considerations for digital radio broadcast antenna design€¦ · example : analog tal = 18 db and...

2/15/2011

1

Ennes Workshop

Matt LelandNational Sales Manager,

SPX Communication Technology, Dielectric®

Company Confidential

Copyright@2008 SPX Corporation





http://www.spx.com/en/multimedia-library/flash/spx-flash/swf/project-portfolio-pop-up.aspx

2/15/2011

2

HD Radio™ Elevated HD Transmission LevelsHD Radio™ Elevated HD Transmission Levels

•Consideration to increase the digital power level from –20 dB up to –10 dB of analog power

•Reasons for the increase

•Improve building penetration

Spectrum of IBOC waveform

Analog

FM Signal

•Improve building penetration

•Improve reception by portable radios

•Provide equivalent coverage to the analog signal

-10 dB (10%) Total digital power

-20 dB (1%) Total digital power




Digital

Signal

Digital

Signal

0 kHz +200 kHz-200 kHz

HD Radio™ Implementation MethodsHD Radio™ Implementation Methods

High Level

10 dB CouplerHDFMVee

Best overall efficiency

10% analog and 90% digital lost

No analog lost…but 80 to 90% digital lost

A quick review

Low Level

Split Level Space Combining

A Registered Trademark of iBuquity Digital Corporation

y

Attractive option for elevated IBOC levels

Dybrid




PAGE 4

Analog Signal

Digital Signal

Common AmpTrade efficiency for linearity

2/15/2011

3

High Level CombiningHigh Level Combining

Digital I/PStation Load

10 dB Hybrid Example10 dB Hybrid Example

Analog I/P Combined O/P




“Easy”and inexpensive

but….

Very inefficient

All pages and images © 2007 Dielectric Communications, A unit of SPX Corporation. Information contained herein is confidential property of SPX. It is to be used solely for the purpose provided, and is not to be disclosed to others without the prior written consent of SPX.

Effect of Cross Coupling on VSWR Performance

By Definition:The VSWR of the individual hybrid

inputs can only be as good as theinputs can only be as good as the isolation between the outputs, assuming the output loads (the dipoles) are perfect matches.

Assume Isolation = 20 dBAssume Isolation = 20 dB



Company ConfidentialAll pages and images © 2007 Dielectric Communications, A unit of SPX Corporation. Information contained herein is confidential property of SPX. It is to be used solely for the purpose provided, and is not to be disclosed to others without the prior written consent of SPX.

Assume Isolation = 20 dBAssume Isolation = 20 dB

Best case VSWR = 1.22:1 Best case VSWR = 1.22:1 into each port into each port

2/15/2011

4

Impact

•High level combining is not practical for more than +2 dB increase in HD Radio sideband power

•Split level combining is not practical for more than +4 dB increase in HD Radio sideband powerincrease in HD Radio sideband power

Common Amplification

What’s Left ?

Requires linearized Xmtr




PAGE 7

Source: Geoff Mendenhall – VP Transmission Research and Technology, Harris Corporation. “Transmission System Requirements for Increased HD Radio Sideband Power” - 2008 National Public Radio Engineering Conference

Space Combining

Will require 10 dB more isolation from the antennas

Isolation is keyElegant but technically challenging

HD Radio™ Space Combining Implementation Methods HD Radio™ Space Combining Implementation Methods

Interleaving Common Radiator

Separate Antennas




PAGE 8

2/15/2011

5

HD Radio™ Space Combining HD Radio™ Space Combining –– Required IsolationRequired Isolation

How much analog to digital isolation is required from the antenna?

Why?




Is the analog leaking into the digital the problem?

Is the digital leaking into the analog the problem?Or

HD Radio™ Spectral ReHD Radio™ Spectral Re--growthgrowth

Spectral re-growth is directly related to the analog - digital isolation. It describes the inter-modulation products generated when a digital and analog transmitter share a common system

Three sources

• Interaction between the two sidebands within the digital transmitter

• Analog signal “leaking” into the digital transmitter

• Digital signal “leaking” into the analog transmitter

Analog

Mask

Analog

164 kHz Spacing

Mask

328 kHz Spacing




Analog

Digital Sidebands

Spectral re-growth

Spectral re-growth

Caused by digital sideband interaction within a digital only transmitter

Analog

Digital Sidebands

Spectral re-growth

Spectral re-growth

Caused by poor analog to digital isolation or non-linearity's in a common amplification transmitter

PAGE 10

2/15/2011

6


•What level must the spectral re-growth be under?

