Double-passband micro-strip filter

Abstract

The invention relates to a double-passband micro-strip filter, which comprises two groups of first sub micro-strip filters and second sub micro-strip filters which are different in structure, an input coupled feeder line and an output coupled feeder line. The input coupled feeder line is respectively coupled with the first sub micro-strip filters and the second sub micro-strip filters, and the output coupled feeder line is respectively coupled with the first sub micro-strip filters and the second sub micro-strip filters. Compared with the prior art, the center frequencies, the band widths and the in-band properties of two pass bands of the double-passband micro-strip filter provided by the invention all can be regulated independently, and the distance between the two pass bands can be regulated in a quite large range, so that the micro-strip filter provided by the invention can meet a smaller attenuation band width between the two pass bands.

Description

technical field [0001] The invention relates to a filter applied in a wireless communication system, in particular to a double-passband microstrip filter. Background technique [0002] As the front-end equipment of the wireless communication system, there is an urgent need for high selectivity, small size, low cost, and flexible design of RF filters for efficient spectrum utilization. Today's communication systems require simultaneous work in multiple communication frequency bands to save costs, that is, multi-passband low-cost filters have become indispensable devices in these systems. The microstrip filter has an absolute advantage in low cost. Therefore, the dual-passband microstrip filter has also been extensively studied in the industry, such as filters based on SIR dual-passband resonators. [0003] see figure 1 , which is a structural schematic diagram of a SIR dual-passband microstrip filter in the prior art. The dual-pass band microstrip filter 10 includes a fir...

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Problems solved by technology

but figure 1 The frequency band that can be achieved by the design of the SIR dual-passband microstrip filter shown can only realize the situation that the distance between the two passbands is far away. The stopband between the two passbands is generally 40%, and the center frequency of the two passbands is The ratio is 2, and the relative bandwidth of the passband is more than 10%, and the order is higher, the size is larger, and the insertion loss is larger

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