Estimation of the group delay of a signal in the receiving path of measuring devices with the use of step response

We consider the methods used for calibration of coordinate-time measuring instruments of current parameters of the global navigation satellite systems. For the calibration of coordinate-time measuring instruments in the process of their design and testing, it is customary to use simulators of signals of the global navigation satellite systems. However, these simulators should be also calibrated. At present, there exist various procedures of guaranteeing the metrological characteristics of simulators, including their calibration with the help of an oscilloscope. However, this method has not only advantages but also disadvantages connected with the application of oscilloscope. Note that the development of a new reference measuring device, namely, a calibrator of the simulator of signals of the global navigation satellite systems is now carried out at the VNIIFTRI. Since the operation of the calibrator is based on the same principles as the operation of the navigation receiver and the calibrator determines the time of propagation of the signal (group delay time) received from the calibrated simulator, it is extremely important to accurately evaluate the intrinsic group delay time of the calibrator introduced by the receiving path and to develop the procedure for the determination of this metrological characteristic. The applied circuit solutions used in the design of calibrators include digital blocks, e.g., digital-to-analog or analog-to-digital converters. The aim of the performed investigations is to estimate the group delay time in the input circuit of the calibrator containing an analog-to-digital converter. The traditional methods used for estimating the group delay time by using S‑parameters are not suitable for this purpose because they do not enable one to compare analog and digital signals. In the present work, we develop an indirect method for estimating the group delay time of a signal in the receiving path of the calibrator according to the step responses of the circuit. The method proposed by the authors determines the group delay time of the signal in the receiving path of the calibrator according to the step response of the circuit. The field of application of the proposed method is the verification and calibration of measuring devices, which use input and output signals with analog-to-digital conversion. By using this method, we estimated the group delay time of the signal in the calibrator circuit containing an analog-to-digital converter. We present the results of investigations of the indicated time characteristic by the proposed method for circuits containing various microwave devices (power splitters and circulators). The proposed method enables us to obtain exact estimates of the frequency characteristics of circuits of measuring devices and normalize their metrological characteristics.