Phase Shift Keying Demodulator Research Articles

M-PSK Demodulator With Joint Carrier and Timing Recovery

In this brief, we propose a new digital receiver for Phase-Shift Keying (PSK) modulation based on the integration of the conventional digital Costas Loop circuit with a new timing recovery method. The timing recovery is applied to the PSK demodulator using an Iterative Learning Control (ILC) law and it is based on the minimization of the intersymbol interference using only one sample per symbol. The main advantage of the proposed timing recovery method is the insensitivity to frequency offsets which results in improved performance and robustness of the Costas Loop circuit. Experiments comparing a conventional receiver (cascade of Costas Loop and Early-Late Timing Synchronizer) to the proposed receiver in scenarios characterized by low signal-to-noise ratios and large frequency and phase errors, show that the time needed to reduce the errors of the proposed receiver is seven times smaller than the conventional receiver. Moreover, the impact of the proposed method on the necessary hardware resources (area and power consumption) is negligible.

An ADPLL-Based PSK Receiver for VHBR 13.56-MHz Contactless Smartcards and NFC Applications

This brief proposes an all-digital phase-locked loop (ADPLL) used as the phase-shift keying (PSK) receiver for a very high bit rate of 13.56-MHz smartcards. A detailed implementation from system to circuit level is presented. This ADPLL-based PSK demodulator mainly consists of a high dynamic range time to digital converter (TDC) without pulse shrinking effect, a dual-path digital loop filter, and a fine resolution digital controlled oscillator based on capacitor division without dithering. This design is fabricated by GF CMOS 40-nm technology with a core area of only 0.035 mm2. The measurement results show low current consumption of 40 mA for phase locking and 70 mA for PSK demodulation with 1.2-V supply. Both integral non-linearity and differential non-linearity of our TDC are smaller than 0.6 LSB. This prototype can demodulate 8-PSK at a symbol rate of 6.78 MHz, corresponding to a data rate of 20.34 Mb/s, with an energy efficiency of 4.1 pJ/bit.

Detection of phase-shift keyed signals with gradual phase change during reception on the background of noise

The detection characteristics of phase-shift keyed radar signal (PSKS) with gradual phase change obeying the Barker law have been considered. Analytical expressions were obtained for the PSKS detection characteristics under conditions of different a priori data regarding the signal parameters on the basis of calculations. It was shown that the gradual phase change lead to insignificant deterioration of the probability of the PSKS correct detection as compared with the stepwise phase change.

Signal activity detection of phase-shift keying signals

We propose computationally inexpensive and efficient solutions for signal activity detection of phase-shift keying (PSK) signals in additive white Gaussian noise. We consider the complex amplitude of the signal, as well as the information sequence, as the unknown parameters. In addition, the noise variance is assumed unknown. We derive the generalized likelihood ratio test (GLRT) and suggest a computationally efficient implementation thereof. Furthermore, we develop a new inexpensive detector for binary PSK signals, which we will refer to as the generalized energy detector. To evaluate the performance of these detectors, we attempt to derive a uniformly most powerful invariant (UMPI) test as an optimal detector. It turns out that the UMPI test exists only if the signal-to-noise ratio is known. We use this UMPI test in order to obtain an upper-bound performance for the evaluation of invariant detectors, such as the GLRT. Simulation results illustrate and compare the performance and the efficiency of the proposed signal activity detectors

Signal Activity Detection of Phase-Shift Keying Signals

We propose computationally inexpensive and efficient solutions for signal activity detection of phase-shift keying (PSK) signals in additive white Gaussian noise. We consider the complex amplitude of the signal as well as the information sequence as the unknown parameters. In addition, the noise variance is assumed unknown. We derive the generalized likelihood ratio test (GLRT) and suggest a computationally efficient implementation thereof. Furthermore, we develop a new inexpensive detector for binary PSK signals, which we will refer to as the generalized energy detector. To evaluate the performance of these detectors, we attempt to derive a uniformly most powerful invariant test (UMPI) as an optimal detector. It turns out that the UMPI test exists only if the signal-to-noise ratio is known. We use this UMPI test in order to obtain an upper-bound performance for the evaluation of invariant detectors, such as the above-mentioned GLRT. Simulation results illustrate and compare the performance and the efficiency of the proposed signal activity detectors.

