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Sun Shi-Cheng(孙世成) a)b) , Sun Gui-Xun(孙贵训) a) , Jiang Zhong-Hao(江忠浩) a) † , Ji Chang-Tao(季长涛) b) ‡ , Liu Jia-An(刘家安) a) , and Lian Jian-She(连建设) a) a)

Abstract-This paper presents differential-fed patch antennas with excellent cross-polarization. This paper provides a detailed graphic illustration of factors that lead to deteriorated H-plane crosspolarization by the conventional single-ended feeding probes. A novel differential rat-race feeding structure was constructed to allow easy impedance matching. An experimental antenna was realized on lowtemperature co-fired ceramic (LTCC) at 8 GHz. An excellent crosspolarization of less than −22.5 dB was achieved. When the operation frequency is high, the parasitic inductance caused by feeding probes may degrade the performance of antennas. This paper further proposes the use of differential aperture-coupled structures at high frequencies. An aperture-coupled antenna realized at 40 GHz with low crosspolarization < −15 dB has been achieved.

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This letter presents a wideband patch antenna on a low-temperature cofired ceramic substrate for Local Multipoint Distribution Service band applications. Conventional rectangular patch antennas have a narrow bandwidth. The proposed via-wall structure enhances the electric field coupling between the stacked patches to achieve wideband characteristics. We designed sameside and opposite-side feeding configurations and report on the fabrication of an experimental 28-GHz antenna used to validate the design concept. Measurements correlate well with the simulation results, achieving a 10-dB impedance bandwidth of 25.4% (23.4-30.2 GHz). Index Terms-Local Multipoint Distribution Service (LMDS)antenna, low-temperature cofired ceramic (LTCC) patch antenna, stacked patch, via-wall structure, wideband patch antenna.