Showing papers on "Continuous phase modulation published in 2014"

Polyphase-coded FM (PCFM) radar waveforms, part I: implementation

Abstract: Polyphase radar codes promise enhanced performance and flexibility due to greater design freedom. While the search for better codes continues, the implementation issues of transmitter bandlimiting and nonlinear distortion have precluded their widespread use in high-power systems. This paper introduces a modified continuous phase modulation implementation that converts an arbitrary polyphase code into a nonlinear frequency-modulated waveform that is constant envelope and spectrally well contained. Experimental results assess the receive sampling and pulse compression effects.

Polyphase-coded FM (PCFM) radar waveforms, part II: optimization

Abstract: This paper addresses polyphase code optimization with respect to the nonlinear frequency modulation waveform generated by the continuous phase modulation implementation. A greedy search leveraging the complementary metrics of peak sidelobe level, integrated sidelobe level, and spectral content yield extremely low range sidelobes relative to waveform time-bandwidth product. Transmitter distortion is also incorporated into the optimization via modeling and actual hardware. Thus the physical radar emission can be designed to address spectrum management and enable the physical realization of advanced waveform-diverse schemes.

Discrete-phase-randomized coherent state source and its application in quantum key distribution

Abstract: Coherent state photon sources are widely used in quantum information processing. In many applications, such as quantum key distribution (QKD), a coherent state is functioned as a mixture of Fock states by assuming its phase is continuously randomized. In practice, such a crucial assumption is often not satisfied and, therefore, the security of existing QKD experiments is not guaranteed. To bridge this gap, we provide a rigorous security proof of QKD with discrete-phase-randomized coherent state sources. Our results show that the performance of the discrete-phase randomization case is close to its continuous counterpart with only a small number (say, 10) of discrete phases. Comparing to the conventional continuous phase randomization case, where an infinite amount of random bits are required, our result shows that only a small amount (say, 4 bits) of randomness is needed.

Polarization-independent phase modulation using a blue-phase liquid crystal over silicon device.

Abstract: Liquid crystal over silicon (LCoS) spatial light modulator technology has become dominant in industries such as pico-projection, which require high-quality reflective microdisplays for intensity modulation of light. They are, however, restricted from being used in wider optical applications, such as computer-generated holography, adaptive optics, and optical correlation, due to their phase modulation ability. The main drawback of these devices is that their modulation is based on simple planar or twisted nematic liquid crystals, which are inherently slow mechanisms due to their viscoelastic properties. Their use is also limited due to fact that the phase modulation is dependent on the state of polarization of the illumination. In this paper, we demonstrate that a polymer-stabilized blue-phase liquid crystal can offer both phase modulation and high speed switching in a silicon backplane device which is independent of the input polarization state. The LCoS device shows continuous phase modulation of light with a submillisecond switching time and insensitivity to the input light polarization direction. This type of phase modulation opens up a whole new class of applications for LCoS technology.

A 13 pJ/bit 900 MHz QPSK/16-QAM Band Shaped Transmitter Based on Injection Locking and Digital PA for Biomedical Applications

Abstract: This paper presents a 900 MHz highly digital transmitter capable of providing band shaped QPSK/16-QAM modulation for high data-rate applications with high energy efficiency. Injection-locked ring oscillator is used for multi-phase carrier generation which eliminates the use of power-hungry phase-locked loop. It also provides fast settling time that enables heavy duty cycling to maximize energy conservation. Direct modulation at power amplifier is adopted to simplify the transmitter architecture. Fabricated in 65 nm CMOS, the transmitter achieves maximum data rate of 50 Mbps/100 Mbps for QPSK/16-QAM with effective sideband suppression more than 38 dB. The chip occupies an active area of 0.08 mm and achieves a settling time of less than 88 ns. Under 0.77 V supply, it achieves an energy efficiency of 26 pJ/bit and 13 pJ/bit with and without band shaping respectively. The measured EVM is better than 6% for QPSK (at 50 Mbps) and 16-QAM (at 100 Mbps) while delivering -15 dBm of output power.

