A novel low loss microwave multiplexer design based on directional filters

A novel design method for directional filters is presented which reduces transmission loss and insertion loss. The theoretical background of directional filters is given, the frequency characteristics and transmission loss are discussed and parameters responsible for the requirements of a low loss application are worked out. A 50 /spl Omega/ multiplexer was built to act as a bandpass filter bank to separate the fundamental, second and third harmonic frequencies at the input and at the output of a digital audio broadcast (DAB) power amplifier. Finally, measurement results are compared with simulations and the improvements with respect to multiplexers previously presented are pointed out.