Showing papers on "Linear phase published in 2006"

A New Single-Phase PLL Structure Based on Second Order Generalized Integrator

Abstract: Phase, amplitude and frequency of the utility voltage are critical information for the operation of the grid-connected inverter systems. In such applications, an accurate and fast detection of the phase angle, amplotude and frequency of the utility voltage is essential to assure the correct generation of the reference signals and to cope with the new upcoming standards. This paper presents a new phase-locked-loop (PLL) method for single-phase systems. The novelty consists in generating the orthogonal voltage system using a structure based on second order generalized integrator (SOGI). The proposed structure has the following advantages: — it has a simple implementation; — the generated orthogonal system is filtered without delay by the same structure due to its resonance at the fundamental frequency, — the proposed structure is not affected by the frequency changes. The solutions for the discrete implementation of the new proposed structure are also presented. Experimental results validate the effectiveness of the proposed method.

Frequency diverse array radars

Abstract: This paper presents a generalized structure for a frequency diverse array radar. In its simplest form, the frequency diverse array applies a linear phase progression across the aperture. This linear phase progression induces an electronic beam scan, as in a conventional phased array. When an additional linear frequency shift is applied across the elements, a new term is generated which results in a scan angle that varies with range in the far-field. This provides more flexible beam scan options, as well as providing resistance to point interference such as multipath. More general implementations provide greater degrees of freedom for space-time-frequency-phase-polarization control, permitting novel concepts for simultaneous multi-mission operation, such as performing synthetic aperture radar and ground moving target indication at the same time.

Range-dependent beamforming using element level waveform diversity

Abstract: This paper presents a novel concept for focusing an antenna beam pattern as a function of range. In conventional phased arrays, beam steering is achieved by applying a linear phase progression across the aperture. Without this phase progression, the antenna beam points to broadside. However, a linear phase progression causes the electric field from each element to constructively sum in the far-field in a direction off broadside, resulting in an electronic scan. For a given linear phase progression, this scan remains fixed for all ranges in the far field. This paper shows that by applying an additional linear frequency shift across the elements, a new term is generated which results in a scan angle that varies with range in the far-field.

Minimax design of adjustable-bandwidth linear-phase FIR filters

Abstract: This paper considers the design of digital linear-phase finite-length impulse response (FIR) filters that have adjustable bandwidth(s) whereas the phase response is fixed. For this purpose, a structure is employed in which the overall transfer function is a weighted linear combination of fixed subfilters and where the weights are directly determined by the bandwidth(s). Minimax design techniques are introduced which generate globally optimal overall filters in the minimax (Chebyshev) sense over a whole set of filter specifications. The paper also introduces a new structure for bandstop and bandpass filters with individually adjustable upper and lower band edges, and with a substantially lower arithmetic complexity compared to structures that make use of two separate adjustable-bandwidth low-pass and high-pass filters in cascade or in parallel. Design examples are included in the paper.

A 16-Channel Low-Power Nonuniform Spaced Filter Bank Core for Digital Hearing Aids

Abstract: We describe a 16-channel critical-like spaced, high stopband attenuation (ges60 dB, 109thtimes16-order), micropower (247.5 muW@1.1 V, 0.96 MHz), small integrated circuit (IC) area (1.62 mm2@0.35-mum CMOS) finite impulse response filter bank core for power-critical hearing aids. We achieve the low-power and small IC area attributes by our proposed common pre-computational unit to generate a set of pre-calculated intermediate values that is shared by all 16 channels. We also take advantage of the consecutive zeros in the coefficients of the filter channels, allowing the multiplexers therein to be simplified. We show that our design is very competitive compared to reported designs, and with the advantages of higher stopband attenuation and linear phase frequency response. Compared to a design using the usual approach, our design features 47% lower power dissipation and 37% smaller IC area

A 25Gb/s CDR in 90nm CMOS for High-Density Interconnects

Abstract: A CDR for source-synchronous high-density link applications receives 25Gb/s at a BER of <10-12. The CDR is a first-order bang-bang topology employing a phase interpolator, linear half-rate phase detector, an analog filter followed by a limiter and a digital loop filter. The core CDR circuit occupies 0.09mm2 and consumes 98mW from a 1.1V supply

