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Showing papers on "Continuous phase modulation published in 1988"


Journal ArticleDOI
Bixio Rimoldi1
TL;DR: In this article, it was shown that any continuous-phase-modulation (CPM) system can be decomposed into a continuous phase encoder and a memoryless modulator in such a way that the former is a linear (modulo some integer P) time-invariant sequential circuit and the latter is also time invariant.
Abstract: It is shown that any continuous-phase-modulation (CPM) system can be decomposed into a continuous-phase encoder and a memoryless modulator in such a way that the former is a linear (modulo some integer P) time-invariant sequential circuit and the latter is also time invariant. This decomposition is exploited to obtain alternative realizations of the continuous-phase encoder (and hence of CPM) and also to obtain alternative forms of the optimum decoding algorithm. When P is a prime p so that the encoder is linear over the finite field GF(p), it is shown that cascading it with an outside convolutional encoder is equivalent to a single convolutional encoder. It is pointed out that the cascade of the modulator, the waveform channel (which it is assumed is characterized by additive white Gaussian noise), and the demodulator that operates over one symbol interval yield a discrete memoryless channel that can be studied without the distractions introduced by continuous-phase encoding. >

515 citations


Journal ArticleDOI
TL;DR: The simultaneous data demodulation and phase tracking of an MSK signal using the Viterbi algorithm is described, and two variations of MSK modulation are studied.
Abstract: The simultaneous data demodulation and phase tracking of an MSK signal using the Viterbi algorithm is described, and two variations of MSK modulation are studied. The MSK with overlay is a dual-rate modulation techniques in which low-rate and high-rate data are superimposed on an MSK signal. Here the demodulator uses the Viterbi algorithm to estimate both the low-rate and high-rate data simultaneously. The MSK with pseudorandom sequence spreading combats intentional or unintentional jamming. A simplified receiver for these spread-spectrum MSK signals is found that takes into consideration the effect of random phase perturbations. The performance of these demodulators is evaluated using transfer-function bounds for the bit error probability. For demodulation of the spread spectrum MSK signal, a simplified receiver is derived, and its performance in the presence of continuous jamming is evaluated. >

33 citations


Patent
01 Nov 1988
TL;DR: In this article, a continuous microstrip phase shifter suitable for use in a phased array microwave hyperthermia system operating at 915 MHz is provided, which utilizes a three dB quadrature hybrid coupler in conjunction with microstrip lines to change the phase of a transmitted wave.
Abstract: A continuous microstrip phase shifter suitable for use in a phased array microwave hyperthermia system operating at 915 MHz is provided. The phase shifter utilizes a three dB quadrature hybrid coupler in conjunction with microstrip lines to change the phase of a transmitted wave. The phase change is introduced through the reflection ports of the coupler which are loaded with identical parallel resonant circuits. An abrupt junction varactor capacitance in parallel with a distributed inductance forms a voltage-tunable resonant circuit. The resonant element values are chosen to give a specified continuous phase variation with minimum transmission loss. This is accomplished without additional microwave circuit elements.

26 citations


Journal ArticleDOI
TL;DR: A comparison of different classes of encoded continuous phase modulation (CPM) schemes is presented, and it is found that coded eight- level systems are better than coded four-level systems and that partial- response signalling is better than full-response signalling.
Abstract: A comparison of different classes of encoded continuous phase modulation (CPM) schemes is presented. In terms of joint power-bandwidth performance, it is found that coded eight-level systems are better than coded four-level systems and that partial-response signalling is better than full-response signalling. In general, the price paid for better performance is increased receiver complexity. Heuristic design rules have been used to find good codes for CPM. In most cases the coding gains found are identical to published results that were generated by exhaustive search, indicating that the choice of design rules is quite appropriate. In the present study bandwidth efficiency is considered from both the 99% and 99.9% power-bandwidth points of view. It is found that partial-response signalling is even more jointly power and bandwidth efficient for the latter than for the former bandwidth criterion. >

25 citations


Journal ArticleDOI
TL;DR: An analytical procedure is presented that allows the determination of the optimum pulse shape together with its bandwidth and the minimum-distance characteristics and contains an unknown parameter that is determined by numerical of a nonlinear equation.
Abstract: The problem of minimizing the effective bandwidth of a binary full-response continuous-phase-modulation (CPM) signal with respect to the shape of the frequency pulse for a prescribed value of the minimum Euclidean distance, which is directly related to the error probability for high signal-to noise ratio, is considered. An analytical procedure is presented that allows the determination of the optimum pulse shape together with its bandwidth and the minimum-distance characteristics. The solution contains an unknown parameter that is determined by numerical of a nonlinear equation. The results are compared to some standard pulses in terms of bandwidth, spectral density, minimum Euclidean distance, and error probability. Some gain in bandwidth is obtained for high values of minimum distance. >

