compact liquid crystal based tunable band-stop filter...

Research ArticleCompact Liquid Crystal Based Tunable Band-Stop Filter with anUltra-Wide Stopband by Using Wave Interference Technique

Longzhu Cai Huan Xu and Daping Chu

Electrical Engineering Division University of Cambridge Cambridge CB3 0FA UK

Correspondence should be addressed to Daping Chu dpc31camacuk

Received 4 December 2016 Accepted 22 January 2017 Published 19 February 2017

Academic Editor Luciano Tarricone

Copyright copy 2017 Longzhu Cai et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

A wave interference filtering section that consists of three stubs of different lengths each with an individual stopband of its owncentral frequency is reported here for the design of band-stop filters (BSFs) with ultra-wide and sharp stopbands as well as largeattenuation characteristics The superposition of the individual stopbands provides the coverage over an ultra-wide frequencyrange Equations and guidelines are presented for the application of a new wave interference technique to adjust the rejectionlevel and width of its stopband Based on that an electrically tunable ultra-wide stopband BSF using a liquid crystal (LC) materialfor ultra-wideband (UWB) applications is designed Careful treatment of the bent stubs including impedance matching of themain microstrip line and bent stubs together with that of the SMA connectors and impedance adaptors was carried out for thecompactness and minimum insertion and reflection losses The experimental results of the fabricated device agree very well withthat of the simulationThe centre rejection frequency asmeasured can be tuned between 4434 and 4814GHzwhen a biased voltageof 0ndash20Vrms is used The 3 dB and 25 dB stopband bandwidths were 486GHz and 251 GHz respectively which are larger thanthat of other recently reported LC based tunable BSFs

1 Introduction

Band-stop filters (BSFs) with wide stopbands and compactstructures are desirable in wireless communications becauseof their ability to suppress unwanted wideband noise andspurious signals [1] In early 2002 the USA Federal Com-munications Commission (FCC) released the unlicensedfrequency spectrum of ultra-wideband (UWB) 31ndash106GHzfor commercial use which has led to the further developmentof wide stopband BSFs [2] According to the FCCrsquos proposalany bandwidth wider than 500MHz or 20 relative to thecentre frequency is considered to be UWB [3] Due toincreasing levels of complexity and demands for advancedcommunication systems UWB technology has drawn moreand more attention [4 5] The advantages of this technol-ogy consist of high resolution for ranging and geolocationand good resistance to small scale fading and narrowbandinterference [3 6 7] Potential uses for UWB technologyincludemedical imaging systems and vehicular radar systems[3 6 7] Regulations regarding UWB standards vary across

the world For instance in 2006 UWB transmission in Japanwas allowed within the 31ndash48 and 6ndash10GHz bands [3]

Some frequency bands such asWorldwide interoperabil-ity forMicrowave Access (WiMAX) with the frequency range33ndash36GHz andWireless Local Area Network (WLAN) withthe frequency spectra 515ndash535GHz and 5725ndash5825GHzare allocated within the designated UWB range which canlead to interference when multiple UWB systems operatesimultaneously within these bands [8] To solve the issueof interference in the UWB frequency range many typesof BSFs have been proposed over the years with variousconfigurations [2 9ndash12] However the reported BSFs usuallyhave relatively complicated structures large dimensions andlimited stopbandbandwidths and attenuationsWhat ismorethese filters are not reconfigurable Liquid crystals (LCs) havebeen studied intensively as tunable dielectric materials incombination with microwave (MW) technology for manyMWapplicationsThis is owing to their ability for continuoustuning large tuning range relatively low dielectric loss inhigh frequencies and cost effective fabrication process [13]

HindawiInternational Journal of Antennas and PropagationVolume 2017 Article ID 9670965 11 pageshttpsdoiorg10115520179670965

2 International Journal of Antennas and Propagation

Liquid crystal

SMA

Impedance adaptor

Etched ground

SMA

Aluminium ground

Rogers 4003CLiquid Crystal

Top view

Side view

y

x

W1

W2

S1

S2

S3

B1

B2

B3

L2

L1

Figure 1 Schematic diagram of the proposed LC based tunable wideband BSF

In this work we demonstrate here an LC based tunableBSF with an inverted microstrip line (ML) structure andan ultra-wide and sharp stopband with large attenuationThe conventional and well-known open stub structureswere widely used in filters to achieve frequency rejectionbehaviours [14 15] with either open stubs of equal lengthor additional spurline structures between the stubs for awider rejection bandwidth and a high rejection ratio but withlimited effects In the past we presented an LC based tunablewideband BSF with double stubs of the same length as well[16] Here our proposed new LC based tunable wideband BSFis based on a new substrate configuration and a modifiedbent stub structure with different stub lengths which ismore effective to attain a wider rejection bandwidth and ahigh rejection ratio without increasing the devicersquos footprintIn this design we applied a new wave interference tech-nique instead of the traditional lumped equivalent circuitanalysis to optimize the filter performance with equationsand guidelines for the adjustment of the rejection level andwidth of its stopband SMA connectors are included in oursimulationMeasured results from the fabricated device agreewell with the simulated ones and they exhibit a continuallytuned rejection band with a centre frequency that can beadjusted between 4434 and 4814GHz The measured 3 dBand 25 dB bandwidths of the device are as high as 486GHzand 251 GHz respectively Furthermore the attenuations inWiMAX andWLAN band ranges are both ltminus25 dB2 Design of the Liquid Crystal Based

