Showing papers on "Continuous phase modulation published in 2009"
Patent•
09 Apr 2009
TL;DR: In this paper, a class of bandwidth reduction techniques are used to develop a broad class of modulation types collectively called SSB-FM, which can be used to construct communication systems that provide bandwidth-normalized performance gains of 10 dB or more when compared to popular prior art modulation methods.
Abstract: A class of bandwidth reduction techniques are used develop a broad class of modulation types collectively called SSB-FM. These signals can be used to construct communication systems that provide bandwidth-normalized performance gains of 10 dB or more when compared to popular prior art modulation methods. An aspect of the invention involves mapping trellis paths in a complex signal space onto corresponding real-valued trellis signals with desirable spectral properties. The invention can be used map continuous phase modulated (CPM) signals onto simpler amplitude-modulated trellis signals having double the channel capacity of prior art CPM signals. Multi-amplitude signaling and frequency division multiplexing may also be incorporated to further accommodate more information per symbol.
118 citations
TL;DR: In this paper, a phase shifter with a fractional bandwidth of 26% and an average insertion loss of 6 dB over all phase states is presented, and the measured return loss is greater than 12 dB.
Abstract: The design and measurement of a compact, wide-band reflective-type phase shifter in 90 nm CMOS technology in V-band frequency is presented. This phase shifter has a fractional bandwidth of 26% and an average insertion loss of 6 dB over all phase states. The chip area is only 0.08 mm 2. Measurement results show that the developed phase shifter provides 90° continuous phase shift over the frequency range of 50-65 GHz. The measured return loss is greater than 12 dB at 50 GHz. The output power is linear up to at least 4 dBm input power.
70 citations
TL;DR: The proposed concatenated structure offers very low error floors and good performance in the waterfall region for all considered spectral efficiencies, and a significant improvement with respect to previous concatenation CPM schemes is shown.
Abstract: In this paper, serially concatenated continuous phase modulation (SCCPM) is considered for the uplink of satellite communications. A three-step design procedure is proposed to optimize the association of the outer code and the CPM for a wide range of spectral efficiencies, ranging from 0.75 to 2.25 bit/s/Hz. Firstly, EXIT chart analysis is applied to derive general guidelines for choosing SCCPM parameters. A significant result is that a high-rate outer code is required to achieve good convergence threshold, given a spectral efficiency. At a second stage, union bounds to the error probability are considered to choose the outer code under the constraints arising from the EXIT charts analysis. From this analysis, extended BCH codes and extended Hamming codes are proposed as outer code for broadband and narrowband transmission, respectively. For the latter, double-binary convolutional codes and symbol interleaving is also proposed as a valid alternative. Finally, combining both EXIT charts and union bounds we optimize the association of code and CPM to achieve both low error rates and good convergence. The proposed concatenated structure offers very low error floors and good performance in the waterfall region for all considered spectral efficiencies. A significant improvement with respect to previous concatenated CPM schemes is shown.
66 citations
TL;DR: This paper devise theory to show that coherent modulation filtering imposes a new bandlimiting constraint on the product of the modulator and carrier as well as the ability to recover arbitrarily chosen envelopes and carriers from their modulation product, and formally show that a carrier estimate based on the time-varying spectral center-of-gravity satisfies the band Limiting condition.
Abstract: Modulation filtering is a class of techniques for filtering slowly-varying modulation envelopes of frequency subbands of a signal, ideally without affecting the subband signal's temporal fine-structure. Coherent modulation filtering is a potentially more effective type of such techniques where, via an explicit product model, subband envelopes are determined from demodulation of the subband signal with a coherently detected subband carrier. In this paper we propose a coherent modulation filtering technique based on detecting the instantaneous frequency of a subband from its time-frequency representation. We devise theory to show that coherent modulation filtering imposes a new bandlimiting constraint on the product of the modulator and carrier as well as the ability to recover arbitrarily chosen envelopes and carriers from their modulation product. We then formally show that a carrier estimate based on the time-varying spectral center-of-gravity satisfies the bandlimiting condition. This bandwidth constraint leads to effective and artifact-free modulation filters, offering new approaches for potential signal modification. However, the spectral center-of-gravity does not, in general, satisfy the condition of arbitrary carrier recovery. Finally, the results from modulation-filtering a speech signal are then used to validate the theory.
