The Research Of Key Techniques On Butler Matrix-Based Dual-Frequency Dual-Polarization Multi-Beam Antenna

Multi-beam antennas find wide application in wireless communication systems, and it is one of the most popular research directions to study dual-frequency dual-polarization multi-beam antennas. In this dissertation, for the application of the C-band wireless communication systems, several key techniques of dual-frequency dual-polarization multi-beam antenna systems are investigated based on the conventional planar circuit fabrication techniques. The detailed contents are as follows:1.A microstrip broadband Butler matrix is proposed and fabricated. A3-branch line wideband coupler with lumped and distributed elements is adopted in the design, which can reduce almost half area. To get good phase and transmission performances during a wide band, an improved Schiffman phase shifter is designed, which uses multi-U-shaped coupled-line instead of the single-U-shaped one. The simulated and measured results show that the bandwidth of the designed Butler matrix is20%.2. The directional coupler, double-side crossover and Schiffman phase shifters of Butler matrix are designed based on suspended stripline. The double-side coupled directional coupler and double-side crossover are capacitive loaded to implement phase velocity compensation, and the broadband performances are obtained. The simulated and measured results show that the designed Butler matrix is characteristic of low loss and good port consistency over the50%bandwidth, and it is compact and can be fabricated easily.3. A compact microstrip-feed dual-frequency dual-polarization rectangle patch antenna embedded a placard-shaped slot is proposed. By exciting the patch at an appropriate position using a single microstrip feed line, TM01and TM10modes are both excited, respectively, at the first and second resonant frequencies. By introducing two corner cuts, we can adjust the cross polarization levels with little influence on the resonant frequencies. The simulated and measured results show that the antenna unit has low cross polarization levels, a wider and easily adjusted frequency-ratio (FR) and a compact size, and it is readily used in array configurations.4.The high isolation diplexers are studied based on the dual behavior resonator (DBR) microstrip filter. The defected ground structure (DGS), spiral compact microstrip resonant cell (SCMRC), and dual-band stub (DBS) are introduced in, respectively, so the upper parasitic passbands are suppressed, and the rejection in the upper stopband could be improved without increasing the original size. The simulated and measured results of the three diplexers designed in this dissertation show that the isolations are better than65dB, and the losses are less than1.3dB.5. A folded stepped-impedance resonator (SIR) structure is proposed. By applying the proposed resonator, the compact band-pass filters (BPFs) of the diplexer are realized. With the adoption of SCMRC into the T-junction, the diplexer isolation is improved, and the size is reduced. The diplexer is very compact and occupies a small area of0.87λg×0.23λg, The simulated and measured results show that the isolations are better than65dB, and the losses are less than1.7dB.6. A Butler matrix-based multi-beam antenna is constructed using the broadband Butler matrix, the dual-frequency dual-polarization microstrip array and the diplexer. The beam switching network (SP4T) and the Rx/Tx are designed and fabricated. And an experiment was carried out to verify the idea.