Research On The High-Performance Microstrip Differential Antenna

Differential technology is widely used in the radio frequency (RF) front-end products to improve the anti-interference ability of the communication system. However, traditional antennas with single port cannot be applied to the differential system directly. Balun is essential to realize the conversion between differential signals and single-ended signals. The use of balun is not conducive to the integration of antennas. In addition, the losses introduced by balun will reduce the signal transmission efficiency. Compared with the traditional single-ported antennas, differential antennas can be efficiently integrated in transceiver, systems without using baluns. Besides, differential antennas with symmetrical structures have the advantages of low cross polarization and stable and symmetrical radiation patterns, which effectively enhances the efficiency and stability of receiving and transmitting antennas.In this thesis, dual-band and miniaturized differential antennas are studied. Firstly, a dual band out-of-phase power divider, providing differential signals to dual band or broadband differential antennas, is proposed. Secondly, a dual band microstrip differential antenna with bandwidth enhancement is presented. Finally, a miniaturized differential antenna with U-slots is provided. Main works and innovative achievements in this thesis are as follows:(1) An impedance-transforming dual band out-of-phase power divider is provided. The use of double-sided parallel-strip line with inserted conductor plane can provide high stability of180°phase difference in a broad band. Hence, the proposed dual band out-of-phase power divider can feed dual band or broadband antennas by converting the dual band or broadband single-ended signals to differential signals.(2) A dual band differential antenna with bandwidth enhancement is proposed. This antenna achieved dual frequency operations by applying U-slots in the two edges of the radiation patch. The proposed antenna is fed through coupling by two I-shaped metal blocks to introduce the distributed capacitance, which can broaden the bandwidth in the higher resonant frequency.(3) A compact differential antenna with U-slots is presented. The size of the proposed antenna is only0.2λ0, where λ0is the wave length of the resonate frequency at free space. The proposed antenna radiates through the U-slots fed by the coplanar waveguide. The impedance matching between the proposed antenna and the feeder line can be realized by adjusting the length of the coplanar waveguide. The manufacture process of the antenna is easy, and the cost is low because of the single layer structure of the proposed antenna.