| With the rapid development of electronic and communication technology,the operation frequency has reached into microwave,millimeter wave and THz frequency range.The main function of millimeter wave receiving front-end is frequency conversion and filtering in order to promote subsequent circuits' demodulation and amplification,which has become a hot area of research for experts and scholars at home and abroad.In addition to low noise amplifiers,mixers and detectors are also critical components in receivers.Simple structure,high reliability,compact size,low conversion loss and other superior performance have been the design goals for millimeter wave receiving components.Therefore,it is of great practical significance to develop a high sensitivity detector and a low conversion loss mixer.Based on current technological condition,a W-band broadband high-sensitivity detector and a low conversion loss harmonic mixer are developed for the application to receiving front end.The main contents of this dissertation are as follows:1.Based on zero-bias Schottky barrier diode HSCH-9161 delivered by Avago technology,a W-band detector adopting improved wideband impedance matching network is designed aiming at meeting the design requirements of broadband and high sensitivity.Compared with the traditional circuit scheme,three pairs of short-end stubs are introduced to expand frequency band,which constitutes matching network combined with multi-stage low impedance line.A multi-stage fan-shaped structure is applied in low-pass filter for blocking the RF signals and the harmonic components generated by the diode's nonlinearity.On basis of the nonlinear equivalent circuit of diode,a whole circuit consisting of finline,matching network and low-pass filter is simulated and optimized with EDA tools.The fabricated W-band detector achieves a maximum voltage sensitivity of 7000mV/mW at 82GHz and greater than 1000mV/mW in the frequency range from 75GHz to 103GHz.2.According to the requirements of practical projects,this paper presents a solution for power detection with high sensitivity detectors which are operated in W band.In schematic design,a coupler is used to pick out a sample of RF signal and feed it to the detector working in a linear detection area.Besides,a video amplifier is placed behind the detector to magnify DC voltage.After making consideration on the cost and volume of the product,the whole circuits are integrated on a same substrate.In accordance of the design principle,two power detection circuits are fabricated and tested.One is used in a power amplifier with the function of power monitoring.The output voltage ranges from 96.9mV to 4050.0mV when output power increases from 0.66dBm to 21.66dBm at 93GHz,and the output voltage ranges from 87.8mV to 2470.OmV when output power increases from 1.06dBm to 21.55dBm at 96GHz.Another power detection circuit is applied in a low noise amplifier protection circuit,which has a gain ranging from 7.1dB to 12.2dB and achieves the highest gain at 75GHz.The testing results indicate that the output voltage is 376mV at 76GHz and 323mV at 79GHz when amplifier approaches to saturation.The exponential behavior of output voltage indicates the two circuits work properly,which meets the requirement of the practical application.3.A W-band sub-harmonic mixer operating in frequency ranges from 75GHz to 80GHz is designed by selecting Hittite's monolithic integrated mixer circuit.When IF frequency is 12GHz,the measurement results exhibit a low conversion loss which is less than 12.5dB over RF frequency ranges from 75GHz to 90GHz;the conversion loss is less than 11.7dB while LO frequency is 35.85GHz and IF frequency ranges from 4GHz-12GHz.4.To ensure the noise figure and gain of the module,a W-band down converter including a low noise amplifier and a mixer is developed and tested.It can be seen that the down converter has a good performance with a conversion gain being lower than 6.2dB and max ripple of 4.5dB while RF frequency ranging from 75GHz to 90GHz.According to the requirements of the FMCW system,a W-band receiving front-end consisting of a low noise amplifier cascaded with down converter is measured.The whole circuit has a conversion gain of 11.8dB?15.8dB and the input power 1dB compression point of-23dBm.The output voltage is lower than 50mV when input power is less than-34dBm.The output voltage is higher than 79mV when the circuits approach to saturation. |
PDF Full Text Request