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Showing papers on "Continuous phase modulation published in 1993"


Patent
03 May 1993
TL;DR: In this paper, the authors proposed a coupled-tracking navigation receiver that periodically measures carrier phase, carrier frequency, modulation phase, and carrier amplitude for all of the signals arriving at the receiving ports of the receiver and periodically estimates the present values of carrier phase and frequency, and modulation phase for all received signals, the estimating process utilizing for each parameter estimate the parameter measurements for a plurality of the received signals properly combined in a statistically appropriate manner.
Abstract: The navigation receiver with coupled-tracking channels is intended for use in radio navigation systems based on trilateration wherein the times of arrival of radio signals transmitted by a plurality of ground- or space-based terminals are measured by a user terminal and utilized by the user terminal in calculating its position and orientation. The coupled-tracking navigation receiver periodically measures carrier phase, carrier frequency, modulation phase, and carrier amplitude for all of the signals arriving at the receiving ports of the receiver and periodically estimates the present values of carrier phase, carrier frequency, and modulation phase for all of the received signals, the estimating process utilizing for each parameter estimate the parameter measurements for a plurality of the received signals properly combined in a statistically appropriate manner by taking into account the relative geometry of the line-of-sight paths, receiver clock time dynamics, and dynamics and motion constraints of the receiver platform, thereby obtaining better performance under poor signal reception conditions and more accurate estimates of carrier phase, carrier frequency, and modulation phase for each of the received signals than independent measurements alone could provide. It follows that these more accurate estimates of the basic signal parameters lead to more accurate estimates of platform position and attitude and the rates of change of these quantities.

194 citations


Journal ArticleDOI
TL;DR: The authors examine maximum-likelihood block detection of uncoded full response continuous phase modulation over an additive white Gaussian noise (AWGN) channel and finds many new receiver structures that can be compared to the traditional ones that have been used in the past.
Abstract: The authors examine maximum-likelihood block detection of uncoded full response continuous phase modulation (CPM) over an additive white Gaussian noise (AWGN) channel. Both the maximum-likelihood metrics and the bit error probability performances of the associated detection algorithms are considered. The special and popular case of minimum-shift-keying (MSK) corresponding to h=0.5 and constant amplitude frequency pulse is treated separately. The many new receiver structures that result from this investigation can be compared to the traditional ones that have been used in the past both from the standpoint of simplicity of implementation and optimality of performance. >

92 citations


Patent
28 May 1993
TL;DR: In this article, a self-adjusting quadrature modulator and modulation method are used to improve the accuracy with which digital data is impressed on an RF carrier, which is particularly useful for systems having Viterbi, echo-integrating demodulators and for systems using subtractive CDMA techniques.
Abstract: A self-adjusting quadrature modulator and modulation method improve the accuracy with which digital data is impressed on an RF carrier, which is particularly useful for systems having Viterbi, echo-integrating demodulators and for systems using subtractive CDMA techniques. The method and apparatus involve receiving one's own transmission with a suitable modulation assessment receiver and determining the modulation error relative to the theoretically perfect transmission expected by the receiver. The measured error is used to adjust the modulation to minimize the error. The modulation assessment receiver may use log-polar signal processing to measure phase and (log)amplitude instead of cartesian I and Q components, and then convert to cartesian form. In addition, correction factors determined by the modulation assessment receiver can be directly identified with certain transform components produced by the Fast Walsh Transform.

91 citations


Patent
01 Nov 1993
TL;DR: In this article, a frequency diversity communication system is provided whereby the number of hopping channels is reduced and more continuous communication achieved as a mobile station travels from cell to cell by the combination of chips of symbols from the mobile sources.
Abstract: A frequency diversity communication system is provided whereby the number of hopping channels is reduced and a more continuous communication achieved as a mobile station travels from cell to cell by the combination of chips of symbols from the mobile sources. The transmitter divides each symbol of an input symbol sequence into a number K of chips, which are modulated with mutually different carrier frequencies. The receiver demodulates the signal sent by the transmitter by local frequencies corresponding respectively to the K different carrier frequencies. According to this invention, the carrier phase is coherent for each frequency of the received wave. Moreover, because the carrier phase is coherent, the outputs for each frequency of the received wave can be combined with the use of a training signal. The receiver also performs an estimation of the maximum likelihood of the transmitted symbol to eliminate the need for decoding. It is also provided that the order of the chips of the symbols is rearranged within a burst.

