Miniaturized Micro-Strip Band-Pass Filters

The increasing applications of Global Navigation Satellite Systems(GNSS) has led to focused attention on improving the performance of RF communication systems. Towards this end, low-power and low-cost BPFs are being designed and developed. The fabrication of the popularly deployed high-Q SAW filters is fairly complex, incurring high costs. Hence four alternative implementations using micro-strip PCB structures to meet desired specifications have been studied here. The first structure provides two passbands using microstrip lines, rectangular resonators and Stepped Impedance Resonator (SIR). The upper band of the suggested filter can be tuned without increasing the circuit size, which is one of its most remarkable advantages. In the second structure designed, microstrip antennas of square geometry are extended into a BPF. The third structure is a filter design based on parallel-coupled lines connected to transmission lines. The fourth structure is BPF implemented using a new and simple Defected Ground Structure (DGS). The asymmetric single S-shaped DGS is used to obtain the dual-band filter response. The structure is relatively much simpler than other DGSs that are presently used to obtain dual-band response. The analysis of these cost-effective designs show characteristics matching the SAW filter counterpart, exhibiting compact size, low insertion loss, sharp transition bands and high attenuation level in the stop-bands.