International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Bit error rate (BER) and bandwidth efficiency of several variations of enhanced Feher patented quadrature phase shift keying (FQPSK) [1] are described. An enhanced FQPSK increases the channel packing density of that of the IRIG 106-00 standardized FQPSK-B by approximately 50% in adjacent channel interference (ACI) environment. As the bandwidth efficiency of FQPSK-B DOUBLES (2×) that of pulse code modulation/Frequency modulation (PCM/FM) [5], the enhanced FQPSK, with a simpler transceiver than FQPSK-B, has a channel packing density of TRIPLE (3×) that of PCM/FM. One of the other enhanced FQPSK prototypes has an end to end system loss of only 0.4 dB at BER=1x10^(-3) and 0.5 dB at BER=1x10^(-4) from ideal linearly amplified QPSK theory. The enhanced FQPSK has a simple architecture, thus is inexpensive and has small size, for ultra high bit rate implementation. With low redundancy forward error correction (FEC) coding which expands the spectrum by approximately 10%, further improvement of about 3-4.5dB E N b o is attained with NLA FQPSK-B and enhanced FQPSK at BER=1x10^(-5) .

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The performance of novel experimental blind equalizers suitable for a large class of applications including telemetry systems and other wireless applications is described. Experimental hardware research of these adaptive patent pending Feher Equalizers (FE) confirms computer simulated data [1]. A two-ray RF selective faded telemetry channel has been simulated. A dynamically changing channel environment with a selective fade rate in the 1Hz to 50Hz range has been constructed by laboratory hardware. The Test and Evaluation (T&E) setup had RF frequency selective dynamic notch depth variations in the Power Spectral Density (PSD) within the band of the signal of up to 15dB. As an illustrative example of the adaptive equalizer capability we used a 1Mb/s rate Feher patented FQPSK [1] Commercially Of The Shelf (COTS) product. Both hardware experimental results as well as simulation indicate substantial performance improvement with the utilization of the FE. It is demonstrated that the FE improves for a large class of frequency selective faded systems the Bit Error Rate(BER) from 10^-2 to 10^-6. Similar performance improvements are presented for the Block Error Rate (BLER).

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / FQPSK is the abbreviation for Feher Quadrature Phase Shift Keying (FQPSK) patented systems [1]. Digcom, Inc. licensed FQPSK products demonstrated significant spectral saving and RF power efficient robust BER performance advantages. These bit rate agile modems and Non Linearly Amplified (NLA) transceivers, DSP and hardware implementations, and in some instances “software-radios” (20kb/s to more than 100Mb/s) and RF frequency agile (from 150MHz to more than 40GHz) developments and systems have recently been demonstrated and deployed. The spectral efficiency, i.e., data throughput capability of the 1st generation of FQPSK, as demonstrated in initial Advanced Range Telemetry (ARTM) flight tests, approximately doubles while 2nd generation “FQPSK-2” systems have the potential to quadruple the spectral efficiency of operational PCM/FM telemetry systems and be backward compatible with the 1st generation of FQPSK technologies. It is also demonstrated that the spectral efficiency advantage of FQPSK over that of NLA power efficient GMSK, OQPSK and QPSK modulated transceivers is in the 50% to 300% range and that the potential spectral efficiency advantage of FQPSK-2 over GMSK [1] is in the 200% to 500% range. Based on extensive multi-year studies of alternative solutions for spectral and RF power efficient, robust BER performance systems, several commercial US and international organizations, AIAA, CCSDS, NASA, ESA, CCSDS and various programs of the US Department of Defense (DoD) concluded that FQPSK offers the most spectrally efficient high performance-high speed proven technology solutions and recommended FQPSK standardization for several data links. Initial DoD-ARTM Program Office Air-to-Ground L-band and S-band jet airborne telemetry Test and Evaluation (T&E) data, obtained during the summer of 1998 are briefly highlighted. These include simultaneosly tested FQPSK and PCM/FM. In these tests the following ARTM objectives have been demonstrated: (a) FQPSK approximately doubles the spectral efficiency of currently operational PCM/FM; (b) The Data Link Performance of these two systems is comparable. The American Institute of Aeronautics and Astronautics (AIAA) draft modulation standard recommended to the DoD, NASA and CCSDS, was approved by the AIAA [23]. The AIAA standard recommends “that FQPSK modulation be immediately adopted as the interim increment–1 standard.”

