X-band Rf Front-end Transmitter Circuit Design

Microwave transceiver has been applied comprehensively in communication and electronic countermeasure, and missile guidance.Therefore,microwave transceiver has become an important research area because of its wide application.While designing RF front-end transmite circuits, the transmit signal's quality is the most important indicators of performance of RF transmitter, and there are two key technologies in the design of RF front-end transmite circuit: the technology of up conversion and local oscillator's design.This paper discusses the X-band RF front-end circuit design process, according to the technical requirements issues of the subject,and in conjunction with the circuit design of technical difficulties, and propose the corresponding solutions and finally complete the design of the circuit.After researching correlative theory particularly, we adopt a kind of new scheme of frequency conversion using single local oscillator to achieve double-conversion as the scheme of transmitter. It simplifies the realization of local oscillator and retains the advantages of traditional double-conversion system. At the same time, it greatly reduce the difficulty of the realization, and more flexible. In the scheme, two local oscillator are got by making frequency demultiplication to a phase-locked oscillator.Because of the high request of phase noise performance, local oscillator is always a key problem of communication system and has the direct influence of system. So, it is often realized by using frequency synthesis technology. Because of the harmonic wave and parasitic frequency composition which is hard to reject, direct frequency synthesis is usually not adopted. Despite being widely used, digital frequency synthesis has to face the problem of upper frequency limit and spur. Therefore, the frequency synthesizer works in microwave band is mostly designed and realized by the way of indirect phase lock frequency synthesis, based on specific integrated circuit. In the process of designing, noise model of phase locked loop (PLL) is analysed; component selection and design of submodule are also performed elaborately. Based on reduplicate hardware debugging, the transmitter possesses excellent phase noise capability at last and testing result is achieved at the same time.