64 citations
TL;DR: The spectral efficiency of continuous phase modulations is investigated, and an effective bandwidth definition for a CPM signal, whose power spectral density has in principle an infinite support is adopted, based on the spacing between adjacent carriers in a frequency division multiplexed CPM system.
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, which 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 efficiencies reported in the literature and obtained by heuristic approaches can be achieved.
62 citations
Patent•
09 Jun 2009
TL;DR: In this paper, a method for modulating single carrier signals using constant envelope 2-CPM modulation and quasi-constant envelope filtered continuously rotated pseudo-PSK modulation in a wireless communication system is presented.
Abstract: Certain aspects of the present disclosure relate to a method for modulating single carrier signals using constant envelope 2-CPM modulation and quasi-constant envelope filtered continuously rotated pseudo-PSK modulation in a wireless communication system.
57 citations
04 May 2009
TL;DR: It is observed that for the CPM implementation the rise/fall-time becomes the limiting factor on spectral containment and a rather simple scheme based on Chireaux out-phasing is suggested as a means to “slow down” the pulse rise/ fall.
Abstract: In this paper we shall demonstrate how a polyphase-coded radar waveform can be implemented using a continuous phase modulation (CPM) framework so as to achieve spectral containment while maintaining a constant envelope to maximize energy-on-target. Current modulation techniques such as derivative phase shift keying (DPSK) and minimum shift keying (MSK), which are applicable to binary-coded waveforms, are well-known implementation schemes for spectral containment. The CPM implementation is applicable to polyphase codes and can also achieve better spectral containment, though a by-product is increased range sidelobes that result due to the deviation from the idealized code (implicitly defined for squared-shaped chips). To ameliorate the increased range sidelobes, a version of Least-Squares mismatched filtering is employed that accommodates the continuous nature of the CPM structure. Also, continuous rise/fall-time transitions of the pulse are addressed as part of the holistic implementation of the CPM-based waveform. It is observed that for the CPM implementation the rise/fall-time becomes the limiting factor on spectral containment and a rather simple scheme based on Chireaux out-phasing is suggested as a means to “slow down” the pulse rise/fall.
48 citations
TL;DR: Simulation results in a 60 GHz environment show that the reduced-complexity MMSE equalizer significantly outperforms the state of the art linear MMSE receiver for large modulation indices, while it performs only slightly worse for small ones.
Abstract: In this paper, we develop a new low-complexity linear frequency domain equalization (FDE) approach for continuous phase modulated (CPM) signals. As a CPM signal is highly correlated, calculating a linear minimum mean square error (MMSE) channel equalizer requires the inversion of a nondiagonal matrix, even in the frequency domain. In order to regain the FDE advantage of reduced computational complexity, we show that this matrix can be approximated by a block-diagonal matrix without performance loss. Moreover, our MMSE equalizer can be simplified to a low-complexity zero-forcing equalizer. The proposed techniques can be applied to any CPM scheme. To support this theory we present a new polyphase matrix model, valid for any block-based CPM system. Simulation results in a 60 GHz environment show that our reduced-complexity MMSE equalizer significantly outperforms the state of the art linear MMSE receiver for large modulation indices, while it performs only slightly worse for small ones.
42 citations
TL;DR: An algorithm for recognition of different types of continuous phase modulation signals that uses a combination of features extracted through cyclic spectral analysis and an ICA-SVM hybrid recognition system is presented.
Abstract: Automatic modulation recognition is a topic of interest in many fields including signal surveillance, multi-user detection and radio frequency spectrum monitoring. In this paper, we present an algorithm for recognition of different types of continuous phase modulation signals that uses a combination of features extracted through cyclic spectral analysis and an ICA-SVM hybrid recognition system. Simulation results demonstrate the ability of the algorithm to correctly identify modulation types over a wide range of SNR scenarios. The effects of pulse shaping and partial response waveforms are also investigated.
39 citations
Patent•
08 Jun 2009
TL;DR: In this article, a method for generating single carrier signals with spread-spectrum coded preambles using constant envelope 2-CPM modulation for transmission in a wireless communication system, and for efficient despreading method at a receiver.