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / This paper presents noncoherent limiter-discriminator detection and differential detection of FQPSK (Feher quadrature phase-shift-keying) with maximum-likelihood sequence estimation (MLSE) techniques. Noncoherent FQPSK systems are suitable for fast fading and cochannel interference channels and channels with strong phase noise, and they can offer faster synchronization and reduce outage events compared with conventional coherent systems. In this paper, both differential detection and limiter-discriminator detection of FQPSK are discussed. We use MLSE with lookup tables to exploit the memory in noncoherently detected FQPSK signals and thus significantly improve the bit error rate (BER) performance in an additive white Gaussian noise (AWGN) channel.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis describes the design and implementation of a software based QPSK demodulator with a demodulation speed of 100 Mbps. The objective of the thesis was to identify a topology for the QPSK demodulator that would allow for high data rates and the design of the synchronization algorithms for carrier and symbol recovery. The QPSK demodulator was implemented on an Altera Stratix II field programmable gate array (FPGA), which does complex I and Q sampling on a down converted 720 MHz QPSK signal. The I and Q down converted baseband signals are sent through matched filters which are implemented with discrete components to maximize the signal to noise ratio of the received rectangular baseband pulses. A 1 GSPS direct digital synthesizer (DDS) is used to generate the synchronous clock for the analog to digital converters which samples the matched filter outputs. The demodulator uses two samples per symbol to demodulate the QPSK signal. A dual locking system is implemented to have a wide pre-locking filter for symbol synchronization and a narrow band post-lock filter to minimize the loop noise. A symbol lock detection algorithm decides when the symbol recovery loop is locked and switches between the loop filters. A second 1 GSPS DDS output is mixed with a local oscillator to generate the 1.44 GHz LO signal for the quadrature down conversion. The carrier recovery loop uses a numerically controlled oscillator inside the FPGA for initial carrier acquisition which allows for very wide locking bandwidth. After lock is achieved, the external carrier recovery loop takes over and removes any frequency offset in the complex baseband signal by changing the frequency of the DDS. A QPSK modulator was also developed to provide a QPSK signal with known data. The modulator can generate any constellation diagram up to 256 points. / AFRIKAANSE OPSOMMING: Hierdie tesis bespreek die ontwerp en implementasie van ’n sagteware gebaseerde QPSK demodulator met ’n demodulasie spoed van 100 Mbps. Die doelstelling is om ’n topologie te identifiseer vir ’n QPSK demodulator wat ’n hoë datatempo sal toelaat en ook om sinkronisasie algoritmes te ontwikkel vir draer en simbool herkenning. Die QPSK demodulator is geïmplimenteer op ’n Stratix II FPGA van Altera wat kompleks basisband monstering doen op infase en kwadratuur basisband seine. Die basisband seine word gegenereer van ’n 720 MHz QPSK sein met ’n kwadratuur menger wiese uittrees deur puls passende filters gestuur word om die sein tot ruis verhouding te maksimeer. ’n Een gigamonster per sekonde direk digitale sintetiseerder (DDS) is gebruik om die klok vir die analoog na digitaal omsetters te genereer vir sinkrone monstering van die pulse passende filter uittrees. Die demodulator gebruik twee monsters per simbool om ’n QPSK sein te demoduleer. ’n Tweevoudige sluit algoritme word gebruik vir die simbool sinkronisasie waar ’n wyeband filter die inisiële sluit funksie verrig en dan word daar oorgeslaan na ’n nouband filter vir fase volging wat die ruis in die terugvoerlus verminder. Daar is ’n simbool sluit detektor wat identifiseer wanneer die simbool beheerlus gesluit is en selekteer dan die gepaste filter. ’n Tweede DDS en ’n sintetiseerder se uittrees word gemeng om ’n 1.44 GHz draer te genereer vir kohurente frekwensie translasie in die kwadratuur menger. Die draer sinkronisasie gebruik ’n numeries beheerbare ossilator vir die inisiële frekwensie en fase sluit wat baie vinnig geimplenteer kan word omdat dit alles in sagteware binne in die FPGA gebeur. Na die interne draer beheerlus gesluit is, neem die eksterne beheerlus oor om enige fase of frekwensie afsette in die kompleks basisband seine van die kwadratuur menger te verwyder deur die frekwensie van die draer DDS te beheer. ’n QPSK modulator is ook ontwikkel om verwysings data te genereer. Enige konstelasie vorm tot 256 punte kan geimplementeer word.

