Showing papers on "Continuous phase modulation published in 2008"

Coherent optical communication systems

Abstract: Publisher Summary This chapter reviews the theory of multilevel modulation formats that permit multiple bits/s of data per Hz of bandwidth and evaluates the results of recent developments on the digital coherent receiver. The fundamental concept behind coherent detection is to take the product of electric fields of the modulated signal light and the continuous-wave local oscillator (LO). Outputs from the homodyne phase/polarization diversity receiver are processed by digital signal processing (DSP) circuits, restoring the complex amplitude of the signal in a stable manner despite of fluctuations of the carrier phase. Hereafter, such receiver is called the digital coherent receiver. The chapter investigates the digital coherent receiver where the carrier phase is estimated with DSP, alleviating locking the phase of the LO to the carrier phase in the conventional homodyne receiver. It has been found that the phase noise of state-of-the-art semiconductor distributed feedback (DFB) lasers is substantially small such that an accurate phase estimate can be obtained from the sampled signal to demodulate M-ary PSK signals up to eight phase states at the symbol rate of 10 Gsymbol/s.

Methods for Ultra-Wideband Pulse Generation Based on Optical Cross-Polarization Modulation

Abstract: Optical methods for different type ultra-wideband (UWB) pulse generation based on cross-polarization modulation (CPM) are proposed and demonstrated in this paper. Two polarity-reverse pulses can be obtained by CPM and birefringence time delay to form a monocycle pulse. A semiconductor optical amplifier (SOA) is placed after the monocycle pulse process for doublet pulse generation. These two kinds of pulses can be employed in single-band impulse radio UWB (IR-UWB) systems. Two kinds of multi-band UWB pulses can be generated based on monocycle pulse train with proper apodization profiles, realized by hybrid photonic microwave filter and synchronous polarization modulation respectively. Experimental results show that these pulses can be used in multi-band UWB (MB-UWB) over fiber systems.

On enhancing hierarchical modulation

Abstract: Hierarchical modulation offers an important coverage/throughput tradeoff for wireless communication, however it has received relatively little attention to date. Regular hierarchical modulation suffers from the interference between layers. It results in both achievable capacity decrease and bit- error rate increase. In this paper, an enhanced hierarchical modulation technique along with three optimization schemes, in which the enhancement-layer signal constellation is rotated, are presented and analyzed. The first optimization scheme is proposed to maximize the achievable spectral efficiency with rotating the enhancement-layer signal constellation. The second scheme is proposed to lower the demodulation symbol-error rate with maximizing the modulation efficiency and asymptotic modulation efficiency. The parameters, modulation efficiency and asymptotic modulation efficiency, are formulated for quantizing inter-layer interference. The last one is proposed to maximize RF power amplifier efficiency with reducing the peak-to-average- power ratio of modulated symbols. This perspective is especially important for multi-carrier communications. All proposed schemes are simple and efficient. They can help recover the performance loss of regular hierarchical modulation due to inter-layer interference with little complexity increase. Computer simulations are provided to support our conclusions.

Enhanced telemetry system using CP-QPSK Band-Pass modulation technique suitable for smart pill medical application

Abstract: A new approach of continuous phase QPSK Band-Pass modulation technique is being developed as enhancement to the QPSK modulation scheme for inductive data transmission (NFC). The modulation is based on Gaussian filtering of the phase transition from one state to the other rather than discontinuity in phase shift. The carrier is based on low frequency 115 KHz suitable for human body energy penetration due to its large skin-depth and lower inductive power attenuation. The complete signal processing is done digitally, external coil and capacitor is used for transceiver interface. The telemetry assists a smart pill swallowed by human being to trigger an actuator for drug delivery, record temperature, or perform diagnostic task inside the body. The smart pill includes 32bit processor, 16 Kbyte memory, temperature sensor, telemetry unit, and additional external peripheries. The complete system is designed, embedded in one SoC, and realized on ASIC with chip-area less than 14 mm2.

