We propose and demonstrate a novel microwave photonic filter based on an electro-optic phase modulator (EOPM), a
tunable optical bandpass filter (TOBF) and a cascaded fiber delay interferometer (DI). The TOBF is slightly detuned
relative to the optical carrier. By using the complementary optical responses of the two output ports of DI, one port of DI
is detuned the same as the TOBF and the other is detuned opposite to the TOBF. Thus a microwave bandpass filter and a
microwave notch filter are obtained at the two ports of DI simultaneously. In the experiment, the rejection ratios of
obtained microwave notch filter and bandpass filter are 22 dB and 16 dB, respectively.
This paper firstly presents the fundamental principles of the microwave photonic filters. According to the number of the
taps of the microwave signal is finite either infinite, a microwave photonic filter is classified into finite impulse response
(FIR) filter and infinite impulse response (IIR) filter. As an example to explain how to implement a microwave photonic
filter, a specific FIR configuration is illustrated. Next, the theory and methods around how to gain high Q value is
discussed. Then, divided into FIR filter, one-order IIR filter, and multi-order IIR filter, several novel approaches to gain
high Q value are discussed and compared. The technical difficulties in multi-order IIR filter are analyzed concretely in
this part. In the end, we make a summary for the microwave photonic filters with high Q value.