International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Design and performance evaluation of a low-complexity equalizer for recently standardized spectral efficient Feher patented quadrature phase shift keying (FQPSK) system [1] over multipath fading channel is presented. The implementation based on a Feher patented equalizer (FE) [1] is of a structure with three branches, which are individually used to compensate for a moving fade notch with different locations. These branches are switched by the control signal that is generated based on pseudo-error on-line detection technique. It is demonstrated that for typical aeronautical telemetry RF frequency selective fading channels, having delay spreads in 20 – 200 ns range, the adaptive FE reduces the number of statistical outages by more than 60% without the need for training bits and without increasing the receiver synchronization time.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / When designing transmitters for quadrature modulation schemes, the designer always tries to achieve good balance and symmetry of the in-phase (I) and quadrature (Q) branches of the modulator in terms of amplitude, phase, and offsets. Perfect balance between modulators is ideal but rarely if ever achieved. The Advance Range Telemetry (ARTM) program has placed indirect specifications on the remnant carrier and sideband levels which are controlled by modulator imbalance. These specifications will govern the ARTM programs first generation of Feher’s patented quadrature phase shift keying, version B (FQPSK-B) [9] airborne telemetry transmitters. The ARTM Program has also adopted test procedures for quantifying these modulation imbalances. This paper looks at the effects of modulator imbalances on spectral occupancy and bit error probability of the airborne telemetry link. It also outlines how these imbalances influence the levels in one of the ARTM specifications. Recommendations are presented based on the measured data for higher bit rate telemetry systems.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper describes the design considerations used by Aydin Telemetry in the development of its high data rate Feher Patented Quadrature Phase Shift Keying (FQPSK) [1] frequency agile transmitter. We will address several key areas of interest to the Telemetry community, such as the use of commercially available VLSI parts to minimize parts count while maximizing reliability, adaptive filtering to accommodate a wide range of data rates, and user selectable features to achieve a universal transmitter design. User selectable features include differential encoder, 15 stage IRIG randomizer, and 1/2 rate convolutional FEC coding. This paper also addresses the spectral efficiency that can be achieved using a Class-C amplifier with FQPSK and the measured bit error rate (BER) performance versus Eb/No.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Organizations such as the National Telecommunications and Information Administration (NTIA), Federal Communications Commission (FCC), International Telecommunications Union (ITU) and various commercial entities use a wide range of spectral efficiency criteria in different broadcast and wireless system applications. These criteria and related specifications have significant differences. This paper briefly reviews some common adjacent channel interference (ACI) definitions as well as issues surrounding the definition of spectral efficiency. The impact of these parameters on system bit error rate (BER) performance and closely "packed" adjacent signals is described. ACI criteria and spectral efficiency definitions considered appropriate for existing telemetry applications and deployment of new generations of spectrally efficient systems are illustrated. Specific ACI and spectral efficiency performance requirements adopted by the Department of Defense (DoD) and Advanced Range Telemetry (ARTM) project are highlighted.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / A new constant envelope modulation scheme for OQPSK, called FQPSK-O, is presented. This modulation technique is an extension of the Feher Quadrature Shift Keying (FQPSK) patented technologies, see Ref[l]. This scheme uses cubic spline interpolation to generate very smooth baseband waveforms in order to increase the spectral and power efficiency. Being a constant envelope modulation, FQPSK-O can operate with class C power amplifier without spectrum regrowth. We achieve a more compact spectrum with comparable bit error rate performance. For example, the spectrum of FQPSK-O is 25% narrower than that of GMSK with BT(b)=0.3 and FQPSK-1 with hardlimiter [2] at -40 dB attenuation point. For coherent demodulation under AWGN channel, FQPSK-O has almost the same BER performance as FQPSK-1 with hardlimiter. Both of them are better than GMSK with BT(b)=0.3 for BER < 10^-4. In Rayleigh fading channel, FQPSK-O outperforms GMSK with BT(b)=0.3 by 2 dB. FQPSK-O is an excellent scheme for wireless and satellite communications which require high spectral and power efficiency.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Design, performance Test and Evaluation (T&E) of a novel smart diversity receiver, based on Feher Diversity (FD) patents over multipath, fast dynamic frequency selective fading channels is presented. A hardware simulator for construction of a frequency selective fading channel has been implemented in laboratory to resemble a telemetry aeronautical channel model, namely the two-path channel model. As an illustrative example, the block error rate (BLER) of a 1 Mb/s rate IRIG 106-00 and CCSDS standardized Feher’s patented quadrature phase shift keying (FQPSK) [1][2] with and without diversity in multipath frequency selective fading channels has been tested and evaluated. The experimental results clearly indicate significant performance improvement with the proposed diversity technique even in cases of severely distorted channels.

In this thesis, the author presents and analyzes two 4-dimensional Constant Envelope Quadrature-Quadrature Phase Shift Keying constellations. Optimal demodulators for the two constellations are presented, and one of them was designed and implemented by the author. In addition, a novel expanded 16-dimensional CEQ2PSK constellation that doubles the number of points without decreasing the distance between points or increasing the peak energy is generated by concatenating the aforementioned constellations with a particular method and restrictions. This original 16-dimensional set of symbols is set-partitioned and used in a multidimensional Trellis-Coded Modulation scheme along with a convolutional encoder of rate 2/3. Effective gain of 2.67 dB over uncoded CEQ2PSK constellation with low complexity is achieved theoretically. A coding gain of 2.4 dB with 8 dB SNR is obtained by using Monte Carlo simulations. The TCM systems and demodulators were tested under an Additive White Gaussian Noise channel by using Matlab's Simulink block diagrams.