A DC to 10-GHz 6-b RF MEMS time delay circuit

Abstract: A 6-b radio frequency (RF) microelectromechanical system (MEMS) time-delay circuit operating from dc to 10 GHz with 39375-ps total time delay is presented The circuit is fabricated on 250-/spl mu/m-thick alumina and uses metal contacting RF MEMS switches to realize series-shunt SP4T switching networks The circuit demonstrates 18+/-06 dB of loss at 10 GHz and has linear phase response across the entire band with accuracy of better than a least significant bit for most states

Detecting secondary arc extinction time by analyzing low frequency components of faulted phase voltage or sound phase current waveforms

Abstract: This paper suggests a new adaptive single-pole auto-reclosing technique based on tracking a single harmonic distortion index (HDI) that represents the behavior of the low frequency components of the faulted phase voltage or sound phase current waveforms and a decision-making index that is defined based on properties of the tracked HDI. The advantage of this technique is that the threshold values, set for indices, can be chosen almost independent of pre-fault loading conditions and line parameters.

Automatic non-linear phase response calibration and compensation for a power measurement device

Abstract: Phase delay compensation sweep may be used in determining correct phase delay compensation of measured currents for substantially matching a measured apparent power to an expected apparent power over an operating range of current values of a current transformer (CT). A frequency sweep may also be used in determining correct phase delay compensation of each measured current in applications having multiple frequencies. Phase delay compensation for each CT current value may be stored in a phase delay compensation look-up table during the phase delay compensation sweep calibration and recalled from the look-up table during operational power measurements. Phase delay compensation for each CT current value and each frequency of that current value may be stored in a phase delay compensation look-up table during the phase delay compensation sweep calibration and recalled from the look-up table during operational power measurements.

Analytical Behavior Law for a Constant Pitch Conical Compression Spring

Abstract: Cylindrical compression spring behavior has been described in the literature using an efficient analytical model. Conical compression spring behavior has a linear phase but can also have a nonlinear phase. The rate of the linear phase can easily be calculated but no analytical model exists to describe the nonlinear phase precisely. This nonlinear phase can only be determined by a discretizing algorithm. The present paper presents analytical continuous expressions of length as a function of load and load as a function of length for a constant pitch conical compression spring in the nonlinear phase. Whal's basic cylindrical compression assumptions are adopted for these new models (Wahl, A. M., 1963, Mechanical Springs, Mc Craw-Hill, New York). The method leading to the analytical expression involves separating free and solid/ ground coils, and integrating elementary deflections along the whole spring. The inverse process to obtain the spring load from its length is assimilated to solve a fourth order polynomial. Two analytical models are obtained. One to determine the length versus load curve and the other for the load versus length curve. Validation of the new conical spring models in comparison with experimental data is performed. The behavior law of a conical compression spring can now be analytically determined. This kind of formula is useful for designers who seek to avoid using tedious algorithms. Analytical models can mainly be useful in developing interactive assistance tools for conical spring design, especially where optimization methods are used.

An active interferometer-stabilization scheme with linear phase control

Abstract: We report a simple and robust computer-based active interferometer stabilization scheme which does not require modulation of the interfering beams and relies on an error signal which is linearly related to the optical path difference. In this setup, a non-collinearly propagating reference laser beam stabilizes the interference output of the laser light propagating collinearly through the interferometer. This stabilization scheme enables adjustable phase control with 20 ms switching times in the range from 0.02pi radians to 6pi radians at 632.8 nm.

Systems and method for automatic quadrature phase imbalance compensation using a delay locked loop

Abstract: An automatic quadrature phase compensation system comprises an on-chip analog phase sense circuit capable of detecting small differences in quadrature phase error and providing a corresponding DC voltage, a voltage-controlled or programmable phase delay circuit to implement quadrature phase error correction, and a feedback system or compensation engine used to process the sensed error voltage and apply a corresponding correction signal to the adjustable phase delay.