Abstract: Certain aspects of the present disclosure relate to a method for generating single carrier signals with spread-spectrum coded preambles using constant envelope 2-CPM modulation for transmission in a wireless communication system, and for efficient despreading method at a receiver.
37 citations
TL;DR: In this article, a least squares integration of phase gradient method is used to remove 2 π ambiguities in the phase image and a continuous surface profile of the test object can be obtained.
Abstract: Quantitative phase imaging is a vital technique in many areas of science. Studying properties and characteristics of biological and other microscopic specimens has been facilitated with new quantitative phase imaging microscopy methods. In quantitative phase imaging, phase images are obtained by interfering two light beams – one reflected from, or traversed through, the specimen and the other reflected from a reference mirror. This can be achieved by two methods; holography or phase-shifting interferometry. In holography, one interferogram is used to produce the phase image, while phase-shifting interferometry uses three or more interferograms. Each fringe in an interferogram represents an area of data ranging from 0 to 2 π . Therefore, the final phase map obtained from a series of interferograms also contains 2 π ambiguities. Such phase maps are called ‘wrapped’ phase maps, and are needed to be ‘unwrapped’ by removing 2 π ambiguities. Once these 2 π ambiguities are removed, a continuous surface profile of the test object can be obtained. Such a surface profile provides height information of surface features. Generally, phase unwrapping is done by using numerical algorithms. Most of these numerical algorithms are computationally intensive and can fail when there are irregularities in the test object. In the basic phase unwrapping method, the phase image is divided to horizontal lines and these lines are unwrapped separately by scanning pixels and adding an offset to each pixel. At each discontinuity a 2 π offset is added or subtracted. After all horizontal lines are unwrapped, they are connected vertically and the unwrapping process is done along vertical lines. There are many phase unwrapping methods to remove 2 π ambiguities and most can be categorized into two types; path-dependent methods and path-independent methods. Path-dependent methods detect positions of edges and phase ambiguities in images and use this information to calculat e phase offset values. In path-independ ent methods, areas that can cause errors in unwrapping are identified and eliminated before the unwrapping process starts. In 1994 Ghiglia and Romero used a least squares integration method with phase unwrapping. In this method, which is known as least squares integration of phase gradient method, the phase gradient is obtained as wrapped phase differences along two perpendicular directions and the gradient field is least squares integrated to obtain continuous phase. However, this method is not effective for phase maps with high noise. P.
07 Jun 2009
TL;DR: In this article, a systematic analysis of different CMOS mm-wave phase shifter architectures for single chip portable radar is presented, where three different active and passive phase shifters are designed and fabricated in standard 1P7M 90nm CMOS process to operate in the frequency band of 50 GHz to 56 GHz.
Abstract: This paper demonstrates, for the first time, a systematic analysis of different CMOS mm-wave phase shifter architectures for single chip portable radar. Three different active and passive phase shifters are designed and fabricated in standard 1P7M 90nm CMOS process to operate in the frequency band of 50 GHz to 56 GHz. The fabricated passive phase shifter has a phase tuning range of 141° with an average RMS gain error of 1.93 dB. The innovative active quadrature-generator-based active phase shifter has an average RMS gain & phase error of 0.64 dB & 6.36° while the passive quadrature-generator-based active phase shifter has an average RMS gain and phase error of 1.36 dB & 15°. To the best of the authors' knowledge, the fabricated CMOS active phase shifters exhibit the best performances reported till date with a continuous phase tuning range of 360° at frequencies above 40GHz.
Proceedings Article•
30 Oct 2009
TL;DR: In this article, a broadside coupler was employed in the multi-layer metal structure in CMOS technology to attain 3dB coupling at coupled and through ports where the phase difference between these two ports is 90°.
Abstract: This paper presents a wideband reflective-type phase-shifter in 90nm CMOS technology. The proposed phase shifter, employs a broadside coupler in the multi-layer metal structure in CMOS technology to attain 3-dB coupling at coupled and through ports where the phase difference between these two ports is 90°. The reflective load contains a NMOS CMOS varactor with a tuning ratio of 3. Applying a 0–1 V DC tuning voltage, the overall phase shifter provides 0–87° continuous phase shift, where the insertion loss of the phase shifter alters between 4.5–8 dB at the frequency range of 50–65 GHz and occupies chip area of 0.3×0.25mm2. The overall phase shift achieved by this design can be extended to 180 and 360 degree.