LLC performance enhancements with frequency and phase shift modulation control

Abstract: This paper presents an algorithm that uses a combination of frequency modulation (FM) and phase shift modulation (PSM) to enhance both the controllability and efficiency of an LLC dc-dc converter. It will be shown that, the proper “marriage” of FM and PSM will result in the ability to support a wider range of operating conditions without comprising efficiency or control monotonicity. These operating points include but are not limited to: monotonic start up, light load regulation, high input voltage, constant-current and constant-power.

Multistage Carrier Phase Estimation Algorithms for Phase Noise Mitigation in 64-Quadrature Amplitude Modulation Optical Systems

Abstract: Two novel low-complexity multistage digital feed-forward carrier phase estimation algorithms for 64-ary quadrature amplitude modulation (QAM) are proposed and analyzed by numerical simulations. The first stage is composed of a Viterbi and Viterbi block, based on either the standard quadrature phase shift keying (QPSK) partitioning algorithm using only Class-1 symbols or a modified QPSK partitioning scheme utilizing both Class-1 and outer most triangle-edge symbols. The second stage applies the Viterbi and Viterbi algorithm after a 64-QAM-to-QPSK transformation, while the subsequent stages iterate a maximum likelihood estimation algorithm for phase estimation. All proposed techniques are characterized by a high tolerance to laser phase noise: with an optical signal-to-noise ratio penalty of 1 dB at bit error rate of $10^{-2}$ , the proposed schemes can tolerate a linewidth times symbol duration product ( $\Delta {{ u }}\cdot T_{s}$ ) equal to $5.6\times 10^{-5}$ and $7.1\times 10^{-5}$ , respectively. At 32 Gbaud, all of the above linewidth requirements can be met using commercial tunable lasers. The proposed schemes achieve a similar linewidth tolerance with a reduced implementation complexity with respect to algorithms based on the blind phase search method.

Optimization of “over-coded” radar waveforms

Abstract: Polyphase-Coded FM (PCFM) radar waveforms generated using the power and spectrally efficient continuous phase modulation (CPM) framework can be further enhanced through the use of finer time control by subdividing each phase transition into sub-transitions and by allowing a greater phase excursion per transition interval, herein referred to as over-phasing. These two strategies are denoted collectively as “over-coding”. It is shown that various combinations of sub-transitions and over-phasing can greatly improve waveform design capabilities by expanding the available degrees-of-freedom. It is also demonstrated that the commensurate increase in computational complexity for optimization under the over-coding paradigm can largely be offset through GPGPU processing.

Low-complexity SOCPBFSK-OOK interface between PLC and VLC channels for low data rate transmission applications

Abstract: This paper studies and proposes a low cost low complexity interface between power line communications (PLC) and visible light communications (VLC) for low data rate transmission applications. The discussion presents the performance of a spread orthogonal continuous phase binary frequency shift keying (SOCPBFSK) receiver combined with an on-off keying (OOK) modulator to relay low data transmission between PLC and VLC channels. The characteristics of the interface are presented. The results of an experimental test using the proposed interface over the European Committee for Electrotechnical Standardization (CENELEC) bands C and D are presented. The eye diagrams of the combined error are presented as well.

Dual Stage CPE for 64-QAM Optical Systems Based on a Modified QPSK-Partitioning Algorithm

Abstract: In this letter, a novel two-stage digital feed forward carrier recovery algorithm for 64-ary quadrature amplitude modulation (QAM) is proposed and analyzed. Due to the absence of any feedback loop, the approach shows a high tolerance toward laser phase noise. Different steps involving partition, selection, and rotation of symbols are also discussed. For an OSNR penalty of 1 dB at bit error rate of 10-3, the proposed scheme can tolerate linewidth times symbol duration product equal to 3.3×10-5 and hence can be used with the commercially available state-of-the-art tunable lasers for 64-QAM transmission at 400 Gb/s.