Coherent detection employing multilevel modulation formats has become one of the most promising technologies for next generation high speed transmission systems due to the high power and spectral efficiencies. Using the powerful digital signal processing (DSP), coherent optical receivers allow the significant equalization of chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise (PN) and nonlinear effects in the electrical domain. Recently, the realizations of these DSP algorithms for mitigating the channel distortions in the coherent transmission systems are the most attractive investigations. The CD equalization can be performed by the digital filters developed in the time and the frequency domain, which can suppress the fiber dispersion effectively. The PMD compensation is usually performed in the time domain with the adaptive least mean square (LMS) and constant modulus algorithms (CMA) equalization. Feed-forward and feed-back carrier phase estimation (CPE) algorithms are employed to mitigate the phase noise (PN) from the transmitter (TX) and the local oscillator (LO) lasers. The fiber nonlinearities are compensated by using the digital backward propagation methods based on solving the nonlinear Schrödinger (NLS) equation and the Manakov equation. In this dissertation, we present a comparative analysis of three digital filters for chromatic dispersion compensation, a comparative evaluation of different carrier phase estimation methods considering digital equalization enhanced phase noise (EEPN) and a brief discussion for PMD adaptive equalization. To implement these investigations, a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying (NRZ-PDM-QPSK) coherent transmission system with post-compensation of dispersion is realized in the VPI simulation platform. In the coherent transmission system, these CD equalizers have been compared by evaluating their applicability for different fiber lengths, their usability for dispersion perturbations and their computational complexity. The carrier phase estimation using the one-tap normalized LMS (NLMS) filter, the differential detection, the block-average (BA) algorithm and the Viterbi-Viterbi (VV) algorithm is evaluated, and the analytical predictions are compared to the numerical simulations. Meanwhile, the phase noise mitigation using the radio frequency (RF) pilot tone is also investigated in a 56-Gbit/s NRZ single polarization QPSK (NRZ-SP-QPSK) coherent transmission system with post-compensation of chromatic dispersion. Besides, a 56-Gbit/s NRZ-SP-QPSK coherent transmission system with CD pre-distortion is also implemented to analyze the influence of equalization enhanced phase noise in more detail. / QC 20120528

[pt] Nos últimos anos, as bandas de frequências nas comunicações sem fio estão começando a saturar devido ao incremento do tráfego e o aumento dos usuários, é devido a isso que, é necessário estudar as bandas de frequências que não estão sendo utilizadas nas áreas das comunicações como a banda milimétrica e sub-milimétrica. A transmissão de dados na banda EHF o banda milimétrica constitui uma possível solução para conseguir transmitir maiores quantidades de informação a altas velocidades de transmissão aliviando as bandas de frequências atuais. Neste trabalho se estuda a transmissão de dados em frequências de 100, 200, 300 e 400 GHz, empregando a modulação Quadrature Phase-Shift Keying (QPSK) mediante uma arquitetura baseada no batimento de dois lasers, cujas frequências são combinadas em um Beam Splitter, para que a corrente resultante da soma dos campos elétricos dos dois lasers seja convertida em um sinal de alta frequência por meio de uma antena fotocondutora. O batimento dos dois lasers, com diferentes comprimentos de onda e com a mesma potência, ao interagir com uma antena fotocondutora dá como resultado uma frequência na ordem de Gigahertz. No experimento utilizaram-se dois tipos de diodos receptores, um de banda larga (menor que 4 GHz) e outro de banda estreita (menor que 1 MHz). As duas antenas foram testadas em diferentes distâncias e com diferentes frequências de portadora para verificar qual delas tinha o melhor desempenho na banda EHF para poder realizar a transmissão de dados. / [en] In recent years, the frequency bands in wireless communications are beginning to saturate due to the increase of traffic and the increase of users, and it for that reason that is necessary to study the frequency bands that are not begin used in the communication areas like millimeter and sub-millimeters bands. Data transmission in the EHF band is a possible solution to be able to transmit large amounts of information at high transmission speeds, alleviating current frequency bands. In this work, the transmission of data in frequencies of 100, 200, 300 and 400 Gigahertz is studied, using Quadrature phase-shift keying (QPSK) modulation with an architecture based on the beat of two lasers, whos frequencies are combined by means of Beam Splitter, so that result of the electric fields of two lasers is converted into a high frequency signal with the aid of a photoconductor antenna. The.beating of the two lasers, with different wavelengths and with the same power, when interacting with a photoconductor antenna results in a frequency in the order of Gigahertz. In the experiment, two types of receiver diodes were used, one Broadband (less than 4 GHz) and the other of narrowband (less than 1 MHz). The two antennas were tested at different distances and with different carrier frequencies to verify which one had the best performance in the EHF band in order to perform the data transmission.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Shaped Offset Quadrature Phase Shift Keying (SOQPSK) has the advantages of low sidelobes and high detection probability; however, its main lobe has a fixed width set by the number of constellation points. By slightly modifying the modulation scheme, the four constellation points of quadrature shift keying can be changed to M constellation points where M is a power of 2. After this change, the power spectral density (PSD) retains low sidelobes, and the desirable property of being able to detect the signal by integrating over two symbol periods is retained.