Improvement of low pass and band pass filter characteristics using Cross-DGS-resonators, logarithmic series and coupling matrix methods

A new method to improve the filter features and to control the results of the LPF using Cross defected ground structure (CDGS) and logarithmic method is proposed in this work. The etched DGS topologies on the ground plane as well as its coupling provide the slow-wave characteristics [1, 2. In order to control the operate frequency range of the filter and its results, the Chebyshev's rule, suspended Layer's technique first order and logarithmic method are employed. The proposed filters are partially measured, simulated, optimized and compared. The lowpass filters designed at cutoff frequency of 2.0GHz/3GHz/4.5GHz, which are suitable for GSM900, radar and wireless local area network applications. The proposed filters have low insertion loss, high return loss in the passband and wide stopband as well as very sharp roll-off characteristics for near pass-band. The proposed topologies are designed, optimized and simulated on RO4003 substrate using AWR software. The measurements show good consistency with the simulations. The minor discrepancy between both results can be attributed to the unexpected tolerance of the manufacturing process and reflections from the SMA connectors.