.8 Mm Power Limiter Study

Millimeter wave limiter is the key component of millimeter wave system, and plays an important part in radar system especially. The research in 8mm band limiter had last for a long time in abroad and with many kinds of products. However, there are no products operating higher than 18GHz at frequency, even no papers reported in domestic. So, this thesis has its important engineering value. In this work, the millimeter-wave limiter operating at the frequency of 30GHz is studied based on microwave limiter theory. Millimeter-wave limiters with single stage and two stages in wave-guide using PIN diodes are designed.At first, the equivalent circuit of post in waveguide is studied. The accurate equivalent circuit is very important in simplifying the wave-guide limiter. Then, the position of diodes, the length between diodes to the short and the distance between two diodes, which are the key factor in designing pin wave-guide limiters, are detail studied. The performance, both at on and off state, has been simulated for two different type limiters using commercial software Agilent advanced design system (ADS).Wave-guide coupling-detecting circuit has been applied for designing two stages limiter, and the validation is also given out.The measurement results shows that the insertion loss and isolation of single stage are less than 4dB and more than 19dB at 30GHz, respectively. And the insertion loss and isolation of two stage type are less than 4.5dB and more than 30dB at 30GHz, respectively. The results also shows that the insertion loss of measured is not very coincide with simulated. And this is caused by inaccurate equivalent circuit and the performance of PIN diodes.