Simulation and analysis: The final circuit was simulated, where
the junction capacitance of the PIN diodes was set to 0.2pF. Fig.3 shows
the transmission coefficient when the diode is progressively turned on.
It can be seen that when the PIN diodes are off, the proposed BPLF
exhibits filterability. As the number of triggered-on PIN diodes
increases, the isolation grows, showing better protection performance.
As for the response process, Fig.4 shows the waveforms of the input and
output. It can be seen that the output power remains almost the same for
1W, 4W and 16W input levels, which means well flatness. Also, it can be
observed that response time is at the nano-second level.
Experimental results: In Fig.5, the comparison of simulation and
test results in the small-signal state is plotted. It can be seen that
the return losses at the input and output ends are better than -15dB.
The insertion loss at 8.2 to 9.0 GHz is about 3.5dB in passband. As a
bandpass filter, its relative bandwidth reaches 9.3%.
The limiting measurement performance in different frequencies and the
assembled BPLF with the dimension of 14.5mm*10.5mm*0.385mm are shown in
Fig.6. The alumina surface film process is adopted for fabrication of
the structure and micro-assembly technology is adopted to bond PIN
diodes. The details are shown in Fig.7. The pulse width of tested high
power signal is 1us and the period is 1ms. The results show that the
threshold level of the BPLF is about 13dBm and the limiting level is
less than 17dBm with 50W injection.
Conclusion: A concept of BPLF based on comb line structure has
been presented and experimentally
investigated,
exhibiting dual selectivity of frequency and power, which is significant
for receiver in the complex environment.
Fig 3 Frequency responses of structures when different number of
PINs are triggered on
Fig 4 3 power levels input with their corresponding output