•The spectral re-growth level is the vector sum of the analog interference into the digital plus the digital interference into the analog

FCC Mask

iBiquity Mask

Un-modulated FM analog carrier

•What is transmitter turn around loss? (TAL)

•TAL is the ratio of the incoming interfering signal to the generated re-growth level

•Is the TAL of all transmitters the same

•Tubes have TAL of 6 to 12 dB

•Solid state have TAL of 16 to 25 dB

•In the remainder of this presentation we will assume the worst case turn around loss for each application shown -90

-80

-70

-60

-50

-40

-30

-20

-10

0

iBiquity Mask




PAGE 11

application shown. -90

-750 -600 -450 -300 -150 0 150 300 450 600 750

Digital sideband

The combined re-growth sum of the analog interference into digital and digital interference into analog must be less then –74.4 dB

PAGE 11

Source: Geoff Mendenhall – VP Transmission Research and Technology, Harris Corporation. “Transmission System Requirements for Increased HD Radio Sideband Power” - 2008 National Public Radio Engineering Conference


-27 dB

Isolation budget - digital into analog for –20 dB IBOC to suppress spectral re-growth in the analog transmitter below the iBiquity mask

-30

-20

-10

0

-41.4 dB

Digital to Analog Power -41.4 dB

-90

-80

-70

-60

-50

-40

-750 -600 -450 -300 -150 0 150 300 450 600 750




PAGE 12

-6 dB

Antenna Isolation -27.0 dBCirculator 0.0 dBTurnaround Loss -6.0 dB

Re-growth Level -74.4 dB

PAGE 12

2/15/2011

7

-27 dB for -10 dB

-23 dB for -14 dB


Isolation budget - analog into digital for –10 & 14 dB IBOC to suppress spectral re-growth in the digital transmitter below the iBiquity mask

-30

-20

-10

0

Digital relative to analog 10dB 14 dbDigital to Analog Power -31.4 dB -35.4 dB

-90

-80

-70

-60

-50

-40

30

-750 -600 -450 -300 -150 0 150 300 450 600 750




-31.4 dB-20 dB

-16 dB

PAGE 13

g gAntenna Isolation -27.0 dB -23.0 dBCirculator 0.0 dB 0.0 dBTurnaround Loss -16.0 dB -16.0 dB

Re-growth Level -74.4 dB -74.4 dB

PAGE 13


Isolation budget - analog into digital for –20 dB IBOC to suppress spectral re-growth in the digital transmitter below the iBiquity mask

-27dB

-30

-20

-10

0

-90

-80

-70

-60

-50

-40

30

-750 -600 -450 -300 -150 0 150 300 450 600 750

With Circulator WithoutDigital to Analog Power -41.4 dB -41.4 dBA t I l ti 27 0 dB 27 0 dB




PAGE 14

-41.4 dB-20 dB

-16 dB

Antenna Isolation -27.0 dB -27.0 dBCirculator -20.0 dB 00.0 dBTurnaround Loss -16.0 dB -16.0 dB


PAGE 14

2/15/2011

8


-37 dB for -10 dB-33 dB for -14 dB

-30

-20

-10

0

Isolation budget - digital into analog for –10 dB IBOC to suppress spectral re-growth in the analog transmitter below the iBiquity mask

-31.4 dB

-90

-80

-70

-60

-50

-40

-30

-750 -600 -450 -300 -150 0 150 300 450 600 750

Digital to Analog Power -31.4 dB -35.4 dBAntenna Isolation 37 0 dB 33 0 dB




PAGE 15

-6 dB

Antenna Isolation -37.0 dB -33.0 dBCirculator 0.0 dB 0.0 dBTurnaround Loss -6.0 dB -6.0 dB


PAGE 15


35

40

Required

-10 dB IBOC

-12 dB IBOC

Analog Transmitter Turn Around Loss vs. Required Antenna Isolation for Different Digital Power Levels

15

20

25

30

35Antenna A

nalog to Digital Iso

-16 dB IBOC

-18 dB IBOC

-14 dB IBOC

-20 dB IBOC




PAGE 16

10

6 10 14 18 22 26

Analog Transmitter Turn Around Loss (dB)

lation (dB)

Tube Transmitters Solid State Transmitters

2/15/2011

9

-15

-10

HD Radio™ Required Isolation For Systems Using a Coupler/Injector/HybridHD Radio™ Required Isolation For Systems Using a Coupler/Injector/Hybrid

Isolation headroom is required to allow for changes in antenna VSWR due to rain, snow, etc.

