improving fm combiner/filter efficiency and size using non...
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Improv ing FM Combiner /F i l te rE f f i c iency and S ize
Us ing Non-Conven t iona l Coup l ingC o r y E d w a r d sS a l e s M a n a g e r
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Today’s Presentat ion
• Manifold / CIF Comparison
• Combining Requirements Each Technique
• Introduce Cross Coupling for Efficiency
• Introduce New Source / Load Coupling
• Small Space (Less Poles)
• More Efficiency
• New 2 Channel Design
• Manifold Channel Limited?
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Eff iciency, Manifold or Direct ional
Manifold• More efficient• All channels same VSWR• All channels same loss• Mainline offers higher voltage safety margin• Compact, light and simple• Easy to assemble• Easy to test• Easily maintainable• Lower cost (by 60%)• Simple module design and installation• Expandable
Directional• Less efficient• VSWR degrades with distance • Loss degrades with distance• Hybrids limit voltage safety margin• Large, heavy and complex• Difficult to assemble• Difficult to test• Difficult to maintain• Higher cost• Part intense module design• Expandable
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Combining Requirement
Combiner abc’sCombiner abc’s
Junction Combiner Channel isolation for reduced IM products 40 dB
Directional Combiner Enough rejection for low loss combining 27 – 30 dB
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Combining Requirements1.6 MHz Spacing Example
Junction Combiner• Isolation entirely dependent on filter• ∴ 40 dB min filter rejection• 4‐pole required for 1.6 MHz spacing
Directional Combiner• Hybrids provide directionality, or
isolation, ~ 30 dB• ∴ 27‐30 dB min filter rejection• 3‐pole required for 1.6 MHz spacing
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Chebyshev
Number of PolesChebyshev
Min. CH Spacing, MHz
Directional Junction 2 8.4 9.03 1.6 2.44 .8 1.2
Combining Requirement Summary
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Current FM BroadcastFi l ter Topologies
Chebyshev
Lump element inductively coupled filter
• Sequentially coupled from input to output• Chebshev g number from lowpass prototype/closed form equations• Normalized coupling coefficients, Mi,j determined• Coupling bandwidth given by dF1,2 = BWr * M1,2
1 2 3
,1
Coupling routing diagram
S 1 2 3 L
dF1,2 dF2,3
1 2 31 0 M1,2 02 M1,2 0 M2,33 0 M2,3 0
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• More recently, X‐coupled filters have been used to provide greater rejection
• Filters designed using insertion loss theory
= ∙∙∙ ∙∙∙
• Tri‐Section, normalized coupling coefficients extracted from polynomials
1 2 31 0 M1,2 M1,32 M1,2 0 M2,33 M1,3 M2,3 0Places zero above passband
S L
2
31
increasedincreasedreducedreduced
Tri‐Section
Current FM BroadcastFi l ter Topologies X-Coupled
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Source multi‐resonator coupling provides 2 transmission zeros
New Source/LoadMult i -Resonator Coupling
Key benefits
• Tighter channel spacing for given filter order
• Efficiency gain
• Size reduction
• Easy implementation
S 1 2 3 LS 0 1.36 0 ‐.052 01 1.36 0 1.47 0 02 0 1.47 0 1.41 03 ‐.052 0 1.41 0 1.39L 0 0 0 1.39 0
S L
2
31
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ExampleWhere this Technique was used
• Miami
• Small space for combiner
• TX has very little head room
• A frequency might be added Later
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• 99.1 MHz, high power • No Tx headroom• 3‐pole filters to minimize loss• 101.5 MHz may come in later• NEED < .1dB loss• Space constraints
Manifold
New S o u r c e / L o a d M u l t i - R e s o n a t o r C o u p l i n gS o l u t i o n f o r a n E f f i c i e n c y P r o b l e m
99.1MHz
105.1MHz
97.3MHz
93.1MHz
99.1MHz
97.3MHz
101.5MHz
n = 3VSWR = 1.05BWr = 550kHzLa = .128 dB
105.1MHz
93.1MHz
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• 24” Cavity• 3‐pole red• 4‐pole blue
New S o u r c e / L o a d M u l t i - R e s o n a t o r C o u p l i n gL o s s v s B a n d w i d t h
Loss vs BWr
Need ≈ 1 MHz BWr
Chebyshev
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New S o u r c e / L o a d M u l t i - R e s o n a t o r C o u p l i n gS o l u t i o n t o E f f i c i e n c y P r o b l e m
n = 3VSWR = 1.12BWr = 1150kHzLa = .06 dB
S 1 3
2
L
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Multi‐channel site in Miami
• Source multiple coupling used on a 3‐pole filter to provide transmission zeros and allow wider bandwidth to increase efficiency
• Filter loss:< .16 dB w/o X‐coupling< .06 dB with X‐coupling
Efficiency improvement with wider bandwidth
New S o u r c e / L o a d M u l t i - R e s o n a t o r C o u p l i n gS o l u t i o n t o E f f i c i e n c y P r o b l e m
S 1 3
2
L
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Efficiency improvement with wider bandwidth
New S o u r c e / L o a d M u l t i - R e s o n a t o r C o u p l i n gS o l u t i o n t o E f f i c i e n c y P r o b l e m
Multi‐channel site in Miami
• Source multiple coupled MODULE loss: .08dB
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New Design for 2 Sta t ion Combin ing
• Auburn
• Small space for combiner
• Very Tight timeline
• Limited resources on site
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Manifold Combiner
2‐Channel Manifold
• Filters placed ≈ n λ/2 from junctions
• Tees spaced ≈ n λ/2
• Short ≈ n λ/4 from Tee
• Short can be replaced w filter to eliminate a Tee
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Load Mult iple Coupling Combiner
LPFM Common Case Combiner
• Simplified design• Elimination of Tees and delay lines• One filter “box”
• Band tunable• Tee/delay line design not easily tuned• Spacing set by rejection levels
• Lower cost• Reduced part count• Same design for all channels• Less labor: manufacture, assemble, test
• Easy Install• Smaller size• Space limited sites
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LPFM Common Case Combiner, Test Results
Product highlights
• 3‐pole design
• 96.1 MHz and 98.5 MHz
• Loss < .45 dB
• VSWR < 1.08:1
• Isolation > 40dB
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Manifold Limitat ions
• Project
• Small space for combiner
• 19 channels
• Very close spacing of channels
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Manifold Combiner, How Many CH’s?