Band-Stop Filter

The configuration of the proposed LC based BSF is shownin Figure 1 A layer of LC material is sandwiched betweenan aluminium ground plate and 1524mm thick PCB-Rogers4003C with relative permittivity 120576119903 = 355 and dielectric loss

tan 120575 = 00027 The ML structure of the BSF is coated on thebottom of the Rogers 4003C to a thickness of 0017mm Thethickness of the LC layer is 0113mm which is smaller thanthat of SMA connectors To allow the SMA connectors to beinserted without touching the ground plate two ends of theground plate are shaped to leave a gap of 063mm In thisconfiguration MW propagating into and out of the deviceexperience a discontinued medium between air and the LCmaterial which causes impedance mismatching To reducethe reflection two impedance adaptors with width 1198822 =25mm are designed at the two ends as shown in Figure 1ThemainML and bent stubs have equal widths1198821 which arecarefully designed to ensure that the characteristic impedanceof the whole device including the impedance adaptors andSMA connectors thoroughly matches for minimising thedevice reflection and insertion loss [17 18] Alignment layermade of polyimide mixture nylon with 02 concentrationwas coated on the Rogers and ground surfaces that are incontact with the LC material After the curing process toevaporate the solvent in the polyimide mixture the surfaceswith the polyimide mixture are rubbed by a velvet cloth inorder to align the LC molecules in a fixed direction

The dimensions of the central ML structure shown inFigure 1 are as follows1198821 = 0254mm 1198781 = 1198611 = 385mm1198782 = 1198612 = 473mm 1198783 = 1198613 = 6mm 1198711 = 86mmand 1198712 = 1025mm These dimensions have been adjustedand optimized by using a new wave interference technique toreject the WiMAX and WLAN bands at a high attenuationlevel during stopband tuning In the following sections thewave interference technique and device design procedure arepresented in detail

21 Liquid Crystal Used for the Band-Stop Filter LCmaterialsare known to be an optically and electrically anisotropicmedium The mechanism of nematic LC used as the tunable

International Journal of Antennas and Propagation 3

perp

(a)

Rogers 4003CML

Alignment layer

Aluminium ground

LC layerV＜ＣＭ

V＜ＣＭ = 0

(b)

V＜ＣＭ

0 lt V＜ＣＭ lt VＭＮ

(c)

V＜ＣＭ

V＜ＣＭ = VＭＮ

(d)

Figure 2 (a) Single LCmolecule and states of LCmolecules under various biased voltages (b)119881bias = 0 (c) 0 lt 119881bias lt 119881sat and (d)119881bias = 119881sat

Table 1 Dielectric properties of the chosen LCmaterial at 1ndash10GHzand 23∘C

LC material 120576perp 120576 tan 120575perp tan 120575GT3-24002 25 33 00123 00032

dielectric material in MW devices is that the orientationof the rod-like nematic LC molecules can be reoriented byeither an electric or a magnetic field resulting in a changeof the effective permittivity in the MW propagation pathwhich thus alters the device characteristic properties Variousmolecular orientation states are illustrated in Figure 2 whenLC molecules are subjected to different biased voltages

The chosen nematic LC was GT3-24002 from Mercksynthesized with a wide nematic phase temperature rangeand with a clearing temperature of sim173∘C which makes thisLC material suitable for many practical purposes [19] Theproperties of GT3-24002 at 1ndash10GHz and 23∘C are listed inTable 1

22Wave Interference Techniques andDesign of the Band-StopFilter The filter structure shown in Figure 1 comprises threebent stubs and two offset lines (1198711 and1198712) In order to achievea large attenuation as well as a sharp and wide stopband ina frequency range covering the WiMAX band and WLANband the physical length of each element must be carefullyadjusted A simple explanation of the complicated waveinterference behaviour of the structure shown in Figure 1starts from simpler structure with one stub as shown inFigure 3(a) For this structure a portion of MW is reflectedfrom the stub to a traveling distance of 21198781 at the intersectionof the main transmission path and the stub Destructive waveinterference is expected if theMW fulfils the condition statedin (1) The stopband centre frequency for mode 119899 can becalculated according to (2) and (3)

Δ119878 = 21198781 = 119899 times 120582119892 + 12120582119892 (119899 = 0 1 2 ) (1)

120582119892 = 119888119891 times radic120576eff (2)

119891 = (119899 + 12)119888

21198781 times radic120576eff (3)

where 120582119892 is the guided wavelength at the stopband centrefrequency119891 and 120576eff is the effective relative permittivity whenMW propagates throughout the structure In (1) (12)120582119892represents a 180∘ MW phase difference (antiphase) Thelength 1198781 = (14)120582119892 for 119899 = 0 called the quarter-wavelengthopen stub determines the required centre frequency of thefundamental stopband Equation (3) indicates that stopbandfrequency 119891 is a function of both 1198781 and 120576eff For a fixedstub length 1198781 119891 can be adjusted by tuning the effectivepermittivity of the LC material using a biased voltage

Figure 3(b) is a conventional spurline structure whichhas been used to realize LC based BSFs recently [20 21]With the same substrate and dimensions for the structures inFigures 3(a) and 3(b) the simulated transmission character-istics are shown in Figure 3(c) where we can see that the stubstructure of Figure 3(a) has a wider stopband bandwidth anda larger attenuation at the rejection frequencyThe simulationtool used in this work is High Frequency Structural Simulator(HFSS) from Ansys The stronger coupling between theresonator of length 1198781 and its parallel transmission line resultsin a narrower stopband bandwidth for the spurline structureThe larger attenuation for the stub structure comes from thesamewidth of the stub and themain transmission lineThere-fore using the prototype in Figure 3(a) is more advantageousto design wide stopband and large attenuation BSFs

