Design Of Micro Video Transmitter

Instantaneity and all-sidedness of the information are the most important in the modernized war. Eyes– the most direct-viewing, most common way to gain the information; Reducing the casualties has more and more vital significance in the modernized war. The micro video transmission system comes into being, which can satisfy the requirement to gain the information in the war and don't expose easily. And it also can do the response quickly in the complex war. In theoretical, it can achieve non- casualty. Comparing with the way of getting the information by the soldier, that by the micro video transmission system is more prompt, less cost and risk.This thesis compared two plans: analog and digital video transmission program. Digital transmission program have a bottlenecks in transition speed. If an additional video compression IC is added, total costs will increase; and the circuit size and power consumption will increase at same time. By comparison, FM transmitter has some advantages, such as long transmission distance, good noise restraint ability. Therefore, this thesis has chosen the FM video transmission plan.The colorful elements of video signal concentrate in the high-frequency part. So, this thesis set up an pre-emphasis networks for the video signal input unit. This thesis give the pre-emphasis network's transmission characteristic. The simulation showed that the high frequency components of video signal essentially the same, low-frequency component is significantly restrained. With the de-emphasis unit of the receiver, we can improve signal noise ratio of the entire video transmission system.In order to precisely control the frequency, the system used PLL FM mode. MAX2754 program used as a VCO, MC12022 as a pre-scalar, ML145152 as Synthesizer, use integrated operational amplifier LM358 to do an active low-pass filter, a voltage-controlled oscillation direct approach launch FM analog video signals.According to tuner curve in MAX2754's datasheet, the gain around 1.2 GHz has been calculated in this thesis. Gains of ML145152, MC12022 and VCO have been calculated. The equally integral model has been simulated in this thesis.According to the external crystal of Synthesizer, ratio of dual-mode pre-scalar and the set of transmitter's center frequency, the N counter and A counter's value has been calculated..The LPF is the important part of PLL design. This problem has been discussed in detailed in this thesis. This thesis has discussed how to enter the RC parameters.Loop filter's transmission characteristics have been simulated. The phase and gain characteristics have been discussed in this thesis. Specific hardware circuits used LM358 a PI filters. Thesis also gives the whole PLL characteristic of the open-loop and closed-loop characteristic curves.PCB layout is presented in this thesis according to schematic circuit. The input and output impedance matching issues have been discussed. The two stages settings and the bias impedance matching method have been discussed. This thesis use 1 mm FR-4 material, this is a common board material. Dielectric constant between 4.0-4.3; and the thinner the board is conducive to some of the power amplifier Chip cooling, so this option can satisfy the needs of thermal and dielectric constant.In order to reduce the size of transmitter has been chosen plate package capacitors and inductors (0402) in this thesis. System uses a 3.7 V lithium battery-powered, increased power and the stability of portable performance. In order to avoid electromagnetic interference, the analog ground and digital ground has been separated, and linked together in power place.The actual size of circuit boards is 5.5×7.5cm, after the assembly components total weight is 50 g. The work frequency is 1.2 GHz. From the spectrum of the circuit we can found an obvious power output, output frequency is stable.Using this transmitter transmit video signal, the 1.2 GHz FM receivers, the signal is received and display on television. This transmitter can achieve 1.2 GHz wireless transmission of video.This design of video transmitters can be widely applied to the Border Patrol, natural disaster surveillance, detection, such as topography, with very great military significance and practical application value.