75 citations


Journal ArticleDOI
TL;DR: In this article, the phase is determined continuously as the phase locked loop scans the two-dimensional interferogram, and the phase can be implemented using a special purpose video processor for phase determination at video rates.
Abstract: A new technique for continuous phase determination of an interferogram based on a digital phase locked loop is presented. The main advantage of this method, with respect to well established techniques such as Fourier or phase stepping demodulation, is that the traditional approach to phase unwrapping processes by removal of discontinuities is not required. The phase is determined continuously as the phase locked loop scans the two-dimensional interferogram. Because of the sequential nature of the algorithm proposed, this can be implemented using a special purpose video processor for phase determination at video rates. The above mentioned properties makes the presented technique a fast algorithm for phase determination of carrier frequency interferograms modulated by a two-dimensional smooth phase function.

72 citations


Proceedings ArticleDOI
TL;DR: In this paper, a DPP design for inertial-confinement-fusion (ICF) laser systems, used to irradiate fuel capsules, is presented, which exhibits near-unity energy efficiency, envelope and power spectrum flexibility, and reduced near field intensity modulation.
Abstract: Efficient phase conversion of laser light can be achieved using continuous distributed phase plates (DPPs) for applications in laser-beam shaping and laser-beam smoothing. These DPPs are deep, surface-relief, continuous phase plates that exhibit near-unity energy efficiency, envelope and power spectrum flexibility, and reduced near-field intensity modulation as compared to stepped diffractive optics. Specific DPP designs for inertial-confinement-fusion laser systems, used to irradiate fuel capsules, is presented.

64 citations


Patent
Ian Hardcastle1
08 Sep 1993
TL;DR: In this article, an optical transmission system with a continuous phase frequency shift keyed modulation of a laser and a coherent heterodyne receiver is presented, including at the transmitter means for imposing a low frequency modulation on the transmitter optical power and frequency deviation and at the receiver means for extracting (28) from the receiver AGC control signal a replica of the low-frequency modulation, means for demodulating (32) the modulated frequency deviation of the received optical signal synchronously with respect to the extracted low frequency signal.
Abstract: An optical transmission system utilising at a transmitter (100) continuous phase frequency shift keyed modulation of a laser (14) and a coherent heterodyne receiver (200) therefor, the system including at the transmitter means for imposing (18, 12) a low frequency modulation on the transmitter optical power and frequency deviation and at the receiver means for extracting (28) from the receiver AGC control signal a replica of the low frequency modulation, means for demodulating (32) the modulated frequency deviation of the received optical signal synchronously with respect to the extracted low frequency signal, means for deriving (34) from the demodulated signal an error signal and a control system responsive to the error signal to control the receiver local oscillator (22) frequency.

57 citations


Proceedings ArticleDOI
23 May 1993
TL;DR: The authors analyze a full-digital receiver for band-limited spread-spectrum signals in a radio communication network employing asynchronous code-division multiplexing and constant-envelope continuous-phase modulation (CPM), and present a detailed analysis of the code synchronization strategy, both in the acquisition and in the tracking mode.
Abstract: The authors analyze a full-digital receiver for band-limited spread-spectrum signals in a radio communication network employing asynchronous code-division multiplexing and constant-envelope continuous-phase modulation (CPM). They present a detailed analysis of the code synchronization strategy, both in the acquisition and in the tracking mode. They also consider the issue of chip timing recovery, discussing first the impact of chip timing errors on code acquisition, and then evaluating the performance of three different code tracking loops. In particular, the acquisition performance is assessed in terms of false alarm and miss probabilities as well as average lock-in time, while in the analysis of the tracking behavior the root mean square chip timing jitter is assumed as the quality factor. A special subset of CPM, known as generalized minimum shift keying (GenMSK), encompassing Gaussian-filtered MSK modulation as well as traditional MSK, has been emphasized. >

