| Millimeter wave limiter is a common component of millimeter wave system, it protects the front-end of radar system. At present, there are many millimeter wave limiter products in abroad. In domestic, however, there are few limiter products, which working frequency is higher than 18GHz. And even little research about millimeter wave limiter has been done. Therefore, there are important engineering values for this researching.In this article, the millimeter-wave limiter operating at the frequency of 37.5GHz is studied based on the researched microwave and millimeter limiter theory.Millimeter-wave limiters with two stages on microstrip using PIN diodes are designed. When begin designing the limiter, the equivalent circuit of PIN diode should be studied first. Because an accurate equivalent circuit is very important in successfully designing the limiter. Then, the influence between matching circuit and bias circuit of limiter is studied. Finally, the detector is analyzed. The performance of limiter, both at on and off state, has been simulated by the commercial software Agilent advanced design system (ADS). In order to enhance the limiter's limiting capability, a detector and an operating amplifier are applied to PIN diode bias circuit directly. This is achieved by wave-guide coupling-detecting circuit. The detector is also simulated through Agilent advanced design system.The measurement data shows that the return loss and insertion loss is more than 12dB and less than 3dB at 37.5GHz, respectively. The measurement result of limiting ability is not matched well, comparing with the simulation. And this is probably caused by inaccurate equivalent circuit and the performance of PIN diode at millimeter wave frequency. |