TL;DR: A doubly-iterative linear receiver, equipped with a soft-information aided frequency domain minimum mean-squared error (MMSE) equalizer, is proposed for the combined equalization and decoding of coded continuous phase modulation signals over long multipath fading channels.
Abstract: In this paper, a doubly-iterative linear receiver, equipped with a soft-information aided frequency domain minimum mean-squared error (MMSE) equalizer, is proposed for the combined equalization and decoding of coded continuous phase modulation (CPM) signals over long multipath fading channels. In the proposed receiver architecture, the front-end frequency domain equalizer (FDE) is followed by the soft-input, soft-output (SISO) CPM demodulator and channel decoder modules. The receiver employs double turbo processing by performing back-end demodulation/decoding iterations per each equalization iteration to improve the a priori information for the front-end FDE. As presented by the computational complexity analysis and simulations, this process provides not only a significant reduction in the overall computational complexity, but also a performance improvement over the previously proposed iterative and noniterative MMSE receivers.
TL;DR: It is shown that a quantization scheme can be used to yield an extremely low-complexity version of the system with only negligible performance losses, and the S-curve of the proposed quantized TED is given, which rules out the existence of false lock points.
Abstract: We consider symbol timing recovery for continuous phase modulations (CPMs) with correlated data symbols. A popular example of such a scheme is shaped offset quadrature phase-shift keying (SOQPSK). We propose an extension to an existing non-data-aided (blind) timing error detector (TED) to make it compatible with such modulation schemes. The merits of the modified TED are demonstrated by comparing its performance with and without taking the data correlation into account. As a further modification, we show that a quantization scheme can be used to yield an extremely low-complexity version of the system with only negligible performance losses. The S-curve of the proposed quantized TED is given, which rules out the existence of false lock points. The proposed scheme shows great promise in a wide range of applications due to its low complexity, its lack of false lock points, and its blind nature; such applications include timing recovery for noncoherent detection schemes and false lock detectors.
TL;DR: This paper proposes a new frequency-domain channel-estimation and equalization method for continuous-phase modulation block transmissions with superimposed pilot signals that provides spectral and power-efficient broadband CPM wireless communications with less complexity than previous methods.
Abstract: This paper proposes a new frequency-domain channel-estimation and equalization method for continuous-phase modulation (CPM) block transmissions with superimposed pilot signals. Our method provides spectral and power-efficient broadband CPM wireless communications with less complexity than previous methods. The proposed frequency-domain channel estimation uses the superimposed pilot sequence as a reference signal to reduce the throughput loss caused by traditionally multiplexed pilots. The proposed CPM frequency-domain decision feedback equalizer (DFE) eliminates the complexity overhead of conventional decomposition-based CPM receivers.
30 Nov 2009
TL;DR: This paper addresses the joint path delay and time-varying complex gain estimation for continuous phase modulation (CPM) over a time-selective slowly varying flat Rayleigh fading channel with an expectation-maximization algorithm for path delay estimation in a Kalman smoother framework.
Abstract: This paper addresses the joint path delay and time-varying complex gain estimation for continuous phase modulation (CPM) over a time-selective slowly varying flat Rayleigh fading channel. We propose an expectation-maximization (EM) algorithm for path delay estimation in a Kalman smoother framework. The time-varying complex gain is modeled by a first order autoregressive (AR) process. Such a modeling yields to the representation of the problem by a dynamic bayesian system in a state-space form that allows the application of EM algorithm in the context of unobserved data for obtaining an estimate of the path delay. This is used with Kalman smoother for state estimation. We derive analytically a closed-form expression of the modified hybrid Cramer-Rao bound (MHCRB) for path delay and complex gain parameters. Finally, some numerical examples are presented to illustrate the performance of the proposed algorithm compared to the conventional generalized correlation method and to the MHCRB.
TL;DR: This work shows how an existing CPM-based timing error detector (TED) can be adapted to the unique characteristics of SOQPSK and shows that the proposed decision-directed TED (DD-TED) performs close to these bounds in computer simulations and is free of false-lock points.