23 citations


Journal ArticleDOI
TL;DR: The free Euclidean distance is the best one-parameter description of the error probability for the considered class of signals for high signal-to-noise ratios, but the upper bound results show that the free distance alone yields pessimistic bit error probability behavior for some interesting cases.
Abstract: The bit error probability properties of signals consisting of convolutional coding combined with partial-response multilevel continuous phase modulation (CPM) are studied. It is assumed that the channel is an additive white Gaussian noise channel and that the receiver performs coherent maximum-likelihood sequence detection by means of the Viterbi algorithm. An upper bound on the bit error probability is derived, using the average generating function technique, and evaluated numerically for a number of coded multilevel full-response CPM schemes. Simulation results are also presented. It is concluded that the free Euclidean distance is the best one-parameter description of the error probability for the considered class of signals for high signal-to-noise ratios. However, the upper bound results show that the free distance alone yields pessimistic bit error probability behavior for some interesting cases. >

13 citations



Patent
Thad J. Genrich1
29 Apr 1988
TL;DR: In this article, a general purpose continuous phase modulator is presented, which greatly reduces the amount of memory and associated hardware complexity traditionally found in continuous phases modulators, and includes a phase accumulator which calculates the phase state in an on-line real-time fashion.
Abstract: A general purpose continuous phase modulator is shown which greatly reduces the amount of memory and associated hardware complexity traditionally found in continuous phase modulators. The continuous phase modulator includes a phase accumulator which calculates the phase state in an on-line real time fashion. As a result, a continuous phase modulator is provided which is adaptable to any transmitter or transceiver product requiring power and bandwidth efficiency such as those found in satellite communications equipment.

11 citations


Proceedings ArticleDOI
15 Jun 1988
TL;DR: Noncoherent detection of constant envelope digital partial response continuous phase modulation (PRCPM) in fast Rayleigh fading characterizing land mobile radio channels is analysed.
Abstract: Summary form only given. Future mobile radio systems are expected to provide high-quality voice and high-speed data transmission and to be integrated into the digital communication networks in several countries. The performance of some digital modulation techniques that are relevant for future mobile radio systems is studied. These techniques are characterized by having a constant envelope signal to reduce the effect of nonlinearity and fading and a compact RF power spectrum to reduce adjacent channel interference. Most digital partial-response continuous-phase modulation (PRCPM) techniques such as 2 RC, 2 SRC, 2 RC, 3 SRC, GMSK, and GTFM have the above properties. Discriminator detection of these techniques is analyzed in fast Rayleigh fading characterizing land mobile radio channels. Approximate closed-form expressions for the probability of error are derived and numerical results are presented for land mobile radio systems. >

10 citations


Journal ArticleDOI
T.G. Hodgkinson1, R.P. Webb1
TL;DR: In this article, it is shown that spontaneous lifetime produces a phase shift which causes an interchange of power between channels, which can be used to analyse the carrier density modulation caused by interchannel beat powers.
Abstract: It is shown that standard communications phase modulation theory can be used to analyse the carrier density modulation caused by interchannel beat powers. Also, it is shown that spontaneous lifetime produces a phase shift which causes an interchange of power between channels.

10 citations


Patent
20 Sep 1988
TL;DR: In this paper, an instantaneous comparison unit with an associated sequential state logic circuit is described which functions to maintain a condition of phase locking with a reference signal which is substantially immune to disturbances which cause losses or additions of signal fronts.
Abstract: An instantaneous comparison unit with an associated sequential state logic circuit is described which functions to maintain a condition of phase locking with a reference signal which is substantially immune to disturbances which cause losses or additions of signal fronts. Continuous phase shifting conditions during the transient, which precedes phase locking, is detected and compensated for by the disclosed circuit.

