ABSTRACT
In radio frequency (RF) power amplifiers, the main purpose of filters is to eliminate spurious and harmonic contents from the frequency of interest. Depending on the frequency of operation and application, a filter can be implemented using lumped elements or distributed elements, or it can comprise a mix of lumped and distributed elements. The common method to analyze filters is to treat them as lossless, linear two-port networks. The conventional filter design procedure for low-pass filters (LPFs), high-pass filters (HPFs), bandpass filters (BPFs), or bandstop filters (BSFs) begins from LPF prototype and then involves impedance and frequency scaling, and filters transformation to HPFs, BPFs or BSFs to obtain final component values at the frequency of operation. Conventional parallel-coupled BPFs suffer drastically from spurious harmonics. The stepped-impedance resonator (SIR) filters can be used to realize high-performance BPFs by suppressing the spurious harmonics to overcome this problem.