A new wave interference technique is used to explore theeffects of the stub and offset lengths for BSFs that consistof several stubs and can also estimate the transmissionproperties of each structure by using this qualitative analysisOnly one stopband centre frequency can be achieved for thedouble-stub structure shown in Figure 4(a) assuming thatthe two stub lengths are equal (1198781 = 1198782) The rejectionlevel |11987821| at the stopband centre frequency is governed bythe offset transmission line length 1198711 which is shown inFigure 4(b) By comparing the rejection levels for the one-stub structure and the double-stub structure with offsetlength 1198711 = 0 it can be shown that the double-stub structurecan further reduce the rejection level by sim5 dB due to thedoubled destructive wave interference However a betterattenuation at the centre frequency can be obtained if 1198711 isaround (14)120582119892 or (34)120582119892 as the consequence of anotherdestructive wave interference occurring along the offsettransmission line 1198711 This is further confirmed by the lowelectric field distribution along the structure for 1198711 = (14)120582119892


1 2

s1

w1

w2

(a)

1 2G1

s1

w1

w2

(b)

0

minus5

minus10

minus15

minus20

minus25

minus30

S21

(dB)

Frequency (GHz)

Stub structureSpurline structure

654321

(c)

Figure 3 (a) One-stub structure (b) spurline structure and (c) their transmission properties for 1199081 = 1199082 = 0276mm and 1198661 = 005mm

and 1198711 = (34)120582119892 as indicated in Figures 4(c) and 4(e)respectively

Two valleys in a stopband are expected when 1198781 = 1198782each independently determined by the associated stub lengththat is described as 1198781 = 12058211989214 and 1198782 = 12058211989224 Figure 5(a)shows the transmission |11987821| for the double-stub structurewith different stub lengths which clearly shows two valleysIn order to create a strong destructive wave interferencebetween the two valleys the offset length1198711 should be around12058211989214 and 12058211989224 This is true if the two valleys are closeenough for example as shown in Figure 5(b) The red linerepresents the insertion loss |11987821| in such a condition (1198781 =95mm 1198782 = 105mm and 1198711 = 105mm) which achievesattenuation greater than minus40 dB However the drawback ofsuch a design is its narrow stopband width

If the two stub lengths differ considerably then the twovalleys are separated by a few GHz As a result of waveinterference of the individual stopbands an undesirable over-shoot appears between the two valleys that greatly reducesthe attenuation The double-stub structure is therefore notsuitable for use as a BSF of large attenuation and widestopband To solve the problem a third stub with a differentlength is added to the structure which is expected to create a

main stopband located between the two valleys that providesa strong attenuation as well as a sharp and wide stopband

In order to minimise the interference from the popularlyused WiMAX and WLAN bands in UWB applications thelengths of two stubs can be roughly determined to producetransmission valleys at a minimum and amaximum frequen-cies with the third stub of a length between that of thesetwo stubs placed in the middle to produce a main stopbandbetween the two valleys Subsequently based on the analysisof various offset length effects the distances between thesestubs are optimized to avoid undesirable overshoots Thethree stubs are bent for compactness and all the dimensionsof the filter are carefully optimized and adjusted in the HFSSin order to obtain good characteristics such as minimuminsertion and reflection losses a strong attenuation anda sharp and wide stopband The proposed bent three-stubstructure was shown in Figure 1 and the final dimensionsas optimized are reported in Section 2 Figure 6 shows thesimulated scattering parameters (S-parameters) |11987821| and|11987811| of the proposed BSF with SMA connectors includedTo illustrate the properties of device transmission Figure 7shows the MW electric field distributions (including theSMA connection interface) at the untuned LC state (biased


S1

S2

L1

(a)

minus30

minus40

minus50

minus60

minus70

S21

at ce

ntre

freq

uenc

y (d

B)

100806040200

1-stub structure2-stub structure

Offset length L1 (g)

(b)

L1 =g

4

23518e + 00511229e + 00553614e + 00425598e + 00412222e + 00458356e + 00327863e + 00313303e + 00363517e + 00230327e + 00214480e + 00269135e + 00133009e + 00115761e + 00175250e + 000

EFi

eld

(V_p

er_m

)

(c)

L1 =g

2


EFi

eld

(V_p

er_m

)

(d)

L1 =3g

4


EFi

eld

(V_p

er_m

)

(e)Figure 4 (a) Double-stub structure and (b) its transmission (|11987821|) for 1198781 = 1198782 at the centre frequency with respect to offset length 1198711 andthe electric field distribution when the offset lengths 1198711 are (c) (14)120582119892 (d) (12)120582119892 and (e) (34)120582119892

voltage = 0Vrms) for two passbands (2GHz and 8GHz)and one stopband (4757GHz) The color difference associ-ated with the electric field strength clearly demonstrates aneffective performance of the proposed BSF in rejecting theintended frequencies

Figure 6 shows that the transmission |11987821| has quite asharp slope The 3 dB and 25 dB bandwidths are as high as473GHz and 254GHz respectively in the untuned LC stateThe fractional bandwidth (FBW) is defined as [23]

