Study Of The 340 GHz 4^th Harmonic Mixer

THz wave belongs to electromagnetic wave whose frequency is defined from 100GHz-10 THz. In accordance with the division of the frequency band, the spectrum of the location in the visible light and millimeter wave, determines the terahertz wave has its unique properties and advantages,such as high resolution and strong penetration.The atmosphere attenuation at 340 GHz is relatively small, so it is can be used in radar, wireless communication system, etc. As an important component in THz application system, the main function of the mixer is to achieve frequency shifting, so it is very important for the performance of the whole receiver. However due to the relatively high frequence of THz wave, now it is difficult to obtain high quality local oscillator for fundamental mixing. And fourth harmonic mixer can makes the LO frequency decreased to one fourth of RF frequency, thereby reduce the demand for the source. In summary, this paper will focus on 340 GHz 4th harmonic mixer.The establishment of the correct model is the key to design the diode mixer. In this paper the diode model is studied. By establishing a three-dimensional model of the diode, and setting the internal wave port, high frequency parasitic effects is studied. And then combined with the intrinsic model of the diode in ADS, the whole model is used to characterize the diode,complete the design passive structure in HFSS. Combined with ADS software, optimize the design of mixer using harmonic balance method.In this paper, we design two mixer model using different diodes, and choose the better simulation reslult of mixer to process. The simulation results show that when the RF input signal in the range of 320GHz-355 GHz, single sideband mixer conversion loss is better than 15 dB, the best conversion loss is 8.29 dB. In the end, the test of the up and down conversion of the 340 GHz 4th harmonic mixer is carried out. The test results show the conversion loss of the mixer is better than 20 dB in the bandwidth of 10 GHz, and the optimal frequency conversion loss is 14.7dB.