Proceedings ArticleDOI
13 Jun 1988
TL;DR: In this paper, the average power spectral density is calculated by the Aulin-Sundberg method adapted to multiamplitude continuous phase modulation (MACPM) signals and the energy-bandwidth tradeoff is presented.
Abstract: Average power spectral density is calculated by the Aulin-Sundberg method adapted to multiamplitude continuous phase modulation (MACPM) signals. Arbitrary baseband symbol pulse shapes and durations, the modulation indices, the number of symbol levels, their probabilities and different amplitude values of the larger CPM signal component can be used. The upper bounds on the normalized minimum squared Euclidean distances are calculated for full-response MACPM signals. The energy-bandwidth tradeoff is presented. >

Journal ArticleDOI
01 Jan 1988
TL;DR: In this paper, a method of constructing a frequency synthesizer with a short settling time is suggested, based on a double-loop phase-locked loop which has a short convergence time and on a continuous-phase divider that matches the VCO (voltage-controlled oscillator) frequency to the reference frequency.
Abstract: A method of constructing a frequency synthesizer with a short settling time is suggested. The frequency synthesizer is based on a double-loop phase-locked loop which has a short convergence time and on a continuous-phase divider that matches the VCO (voltage-controlled oscillator) frequency to the reference frequency. >

Patent
20 May 1988
TL;DR: In this article, the continuous phase modulation of a carrier wave (CPM) in a time-dependent envelope curve is described, and the estimated symbols are determined with an optimization algorithm.
Abstract: During a signal transmission process, digital data are reproduced in a transmitter in accordance with a given process for the continuous phase modulation of a carrier wave (CPM) in a time-dependent envelope curve, the envelope curve is transmitted by the carrier wave via a channel with a given unit pulse response, an additive, white Gaussian noise being superimposed, the digital data are sent through a channel-specific filter and sampled in a receiver, and a sequence of estimated symbols is determined with an optimization algorithm.

Proceedings Article
11 Sep 1988
TL;DR: In this article, phase-insensitive zero-IF coherent optical detection is achieved by imposing a periodic phase modulation on the transmitter carrier or local oscillator and a single-branch receiver is used.
Abstract: The authors present a simplification of their previously proposed technique in which phase-insensitive zero-IF coherent optical detection is achieved by imposing a periodic phase modulation on the transmitter carrier or local oscillator and a single-branch receiver is used >

Proceedings ArticleDOI
12 Jun 1988
TL;DR: It is demonstrated that the error rate performance of continuous phase modulation (CPM), when detected using a limiter discriminator followed by a 2-bit integrate-and-dump filter (IDF), is far superior to the performance obtained using a discriminator following by a 1-bit IDF.
Abstract: It is demonstrated that the error rate performance of continuous phase modulation (CPM), when detected using a limiter discriminator followed by a 2-bit integrate-and-dump filter (IDF), is far superior to the performance obtained using a discriminator followed by a 1-bit IDF The performance obtained at a modulation index h=1/2 is quite comparable to that of the 2-bit differentially coherent detector A parameterized performance study shows that drastic improvements are achievable by properly selecting the modulation index and simultaneously optimizing the receive filter bandwidth The investigation also shows that the error performance is sensitive to the type of IF filter response, ie, the Butterworth response yields superior performance in comparison to the Gaussian filter response >

Proceedings ArticleDOI
28 Nov 1988
TL;DR: The authors consider a satellite-based mobile communication scheme based on continuous-phase modulated (CPM) signals used in conjunction with trellis-coded modulation (TCM) and describe the system and its performance, and then they investigate how to estimate the frequency shift induced in the received signal by the Doppler effect.
Abstract: The authors consider a satellite-based mobile communication scheme based on continuous-phase modulated (CPM) signals used in conjunction with trellis-coded modulation (TCM). This scheme provides a power saving due to the coding gain of TCM, and simultaneously a reduced bandwidth occupancy due to the particular structure of CPM signals. Moreover, CPM provides constant-envelope signals, which is a requirement for satellite transponders operating in a time-division multiple-access mode. To keep the complexity manageable, a detection scheme based on differential detection of CPM is used. They describe the system and its performance, and then they investigate how to estimate the frequency shift induced in the received signal by the Doppler effect. >

Journal ArticleDOI
Arne Svensson1
TL;DR: The author shows that quaternary schemes outperform binary schemes, when the schemes are compared in a power-bandwidth tradeoff.
Abstract: A matched-filter differential detector for continuous phase modulation is proposed and simulated error probability for this detector is presented. The detector consists of a conventional differential detector operating with a delay, a bank of matched filters, and a Viterbi processor to perform sequence decision. The author shows that quaternary schemes outperform binary schemes, when the schemes are compared in a power-bandwidth tradeoff. Schemes that lose about 3.4 dB compared to coherently detected minimum shift keying (MSK) at 10/sup -3/ on a Gaussian channel, but with a bandwidth of about 0.6 times the MSK bandwidth, are presented. >