Example : Analog TAL = 18 dB and IBOC level is –12 dB requires 23 dB of antenna isolation

Change in VSWR

-35

-30

-25

-20

Dig

ital / An

alog

Isolatio

n (d

B)

inclu

din

g 20 d

B fro

m circu

lator

30 dB Factory Ant Isolation



Required IsolationFactory Antenna

Isolation

Change in VSWR of antenna




-40

1 1.1 1.2 1.3

PAGE 17PAGE 17

Change in VSWR of antenna

An antenna with 33 dB isolation can withstand a 1.1:1 VSWR variation with analog TAL=18 dB at –12 dB IBOC

AnalogDigital



•Spectral re-growth caused by the digital signal getting into the analog is a much bigger problem than the analog into the digital

Th t f i d t i l ti d d

Required Isolation Summary

•The amount of required antenna isolation depends on

•Analog transmitter TAL

•IBOC level

•The amount of antenna performance headroom necessary for inclement weather

Th t t t “Don’t worry about the antenna’s




•The statement Don t worry about the antenna s isolation….just put in a circulator”, is completely inaccurate

PAGE 18

2/15/2011

10

>40 dB Isolation

Interleaved Antennas




PAGE 19http://www.publicradiotulsa.org/antenna.html

Interleaving

Two independent arrays interleaved vertically in the same plane

Full array prototype testing 2003

HD Radio™ Space Combining HD Radio™ Space Combining -- InterleavingInterleaving




But…..Antennas are sociable creatures. “How do you stop two antennas tuned to the same frequency from talking to each other?”

AnalogDigital

PAGE 20

U.S. Patents 6,914,579 6,972,731 & 7,102,589

2/15/2011

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Interleaving and Isolation

Factors that govern the level of isolation achievable through interleaving

1. Element elevation pattern C t ll d th h

HD Radio™ Space Combining HD Radio™ Space Combining –– Interleaving IsolationInterleaving Isolation

2. Polarization

3. Quality of the circular polarization

4. Grounding Controlled through smart design




PAGE 21

Interleaving - Isolation vs. H/V Ellipticity

25

30

Loss of 10 dB in isolation if Vpol is increased 2 dB over Hpol


0

5

10

15

20

0 2 4 6 8 10 12 14 16 18

Iso

lati

on




Axial Ratio

True CP = Good Isolation

Elliptical Polarization = Poor IsolationThe level of isolation is heavily dependent on the quality of circular polarization. If the elements do not exhibit true circular polarization, the benefit of the RH /LH technique is lost.

PAGE 22

2/15/2011

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Interleaving – Using Polarization Diversity to Achieve Isolation

Analog Right Hand Polarization

•Challenge:•How do you stop two antennas tuned to the same center frequency from talking to each

Two separate arrays interleaved vertically in the same plane


Polarization

Analog Right Hand P l i ti

Digital Left Hand Polarization

same center frequency from talking to each other?

•Solution - Oppositely polarize them

RH Polarized Signal




Polarization

LH Receive Antenna

PAGE 23

Interleaving - Element Choice

330 300

1.0D=3”

D=38”

“Stub – Loop” type antennas exhibit a large amount of Hpol downward radiation


330

300

270

240

210180

150

120

90

60

30

0.0

0.2

0.4

0.6

0.8

D

The direction of radiation changes from parallel to

Hpol elevation pattern of a loop

Coupling

Analog

Digital




The direction of radiation changes from parallel to orthogonal to the loop as the diameter increases

Not a good choice for high isolation

Digital

PAGE 24

2/15/2011

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Ring antennas have low downward radiation

Interleaving - Element Choice


+-

330

300 60

300

0.2

0.4

0.6

0.8

1.0

Coupling

Analog

Digital

+ -

Opposing currents in the up and down direction




PAGE 25

270

240

210180

150

120

900.0

0.2Digital

> FCC allows digital and analog antenna separation of 3 sec in latitude and longitude at 70 to 100% HAAT

