Phase Ambiguity Problem Research Articles

A Phenomenological Study of Violation of CP and CPT Symmetries in the Neutral Kaon System

A phenomenological study is given of the (possible) violation of CP and CPT symmetries in the A'- K system. Special attention is paid to the problem of phase ambiguity and phase convention. Mixing parameters and decay amplitudes are parametrized in a rephasing invariant way, and the well-known parameters 7'/+- and 7'/oo describing 2Jr modes as well as various leptonic asymmetries are expressed in terms of these parameters. The parameters E and L1 characterizing mixing between IK> and IK 0 ) are treated with as little theoretical prejudice as possible.

Transparency of Error Correcting Codes

Coherent demodulation of BPSK/QPSK signals gives rise to phase ambiguity problem. Differential encoding and decoding is one method to overcome this. Use of error correcting codes with this arrangement demands transparency of the code. Present paper discusses some aspects of the technique using systematic block code's structure. Phase rotation invariance in combined modulation and coding is also discussed briefly.

High-speed noncontact profiler based on scanning white-light interferometry

We describe a system for fast three-dimensional profilometry, of both optically smooth and optically rough surfaces, based on scanning white-light techniques. The system utilizes an efficient algorithm to extract and save only the region of interference, substantially reducing both the acquisition and the analysis times. Rough and discontinuous surfaces can be profiled without the phase-ambiguity problems associated with conventional phase-shifting techniques. The system measures steps to 100 µm, scans a 10µLm range in 5 s, and has a smooth surface repeatability of 0.5 nm.

A matched-mode processing technique for localizing a transient source in the time domain

A matched-mode processing method separates the range and depth estimation tasks, thereby obtaining a sequential procedure that circumvents the need for a two-dimensional search over all hypothesized source locations. Therefore, when applicable, it is more efficient than a matched-field method. Here, the conventional frequency-domain, matched-mode method is extended to deal with more realistic nonharmonic, narrow-band signals directly in the time domain. The modes are separated by the conventional modal filtering approach. Then, the source range and depth information can be estimated by the relative arrival times and energies of a relatively well-behaved subset of the modal arrivals. In this way, the problem of modal phase ambiguity is removed, and the entire frequency content of the modal arrivals is coherently combined by operating directly on the time waveforms. Moreover, this approach does not require a prior knowledge of the source waveform. In the numerical simulation, the source and receiver arrangement and the ocean parameters are taken from an experimental setup in the Mediterranean Sea [S. M. Jesus, J. Acoust. Soc. Am. 90, 2034–2041 (1991)].

Instantaneous GPS attitude determination

A procedure for instantaneous GPS (Global Positioning Satellite) attitude determination, i.e., a solution for the GPS integrated carrier Doppler wavelength ambiguities using only measurements at a single epoch, is described. Most previous techniques to solve the phase ambiguity problem have required some form of time history processing relying on GPS satellite and/or user motion to provide enough geometry change to eliminate false solutions. The algorithm described assumes three noncollinear antennas and integrated carrier Doppler measurements from four or more satellites. Double-difference processing provides at least three independent observables for the two antenna separation vectors to compute the three attitude Euler angles.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Phase ambiguity resolution in trellis-coded modulations

A rotation detection algorithm for solving the phase ambiguity problem in trellis-coded modulations is proposed. This algorithm is simple to implement and may be an efficient alternative to rotationally invariant codes. Its performance has been investigated by simulation and appears promising. >

Modal analysis for randomly excited structural systems with unmeasured input

A new time series approach for the estimation of modal parameters of randomly excited structures is presented in this paper. Since previous methods in time series analysis techniques suffer from the phase ambiguity problem, the new method is proposed to circumvent this difficulty. It relies on the development of a vector first-order autoregressive model VAR (1) of the vibrating structure at the points of measurement and, in particular, on the utilization of velocity information to set up the cross-covariance matrix in the estimation procedures. The theoretical basis of the procedure is presented along with simulation results.

Resolution of phase ambiguity in macromolecular crystallography

The chapter presents a procedure that is applicable to single isomorphous replacement (SIR) data without anomalous scattering information as well as to pure single-wavelength anomalous scattering (SAS) data alone, and it does not require the presence of noncrystallographic symmetry. Test results shows that it is very effective; not only can it remove the phase ambiguity but it will also refine the phases at the same time. In actual application to SIR data, the method has even produced results that appear to be superior to those obtained from the multiple isomorphous replacement method. One of the situations in which the phase ambiguity problem occurs is when the isomorphous replacement method is applied to a noncentrosymmetric structure using only one isomorphous data set. The method demonstrates a remarkable effectiveness for overcoming the phase ambiguity problem that has the major obstacle in the use of SIR or SAS data alone for macromolecular studies. The computer programs used in the studies has been assembled into a program package.

New possibilities for phaseless microwave diagnostics. Part2: The uniqueness problem and half plane imaging

The ambiguity of the phase-retrieval problem has been investigated. Theoretical studies have concentrated on the asymptotic properties of the Fourier-transform integral to investigate the band-limiting function of the aperture in determining the zeros of the transform. For one-dimensional functions, the phase-ambiguity problem is identified as finite permutations of zero conjugation, which, although modifying the existing phase, leave the intensity unperturbed. Based on these studies a new practical algorithm for halfplane imaging is proposed for one-dimensional functions. The relevance of the proposed technique has been discussed, with a theoretical analysis which studies the distribution of transform zeros for two-dimensional functions.

Evaluation of cellular mobile telephone data receivers

Some measurement techniques and results employed to evaluate advanced mobile phone system (AMPS) data receivers being driven by a Rayleigh fading channel are described. These performance measurements were used as a mechanism for comparing the design effectiveness of various bit clock recovery systems. Of five data receiver types evaluated, two models employed a full-wave rectifier in the bit clock recovery system. In this system nominal diode unbalance may cause the derived bit clock to lock 180° from the phase required to properly decode the incoming bit stream. This condition may even occur at high carrier-to-noise ratios when message structures containing long strings of ones or zeros are received. The other data receiver types employed digital signal processing for clock recovery to circumvent this phase ambiguity problem. The performance data of five data receivers are compared to noncoherent frequency-shift keying (FSK) as a model. In most cases, the test results are in good agreement with this model. The performance measurements presented include derived clock jitter and single and average bit error rates as a function of average carrier-to-noise ratios. The implementation of test instrumentation and the interpretation of test results are discussed. The objective is to stress the capability of simulation measurements to evaluate mobile receiver designs in a laboratory environment.

Phase-Ambiguity Resolution in a Four-Phase PSK Communications System

The constraints of digital satellite communications systems have led to the derivation of a method for resolving the problem of recovered-carrier phase ambiguity in a coherent fourphase phase-shift-keying (PSK) communications system while simultaneously providing synchronization information. This method is described for the general case and a general implementation is given. In addition, implementations are given for two particularly simple special cases.