Patent
07 Nov 1988
TL;DR: In this paper, an improved circuit for pulsed biphase modulation of a sine wave carrier having the same frequency as the clock frequency selects carrier phase deviations from static phase shift circuits by means of multiple bilateral semiconductor switches which are controlled by coded pulses generated in a digital processing cirucit receiving NRZ digital data.
Abstract: An improved circuit for pulsed biphase modulation of a sine wave carrier having the same frequency as the clock frequency selects carrier phase deviations from static phase shift circuits by means of multiple bilateral semiconductor switches which are controlled by coded pulses generated in a digital processing cirucit receiving NRZ digital data The switches are controlled by the pulses to disconnect the carrier and to connect the phase deviations to the output at the start and at the middle of a cycle of the carrier frequency

Proceedings ArticleDOI
12 Jun 1988
TL;DR: It is shown through simulations that performance close to the optimal receiver can be obtained while realizing significant computational savings.
Abstract: The decoding of signals in infinite intersymbol interference caused by severe filtering is considered. A state-variable representation of a linear system is used to define the decoder tree. Tree decoding is then performed by the M-algorithm. It is shown through simulations that performance close to the optimal receiver can be obtained while realizing significant computational savings. Binary phase-shift keying with rectangular baseband pulse shaping and continuous phase/frequency-shift-keyed signals are considered. The channel is modeled as a narrowband filter with two and four-pole Butterworth spectra with symbol-rate normalized 3-dB bandwidths of 0.1 and 0.25. >

Proceedings ArticleDOI
28 Nov 1988
TL;DR: In this article, the minimum Euclidean distances for binary three-hop and four-hop schemes and power spectra for three-and four-hops were derived for each scheme.
Abstract: Multihop phase-coded modulation (MHPM) using asymmetric modulation indices corresponding to the bipolar data+1 and -1 is considered, and numerically obtained values of the minimum Euclidean distances for binary three-hop and four-hop schemes and power spectra for three-hop schemes are provided. It is shown that improved error probability is obtained compared to conventional MHPM with essentially no bandwidth expansion. >

Proceedings ArticleDOI
D. Makrakis1, K. Feher1
11 May 1988
TL;DR: A sequential decoder for the differential detection of continuous-phase-modulation (CPM) signals is introduced that is derived in a general form and can be applied to any CPM scheme with any number of differential detectors.
Abstract: A sequential decoder for the differential detection of continuous-phase-modulation (CPM) signals is introduced. The decoder is based on the use of multiple differential detectors and takes advantage of a self-encoding process introduced by the differential detection. The algorithm is derived in a general form and can be applied to any CPM scheme with any number of differential detectors. The decoder has been evaluated for the case of tamed frequency modulation (TFM) and Gaussian minimum-shift keying (GMSK) with B/sub t/T=0.25, under additive white Gaussian noise and multipath propagation conditions. The BER performance results indicated significant gains. In additive white Gaussian noise, an improvement of 8.2 dB over the conventional differential receiver has been achieved. Under fading conditions the gains become even higher, indicating that the decoders perform significantly better than conventional detectors under multipath propagation. >

Journal ArticleDOI
TL;DR: A discriminator detector using decision feedback for continuous phase modulation (CPM) is proposed, which leads to an improved performance, especially for high signal/noise ratios.
Abstract: A discriminator detector using decision feedback for continuous phase modulation (CPM) is proposed. Different thresholds are employed in the hard decision device owing to the memory in the CPM signal. This leads to an improved performance, especially for high signal/noise ratios. Parameters such as bandwidth of the IF filter, sampling time and integration time are optimised.

Proceedings ArticleDOI
15 Jun 1988
TL;DR: In this article, two coding methods to enable in-band operation of pilot-aided synchronization techniques are introduced, i.e., KF10 and OF00, which enable a triple-pilot scheme to be conceived to provide a symbol timing with no 180 degrees phase ambiguity.
Abstract: Two coding methods to enable in-band operation of pilot-aided synchronization techniques are introduced. By operating on baseband equivalent QAM, i.e. PAM symbol streams, the new codes generate power spectral notches at the Nyquist frequency with fairly low redundancy. One of the codes, called KF10, generates a power spectral notch at the Nyquist frequency, so that the dual-pilot tone calibration technique can be arranged to convey both a symbol timing and carrier reference to the receiver. The second code, called OF00, generates a notch at zero as well as the Nyquist frequency, and so enables a triple-pilot scheme to be conceived to provide, in addition to a symbol timing, a carrier reference with no 180 degrees phase ambiguity. Through comparison with previous codes used in real systems, it is shown that the codes generate spectral notches of the same quality as others, yet reducing the required redundancy by as much as 400% in the case of 256-QAM application. Various simulation results confirm the coding effects. >