> Separate antennas WILL have different coverage

Separate Separate –– Auxiliary AntennaAuxiliary Antenna

> The digital signal will start to degrade the analog as the 20 dB headroom is eroded

12 Bay

Main antenna0.4

0.5

0.6

0.7

0.8

0.9

1

Digital signal overriding the analog




4 Bay

Aux antenna 0

0.1

0.2

0.3

-3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11

Degrees Below Horizontal

2/15/2011

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Array Elevation Analog Antenna Only Array Elevation Interleaved

Measured Elevation Patterns




Are You Concerned About RFR Exposure?




2/15/2011

15

ELEVATION PATTERN

RMS Gain at Main Lobe 4.20 ( 6.23 dB ) Beam Tilt 0.00 degRMS Gain at Horizontal 4.20 ( 6.23 dB ) Frequency FM

Calculated / Measured CALCULATED Drawing # 08F420000-90

0.8

0.9

1

8 BAYS, 1 WAVELENGTH SPACED

CaAc0.3

0.4

0.5

0.6

0.7




0

0.1

0.2

-10 0 10 20 30 40 50 60 70 80 90

ELEVATION PATTERN



0.9

1

8 BAYS .50 WAVELENGTH SPACED

CaAc0.3

0.4

0.5

0.6

0.7

0.8




0

0.1

0.2

-10 0 10 20 30 40 50 60 70 80 90

2/15/2011

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ELEVATION PATTERN



0.9

1

8 BAYS 7/8 WAVELENGTH SPACED

CaAc0.3

0.4

0.5

0.6

0.7

0.8




0

0.1

0.2

-10 0 10 20 30 40 50 60 70 80 90

Measured Azimuth Patterns

Interleaved




All pages and images © 2007 Dielectric Communications, A unit of SPX Corporation. Information contained herein is confidential property of SPX. It is to be used solely for the purpose provided, and is not to be disclosed to others without the prior written consent of SPX.

2/15/2011

17

Stacked Arrays




PAGE 33

Differences in azimuth pattern

Example In this example both the auxiliary and main antennas

HPOL Aux Ant

HPOL Main Ant

330

300 60

300

0 20.30.40.50.60.70.80.91.0

Separate Separate –– Auxiliary AntennaAuxiliary Antenna

HD Radio Implementation MethodsHD Radio Implementation Methods

> Example : In this example both the auxiliary and main antennas were optimized through a pattern study…Best Case

> Remember….The digital signal will start to degrade the analog as the 20 dB headroom is eroded

5 000

10.000

15.000

20.000

dB

)

270

240

210180

150

120

900.00.10.2

330

300 60

300

0.20.30.40.50.60.70.80.91.0

Main (analog) signal strength / Aux (digital) signal strength




-20.000

-15.000

-10.000

-5.000

0.000

5.000

1 180 359

Azimuth Angle

Mai

n /

Au

x (d VPOL Aux Ant

VPOL Main Ant

270

240

210180

150

120

900.00.1

2/15/2011

18

Anechoic Chamber




Pattern Study

Detailed information is needed to create an accurate model




2/15/2011

19

Once The Horns Were Removed An Amazing Improvement In Coverage Was RealizedThe Names Have Been Changed to Protect the Innocent




Having Accurate Information to Set-up Your Pattern Test is Absolutely Critical to Obtain The Best Results

Dielectric Offers a Questionnaire to Guide You Through Gathering The Necessary Details

Please Provide as Much Information As Possible. It may be necessary to have a qualified climber measure the tower and apurtenences in the area where the antenna is to be installed.




a e a s o be s a ed

You may have to have the tower surveyed to determine the leg azimuths. This is particularly critical for directional antennas

2/15/2011

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Reduced Scale Model Anechoic Chamber Testing, 1 : 4.4




Full Scale Test




2/15/2011

21

Test ModelDetails Can Make All The Difference

Conduits

Bracing

Sizes

Leg Diameters




Tower Width vs. Azimuth




18” Face 24” Face

2/15/2011

22

Tower Width vs. Azimuth




36” Face 48” Face

Rotation of Antenna on Tower Leg

LEFT




CENTER

RIGHT

2/15/2011

23

Frequency vs. Azimuth, Same Tower.. Same Offset

88 MH




88 MHz98 MHz

108 MHz

Face Mounted Antennas

88 MHz




108 MHz

88 MHz Rotated

2/15/2011

24

HD Radio™ Dielectric Interleaved Field ResultsHD Radio™ Dielectric Interleaved Field Results

Clear Channel – Chattanooga, TN

– 20 dB IBOC + Analog Waveform

Isolation > 40 dBNo sign of spectral re-growth

No Circulator!

