Method for evaluating the frequency offset of an embedded local oscillator in retranslator from its nominal value using OFDM signal

The rapid modernization of radio-electronic equipment leads to increasing demands and constraints. Such devices must undergo rapid testing for compliance with these limitations. This necessitates the search for methods and techniques for measuring device characteristics that meet metrological requirements. This work presents a technique for measuring the frequency offset of a built-in oscillator of a communication satellite transponder relative to its nominal value using a polyharmonic signal. The measurement setup is described, consisting of two generators, the device under test (DUT), and a digital oscilloscope. The generator, whose signal is fed to the radio frequency input of the mixer, is connected to the digital oscilloscope via its output and synchronization input (synchronization is implemented using the vector signal generator). A signal with a frequency adjusted for the deterministic error (in the form of a constant offset over the measurement time interval) is set on the local oscillator. The signal is recorded on a digital oscilloscope, with subsequent transformation to the frequency domain using the VSA module. There, the frequency offset is calculated using the phase increment values. An experiment was conducted to measure the frequency offset of the vector signal generator. Various deterministic errors were set in the range from -1 kHz to 1 kHz, with 3 measurements performed for each value. It was found that when using external synchronization from the vector signal generator, the dependencies of the frequency offset on the set deterministic errors have a similar character for each realization. For the setup using external synchronization from the vector signal generator, it was observed that the dependencies of the frequency offset on the set deterministic errors differ for each realization. The instrumental error, reflecting the accuracy of the proposed method, was obtained. Also, the frequency offset error values corresponding to a real system with a built-in local oscillator are presented.