Robust Modulation Methods and Smart Antennas in Wireless Communications

Abstract: 1. In Pursuit of Bandwidth Efficiencies for Wireless Terrestrial and Satellite Communications. Introduction. 2. Bandwidth-Efficient Modulation Techniques. Introduction. Bandwidth and Power Efficiency Plane. Conclusions. References. 3. Higher Order Modulation Methods. Introduction. Signal State Space Diagrams. Performance Representations. Conclusions. Glossary of Terms. References. 4. Dynamics of Linear and Continuous Phase Modulation Methods in Digital Communications. Introduction. Linear Modulation. Continuous Phase Modulation. Phase Trellises in CPM. GMSK Modulation. Tamed Frequency Modulation (TFM). Signal Orthogonality. Conclusions. References. 5. Error Control Coding. Introduction. Code Families. Code Performance. Block Coding. Convolutional Encoding. Concatenated Coding. Interleaving. Coding Break-through. Conclusions. References. 6. Trellis Coded Modulation (Codulation). Introduction. The Theory. Attributes of Trellis Coded Modulation. Practical Systems. Performance Degraders. Conclusions. Glossary of Terms. References. 7. Spread Spectrum Communication Systems. Introduction. Spread Spectrum Techniques. Code Generation. Codes for Spread Spectrum Multiplexing. Spread Spectrum Interference Analysis. The Multipath Phenomenon. Purely Random or Pseudo-Random- What's the Difference? Conclusions. Glossary of Terms. References. 8. Terrestrial-based Wireless Communications. Introduction. Frequency Bands of Operation. Interference Analysis. Increasing Capacity. Cellular Standards. Personal Communications Service. Conclusions. References. 9. The Butler Matrix. Introduction. Planar Array Beams. Multiple Volumetric Beams. Butler Array Application. Conclusions. References. 10. Sidelobe Cancellers in Smart Antenna Applications. Introduction. Single Interferer Sidelobe Canceller. Multiple Interferers. Conclusions. References. 11. A Look at Switched-Beam Smart Antennas. Introduction. Trunking Efficiency. Smart Antennas. Configurations. Conclusions. References. 12. Deterministic Signals, Random Noise, and Coherent Noise (Pseudo) Combining in an Array Antenna. Introduction. Coherent Signals. Coherent Noise. An Adaptive Array in a Quiescent Signal Field. 13. Adaptive Arrays in Cellular Communications. Introduction. The Theory. Simulation Results. Conclusions. References. 14. Summary Smart Antennas in Cellular Communications. Introduction. Adaptive Array Genre. Where Are Smart Antennas Going? Conclusions. A. Gaussian Low-Pass Filter. B. Scattering Matrix of the Quadrature Hybrid. C. Example of Trunking and Erlang Tables. D. Glossary of Terms. Index. The Author.

Liquid Crystal Optical Phase Plate with a Variable In-Plane Gradient

Abstract: We propose a nematic liquid crystal (LC) optical phase plate, with a large continuous in-plane gradient that is variable, and its application to a beam steering device with high efficiency. The device is a vertically aligned, continuous phase, optical phased array (V-COPA) that uses a negative dielectric anisotropy LC material. High steering efficiency of over 95% is demonstrated by modeling the LC director field and its effect on transmitted light. The period of the V-COPA grating can be varied by adjusting an applied voltage profile, which allows for continuous angular control of the diffraction angle.

Near Optimal Common Detection Techniques for Shaped Offset QPSK and Feher's QPSK

Abstract: A detector architecture capable of detecting both shaped offset quadrature phase shift keying (SOQPSK-TG) and Feher's quadrature phase shift keying (FQPSK-JR) is developed and analyzed. Both modulations are embodied as fully interoperable modulations in the Interrange Instrumentation Group (IRIG) standard IRIG-106. It is shown that the common detector achieves near optimal bit error rate performance without knowledge of which modulation is used by the transmitter. The detection techniques are based on a common trellis-coded modulation representation and a common continuous phase modulation (CPM) representation for these two modulations. In addition the common pulse amplitude modulation (PAM) decomposition of the common CPM representation is developed. The common PAM-based detector offers the best performance- complexity trade-off among the detectors considered.

