Search results for "Demodulation"
showing 10 items of 18 documents
Homodyne Solid-State Biased Coherent Detection of Ultra-Broadband Terahertz Pulses with Static Electric Fields.
2021
We present an innovative implementation of the solid-state-biased coherent detection (SSBCD) technique, which we have recently introduced for the reconstruction of both amplitude and phase of ultra-broadband terahertz pulses. In our previous works, the SSBCD method has been operated via a heterodyne scheme, which involves demanding square-wave voltage amplifiers, phase-locked to the THz pulse train, as well as an electronic circuit for the demodulation of the readout signal. Here, we demonstrate that the SSBCD technique can be operated via a very simple homodyne scheme, exploiting plain static bias voltages. We show that the homodyne SSBCD signal turns into a bipolar transient when the stat…
Performance analysis of binary DPSK modulation schemes over Hoyt fading channels
2009
This paper presents a performance analysis of differential phase shift keying (DPSK) modulation schemes over Hoyt fading channels. Based upon the theory of DPSK modulation and a recently derived formula for the probability density function (PDF) of the differential phase between two Hoyt vectors contaminated by additive white Gaussian noise (AWGN), the bit error probability (BEP) for DPSK systems with noncoherent demodulation over Hoyt channels is analyzed. In the analysis, the correlation between adjacent bits is taken into account. The obtained theoretical results are fully validated first by reducing them to the corresponding known solutions for the Rayleigh fading distribution being a s…
FLUMO: FLexible Underwater MOdem
2019
The last years have seen a growing interest in underwater acoustic communications because of its applications in marine research, oceanography, marine commercial operations, the offshore oil industry and defense. High-speed communication in the underwater acoustic channel has been challenging because of limited bandwidth, extended multipath, refractive properties of the medium, severe fading, rapid time variation and large Doppler shifts. In this paper, we show an implementation of a flexible Software-Defined Acoustic (SDA) underwater modem, where modulation parameters are completely tunable to optimize performance. In particular, we develop the system architecture following two key ideas. …
Fast fringe pattern phase demodulation using FIR Hilbert transformers
2016
This paper suggests the use of FIR Hilbert transformers to extract the phase of fringe patterns. This method is computationally faster than any known spatial method that produces wrapped phase maps. Also, the algorithm does not require any parameters to be adjusted which are dependent upon the specific fringe pattern that is being processed, or upon the particular setup of the optical fringe projection system that is being used. It is therefore particularly suitable for full algorithmic automation. The accuracy and validity of the suggested method has been tested using both computer-generated and real fringe patterns. This novel algorithm has been proposed for its advantages in terms of com…
Learning From Errors: Detecting Cross-Technology Interference in WiFi Networks
2018
In this paper, we show that inter-technology interference can be recognized using commodity WiFi devices by monitoring the statistics of receiver errors. Indeed, while for WiFi standard frames the error probability varies during the frame reception in different frame fields (PHY, MAC headers, and payloads) protected with heterogeneous coding, errors may appear randomly at any point during the time the demodulator is trying to receive an exogenous interfering signal. We thus detect and identify cross-technology interference on off-the-shelf WiFi cards by monitoring the sequence of receiver errors (bad PLCP, bad FCS, invalid headers, etc.) and propose two methods to recognize the source of in…
Tutorial on dynamic analysis of the Costas loop
2016
Abstract Costas loop is a classical phase-locked loop (PLL) based circuit for carrier recovery and signal demodulation. The PLL is an automatic control system that adjusts the phase of a local signal to match the phase of the input reference signal. This tutorial is devoted to the dynamic analysis of the Costas loop. In particular the acquisition process is analyzed. Acquisition is most conveniently described by a number of frequency and time parameters such as lock-in range, lock-in time, pull-in range, pull-in time, and hold-in range. While for the classical PLL equations all these parameters have been derived (many of them are approximations, some even crude approximations), this has not…
Performance evaluation of sum-of-cisoids Rice/Rayleigh fading channel simulators with respect to the bit error probability
2014
Sum-of-cisoids (SOC) processes provide an important framework for the modeling and simulation of multipath fading channels. In this paper, we analyze the performance of SOC Rice/Rayleigh narrowband fading channel simulators with respect to the bit error probability (BEP) of quadrature phase shift keying (QPSK) and differential phase shift keying (DPSK) systems with both coherent and noncoherent demodulation. For the BEP of coherent QPSK and DPSK, exact analytical expressions are derived, which provide insight into the influence of the number of propagation paths and the path gains on the system performance. It will be shown that at least 10 multipath components are required to guarantee tha…
Implications of the Semigeostrophic Nature of Rossby Waves for Rossby Wave Packet Detection
2015
Abstract Upper-tropospheric Rossby wave packets have received increased attention recently. In most previous studies wave packets have been detected by computing the envelope of the meridional wind field using either complex demodulation or a Hilbert transform. The latter requires fewer choices to be made and appears, therefore, preferable. However, the Hilbert transform is fraught with a significant problem, namely, a tendency that fragments a single wave packet into several parts. The problem arises because Rossby wave packets show substantial deviations from the almost-plane wave paradigm, a feature that is well represented by semigeostrophic dynamics. As a consequence, higher harmonics …
A Novel Method of Distance Measurement Based on Pulse Position Modulation and Synchronization of Chaotic Signals Using Ultrasonic Radar Systems
2009
This paper deals with a novel method of transmission and receipt of a signal based on both the property of two chaotic systems generating the same chaotic signal when they are synchronized and the property of pulse position modulation (PPM) to be insensitive to the distortions of the transmission channel. The method is discussed in the context of ultrasonic radar systems, in which the transmitter and receiver, which consist of ultrasonic sensors, are near each other, and the received signal consists of the transmitted signal reflected by an obstacle. A reference sinusoidal signal is superimposed to a chaotic signal generated by a master chaotic system, and the whole signal is modulated acco…
A method to estimate the path gains and propagation delays of underwater acoustic channels using the arrival phase information of the multipath compo…
2017
Abstract We propose a method for the estimation of the channel parameters of underwater acoustic channels (UACs) by using a pseudo-noise (PN) sequence. For the channel sounding, the PN sequence is coherently modulated on a carrier frequency by using a binary phase-shift keying (BPSK) modulation scheme. For the demodulation, the arrival phases of the received BPSK signals must be known at the receiver. In practice, however, the arrival phases of the received signal are unknown. We propose to demodulate the received BPSK signal by using an hypothetical arrival phase, which will be increased from 0 to 2 π . The demodulated signal obtained by using the hypothetical arrival phase is then correla…