Abstract: Shaped-offset quadrature phase shift keying (SOQPSK) is a highly bandwidth efficient modulation technique used widely in military and aeronautical telemetry standards. It can be classified as a form of continuous phase modulation (CPM), but its major distinction from other CPMs is that it has a constrained (correlated) ternary data alphabet. CPM-based detection models for SOQPSK have been developed only recently. While these detectors offer an appreciable performance gain over current detection schemes, one roadblock standing in the way of their being adopted is the lack of a CPM-based symbol timing recovery scheme that will work with SOQPSK. We show how an existing CPM-based timing error detector (TED) can be adapted to the unique characteristics of SOQPSK. The TED is formulated for a coherent detector but can be extended to the noncoherent case. We apply this timing recovery method to the versions of SOQPSK used in military (MIL-STD SOQPSK) and telemetry group (SOQPSK-TG) standards. We derive the theoretical performance limits on the accuracy of timing recovery for SOQPSK, as given by the modified Cramer-Rao bound (MCRB), and show that the proposed decision-directed TED (DD-TED) performs close to these bounds in computer simulations and is free of false-lock points. We also show that the proposed scheme outperforms a non-data-aided TED (NDA-TED) that was recently developed for SOQPSK. These results show that the proposed scheme has great promise in a wide range of applications due to its low complexity, strong performance, and lack of false-lock points.
TL;DR: Two-state decision feedback detectors for shaped-offset quadrature phase-shift keying (SOQPSK) show that the state complexity can be reduced to a minimal level - two states - with asymptotically optimum performance, as demonstrated by performance analysis and confirmed by computer simulations.
Abstract: We consider highly-simplified decision feedback detectors for shaped-offset quadrature phase-shift keying (SOQPSK), a highly bandwidth-efficient and popular constant-envelope modulation. In particular, we show that the state complexity can be reduced to a minimal level - two states - with asymptotically optimum performance, as demonstrated by performance analysis and confirmed by computer simulations. The complexity reduction is achieved by a novel manipulation of the differential encoder and the SOQPSK precoder, which are both part of the transmission model for SOQPSK. We give two possible architectures for achieving this complexity reduction: the pulse amplitude modulation (PAM) technique and the pulse truncation (PT) technique. We also formulate these detectors for coherent and noncoherent detection. The resulting family of detectors makes use of recent advances in SOQPSK technology based on a continuous phase modulation (CPM) interpretation of SOQPSK. The proposed simplifications are significant because they minimize the complexity of trellis-based SOQPSK detectors, which have become available only in recent years. Because trellis-based SOQPSK detectors are 1-2 dB superior to the widely-deployed family of symbol-by-symbol SOQPSK detectors, the proposed two-state detectors offer the simplest means of achieving these performance gains. Thus, these simple detection schemes are applicable in settings where high performance and low complexity are needed to meet restrictions on power consumption and cost.
05 May 2009
TL;DR: The complete model of Quadrature Phase Shift Keying (QPSK) modulator and demodulator has been developed and final hardware design and implementation of QPSK for Wireless Modem has been proposed.
Abstract: Digital modulation is a process that impresses a digital symbol on to a signal suitable for transmission on a wired or wireless medium in order to receive that signal at receiving end correctly with out any loss of information. Quadratic phase shift keying (QPSK) modulation technique is the most widely used modulation scheme in modern digital communication system; it provides high performance on bandwidth efficiency and bit error rate. In this paper the complete model of Quadrature Phase Shift Keying (QPSK) modulator and demodulator has been developed. The model has been simulated in Matlab using Simulink. Complete results are tested and verified. In final hardware design and implementation of QPSK for Wireless Modem has been proposed. QPSK modulation has various applications particularly in the design of wireless modem, cellular CDMA communication.
TL;DR: A generalization of periodic clustered-dot halftones is proposed, wherein the phase of the halftone spots is modulated using a secondary signal to improve spatial and tonal rendering and modulating the screen frequency according to the frequency content of the continuous tone image.
