Instantaneous frequency measurement devices are useful for conducting extremely fast measurements of the current frequency value of microwave signals, even if their duration is extremely short. This paper presents the principle of determination of temporary values of the microwave signal phase and frequency using interferometer techniques, based on passive microwave components. Additionally, the structures and results of measurements of two novel versions of integrated microwave correlators for microwave frequency discriminators, made on a single printed circuit board, are shown. Three Wilkinson-type, single-stage power dividers, and two rat-race hybrids create the developed correlators. The developed devices were designed to work over a wide frequency range, i.e., of 1.6–3.1 GHz, and can be used to monitor Wi-Fi devices as well as pulse and CW radar systems operating in the S band. They can also be applied in passive radars and active Doppler radars. The view of the printed circuits boards and results of measurements are presented. Recommendations for improving the accuracy of measurement are proposed.
The paper presents an analysis of a microwave interferometer with a multi-ports architecture with one input and four outputs. The tested system consisted of two main parts: a subsystem consisting of a power divider and two transmission lines of different electric length -responsible for developing two signals whose phase difference will depend on the frequency of the input signal. The second part of the tested system consisted of a six-port elementa 4 x 4 Butler matrix, whose task was to develop four signals. The output amplitude depends on the phase difference of the signals fed to the inputs of this six-ports. Frequency detector tests were carried out by calculations in the MATLAB computer program in a very wide band fg/fd=4. The system response was analyzed for different combinations pair of an input ports of a six-port system and for different values of coupler coupling coefficients. During the analysis it was shown that the parameters of such an interferometer depend on which ports pair is excited as well as on the value of the coupling factor of the couplers. It is important to specify the system parameters in order to make the optimal selection of the interferometer system configuration in terms of the acceptable frequency detection error, operating bandwidth, or even the topological distribution of the ports.
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