A broadband microwave limiting amplifier

[摘要] ENGLISH ABSTRACT: Limiting amplifiers are employed in electronic warfare (EW) systems requiring a high measure of amplitude control. TheseEW systems employ sensitive signal processing components that are unable to accept the full dynamic range of inputsignals the system must face. The limiting amplifier, however, offers the unique capability of reducing the received signalspectrum to a suitable dynamic range. A typical application of the limiting amplifier is in the instantaneous frequencymeasurement (IFM) receiver where the limiting amplifier allows the receiver to accurately measure pulsed signals over awide input dynamic rangeThe aim of this study is the design and analysis of a broadband limiting amplifier. Focus is placed on the design of a socalledbackbone limiting amplifier (BLA) which forms an integral part of a proposed modular design approach for realizinga design with improved input dynamic range. A designed BLA is discussed in this thesis while insight is given as to theintricacies associated with its mechanism of operation. Over its 45 dB (- 40 to + 5 dBm) input dynamic range, the designed2-18 GHz limiting amplifier offers a typical saturated output power of 7.5 dBm while harmonic suppression of better than8.6 dBc is achieved.The BLA design was based on an existing limiting amplifier design, the so-called baseline limiting amplifier, employingalternating amplifiers and attenuators. Evaluation of the baseline limiting amplifier design allowed for formulation of adesign hypothesis for realizing the BLA design. Physical measurements on the BLA were then used to scrutinize andvalidate the formulated design hypothesis.The requirements for realizing the BLA design were the establishment of a thorough radio frequency (RF) amplifier designcapability, an understanding of the nonlinear phenomena associated with the RF amplifier and the utilization and controlthereof within the limiting amplifier. Different RF amplifier designs that were carried out are discussed in this thesis, whileit is shown how they were used to further investigate important design considerations for application in the BLA design.The computer-aided design packages namely MultiMatch and Microwave Office (MWO) were successfully used inrealizing the desired broadband RF amplifier designs and the eventual BLA design.

[发布机构] Stellenbosch University