36 citations


Patent
Hiroshi Saka1, Kazunao Urata1
02 Nov 1993
TL;DR: In this article, the frequency of the digitally modulated IF signal can be controlled in accordance with the frequency shift information related to an IF signal having a continuous phase and a digital modulation signal having discontinuous phase.
Abstract: A channel selecting apparatus simultaneously selects both the modulation signals, which are simultaneously received at different channels where modulation signals having a continuous phase and digital modulation signals having a discontinuous phase are located. As both the modulation signals are propagated on the same transmission path or approximately the same inclination of transmission path, modulation signals existing on different channel frequencies suffer approximately similar frequency shift from the transmission path before being inputted to the channel selecting apparatus. Therefore, the frequency of the digitally modulated IF signal can be controlled in accordance with the frequency shift information related to an IF signal having a continuous phase and the frequency of the digitally modulated IF signal may be focused into the comparatively narrow frequency range around the synchronous pull-in frequency of the digital demodulating circuit and the modulation signal having a continuous phase may be focused into the comparatively narrow frequency range around the optimum input frequency of the demodulation circuit.

29 citations


Proceedings ArticleDOI
07 Jun 1993
TL;DR: The PPT appears to be a practical approach to parametric modeling of a class of nonstationary signals and its application to estimating the parameters of complex signals with continuous phase and slowly varying amplitudes is discussed.
Abstract: Presents a tutorial discussion of the polynomial phase transform (PPT) and its application to estimating the parameters of complex signals with continuous phase and slowly varying amplitudes. The PPT-based algorithm provides suboptimal but computationally efficient estimates of the signal parameters. The performance of the algorithm on single-component signals is discussed in some detail. Preliminary results on estimating multicomponent signals are presently briefly. The PPT appears to be a practical approach to parametric modeling of a class of nonstationary signals. >

28 citations


Journal ArticleDOI
TL;DR: In this article, a real-time displacement measurement system using a sinusoidal phase modulating interferometer is proposed and demonstrated, which utilizes the frequency components of the interference signal to detect the desired phase or the displacement in real time.
Abstract: A real-time displacement measurement system using a sinusoidal phase modulating interferometer is proposed and demonstrated. The system utilizes the frequency components of the interference signal to detect the desired phase or the displacement in real time. The real-time phase detector is constructed with simple electronic circuits. The system also has a feedback loop to eliminate external disturbance. It is easy to measure the relatively large displacement that exceeds a half wavelength of the light because the compensation circuit is incorporated into the system to obtain continuous phase outside the region from 0 to 2π.

Journal ArticleDOI
TL;DR: A sequence estimation algorithm for the differential detection of the continuous phase modulation (CPM) signals, yielding significant gains in BER performance and with considerable resistivity to fading, is introduced and makes the proposed receiver useful for land mobile radio and mobile-satellite communications.
Abstract: A sequence estimation algorithm for the differential detection of the continuous phase modulation (CPM) signals, yielding significant gains in BER performance and with considerable resistivity to fading, is introduced. These advantages, along with the reduced hardware complexity, low cost, and fast synchronization which characterize the differential detector, make the proposed receiver useful for land mobile radio and mobile-satellite communications. The new receiver is based on multiple differential detection. The multiple differential detection strategy provides the decoder with more information regarding the transmitted data and applies a noise decorrelation process on the received signal, useful to the sequence estimation. The algorithm is derived in a general form, and can be applied on any CPM scheme, with any degree of complexity. The authors have evaluated the receiver for two of the most popular CPM schemes, the tamed frequency modulation (TFM) and Gaussian minimum-shift keying (GMSK) (with B/sub 1/T=0.25), in the presence of additive white Gaussian noise (AWGN) and Rician fading. The BER performance evaluation results indicated significant gains and considerable reduction of error floors. In AWGN improvements close to 9 dB have been verified. >

