Design of high power waveguide limiter /

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2014




Microwave limiters are protector structures. Microwave limiters protect the receiver circuits from high power microwave signals. Receiver circuits of radar systems are able to process the signals with low level amplitude. This situation results in usage of very sensitive circuit blocks. These sensitive circuit blocks, such as LNAs, are protected from high power signals by limiters. The causes of the undesired microwave signals with high level amplitude can be transmitter to receiver leakage and high power microwave short pulses coming from outside as an enemy attack. Transmitter leakages are predictable threats because transmitted signal timing is known. However threats from outside is unpredictable because the time of threat cannot be known. Outside threats can cause problem in the radar system at any time. In order to protect receiver channel of radar system, low response time high power microwave limiter must be used. In this study, two critical points are aimed. The limiter, which can handle the signals with kW power levels, and which have low response time is aimed. Two different single stage waveguide limiters, whose operating frequency bands are 9.4-10 GHz, are designed with two different high power pin diodes. Linear/Nonlinear measurements of waveguide limiters are performed. Then these two single stage limiters are connected in cascade and the resulting two stage waveguide limiter is measured. In order to increase the sensitivity and the response speed of the waveguide limiter, the waveguide detector is designed with the Schottky diode. The limiters are measured with the WG detector. Circuit designs and simulations are performed using AWR® and CST®.