john l. schadler continuationโฌยฆย ยท ๐๐๐ท= ๐1 2ฮ 21 2 ๐ 2๐ผ+ฮ 22 2๐ 2๐ผ+2ฮ...
TRANSCRIPT
โAntenna Technology For ATSC 3.0 โ Boosting the Signal Strengthโ
Continuation
John L. Schadler
4KUHDTV
โข
โข
โข
โข
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 โ High null fill + SFNs
โข Saturate in the vicinity of the main antenna by increasing the null fill
โข Add SFN sites around coverage perimeter to boost the signal strength outside of the high null fill area
+ SFN
โข ATSC 3.0 MISO scheme โ TDCFSโข Transmitting two uncorrelated signals to a single receiverโข Cost effective
โข Increase the complexity of the transmitter โ not the receiverโข ATSC 3.0 SFN sites will serve many receivers
โข Economical to add equipment cost at the transmit site rather than the receiver
โข Receiver remains small and affordable
โข TDCFS can be deployed in either a co-located or distributed configuration
โข Does not require any new RF equipment within the existing SFN
Co-located Distributed
โข Diversity gain throughout the coverage area
Diversity gain Boosting the RSSโก
Max diversity gain is based on the total number of independent signal paths
M transmit antennas N receive antennas
1 โค ๐บ๐ โค ๐บ๐๐๐ฅ = ๐ โ ๐
3 dB improvement in RSS can be achieved when 2 x 1 MISO diversity is applied
โข Traditionallyโข Spatial diversity
โข Separate antennasโข Difficult to implement
โข Space limitationsโข Polarization diversity
โข Co-located antenna elementsโข Orthogonal polarizationsโข Modes of operation
โข Slant linearโข RH / LH CP
Which mode of polarization diversity operation is best for ATSC 3.0 MISO?
Dual input broadcast antenna array
X
โข Max diversity gain depends on spreading the power evenly between the polarizationsโข Figure of merit
โข Cross Polarization Discrimination (XPD)โข The ratio between the available power in the vertical and horizontal polarizations
๐๐๐ท =๐ ๐ฃ
2
๐ โ2 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 ฮฑ
Dipole modeling Channel modeling
Four channel links between the transmitter and receiver
๐ โ๐ ๐ฃ
=ฮ11๐
๐๐11 ฮ12๐๐๐12
ฮ21๐๐๐21 ฮ22๐
๐๐22
๐โ๐๐ฃ
๐โ๐๐ฃ
=๐ ๐๐๐ผ โ๐๐๐ ๐ผ๐๐๐ ๐ผ ๐ ๐๐๐ผ
๐1๐2๐
โ๐๐
ฮ โ random variable used to model the multipath fading
ฮฆ- random phase introduced by the channel
๐๐๐ท =
๐12 ฮ21
2๐ ๐๐2๐ผ + ฮ222๐๐๐ 2๐ผ + 2ฮ21ฮ22๐ ๐๐๐ผ๐๐๐ ๐ผ๐๐๐ ๐21 โ ๐22 + ๐2
2 ฮ222๐ ๐๐2๐ผ + ฮ21
2๐๐๐ 2๐ผ + 2ฮ21ฮ22๐ ๐๐๐ผ๐๐๐ ๐ผ๐๐๐ ๐21 โ ๐22
+2๐1๐2๐๐๐ ๐ ฮ21ฮ22 ๐ ๐๐2๐ผ โ ๐๐๐ 2๐ผ ๐๐๐ ๐21 โ ๐22 + ฮ222 โ ฮ21
2 ๐ ๐๐๐ผ๐๐๐ ๐ผ
๐12 ฮ11
2๐ ๐๐2๐ผ + ฮ122๐๐๐ 2๐ผ + 2ฮ11ฮ12๐ ๐๐๐ผ๐๐๐ ๐ผ๐๐๐ ๐11 โ ๐12 + ๐2
2 ฮ122๐ ๐๐2๐ผ + ฮ11
2๐๐๐ 2๐ผ + 2ฮ11ฮ12๐ ๐๐๐ผ๐๐๐ ๐ผ๐๐๐ ๐11 โ ๐12
+2๐1๐2๐๐๐ ๐ ฮ11ฮ12 ๐ ๐๐2๐ผ โ ๐๐๐ 2๐ผ ๐๐๐ ๐11 โ ๐12 + ฮ122 โ ฮ11
2 ๐ ๐๐๐ผ๐๐๐ ๐ผ
The definition yields ๐๐๐ท =๐ ๐ฃ
2
๐ โ2=๐ด ฮ21
2 + ๐ต ฮ222
๐ด ฮ112 + ๐ต ฮ12
2
๐ด = ๐12๐ ๐๐2๐ผ + ๐2
2๐๐๐ 2๐ผ โ 2๐1๐2๐ ๐๐๐ผ๐๐๐ ๐ผ๐๐๐ ๐
๐ต = ๐12๐๐๐ 2๐ผ + ๐2
2๐ ๐๐2๐ผ + 2๐1๐2๐ ๐๐๐ผ๐๐๐ ๐ผ๐๐๐ ๐where
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.
โข Analysis assumesโข For CP we increased the transmitter power 3dB to maintain the same ERPโข The receiver is stationaryโข Independent of any margin improvement observed by transmitting CP to a
linearly polarized receive antenna in motion
๐๐ผ = ๐๐๐ ๐๐ โ ๐๐๐ ๐๐๐๐๐๐
Starting over a decade ago โ extensive testing to quantify the benefit of transmitting CP to a linearly polarized receiver in motion
โข Controlled environmentsโข Field tests in ME and FLโข Indoor / Outdoor / Vehicleโข Measurements based on RSS
and BERโข 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.
โข Gd and MI are independentโข 5-7dB MI is observed when transmitting a single CP signal to a linear
receiver in motionโข 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.
โข A new antenna specification to considerโข So far we have assumed the transmit signals are completely uncorrelatedโข Imperfect antennas couple energy
SR/SL Linear RH/LH circular
๐ผ = ๐ ๐๐๐๐ ๐ ๐๐๐๐๐๐๐ง๐๐ก๐๐๐ ๐ผ = ๐ ๐๐ฅ๐๐๐ ๐๐๐ก๐๐
โข 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
๐ผ = 10๐๐๐
12 +
๐ด๐ ๐ด๐ 2 + 1
12
1
๐ด๐ + 1๐ด๐ โ 1
2 + 1 +๐ด๐
๐ด๐ 2 + 11
๐ด๐ + 1๐ด๐ โ 1
2 โ 1
SpecificationAR<1.7dB for RH/LH CP MISO
โข Employing MISO diversity gain can add up to 3 dB in the system gainโข On average slant linear and circularly polarized antennas transmit the same
average performance in a stationary MISO diversity systemโข This is independent of any margin improvement observed by transmitting CP to
a linearly polarized receive antenna in motionโข Transmitting CP to a linearly polarized receiver in motion in a heavy scatter
environment can add 5 to 7 dB of margin improvementโข 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.โข 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
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