Development of a calculator for Edge and Parallel Coupled Microstrip band pass filters

Abstract

This paper presents an implemented calculator tool for the design of Edge/ Parallel Coupled Microstrip Band Pass Filters (PCMBPF) that makes use of the MA TLAB software. This calculator allows estimating both the parameters required for the design of the PCMBPF and the electrical response which is obtained by means of the equivalent circuit of this type of filters. Based on the transmission line theory approach (TLTA), the calculator herein proposed is a good solution to simply obtain the design parameters of this type of filters given that all formulas required for the PCMBPF design are programmed using close-form mathematic expressions and the coupling matrix concept. In order to validate our calculator performance, we implemented the proposed filter in a commercial electromagnetic simulator CST MWs that considers a set of electromagnetic effects, and accurately determine the final filter design. Secondly, we compared these simulation outcomes with the measurement results, achieving a reasonable agreement.

Design of compact wideband multi‐band and ultrawideband band pass filters based on coupled half wave resonators with reduced coupling gap

“…In Section 2.2, we detail the basic design of a two-pole parallel coupled band pass filter centred at 5.78 GHz. In Section 2.3 we optimise the previous design with an optimisation tool [10,11]. In Section 2.4 we show the dual-band and UWB responses obtained by applying small or null coupling gap.…”

“…The filter designed in the initial step can be optimised to improve the MB feature of the filter response, the insertion loss, the rejection between bands and the stopband. The optimal filter design was accomplished by using a previously developed parameter optimisation tool [10,11], which adjusts the physical dimension values for an optimised fitting of the S-parameters, insertion and return loss. Once obtained the optimised design, the simulation of its electrical response was performed with the electromagnetic simulator software CST.…”

“…Once obtained the optimised design, the simulation of its electrical response was performed with the electromagnetic simulator software CST. The theoretical analysis regarding the design to understand details such as the control resonant frequency of each band tool, the number of the poles for each pass band, and the rejection between bands can be found in [10][11][12][13]. Fig.…”

“…For the filter designed in Section 2.3, Table 1 shows the variation of the FBW for different values of the coupling gaps S 1-3 and S 2 . The FBW was achieved by calculating ABCD and S matrixes indicated in [11]. It can be observed that by decreasing the values of both coupling gaps, S 1-3 and S 2 , the even impedance characteristic Z 0e increases and its related value for odd-mode Z 0o decreases, hence leading to a larger value of FBW.…”

“…Evenand odd-mode characteristic impedances of parallel-coupled half-wave resonators are computed using admittance inverters. These even-and odd-mode impedances are then used to compute physical dimensions of the filter, as described in [10,11]. The expressions for the coupled line parameters, such as space-gap between lines, line widths and lengths, can be found in classical microwave books [4,5].…”