Abstract: A generalization of periodic clustered-dot halftones is proposed, wherein the phase of the halftone spots is modulated using a secondary signal. The process is accomplished by using an analytic halftone threshold function that allows halftones to be generated with controlled phase variation in different regions of the printed page. The method can also be used to modulate the screen frequency, albeit with additional constraints. Visible artifacts are minimized/eliminated by ensuring the continuity of the modulation in phase. Limitations and capabilities of the method are analyzed through a quantitative model. The technique can be exploited for two applications that are presented in this paper: (a) embedding watermarks in the halftone image by encoding information in phase or in frequency and (b) modulating the screen frequency according to the frequency content of the continuous tone image in order to improve spatial and tonal rendering. Experimental performance is demonstrated for both applications.
30 Nov 2009
TL;DR: A technique for constructing a training sequence of known symbols instead of a CP for CPMFDE and results in a 60 GHz environment show that the proposed technique satisfies all requirements.
Abstract: Frequency domain equalization (FDE) of continuous phase modulations (CPM) has been thoroughly investigated lately. To enable this low-complexity FDE, all known techniques use a cyclic prefix (CP). However, using a training sequence (TS) of known symbols instead of a CP offers some advantages: the additional known symbols can be used to improve synchronization and channel estimation, with the same performance of a CP. Nevertheless, using a TS for CPM-FDE is not trivial because the memory in a CPM waveform has to be taken into account to guarantee cyclicity and phase continuity after insertion of the TS into a block of input symbols. In this paper, we therefore propose a technique for constructing a TS for CPMFDE. Simulation results in a 60 GHz environment show that the proposed technique satisfies all requirements. The 60 GHz case is chosen because CPM with FDE has recently been proposed for communications at 60 GHz and the latest IEEE and ECMA standards for these frequencies mandate the use of a TS rather than a CP.
TL;DR: The work here renders it adaptive by developing a recursive metric that is adapted on-line based on the received signals, without prior knowledge of the carrier phase characteristics.
TL;DR: A new method of demodulating link-16 message demodulation is presented by digitizing the incoming signal in a superconducting delta-sigma modulator driving a 1 to 64 deserializer, then digitally filtering with a polyphase implementation of a sliding Goertzel filter.
Abstract: We describe the design of a new demodulator for continuous phase frequency modulated signals such as link-16 messages. A link-16 message consists of short RF pulses containing 32 ldquochipsrdquo each one having duration of 200 ns. One of the main difficulties in demodulation of such signals is the very short ldquochiprdquo period as compared to the frequency difference between the carrier and its' modulation. For example in link-16, the difference in frequency between the carrier and its' modulated signal is only 1.25 MHz. This makes traditional demodulation approaches, i.e., mixing the incoming signal with the carrier frequency and then low-pass filtering ineffective. We present a new method of demodulating such signals by digitizing the incoming signal in a superconducting delta-sigma modulator driving a 1 to 64 deserializer, then digitally filtering with a polyphase implementation of a sliding Goertzel filter. We have designed and fabricated a bandpass analog-to-digital converter (ADC) chip with an on chip deserializer, an additional room-temperature deserializer, and an FPGA polyphase implementation of sliding Goertzel filter. The results are presented for our experimental evaluation of link-16 message demodulation.
TL;DR: An orthogonal space-time (ST) block coding (STBC) technique for continuous phase modulation (CPM) is proposed and combined with a frequency domain equalizer (FDE) to obtain high performance gains over frequency-selective channels.
Abstract: In this letter, an orthogonal space-time (ST) block coding (STBC) technique for continuous phase modulation (CPM) is proposed and combined with a frequency domain equalizer (FDE) to obtain high performance gains over frequency-selective channels. The new method maintains the constant envelope and phase continuity of the CPM waveforms perfectly by using appropriate tail symbols during the addition of cyclic prefix and interblock transitions and, therefore, has no negative impact on the spectral efficiency. Because the STcoded CPM blocks remain orthogonal, FDE is applied as in the case of single antenna transmissions without any increase in the computational load. Simulations corroborate the performance improvement offered by STBC while also preserving the desired bandwidth efficiency of CPM.
TL;DR: A new approach for the demodulation of fringe patterns recorded in holographic interferometry using high-order ambiguity function (HAF) that directly provides an estimation of the continuous phase distribution and thereby avoids the necessity of using a cumbersome 2D phase unwrapping procedure.