PAM representation of ternary CPM

Abstract: This letter considers the pulse amplitude modulation (PAM) representation of continuous phase modulation (CPM) with a ternary data alphabet. This technique is applied to the problem of constructing reduced-complexity detectors with near-optimum performance. The usefulness of this approach is demonstrated using the ternary CPM variant known as shaped-offset quadrature phase-shift keying (SOQPSK).

Continuously phase-matched terahertz difference frequency generation in an embedded-waveguide structure supporting only fundamental modes

Abstract: We demonstrate an all-single mode structure which enables continuous phase matching of difference frequency generated THz light from the near-IR This structure provides a long interaction length by way of well-confined collinear propagation of pumps and product without diffraction, resulting in high conversion efficiency A LiNbO3 version of this structure achieved a power-normalized conversion efficiency of 13×10-7 W-1 - some 23 times larger than the largest previously reported results

Robust Frequency Hopping for Interference and Fading Channels

Abstract: A robust frequency-hopping system with noncoherent detection, iterative turbo decoding and demodulation, and channel estimation is presented. The data modulation is the spectrally compact nonorthogonal continuous-phase frequency-shift keying, which strengthens the frequency-hopping system against multiple-access interference and multitone jamming. An analysis based on information theory provides the optimal values of the modulation index when there is a bandwidth constraint. The channel estimator, which is derived by applying the expectation- maximization algorithm, accommodates both frequency-selective fading and interference. Simulation experiments demonstrate the excellent system performance against both partial-band and multiple-access interference.

A group of modulation schemes for adaptive modulation

Abstract: Adaptive modulation increases the throughput of a wireless network by adjusting the modulation scheme to the channel status. To have more capacity and more flexibility in using adaptive modulation, our research attempts to find a group of modulation schemes, which includes M-QAM where the number of signal points is not a power of 2, as well as non-squared QAM (or APSK: amplitude and phase-shift keying), so we can have n-bit modulation where n ranges fully from 1 to 6 including half-integer indices. Some recent research has shown that the gap between QPSK and 16-QAM, 16-QAM and 32-QAM, 32-QAM and 64-QAM can be filled smoothly by introducing 12-QAM, 24-QAM and 48-QAM. But the gap between QPSK (4-QAM) and 12-QAM is still an open problem. In this paper we insert 8-ary modulation schemes, and propose 6-ary modulation schemes. Simulation results show that our proposed group can fill smoothly the gap between QPSK and 12-QAM.

An easy-to-realize method and device for full digital frequency conversion

Abstract: The invention discloses an all digital frequency converting method and a device thereof, being easily realized for hardware. The method and the device are essentially used for sample rate convertion of rational number-times of baseband signals and the convertion of the baseband signals and the intermediate frequency signals in digital communication. Under the coordination of control signals and enabling signals, the convertion of signal sample rate can be finished and the convertion of the baseband signals and the intermediate signals can be finished through the reasonable matching of variable integral number-times wave filtering and fraction-times interpolation. The system of the invention essentially comprises a frequency mixer, a cascade connection integral comb filter, a fraction-time interpolating device, a half-band filter, a signal shaping filter, a power detection module and a control interface. The configurable hardware implemented structure of the invention is applicable to a plurality of modulation methods, has the advantages of low resource consumption and good portability, and is used for various wireless communication systems such as multilevel phase shift keying (MPSK), orthogonal frequency division multiplex (OFDM), direct sequence spread spectrum (DSSS) and continuous phase modulation (CPM), etc.

Low-power Tx module for high-resolution continuous programmable phase shift

Abstract: A novel phase shifter topology for digital phased antenna arrays based on a low-power phase control block joint with an innovative PLL design is presented. Experimental results obtained by a prototype are reported validating the architecture capabilities.