Dielectric HDR Series Interleaved Antenna

-20 dB IBOC

(-41.4 dB)




Digital Tx Solid State

TAL > 20 dB

Analog Tx Solid State

TAL > 20 dB

Combined sample output of analog and digital transmitters

PAGE 47

Interleaved Arrays – Field DataInterleaved Isolation

-45

-40

-35

-30

Iso

lati

on

(d

B)

Interleaved Isolation

-35

-30

-50

103.5 103.55 103.6 103.65 103.7 103.75 103.8 103.85 103.9

Frequency (MHz)

Interleaved Isolation

-40

-35

-30

Isola

tio

n (dB

)

WQPR

KZTH




PAGE 48

-50

-45

-40

88.5 88.55 88.6 88.65 88.7 88.75 88.8 88.85 88.9

Frequency (MHz)

Iso

lati

on

(d

B)

-50

-45

88.3 88.35 88.4 88.45 88.5 88.55 88.6 88.65 88.7

Frequency (MHz)

WTRZ

U.S. Patents 6,914,579 6,972,731 & 7,102,589

2/15/2011

25

Interleaved Arrays – Field Data

Dual Frequency Antenna – 94.7 & 101.1 MHz KESS

KRTH

KAMP

Isolation - Analog to Digital

-33

-31

B)

Isolation - Analog to Digital

-30

-20

-10

0

atio

n (dB)




PAGE 49

-45

-43

-41

-39

-37

-35

88 93 98 103 108

Frequency (MHz)

Iso

lati

on

(d

B

-60

-50

-40

107.4 107.6 107.8 108 108.2 108.4

Frequency (MHz)

Isola

U.S. Patents 6,914,579 6,972,731 & 7,102,589

KESS – Isolation Verification

Analog TPO 28,000 Watts 14.47 dB

Analog Line Efficiency 71.20% (1.48 dB)

Digital Line Efficiency 61.50% (2.11 dB)

Analog - Digital Isolation (44.4 dB)

Analog Power at Digital Transmitter (33.52 dB) 1.2 Watts

Digital TPO 300 Watts (5.22 dB)

Digital VSWR 1.04:1 (34.0 dB)

Reflected Power from VSWR 0.2 Watts




PAGE 50

Total Reflected Power at Digital Transmitter 1.4 Watts

Spectral Re-growth into Analog at -20 dB (-10 dB) -95.4 dB (-105.4)

Spectral Regrowth into Digital at -20 dB (-10 dB) -105.4 dB (-115.4)

*Assume -6 dB for TAL on Analog Xmtr and -16 dB for TAL on Digital Xmter*

Spectral Re-growth well below -74.4 Mask Limit

2/15/2011

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KESS – Isolation in Inclement Weather

Analog TPO 28,000 Watts 14.47 dB

Analog Line Efficiency 71.20% (1.48 dB)

Digital Line Efficiency 61.50% (2.11 dB)

Analog - Digital Isolation (35.4 dB)

Analog Power at Digital Transmitter (24.52 dB) 3.5 Watts

Digital TPO 300 Watts (5.22 dB)

Digital VSWR 1.04:1 (34.0 dB)

Reflected Power from VSWR 0.2 Watts

4 Watts




PAGE 51

Total Reflected Power at Digital Transmitter 3.7 Watts

Spectral Re-growth into Analog at -20 dB (-10 dB) -86.4 dB (-96.4)

Spectral Regrowth into Digital at -20 dB (-10 dB) -96.4 dB (-106.4)

*Assume -6 dB for TAL on Analog Xmtr and -16 dB for TAL on Digital Xmter*

Spectral Re-growth well below -74.4 Mask Limit

> Efficient• Eliminates the high losses associated with high level combining• Efficient use of tower space; only requires 10’ of additional aperture

> Future Proof• Interleaving accepts any elevated level of IBOC• Even if HD Radio does not gain acceptance, the broadcaster is left with a completely functional auxiliary