Abstract: This letter introduces a new approach for the demodulation of fringe patterns recorded in holographic interferometry using high-order ambiguity function (HAF). The proposed approach is capable of retrieving the phase from a single fringe pattern. The main advantage of this approach is that it directly provides an estimation of the continuous phase distribution and thereby avoids the necessity of using a cumbersome 2D phase unwrapping procedure. This method first computes the discrete-time analytic signal of the recorded fringe pattern. Then, by modelling this analytic signal as a polynomial phase signal embedded in additive complex white Gaussian noise, a parametric estimation procedure based on HAF is employed to directly estimate the unwrapped phase distribution. Numerical simulations and experimental results demonstrate the potential of the proposed approach.
04 Dec 2009
TL;DR: Simulation results illustrate the validity of theoretical spectrum analysis, which prove that this CP-EBPSK system has high spectral efficiency, and belongs to the category of the UNB throughput-efficient communications.
Abstract: In this paper a throughput efficient modulation method based on the idea of continuous phase is devised, namely the continuous phase extended binary phase shift keying (CPEBPSK), which satisfies increasingly greater demand for the performance of communication systems. The detailed analysis of the corresponding power spectrum is derived by a universal way that is suitable for the binary modulation of ultra narrow band (UNB) communications. Simulation results illustrate the validity of theoretical spectrum analysis, which prove that this UNB system having high spectral efficiency. On this basis, the bandwidth is studied that indicates the CP-EBPSK technology belongs to the category of the UNB throughput-efficient communications.
TL;DR: Using a linear decomposition of CPM signals with tilted phase, a rank criterion is identified for M-ary partial- and full-response CPM that specifies the set of allowable modulation indices and a coding gain design criterion is proposed.
Abstract: Sufficient conditions are derived under which M-ary partial- and full-response continuous phase modulation (CPM) space-time (ST) codes will attain both full spatial diversity and optimal coding gain. General code construction rules are desirable due to the nonlinearity and inherent memory of the CPM signals which makes manual design or computer search difficult. Using a linear decomposition of CPM signals with tilted phase, we identify a rank criterion for M-ary partial- and full-response CPM that specifies the set of allowable modulation indices. We also propose a coding gain design criterion. Optimization of the coding gain for CPM ST codes is shown to depend on the CPM frequency/phase shaping pulse, modulation index, and codewords. The modulation indices and phase shaping functions that improve the coding gain are specified. Finally, optimization of coding gain for ST-CPM and orthogonal ST-CPM codewords is discussed.
28 Apr 2009
TL;DR: This new system gets the advantages of power efficiency of CE-OFDM and the performance improvement of the chaotic interleaving and comprises frequency domain equalization (FDE) to obtain high diversity gains over frequency selective multipath fading channels.
Abstract: Continuous phase modulation (CPM) is an attractive scheme for wireless communications because of its constant envelope (CE) and its ability to improve the diversity of the multipath channel. In this paper we propose a new interleaving scheme for the CPM based orthogonal frequency-division multiplexing (CE-OFDM) system, namely chaotic interleaving. The proposed system combines the key characteristics of CE-OFDM and the chaotic maps. Thus, this new system gets the advantages of power efficiency of CE-OFDM and the performance improvement of the chaotic interleaving. The proposed system comprises frequency domain equalization (FDE) to obtain high diversity gains over frequency selective multipath fading channels. The bit error rate (BER) performance of the CE-OFDM system with and without chaotic interleaving is evaluated by computer simulations. The simulation results show that, the CE-OFDM system based on the new interleaving scheme provides a better performance of about 2.3 dB improvements in SNR than the conventional CE-OFDM system.
18 Oct 2009
TL;DR: Results show that a signal space receiver based on B-splines approximates a wide variety of CPM signal sets with only a small number of basis functions and is particularly useful for spectrally efficient CPM waveforms.
Abstract: A basis function expansion to reduce the demodulation complexity of continuous phase modulation (CPM) signals applicable for either coherent or non-coherent reception in tactical networks is presented. Results show that a signal space receiver based on B-splines approximates a wide variety of CPM signal sets with only a small number of basis functions and is particularly useful for spectrally efficient CPM waveforms.