Balanced Broadband Tunable Common Mode Filter

Abstract

The invention discloses a balance type common-mode filter with adjustable broad band. The filter comprises a dielectric substrate, a first metal layer and a second metal layer, wherein the first metal layer is arranged on one surface of the dielectric substrate; a pair of differential microstrip transmission lines are arranged on the first metal layer; the second metal layer is arranged on the other surface of the dielectric substrate; the second metal layer is used as a grounding metal surface, and at least one groove line annular resonator is arranged on the second metal layer; each groove line annular resonator is formed by four groove lines in a surrounding manner, wherein the four groove lines are arranged on the second metal layer, connected in sequence, and distributed along the rectangular four sides; the differential microstrip transmission lines are in axial symmetry relative to a first straight line; the projections of the groove line annular resonators on the second metal layer are all in axial symmetry relative to the first straight line; and a variable capacitor is arranged between one group of opposite groove lines, parallel to the first straight line, of the groove line annular resonators separately. By implementation of the technical scheme of the filter, the common-mode stop band frequency of the balance type adjustable common-mode filter can be adjustable in a bidirectional way by controlling the capacitance values of the two viable capacitors loaded on the groove line annular resonators respectively so as to restrain the target common-mode signal.

Description

technical field [0001] The invention relates to the field of microwave technology, in particular to a balanced broadband adjustable common-mode filter. Background technique [0002] In modern mixed-signal systems, the differential structure is widely used in circuit design because of its inherent noise immunity, low crosstalk and low EMI characteristics. In practical circuits, common-mode noise due to sampling time lag or amplitude imbalance of signals along the differential path is unavoidable. Some tiny asymmetries in differential transmission lines can have a big impact on EMC and signal integrity in high-speed circuitry if not handled properly. Therefore, filters with wideband and deep common-mode noise rejection performance have attracted great attention in the design for transmission of high-speed differential signals. For example, in some non-planar circuit designs, there are common-mode filters designed using ferrite cores as the core components for common-mode sup...

AI Technical Summary

Problems solved by technology

But in order to be able to suppress common-mode noise signals over a wider frequency band, it is usually necessary to cascade multiple structures with the same / different size, which also leads to an increase in circuit size

However, in the design of these common-mode filters, frequency tunable technology and balanced common-mode filters have not been well combined, and the problem of how to design balanced common-mode filters with broadband tunable performance has not been clearly resolved. Program

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