HD Radio™ Space Combining HD Radio™ Space Combining –– Interleaving AdvantagesInterleaving Advantages

antenna system

> Simple / Reliable• Industry proven and accepted antenna types• HD array can be interleaved within an existing analog array without affecting the current antenna system• Provides consistent coverage area for both analog and digital

> Analog/Digital - Completely separate antenna systems• If a failure occurs in an interleaved solution, either input, digital or analog can be swapped and used as an

emergency standby

> Flexibility • The concept can be applied to mixtures of feed designs or antenna type




• The concept can be applied to mixtures of feed designs or antenna type• Series – Series, Series – Branch, Branch – Branch, Branch – Series• M-bays and M-bays, C-bays and C-bays, M-bays and C-bays

Bottom Line….Interleaving is “Low Risk” and “Future Proof”

PAGE 52

2/15/2011

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Interleaving is the best solution for

•Side mount

•Low to medium power

HD Radio™ Space CombiningHD Radio™ Space Combining

•Bandwidths < 10 MHz

But what about…

•Top mount

•Broadband

•High powerMaster antenna systems




PAGE 53

•Multiplexed

Common radiator solutions are more suitable for full band multi-station masters

HD Radio Common Radiator

2/15/2011

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Common Radiator and Isolation

Factors that govern the level of isolation achievable in a common radiator

1. Cross coupling C t ll d th h

HD Radio™ Space Combining HD Radio™ Space Combining –– Common Radiator IsolationCommon Radiator Isolation

2. Mutual coupling

3. Radiator VSWR

4. Feed system VSWR Controlled through

smart design




PAGE 55

Cross coupling

addition at random phasesMutual coupling

HD Radio™ Space Combining HD Radio™ Space Combining –– Common Radiator Isolation BudgetCommon Radiator Isolation Budget

Expected isolation of a typical style panel antenna

Mutual coupling

Power divider VSWR

Feedlines VSWR

Radiator VSWR

Cross coupling

Feedlines

Power divider

Radiator

Source VSWR




PAGE 56

Analog

DigitalExpected Isolation

Cross coupling (25 dB) 1.12 0.057Mutual coupling (20 dB) 1.22 0.099Radiator impedance 1.15 0.070Feed lines/connectors 1.04 0.020Power dividers 1.05 0.024

Expected Isolation 17.1dB

2/15/2011

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Define cross coupling and mutual coupling

Cross coupling is the inter-bay dipole to dipole coupling


dipole coupling

Mutual coupling is layer to layer coupling




PAGE 57

HD Radio™ Space Combining HD Radio™ Space Combining –– Common RadiatorCommon Radiator

Digital - left hand CP

•Crossed dipoles fed by a 90 degree hybrid

•Input ports to the hybrid are fed with separate analog and digital signals

Analog - right hand CP•The hybrid combines the signals and feeds the dipoles

•Systems produce an analog right hand circularly polarized signal and a digital left hand circularly polarized signal




PAGE 58

U.S. Patents 6,914,579 & 6,934514

2/15/2011

30

The isolation between the input ports of a hybrid coupler can only be as good as the load

reflection AND/OR the isolation between the output portsCross coupling


C

C

Isolation40

60

Isolation




PAGE 59

C0

20

1 1.5 2

Isolation

VSWR mismatch

Reflections from mismatches and coupling have the same effect. They degrade the isolation between the input ports


How can the isolation of a typical common radiator be improved?

The only way to achieve analog to digital isolation in a common The only way to achieve analog to digital isolation in a common radiator solution is to reduce cross coupling and mutual coupling radiator solution is to reduce cross coupling and mutual coupling and have very low VSWR in each radiator inputand have very low VSWR in each radiator input

Not an easy task




Not an easy task…………

PAGE 60

2/15/2011

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TQT™ -Transverse Quadrilateral Technology

Dielectric has developed a radiator design which:

•Has very low cross coupling

•Has very low mutual coupling

HD Radio™ Space Combining HD Radio™ Space Combining –– Common Radiator TQT TechnologyCommon Radiator TQT Technology

•Excellent VSWR performance for both analog and digital inputs




PAGE 61

Protected by U.S. Patents 6,914,579 & 6,934514

How TQT™ Works – Elimination of Cross Coupling

Non-crossover Hybrid coupler




Hybrid coupler analysis applied to the TQT™ element

2/15/2011

32

TQT™ Element Driven by Loop Currents

This analysis leads to the understanding that the TQT™ radiating element is driven byloop currents as opposed to linear currents that would be found on a typical crosseddipole configuration.




