Testing frequency hopping devices

Abstract

An improved system and method for testing high frequency electronic devices. The improvement allows characteristics such as phase noise to be measured while a device under test changes operating frequency (frequency hops) at its normal rate. In accordance with the invention, a dynamic controller programs the frequencies of first and second frequency synthesizers at precisely controlled instants of time. For each of the first and second synthesizers, the dynamic controller includes a frequency memory for storing a sequence of frequency data, a counter for sequencing through the frequency memory, and a timing source for activating the counter. Data stored at each location of the frequency memory represents a frequency to which the respective synthesizer is to be programmed. The output from the first synthesizer is provided to the input of a device under test (DUT), in response to which the DUT generates and output signal. A mixer receives at its inputs the output of the DUT and the output of the second synthesizer. The mixer combines the two inputs to generate a test signal. The test signal can then be digitized, and the resulting digital samples can be evaluated. Under control of the timing source, the dynamic controller steps through different addresses of the frequency memories for the first and second synthesizers. At each memory location, new data are sent to the synthesizers at precisely controlled instants of time. New frequencies are established, and the test signal is again digitized. Characteristics of the DUT can be determined from the digital samples at each frequency that the DUT assumes.