A highly accurate DFT-based parameter estimator for complex exponentials, Journal of Telecommunications and Information Technology, 2006, nr 1

A highly accurate DFT-based complex exponential parameter estimation algorithm is presented in this paper. It will be shown that for large number of samples and high signal to noise ratio (SNR), the phase estimation error variance performance is only 0.0475 dB above the Cramer-Rao lower bound (CRLB) for phase estimation with unknown frequency and phase. The amplitude estimation error variance performance was found to lay on the CRLB for amplitude estimation. Exact phase and amplitude estimation can be achieved in the noiseless case with this algorithm. The algorithm has low implementation computational complexity and is suitable for numerous real time digital signal processing applications

Darkening Low-Earth Orbit Satellite Constellations: A Review

The proliferation of low-earth orbit (LEO) satellites and the LEO satellite internet will be a game-changer for the low-latency high-speed global internet. While this new generation of the satellite internet in conjunction with fifth generation network (5G) and sixth generation network (6G) enabled emerging technologies, such as precision farming and smart cities, it will bring new challenges, such as satellite collision, limited satellite lifespan, security concerns, and satellite brightness. This article discusses the satellite brightness caused by LEO constellations that potentially affect the ongoing astronomical studies. It reviews the underlying contributors to the satellite brightness as well as the state-of-the-art technologies proposed to mitigate this emerging challenge.This work was supported in part by Macquarie University; in part by the Australian Research Council Discovery Grants Scheme; and in part by the Faculty of Engineering and Information Technology, University of Technology Sydney, Seed Grant

The Australian Space Eye: studying the history of galaxy formation with a CubeSat

The Australian Space Eye is a proposed astronomical telescope based on a 6U CubeSat platform. The Space Eye will exploit the low level of systematic errors achievable with a small space based telescope to enable high accuracy measurements of the optical extragalactic background light and low surface brightness emission around nearby galaxies. This project is also a demonstrator for several technologies with general applicability to astronomical observations from nanosatellites. Space Eye is based around a 90 mm aperture clear aperture all refractive telescope for broadband wide field imaging in the i and z bands.Comment: 19 pages, 14 figures, submitted for publication as Proc. SPIE 9904, 9904-56 (SPIE Astronomical Telescopes & Instrumentation 2016

Efficient pilot carrier acquisition and tracking in detect and avoid signal processing

For the detect and avoid operation in cognitive radio systems, there is often a requirement to rapidly acquire a pilot carrier in a large frequency uncertainty band. This paper presents a method for rapid pilot carrier acquisition with extremely low computational complexity. A low latency, iterative frequency estimation algorithm is introduced, which accurately determines the pilot carrier frequency and initializes a phase locked loop center frequency. The phase locked loop, with essentially no initial frequency error, is then able to rapidly acquire the pilot signal. Because a narrow band phase locked loop can be used, extremely good phase error tracking performance is achievable with small acquisition time.6 page(s

High-throughput multicarrier satellite transmission using linearized traveling wave tube amplifiers

Traveling wave tube amplifiers (TWTAs), used in satellite transponders, are nonlinear devices. Often, multiple, frequency multiplexed, digitally modulated carriers are transmitted through a satellite transponder. Additionally, square-root raised cosine transmit and received filtering is frequently used to reduce bandwidth requirements, and a result is a large peak power to average power ratio for each carrier at the TWTA input. In this situation, when the TWTA is operated close to its saturation point, there is large bit error rate performance degradation due to the intermodulation products produced by the nonlinearity. Operation of the TWTA with large input and output backoffs provides more linear operation at the expense of TWTA output power. A linearizer, which may be implemented as an instantaneous nonlinearity inserted in front of the input to the TWTA, may be designed such that the cascade combination of the linearizer and the TWTA has a considerably more linear characteristic than the TWTA alone. The optimal TWTA operating point, which minimizes the performance losses both due to bit error rate degradation and TWTA output backoff, is obtained with less TWTA output backoff using the linearizer. In this paper, the performances for both the TWTA and the linearized TWTA are obtained by computer simulation, and the performance advantage of the linearized TWTA is determined for extremely bandwidth efficient, frequency multiplexed, square-root raised cosine pulse shaped QPSK modulated carriers. A modest power efficiency advantage of the linearizer is shown for this extremely bandwidth efficient, multicarrier case.16 page(s

Deteriorative effects on feature-based signal detection due to imperfect training

Feature-based detection techniques have been advocated for robust spectrum sensing in cognitive radios. Cognitive radios must be able to train themselves to identify the features for a specific primary user at a given channel, time or location. However, 'in-the-field' training relies on signal observations where there is uncertainty about whether or not it is truly representative of the primary user. This work considers this uncertainty, how it effects the detector's training time and performance, and identifies a trade-off between these outcomes. A two-stage detector structure is also illustrated to fulfill both the training and operational requirements of such detectors.6 page(s

Frequency error correction for OFDM based multicarrier systems and performance analysis

The presence of frequency offsets in the received signal for an orthogonal frequency division multiplexing (OFDM) based multicarrier system leads to inter carrier interferences (ICI). The degradation in the performance of an OFDM system is severe when there is frequency error, which is caused by the loss of orthogonality in the received carrier frequencies. Here, we look into the correction of frequency errors in the received OFDM signal, by means of a correlator based maximum likelihood (ML) frequency estimator. We analyse the system performance of the frequency corrected OFDM system and study the statistical nature of the frequency uncertainty in the receiver when the ML frequency estimator is used. The statistical distribution of the estimates made by the receiver is also determined.5 page(s

Performance analysis of a Digital Phase-Locked Loop with a Hyperbolic Nonlinearity

The treatment of phase locked loops (PLL) has been heavily looked into over the past several decades on its performances and analysis, and is a very old topic. However the usage of it has never been reduced with the rapid evolvement of various open loop and closed loop systems. In this paper we analyse the performance of an arctan based digital phase locked loop (DPLL) with a hyperbolic nonlinearity for single-tone carrier tracking. We purposely introduce the nonlinearity for improved performance of the closed loop system. We look at the acquisition performance of the DPLL by considering the phase plane portrait and the lock-in range of the loop. The steady state (SS) performance of the loop is analysed by considering the open loop SS statistical distribution of the phase noise

A highly accurate DFT-based parameter estimator for complex exponentials

7 page(s

Spectral symmetry iterative frequency estimation algorithm

In this paper, a new technique called the Spectral Symmetry Iterative (SSI) frequency estimation algorithm is disclosed. This algorithm can be used for estimating the frequency and phase of a wide class of signals that are bandpass in nature. This technique can precisely determine the centre frequency of this class of signal in noiseless condition and can yield frequency error variance performance that is comparable to the Cramer Rao lower bound (CRLB) on frequency estimation error of a single complex exponential in the additive white Gaussian noise (AWGN).4 page(s