FBW = bandwidthcentre frequency

= 1198912 minus 1198911(1198912 + 1198911) 2 (4)

where 1198912 and 1198911 are the upper and lower frequencies inthe stopband respectively Hence the 3 dB and 25 dB FBWare 968 and 526 respectively In addition the stopbandcentre frequency can be continuously tuned between 4337and 4757GHz with 97 tunability relative to the centrefrequency in the fully biased state Moreover during the tun-ing process the rejection level of transmission |11987821| remainsbelow minus50 dB Using such a BSF frequency bands where waveinterference may occur in UWB communications such asthe WiMAX and WLAN bands will be effectively rejectedto a level lower than minus30 dB This makes the proposed BSFparticularly useful for UWB applications


0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

Tran

smiss

ion S

21

(dB)

Frequency (GHz)765432

S1 = 95 mm S2 = 105 mmS1 = 95 mm S2 = 11 mmS1 = 95 mm S2 = 115 mmS1 = 95 mm S2 = 125 mm

(a)

0

minus10

minus20

minus30

minus40

Tran

smiss

ion S

21

(dB)

Frequency (GHz)6 842

minus50

minus60

S1 = 95mm S2 = 105mm L1 = 1mmS1 = 95mm S2 = 105mm L1 = 105mmS1 = 95mm S2 = 105mm L1 = 19mm

(b)

Figure 5 Transmission |11987821| properties of the double-stub structure with (a) various stub length 1198782 and (b) various offset length 1198711


0

minus10

minus20

minus30

minus40

minus50

minus60

S-pa

ram

eter

s (dB

)

SimulatedSimulated

SimulatedSimulated

0Vrms S2120Vrms S21

0Vrms S1120Vrms S11

Figure 6 Simulated S-parameters of the proposed filter when the substrate LC is tuned

3 Experimental Results and Discussions

The designed BSF was fabricated at a compact size of 34mm(L) by 22mm (W) weighing 2311 g These parameters areshown in Figure 8

Thedevicewasmeasured using a two-port vector networkanalyser (VNA) Agilent 8722ET The measured transmission|11987821| under various driven voltages is displayed in Figure 9(a)At zero biased voltage the centre rejection frequency of the

fabricatedBSF is 4814GHz and the LC layer exhibits the low-est dielectric permittivity 120576perp As the biased voltage increasesthe LC layer permittivity increases as well which resultsin a decrease of the device rejection frequency The lowestrejection frequency reaches 4434GHz when a biased voltageof 20Vrms is used and the LC layer permittivity has a valueof around 120576 The total tuned frequency range is 038GHzcorresponding to a tunability of 86 relative to the centrefrequency at a biased voltage of 20VrmsThis is fairly close to


E Field (V_per_m)

f = 2 GHz

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(a)

f = 4757 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(b)

f = 8 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(c)

Figure 7 Electric field distributions of the proposed filter in the untuned state at its (a) passband 2GHz (b) stopband 4757GHz and (c)passband 8GHz

(a) (b) (c)

Figure 8 (a) The length (b) width and (c) weight of the fabricated BSF

the targeted value of 97 tunability identified in simulationThe tuned frequencies with respect to the applied voltage areshown in Figure 9(b) The voltage range for the tuned fre-quency 8ndash85 is sim6Vrms from 4Vrms to 10Vrms Basedon the experimental results the rejection level of the deviceis as low as simminus45 dB during tuning of the LC In addition

a wide range of undesired signals is expected to be rejectedwhen the device is implemented in UWB systems When thedevice is electrically controlled some undesired frequencybands such asWiMAX (33ndash36GHz) andWLAN (515ndash535and 5725ndash5825GHz) that could cause signal interference inUWB communications are suppressed to below minus25 dB


0

minus10

minus20

minus30

minus40

minus50

S21

( dB)


0Vrms4Vrms6Vrms

8Vrms12 Vrms20Vrms

(a)

85

8

400

300

200

100

0

Tune

d fre

quen

cies

(MH

z)

LC driven voltage (Vrms)201612840

(b)

Figure 9 Measured results of (a) transmission |11987821| and (b) tuned frequencies with respect to LC driven voltage

Table 2 Comparison between the simulation and measurement results of the proposed BSF

Parameters Simulated results Measured resultsFrequency (nonbiasedbiased) 47574337GHz 48144434GHzTuned frequency rangetunability 042GHz97 038GHz86Transmission |11987821| (nonbiasedbiased) minus536minus587 dB minus442minus458 dB3 dB bandwidthFBW 473GHz968 486GHz96225 dB bandwidthFBW 254GHz526 251 GHz512

To further verify the design quality of the fabricateddevice both the simulation and measurement results arecompared in Figure 10 In Figure 10(a) the curves for 0Vrmsand 20Vrms in the simulation correspond to 1205761015840 = 120576perp and1205761015840 = 120576 of the LC material respectively The figure showsthat there is a close agreement between the simulation andmeasurement of the device in terms of the trend of S-parameters though some slight discrepancies remain Onenoticeable discrepancy in Figure 10(a) is that there is asmall shift between the simulated and measured stopbandfrequencies when the filter is tuned by a biased voltage of20Vrms This could be due to an error in measurementof the relative permittivity of the LC material It might bealso because a biased voltage of 20Vrms is not sufficientlyhigh to drive such a thick LC layer (0113mm) to reach thehomeotropic orientation state (120576) though the S-parametersof the device are almost unchanged when the biased voltagevaries from 15 to 20Vrms The left plot of Figure 10(a) showsthat at 0Vrms the measured stopband centre frequencyclosely matches that of the simulated results which furthersupports this assumption Nevertheless the measured tuningfrequency range (038GHz) already reaches 905 of thetargeted value (042GHz) at 20Vrms Figure 10(b) also shows

a good consistency between the measurement and simula-tion being the results for the empty device using air as amedium before LC injection This indicates the accuracy ofthe model In addition to the accuracy of the simulationother potential reasons for deviation between the simulationand measurement include radiation loss due to the lack ofmetal shielding during measurement the existence of LCalignment layer and LC thickness variation resulting fromthe fabrication process Table 2 shows a comparison of theperformance between the simulation and measurement ofthe proposed LC based BSF Table 3 shows a comparisonbetween this work and other LC based tunable BSFs recentlyreported for C-band and S-band applications The 3 dB and25 dB bandwidths of this work remain the largest Thoughthe dielectric anisotropy Δ120576 of the LC used in this work withΔ120576 = 08 is not as large as that used in [22] with Δ120576 = 14 itstunability is still reasonably high

