Design And Realize Of Paroxysmal Microwave Transmitter In L Band

The microwave transmitter is an important part in modern wireless communication system. RF transmitters are widely used in systems such as wireless communication, satellite communication, measurement and control of missiles. They should have characters such as compact-structured, long-life, high-reliability, easy-to-maintenance etc. There are different requests for RF transmitters such as high-gain, high-efficiency, wide-band, large-capacity and others in engineering and practical aspect. GaAs semiconductor microwave components are widely used in L-band microwave systems now.The base knowledge of microwave transmitter designing is introduced in the first part of this paper, including the selection of mechanical structure, compositions and key technologies. And then, the working principles and technical requests of filters, mixers, power amplifiers are described in the second part. The thermal designing and structural designing technologies of microwave transmitters are described at the last.There are mainly three aspects in the designing of the microwave transmitter:IF circuit, mixer circuit and PA circuit. Many research and demonstration works have been performed by the author in the design course. Proper signal level must be assigned to every part of the RF transmitter to avoid self-excited oscillation and to ensure stability and high-efficiency. Simulation softwares such as AWR and ADS are used by the author to optimize the transmission gain, reflection loss, stability coefficient and other key specifications. The circuit diagrams and PCB are designed by the author with Protel. After all, every specification of the microwave transmitters is tested by microwave instruments in the laboratory and the test results are list in the paper.Finally, the gain of the RF transmitter is38dBm, the output power of1dB compression point is40dBm, the three order intermodulation coefficient is-27.2dBc. The RF transmitter achieves good linearity. The switch bias circuit of the RF transmitter can response very fast and has high ratio of switch which reduce the power consumption of the system and improve the power efficiency.After assembled in the working communication system, the stability, high-efficiency and high-power of the RF transmitter improve the communication distance. The outer-band-rejection ability of the RF transmitter improves the anti-interference performance of the whole system.