βAntenna Technology For ATSC 3.0 β Boosting the Signal Strengthβ
Continuation
John L. Schadler
4KUHDTV
β’
β’
β’
β’
Outdoor reception of the Bootstrap signal
.25 Mbit Deep indoor mobile to small handheld receiver
48 dBu
95 dBu
Effect of heavy beam tilt Effect of heavy null fill
Addition of SFNs
Most effective way to design for service and provide even distribution of high signal strength β High null fill + SFNs
β’ Saturate in the vicinity of the main antenna by increasing the null fill
β’ Add SFN sites around coverage perimeter to boost the signal strength outside of the high null fill area
+ SFN
β’ ATSC 3.0 MISO scheme β TDCFSβ’ Transmitting two uncorrelated signals to a single receiverβ’ Cost effective
β’ Increase the complexity of the transmitter β not the receiverβ’ ATSC 3.0 SFN sites will serve many receivers
β’ Economical to add equipment cost at the transmit site rather than the receiver
β’ Receiver remains small and affordable
β’ TDCFS can be deployed in either a co-located or distributed configuration
β’ Does not require any new RF equipment within the existing SFN
Co-located Distributed
β’ Diversity gain throughout the coverage area
Diversity gain Boosting the RSSβ‘
Max diversity gain is based on the total number of independent signal paths
M transmit antennas N receive antennas
1 β€ πΊπ β€ πΊπππ₯ = π β π
3 dB improvement in RSS can be achieved when 2 x 1 MISO diversity is applied
β’ Traditionallyβ’ Spatial diversity
β’ Separate antennasβ’ Difficult to implement
β’ Space limitationsβ’ Polarization diversity
β’ Co-located antenna elementsβ’ Orthogonal polarizationsβ’ Modes of operation
β’ Slant linearβ’ RH / LH CP
Which mode of polarization diversity operation is best for ATSC 3.0 MISO?
Dual input broadcast antenna array
X
β’ Max diversity gain depends on spreading the power evenly between the polarizationsβ’ Figure of merit
β’ Cross Polarization Discrimination (XPD)β’ The ratio between the available power in the vertical and horizontal polarizations
πππ· =π π£
2
π β2 For optimal diversity gain XPD=0dB
Compare the static response XPD for slant linear and RH/LH CP
Pair of orthogonal crossed dipoles oriented in space by a tilt angle Ξ±
Dipole modeling Channel modeling
Four channel links between the transmitter and receiver
π βπ π£
=Ξ11π
ππ11 Ξ12πππ12
Ξ21πππ21 Ξ22π
ππ22
πβππ£
πβππ£
=π πππΌ βπππ πΌπππ πΌ π πππΌ
π1π2π
βππ
Ξ β random variable used to model the multipath fading
Ξ¦- random phase introduced by the channel
πππ· =
π12 Ξ21
2π ππ2πΌ + Ξ222πππ 2πΌ + 2Ξ21Ξ22π πππΌπππ πΌπππ π21 β π22 + π2
2 Ξ222π ππ2πΌ + Ξ21
2πππ 2πΌ + 2Ξ21Ξ22π πππΌπππ πΌπππ π21 β π22
+2π1π2πππ π Ξ21Ξ22 π ππ2πΌ β πππ 2πΌ πππ π21 β π22 + Ξ222 β Ξ21
2 π πππΌπππ πΌ
π12 Ξ11
2π ππ2πΌ + Ξ122πππ 2πΌ + 2Ξ11Ξ12π πππΌπππ πΌπππ π11 β π12 + π2
2 Ξ122π ππ2πΌ + Ξ11
2πππ 2πΌ + 2Ξ11Ξ12π πππΌπππ πΌπππ π11 β π12
+2π1π2πππ π Ξ11Ξ12 π ππ2πΌ β πππ 2πΌ πππ π11 β π12 + Ξ122 β Ξ11
2 π πππΌπππ πΌ
The definition yields πππ· =π π£
2
π β2=π΄ Ξ21
2 + π΅ Ξ222
π΄ Ξ112 + π΅ Ξ12
2
π΄ = π12π ππ2πΌ + π2
2πππ 2πΌ β 2π1π2π πππΌπππ πΌπππ π
π΅ = π12πππ 2πΌ + π2
2π ππ2πΌ + 2π1π2π πππΌπππ πΌπππ πwhere
The different types of polarization diversity can be described by the coefficients A and B
Since the A and B coefficients are the same in all 6 cases, the equations that describe the XPD are identical in all 6 cases
Slant linear and circularly polarized antennas transmit the same average performance in a static MISO system. The expected diversity gain of SL / SR linear and RH / LH CP are on average the same.
β’ Analysis assumesβ’ For CP we increased the transmitter power 3dB to maintain the same ERPβ’ The receiver is stationaryβ’ Independent of any margin improvement observed by transmitting CP to a
linearly polarized receive antenna in motion
ππΌ = πππ ππ β πππ ππππππ
Starting over a decade ago β extensive testing to quantify the benefit of transmitting CP to a linearly polarized receiver in motion
β’ Controlled environmentsβ’ Field tests in ME and FLβ’ Indoor / Outdoor / Vehicleβ’ Measurements based on RSS
and BERβ’ Different amounts of VPOL
All measurements have confirmed that transmitting circular polarization to a linearly polarized receiver in motion in a heavy scatter environment provides 5 to 7 dB of margin improvement (MI) over transmitting a linearly polarized signal to the same receiver.
β’ Gd and MI are independentβ’ 5-7dB MI is observed when transmitting a single CP signal to a linear
receiver in motionβ’ Adding a second independent path (MISO) does not change this but
adds 3dB of Gd
The total system gain of dual RH / LH CP MSIO diversity system transmitting to a linearly polarized mobile receiver in motion in a heavy scatter environment is as high as 8-10dB.
β’ A new antenna specification to considerβ’ So far we have assumed the transmit signals are completely uncorrelatedβ’ Imperfect antennas couple energy
SR/SL Linear RH/LH circular
πΌ = π ππππ π πππππππ§ππ‘πππ πΌ = π ππ₯πππ πππ‘ππ
β’ Studies : 17 dB of cross pol isolation is sufficient to reach 99% of desired data rate
All waves can be decomposed into two components with orthogonal polarization states
πΌ = 10πππ
12 +
π΄π π΄π 2 + 1
12
1
π΄π + 1π΄π β 1
2 + 1 +π΄π
π΄π 2 + 11
π΄π + 1π΄π β 1
2 β 1
SpecificationAR<1.7dB for RH/LH CP MISO
β’ Employing MISO diversity gain can add up to 3 dB in the system gainβ’ On average slant linear and circularly polarized antennas transmit the same
average performance in a stationary MISO diversity systemβ’ This is independent of any margin improvement observed by transmitting CP to
a linearly polarized receive antenna in motionβ’ Transmitting CP to a linearly polarized receiver in motion in a heavy scatter
environment can add 5 to 7 dB of margin improvementβ’ Total ATSC 3.0 system gains employing RH/LH CP diversity can be 8 to 10dB if
you choose to increase your TPO by 3dB.β’ The axial ratio specification of a RH / LH co-located system considered for
diversity should be < 1.7dB.
* The use of LH CP will require an FCC rule change
Come visit us at Booth # C2613