Ultra-wideband bandpass filter on coplanar waveguide: Proposal and implementation

Abstract

In this paper, a novel ultra-wideband (UWB: 3.1~10.6 GHz) bandpass filter on coplanar waveguide (CPW) is presented, designed and implemented. At first, an openended nonuniform or multiple-mode resonator with three distinctive sections is constructed and investigated toward generating the first three resonant modes occurring around the lower-end, center, and higher-end of the UWB band. Then, a CPW interdigital capacitor element with enlarged ground-to-ground distance is characterized to excite two additional resonant poles below and above the UWB's center. As a result, a five-pole UWB bandpass filter with only one full-wavelength is constituted. Its performance is studied on the basis of a simple cascaded transmission-line network, whose parameters are extracted from our selfcalibrated method of moments. After the optimized results are confirmed by full-wave simulation over the filter layout, a UWB filter sample is fabricated to demonstrate the actual UWB passband behavior with the 2.8-10.2 GHz bandwidth, where the insertion loss is less than 1.5 dB and variation in group delay is less than 0.33 ns. V V C 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE 17: 225-232, 2007.

Coplanar-Waveguide Ultra-Wideband Bandpass Filter Based on Interdigital Structure

“…Additionally, all the slots are symmetrically etched at the both sides of the input/output CPW center strip. It is obvious that the proposed filter bears merits such as good performance, concise procedure, easy fabrication and integration, compared to the reference [4][5][6][7][8][9][10][11][12]. …”

“…However bonding wires to connect the split strips of the resonator make it difficult to process and integrate. The UWB bandpass filter which uses interdigital capacitor coupling to generate additional transmission poles is mentioned in [12] and achieves 110% passband.…”

“…The size of the bandpass filter which occupies only half one guided wavelength at 5.56 GHz is 2cm×3cm×0.635cm, and it is more compact than the filter size in [12]. Moreover, the fractional band width of the filter at center frequency reaches 150% and it has a steeper stopband.…”

A rectangular ring backed CPW UWB filter with notched band

“…Several CPW-based filters with broad/ ultra wide pass band have been designed and reported in the literature [6,[14][15][16][17]. Most of these UWB filters [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] could be used in actual systems, but the performance may degrade because of interference from signals of other communication systems like wireless local-area network (WLAN). Hence, researchers are making efforts to reject these bands to avoid interference [18][19][20].…”

“…Another useful technology is the CPW that offers distinct advantages over microstrip lines such as low radiation loss, low dispersion, and easy integration with the integrated circuits especially at higher microwave and millimeterwave frequencies [14]. Several CPW-based filters with broad/ ultra wide pass band have been designed and reported in the literature [6,[14][15][16][17]. Most of these UWB filters [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] could be used in actual systems, but the performance may degrade because of interference from signals of other communication systems like wireless local-area network (WLAN).…”