Coherent Detection-Based Automatic Bias Control of Mach–Zehnder Modulators for Various Modulation Formats

Abstract: In this paper, a method to automatically control the bias voltages of LiNbO3 Mach–Zehnder modulator (MZM) is proposed and demonstrated experimentally. The automatic bias control (ABC) method is based on low cost coherent detection employing 3 × 3 optical coupler, which enhances the dither detection sensitivity. By minimizing the monitored dither frequency components which represents the residual carrier component in the optical signal, the modulator biases are optimized. A 0–π/2 square-wave phase modulation is introduced to mitigate the detection fluctuation induced by the imbalance of 3 × 3 coupler and improve the monitoring accuracy. Experiments show that the proposed method is universal for different modulation formats. High bias control precision is achieved for inner in-phase/quadrature (I/Q) branches and outer phase bias of optical quadrature modulator. The penalty caused by the proposed ABC is negligible for both single carrier (SC) modulation and optical orthogonal frequency division multiplexing modulation. The tolerance to temperature disturbance is also demonstrated.

Biorthogonal modulation in 8 dimensions experimentally implemented as 2PPM-PS-QPSK

Abstract: We experimentally demonstrate biorthogonal modulation in 8 dimensions as binary pulse-position modulation polarization-switched QPSK. We compare this format with PM-QPSK at the same bit rate and show a 1.4 dB sensitivity gain and 84 % increased transmission distance.

Spatially-modulated radar waveforms inspired by fixational eye movement

Abstract: We consider a class of MIMO radar emissions in which a coherent spatial beam is formed while the direction is modulated during the pulse width. This type of spatial modulation has a direct analog to the rapid, small movements of the human eye during fixation (staring) to enhance contrast and sensitivity to fine detail. To replicate this passive sensing capability of the eye for the active sensing modality of radar we leverage and expand the continuous phase modulation (CPM) framework for code-to-waveform implementation and thereby realize a physical delay-angle coupled emission. Through analysis of a defined angle-delay ambiguity function for specific waveform/spatial modulation examples it is shown that enhanced discrimination is enabled at the cost of some SNR loss, which may be an acceptable tradeoff for some applications.

Distinguishing BFSK from QAM and PSK by sampling once per symbol

Abstract: In this paper we propose a feature to distinguish FSK from QAM and PSK modulations. The feature is based on the imaginary part of product of two consecutive signal values where every symbol is sampled only once. Conditional probability density functions of the feature given the present modulation are determined. Central limit theorem for strictly stationary m-dependent sequences is used to obtain Gaussian approximations. Then the thresholds are determined based on the minimization of total probability of misclassification. Effects of AWGN, carrier offset and non-synchronized sampling on the performance are studied. Proposed classifier is compared to the maximum likelihood classifier.

A Phase-Reconstruction Technique for Low-Power Centimeter-Accurate Mobile Positioning

Abstract: A carrier phase reconstruction technique is presented as an enabler for low-power centimeter-accurate mobile positioning. Reliable carrier phase reconstruction permits the duty cycling of a Global Navigation Satellite System (GNSS) receiver whose outputs are used for precise carrier-phase differential GNSS (CDGNSS) positioning. Existing CDGNSS techniques are power intensive because they require continuous tracking of each GNSS signal's carrier phase. By contrast, the less-precise code-ranging technique that is commonly used in mobile devices for 3-to-10-meter-accurate positioning allows for aggressive measurement duty-cycling, which enables low-power implementations. The technique proposed in this paper relaxes the CDGNSS continuous phase tracking requirement by solving a mixed real and integer estimation problem to reconstruct a continuous carrier phase time history from intermittent phase measurement intervals each having an ambiguous initial phase. Theoretical bounds on the probability of successful phase reconstruction, corroborated by Monte-Carlo-type simulation, are used to investigate the sensitivity of the proposed technique to various system parameters, including the time period between successive phase measurement intervals, the duration of each interval, the carrier-to-noise ratio, and the line-of-sight acceleration uncertainty. A demonstration on real data indicates that coupling a GNSS receiver with a consumer-grade inertial measurement unit enables reliable phase reconstruction with phase measurement duty cycles as low as 5%.

