LTCC Differential-Fed Patch Antennas With Rat-Race Feeding Structures

This paper presents difierential-fed patch antennas with excellent cross-polarization. This paper provides a detailed graphic illustration of factors that lead to deteriorated H-plane cross- polarization by the conventional single-ended feeding probes. A novel difierential rat-race feeding structure was constructed to allow easy impedance matching. An experimental antenna was realized on low- temperature co-flred ceramic (LTCC) at 8GHz. An excellent cross- polarization of less than i22:5dB 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 difierential aperture-coupled structures at high frequencies. An aperture-coupled antenna realized at 40GHz with low cross- polarization < i15dB has been achieved.