Journal ArticleDOI
TL;DR: An approach to reduced-complexity detection of partial response continuous phase modulation (CPM) on a linear multipath channel is presented and it is shown that for channels with a long memory, a significant complexity reduction can be achieved at the cost of a moderate degradation in performance.
Abstract: An approach to reduced-complexity detection of partial response continuous phase modulation (CPM) on a linear multipath channel is presented. The method, referred to as decision feedback sequence estimation (DFSE), is based on a conventional Viterbi algorithm (VA) using a reduced-state trellis combined with decision feedback (DF). By varying the number of states in the VA, the receiver structure can be changed gradually from a DF receiver to the optimal maximum-likelihood sequence estimator (MLSE). In this way different tradeoffs between performance and complexity can be obtained. Results on the receiver performance, based on minimum distance calculations and bit error rate simulations, are given for Gaussian minimum-shift keying modulation on typical mobile radio channels. It is shown that for channels with a long memory, a significant complexity reduction can be achieved at the cost of a moderate degradation in performance. >

Journal ArticleDOI
TL;DR: A phase representation of minimum shift keying (MSK) is used to show that MSK can be viewed as a coded-modulation scheme with an expanded signal set using Ungerboeck's set partitioning concept.
Abstract: A phase representation of minimum shift keying (MSK), which is a general framework suitable for use with other continuous phase modulation (CPM) schemes, is discussed. The representation is used to show that MSK can be viewed as a coded-modulation scheme with an expanded signal set using Ungerboeck's set partitioning concept (see IEEE Trans. Inf. Theory, vol.IT-28, no.1, p.55-67, 1982). The properties which follow from this view of MSK are explored. The uniqueness of the representation of MSK as a coded-modulation scheme and the structural relationships between different versions of MSK are described. >

Proceedings ArticleDOI
27 Apr 1993
TL;DR: It is concluded that, under significant noise degradation, only the scheme based on the fourth-order cumulant sequence can be used to estimate consistently the modulation index h in the range 0(h(1.0) - 1.1) .
Abstract: Three simple methods are proposed for the estimation of the modulation index of continuous phase modulated signals in noise. These methods employ the estimated autocorrelation and fourth-order cumulant sequences of the received signal after sampling at the symbol rate. Analytic expressions are derived for the asymptotic mean and variance of the estimated parameters which are corroborated by means of Monte Carlo simulations. The performance of the methods is illustrated graphically and numerically. It is concluded that, under significant noise degradation, only the scheme based on the fourth-order cumulant sequence can be used to estimate consistently the modulation index h in the range 0(h(1. >

Journal ArticleDOI
TL;DR: The performance of a hybrid modulation technique derived from binary frequency shift keying is presented, and the performance of complete and expurgated phase codes is examined for the Gaussian and Rayleigh fading channels.
Abstract: The performance of a hybrid modulation technique derived from binary frequency shift keying is presented. In the hybrid scheme, each frequency is allowed to be phase modulated with any of p discrete, equally spaced phase shifts. The spectral separation between frequencies is chosen to make the carriers orthogonal, thus generating a multidimensional modulation scheme. The performance of complete and expurgated phase codes is examined for the Gaussian and Rayleigh fading channels, and their spectral characteristics are determined. >

Proceedings ArticleDOI
23 May 1993
TL;DR: A systematic procedure for obtaining the optimal SSP subject to the new criterion is presented, based on two parameters: C, which determines the computational effort, and a distance parameter d'/sub min/, which characterizes the error event probability.
Abstract: The joint optimization of decoder complexity and error performance is considered for partial-response continuous phase modulation (CPM). The operation of the decoder is defined by a state-space partition (SSP), by which the states are divided into C classes. Proceeding breadth-first in the trellis, the decoder selects the single best path for each state-class. A novel decoder design criterion is formulated, based on two parameters: C, which determines the computational effort, and a distance parameter d'/sub min/, which characterizes the error event probability. A systematic procedure for obtaining the optimal SSP subject to the new criterion is presented. >

