为进一步拓展微波光子滤波器的FSR(自由谱范围)和提高滤波器的Q值, 进行了IIR(无限冲激响应)滤波器分别与FIR(有限冲激响应)滤波器和IIR滤波器级联的研究。分析了两种级联结构的滤波特性并给出了相应的传输函数。IIR滤波器与FIR滤波器级联后的FSR与Q值是IIR滤波器的2n倍; IIR滤波器与IIR滤波器级联后的FSR是各个IIR滤波器的FSR的最小公倍数。用Matlab软件仿真验证了两种级联结构的频率响应特性, 实验验证了IIR滤波器与IIR滤波器的级联特性。IIR滤波器与IIR滤波器的级联有望实现宽频率范围内的单通带滤波器。

To further expand the Free Spectrum Range (FSR) and increase the Q factor of microwave photonic filters, this paper conducts researches on an Infinite Impulse Response (IIR) filter cascaded respectively with a Finite Impulse Response (FIR) filter and an IIR filter. Then, it analyzes the filtering characteristics of these two cascaded structures and derives the corresponding transfer functions. In the former case, the FSR and the Q factor are 2n times that of the IIR filter and in the latter case, the FSR is the least common multiple of that of each IIR filter. It simulates and verifies the frequency response characteristics of the two structures using the Matlab, and experimentally verifies the cascaded characteristics of an IIR filter with an IIR filter. The cascading of an IIR with an IIR is expected to realize single-passband filtesrs in a wide frequency range.