Frank Carden

A quantized Euclidean soft-decision maximum likelihood sequence decoder for TCM

The authors discuss the use of quantized Euclidean soft-decision maximum-likelihood sequence decoders on trellis-coded 8-PSK communication schemes. A model is developed for the circularly quantized Euclidean decoder, and computer simulations are used to evaluate it. Degradation is determined as a function of the number of sectors used in the circular quantization.<<ETX>>

Fast TCM decoding: phase quantization and integer weighting

TCM, combining modulation and coding, achieves coding gains over conventional uncoded multilevel modulation without the attendant bandwidth expansion. Since TCM was proposed Ungerboeck (1982, 1987) substantial work has done in this area. A large portion of the TCM work has been in the area of high-speed data transmission over voice grade modems using quadrature amplitude modulation, QAM. QAM, not having a constant envelope, is unattractive for employing a TWT with its nonlinear behavior as the power stage. Additional work has been done in utilizing M-ary PSK with TCM. Simulations by Taylor and Chan (1981) utilizing a 4-state convolutional code demonstrated the coding gain of a rate 2/3 coded 8-PSK modulation scheme. Wilson et. al. (1984) obtained results for 16-PSK TCM using codes with 4 to 32 states and achieved coding gains of 3.5 to 4.8 dB respectively, over 8-PSK and demonstrated that small memory codes achieved good gains with simple design procedures. >

Pragmatic trellis coded modulation: a simulation using 24-sector quantized 8-PSK

Pragmatic trellis coded modulation (TCM) uses the industry standard, 64-state, binary convolutional code. The authors present the logic design and simulation results for a system which effectively implements pragmatic TCM for rate 2/3 encoded 8 phase shift keying (PSK). This system associates each sector of a quantized phase receiver with a pair of weights to be used as soft decision inputs of the Viterbi decoder. This system approaches 3 dB of coding gain at bit error rates of 10/sup -5/ and less.<<ETX>>

A Multifilter Phase-Lock Loop

The phase model for the generalized multifilter phaselock loop (M PLL) is considered and state equations for this model are derived. A linear analysis is presented to aid in the preliminary design of an M PLL and to indicate the noise improvement over a conventional phase-lock loop (PLL). Performance characteristics are examined for an M PLL with low-pass and bandpass characteristics used in a specific FM communication system. Both single and double sinusoidal FM are used and a region of proper operation of the M PLL is determined in terms of modulation index and modulating frequency. These results are obtained from both analog and digital computer simulation of the nonlinear system.

Pragmatic trellis coded modulation: a hardware implementation using 24-sector 8-PSK

The authors present the construction and test results of a system which implements pragmatic trellis coded modulation (TCM) for rate 2/3 encoded 8-PSK (phase shift keying). Pragmatic TCM is described. This system associates each sector of a quantized phase receiver (F. Carden et al., 1988) with a pair of weights to be used as soft decision inputs of the Viterbi decoder. This system approaches 3 dB of coding gain at bit error rates of 10/sup -5/ and less.<<ETX>>

Multi-mode modem/codec designs

The design of an integrated modem/codec unit which can receive coded and uncoded BPSK an QPSK using de facto standard coding schemes as well as 8PSK-TCM and 16PSK-TCM is examined. The design is totally compatible with todays modulation schemes and capable of processing tomorrows TCM codes. This is accomplished in the modem by using quadrature channel carrier recovery processing and a version of the MAP phase detector algorithm. The symbol synchronization is accomplished with a derivative of an early-late gate designed to accommodate multilevel signals.

Possible harmonic-wavelet hybrids in image compression

The paper describes some image compression research at New Mexico State University. It explores the possibility of combining multi-resolution and harmonic analysis in signal decomposition. This is in recognition of the fact that both local and global characteristics are found in most images and that the ideal compression system should be able to contend with both types of features. A hybrid is proposed and discussed.<<ETX>>

A laboratory minimum shift key modulator

Minimum shift keying (MSK) is a modulation format that exhibits some spectral efficiency over currently used spacelink digital modulation techniques such as binary phase shift keying (BPSK) and offset quadrature phase shift keying (OQPSK). The authors present a novel design of an MSK modulator that is well suited for investigating MSK in the laboratory. MSK obtains its advantage over OQPSK through the use of some elaborate timing. One of the costs of this required timing is added complexities in the modulator circuitry. Phase locked loops and an extra phase shift are required to modify a simple OQPSK modulator to perform MSK. Digital timing circuitry, including digital phase shifting, can be used in conjunction with inexpensive laboratory function generators to construct a simple MSK modulator that avoids the complexities of the modified OQPSK design technique. These design techniques are described.<<ETX>>

Phase-Lock Loop Characteristics in the Presence of Nonwhite Noise for Bandpass Types of Modulating Spectra

In this concise paper the phase-lock loop (PLL) steady state characteristics for bandpass types of modulating spectra are determined. The usual assumption that the intermediate frequency (IF) bandwidth is wide compared with PLL bandwidth is not made. The characteristics are determined from measurements on an experimental system and from theoretical calculations using a quasi-linear model (QLM) of the PLL. Experimental data are compared to theoretical data to determine the accuracy of the QLM over the PLL parameter space. The experimental results are used to provide design data and to arrive at conclusions concerning threshold, multiplier output variance, phase error variance, output signal-to-noise ratio, and signal distortion.