Amplitude Modulation Receiver Research Articles

Optimization Strategies for Rydberg Atom-based AM Receiver Operational Parameters

Abstract The Rydberg atom-based receiver, as a novel type of antenna, demonstrates broad application prospects in the field of microwave communications. However, since Rydberg atomic receivers are nonlinear systems, mismatches between the parameters of the received amplitude modulation (AM) signals and the system's linear workspace and demodulation operating points can cause severe distortion in the demodulated signals. To address this, the article proposes a method for determining the operational parameters based on the mean square error (MSE) and total harmonic distortion (THD) assessments, and presents strategies for optimizing the system’s operational parameters focusing on linear response characteristics (LRC) and linear dynamic range (LDR). Specifically, we employ a method that minimizes the MSE to define the system’s linear workspace, thereby ensuring the system has a good LRC while maximizing the LDR. To ensure the signal always operates within the linear workspace, an appropriate carrier amplitude is set as the demodulation operating point. By calculating the THD at different operating points, the LRC performance within different regions of the linear workspace is evaluated, and corresponding optimization strategies based on the range of signal strengths are proposed. Moreover, to more accurately restore the baseband signal, we establish a mapping relationship between the carrier Rabi frequency and the transmitted power of the probe light, and optimize the slope of the linear demodulation function to reduce the MSE to less than 0.8×10-4. Finally, based on these methods for determining operational parameters, we explore the effects of different laser Rabi frequencies on system performance, and provide optimization recommendations. This research provides robust support for the design of high-performance Rydberg atom-based AM receivers.

Empirical laser measured with optical coherent quadrate amplitude modulation receiver for upgrading fiber optic systems

Abstract The work clarified the empirical laser measured with optical coherent quadrate amplitude modulation receiver for upgrading fiber optic systems. Peak signal amplitude and output power spectrum are measured after light receivers under the control of extinction modulator ratio, radio frequency switching voltage and switching bias voltage. The better the fiber optic system performance can be achieved with the higher values of extinction ratio, both switching radio frequency and bias voltages based LiNb modulators.

Inverter Based Ultra‐Low Power Demodulation Circuit for AM Receivers

AbstractWireless communication with AM (Amplitude Modulation) is widely used. If the power consumption of the AM receiver is reduced to the utmost limit, the power source can be replaced with an energy harvest, which is very convenient. Power lines will not be needed and batteries will no longer need to be replaced or recharged. Therefore, we propose an ultra‐low power demodulation circuit for AM receivers. The proposed demodulator achieved a peak SNDR of 47.8 dB and a power consumption of 3.36 μW at a carrier frequency of 1 MHz. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

A Quadrature Amplitude Modulation Receiver Model with Matched Filters

In this study, it is mathematically shown that the detector inputs obtained using the matched filters in the Quadrature Amplitude Modulation (QAM) receiver are the same expressions as those obtained using the integrators if a rectangular pulse is used in the transmitter and the channel is Additive White Gaussian Noise (AWGN). Under the assumption that there is a perfect synchronization between the transmitter and the receiver. QAM is intensively used at the present time for the data transmission on subchannels in orthogonal frequency-division multiplexing (OFDM) communication systems such as digital subscriber lines (DSLs) modems, wireless local area networks (WLANs) and cellular wireless communication systems (e.g. 4G LTE). Cyclic-prefix OFDM is deployed in 4G LTE systems and the rectangular pulse is used in the time domain to shape all subcarriers of OFDM.

Compensation of Laser Frequency Fluctuations and Phase Noise in 16-QAM Coherent Receivers

Frequency fluctuations caused by mechanical vibrations, power supply noise, and other mechanisms are detrimental to the phase estimator performance in high speed intradyne coherent optical receivers. In this letter, we propose the use of a low-latency parallel digital phase lock loop in combination with common feed-forward carrier phase recovery algorithms in order to compensate both the phase noise and laser frequency fluctuation effects on 16-quadrature amplitude modulation receivers. Numerical results demonstrate the excellent behavior of the proposed two-stage carrier recovery scheme.

Effect of interpolation filter in digital quadrature amplitude modulation signal resampling

In this study, a closed-form equation is derived which relates the mean-squared error (MSE) to the frequency response of the interpolation filter. Effects of additive white Gaussian noise and timing jitter on the MSE are accounted for in the equation. By using properties of the Nyquist signalling pulse, a simple approximation to the MSE equation is obtained, which is found to be accurate over the range of excess bandwidths commonly used in quadrature amplitude modulation receivers.

A novel phase-noise compensation scheme for communication receivers

A novel phase-noise (PHN) compensation method is proposed in this paper. The proposed approach uses the information provided by an additional signal path that is added with modest hardware overhead to better estimate the PHN. In this signal path, the oscillator output is self-downconverted to the baseband by mixing itself with a delayed and conjugated replica, so as to provide PHN information that is free from data modulation. A joint prediction and smoothing Wiener filter can then be employed to obtain the minimum mean-squared error estimate of the PHN. There are generally two types of PHN models commonly used in the literature: stationary PHN and Wiener PHN. Both types of PHN are considered in this paper. Adaptive schemes are also presented using the least-mean square algorithm and recursive least-square algorithm. Simulations of a 64-quadrature amplitude modulation receiver confirm the analysis results of the PHN estimation performance, and show that the proposed method can improve the receiver performance significantly over the conventional schemes.