Zero Phase Filtering for Active Compensation of Periodic Physiological Motion

Abstract: Periodic physiological motions have been a source of disturbance to many medical interventions and diagnostics that require high precision. This paper presents a new method that performs zero phase filtering to extract a periodic signal within a predetermined frequency band. The basic concept of the proposed adaptive zero phase bandpass filter is to design a pair of cascaded lowpass and highpass IIR filters, such that the phase lag caused by the lowpass filter is balanced by the phase lead introduced by the highpass filter. Since phase angle of a IIR filter is frequency dependent, we adopt the weighted-frequency Fourier linear combiner (WFLC) algorithm as an adaptive frequency estimator to provide the instantaneous dominant frequency of the signal of interest to the system to adjust the filter coefficients to yield the required performance. The proposed filter is implemented in an experiment to perform active stabilization of video images captured by a camcorder subjected to an oscillatory disturbance with varying frequency

All digital phase locked loop architecture for low power cellular applications

Abstract: A novel mechanism that is operative to observe and compare the differentiated phase of the reference and variable PLL loop signals using a frequency detector. The resultant phase differentiated error is then accumulated to yield the phase error. The operation of the loop with the frequency detector is mathematically equivalent to that of the phase detector. A frequency error accumulator is used to generate the integral of the frequency error. The frequency error accumulator also enables stopping the accumulation of the frequency upon detection of a sufficiently large perturbation, effectively freezing the operation of the loop as subsequent frequency error updates are not accumulated. Upon removal of the phase freeze event, accumulation of the frequency error and consequently normal loop operation resumes.

Minimum-phase calibration of sampling oscilloscopes

Abstract: We describe an algorithm for determining the minimum phase of a linear time-invariant response function from its magnitude. The procedure is based on Kramers-Kronig relations in combination with auxiliary direct measurements of the desired phase response. We demonstrate that truncation of the Hilbert transform gives rise to large errors in estimated phase, but that these errors may be approximated using a small number of basis functions. As an example, we obtain a minimum-phase calibration of a sampling oscilloscope in the frequency domain. This result rests on data obtained by an electrooptic sampling (EOS) technique in combination with a swept-sine calibration procedure. The EOS technique yields magnitude and phase information over a broad bandwidth, yet has degraded uncertainty estimates from dc to approximately 1 GHz. The swept-sine procedure returns only the magnitude of the oscilloscope response function, yet may be performed on a fine frequency grid from about 1 MHz to several gigahertz. The resulting minimum-phase calibration spans frequencies from dc to 110 GHz, and is traceable to fundamental units. The validity of the minimum-phase character of the oscilloscope response function at frequencies common to both measurements is determined as part of our analysis. A full uncertainty analysis is provided

Design of linear-phase recombination nonuniform filter banks

Abstract: This correspondence proposes a novel method for designing a class of recombination nonuniform filter banks (RNFBs) with the linear-phase (LP) property. In the structure of the proposed nonuniform filter bank (FB), certain channels of an M-channel uniform FB are merged by synthesis filters of transmultiplexers (TMUXs), yielding nonuniform subbands. By a detailed analysis of the frequency characteristics of the RNFBs, we derive the existence and matching conditions that are necessary for constructing the proposed RNFBs having good frequency responses. With those conditions being satisfied, the design problem becomes that of a set of LP uniform FBs. By using the Parks-McClellan algorithm, we are able to design the near-perfect-reconstruction LP RNFBs in a very simple and efficient way as demonstrated by two examples

Blind MIMO System Estimation Based on PARAFAC Decomposition of Higher Order Output Tensors

Abstract: We present a novel framework for the identification of a multiple-input multiple-output (MIMO) system driven by white, mutually independent unobservable inputs. Samples of the system frequency response are obtained based on parallel factorization (PARAFAC) of three- or four-way tensors constructed based on, respectively, third- or fourth-order cross spectra of the system outputs. The main difficulties in frequency-domain methods are frequency-dependent permutation and filtering ambiguities. We show that the information available in the higher order spectra allows for the ambiguities to be resolved up to a constant scaling and permutation ambiguities and a linear phase ambiguity. Important features of the proposed approach are that it does not require channel length information, needs no phase unwrapping, and unlike the majority of existing methods, needs no prewhitening of the system outputs

Linear phase frequency detector and charge pump for phase-locked loop

Abstract: Techniques for achieving linear operation for a phase frequency detector and a charge pump in a phase-locked loop (PLL) are described. The phase frequency detector receives a reference signal and a clock signal, generates first and second signals based on the reference and clock signals, and resets the first and second signals based on only the first signal. The first and second signals may be up and down signals, respectively, or may be down and up signals, respectively. The phase frequency detector may delay the first signal by a predetermined amount, generate a reset signal based on the delayed first signal and the second signal, and reset the first and second signals with the reset signal. The charge pump receives the first and second signals and generates an output signal indicative of phase error between the reference and clock signals.

