Reflectionless Filters Improve Linearity and Dynamic Range in Microwave Systems
Filters are fundamental building blocks of nearly every modern RF/microwave system used to eliminate unwanted signals in receiver and transmitter architectures. Until recently, study and research in practical filter design has been largely devoted to topologies in which rejection of stop band frequencies is accomplished by reflecting undesired signals back to the source. Meanwhile, there are many applications in which these reflections produce intermodulation products, gain ripples, and other problems in system performance. For example, non-linear devices such as mixers, multipliers and high-gain amplifiers which respond to out-of-band frequencies are highly sensitive to the reflections caused by conventional filter designs. This becomes especially challenging as filters are often needed near or adjacent to active devices in the signal path to better define bandwidth or suppress unwanted harmonics.