Low timing sensitivity receiver structures for CAP

Carrierless amplitude and phase (CAP) is one of the modulation schemes that has been proposed to accomplish the task of transporting high bit-rate data over cheap copper wire pairs. In this paper, we reexamined some CAP receiver structures that have been proposed in the literature and showed that the modified quadrature amplitude modulation receiver can offer a significant advantage over the other receiver structures through its greater immunity to timing phase errors. Our recommendation is based on an analysis of the eye diagram of a received CAP signal.

Polynomial perceptrons and their applications to fading channel equalization and co-channel interference suppression

This paper investigates the behaviors of polynomial perceptrons and introduces a fractionally spaced recursive polynomial perceptron with low complexity and fast convergence rate. The nonlinear mapping ability of the polynomial perceptron is analyzed. It is shown that a polynomial perceptron with degree L(/spl ges/4) satisfies the Stone-Weierstrass theorem and can approximate any continuous function to within a specified accuracy. Moreover, the nonlinear mapping ability of a polynomial perceptron with degree L is similar to that of the three-layer perceptron with one hidden layer for time same number of neurons in the input layer. The nonlinear mapping ability of the fractionally spaced recursive polynomial perceptron is also presented. Applications of polynomial perceptrons for fading channel equalization and co-channel interference suppression in a 16-level quadrature amplitude modulation receiver system are considered. Computer simulations are used to evaluate and compare the performance of polynomial perceptron (PP) and fractionally spaced bilinear perceptron (FSBLP) with that of the synchronous decision feedback multilayer perceptron (SDFMLP), fractionally spaced decision feedback multilayer perceptron (FSDFMLP), and the conventional decision feedback equalizer (DFE). The results show that the performance of the fractionally spaced bilinear perceptron is clearly superior to that of the other structures. >

Discussion on “Impulsive interference in amplitude-modulation receivers”

Discussion on “Impulsive interference in amplitude-modulation receivers”

Impulsive interference in amplitude-modulation receivers

Impulsive interference in amplitude-modulation receivers

Impulsive interference in amplitude-modulation receivers

An analysis is made of the response of an a.m. receiver to impulsive interference (of the type generated by car ignition systems) using the Fourier integral theorem. Conclusions concerning the general behaviour of receivers are deduced from the formulae developed. The method is then applied to the calculation of the performance of noise suppressor circuits which are classified as amplitude, differential and delay limiters. Simple expressions are derived for estimating the suppression attainable in any particular case.Some experiments are described in which the performance of the first two types of noise suppressor was measured. There is shown to be fair agreement with the calculated values.A comparison is made between the behaviour of frequency modulated, pulse-length-modulated and suppressed amplitude-modulated systems with impulsive interference.

The Influence of Amplitude Limiting and Frequency Selectivity upon the Performance of Radio Receivers in Noise

This paper describes an experimental study of the relations which exist between the effectiveness of voice communication, measured in terms of the intelligibility of received speech, and the amplitudeand frequency-selective characteristics of amplitude-modulation receivers. The results lead to the following conclusions: (1) Amplitude limiters are ineffective against fluctuation noise. Against impulse noise, however, they provide marked improvement in performance if they are incorporated in receivers with appropriate selectivity characteristics. (2) When no limiter is used, best performance in the presence either of fluctuation noise or of impulse noise is provided by narrow-band circuits, but the advantage of narrow-band circuits over wide-band circuits is small. (3) When a limiter is used, best performance against fluctuation noise is again provided by narrow-band circuits, and again the advantage of narrow-band circuits over broad-band circuits is small. For optimal reception in the presence of impulse noise, however, the selectivity curve of the circuits preceding the limiter must have gradually sloping skirts. When a limiter is used, therefore, advantage rests with broad-band rather than with narrow-band circuits.

Frequency Modulation Noise Characteristics

Theory and experimental data are given which show the improvements in signal-noise ratio effected by modulation over amplitude modulation. It is shown that above a certain carrier-noise ratio in the modulation receiver which is called the the modulation signal-noise ratio is greater than the amplitude modulation signal-noise ratio by a factor equal to the product of a constant and the deviation ratio (the deviation ratio is equal to the ratio between the maximum deviation and the audio modulation band width). The constant depends upon the type of noise, being slightly greater for impulse than for fluctuation noise. In modulation systems with high deviation ratios, a higher carrier level is required to reach the improvement threshold than is required in systems with low deviation ratios; this carrier level is higher for impulse than for fluctuation noise. At carrier-noise ratios below the improvement threshold, the peak signal-noise ratio characteristics of the modulation receiver are approximately the same as those of the amplitude modulation receiver, but the energy content of the modulation noise is reduced. An effect which is called frequency limiting is pointed out in which the peak value of the noise is limited to a value not greater than the peak value of the signal. With impulse noise this phenomenon effects a noise suppression in a manner similar to that in the recent circuits for reducing impulse noise which is stronger than the carrier in amplitude modulation reception.