Design Of A X-band Miniaturized Balanced Microwave Limiter

Limiter is an important microwave control device which is widely used in radarreceiver systems. In recent years, with the rapid development of the thin film hybridintegrated circuit technology, the microwave limiter assembled by the metal thin filmtechnology has become a key component in the front-end of the receiver because of itssmall size, excellent performance and high reliability.This paper studies on a X-band miniaturized balanced microwave limiter. Theadvantages of the limiter are: the balanced circuit structure improves the power capacityof the diodes, and also effectively solves the problem of the circuit’s needing towithstand high power, to work with low insertion loss, low leakage power, and shortrecovery time. The balanced structure also gives the circuit an ideal VSWR in the wholepower range, and provides a favorable absorption match in the system terminal.In this paper, firstly, the limitation and selection method of the PIN diode at highRF power were investigated in detail in terms of the structural characteristics of thelimiter circuit, the thermal resistance, the heat capacity of the I region, the minimumthermal time constant, the steady-state and pulse transient temperature rise of theincident power. Secondly, the multi-level arranging limiter diodes and the quasi-activecircuit were used in the limiter design. The leakage power of the limiter wassignificantly inhibited by using the microwave conductivity modulation effect of thePIN diode and the rectification effect of the Schottky Barrier diode. Finally, based onthe optimization results of ADS, HFSS, and also combined with the integrated hybridmetal film technology, this study had finished the design and assembly of the circuitsubstrate, the carrier board and the test chamber. The comprehensive performance of thelimiter was presented through the electrical and environmental test.The measurement data shows that: in8.8~10GHz, the insertion loss of the limiter≤1.3dB, input and output VSWR≤1.2, power handling capability: peak power150W(pulse width60μs,3%duty), spike leakage power≤8mW, flat leakage power≤8mW,recovery time≤130nS, the circuit size≤16mm×14mm×3mm.