Improved Carrier Tracking of Space Telemetry Signals Using Cascaded Phase Locked
A Carrier Aiding technique that employs cascaded phase-locked loops is described.
Shihabi, M.↗
Engineering topics
Shah, B.
Publications and source records attributed to Shah, B..
Residual and suppressed-carrier arraying techniques for deep-space communications
Three techniques that use carrier information from multiple antennas to enhance carrier acquisition and tracking are presented. These techniques in combination with baseband combining are analyzed and simulated for residual and suppressed-carrier modulation. It is shown that the carrier arraying using a single carrier loop technique can acquire and track the carrier even when any single antenna in the array cannot do so by itself. The carrier aiding and carrier arraying using multiple carrier loop techniques, on the other hand, are shown to lock on the carrier only when one of the array elements has sufficient margin to acquire the carrier on its own.
Shihabi, M.↗
A Novel Parallel All-Digital Buffered Telemetry Demodulator for Future Low Cost Space Missions
This paper functionally describes a novel Buffered Telemetry Demodulator (BTD) suitable for future low cost space missions characterized by low data rates and relatively weak space-to-ground communication links.
BTD Buffered Telemetry Demodulator resynchronizati↗
A comparison of full-spectrum and complex-symbol combining techniques for the Galileo S-band mission
Full-spectrum combining (FSC) and complex-symbol combining (CSC) are two antenna-arraying techniques being considered for the Galileo spacecraft's upcoming encounter with Jupiter. This article describes the performance of these techniques in terms of symbol signal-to-noise ratio (SNR) degradation and symbol SNR loss. It is shown that both degradation and loss are approximately equal at low values of symbol SNR but diverge at high SNR values. For the Galileo S-band (2.2 to 2.3 GHz) mission, degradation provides a good estimate of performance as the symbol SNR is typically below -5 dB. For the following arrays - two 70-m antennas, one 70-m and one 34-m antenna, one 70-m and two 34-m antennas, and one 70-m and three 34-m antennas - it is shown that FSC has less degradation than CSC when the subcarrier and symbol window-loop bandwidth products are above 3.0, 10.0, 8.5, and 8.2 mHz at the symbol rate of 200 sym/sec, and above 1.2, 4.5, 4.0, and 3.5 mHz at a symbol rate of 400 sym/sec, respectively. Moreover, for an array of four 34-m antennas, FSC has less degradation than CSC when the subcarrier and symbol window-loop bandwidth products are above 0.32 mHz at the symbol rate of 50 sym/sec and above 0.8 mHz at the symbol rate of 25 sym/sec.
Million, S.↗
Performance of Full-Spectrum Combining for the Galileo S-Band Mission
This paper describes the performance of Full-Spectrum Combining (FSC), an arraying technique being considered for the Galileo S-Band Mission.
Full-Spectrum Combining signal-to-noise ratio Gali↗
Arraying Techniques for the Galileo S-Band Mission, Part II - Complex Symbol Combining
Antenna arraying is becoming an increasingly popular technique to enhance the quality of signals received from distant transmitters. In principle, arraying is a simple concept that increases signal-to-noise (SNR) ratio by combining waveforms with identical signal sources and independent noise sources.
antenna arraying↗
Limitations on the Subcarrier Frequency-to-Symbol Rate Ratio
For space missions in which tracking the residual carrier is absolutely critical, the use of a subcarrier to separate the data from the residual carrier is the best way to maximize residual-carrier tracking performance.
subcarrier-to-symbol rate ratio↗
Arraying Techniques for the Galileo S-Band Mission, Part I - Full Spectrum Combining
It has been known for some time now that when signals from a single source are received at multiple antennas, these antennas can be arrayed to enhance the quality of the received signal. What has been relatively unknown, however, is that the quality of the combined signal critically depends on the arraying algorithm, as well as, the characteristics of the transmitted signal.
arraying algorithms↗
A functional description of the Buffered Telemetry Demodulator (BTD)
This article gives a functional description of the buffered telemetry demodulator (BTD), which operates on recorded digital samples to extract the symbols from the received signal. The key advantages of the BTD are as follows: (1) its ability to reprocess the signal to reduce acquisition time; (2) its ability to use future information about the signal and to perform smoothing on past samples; and (3) its minimum transmission bandwidth requirement as each sub carrier harmonic is processed individually. The first application of the BTD would be the Galileo S-band contingency mission, where the signal is so weak that reprocessing to reduce the acquisition time is crucial. Moreover, in the event of employing antenna arraying with full spectrum combining, only the sub carrier harmonics need to be transmitted between sites, resulting in significant reduction in data rate transmission requirements. Software implementation of the BTD is described for various general-purpose computers.