Phase synchronization in tilted deterministic ratchets

Abstract: We study phase synchronization for a ratchet system. We consider the deterministic dynamics of a particle in a tilted ratchet potential with an external periodic forcing, in the overdamped case. The ratchet potential has to be tilted in order to obtain a rotator or self-sustained nonlinear oscillator in the absence of external periodic forcing. This oscillator has an intrinsic frequency that can be entrained with the frequency of the external driving. We introduced a linear phase through a set of discrete time events and the associated average frequency, and show that this frequency can be synchronized with the frequency of the external driving. In this way, we can properly characterize the phenomenon of synchronization through Arnold tongues, which represent regions of synchronization in parameter space, and discuss their implications for transport in ratchets.

Phase-Compensated Time-Varying Butterworth Filters

Abstract: One of the important problems of signal processing is to design the filters which possess linear phase characteristics. This paper presents the concept of time-varying Butterworth filters with linear phase. The compensation of the phase characteristics is carried out with the aid of phase shifter which is cascade-connected to the structure of the original Butterworth filter given by the transfer function. The parameters of the phase shifter were calculated in this way that the group delay of the designed filter is possible constant in the filter pass---band. Time varying coefficients were introduced to the phase---compensated filter structure for the purpose of minimization of the filter transient state. This paper contains simulation results of proposed filters and comparison with classic circuits.

Efficient Algorithm for Solving Semi-Infinite Programming Problems and Their Applications to Nonuniform Filter Bank Designs

Abstract: An efficient algorithm for solving semi-infinite programming problems is proposed in this paper. The index set is constructed by adding only one of the most violated points in a refined set of grid points. By applying this algorithm for solving the optimum nonuniform symmetric/antisymmetric linear phase finite-impulse-response (FIR) filter bank design problems, the time required to obtain a globally optimal solution is much reduced compared with that of the previous proposed algorithm

Novel attenuation-counter-propagating phase modulator for highly linear fiber-optic links

Abstract: A key to the development of a high-dynamic-range phase-modulation fiber-optic link is a novel integrated photonic-phase-locked-loop (PPLL) linear phase demodulator, which consists of an inloop phase modulator and feedback control. At present, the propagation delay of the inloop phase modulator is the principal bottleneck in the implementation of this device. This paper specifically concerns a novel attenuation-counter-propagating (ACP) phase modulator (PM) that is free of propagation delay and therefore provides the solution. A rigorous theoretical model and an experimental verification of the ACP phase modulator were provided

DC motor phase estimation with phase-locked loop

Abstract: A DC motor phase estimation algorithm that estimates a speed-related harmonic frequency of a DC motor current under dynamic load conditions having known geometry parameters. The algorithm estimates the phase and magnitude of a complex coefficient in a complex single frequency adaptive filter that receives a primary signal from the motor current and estimates a reference signal using an incident frequency by adapting the complex coefficient to match the magnitude and phase of the speed-related harmonic component of the primary signal. The rate of change of the phase of the complex coefficient is determined by a phase-lock loop coupled to the adaptive filter to adapt a dynamic incident frequency corresponding to a single frequency component of interest in the primary signal. The incident frequency is extracted, and the motor speed is estimated using the extracted incident frequency and the known motor geometry parameters.

Two Classes of Frequency-Response Masking Linear-Phase FIR Filters for Interpolation and Decimation

Abstract: This paper introduces two classes of frequency-response masking (FRM) linear-phase finite (length) impulse response (FIR) filters for interpolation and decimation by arbitrary integer factors M. As they are based on the FRM approach, the proposed filters are low-complexity (efficient) sharp-transition linear-phase FIR interpolation and decimation filters. Compared to previously existing FRM linear-phase FIR filter classes for interpolation and decimation, the new ones offer lower complexity and more freedom in selecting the locations of the passband and stopband edges. Furthermore, the proposed classes of FRM filters can, as special cases, realize efficient Mth-band FRM linear-phase FIR interpolation and decimation filters for all values of M. Previously, only half-band (M = 2) FRM linear-phase FIR filters have appeared in the literature. The paper includes design techniques suitable for the new filters and design examples illustrating their efficiency.