Bit Erro r Rate Analysis in Simulation of Digital Communication Systems with Different Modulation Schemes

Abstract: With the increasing demand in communication, it has become necessary to give better and efficient service to users by using better technique. This paper analyse the bit error rate, for different modulation schemes such as Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK. By Choosing a reliable modulation scheme and better coding technique the enhancement of the performance can be obtained in transmitter and receiver of the system. Simulated result is shown to analyse and compare the performance of these systems by using additive white Gaussian noise channel (AWGN). Finally the different modulation schemes are compared on the basis of BER and best modulation scheme is determined. From analysis of two modulation techniques, the system could use more appropriate modulation technique to suit the channel quality, thus we can deliver the optimum and efficient system parameters. LabVIEW has been used for simulation.

Design of Unstructured and Protograph-Based LDPC Coded Continuous Phase Modulation

Abstract: In this paper, we derive an asymptotic analysis and optimization of coded CPM systems using both unstructured and protograph-based LDPC codes ensembles. First, we present a simple yet effective approach to design unstructured LDPC codes : by inserting partial interleavers between LDPC and CPM, and allowing degree-1 and degree-2 variable nodes in a controlled pattern, we show that designed codes perform that can operate very close to the maximum achievable rates. Finally, the extension to protograph based codes is discussed. We provide some simple rules to design good protograph codes with good threshold properties.

A modified QPSK modulation technique for direct antenna modulation (DAM) systems

Abstract: Direct antenna modulation (DAM) has been proposed to overcome the bandwidth limitation of high Q resonating antennas by decoupling the stored energy from the coupled or radiated energy. It, however, due to its switching nature, imposes a zero voltage or zero current switching condition to the modulation technique at the symbol transition in order to achieve high radiation efficiency. Simple on-off keying (OOK) based on monocycle RF pulses was used in the past. In this paper, higher order phase shift keying modulation techniques are proposed for DAM systems. The so-called modified QPSK modulation technique can maintain zero current switching conditions at the symbol transitions while creating the four quadrant phases to represent different symbols. Simulations for a near field communication (NFC) system employing such modulation techniques have demonstrated better transmission performance judged by the eye diagrams.

An all-pass topology to design a 0–360° continuous phase shifter with low insertion loss and constant differential phase shift

Abstract: In this paper, an analog phase shifter is designed by using a novel all-pass topology. The phase shift can be continuously adjusted from 0 up to 380° by biasing varactor-diodes while maintaining the differential phase shift constant across the 6.7 GHz - 7.7 GHz band. This two-stage circuit is simple and compact with respectively insertion losses of 2.9 dB +- 1.3 dB, return losses better than 9.4 dB and a differential phase shift flatness of +- 11° in the worst case. With a 90.5°/dB Figure-of-Merit, this topology presents an interesting trade-off between low-cost, low loss, large phase-shift range, phase flatness and bandwidth. Measurements are discussed and carefully compared to current competing topologies.

Multi-dimensional permutation modulation aiming at both high spectral efficiency and high power efficiency

Abstract: We analyze the performance of multi-dimensional permutation modulation formats. With the increase in the dimension of modulation, their spectral efficiencies can approach the Shannon limit even when their power efficiencies are kept high.

Carrier phase estimation for 16-QAM optical coherent systems using QPSK partitioning with barycenter approximation.

