Balanced RF Electrically Tunable Bandpass Filter with Constant Relative Bandwidth

Abstract

The invention discloses a balanced radio frequency electrically tunable bandpass filter with constant relative bandwidth. The bandpass filter consists of an upper-layer microstrip structure, a middle-layer dielectric substrate, and a lower-layer grounded metal. The upper-layer microstrip structure is a balanced circuit, and comprises four half-wavelength resonators, two input feed networks, two output feed networks, two input ports and two output ports; the four half-wavelength resonators respectively consist of microstrip lines and variable capacitance diodes connected at two ends; the middle of the first half-wavelength resonator is connected with a capacitor and a microstrip line; the middle of the third half-wavelength resonator is connected with a capacitor; the second and fourth half-wavelength resonators are bent and symmetrical vertically; and the whole filter structure is in vertical mirror symmetry. The balanced radio frequency electrically tunable bandpass filter realizes constant relative bandwidth when a center frequency is tuned, can inhibit common-mode interference and can be used for a reconfigurable radio frequency front end for wireless communication.

Description

technical field [0001] The invention relates to a balanced radio frequency electronically adjustable band-pass filter with adjustable center frequency, in particular to a balanced radio frequency electronically adjustable bandpass filter with constant relative bandwidth that can be applied in multi-band, wide-band and reconfigurable radio frequency front-end systems pass filter. Background technique [0002] Modern ultra-wideband radar and wireless communications require high-performance reconfigurable RF front-ends. For example, in the cognitive radio system, in order to fully utilize and integrate various wireless channels and standards, the RF front-end needs to work at different frequencies, which requires a reconfigurable RF front-end with tunable center frequency. As an important part of the reconfigurable RF front-end, RF electronically tuned band-pass filters are receiving increasing attention. In this regard, there have been some research reports, and a variety of...

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Problems solved by technology

[0005] (2) Interference from environmental noise around the system

So far there is no research report on balanced RF electrically tunable filters with relative bandwidth control and common-mode rejection characteristics

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