The Research Of Fourth Harmonic Mixer X-band Radar Receiver Front-end

Ship navigation radar as a guarantee of the safety of navigation of the ship, hasgood prospects for development.Ship navigation radar receiver front-end is the keycomponents of ship navigation radar which includes of a low-noise amplifier, mixer,local oscillator and has great significance in ship navigation radar.The contents of this paper are based on a X-band navigation radar receiverfront-end, the superheterodyne system using4-harmonic mixer technology.Suchreceiver has the advantage of reducing the difficulty in design and lowering the cost ofthe local oscillator signal source.The front-end circuit structure includes a low-noise amplifier,a fourth harmonicimage rejection mixer and a local oscillator.The low-noise amplifier applies a FETtransistor TC2181of Transcom Company. Two narrow-band low noise amplifier issimulated by the software ADS and manufacted with the result of the simulation to realobject. The Gain of the low-noise amplifier is20.5dB by test. The local oscillatorsource is achieved by the phase-locked loop method. The PLL circuit includes alock-chip circuit, a reference crystal oscillator(TCXO）microcontroller and a drivenamplifier. The PLL chip is from ADF4350of AD company, and use a microcontroller tolet the ADF4350output a frequency of2.3675GHz, and at last use the MAAL-009120which is a driven amplifier of M/A-COM to amplify the signal power. By testing, theoutput powe is15.67dBm, the phase noise of the PLL is better than-80dBc/Hz@1kHzand the spurious suppression is better than80dBc. To achieve a certain degree of imagerejection, the fourth harmonic mixing mode whose core device is a parallel reversedSchottky diode HSMS8202and a circuit structure of the image rejection is applied. Thecircuit includes a RF input bridge, a LO input power splitter, two4-harmonic mixer anda IF bridge. The conversion loss of the real object is15dB, image rejection is10dB.Finally, the low-noise amplifier, mixer, local oscillator are placed in a special designedcavity and then the entire front-end could be tested, and the gain is5.2dB, and thedesign meet the expected targets. The paper work includes each part of the circuit simulation, design of layout andcavity, physical circuit debugging. The passive part of the mixer including splitters andRF bridge is designed by both ADS and HFSS software, the low-noise amplifier andmixer is simulated by ADS, Cavity is designed by Autodesk’s design software AutoCAD.The physical circuit is mainly tested by the instruments spectrum analyzer (HP8563E,Agilent9320B), signal source, vector network analyzer(Anritsu34369D).