A non-reciprocal LC filter structure and its design methodology

This paper analyses the differences between the non-reciprocal filter design and reciprocal filter design process, gives the difficulties in the non-reciprocal filter design process, and finally concludes the general methodology of non-reciprocal filter design. After the general method is given, a third-order LC non-reciprocal filter with a center frequency of 140 MHz and a bandwidth of 20 MHz is designed and simulated from a third-order reciprocal bandpass filter circuit. The results obtained from the testing of the designed and processed third-order non-reciprocal filter show that this filter can achieve non-reciprocal transmission in the frequency range of 132 MHz-152 MHz with a forward transmission insertion loss of 8.2 dB, an isolation of more than 8 dB, and a maximum isolation of 11.6 dB in the band.