Designing Matched Bandstop Filter for Very High Frequency (VHF) Band

Figure 1: Matched bandstop filter circuit
Figure 2: Double section lumped branchline coupler circuit
Figure 3: Realization of Inverter
Figure 4: Simulation result for lumped-matched bandstop filter
  1. The s21 value at the center frequency of 90 MHz has the value of — 40.97dB which equals to the suppression of incoming signal at that frequency at least 10,000 times. This conforms to the requirement for the filter to be bandstop at 90 MHz.
  2. The s11 has return loss that is better than 10 dB for almost the entire range. This means, the reflection for this range frequency is at most 1%; hence the name matched bandstop filter.
  3. It could be observed that the frequency beyond 110, the reflection goes higher than 1%, this could be lowered by optimizing the values of the circuit elements further but around the designed frequency at 90 MHz.

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FILPAL designs, and builds RF and Microwave software and hardware for Cellular, Military, Academia and Test & Measurement applications. http://www.filpal.com

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FILPAL

FILPAL

FILPAL designs, and builds RF and Microwave software and hardware for Cellular, Military, Academia and Test & Measurement applications. http://www.filpal.com

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