How TQT™ Works – Minimizing Mutual Coupling

Given the loop nature of the element, loop antenna theory can be applied to understand how mutual coupling is minimized.

> VPOL propagates perpendicular to loop; in loops neutral planeO




• No VPOL coupling

> Faces 1 and 3 are orthogonal to HPOL; in the neutral plane• No coupling

> A potential difference can only be created between faces 2 and 4• The voltage induced between the sides is proportional to the

distance between them

2/15/2011

33


Expected isolation of a top / side mount TQT with a hybrid on the back of each panel

Cross coupling

Source VSWR Cross coupling (40 dB) 1.02 0.010Mutual coupling (32 dB) 1 05 0 024

Mutual coupling

Radiator VSWR Hybrid




PAGE 65

Mutual coupling (32 dB) 1.05 0.024Radiator impedance 1.05 0.024Feed lines/connectors 1 0.000Power dividers 1 0.000

Expected Isolation 31.1dBAnalog

DigitalExpected Isolation

VS

WR

1.08

1.12

1.16

1.2

AnalogDigital


Side mount TQT measured performanceR

1

1.04

88 92 96 100 104 108

30

-20

-10

0

Frequency

Isolatio




PAGE 66

-50

-40

-30

88 92 96 100 104 108

Frequency

on

2/15/2011

34

330

300

270 90

60

30

0

0.00.10.20.30.40.50.60.70.80.91.01.11.21.3

Black CompositeBlue HPOL

Red VPOLGreen RMS

HDFMVee

Top Mount


HDFMVee TQT measured performance

270

240

210180

150

120

VSWR vs. Frequency

1.1

1.15

1.2

SW

R

Isolation between analog and digital




1

1.05

88 93 98 103 108

Frequency (MHz)

VS

Analog Input Digital Input

Field measured isolation > 30 dB without the use of a circulator

PAGE 67

Analog Input (RHP)

Field Data from Similar Designs Field Data from Similar Designs –– St. St. Louis, MOLouis, MO

Includes 1,100 ft plus of

Transmission Line,

Power Splitter, Phasing

Loop, etc.

1.10:1 VSWR



Company Confidential February 15, 2011 68

Digital Input (LHP)

1.10:1 VSWR

2/15/2011

35

Analog Input (RHP)

Field Data from Similar Designs Field Data from Similar Designs ––Portland, ORPortland, OR




Includes 1,100 ft plus of Transmission

Line / Flex Line and Master Antenna

Digital Input (LHP)

Antenna LHCP

Antenna RHCP

Dielectric Antenna IsolationDielectric Antenna Isolation

•Isolation is Transmission Measurement•One TL (RHCP) to Other TL (LHCP)




Does Not Include or Require Circulators

Isolation From Field Does not Include 25 dB Additional from CirculatorsInvestment Per Station for Poor Antenna Design is Over $25k Per StationDC Isolation always Shown w/o CirculatorsReoccurring Operating Costs Reduced Monthly (Power, HVAC, etc)

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HD Radio™ SummaryHD Radio™ Summary

Implementation Methods

High Level Combining Split Level Combining Common Amplification

Space Combining

Separate Antennas

•Most efficient

•Attractive at elevated IBOC levels

•Inefficient

•Not practical for elevated IBOC levels

•Coverage congruency may cause host analog interference

•Most elegant solution

•Linearity for efficiency

•Transmitter manufacturers working to improve




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Common RadiatorInterleaving

•Side mount solution < 10 MHz bandwidth

•Simple / Reliable / Flexible

•Low risk – future proof

•Full band master antenna solution

Keys to success

• High Analog Transmitter TAL

•Antenna A/D Isolation




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Questions?

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Filters and Combiner Systems

•Dibrid Coupler

•Bandpass Filters

•Branch Combiners

•Constant Impedance Combiners

•Custom RF Components and Sub systems




•Custom RF Components and Sub-systems

High Level High Level -- “Lossy” Combining“Lossy” Combining

10 dB Hybrid10 dB Hybrid

Analog I/P Combined O/P

“Easy”and inexpensive




but….

