![]() 150 on the TSP Order card in this issue to receive a copy by mail ($5 charge). In this algorithm, r( t) is split into two paths, on one of which it is delayed by an interval τ, where 0 under the Electronic Systems category,or circle no. The Doppler effect or the Doppler shift describes the changes in the frequency of any sound or light wave produced by a moving source with respect to an. Where t is time s( t) is the square-wave-pulse-shaped binary data-modulation signal with symbol period T n( t) is the low-pass-filtered version of the additive white Gaussian noise, with independent I and Q components, that is received along with the signal and ω 0denotes the Doppler-frequency shift, which one seeks to estimate, and which is assumed to be constant during the time needed to make the estimate. The in-phase (I) and quadrature (Q) components of the resulting input signal r( t) can be represented in complex form as Prior to processing via this algorithm, the input signal is mixed to baseband, then passed through a low-pass filter of cutoff frequency B/2 to reduce out-of-band noise. Our simulation and experimental results confirm that the new models. the slant ranges for different elevation angles and the coordinates of both the satellite and the earth station. Furthermore, because it is a feedforward rather than a feedback algorithm, it offers at least the potential for better performance in the presence of fading. In low-earth-orbit (LEO) satellite communications, frequency Doppler shift (FDS) results in lower or higher received frequency than the signal initially transmi. The present algorithm does not depend on symbol synchronization and performs well even at Doppler shifts well beyond the symbol rate. An older open-loop scheme is also limited to small Doppler shifts and depends on symbol synchronization. Older closed-loop schemes for estimating and compensating for Doppler shifts do not work at Doppler shifts greater than fractions of symbol rates, nor do they work in the presence of the deep fading that often occurs in mobile operation. Doppler Estimation and Compensation are performed prior to demodulation and other processing. The algorithm implements a feedforward (open-loop) estimation scheme, providing the needed Doppler estimate prior to detection and subsequent processing (see figure) for extraction of data symbols from the modulation. There is a need for estimation of, and compensation for, large Doppler frequency shifts in such a receiver. The algorithm was developed especially for use in processing a received K- or K a-band signal in a ground mobile receiver in a ground-mobile/satellite communication system. ![]() NASA's Jet Propulsion Laboratory, Pasadena, CaliforniaĪn algorithm estimates the Doppler frequency shift in a received radio signal with square-wave-pulse binary differential-phase-shift-keyed (DPSK) modulation. ![]()
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