Journal ArticleDOI
TL;DR: In this paper, an analytical approach is presented to achieve error probability analysis of limiterdiscriminatorintegrator (LDI) detection of binary continuous-phase modulation in a land mobile radio channel characterized by Rayleigh fading and Doppler effects.
Abstract: A completely analytical approach is presented to achieve error probability analysis of limiter-discriminator-integrator (LDI) detection of binary continuous-phase modulation in a land mobile radio channel characterized by Rayleigh fading and Doppler effects. Optimum choice of the postdetection integration time is carried out when varying both system parameters and propagation characteristics, namely the Doppler shift. The improvements obtainable by means of decision feedback equalization (DFE) are also considered, in the presence of error propagation. The algorithm allows a very general analysis, which can be applied both to a partial and a full response modulation pulse, with narrowband IF filter and multipath propagation. This leads to the optimization of various system parameters, such as filter bandwidth, the modulation index, and the postdetection integration time, whatever the choice of the modulation pulse. >

Journal ArticleDOI
TL;DR: It turns out that, in the presence of phase jitter, multiple phase tracking provides better performance than single phase tracking, with a limited increase in the overall processing load of the decoder.

Proceedings ArticleDOI
11 Oct 1993
TL;DR: In this article, the authors considered the problem of estimating the modulation index of continuous phase modulated (CPM) signals in noise and derived analytical expressions for the cyclic autocorrelation and fourth-order cumulant sequences that permit the formulation of a maximum likelihood estimator.
Abstract: The authors address the problem of the estimation of the modulation index of continuous phase modulated (CPM) signals in noise. In a previous work (1993) they considered the same problem when the CPM signal was sampled at the symbol rate and thus constituted a stationary sequence. In this case, sampling is performed at a higher rate, and thus the discrete sequence becomes cyclostationary. Analytical expressions are derived for the cyclic autocorrelation and fourth-order cumulant sequences that permit the formulation of a maximum likelihood estimator. Simulation examples illustrate the performance of both methods. >

Proceedings ArticleDOI
18 May 1993
TL;DR: The modulation scheme in a mobile radio communication system must primarily satisfy the objective of achieving high spectral efficiency and narrow power spectrum and the effect of coding on transmission rate and improvement of SNR requirement is considered.
Abstract: The modulation scheme in a mobile radio communication system must primarily satisfy the objective of achieving high spectral efficiency and narrow power spectrum. The emerging modulation technologies in the family of linear modulation and constant envelope techniques are described. Multilevel modulation, spectral efficiency, power spectrum and intersymbol interference are discussed. The effect of coding on transmission rate and improvement of SNR requirement is considered.

Journal ArticleDOI
TL;DR: The approach of Morales-Moreno and Pasupathy (1988) is extended for the design of trellis codes for 4-ary continuous phase frequency shift keying (CPFSK) with modulation index h=1/2 and these codes improve the free Euclidean distance by up to 1.25 dB over previously published results.
Abstract: The approach of Morales-Moreno and Pasupathy (1988) is extended for the design of trellis codes for 4-ary continuous phase frequency shift keying (CPFSK) with modulation index h=1/2. The criterion for comparison of codes is the maximum free Euclidean distance for a given rate and the number of states of the signal space code. For the same number of states of the signal space code, these codes improve the free Euclidean distance by up to 1.25 dB over previously published results. Finally, the implementation of the combined coding and modulation system is discussed. >

