In this paper, a microstrip diplexer is designed based on a novel structure consisting of the meandrous and patch cells. It operates at 0.8 and 0.9 GHz for global system for mobile communications applications. The proposed diplexer is well miniaturized with an overall size of 0.01 λg2. It has the narrowband channels making it appropriate for the modern long-range communication systems, which are widely accepted by the industry. The introduced diplexer has the other advantages of low insertion and return losses and the good isolation between channels better than −30 dB. Moreover, there is a good upper stopband rejection so that the first and second harmonics are suppressed with a maximum level of −30 dB. The designing method is based on finding the effective parameters to control the resonance frequency, miniaturization and harmonic attenuation simultaneously. To validate the designing method and simulation results, the proposed diplexer is fabricated and measured. There is a good agreement between the simulated and measured results.
