Miniature Wireless Video Transmission System Design And Realization

With the development of information technology and the highly integrated circuit, the current trend of wireless video transmission system is to reduce size. Mini-type wireless video transmission system not only can be used in military small-area battlefield scout, but also have great application foreground in different kinds of field, for example in traffic monitoring, disaster detecting and terrain reconnaissance. The main purpose of this paper is to design a wireless video transmission system which is miniature and low energy cost.After briefly introducing the correlated technical basis of analog wireless video transmission system, the paper mainly focuses on the theory of oscillator and PLL(Phase Lock Loop). Aiming to achieve mini-type designment, and transmitting farther on the setting frequency band, direct frequency modulation is chosen after comparing the advantage of amplitude modulation with that of frequency modulation. This paper realized frequency modulation using the video signal to directly control the resonance loop's diode of the VCO at the early stages, and then through using radio frequency Bipolar Junction Transistor, designed a LC voltage controlled oscillator which was emulated by Advance Design System. In addition, it also implemented the design and debugged the hardware circuit. As the experiment results show, multiple reasons led to the offset of oscillating frequency, including diode's nonlinear characteristic, fluctuation of electrical source voltage, traction of load impedance, change of environmental temperature and humidity and the design of circuit. Based on the experience, this thesis adopts PLL to realize wireless video transmission, which can stabilize the center frequency, reduce the frequency offset and enhance the stabilization of system. The frequency modulation range is 1145MHz to 1250MHz, and the frequency step is 80KHz.This paper presents the general project design firstly, and then introduces the system hardware circuit design in detail which includes the choice of chips, the loop filter parameters computation and the design of the power amplifier's peripheral matching circuit. As the experiment results show, the problem of center frequency offset...