TRANSIENT BEHAVIOR OF MICROWAVE NETWORKS

The purpose of this study is to investigate the transient behavior of nonreciprocal ferrite devices and coupled networks which are used in wideband radar and communications systems to process signals having wideband spectral content. The report is divided into three major component study areas. They are: (1) nonreciprocal ferrite devices (e.g., isolators, circulators); (2) coupled TEM-mode networks (e.g., the quarter-wavelength or parallel-line coupler); (3) coupled waveguide networks (e.g., the sidewall coupler). In addition, a major subsection is devoted to determining the utility of describing the transient behavior of a microwave network by a single parameter in the frequency domain, namely, 'the bandwidth'. New methods are introduced to evaluate transients in microwave networks in both the study of ferrite and waveguide networks; in the former area a microstrip circulator is suggested for wideband application. A new definition of effective bandwidth for microwave networks is offered which considers energy stored in the natural modes of the device. Finally, a novel class of parallel-line couplers whose impulse response is time limited is introduced: the impulse response consists of two delayed impulses. Both the theoretical and experimental portions of this study employ a time domain analysis as opposed to the conventional frequency domain approach. It is shown that a time domain analysis yields considerable insight and suggests new network models.