4 Conclusions

Aiming for UWB applications a compact tunable BSFwith an ultra-wide and sharp stopband as well as a largeattenuation characteristic has been developed The proposed


0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)



0Vrms simulated S210Vrms measured S21




(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)

Simulated S21Measured S21


0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)

Figure 10 Comparison between the simulation and measurement results of the proposed BSF (a) LC as the substrate and (b) air as thesubstrate (before LC injection)

Table 3 Comparison with recently reported LC based tunable BSFs

Parameter Ref[16] [20] [21] [22] This work

Dielectric anisotropy Δ120576 037307 NA NA 14 081198910 (GHz) at 120576119903 3845 445 34 2225 4434Tunable range (GHz) 029 04 035 0275 038Tunability () 73 86 98 116 863 dB bandwidth (GHz) 3135 115 125 15 4863 dB FBW () 815 258 368 674 96225 dB bandwidth (GHz) sim1 0 0 sim07 251Rejection level (dB) ltminus41 ltminus25 ltminus20 ltminus60 ltminus45


filter topology uses a wave interference filtering section thatconsists of three stubs of different lengths each with anindividual stopband of its own central frequency Equationsand guidelines to apply the new wave interference techniqueto adjust the rejection level and width of its stopband aredescribed Careful treatment of the main ML and bent stubswas carried out for compactness as well as minimising thedevice reflection and insertion loss The measured resultsof the designed filter show a good agreement with thatof the simulation The centre frequency of the superposedstopband of this filter in measurement can be tuned over alarge frequency range between 4434 and 4814GHz nearly10 of the central frequency due to the use of a tunabledielectric medium-LC The reported BSF possesses otherunique features such as an ultra-wide and sharp stopbandefficient noise attenuation (simminus45 dB) and a compact sizeideal for being integrated into various monolithic microwaveintegrated circuits (MMIC) The good performance of thedesigned BSF makes it potentially useful in UWB andtargeted communication systems including those in extremeand hazardous conditions with special measures such as slowblackening treatments [24] for protections

Competing Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank the UK Engineering andPhysical Sciences Research Council (EPSRC) for the supportthrough the Platform Grant for Liquid Crystal Photonics(EPF00897X1) Longzhu Cai thanks Chinese ScholarshipCouncil and Cambridge Commonwealth European andInternational Trust for financial support

References

[1] W J Feng W Q Che S Y Shi and Q Xue ldquoCompactdual-wideband bandstop filters based on open-coupled linesand transversal signal-interaction conceptsrdquo IET MicrowavesAntennas and Propagation vol 7 no 2 pp 92ndash97 2013

[2] B Shrestha and N-Y Kim ldquoMicrostrip wideband bandstopfilter with open stubs for UWB applicationsrdquo Microwave andOptical Technology Letters vol 57 no 4 pp 1003ndash1006 2015

[3] A Svensson A Nallanathan and A Tewfik ldquoUltra-widebandcommunication systems technology and applicationsrdquo EurasipJournal onWireless Communications and Networking vol 2006Article ID 16497 2007

[4] M Mokhtaari and J Bornemann ldquoMicrostrip Ultra-widebandfilter with flexible notch characteristicsrdquo Wireless Engineeringand Technology vol 3 no 1 pp 12ndash17 2012

[5] J Wells ldquoMM-waves in the living room the future of wirelesshigh definition multimediardquo Microwave Journal vol 52 no 8pp 72ndash84 2009

[6] B Allen A Brown K Schwieger et al ldquoUltra wideband appli-cations technology and future perspectivesrdquo in Proceedings of

the International Workshop on Convergent Technologies (IWCTrsquo05) pp 1ndash6 Oulu Finland June 2005

[7] T K K Tsang and M N El-Gamal ldquoUltra-wideband (UWB)communications systems an overviewrdquo in Proceedings of the 3rdInternational IEEE Northeast Workshop on Circuits and SystemsConference (NEWCAS rsquo05) pp 381ndash386 Quebec Canada June2005

[8] F Zhu S Gao J Z Li and J D Xu ldquoPlanar asymmetricalultra-wideband antenna with improved multiple band-notchedcharacteristicsrdquo Electronics Letters vol 48 no 11 pp 615ndash6172012

[9] Z-P Li T Su and C-H Liang ldquoCompact widebandmicrostripbandpass filter with wide upper stopband based on coupled-stub loaded resonatorrdquo International Journal of RF andMicrowave Computer-Aided Engineering vol 25 no 2 pp 122ndash128 2015

[10] R K Mahajan B Shrestha and N-Y Kim ldquoMicrostripsymmetrical twin-spiral inductor resonator filter for UWBapplicationsrdquo Arabian Journal for Science and Engineering vol38 no 9 pp 2465ndash2472 2013