The polyphase-with-advance representation and linear phase lifting factorizations

Abstract: A matrix theory is developed for the noncausal polyphase representation that underlies the theory of lifted filter banks and wavelet transforms. The theory presented here develops an extensive matrix algebra framework for analyzing and implementing linear phase two-channel filter banks via lifting cascade schemes. Whole-sample symmetric and half-sample symmetric linear phase filter banks are characterized completely in terms of the polyphase-with-advance representation, and new proofs are given of linear phase lifting factorization theorems for these two principal classes of linear phase filter banks. The theory benefits significantly from a number of group-theoretic structures arising in the polyphase-with-advance representation and in the lifting factorization of linear phase filter banks. These results form the foundations of the lifting methodology employed in Part 2 of the ISO/IEC JPEG 2000 still image coding standard.

An efficient implementation of linear-phase FIR filters for a rational sampling rate conversion

Abstract: This paper considers how to efficiently implement linear-phase FIR filters for providing a sampling rate conversion by an arbitrary rational factor of M/L, where L(M) is the up-sampling (down-sampling) factor to be implemented before (after) the actual filter. In the proposed implementation, the coefficient symmetry of the linear-phase FIR filter is exploited as well as possible when taking into account the following facts. When increasing (decreasing) the sampling rate by the factor of L(M), only every Lth input sample has a nonzero value (only every Mth output sample has to be evaluated). The proposed implementation is, first, presented by two illustrative examples and, then, guidelines are given on how to efficiently implement a sampling rate converter having an arbitrary rational sampling rate factor M/L.

A new common subexpression elimination algorithm for implementing low complexity FIR filters in software defined radio receivers

Abstract: The complexity of linear phase finite impulse response (FIR) filters used in the channelizer of a software defined radio (SDR) receiver is dominated by the complexity of coefficient multipliers. It is well known that common subexpression elimination (CSE) methods based on canonical signed digit (CSD) coefficients produce low complexity FIR filter coefficient multipliers. A new CSE algorithm based on the binary representation of filter coefficients is presented in the paper. Design examples of channel filters employed in the digital advanced mobile phone systems (D-AMPS) and personal digital cellular (PDC) receivers show that the proposed method offers an average adder reduction of 23% over the conventional CSD-based CSE method.

Delay time adjusting method of delaying a phase of an output signal until a phase difference between an input signal and the output signal becomes an integral number of periods other than zero

Abstract: A delay time adjusting method adjusts a delay time of an input signal so that a phase of the input signal and a phase of an output signal match each other. The delay time adjusting method comprises the step of delaying the phase of the output signal until a phase difference between the phase of the input signal and the phase of the output signal becomes N periods, where N is an integer other than zero.

A 12.5-Gb/s Parallel Phase Detection Clock and Data Recovery Circuit in 0.13- $muhbox m$ CMOS

Abstract: A clock and data recovery (CDR) architecture featuring a parallel phase detector is proposed for speeding up linear-type CDRs. A cause of speed limit in conventional CDRs is very short UP pulses in its phase detector circuit. The parallel phase detector expands UP pulsewidth by adding fixed-width using a half-rate clock. The parallel phase detector is used in the CDR with a couple of unbalanced charge-pump. The bandwidth of decision latches of the PD is extended by 1.7 times by using both shunt-peaking and capacitance coupling. The monolithic CDR implemented in 0.13-mum CMOS shows 1.7 times wider phase linear response region of 0.56UI than that of a conventional CDR. It operates at 12.5-Gb/s with PRBS 231-1 input data. Measurements show large jitter tolerance of over 0.5 UIpp for 4-8 MHz jitter frequency as well as jitter transfer characteristics independent on input-jitter amplitudes of 0.1, 0.3, and 0.5 UIpp