Microstrip dual-mode filter with features of wide stop band and low spurious

Abstract

The invention relates to a microstrip dual-mode filter with the features of wide stop band and low spurious, which is produced on a microstrip medium substrate, an L-shaped coupling structure (2) of an input port and the L-shaped coupling structure (4) of an output port are respectively positioned on the outer sides of a diagonal of an SIR square ring resonator (1), the two ends of a microstrip connecting line (3) are respectively connected with the adjacent L-shaped coupling structure (2) of the input port and the other L-shaped coupling structure (4) of the output port, the non-adjacent L-shaped coupling structure (2) of the input port and the L-shaped coupling structure (4) of the output port are respectively connected with a 50-ohm input and output feeder (6), and a perturbation element (5) is positioned on an inner angle of the SIR square ring resonator (1). The microstrip dual-mode filter can obtain the larger port coupling amount in comparison with the traditional microstrip andfurther reduce the insertion loss. Meanwhile, the special coupling structure of the filter can very effectively suppress the parasitic spurious response and increase the stop band width. In addition,the filter has simple structure, is easy to realize the large-scale manufacture and is especially applicable to the design of radio frequency front end of mobile communication.

Description

technical field [0001] The invention can be applied to the radio frequency front end of the mobile communication system, can significantly increase the out-of-band spurious suppression degree and stop band width of the system, and maintain low insertion loss in the pass band, and is a high-performance microwave band pass filter. Background technique [0002] The modern mobile communication technology system puts forward higher and higher requirements on the performance of the radio frequency front end, and the filter at the front end of the radio frequency affects the transmission power and signal-to-noise ratio of the system to a large extent. Microstrip dual-mode filters have attracted much attention due to their low cost, easy processing and flexible implementation. Due to its own double-tuning characteristics, the volume is halved compared to filters of the same order. However, the insertion loss of ordinary microstrip dual-mode filters is large, and its inherent second...

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Problems solved by technology

However, the first technique will reduce the bandwidth of the filter, while the latter two will introduce additional structures, which will not only increase the circuit scale, but also deteriorate the transmission characteristics in the passband and increase the insertion loss.

In another technology, two double-film resonators are cascaded with a microstrip line to form a high-order filter, but the microstrip line and the coupling structure connected to it will cause additional spurious responses and deteriorate the frequency response characteristics inside and outside the passband.

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