Abstract: This paper presents a hardware-efficient carrier phase estimator with high-linewidth tolerance for 16-QAM optical coherent systems. The laser phase noise is estimated using quaternary phase-shift keying (QPSK) partitioning complemented with a low complexity angle-based barycenter approximation as opposed to the classical Viterbi and Viterbi algorithm. The various stages necessary for partitioning and removing the modulation on the received symbols for carrier phase recovery are presented. We show that the phase offset in the middle ring for a 16-QAM constellation can be removed through a simple comparison with the symbols lying on the inner and outer rings of the constellation thus enabling all the symbols to be efficiently utilized for carrier phase recovery. We assess the performance of different filter structures for 16-QAM with filter half width 8 and 16. Simulation results demonstrate that combined linewidth symbol duration product $\Delta u \cdot T_s$ of $10^{-4}$ is tolerable at the target BER of $10^{-2}$ and $10^{-3}$ when using the barycenter algorithm. Finally, carrier phase recovery in a 16-QAM experiment is investigated to validate the performance of the proposed algorithm.

A low complexity coherent CPM receiver with modulation index estimation

Abstract: In this paper we address the problem of low-complexity coherent detection of constant phase modulation (CPM) signals. We exploit the per-survivor-process technique to build a reduced-state trellis and apply a Viterbi algorithm with modified metrics. In the case where the modulation index can vary, we propose a maximum-likelihood (ML) estimation of the modulation index and compare the performance of the resulting structure with a non-coherent receiver structure of the state of the art. Simulations on an additive white Gaussian noise (AWGN) channel both for binary and M-ary CPM show the efficiency of the proposed receiver.

Non-coherent detection of GFSK using Extended Kalman Filtering for Non-Gaussian noise

Abstract: Gaussian Frequency Shift Keying (GFSK), a special case of Continuous Phase Modulation (CPM) schemes, is the modulation scheme chosen for achieving basic data rate of 1 Mbps with Bluetooth receivers. In this article, we present a new non-coherent demodulation technique based on the Extended Kalman Filter (EKF) that does not require the knowledge of the modulation index to detect the GFSK modulated signal in Bluetooth receivers. The paper examines the performance of our proposed receiver in the presence of Non-Gaussian impulsive noise since this type of noise is considered to be a severe noise for wireless technologies including Bluetooth. Bit Error Rate (BER) was used as the measurement metric for the performance for our proposed receiver at the physical level while Packet Error Rate (PER) and Residual Bit Error Rate (RBER) were used as the measurement metrics at the system level. Experimental results obtained for the Extended Kalman Filter detector for Non-Gaussian noise are provided.

Statistical properties proposed for blind classification OFDM modulation scheme

Abstract: Classification of modulation scheme, previous step before demodulation, is the main part of an intelligent receiver at military or commercial application. Moreover, without definite parameters of the transmitted signal, blind modulation classification becomes a difficult task. Modulation classification becomes more challenging in real application with multicarrier modulation at fading channel. Furthermore, in recent years, the wireless communication has concerned to the orthogonal frequency division multiplexing (OFDM) because of spectral efficiency by using orthogonal multicarrier modulation. In this paper, we provided statistical characteristics of different modulation schemes from the OFDM signal with multipath (Rayleigh) fading channel. Based on standard of IEEE 802.16e, there are three possible modulation schemes used like a Quadrature Phase Shift Keying (QPSK), 16-QAM (Quadrature Amplitude Modulation), and 64-QAM. We analyzed those three modulation schemes by using statistical properties, such as, mean, variance, skewness, kurtosis and moment order.

Optimum discrete single group multicast beamforming

Abstract: In this paper, transmit beamformer design for single group multicast scenario is considered. The problem is solved in discrete form where the beamformer phase and amplitude val- ues are selected from finite discrete sets. Original optimiza- tion problem is converted to a linear form by introducing new variables. The solution of the equivalent optimization prob- lem is always feasible as long as the total power is above a certain value. The problem in its linear form is guaranteed to return optimum solution. Proposed approach is very effec- tive and the number of bits can be increased to obtain close to optimum continuous phase and amplitude beamformers.