[11] M K Mandal K Divyabramham and V K Velidi ldquoCompactwideband bandstop filter with five transmission zerosrdquo IEEEMicrowave and Wireless Components Letters vol 22 no 1 pp4ndash6 2012

[12] M A Sanchez-Soriano G Torregrosa-Penalva and E Bron-chalo ldquoCompact wideband bandstop filter with four transmis-sion zerosrdquo IEEE Microwave and Wireless Components Lettersvol 20 no 6 pp 313ndash315 2010

[13] P Yaghmaee O H Karabey B Bates C Fumeaux and RJakoby ldquoElectrically tuned microwave devices using liquidcrystal technologyrdquo International Journal of Antennas andPropagation vol 2013 Article ID 824214 9 pages 2013

[14] S Yang ldquoSimulation of a bandstop filter with two open stubsand asymmetrical double spurlinesrdquo International Journal ofAdvanced Research in Electrical Electronics and InstrumentationEngineering vol 3 no 9 pp 11697ndash11701 2014

[15] W-H Tu and K Chang ldquoCompact microstrip bandstop filterusing open stub and spurlinerdquo IEEE Microwave and WirelessComponents Letters vol 15 no 4 pp 268ndash270 2005

[16] L Cai H Xu M Pivnenko and D Chu ldquoA tunable widebandmicrostrip bandstop filter based on liquid crystal materialsrdquo inProceedings of the IEEE International Conference on Communi-cation Problem-Solving (ICCP rsquo14) pp 656ndash657 December 2014

[17] L Cai H Xu J Li and D Chu ldquoHigh figure-of-merit compactphase shifters based on liquid crystal material for 1ndash10GHzapplicationsrdquo Japanese Journal of Applied Physics vol 56 no 1Article ID 011701 2017

[18] L Cai H Xu J Li and D Chu ldquoHigh FoM liquid crystalbased microstrip phase shifter for phased array antennasrdquo inProceedings of the International Symposium on Antennas andPropagation Okinawa Japan October 2016

[19] O H Karabey ldquoLiquid crystal material for microwave applica-tionsrdquo in Electronic Beam Steering and Polarization Agile PlanarAntennas in Liquid Crystal Technology pp 9ndash25 SpringerInternational Cham Switzerland 2014

[20] V Urruchi C Marcos J Torrecilla J M Sanchez-Pena andK Garbat ldquoNote tunable notch filter based on liquid crystaltechnology for microwave applicationsrdquo Review of ScientificInstruments vol 84 no 2 Article ID 026102 2013

[21] J Torrecilla E Avila-Navarro C Marcos et al ldquoMicrowavetunable notch filter based on liquid crystal using spiral spurline


technologyrdquoMicrowave and Optical Technology Letters vol 55no 10 pp 2420ndash2423 2013

[22] J Skulski A Szymanska P Szczepanski R Kisiel and R SRomaniuk ldquoLiquid crystal tunablemicrowave band stop filtersrdquoin Proceedings of the Electron Technology Conference p 89022ERyn Poland July 2013

[23] JD Taylor Introduction toUltra-WidebandRadar Systems CRCPress 1994

[24] F Xing B Zhao and W Shi ldquoStudy on tunable fabrication ofthe ultra-black Ni-P film and its blacking mechanismrdquo Elec-trochimica Acta vol 100 pp 157ndash163 2013

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpswwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



Liquid crystal

SMA

Impedance adaptor

Etched ground

SMA

Aluminium ground

Rogers 4003CLiquid Crystal

Top view

Side view

y

x

W1

W2

S1

S2

S3

B1

B2

B3

L2

L1

Figure 1 Schematic diagram of the proposed LC based tunable wideband BSF

In this work we demonstrate here an LC based tunableBSF with an inverted microstrip line (ML) structure andan ultra-wide and sharp stopband with large attenuationThe conventional and well-known open stub structureswere widely used in filters to achieve frequency rejectionbehaviours [14 15] with either open stubs of equal lengthor additional spurline structures between the stubs for awider rejection bandwidth and a high rejection ratio but withlimited effects In the past we presented an LC based tunablewideband BSF with double stubs of the same length as well[16] Here our proposed new LC based tunable wideband BSFis based on a new substrate configuration and a modifiedbent stub structure with different stub lengths which ismore effective to attain a wider rejection bandwidth and ahigh rejection ratio without increasing the devicersquos footprintIn this design we applied a new wave interference tech-nique instead of the traditional lumped equivalent circuitanalysis to optimize the filter performance with equationsand guidelines for the adjustment of the rejection level andwidth of its stopband SMA connectors are included in oursimulationMeasured results from the fabricated device agreewell with the simulated ones and they exhibit a continuallytuned rejection band with a centre frequency that can beadjusted between 4434 and 4814GHz The measured 3 dBand 25 dB bandwidths of the device are as high as 486GHzand 251 GHz respectively Furthermore the attenuations inWiMAX andWLAN band ranges are both ltminus25 dB2 Design of the Liquid Crystal Based

