A duplexer system for a radio telephone is designed and fabricated for 800 MHz band by using only seven dielectric resonators. The transmitting band pass filter is designed in the type of the elliptic function band rejection filter by using 3 dielectric resonators with 4 additional capacitors and 2 inductors. The receiving filter is designed by using 4 dielectric resonators(4 parallel resonance poles) with 5 additional capacitors which give additional series resonances.
Designed results of the transmitting and receiving filters, respectively, yield -42dB and -53dB attenuation in their rejection bands. They are implemented in the printed circuit boad of 23×14 ㎟ area and yield -40dB and -46dB attenuation in their respective rejection band which satisfy the required specification including requirements such as center frequencies, bandwidth, insertion loss, ripple, and VSWR.