19 CH FM combiner, 800 kHz spacing
10 channels, 1.6 MHz spaced (odd channels)
9 channels, 1.6 MHz spaced (even channels)
Feeding RHCP and LHCP antenna
IBOC compatible
4‐Pole Filter Size and Loss
24” 14” 9” 5.5”Power* 23kW 15kW 5kW 1.3kWLoss .25dB .35dB .45dB .68dB
*Convection cooled
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Manifold CombinerLumped Element Model
10 channels, 1.6 MHz spaced
IBOC compatible
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Manifold Combiner Lumped Element Model , Optimized Results
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Manifold Combiner, w/o “drip loops”
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Actual Data after Optimizat ion, Return Loss
‐30 dB
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Actual Data after Optimizat ion, VSWR
1.06:1
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Actual Data after Optimizat ion, Transmission, WXRK, 92.3 MHz
92.3MHz .72dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WNYC, 93.9 MHz
92.3 MHz .72dB93.9 MHz .79dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WXNY, 96.3 MHz
92.3 MHz .72dB93.9 MHz .79dB96.3 MHz .72dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WSKQ, 97.9 MHz
92.3 MHz .72dB93.9 MHz .79dB96.3 MHz .72dB97.9 MHz .76dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WBAI, 99.5 MHz
92.3 MHz .72dB93.9 MHz .79dB96.3 MHz .72dB97.9 MHz .76dB99.5 MHz .75dB
Filter Loss ≈ .68dB
Combiner Loss
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WCBS, 101.1 MHz
92.3 MHz .72dB93.9 MHz .79dB96.3 MHz .72dB97.9 MHz .76dB99.5 MHz .75dB101.1 MHz .80dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WNEW, 102.7 MHz
92.3 MHz .72dB93.9 MHz .79dB96.3 MHz .72dB97.9 MHz .76dB99.5 MHz .75dB101.1 MHz .80dB102.7 MHz .83dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WAXQ, 104.3 MHz
92.3 MHz .72dB93.9 MHz .79dB96.3 MHz .72dB97.9 MHz .76dB99.5 MHz .75dB101.1 MHz .80dB102.7 MHz .83dB104.3 MHz .75dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WQXR, 105.9 MHz
92.3 MHz .72dB93.9 MHz .79dB96.3 MHz .72dB97.9 MHz .76dB99.5 MHz .75dB101.1 MHz .80dB102.7 MHz .83dB104.3 MHz .75dB105.9 MHz .77dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, WBLS, 107.5 MHz
92.3 MHz .72dB93.9 MHz .79dB96.3 MHz .72dB97.9 MHz .76dB99.5 MHz .75dB101.1 MHz .80dB102.7 MHz .83dB104.3 MHz .75dB105.9 MHz .77dB107.5 MHz .70dB
Filter Loss ≈ .68dB
Combiner Loss
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Actual Data after Optimizat ion, Transmission, X-coupled
X‐Coupledf0 +/‐ .8 MHz
Manifold Isol. 35 dBAntenna Isol.* 25 dBTx turn‐around loss 20 dBFilter rejection 35 dBIM Suppression 115 dB
* Antenna isolation typically > 30dB
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Actual Data after Optimizat ion, Isolat ion, X-coupled
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10 Channel FM ManifoldDesign/Performance
Actual Duration Times:
• Lumped element design in ANSYS – 2 days
• Mechanical design – 1 day
• Manufacturing – 10 days
• Individual filter tuning – 0.5 days
• 10 channel manifold assembly/test – 0.5 day
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Manifold Combiner Benefi ts
Specification Manifold CIF (# of modules from output)
VSWR < 1.06:1 < 1.1;1 (1st , takes a beating for others )< 1.16:1 ( 10th, pays dearly for position)
Loss, f0 < .35 dB < .35 dB (1st and keeping quite about it)< .95 dB (10th no beer money left)
• Better impedance for transmitters at ALL channels• Higher efficiency for ALL broadcasters• Lower initial cost• Lower operating cost• Design/component simplicity• Reduced size
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