Below is the response of a coupled-resonator bandpass filter with extreme bandwidth. I designed this filter purely by iterative 3D EM analysis plus some minor port-tuning work in a circuit simulator and optimisation. It is perhaps the filter with the widest passband I have designed – so far… Standard text book theory suggests it can’t be done with the filter structure I used. Well – I have done it. Not only that – it can also take a few kW of RF power.
click on the response image to view enlarged
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