Characterizing an Image Intensifier in a Full-Field Range Imaging System

Abstract: We are developing a high precision full-field range imaging system. An integral component in this system is an image intensifier, which is modulated at frequencies up to 100 MHz. The range measurement precision is dictated by the image intensifier performance, in particular, the achievable modulation frequency, modulation depth, and waveform shape. By characterizing the image intensifier response, undesirable effects can be observed and quantified with regards to the consequence on the resulting range measurements, and the optimal operating conditions can be selected to minimize these disturbances. The characterization process utilizes a pulsed laser source to temporally probe the gain of the image intensifier. The laser is pulsed at a repetition rate slightly different to the image intensifier modulation frequency, producing a continuous phase shift between the two signals. A charge coupled device samples the image intensifier output, capturing the response over a complete modulation period. Deficiencies in our measured response are clearly identifiable and simple modifications to the configuration of our electrical driver circuit improve the modulation performance.

A New Symbol Block Construction for CPM with Frequency Domain Equalization

Abstract: We present a new symbol block construction which yields a cyclic continuous phase modulated (CPM) signal to enable frequency domain equalization. It is known that in addition to a cyclic prefix, a subblock of data-dependent symbols has to be inserted in each block to cope with the memory in the CPM signal. We propose a new subblock, called intrafix, valid for any CPM scheme. Our intrafix is shorter than what is currently known in the literature, reducing the overhead. Moreover, it can be calculated on a per-block basis, without knowledge of previous blocks. We also prove that there are constraints on the length of both the intrafix and the total block by studying the influence of the modulation index. Simulation results in a 60 GHz environment show that our new block construction satisfies all requirements.

Use of Sliding-Mode Modulation in Switch-Mode Power Amplification

Abstract: This paper presents a recently developed feedback modulation scheme called sliding-mode modulation. Sliding-mode modulation, operating in sliding mode, simultaneously minimizes the accumulated quantization error and in-band modulation error while converting a continuous input signal into a coarsely quantized signal. With these minimization mechanisms, the modulator exhibits simple tractable behavior in the sliding mode and high in-band linearity in signal conversion. These two distinct properties make sliding-mode modulation an attractive substitute for other modulation schemes such as pulsewidth modulation and sigma-delta modulation. A simple method is presented for designing sliding-mode modulators. Moreover, a class-D audio power amplifier with three-level sliding-mode modulation is designed to demonstrate the practicality and superiority of this modulation technique.

Spectrally-efficient continuous phase modulations

Abstract: We investigate the spectral efficiency of continuous phase modulations (CPMs). To this end, we need an effective bandwidth definition for a CPM signal, whose power spectral density has in principle an infinite support. The definition we adopt is based on the spacing between adjacent carriers in a frequency division multiplexed CPM system. We consider the inter-channel interference, that depends on the channel spacing, and we evaluate the spectral efficiency achievable by a single- user receiver in the considered multi-channel scenario. We then optimize the channel spacing with the aim of maximizing the spectral efficiency, showing that impressive improvements with respect to the spectral efficiency achieved without optimizing the channel spacing can be achieved. I.

Simplified receiver design for STBC binary continuous phase modulation

Abstract: Existing space-time codes have focused on multiple- antenna systems with linear modulation schemes such as phase- shift keying and quadrature amplitude modulation. Continuous phase modulation (CPM) is an attractive scheme for digital transmission because of its constant envelope which is needed for power efficient transmitters. Recent research has shown that space-time coded CPM can achieve transmit diversity to improve performance while maintaining the compact spectrum of CPM signals. However, these efforts mainly combine space- time coding (STC) with CPM to achieve spatial diversity at the cost of a high decoding complexity. In this paper, we design space-time block codes (STBC) for binary CPM with modulation index h = 1/2 and derive low-complexity receivers for these systems. The proposed scheme has a much lower decoding complexity than STC CPM with the Viterbi decoder and still achieves near-optimum error performances.