Iterative demodulation and decoding of frequency-hopped PSK in partial-band jamming

This paper considers the problem of developing and utilizing side information in a frequency-hopped communication system using phase-shift keying (PSK) and operating in an environment with partial-band jamming. Two aspects of side information are studied. The first deals with estimating the unknown random carrier phase that varies from hop to hop. The second aspect is the detection of jamming signals. We use a serially concatenated convolutional code structure with differential M-ary PSK as the inner code. The iterative receiver uses an expanded trellis in the inner decoder to resolve the phase ambiguity and is augmented by a ratio-threshold test for detecting jammer energy. Performance is compared for different dwell interval lengths and both log-APP and max-log-APP decoding algorithms. This paper also considers the effect of different thresholds on the false alarm and detection probabilities of the ratio-threshold test.

A simple scheme for PSK demodulation

In recent years, Phase Shift Keying (PSK) has been often used for digital modulation of satellite link because of its good noise resistance. The PSK demodulation requires complex hardware which becomes a constraint for some applications. In this paper a new scheme is proposed for the demodulation. When compared to conventional schemes such as costas loop and square loop, the proposed scheme uses a very simple technique and requires very less hardware for the realization. But the scheme is more suitable for low noise environment applications such as the one discussed in the paper. Performance analysis of the proposed scheme is also briefly presented here.

Spectrally efficient noncoherent communication

This paper considers noncoherent communication over a frequency-nonselective channel in which the time-varying channel gain is unknown a priori, but is approximately constant over a coherence interval. Unless the coherence interval is large, coherent communication, which requires explicit channel estimation and tracking prior to detection, incurs training overhead which may be excessive, especially for multiple-antenna communication. In contrast, noncoherent detection may be viewed as a generalized likelihood ratio test (GLRT) which jointly estimates the channel and the data, and hence does not require separate training. The main results in this paper are as follows. (1) We develop a space criterion for signal and code design for noncoherent communication, in terms of the distances of signal points from the decision boundaries. (2) The noncoherent metric thus obtained is used to guide the design of signals for noncoherent communication that are based on amplitude/phase constellations. These are significantly more efficient than conventional differential phase-shift keying (PSK), especially at high signal-to-noise ratio (SNR). Also, known results on the high-SNR performance of multiple-symbol demodulation of differential PSK are easily inferred from the noncoherent metric. (3) The GLRT interpretation is used to obtain near-optimal low-complexity implementations of noncoherent block demodulation. In particular, this gives an implementation of multiple symbol demodulation of differential PSK, which is of linear complexity (in the block length) and whose degradation from the exact, exponential complexity, implementation can be made as small as desired.

Carrier detection of PSK signals

This paper reports on a theoretical study of the detection of the 2f and 4f carrier components of phase-shift keying (PSK) signals produced by passing signal and noise through a nonlinear device. Unbalanced quadrature PSK (QPSK) signals, i.e., QPSK signals with unequal power in the two channels, are studied. The complete range of channel power ratio is covered, with equal emphasis on the general unbalanced case and the two limiting cases of binary PSK and (balanced) QPSK. Analytic expressions are derived for the detected SNR of carrier harmonics 2f and 4f as a function of SNR, channel power ratio, and normalized input bandwidth. The results apply equally well to PSK data signals and direct-sequence spread-spectrum signals. Measurements confirm every aspect of the theory. The least detectable signal type is balanced QPSK, which is detectable (at 4f) at a threshold SNR ranging from -2 to -13 dB as the detection process gain (chip or data rate/detection bandwidth) is varied from 40 to 80 dB.