Research And Design Of Differential SIW Antenna And Array With High Common-mode Rejection

With the rapid development of modern wireless communication systems,higher requirements have been placed on the integration and miniaturization of RF front-ends.The differential circuit is attractive due to its high immunity from crosstalk and common-mode(CM)noise,high linearity and large dynamic range,etc.Thus,RF front-end circuits are often implemented using differential technology.However,traditional single-ended antennas often require baluns to interface with differential circuits.This will not only reduce the integration of the system,but also generate unnecessary losses.The differential antennas can also be directly connected to differential circuit without introducing a balun,which have two feed ports.At the same time,although the RF front-end differential circuit has the ability to suppress common-mode noise,external noise is still fed into the antenna in the form of a common-mode signal with the differential-mode signal,which affects the communication quality.Therefore,the differential antenna with high CM rejection has become a new research hotspot.On the other hand,substrate integrated waveguide(SIW)technology has the advantages of low profile,low insertion loss,high power capacity,easy integration,and has gradually become the first choice in microwave millimeter wave communication device design.Therefore,this paper analyzes the differential transmission characteristics and balun characteristics of SIW.On this basis,the differential SIW tapered slot antenna and slot antenna array with high common-mode rejection are designed.Meanwhile,a differential SIW filtering antenna with common-mode rejection is also designed based on the half-mode radiation cavity.The specific work and innovation of this paper are summarized as follows:1.According to the transmission characteristics and E-field distribution of the SIW,the differential transmission characteristics and inherent common-mode rejection characteristics are analyzed and studied.On this basis,a multi-layer differential SIW horn antenna with microstrip feed is designed.According to the PEC/PMC mixed boundary conditions,the transmission of the common-mode signal is effectively prevented by the slot in the middle ground,and the radiation terminal is added with the materials with high dielectric constant which can achieve wide-band impedance matching and good radiation characteristics.2.Utilizing the differential transmission characteristics of SIW,the coaxial-SIW and microstrip-SIW differential feed structures were designed.Based on these two structures,differential SIW tapered slot antenna with high common-mode rejection were proposed,in which the rectangular ripple structure is adopted to effectively reduce the cross polarization and side lobe level.On this basis,four-way T-type differential power dividers are designed to feed the tapered slot antenna elements,and a differential SIW tapered slot antenna array with high common-mode rejection characteristics is designed.Finally,the above antenna and array are implemented and fabricated,and the measured results agree well with simulated ones.3.Based on the analysis and research of the balun characteristics,a 1×4 differential SIW slot antenna array is designed by analyzing and simulating several key parameters.In order to meet the requirements of higher radiation performance,a 4×4 differential SIW slot array with common-mode rejection is designed based on T-type power divider by adjusting the power distribution and phase arrangement reasonably.Finally,the antenna array is implemented and fabricated,and the measured results agree well with simulated ones.4.The SIW differential transmission characteristics are applied to the filtering antenna design of cavity structure.A high common-mode rejection differential SIW filtering antenna is designed based on the half-mode radiation cavity.The impedance matching and radiation characteristics of the antenna are effectively improved by loading periodic metal patches on the terminal.At the same time,a coplanar waveguide structure is formed by etching parallel slots on the back,and multiple coupling paths are introduced to generate two gain zeros on the upper and lower edges of the passband by means of cross-coupling,thus achieving high selectivity.