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Journal of the Korean Institute of Electromagnetic and Science 2001;1(1):83-87.
An RF Amplitude Equalizer ; Improved Passband Flatness of a Bandpass Filter
Hee-Yong Hwang1, Jung-Seong Jung2, Sang-won Yun3
1Dept. of Electric & Computer Eng., University of Maryland, College Park
2Microwave Lab, AMOTECH CO., LTD
3Dept. of Electronics Engineering, Sogang University
Abstract
Many communication systems require bandpass filters with sharp skirt frequency characteristics in order to avoid the interferencce, which results in more order in the filter design. However, because of the limited Q values bandpass filters made of small sized ceramic resonators suffer from relatively large ripples at the band edges as the order of the filter increases. In order to compensate the large ripples while maintaining the sharp skirt frequency we propose a new RF amplitude equalizer. The equalizer made of two pole bandpass filter and an amplifier whose amplitude characteristics are the reverse of those of the bandapss filter. At the cellular band 9-pole bandpass filter with 10 MHz bandwidth exhibits 3 dB ripple when 8mm*8mm ceramic coaxial resonators are used. We added the RF equalizer to this filter and the flatness is improved as less than 1 dB.
Key words: RF equalizer, amplitude equalizer, bandpass filter, quality factor, concave shape

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