Design of UHF Harmonic Butterworth Low Pass Filter For Portable 2 ways-Radio

Abstracts-This paper presents the design of a compact Butterworth low pass filter designed operating at frequency range of 300-400MHz with input and output impedance of 50 ohm have been designed, simulated and fabricated. This filter is used to attenuate harmonic that generated by power amplifier to prevent from radiating out through the antenna. The filter’s circuits were first simulated using Advanced Design Software (ADS) to obtain the best filter characteristic based on S-parameter to see whether they met the specification for two way radio or not using the tuning and optimization features in ADS. From the measured results obtained from the fabricated filter, it is found that the performance of the filters do not satisfied according to the design specification value requirements. Comparing with the simulated circuits using ADS simulation software, the measured value also do not match. There many factors that influenced the results. This resulting the all the hardware measurement result low pass filter on each Sparameter show are not ideal as compared with the software simulation. The ADS based design has been prototyped and tested. Some optimization has been performed to improve the radio performance. Keywords-Butterworth Filter, S-parameter, Harmonic filter, RF Communication, Maximally Flat