Patent
01 Oct 1993
TL;DR: In this paper, a modulator is adapted for use in a transmitter of an information transmission signal in which the information is in the form of a frequency shift keyed code, and the signal is centered on a fictional carrier frequency fc, on either side of which are emitted two actual frequencies separated from the frequency by Δf, according to whether the binary information has a high value (+1) or a low value (-1).
Abstract: A modulator is adapted for use in a transmitter of an information transmission signal in which the information is in the form of a frequency shift keyed code. The signal is centered on a fictional carrier frequency fc, on either side of which are emitted two actual frequencies separated from the frequency fc by Δf, according to whether the binary information has a high value (+1) or a low value (-1). A first generator (1) creates carrier signals in the form of sin(2πf c t) and cos(2πf c t). A second generator (6) creates, as a function of the information, modulation signals of the form sin(2πΔft) and cos(2πΔft) which are mixed with the carrier signals. At each transition of the information, first phase shifting means (8,14) modify by kπ the phase of one of the modulation signals. Second phase shifting means (8,9,10,12), simultaneously with the action of the first phase shifting means and at each transition of the information, change the sign of the argument of the modulation signals. The carrier signal is thus devoid of phase jumps.

Journal ArticleDOI
Torgny Palenius1, Arne Svensson1
TL;DR: This paper proposes correlation detectors that calculate its metrics in a subspace of the signal space that corresponds to at least a five-fold reduction in number of filters and with the reduced complexity search algorithms for making symbol decisions this leads to a dramatic reduction in overall complexity.
Abstract: Optimum detectors for CPM use in general a large number of filters in order to calculate the optimum metrics. In this paper, we propose correlation detectors that calculate its metrics in a subspace of the signal space. The subspace is selected such that the asymptotic error performance is optimized for the given dimensionality. We focus on noncoherent detectors but show also some results for coherent detectors. The subspace metric calculation is combined with previously published reduced complexity decoding algorithms such as the SAN(B) and RSSD algorithms. Optimum subspace correlation detectors with different number of filters are found for both binary and quaternary CPM schemes. Their error performance on an AWGN channel is derived analytically through the use of a minimum Euclidean distance approach and is also simulated through the symbol error probability. Comparison is done with the optimum detectors. A close agreement between minimum distance and simulated symbol error probability is found for all considered detectors. We find that in most cases only 4 to 6 matched filters are needed in order to obtain a performance that is close to optimum. This corresponds to at least a five-fold reduction in number of filters and with the reduced complexity search algorithms for making symbol decisions this leads to a dramatic reduction in overall complexity.

Proceedings ArticleDOI
23 May 1993
TL;DR: New 2/3-rate convolutional codes for 8-ary continuous-phase frequency shift keying (CPFSK) with modulation indices h = 1/8, 1/4, 3/8 nd 1/2 are presented.
Abstract: New 2/3-rate convolutional codes for 8-ary continuous-phase frequency shift keying (CPFSK) with modulation indices h = 1/8, 1/4, 3/8 nd 1/2 are presented. The design of these coded CPFSK schemes is based on the continuous-phase modulation (CPM) decomposition technique. It is shown that some of the presented codes achieve 2 to 3 dB of gain in minimum Euclidean distance over the best codes found by the conventional optimization technique. >

Proceedings ArticleDOI
11 Oct 1993
TL;DR: Two examples of Direct-Sequence Code Division Multiple Access (DS/CDMA) communication systems with offset quadrature signals and smoother chip pulses than the rectangular pulse of the conventional Offset Quadrature Phase Shift Keying (OQPSK) modulation are presented.
Abstract: Two examples of Direct-Sequence Code Division Multiple Access (DS/CDMA) communication systems with offset quadrature signals and smoother chip pulses than the rectangular pulse of the conventional Offset Quadrature Phase Shift Keying (OQPSK) modulation are presented. The two systems use Minimum Shift Keying (MSK) and Sinusoidal Frequency Shift Keying (SFSK), which are continuous-phase modulation formats. It is shown that these two systems outperform OQPSK with regard to both bandwidth consumption and bit error probability. >

