Rectangular Microstrip Antenna (RMSA)

Co-axial feed

Side

Viewr

Ground plane

h

Top

View

L

W X

Y

x

Microwave Integrated Circuits (MIC) vs MSA

Parameters MIC MSA

Dielectric

Constant (εr)

Large Small

Thickness (h) Small Large

Width (W) Generally Small

(impedance dependent)

Generally Large

Radiation Minimum (small fringing

fields)

Maximum (large

fringing fields)

Examples Filters, power dividers,

couplers, amplifiers, etc.

Antennas

Substrates for MSA

Substrate Dielectric

Constant (εr)

Loss tangent

(tanδ)

Cost

Alumina 9.8 0.001 Very

High

Glass Epoxy 4.4 0.02 Low

Duroid /

Arlon

2.2 0.0009 Very

High

Foam 1.05 0.0001 Low/

Medium

Air 1 0 NA

Advantages

Light weight, low volume, low profile, planar

configuration, which can be made conformal

Low fabrication cost and ease of mass production

Linear and circular polarizations are possible

Dual frequency antennas can be easily realized

Feed lines and matching network can be easily

integrated with antenna structure

Disadvantages

Narrow bandwidth (1 to 5%)

Low power handling capacity

Practical limitation on Gain (around 30 dB)

Poor isolation between the feed and

radiating elements

Excitation of surface waves

Tolerance problem requires good quality

substrate, which are expensive

Polarization purity is difficult to achieve

Size is large at lower frequency

Applications

Pagers and mobile phones

Doppler and other radars

Satellite communication

Radio altimeter

Command guidance and telemetry in

missiles

Feed elements in complex antennas

Satellite navigation receiver

Biomedical radiator

Various Microstrip Antenna Shapes

MSA Feeding Techniques

Coaxial Feed

Microstrip Line Feed

Microstrip Feed (contd.)

Electromagnetically Coupled Feed

Aperture Coupled Feed

RMSA: Resonance Frequency

where m and n are orthogonal modes of excitation. Fundamental mode is TM10 mode, where m =1 and n = 0.

L

Le

W We

~

x

RMSA – Characterization

RMSA: Design Equations

Smaller or larger W can be taken than

the W obtained from this expression.

BW α W and Gain α W

Choose feed-point x between L/6 to L/4.

RMSA: Design Example

Design a RMSA for Wi-Fi application (2.400 to 2.483 GHz)

Chose Substrate: εr = 2.32, h = 0.16 cm and tan δ = 0.001

= 3 x 1010 / ( 2 x 2.4415 x 109 x √1.66)

= 4.77 cm. W = 4.7 cm is taken

= 2.23

Le = 3 x 1010 / ( 2 x 2.4415 x 109 x √2.23) cm

= 4.11 cm

L = Le – 2 ∆L = 4.11 – 2 x 0.16 / √2.23 = 3.9 cm

RMSA: Design Example – Simulation using IE3D

L = 3.9 cm, W = 4.7 cm, x = 0.7 cm

εr = 2.32, h = 0.16 cm and tan δ = 0.001

Zin = 54Ω at f = 2.414 GHzBW for |S11| < -10 dB is from

2.395 to 2.435 GHz = 40 MHz

Designed f = 2.4415 and Simulated f = 2.414 GHz

% error = 1.1%. Also, BW is small.

SOLUTION: Increase h and reduce L

L = 3 cm and W = 4 cm

Substrate parameters: εr = 2.55, h = 0.159 cm, and tan δ = 0.001

Probe diameter = 0.12 cm for SMA connector.

RMSA is analyzed using commercially available IE3D software.

Effect of Various Parameters on Performance of RMSA

L

Le

W We

x

Effect of Feed Point Location (x)

For Infinite Ground Plane

With increase in x, input impedance plot shifts right

towards higher impedance values.

Effect of Width (W)

With increase in W, aperture area, εe and fringing fields increase, hence frequency

decreases and input impedance plot shifts towards lower impedance values.

BW α W and Gain α W

Effect of Thickness (h)

However, to reduce surface waves

As h increases, fringing fields and probe inductance increase,

frequency decreases and input impedance plot shifts upward.

