Research On Ultra-Wideband Multi-Polarization Feeding Networks

With the rapid development of wireless technology, broadband multi-polarization antenna feeding is widely applied in the satellite communication, Massive MIMO technology, radar, GPS, electronic countermeasures, radio astronomy and so on. Modern communication systems. Miniaturization, bandwidth broadening and insertion loss reduction have been hot spots in the industry today. This thesis focuses on the ultra-wideband multi-polarization feeding networks. This thesis is organized as follows:1. The multilayer broadside coupling structure is studied. Based on the classic triangular coupling patch calculation method, an improved calculation method with a better coupling factor is presented and verified by simulation. Two improved calculation methods for the elliptical coupler are compared with the classic method. With one of the two methods, a multi-sectional 3 dB directional coupler working at 2.1-13.3 GHz is designed. A UWB coplanar waveguide 3 dB coupler operating at 2.3 to 18 GHz is designed and simulated, with the insertion loss less than 2 dB, the phase ripple less than 6 degree, the return loss and isolation better than 17 dB. A curve is developed to show the relationship between the coupling dimensions and coupling factor.2. Two kinds of phase shifter operating at 2.5-8 GHz are built and simulated based on the broadside coupling theory to fulfill the 45 degree and 90 degree phase shift. The phase ripple of the 45 degree phase shifter is less than 5 degree, and the insertion loss is less than 0.8 dB. The phase ripple of the 90 degree phase shifter is less than 10 degree, and the insertion loss is less than 0.8 dB. The UWB comparator is determined to be a cascade structure of the 90 degree phase shift and the UWB 3 dB coupler with a more compact structure and a lower insertion loss. Then, the comparator is implemented and measured. According to the measurement results, the isolation between the sum port and the difference port is better than 13 dB, and the insertion loss is less than 1.6 dB. Several improvements are raised and discussed.3. The multi-polarization feeding network is designed, which can achieve the horizontal/vertical polarization, circular polarization and 45 degree linear polarization. Two schemes are demonstrated, of which the difference is the way of phase shifting. With the CPW coupler in Chapter 3, a multi-sectional Wilkinson power divider, a SP4T switch and a low noise amplifier, the feeding network can fulfill the horizontal/vertical polarization, circular polarization and 45° linear polarization by a MCU controller at the 2 to 18 GHz. According to the measurements of output gain, an amplitude equalizer is designed and applied to improve the gain ripple by 3.6 dB at the operating band.