Very inefficient

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10 DB INJECTOR SWITCHER COMBINER

•SWITCHABLE ANALOG & IBOC•HIGHLY RELIABLE•LOW VSWR•LOW LOSS•COMPACT

•ON THE BENCH 43 DB ISOLATION

•IN THE FIELD•ISOLATION IS LOAD DEPENDANT

•LOSE 10% ANALOG & 90% IBOC

Operational Modes:

Analog plus Digital to antenna





Analog to Antenna, Digital to Load

Analog to Load, Digital to Antenna

Analog plus Digital to Load

HDR SPLIT LEVEL™ DIBRID

•HOT SWITCHED ANALOG & ANA-IBOC•HIGHLY RELIABLE•STABLE•COMPACT•EFFICIENTC•ISOLATION= 40 DB ON BENCH•ISOLATION LIMITED BY RETURN LOSS OF SYSTEM BEYOND OUTPUT•LOSE 75% OF IBOC ONLY•GET 100% OF ANALOG

Operational Modes:






Analog to Antenna, Digital to Load

Analog to Load, Digital to Antenna

*Does Not provide Analog plus Digital to Load Option

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Split Level Combining Split Level Combining -- DibridDibrid

> Advantage: No analog power lostExample

Tx1 = Analog 28 kWTx2 = Analog 7 kW + 1.75 kW Digital (4:1 Ratio)

P 35 kW Analog + 350 W Digital (Full Power Digital)

PT ANT

PT ANT = 35 kW Analog + 350 W Digital (Full Power Digital)PT LOAD = 1.4 kW Digital

> Different modes of operationDifferent transmitter combinations

> Switchable under power

> Utilizes standard components




Tx2

Solid State

Analog + Digital

T ANT

100 % Analog

10% to 20% Digital

PT Load

0 % Analog

80% to 90% Digital

Depends of the power ratio of the analog transmitters

Bandpass Filters

• IBOC compatible• Stable

• Wide pass band & VSWR• Wide pass-band & VSWR bandwidth eliminate drift problems.

• Truly modular, additional sections may be bolted on in the event of requirement change. Allows stocking of modules for quick delivery.

• Retunable• Fixed iris• Invar probe adjuster• Efficient




• Low loss filter design rarely requires forced air cooling

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Filter Response for 3, 4 & 5 Stage Filters

2.21062 108

22

17

trans f( )

refl f p

freq .850freq 1.0

30

20

10

0Filter Response 2.448807 10

4

24

30trans f( )

refl f p

freq .850freq 1.0

30

20

10

0Filter Response

ns, R

efl C

oeff

60

Plotcent 2Plotcent 2 f f p100.9 101.3 101.7 102.1 102.5 102.9 103.3 103.7 104.1 104.5 104.9

60

50

40

Frequency

60


60

50

40

Frequency

Tra

n

2.302513 104

trans f( )

freq .850freq 1.0

20

10

0Filter Response

Coe

ff




60

47

39

refl f p


60

50

40

30

Frequency

Tra

ns, R

efl

Branch Combiner

• Approximately 1/3 the cost of a constant impedance combiner

• For systems of up to 3 stations• Frequency Spacing >1.2 MHz• Minimum floor-space required, can be

configured in a number of variations to fit in cramped spaces

• Short lead time availability due to modular design

• Filters fit through standard single door




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Typical Constant Impedance Combiner

•The Most Efficient In the Industry

•Best Frequency Response in the IndustryIndustry

•Expandable Virtually Any Number of Stations

•Stable-Fixed Iris Design

•The Most Reliable, Never Had a in-field module Failure

•Highest Power Systems In Service

•Temperature Stable Installed




Temperature Stable, Installed Systems with Individual Inputs of as much as 44 kW Convection Cooled.

IBOC compatible for low loss insertion

Manifold Combiners

• Uses Standard Bandpass filters

• Smaller footprint than CIF Units

• For up to 10 stations

• Excellent Electrical Performance• Excellent Electrical Performance

• Economical

• Patented Technology




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Patents Dual input / Interleaved Antennas




PAGE 83

Interleaved Patents




PAGE 84

considerations for digital radio broadcast antenna design€¦ · example : analog tal = 18 db and...

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