Research On The High Performance Detection Circuit Of W-band

With the rapid development of technology, millimeter wave radiometer, which has vast market and great commercial value, is widely used in many important areas, such as remote sensing, detection, and security. Detector circuit as the core part radiometer, especially the direct detection structure circuit, has become the hot rearch topic because of its simple structure, low system noise temperature in recent years. Therefore, this thesis is forcus on the W-band detector circuit.In the W-band, feeds of test equipments are waveguide ports. This paper firstly developed a waveguide-microstrip transition by finline, using Spline curve to shorten the size of finline transition structure and adding convex grooves by the end of the dielectric substrate to improve the impedance discontinuity at the interface. Eventually the back to back structure of the transition had been carried out and tested. The experimental results showed that the insertion loss of the back to back structure was less than 2dB in the working band 84～110GHz, and the reflection coefficient S11 was less than-12dB.The reflection coeffient S11 was also less than-9dB in the whole 80～110GHz. The insertion loss of the single transition is less than 0.9dB.Subsequently, A W-band detector and a low-noise amplifier had been developed using the finline-structure waveguide-microstrip transition. The W-band detector used a new type zero bias Schottky diode, which had few studies in the domestic, made by VDI company. Firstly, we extraced the Spice model parameters of the diode, and then made the simulation of the detector by the Spice model. In the end, the detector was manufactured and tested. The results showed that the voltage sensitivity is greater than 800mV/mW in the operating frequency band 84-94GHz, especially at 92GHz the voltage sensitivity is up to 1900mV/mW, which is close to the international advanced level.In the end, we developed the W-band low-noise amplifier. Through cascading two MMICs, made by Gotmic company, to achieve the expected gain of 30dB or more. In order to prevent inter-chip-level feedback, we joined the wall between the two MMICs, and the wall was optimated by HFSS software. A sequency power module was also manufactured to complete the single power supply; For the purpose of achieving physical isolation between high frequency part and low frequency part of LNA, we designed cavity structure and put the two parts on the positive and negative of the cavity respectively. Finally assembly and testing of the LNA were completed, the experimental data showed the gain of LNA is 18±2dB, in the operating band of 84～94GHz and 1dB compression output power is OdBm at 89GHz. The results suggested that the LNA chips was not as good as it described. In order to achieve the desiered targets, we cascad two LNAs and calculated the minimum noise temperature of the whole system. The minimum noise temperature was 0.6K, which reached the expected targets.