Research On Microwave Broadband Detector Logarithmic Video Amplifier

All the countries are putting great efforts into improving their battlefield combat capability in order to enhance security and self-protection. In the meantime, increasingly higher standards are set for electronic reconnaissance system performance with the development of electronic warfare technology and against the background of complex electronic reconnaissance environment. We can design high performance antennas and antenna array, as well as rational microwave front end to provide high sensitivity, wide dynamic range, high signal to noise ratio and improve receiver sensitivity and accuracy of frequency measurement for the back-end receivers. DLVA is mainly used for detection applications of power or pulse, and it can compress a large dynamic range input into a smaller dynamic range of the output video voltage, which is proportional to the input RF power. DLVA plays an indispensable role in the current radar, communications and electronic warfare systems and many other areas. Because simple detector cannot be broadband, or have a large dynamic range and high sensitivity, a variety of circuit configurations emerge to make up for this defect. Although the receiver’s sensitivity of direct detection is about 40 dB lower than the superheterodyne’s, it does not need a mixing module or local oscillator, and boosts the advantage of simple structure, high reliability and low noise. The method proposed in this thesis is dual-channel direct detection, which includes limiter, power divider, amplifiers, detector, amplifier, logarithmic amplifiers and other low-frequency components.The basic function of DLVA is to detect the high frequency signal from antenna to the low frequency signal which is easy to handle for logarithmic amplifier. Difficulty of this project is also here: realize a detector logarithmic video amplifier of K-Ka-band, with 60 dB dynamic range, the receiver sensitivity of-55 dBm and 1W anti-burning power in the cavity of 80×30×10mm3.Firstly, this article describes the history and the development process of the alarm detector machine and the status of DLVA; Secondly, the topology and performance of two kinds of receiver(superheterodyne and direct detection) are analyzed; Lastly, the structure of direct detection is adopted and we analyze two direct detection types and adopt the dual-channel direct detection scheme. An appropriate chip is selected based on the chosen structures and requirements of systems, and then the program’s feasibility is verified by overall comprehensive link simulation in ADS. The limiter and detector is designed by ADS according to indicators of each module circuits, and the che1270 detector is fabricated separately and tested. Finally, the modules are integrated into a cavity, and joint commissioning is conducted after adding the circuit of bias voltage, timing and low-frequency logarithmic amplifier. The overall system performance is tested, and the results are recorded and analyzed.After the overall circuit debugging and improvement, the final test results show that the system input VSWR is less than 3, and TSS is-57 dBm, with 60 dB dynamic range; the logarithmic slope is between 70~120mV/dB; the background voltage noise is less than 100 mV; and the test data basically meets the requirements of the project.