Tsou, H.↗
Application of multirate digital filter banks to wideband all-digital phase-locked loops design
A new class of architecture for all-digital phase-locked loops (DPLL's) is presented in this article. These architectures, referred to as parallel DPLL (PDPLL), employ multirate digital filter banks (DFB's) to track signals with a lower processing rate than the Nyquist rate, without reducing the input (Nyquist) bandwidth. The PDPLL basically trades complexity for hardware-processing speed by introducing parallel processing in the receiver. It is demonstrated here that the DPLL performance is identical to that of a PDPLL for both steady-state and transient behavior. A test signal with a time-varying Doppler characteristic is used to compare the performance of both the DPLL and the PDPLL.
Sadr, R.↗
Acquisition performance of various QPSK carrier tracking loops
The frequency and phase acquisition performance of three quadrature phase shift keying (QPSK) carrier tracking loops, the MAP estimation loop, the Costas crossover loop, and the generalized Costas loop, is described. Acquisition time and probability of acquisition as a function of both loop signal-to-noise ratio and frequency offset to loop bandwidth ratio are obtained via computer simulations for type II and III loops. It is shown that the MAP loop, which results in the smallest squaring loss for all signal-to-noise ratios, is sometimes outperformed by the other two loops in terms of acquisition time and acquisition probability.
Hinedi, S.↗
Symbol lock detection in the ARX 2 and Block 5 receivers
The performances of 5 symbol-lock detectors are compared. These detectors are the square-law detector with overlapping (SQOD) and nonoverlapping integrators, the absolute-value detectors with overlapping and nonoverlapping integrators, and the signal-power estimator detector (SPED). The analysis considers various scenarios in which the observation interval is much larger than or equal to the symbol-synchronizer loop bandwidth, and which were not considered in previous analyses. Also, the case of threshold setting in the absence of signal is considered. It is shown, that the SQOD outperforms all others when the threshold is set in the presence of a signal, independent of the relationship between loop bandwidth and observation period. On the other hand, the SPED outperforms all others when the threshold is set in the presence of noise only.
Shihabi, M.↗
Open-loop frequency acquisition for suppressed-carrier biphase signals using one-pole arm filters
Open loop frequency acquisition performance is discussed for suppressed carrier binary phase shift keyed signals in terms of the probability of detecting the carrier frequency offset when the arms of the Costas loop detector have one pole filters. The approach, which does not require symbol timing, uses fast Fourier transforms (FFTs) to detect the carrier frequency offset. The detection probability, which depends on both the 3 dB arm filter bandwidth and the received symbol signal to noise ratio, is derived and is shown to be independent of symbol timing. It is shown that the performance of this technique is slightly better that other open loop acquisition techniques which use integrators in the arms and whose detection performance varies with symbol timing.
Shah, B.↗
QPSK carrier-acquisition performance in the advanced receiver 2
The frequency-acquisition performance of the Costas cross-over loop which is used in the Advanced Receiver 2 (ARX 2) to perform Quadrature Phase Shift Keying (QPSK) carrier tracking is described. The performance of the Costas cross-over loop is compared to two other QPSK carrier tracking loops: the MAP estimation loop and the generalized Costas loop. Acquisition times and probabilities of acquisition as functions of both loop signal-to-noise ratio and frequency-offset to loop-bandwidth ratio are obtained using computer simulations for both type-2 and type-3 loops. It is shown that even though the MAP loop results in the smallest squaring loss for all signal-to-noise ratios, the MAP loop is sometimes outperformed by the other two loops in terms of acquisition time and probability.
Hinedi, S.↗
Performance of the split-symbol moments SNR estimator in the presence of inter-symbol interference
The Split-Symbol Moments Estimator (SSME) is an algorithm that is designed to estimate symbol signal-to-noise ratio (SNR) in the presence of additive white Gaussian noise (AWGN). The performance of the SSME algorithm in band-limited channels is examined. The effects of the resulting inter-symbol interference (ISI) are quantified. All results obtained are in closed form and can be easily evaluated numerically for performance prediction purposes. Furthermore, they are validated through digital simulations.
Shah, B.↗