Accelerating the averaging rate of atomic ensemble clock stability using atomic phase lock

Abstract: We experimentally demonstrated that the stability of an atomic clock improves at its fastest rate ? ?1 (where ? is the averaging time) when the phase of a local oscillator is genuinely compared to the continuous phase of many atoms in a single trap (an atomic phase lock). For this demonstration, we developed a simple method that repeatedly monitors the atomic phase while retaining its coherence by observing only a portion of the whole ion cloud. Using this new method, we measured the continuous phase over three measurement cycles, and thereby improved the stability scaling from to ? ?1 during the three measurement cycles. This simple method provides a path by which atomic clocks can approach a quantum projection noise limit, even when the measurement noise is dominated by the technical noise.

Light-receiving device and phase cycle slip reduction method

Abstract: This light-receiving device, which receives an optical signal which has been modulated by means of phase modulation or quadrature amplitude modulation, converts the received optical signal into an electric signal by means of coherent detection, and applies phase compensation to the converted received signal, has: a carrier phase estimation section that estimates a carrier phase error in a received symbol string obtained from the received signal; a gain adjustment section that executes a gain adjustment of the symbols input to the carrier phase estimation unit; a phase cycle slip reduction section that detects coarse noise causing a phase cycle slip through statistical processing of outputs from the carrier phase estimation unit and reduces the phase cycle slip; and a phase compensation circuit that uses the outputs of the carrier phase estimation unit to compensate for the carrier phase error contained in the received signal.

Frequency-domain Equalization Techniques for Multi-h Continuous Phase Modulation

Abstract: Two receiver architectures are presented for equalization of multi-h continuous phase modulation (CPM). In the first approach, the receiver front end is a matched-filter bank, which is derived from Laurent decomposition of the signal. A circulant-matrix model derived for the samples of the matched filter is used to perform the equalization in frequency domain. The second technique employs a receiver with a simple front end consisting of a low-pass filter and a fractional sampler. We also develop a circulant matrix model for the latter approach, which relates the Laurent pseudo-symbols to each polyphase component at the output of the sampler. A linear frequency-domain equalizer (FDE) is also proposed using this model. In addition to providing the details of these approaches, the paper proposes several simplifications applicable to each of the two cases, and provides a detailed discussion on the performance/complexity trade-off. Bit-error rate (BER) results are presented for the IRIG-106 aeronautical telemetry dual-h CPM waveform.

2pi low drift phase detector for high precision measurements

Abstract: In modern particle accelerators, radio frequency (RF) phase detectors have to fulfill high demands on stability and accuracy to meet the goals of state-of-the-art synchronization systems. Especially challenging are those cases where the RF signal phase shift accuracy must be measured with fs accuracy for several hours over the full $2 {\pi }$ phase detection range. In these cases special measures on the component’s nonlinearities and RF channel isolation have to be taken. The long-term stability of the phase detector is mostly affected by temperature and humidity variations. To meet the synchronization goals, we have built a phase detector that incorporates a high-speed dual analog-to-digital converter (ADC) with a special circuit for continuous phase drift calibration. In the calibration circuit we successfully combined the RF signal with an RF calibration signal (second tone) to compensate common phase drift that occurs in the microstrip lines, the RF transformers, and the ADC. The second-tone RF signals are directly converted to the digital domain by the fast ADC and, based on signal processing in the field-programmable gate array, are used to calculate the RF signal phase shift correction caused by detector drifts. In this paper, potential error sources of the analog and the digital part of the so-called two-tone calibration technique that limit the phase detector precision are discussed. Finally, the experimental results are presented showing a long-term phase measurement stability better than 0.01 $\ ^\circ \hbox {pk}-\hbox {pk} $ evaluated at an RF frequency of 1.3 GHz over a few days.