Cooperative Relaying with CPFSK and Distributed Space-Time Trellis Codes

Abstract: Cooperative relaying allows single antenna users to achieve diversity and coding gains by utilizing nearby users' transmitting capabilities. We consider a relay system employing constant envelope continuous phase frequency shift keying. Distributed space-time trellis codes are implemented with a novel multiple relay protocol.

Timing recovery based on the PAM representation of CPM

Abstract: A reduced-complexity decision-directed timing recovery method for continuous phase modulation (CPM) is presented. Using the well-known and popular pulse amplitude modulation (PAM) representation-or Laurent representation- of CPM, we develop two different formulations of a PAM-based timing error detector (TED). We consider the general M-ary multi-h CPM model in our development and use the family of aeronautical telemetry CPMs for our numerical examples. We show by analysis that the two TED formulations have identical ldquoS-curverdquo characteristics, and are free of false lock points, but have slightly different performance when applied to specific CPM examples, particularly in the multi-h case. There is no unanimous winner between the two formulations in all cases; however, for both formulations, we show the TEDs are able to perform close to the theoretical limit given by the modified Cramer-Rao bound. As such, the proposed TEDs provide an important synchronization component for reduced-complexity PAM-based CPM receivers that has heretofore been missing.

Coded Single-Sideband QPSK and Its Turbo Detection for Mobile Communication Systems

Abstract: This paper proposes a novel single-sideband quadrature phase shift keying (SSB QPSK) modulation scheme that utilizes a single-reference carrier frequency and transforms both baseband I and Q components into the same radio frequency band, whose width is exactly half that of QPSK. The modulation method is first derived and followed by the analysis of the matched filter demodulation. The analysis shows that there are performance degradations due to intersymbol interference (ISI) in the received signal and correlation in the received noise. To suppress the degradations, this paper employs a turbo equalizer for demodulation, in which the effects of ISI and noise correlation can be suppressed by a soft canceler and a noise whitening filter in the minimum mean square error (MMSE) linear equalizer, respectively. The computer simulations are then used to verify the proposed modulation scheme. At the transmitter, the root-raised cosine rolloff filter is employed for pulse shaping and Hilbert-transformed pulse generation. The truncation of the signal pulse is performed by the window function. The results show that the proposed modulation scheme outperforms 16-quadratic-amplitude modulation (16-QAM) with the turbo code in the Rayleigh-fading environment.

L2 orthogonal space time code for Continuous Phase Modulation

Abstract: To combine the high power efficiency of Continuous Phase Modulation (CPM) with either high spectral efficiency or enhanced performance in low signal to noise conditions, some authors have proposed to introduce CPM in a MIMO frame, by using Space Time Codes (STC). In this paper, we address the code design problem of Space Time Block Codes combined with CPM and introduce a new design criterion based on L2 orthogonality. This L2 orthogonality condition, with the help of simplifying assumption, leads, in the 2times2 case, to a new family of codes. These codes generalize the Wang and Xia code, which was based on pointwise orthogonality. Simulations indicate that the new codes achieve full diversity and a slightly better coding gain. Moreover, one of the codes can be interpreted as two antennas fed by two conventional CPMs using the same data but with different alphabet sets. Inspection of these alphabet sets lead also to a simple explanation of the (small) spectrum broadening of Space Time Coded CPM.

Communication Using Continuous-Phase Modulated Signals

Abstract: Embodiments of a circuit are described. In this circuit, a modulation circuit provides a first modulated electrical signal and a second modulated electrical signal, where a given modulated electrical signal, which can be either the first modulated electrical signal or the second modulated electrical signal, includes minimum-shift keying (MSK) modulated data. Moreover, a first phase-adjustment element, which is coupled to the modulation circuit, sets a relative phase between the first modulated electrical signal and the second modulated electrical signal based on a phase value of the first phase-adjustment element. Additionally, an output interface, which is coupled to the first phase-adjustment element, is coupled to one or more antenna elements which output signals. These signals include a quadrature phase-shift-keying (QPSK) signal corresponding to the first modulated electrical signal and the second modulated electrical signal.