La demande constante de capacité et la saturation prévue de la fibre monomode ont conduit récemment à des avances technologiques qui ont complètement changé le paysage des télécommunications à fibre optique. Le progrès le plus important était la mise en œuvre d'une détection cohérente à l'aide d'électronique rapide. Cela a permis pas seulement l'utilisation de formats de modulation qui promettent une utilisation plus efficace de la bande passante, mais aussi l’utilisation des algorithmes adaptés pour combattre la dégradation du signal optique due à la propagation. Cette thèse a commencé un peu après le début de cette « ère du cohérent » et son principal objectif était de revoir les effets physiques de la propagation dans des systèmes de transmission terrestres, utilisant le format de modulation QPSK (Quadrature Phase Shift Keying). Le manuscrit est divisé en deux parties. La première partie est consacrée à une étude sur les séquences des données qui doivent être utilisés dans les simulations numériques, lorsqu’un format de modulation avancée est impliqué. La propagation, et en particulier l'interaction entre la dispersion chromatique et les non-linéarités, introduisent une interférence inter-symbole (ISI). Vu que cet ISI dépend de l’enchainement des données transmises, il est évident que le choix de la séquence a une influence sur la qualité estimée du canal. Etant donné que des séquences aléatoires infinies ne sont pas pratiquement réalisables, nous utilisons souvent des séquences « pseudo-aléatoires » (PR), i.e. des séquences déterministes de longueur finie, avec des statistiques équilibrés, qui semblent être aléatoires. Dans la première partie, nous décrivons la méthode de génération de séquences PR avec M. niveaux (M> 2) et nous détaillons leurs propriétés. En outre, nous proposons des outils numériques pour caractériser les séquences non pseudo-aléatoires qu’on utilise souvent dans des simulations, ou parfois aussi dans des expériences au laboratoire. Enfin, nous présentons les résultats de simulations qui permettent de quantifier la nécessité d'utiliser des séquences PR en fonction des paramètres du système. Après avoir établi les séquences finies "les plus adaptées", dans la seconde partie du manuscrit, nous nous concentrons sur l'étude de la propagation, dans le contexte d'un système de transmission QPSK et en supposant une gestion de dispersion et un type de fibre variables. Plus précisément, nous étudions numériquement les statistiques de signaux dégradés dus à l'interaction de la dispersion chromatique avec les effets non linéaires, en négligeant tout effet de polarisation ou inter-canaux, aussi que le bruit des amplificateurs. Dans ce contexte, nous étions intéressés à déterminer si certaines lois empiriques développées pour les systèmes OOK, sont valable dans le cas d'une modulation QPSK, tels que le critère de la phase non-linéaire cumulée (ΦNL) ou des lois qui permettent une optimisation de la gestion de dispersion. Ensuite, nous révélons l'importance de la rotation de la constellation du signal initial, comme un paramètre qui peut fournir des informations pour la post-optimisation de notre système. Nous discutons également autour du fait que la forme de la constellation dépend de la gestion de dispersion et concernant les constellations nous concluons qu'il y en a généralement 3 types, avec: (1) une variance de phase supérieure à la variance d'amplitude (2) une variance d'amplitude supérieure à la variance de phase et (3) avec le signal ayant une constellation qui ressemble à la constellation d’un signal sous l'influence d'un bruit blanc gaussien additif. Enfin, nous fournissons une explication phénoménologique des formes des constellations révélant le fait que des sous-séquences différentes conduisent à un « type » différent de dégradation et nous utilisons ces informations pour définir un paramètre qui quantifie le bénéfice potentiel d'un algorithme de correction du type MAP(Maximum A Posteriori Probability) / The constant demand for capacity increase, together with the foreseen saturation of the single-mode optical fiber, paved the way to technological breakthroughs that have completely changed the landscape of fiber-optic telecommunications. The most important advance was, undeniably, the practical implementation of a coherent detection with the help of high-speed electronics. This has, first, enabled the use of advanced modulation formats that allowed for a more efficient use of the fiber bandwidth, compared to the classical On-Off Keying, while adapted algorithms could not be used in order to mitigate the optical signal degradation. This thesis began a little after the advent of coherent detection and its main objective was to revisit the propagation effects in optical transmission systems using "Quadrature