3db double-branch directional coupler based on interdigitated structure

Abstract

The invention discloses a 3dB (dual-branch) directional coupler based on a cross-finger structure. The 3dB directional coupler comprises a main line, a subline, a first branch line and a second branch line, wherein the two ends of the main line are respectively provided with a first port and a second port, and the two ends of the subline are respectively provided with a third port and a fourth port. The 3dB directional coupler is characterized in that the main line, the subline, the first branch line and the second branch line are respectively composed of the cross-finger structure and residual parts at the two ends of the cross- finger structure; the outer sides of the residual parts of the main line are provided with main line resistance adjusting parts, and the outer sides of the residual parts of the subline are provided with subline resistance adjusting parts; the size of the coupler is reduced due to the slow wave characteristic of the cross-finger structure, and the coupler hasstable insertion loss close to the insertion loss of a common microstrip line within a wide waveband due to the lowpass characteristic of the transverse cross-finger structure, therefore, the cross-finger structure is used for replacing the common microstrip line so as to ensure the steadiness of the high band characteristic, and the defect in the prior art is overcome.

Description

technical field [0001] The present invention relates to a 3dB double-branch directional coupler; more specifically, it relates to a 3dB double-branch directional coupler based on an interdigitated structure. Due to the intervening of the interdigitated structure, the coupler can ensure that the characteristics remain unchanged. The occupied area is reduced. Background technique [0002] With the development of mobile communication technology and satellite communication technology, in order to facilitate portability and mobility, the miniaturization of communication equipment is the future development trend. The frequency band used by mobile communication is in the microwave range, so realizing the miniaturization of microwave circuits has important research value not only in practical aspects, but also in academic aspects. Branch line directional couplers are widely used in microwave integrated circuits and monolithic integrated circuits as power dividers, mixers, power com...

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Problems solved by technology

[0003] In the prior art, in 1997, people such as Iwata Sakagami published a paper "A Reduced Branch-line Coupler With Eight Stubs (a kind of small branch-line coupler with eight branches)" at the Asia-Pacific Microwave Conference, and proposed a A branch coupler with eight branch microstrip lines realizes miniaturization. The center frequency of the coupler is 500MHz. It has the same characteristics as the traditional coupler in the low frequency band, but there are differences in the high frequency band. Therefore, this improvement method only works for low frequency bands

In 2008, Ji Shengbao and Zhang Shaozhou published the paper "Microwave 3dB Microstrip Dual-Branch Directional Coupler Miniaturization" in Radio Engineering Volume 38, Issue 4. The standard 3dB microstrip dual-branch directional coupler was miniaturized by the method of opening the line. The working frequency of this coupler is 2GHz. Compared with the S-parameter characteristic curve of the standard 3dB double-branch directional coupler, the S-parameter characteristic curve is consistent at the low frequency and center frequency, but at the high frequency part S21 and S31 attenuate Very serious

It can be seen that although the above two methods have achieved the effect of reducing the size, they have brought about the attenuation of the high frequency part.

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