A Balanced-to-Unbalanced Filter Power Divider with Broadband Common-Mode Rejection

Abstract

The present invention proposes a balanced-to-unbalanced filter power splitter with wideband common-mode suppression, aiming to widen the common-mode suppression bandwidth of the balanced-to-unbalanced filter power splitter, so as to meet the requirements of high integration and strong anti-interference ability of microwave circuit systems , including a dielectric substrate, a metal base plate printed on the lower surface of the dielectric substrate, a U-shaped input microstrip line and a U-shaped output microstrip line printed on both sides of the axis BB' on the upper surface of the dielectric substrate with opposite opening directions; Four star-shaped impedance resonators are printed between the U-shaped input microstrip line and the U-shaped output microstrip line, and the adjacent impedance resonators are mirror-symmetrical about two vertical axes; the U-shaped output The microstrip line has a first matching branch connected to the bottom of the rectangular microstrip printed between its rectangular microstrip arms, and the free end of the first matching branch is connected with an isolation element; the folded microstrip line and the isolation element The free ends are respectively connected to the metal base plate through metallized via holes.

Description

technical field [0001] The invention belongs to the field of microwave and radio frequency technology, relates to a filter power divider, in particular to a balanced to unbalanced filter power divider with broadband common mode suppression, which can be applied to the radio frequency front end of a wireless communication system. Background technique [0002] The power divider has the function of power distribution. It can divide one signal into two or multiple signals. It is an important passive device in the wireless communication system. The filter can select the required frequency signal from many signals, and at the same time suppress the unnecessary frequency signal, which is an indispensable key device in the wireless communication system. Adding the filter function to the power splitter can greatly reduce the size of the RF front-end circuit and facilitate the integration of microwave systems, so the filter power splitter came into being. On the other hand, with the ...

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Problems solved by technology

[0003] At present, the design of balanced to unbalanced filter power dividers mostly uses the different impedance characteristics of half-wavelength or three-quarter-wavelength transmission lines in the transmission of differential-mode and common-mode signals to achieve the suppression of common-mode signals, but due to the dispersion of transmission lines Effect, so that the common mode rejection bandwidth is relatively narrow, which will greatly reduce the anti-interference performance of the balanced to unbalanced filter power splitter

For example, the application publication number is CN 107464978 A, and the patent application titled "balanced to unbalanced signal filter power splitter" discloses a balanced to unbalanced signal filter power splitter, the power splitter is between the balanced input port A half-wavelength transmission line is loaded between them to achieve good common-mode rejection in the working passband. At the same time, two half-wavelength transmission line resonators are used to achieve a good filtering effect in the passband, but in the working passband Also, common-mode signals cannot be rejected

As another example, the application publication number is CN 108417941 A, and the patent application titled "balanced-unbalanced filter power divider based on ring resonator" discloses a new type of balanced-unbalanced filter power divider based on ring resonator. The power divider is loaded with a three-quarter wavelength transmission line between the balanced input ports, and at the same time adopts a ring resonator structure to achieve a good filtering power division function. In a wide frequency band, high common mode rejection, but in the -4dB operating frequency range, the common mode rejection deteriorates to about -10dB, and the common mode rejection performance of the power splitter still needs to be improved

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