Research Of Anti-burnout Techniques In The Front-end Of UWB Receiver

There is usually a high sensitivity low noise amplifier (LNA) located in the inputof Ultra Wide Band (UWB) receiver. High leakage power of the transmitted signalinside system as well as high-power interference signal from vicinity may lead burnoutof the core semiconductor device in LNA, resulting in the overall failure of the receiver,so improving the anti-burnout ability of receiver is significant in the overall design ofthe receiver. At present, domestic and foreign research has focused on the anteriorlimiters and posterior transistors. But the broadband large signal performance oftraditional limiter has deficiency and the anti-burnout design concepts of LNA circuitsneed to be further enriched and improved. Aiming at the above deficiencies, the thesisstudied the anti-burnout techniques of the front-end of ultra-wideband receiver from theperspective of circuit design, specifically contains the following two aspects:1. The quarter-wavelength line in the inter-stage of traditional limiter can’t fulfillthe requirement of UWB applications and has a large size in low frequency band.Aiming at the two shortcomings, this thesis designed a novel UWB limiter whichemployed a kind of low-pass broadband LC impedance transformation network. Thenetwork can transform the ultra low impedance of clean up limiter to high resistance ina relatively wide bandwidth under large signal level, thus effectively reducing the spikeleakage power and dimensions of the limiter. Besides, due to the filter characteristics ofthis LC network, the isolation of limier was increased notably.2. LNA is the most easily burned part of the UWB receiving front end, effectivelyimproving its anti-burnout capability is crucial to the anti-burnout performance of thewhole RF receiving front-end. At first, this paper analyzed the burnout mechanism ofcore device of LNA, the transistor. And then based on the burning mechanism of thedevice, clipper circuit was introduced to the design of LNA. The clipping diodes wereplaced in parallel with the gate of transistor, and absorbed into the input matchingcircuit of LNA. Finally, the influence of the characteristic impedance of seriesmicrostrip in input matching circuit on the anti-burnout performance of LNA wasdiscussed. The results of simulation and experiment proved that the introduction of the clipper circuit can significantly improve the anti-burnout ability of the UWB LNA.Due to the limitations of the existing experimental conditions, laboratory can notprovide a high power broadband source. To meet the requirements of anti-burnoutperformance test of limiter and LNA, a UWB PA was designed and had high-poweroutput within a specified bandwidth.Ultimately, on the basis of above contents,200-800MHz UWB limiter,200-800MHz UWB LNA, UWB PA and700MHz narrowband LNA was designed andimplemented. Via actually testing the limiter and LNA, the anti-burnout design conceptsof UWB receiving front end were verified.