phase shift keying" (QPSK) modulation in the context of terrestrial systems, i.e. for transmission distances of up to about 2000 km. The manuscript is divided into two parts. The first part is dedicated to a study on the data sequences that need to be used in numerical simulations, when advanced modulation is involved. Fiber propagation, and in particular the interplay between chromatic dispersion and nonlinearities, usually introduce a nonlinear inter-symbol interference (ISI) to the transmitted signal. Since this ISI depends on the actual transmitted data pattern, it is obvious that the choice of the sequence used in our numerical simulations will have a direct influence on the estimated channel quality. Since, an infinite length, random sequence is impractical; we very commonly use pseudorandom" (PR) sequences, i.e. finite-length, deterministic sequences with balanced pattern statistics that seem to be random. In the first part we describe the method of generating M-level (with M>2) pseudorandom sequences and we detail their properties. In addition, we propose numerical tools to characterize the non-pseudorandom sequences that we use in numerical simulations, or we are sometimes forced to use in laboratory experiments. Finally, we present results of numerical simulations that quantify the necessity to use PR sequences as a function of our system parameters. After having established the “fairest possible” finite sequences, in the second part of the manuscript, we focus on the study of the nonlinear propagation, in the context of a transmission system using QPSK modulation and assuming a variable dispersion management and fiber type. Specifically, we numerically study the signal statistics due to the interplay of chromatic dispersion and nonlinear effects, neglecting all polarization or multi-wavelength effects and the amplifier noise. In this context, we were first interested in determining whether some empirical laws developed for OOK systems, can be also used in the case of QPSK modulation, such as the criterion of cumulative nonlinear phase (ΦNL) or laws that allow for a quick optimization of the dispersion management. Next we reveal the importance of a global phase rotation added to the initial signal constellation, as a parameter that can provide interesting information for the post-optimization of our system. We also discuss the fact that the constellation shape critically depends on the applied dispersion management, while there are generally 3 types of constellations, concerning the complex signal statistics: (1) the phase variance is higher than the amplitude variance (2) the amplitude variance is higher than the phase variance and (3) the received signal constellation resembles to a constellation of a signal under the influence of just an Additive White Gaussian Noise. Finally, we provide a phenomenological explanation of the constellations shapes revealing the fact that different data sub-sequences suffer from a different kind of signal degradation, while we also use this information to define a parameter that quantifies the potential benefit from a MAP (Maximum A Posteriori probability) correction algorithm

No description available.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Advances in spectrally efficient Feher’s Quadrature Phase Shift Keying (FQPSK) and Feher‘s Quadrature Amplitude Modulation (FQAM) patented technologies, commercial and government “dual-use” FQPSK products and Test & Evaluation (T&E) results are highlighted in this overview paper. US and international customer requirements/systems, programs and recent deployments and standardization programs are also described. FQPSK doubles the spectral efficiency of PCM/FM Telemetry and of Feher patented Gaussian Minimum Shift Keying (GMSK or FGMSK) and of alternatives, while FQAM quadruples the spectral efficiency of these systems. The predominant focus of this presentation is on an overview and advances of IRIG 106-00 standardized FQPSK technologies. FQAM systems will also be described. Use of FQPSK for applications such as telemetry, data links, clear mode, TDMA ,CSMA and CDMA, OCDMA, WCDMA as well as OFDM – COFDM will be included in the presentation.

No description available.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Bit errors often occur in a wireless communications link when impairments alter the transmitted signal. It is advantageous to be able to predict how well a system will tolerate transmission problems. This paper details laboratory performance measurements and comparisons in terms of evaluating configurations of a digital receiver for Feher patented Quadrature Phase Shift Keying (FQPSK-B) demodulation. The transmitted signal is subjected to calibrated levels of impairments while the receiver performance is monitored in real-time.