BW α h/λ0

Flat Reflector Antennas

CornerPlane

Curved Reflector Antennas

Prime Focus Reflector Cassegrain Reflector

Vertical Dipole Antenna over Infinite Perfect Ground Plane (Reflector)

Directivity and Radiation Resistance of Vertical Dipole Antenna over Infinite Reflector

Directivity and radiation resistance of a vertical

infinitesimal dipole as a function of its height

above an infinite perfect electric conductor

Radiation Pattern of Vertical Dipole Antenna over Infinite Ground Plane (Reflector)

Elevation patterns of a vertical infinitesimal dipole for

different heights above an infinite perfect electric conductor

Horizontal Dipole Antenna over Infinite Ground Plane (Reflector)

Directivity and Radiation Resistance of Horizontal Dipole Antenna over Infinite Reflector

Directivity

Radiation Resistance

Radiation resistance and directivity of a horizontal

infinitesimal electric dipole as a function of its height

above an infinite perfect electric conductor

Radiation Pattern of Horizontal Dipole Antenna over Infinite Ground Plane (Reflector)

Elevation patterns of a horizontal infinitesimal dipole for

different heights above an infinite perfect electric conductor

Corner Reflector Antenna

Top View of Corner

Reflector Antenna

Wave incident at 900 Corner

Reflector reflects back in the

same direction

Corner Reflector Antenna

Prospective View Wire Grid Arrangement

Images for Corner Reflector Antennas

3 Images for 900 Corner

Reflector Antenna 5 Images for 600 Corner

Reflector Antenna

Images for Corner Reflector Antennas

7 Images for 450 Corner

Reflector Antenna11 Images for 300 Corner

Reflector Antenna

No. of Images = 360/α - 1

90° Corner Reflector Antenna

1 1 2 2 3 3 4 4, , , , , , , , , ,E r E r E r E r E r

Total field will be sum of contributions

from the feed and its images.

Array Factor for 90° Corner Reflector Antenna

Array factor of the 90° Corner Reflector Antenna:

In the Azimuthal Plane, ( = /2)

0

, 2 cos sin cos cos sin sinE

AF ks ksE

0

/ 2, 2 cos cos cos sinE

AF ks ksE

Radiation Pattern of 900 Corner Reflector Antenna

For s > 0.7λ, main

beam splits.

For s = λ, null in

the broadside

direction.

Array Factor of Corner Reflector Antenna for other α

= 60

, 4sin cos cos 32 2 2

oFor

X X YAF

= 45

, 2 cos( ) cos( ) 2cos cos2 2

oFor

X YAF X Y

= 30

3 3, 2 cos( ) 2cos cos cos( ) 2cos cos

2 2 2 2

oFor

Y XAF X X Y Y

sin cosX ks sin sinY ks where

S-Limit for Corner Reflector Antennas

S < 0.7λ α = 900

There is Limit on S-value for

single lobe in the radiation pattern.

Parabolic Reflector Antenna

For Parabola:

OP + PQ = constant = 2f

OP = r’ and PQ = r’cos’

So, r’ (1+ cos’) =2f

Parabolic Reflector Antenna Equations

1 1

0 2 2

1

22tan tan1

16 16

fd

d

d ff

f d

f/d 0.4 0.5 0.6 0.7 0.8 1.0

θ0 64.0 53.1 45.2 39.3 34.7 28.1

Gain and Aperture Efficiency of Parabolic Reflector Antenna

𝐒𝐩𝐢𝐥𝐥𝐨𝐯𝐞𝐫 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒔): fraction of the total power that

is radiated by the feed, intercepted, and collimated by the

reflecting surface.

𝐓𝐚𝐩𝐞𝐫 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒕) :uniformity of the amplitude

distribution of the feed pattern over the surface of the reflector.

𝐏𝐡𝐚𝐬𝐞 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒑): phase uniformity of the field over

the aperture plane.

𝐏𝐨𝐥𝐚𝐫𝐢𝐬𝐚𝐭𝐢𝐨𝐧 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒙) : polarization uniformity of

the field over the aperture plane

𝐁𝐥𝐨𝐜𝐤𝐚𝐠𝐞 𝐞𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲 (∈𝒃)

𝑹𝒂𝒏𝒅𝒐𝒎 𝑬𝒓𝒓𝒐𝒓 𝑬𝒇𝒇𝒊𝒄𝒊𝒆𝒏𝒄𝒚 (∈𝒓)

Effect of Feed Pattern on Efficiency

Spillover and Taper Efficiencies of Parabolic Reflector Antenna

Reflector Aperture Angle, θ0

Spillover Efficiency

Taper Efficiency

Reflector Aperture Angle, θ0 (in degrees)

Aperture Efficiency of Parabolic Reflector Antenna

Reflector Aperture Angle, θ0 (in degrees)

Cassegrain Reflector Antenna

Gain of Large Reflector Antennas