Band-Stop Filter

The configuration of the proposed LC based BSF is shownin Figure 1 A layer of LC material is sandwiched betweenan aluminium ground plate and 1524mm thick PCB-Rogers4003C with relative permittivity 120576119903 = 355 and dielectric loss

tan 120575 = 00027 The ML structure of the BSF is coated on thebottom of the Rogers 4003C to a thickness of 0017mm Thethickness of the LC layer is 0113mm which is smaller thanthat of SMA connectors To allow the SMA connectors to beinserted without touching the ground plate two ends of theground plate are shaped to leave a gap of 063mm In thisconfiguration MW propagating into and out of the deviceexperience a discontinued medium between air and the LCmaterial which causes impedance mismatching To reducethe reflection two impedance adaptors with width 1198822 =25mm are designed at the two ends as shown in Figure 1ThemainML and bent stubs have equal widths1198821 which arecarefully designed to ensure that the characteristic impedanceof the whole device including the impedance adaptors andSMA connectors thoroughly matches for minimising thedevice reflection and insertion loss [17 18] Alignment layermade of polyimide mixture nylon with 02 concentrationwas coated on the Rogers and ground surfaces that are incontact with the LC material After the curing process toevaporate the solvent in the polyimide mixture the surfaceswith the polyimide mixture are rubbed by a velvet cloth inorder to align the LC molecules in a fixed direction

The dimensions of the central ML structure shown inFigure 1 are as follows1198821 = 0254mm 1198781 = 1198611 = 385mm1198782 = 1198612 = 473mm 1198783 = 1198613 = 6mm 1198711 = 86mmand 1198712 = 1025mm These dimensions have been adjustedand optimized by using a new wave interference technique toreject the WiMAX and WLAN bands at a high attenuationlevel during stopband tuning In the following sections thewave interference technique and device design procedure arepresented in detail

21 Liquid Crystal Used for the Band-Stop Filter LCmaterialsare known to be an optically and electrically anisotropicmedium The mechanism of nematic LC used as the tunable


perp

(a)

Rogers 4003CML

Alignment layer

Aluminium ground

LC layerV＜ＣＭ

V＜ＣＭ = 0

(b)

V＜ＣＭ


(c)

V＜ＣＭ


(d)







Δ119878 = 21198781 = 119899 times 120582119892 + 12120582119892 (119899 = 0 1 2 ) (1)

120582119892 = 119888119891 times radic120576eff (2)

119891 = (119899 + 12)119888

21198781 times radic120576eff (3)





1 2

s1

w1

w2

(a)

1 2G1

s1

w1

w2

(b)

0

minus5

minus10

minus15

minus20

minus25

minus30

S21

(dB)

Frequency (GHz)


654321

(c)








S1

S2

L1

(a)

minus30

minus40

minus50

minus60

minus70

S21

at ce

ntre

freq

uenc

y (d

B)

100806040200



(b)

L1 =g

4


EFi

eld

(V_p

er_m

)

(c)

L1 =g

2


EFi

eld

(V_p

er_m

)

(d)

L1 =3g

4


EFi

eld

(V_p

er_m

)





= 1198912 minus 1198911(1198912 + 1198911) 2 (4)



0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

Tran

smiss

ion S

21

(dB)



(a)

0

minus10

minus20

minus30

minus40

Tran

smiss

ion S

21

(dB)


minus50

minus60


(b)



0

minus10

minus20

minus30

minus40

minus50

minus60

S-pa

ram

eter

s (dB

)

SimulatedSimulated

SimulatedSimulated

0Vrms S2120Vrms S21

0Vrms S1120Vrms S11







E Field (V_per_m)

f = 2 GHz

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(a)

f = 4757 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(b)

f = 8 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(c)


(a) (b) (c)





0

minus10

minus20

minus30

minus40

minus50

S21

( dB)


0Vrms4Vrms6Vrms

8Vrms12 Vrms20Vrms

(a)

85

8

400

300

200

100

0

Tune

d fre

quen

cies

(MH

z)


(b)






4 Conclusions



0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)







(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)



0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)







Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










perp

(a)

Rogers 4003CML

Alignment layer

Aluminium ground

LC layerV＜ＣＭ

V＜ＣＭ = 0

(b)

V＜ＣＭ


(c)

V＜ＣＭ


(d)







Δ119878 = 21198781 = 119899 times 120582119892 + 12120582119892 (119899 = 0 1 2 ) (1)

120582119892 = 119888119891 times radic120576eff (2)

119891 = (119899 + 12)119888

21198781 times radic120576eff (3)





1 2

s1

w1

w2

(a)

1 2G1

s1

w1

w2

(b)

0

minus5

minus10

minus15

minus20

minus25

minus30

S21

(dB)

Frequency (GHz)


654321

(c)








S1

S2

L1

(a)

minus30

minus40

minus50

minus60

minus70

S21

at ce

ntre

freq

uenc

y (d

B)

100806040200



(b)

L1 =g

4


EFi

eld

(V_p

er_m

)

(c)

L1 =g

2


EFi

eld

(V_p

er_m

)

(d)

L1 =3g

4


EFi

eld

(V_p

er_m

)





= 1198912 minus 1198911(1198912 + 1198911) 2 (4)



0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

Tran

smiss

ion S

21

(dB)



(a)

0

minus10

minus20

minus30

minus40

Tran

smiss

ion S

21

(dB)


minus50

minus60


(b)



0

minus10

minus20

minus30

minus40

minus50

minus60

S-pa

ram

eter

s (dB

)

SimulatedSimulated

SimulatedSimulated

0Vrms S2120Vrms S21

0Vrms S1120Vrms S11







E Field (V_per_m)

f = 2 GHz

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(a)

f = 4757 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(b)

f = 8 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(c)


(a) (b) (c)





0

minus10

minus20

minus30

minus40

minus50

S21

( dB)


0Vrms4Vrms6Vrms

8Vrms12 Vrms20Vrms

(a)

85

8

400

300

200

100

0

Tune

d fre

quen

cies

(MH

z)


