THE APPLIED METHOD FOR CARRIER FREQUENCY RESTORATION OF THE TELEMETRY SYSTEMS SIGNAL BY DIGITAL PROCESSING

Abstract

The paper considers the issue of restoring the level of the telemetry signal carrier frequency at digital processing in the automatic carrier control tract and the calculation of the threshold for taking the decision about the validity of received information symbol from the spacecraft and carrier rocket. We have described the applied method and algorithm for calculating the level of the carrier frequency and the level of threshold for making a solution based on histogram processing of the signal from the output of the frequency detector.

Full Text

The control of flight task execution by class SC/CR onboard systems is performed based on the processing of telemetric data (TMD) on the status of most units and devices of the object [1]. For a satisfactory receipt and processing of TMD achieving proper ground means that the following parameters are required for positive detection of received char (“0” or “1”): the restoration of radio signal carrier frequency and the calculation of decisions making the threshold. Currently, the fast Fourier transformation (FFT) or data parameter linear filtering procedures are usually applied to repair carrier frequency of carrier-shift radio signal [2]. The use of FFT requires a large number of processing operations to get a necessary result, and consequently, a significant time to analyze the signal. The linear filtering (LF) usage leads to complicity for unbiased signal estimate under processing. Besides, the usage of conventional approaches (FFT and LF) for signal processing on a significant noise background does not allow positive detecting of carrier frequency radiosignals [3]; this considerably decreases the sensitivity of radio receiver digital channels. Alternatives to FFT and LF correction carrier frequency procedures and algorithms are still insufficiently presented in Russian and foreign studies [4–6]. Therefore a development of procedures and algorithms (P-A) for carrier frequency correction (CFR) based on the histogram procedure is considered to be rather urgent, since this method would require considerably less computing sources than FFT. The CFR procedure presented in this paper is developed based of the histogram procedure. The point of the procedure is the following: the range of possible signal levels at the detector’s output frequency is divided into an optimal number of control levels or intervals.