Filter Retuning DemonstrationD i l F ll S RF E i

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Daniel Fallon, Sr. RF Engineer

Filter Tuning

• Retune 150 Watt Filter from ch 42 to ch 30

• Uses Agilent Time Domain Tuning Technique

• Agilent AN1287-8 “Simplified Filter Tuning Using Time Domain”

• Requirements

• VNA with time domain option (8753ES / )EN5071…)

• 7/8” deep socket wrench

• ½” wrench (deep socket preffered)

• 1/16” Allen Wrench

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Sequence• Capture memory trace of tuned filterp y

• Set frequency of new channel and recalibrate

• Preset all coupling loop depthsPreset all coupling loop depths

• Set input coupling and resonator 1 (each side)

• Rough tune resonators 2 and 3 (each side)• Rough tune resonators 2 and 3 (each side)

• Time domain fine tune res 1 to 3 (each side)

• S21 fine tune cross coupling• S21 fine tune cross coupling

• Time domain fine tune all

F d i fi i hi t h t i /• Frequency domain finishing touches – centering / bandwidth / frequency

• Lock down

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• Lock down

100/150/200 Watt Filter

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Resonators, Fine matchers and Loops

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Initial Channel Measurement

• Span 30 MHz• Full two Port Cal

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Full two Port Cal• Shown with limits – LPTV Stringent Mask

Coupling Presets

• All coupling loops and Cross coupler position pre-set to height off case from chart

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Coupling Heights

• Cross Coupler Height

• Coupling Loop Height

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Loosen all resonators

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Resonator # 1 and input coupling tune

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Rough In Resonator #2

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Rough In Resonator #3

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Initial Time Domain Tune

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Adjust Cross Coupling

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Bandwidth Adjust

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• All loops deeper = wider filter

Frequency Adjust

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• All fine matchers into cavity= tune down

Fine Tune in Time Domain

• S11 Log Mag display data and memory

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S11 Log Mag, display data and memory• Band-pass time domain transform• Start time -20 ns, stop time ~650 ns

Polar Plot Centering

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• Input coupling and resonator 1

Lock Down Tuned Filter

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• Put tuned filter into memory, do one screw at a time

CONCLUSIONS

• Tuned filter can serve as a template for new channel

• Time domain option on VNA makes tuning much easierTime domain option on VNA makes tuning much easier

• Dielectric offers one time re-tuning with low power filters

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