New Design Technique for Wide Band Pass Filters using Direct Frequency Conversion Design Method

In this paper, a new design technique called the direct frequency conversion method is proposed, for wideband pass filters, which can be applied to the UWB (ultra wide band) system. Using the proposed method, a wide band-pass filter is designed as an equivalent circuit, composed of parallel and serial L-C resonators. In the equivalent circuit, a microstrip line and a suspended stripline (SS) are adopted to implement short-and open-stubs of the parallel L-C resonator. Distributed models for the inductor and the capacitor are used to implement the series L-C resonator. The proposed filter is designed so that the attenuation characteristic is better than -30 dB in the range of DC~1.4 GHz and 6.6-20 GHz, and lower than -60 dB in the range of 7.2-20 GHz. The low-pass filter is connected to the wide band-pass filter, in order to obtain a flat band stop characteristic that is lower than -60 dB at 20 GHz and above. The very low insertion loss and excellent attenuation rejection characteristics are remarkable aspects of the proposed design. The measured data agree well with predictions.