Generic, reduced state, maximum likelihood decoder

Abstract: A decoder includes at least one programming input for a plurality of programmable reduced-state trellis parameters. A programmable device is connected to the at least one programming input and implements a reduced-state maximum likelihood decoder that is operable for processing a continuous phase modulated (CPM) signal and returning up to N bits that were transmitted based on a maximum likelihood and current winning super-state and corresponding survivor full-state. The programmable device calculates the path metrics for every super-state and determines a best path based on the reduced-state trellis parameters.

Joint Source and Channel Coding using Punctured Ring Convolutional Coded CPM

Abstract: In this paper, a novel trellis source encoding scheme based on punctured ring convolutional codes is presented. Joint source and channel coding (JSCC) using trellis coded continuous phase modulation (CPM) with punctured convolutional codes over rings is investigated. The channels considered are the additive white gaussian noise (AWGN) channel and the Rayleigh fading channel. Optimal soft decoding for the proposed JSCC scheme is studied. The soft decoder is based on the a posteriori probability (APP) algorithm for trellis coded CPM with punctured ring convolutional codes. It is shown that these systems with soft decoding outperform the same systems with hard decoding especially when the systems operate at low to medium signal-to-noise ratio (SNR). Furthermore, adaptive JSCC approaches based on the proposed source coding scheme are investigated. Compared with JSCC schemes with fixed source coding rates, the proposed adaptive approaches can achieve much better performance in the high SNR region. The novelties of this work are the development of a trellis source encoding method based on punctured ring convolutional codes, the use of a soft decoder, the APP algorithm for the combined systems and the adaptive approaches to the JSCC problem.

On Reduced-Complexity Soft-Output Detection of Continuous Phase Modulations

Abstract: We compare low-complexity schemes for soft-output detection of continuous phase modulations (CPMs). In particular, we address the problem of minimizing the complexity of the front end filters and that of the trellis exploited by the detection algorithm, with the aim of assuring a negligible performance degradation with respect to the optimal full-complexity receiver. We show that the approach providing the simplest front end is that based on the CPM decomposition proposed by Moqvist and Aulin. On the other hand, we prove that the most convenient solution in terms of trellis complexity is provided by the CPM decomposition proposed by Mengali and Morelli, possibly combined with suitable techniques for reduced trellis search.

Concatenated eIRA Codes for Tamed Frequency Modulation

Abstract: A new scheme of the extended irregular repeat- accumulate (eIRA) coded tamed frequency modulation (TFM) for deep space communications is introduced in this paper. It is mainly based on the optimal concatenation of the eIRA code and the continuous phase encoder (CPE) decomposed from TFM. In order to obtain good performance of the eIRA coded TFM, the main principle of our scheme is to jointly optimize the concatenation by eliminating the short loops in the Tanner graph of the eIRA code and the coding part of TFM and to jointly decode between them. Then our scheme without interleaving and the contrast scheme with interleaving are simulated in an additive white Gaussian noise (AWGN) channel which is typical in deep space communications. Simulation results have shown that our scheme can obtain lower complexity and less decoding delay (due to the reduction of interleaving) at the cost of just 0.1-0.15 dB performance loss when compared to the scheme with interleaving given bit-error-ratio (BER) of 10 5. Therefore, our scheme can be used to implement the coded TFM system for deep space communications with good performance and low complexity.

Retrieval of instantaneous frequency from digital holograms based on adaptive windows

Abstract: In recent years, time-frequency analysis methods have been significantly developed for the processing of fringe patterns. Among such methods, the short-time Fourier transform (STFT) has been proven a valid method to process noisy fringe patterns. In this paper, the complex phasor and the STFT are used to retrieve instantaneous frequency from a series of holograms based on adaptive windows. Continuous phase maps are calculated by integration of the extracted instantaneous frequency, and phase unwrapping is effectively avoided in both temporal and spatial domains. The validity of this method is verified by an experiment. In addition, a comparison between conventional temporal phase unwrapping and the STFT is presented.