(b)






4 Conclusions



0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)







(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)



0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)







Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










1 2

s1

w1

w2

(a)

1 2G1

s1

w1

w2

(b)

0

minus5

minus10

minus15

minus20

minus25

minus30

S21

(dB)

Frequency (GHz)


654321

(c)








S1

S2

L1

(a)

minus30

minus40

minus50

minus60

minus70

S21

at ce

ntre

freq

uenc

y (d

B)

100806040200



(b)

L1 =g

4


EFi

eld

(V_p

er_m

)

(c)

L1 =g

2


EFi

eld

(V_p

er_m

)

(d)

L1 =3g

4


EFi

eld

(V_p

er_m

)





= 1198912 minus 1198911(1198912 + 1198911) 2 (4)



0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

Tran

smiss

ion S

21

(dB)



(a)

0

minus10

minus20

minus30

minus40

Tran

smiss

ion S

21

(dB)


minus50

minus60


(b)



0

minus10

minus20

minus30

minus40

minus50

minus60

S-pa

ram

eter

s (dB

)

SimulatedSimulated

SimulatedSimulated

0Vrms S2120Vrms S21

0Vrms S1120Vrms S11







E Field (V_per_m)

f = 2 GHz

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(a)

f = 4757 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(b)

f = 8 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(c)


(a) (b) (c)





0

minus10

minus20

minus30

minus40

minus50

S21

( dB)


0Vrms4Vrms6Vrms

8Vrms12 Vrms20Vrms

(a)

85

8

400

300

200

100

0

Tune

d fre

quen

cies

(MH

z)


(b)






4 Conclusions



0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)







(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)



0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)







Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










S1

S2

L1

(a)

minus30

minus40

minus50

minus60

minus70

S21

at ce

ntre

freq

uenc

y (d

B)

100806040200



(b)

L1 =g

4


EFi

eld

(V_p

er_m

)

(c)

L1 =g

2


EFi

eld

(V_p

er_m

)

(d)

L1 =3g

4


EFi

eld

(V_p

er_m

)





= 1198912 minus 1198911(1198912 + 1198911) 2 (4)



0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

Tran

smiss

ion S

21

(dB)



(a)

0

minus10

minus20

minus30

minus40

Tran

smiss

ion S

21

(dB)


minus50

minus60


(b)



0

minus10

minus20

minus30

minus40

minus50

minus60

S-pa

ram

eter

s (dB

)

SimulatedSimulated

SimulatedSimulated

0Vrms S2120Vrms S21

0Vrms S1120Vrms S11







E Field (V_per_m)

f = 2 GHz

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(a)

f = 4757 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(b)

f = 8 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(c)


(a) (b) (c)





0

minus10

minus20

minus30

minus40

minus50

S21

( dB)


0Vrms4Vrms6Vrms

8Vrms12 Vrms20Vrms

(a)

85

8

400

300

200

100

0

Tune

d fre

quen

cies

(MH

z)


(b)






4 Conclusions



0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)







(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)



0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)







Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

minus5

minus10

minus15

minus20

minus25

minus30

minus35

minus40

Tran

smiss

ion S

21

(dB)



(a)

0

minus10

minus20

minus30

minus40

Tran

smiss

ion S

21

(dB)


minus50

minus60


(b)



0

minus10

minus20

minus30

minus40

minus50

minus60

S-pa

ram

eter

s (dB

)

SimulatedSimulated

SimulatedSimulated

0Vrms S2120Vrms S21

0Vrms S1120Vrms S11







E Field (V_per_m)

f = 2 GHz

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(a)

f = 4757 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(b)

f = 8 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(c)


(a) (b) (c)





0

minus10

minus20

minus30

minus40

minus50

S21

( dB)


0Vrms4Vrms6Vrms

8Vrms12 Vrms20Vrms

(a)

85

8

400

300

200

100

0

Tune

d fre

quen

cies

(MH

z)


(b)






4 Conclusions



0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)







(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)



0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)







Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










E Field (V_per_m)

f = 2 GHz

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(a)

f = 4757 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(b)

f = 8 GHz

E Field (V_per_m)

16591e

+00

5

5524

7e+00

4

183

97e+00

4

6126

2e+00

3

204

00e+00

3

67931e

+00

2

226

21e+00

2

75327

e+00

1

2508

4e+00

1

83528

e+00

0

2781

5e+00

0

92622

eminus00

1

3084

3eminus00

1

102

71e

minus00

1

3420

1eminus00

2

(c)


(a) (b) (c)





0

minus10

minus20

minus30

minus40

minus50

S21

( dB)


0Vrms4Vrms6Vrms

8Vrms12 Vrms20Vrms

(a)

85

8

400

300

200

100

0

Tune

d fre

quen

cies

(MH

z)


(b)






4 Conclusions



0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)







(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)



0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)







Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

minus10

minus20

minus30

minus40

minus50

S21

( dB)


0Vrms4Vrms6Vrms

8Vrms12 Vrms20Vrms

(a)

85

8

400

300

200

100

0

Tune

d fre

quen

cies

(MH

z)


(b)






4 Conclusions



0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)







(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)



0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)







Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)0

minus15

minus30

minus45

minus60

S-pa

ram

eter

s (dB

)







(a)

S-pa

ram

eter

s (dB

)

Frequency (GHz)



0

minus10

minus20

minus30

minus40

minus50

minus6010987654

(b)







Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











Competing Interests


Acknowledgments


References






























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation
















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









compact liquid crystal based tunable band-stop filter...

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