Patent
Ii-Hyun Nam1, Kwan-Seong Kim1
06 Oct 1993
TL;DR: In this paper, a differentially encoded quadrature modulation method comprises the steps of setting an index corresponding to a phase variation value constituted of input data, forming a phase value to obtain a phase-modulated output phase value from a given table and forming a channel signal to obtain in-phase (I) and Quadrature (Q) channel signals using the phase value.
Abstract: A differentially encoded quadrature modulation method comprises the steps of setting an index corresponding to a phase variation value constituted of input data, forming a phase value to obtain a phase-modulated output phase value from a given table and forming a channel signal to obtain in-phase (I) and quadrature (Q) channel signals from a given table using the phase value. The apparatus for performing the above comprises a signal converter for converting serially input data into two binary signal trains, a signal forming portion for obtaining channel signals, a digital-to-analog converter for converting the respective signals into two analog signals, a baseband filter for baseband-pass-filtering the signals, a phase shifter for shifting a carrier by 90°, first and second multipliers for multiplying the filtered signals with the carrier and phase-shifted carrier, respectively, and a mixer for mixing the respectively obtained signals and outputting a combined signal. Accordingly, the phase difference according to symbol is implemented alter being assigned to the corresponding index value stored in a look-up table. The final modulation output phase together with the previous phase value is directly obtained by using the look-up table. Accordingly, the construction of the circuit is simplified and the size of the chip is reduced for lower power consumption. Also, modulation speed is improved and a reliable modulation signal can be formed.

Journal ArticleDOI
TL;DR: The optimization of the baseband pulse shape for full response CPM signals, when a noncoherent lowest complexity receiver is used, is carried out and the effective bandwidth is chosen as the objective of the optimization.
Abstract: The optimization of the baseband pulse shape for full response CPM signals, when a noncoherent lowest complexity receiver is used, is carried out. The effective bandwidth is chosen as the objective of the optimization. In order to obtain the minimum error probability for high signal-to-noise ratio, orthogonal signaling is taken into consideration. A closed form for the optimum pulse shape, the value of the optimum modulation index and of the optimum effective bandwidth is determined. The power spectral density and the fractional out-of-band power have been compared with some phase functions considered in the literature. >

Proceedings ArticleDOI
06 Sep 1993
TL;DR: This paper proposes a new 4-dimensional trellis coding technique which can be applied to conventional QPSK modulation, and which leads to substantially reduced levels of spectral regrowth.
Abstract: Band-limited QPSK signals are prone to a high degree of spectral regrowth when nonlinearity is present in the transmitter amplifier. In a multi-carrier application with close adjacent channels (such as an FDMA satellite system), the spectral regrowth of adjacent channels can result in severe interference with the desired carrier. This may lead to substantial BER performance degradation or make necessary an increase in the spacing between carriers. The transmitted carrier may suffer levels of spurious RF emission which exceed system specifications or spectral mask regulations. This paper proposes a new 4-dimensional trellis coding technique which can be applied to conventional QPSK modulation, and which leads to substantially reduced levels of spectral regrowth. When the coding is applied, the modulated signal exhibits a reduced degree of envelope fluctuation, and hence it is less affected by amplitude nonlinearity. The scheme is termed Almost-Constant-Envelope QPSK (ACE-QPSK).

Proceedings ArticleDOI
23 May 1993
TL;DR: Comparisons with other competing signals, e.g., trellis-coded 8 DPSK, show TCCPM signals to be attractive for a wide class of wireless communications systems.
Abstract: A coded modulation scheme based on trellis codes combined with continuous-phase modulated (CPM) signals is considered. Trellis-coded CPM (TCCPM) is a coded modulation technique for the transmission of digital information over bandwidth- and power-limited channels such as satellite-based terrestrial radio links (MSAT). While trellis codes provide power efficiency, the choice of CPM yields constant-envelope signals with good spectral properties. The complexity associated with optimum detection is resolved by using differential symbol-by-symbol detection. The performance of this suboptimum scheme is assessed by simulation. Comparisons with other competing signals, e.g., trellis-coded 8 DPSK, show TCCPM signals to be attractive for a wide class of wireless communications systems. >