Proceedings ArticleDOI
12 Jun 1988
TL;DR: The method of multiple trellis-coded modulation is applied to continuous phase modulation (CPM) and the results are clearly superior to single trellIS-coded schemes with 1/2-rate codes.
Abstract: The method of multiple trellis-coded modulation is applied to continuous phase modulation (CPM). Double trellis-coded quaternary CPM schemes using convolutional codes with an effective rate of 2/4 are considered. Tables of optimum codes and minimum Euclidean distances are given for several frequency impulses and ratios of trellis-branches-per-symbol-interval, which have to be processed by a Viterbi-decoder. The results are clearly superior to single trellis-coded schemes with 1/2-rate codes. These improvements are accomplished by a proper selection of double-channel symbols. This method also offers improved receiver implementation properties. For a further reduction of complexity, a modified decision-feedback-sequence estimation is proposed. >

Proceedings ArticleDOI
01 Dec 1988
TL;DR: It is found that the nonuniform multihop coded CPM achieves larger Euclidean distance and diminishes the number of merge events up to a certain depth in the state trellis, thereby improving the strict bit error probability.
Abstract: Convolutional coding combined with continuous phase modulation (CPM) has shown the good tradeoff between coding and bandwidth. The authors propose the use of coded CPM with a nonuniform signal constellation and a multihop scheme to achieve further coding gains over the conventional uniform-mapping single-hop coded CPM. The strict bit error probability and the number of merge events are proposed as criteria for evaluating the average performance of the system. With these estimated criteria, the performance of the uniform multihop coded CPM is analyzed. It is found that the nonuniform multihop coded CPM achieves larger Euclidean distance and diminishes the number of merge events up to a certain depth in the state trellis, thereby improving the strict bit error probability. >

Proceedings ArticleDOI
15 Jun 1988
TL;DR: For the limiter-discriminator detection of continuous phase modulation (CPM) signals, a sequential detector is introduced that takes into account the strong noise correlation between the successive noise samples of the received signal, and uses it in the estimation process.
Abstract: For the limiter-discriminator detection of continuous phase modulation (CPM) signals, a sequential detector is introduced. The decoder takes into account the strong noise correlation between the successive noise samples of the received signal, and uses it in the estimation process. The algorithm has been evaluated for minimum shift keying (MSK) and duobinary MSK, both in additive white Gaussian noise and fading conditions. In comparison with the conventional symbol-by-symbol detector, the technique offers gains of 2.25 dB for the MSK and 2.8 dB for the duobinary MSK (at BER=10/sup -4/). It outperforms the conventional Viterbi decoder (applied on a duobinary MSK signal) by 1 dB. >

DOI
01 Dec 1988
TL;DR: The results show that a net improvement in the throughput and error probability can be achieved by using this technique with respect to the classical protocols.
Abstract: The integration of the modulation operation in the structure of some automatic-repeat-request protocols is analysed. Continuous phase modulation schemes are considered together with block and convolutional codes. The optimum structure of channel coding and modulation is determined through a computer search. The results show that a net improvement in the throughput and error probability can be achieved by using this technique with respect to the classical protocols.

Proceedings ArticleDOI
23 Oct 1988
TL;DR: The authors analyze incoherent detection of trellis-coded continuous-phase M-ary FSK, using M quadrature receivers and trellIS decoding, and obtain upper bounds on the probability of error and symmetric and asymmetric signal constellations.
Abstract: The authors analyze incoherent detection of trellis-coded continuous-phase M-ary FSK, using M quadrature receivers and trellis decoding. The upper bounds on the bit error rate as well as the 99% energy bandwidths are given for the codes under consideration. In particular, the authors consider trellis codes with rates of 1/2 and 2/3 with symmetric and asymmetric signal constellations. The upper bounds on the probability of error are obtained for symmetric and optimum asymmetric signal constellations. The optimum asymmetry is one which minimizes the probability of bit error. The performance of this system is compared with that of standard continuous-phase modulation techniques (MSK, duobinary, and TFM) using noncoherent detection. >

Proceedings ArticleDOI
15 Jun 1988
TL;DR: In this article, the mean square error optimum receiver filter (MSEOF) was proposed for detection of continuous phase modulation (CPM) signals with modulation index h = 1/2.
Abstract: Detection of continuous phase modulation (CPM) signals with modulation index h=1/2 can be achieved using minimum shift keying (MSK)-type receivers with only minor degradation relative to maximum likelihood (Viterbi algorithm) receivers. Performance of such receivers is highly sensitive to both the filter response and the modulation scheme. The authors analyze the mean-square-error optimum receiver filter (MSEOF) among a selected set of MSK-type receiver filters, based on signal-to-mean-square-crosstalk ratio and error probability criterion in an interfacing environment. >