EMRFD Message Archive 12504
Message Date From Subject 12504 2016-03-15 05:20:10 k1rf_digital_stev... 12 MHz quadrature coupled bandpass filter Hi all. For those interested, I posted an LT Spice model of a quadrature coupled bandpass filter in the K1RF folder in the Files section. It is similar to the circuit in EMRFD Figure 6.93 except that it was designed for 12 MHz instead of 9 and I used L-networks for impedance matching rather than tapped tuned circuits. I also added a bridged T diplexer with a Q of 3. It was an interesting learning experience for me with getting the phasing right and seeing the effect of return loss with and without the bridged-T diplexer. The filter itself is meant more for wideband impedance matching to a mixer than high performance filtering. It is assumed that narrower bandwidth filters follow this filter for appropriate SSB or CW filtering requirements. Hope you find the LT spice model useful. I have a bunch of decent quality Fox 12 MHz crystals that I am putting good use to. I plugged their parameters into the model.
"Digital Steve", K1RF