| In the past decades,as an important part of modern wireless communication system,satellite communication has been widely used in human daily life and military life.With the advent and development of the 5G era and the growing demand for satellite communications,wireless communication systems are gradually developing toward high speed,high capacity,low latency and multi-function.With the successive launch of the three satellites of Tiantong-1,the applications and demands around the Tiantong S-band are increasing and have a wide application prospect.With its high gain and flexible beam scanning,phased array has many advantages when applied to satellite communication.Phased array has a wide demand in the aspects of miniaturization,low cost,wide band,and wide angle scanning,which are also the focus and difficulty of their research.In this paper,based on the Tiantong S-band,the relevant research is conducted around the phased array technology,and the specific work are as follows:A wide-beam antenna element is designed based on stacked microstrip antenna and aluminum cavity,the antenna bandwidth is expanded by the stacked structure of double radiation patch,and the introduction of an aluminum cavity expands the beam width of the antenna.The Wilkinson power divider is used as the feed network of the antenna,a circularly polarized wave with good purity can be obtained,and the impedance bandwidth and axial ratio bandwidth of the antenna can also be improved.This antenna element has a wide beamwidth at the center frequency point of the transmitting and receiving working band and has a low profile.Based on this antenna element,the4×4 planar phased array antenna is formed by rotating feed,at the center frequency point of transmitting and receiving band,simulation results show that the phased array antenna achieves ±60°scanning angle in two mutually perpendicular azimuths,and the gain is greater than 11 d Bi and the axial ratio is less than 3d B in the scanning angle range,which can maintain high gain and good circular polarization purity during scanning.A full-duplex phased array TR module is designed,in which the feed network is designed as a double-layer dielectric substrate structure,and the one-to-sixteen port power divider and sixteen-inone combiner are distributed on different dielectric substrates,which is an important basis for the TR module to work in full-duplex,and the S-parameter simulation results of both are good.The use of a large number of bare chips in TR module helps to miniaturize the module,and the use of traditional FR4 substrate helps to reduce cost.Conduct link simulation on a single transmitting and receiving branch,the simulation results show that the link gain of single transmitting branch is greater than28 d B,the output power is greater than 1W when the input power is 3d Bm,the saturated output power is greater than 2W,and the link gain of single receiving branch is greater than 30 d B and the noise factor is less than 3.5d B,which meets the design specifications.Finally,the overall circuit was designed,including the design of the power supply circuit,the PCB layout of the transmitting and receiving channel,and the overall PCB layout.A low-cost reflection-type tunable analog phase shifter is designed based on L-type load and three-branch directional coupler.The phase shift is enpanded by reducing the port impedance of the coupler pass-through and coupling ends,connecting a high-impedance microstrip line and a varactor diode in series in the reflective load,and expand the bandwidth of the phase shifter by using threebranch directional coupler.The measured results show that the maximum phase shift of the designed reflection-type analog phase shifter is 191°±1° in the uplink working band and 186°±0.1° in the downlink working band within the tuning voltage range of 15V～0V,and the return loss is greater than20 d B in both working bands,and the insertion loss is less than 3.3 d B,and the insertion loss fluctuation is less than 1 d B.The measured results and simulation results are in good agreement.The phase shifter has the features of simple structure,easy to tunable and low cost. |
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