CiteULike: dcastro's loop

Limiter effect on cycle slip performance of synchronization loops

P Hasan — 2008-07-23T23:54:11-00:00

Communications, IEEE Transactions on, Vol. 44, No. 5. (1996), pp. 562-565.

A formula suitable for numerical evaluation is derived for the mean cycle slip time of a first-order loop with state-dependent spectral density of the loop noise. The formula is applied to a synchronizer with sinusoidal type limiter phase detector. The accuracy of the asymptotic expression due to Moeneclaey (1985) is evaluated. Better cycle slip performance of the considered synchronizer compared to that with multiplier phase detector is reported at the loop signal-to-noise ratio (SNR) α>2

Decision-directed coherent delay-lock tracking loop for DS-spread-spectrum signals

R de Gaudenzi — 2008-07-23T23:54:14-00:00

Communications, IEEE Transactions on, Vol. 39, No. 5. (1991), pp. 758-765.

The authors present a nonconventional joint data demodulation-pseudo-noise (PN) code tracking scheme for direct sequence (DS) spread-spectrum (SS) signals which solves problems of component imbalance and sensitivity with hardware simplicity and no performance degradation. An integrate-and-dump Costas loop is used for carrier recovery and data demodulation of the SS signal. Both data and carrier are then used to derive the baseband error signal of the code tracking loop. Moreover, a single passband correlator is used to perform the early-late correlation, leading to a hardware complexity equivalent to that of the tau-dither scheme, but without its loss in performance. Results of a thorough theoretical analysis of the system in an additive Gaussian noise (AWGN) environment are reported. They provide performance curves in terms of steady-state jitter and mean time to first lock loss. A superior jitter performance for low values of <e1>E</e1>b/ <e1>N</e1>0 with respect to a traditional noncoherent delay lock loop (DLL) is shown, along with the potential gain of Manchester coding upon the more usual NRZ format

A noncoherent tracking loop with diversity and multipath interference cancellation for direct-sequence spread-spectrum systems

Wern-Ho Sheen — 2008-06-02T06:46:07-00:00

Communications, IEEE Transactions on, Vol. 46, No. 11. (1998), pp. 1516-1524.

A noncoherent tracking loop with diversity reception and multipath interference cancellation is proposed for direct-sequence spread-spectrum systems on frequency-selective multipath fading channels. The basic idea of the loop is to reproduce the multipath interference and remove it from the received signal, and then a path diversity is embedded in the loop to improve the loop performance. The tracking error performance of the loop is evaluated by linear analyses and computer simulations. Numerical results show that the proposed tracking loop outperforms the traditional delay locked loop and performs very well under all considered fading conditions

Two novel automatic frequency tracking loops

S Anguirre — 2008-05-22T09:27:04-00:00

Aerospace and Electronic Systems, IEEE Transactions on, Vol. 25, No. 5. (1989), pp. 749-760.

Two automatic-frequency-control loops are introduced and analyzed in detail. The algorithms are generalizations of the well-known cross-product automatic-frequency-control loop with improved performance. The first estimator uses running overlapping discrete Fourier transforms (DFTs) to create a discriminator curve proportional to the frequency estimation error, whereas the second one preprocesses the received data and then uses an extended Kalman filter to estimate the input frequency. The algorithms are tested by computer simulations in a low carrier-to-noise-ratio (CNR) and highly dynamic environment. The algorithms are suboptimum tracking schemes with a larger frequency error variance compared to an optimum strategy, but they offer simplicity of mechanization and a CNR with a very low operating threshold

The performance of the all-digital data transition tracking loop using nonlinear analysis

A Mileant — 2008-05-22T08:58:49-00:00

Communications, IEEE Transactions on, Vol. 43, No. 234. (1995), pp. 1202-1215.

This paper describes the performance of the all digital data transition tracking loop (DTTL) with coherent and noncoherent sampling using nonlinear theory. The effects of few samples per symbol and of non-commensurate sampling and symbol rates are addressed and analyzed for perfectly square pulses as well as filtered pulses. Their impact on the probability density and variance of the phase error are quantified through computer simulations. It is shown that the performance of the all-digital DTTL approaches its analog counterpart when the sampling and symbol rates are noncommensurate (i.e., the number of samples per symbol is irrational). The phase error variance for an even number of samples per symbol is also shown to degrade compared to an odd number of samples per symbol

Optimum Performance of Suppressed Carrier Receivers with Costas Loop Tracking

M Simon — 2008-05-21T12:54:41-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 25, No. 2. (1977), pp. 215-227.

The performance of suppressed carrier receivers with Costas loop tracking is optimized by proper choice of loop arm filter bandwidth. In particular, it is shown that for a variety of passive arm filter types, there exists, for a given data rate and data signal-signal-to-noise ratio, an optimum filter bandwidth in the sense of minimizing the loop's squaring loss. For the linear theory case, this is equivalent to minimizing the loop's tracking jitter. When symbol synchronization is known, it is shown that by replacing the passive arm filters with active filters, i.e., integrate-and-dump circuits, one can acheive an improvement in carrier-to-noise ratio of as much as 4 to 6 dB depending on the passive arm filter type used for comparison and the value of data signal-to-noise ratio.

Effects of gain and phase imbalance on sum-difference code tracking loop's performance in spread spectrum systems

Jeich Mar — 2008-05-15T17:46:37-00:00

Universal Personal Communications Record, 1997. Conference Record., 1997 IEEE 6th International Conference on, Vol. 2 (1997), pp. 371-375 vol.2.

The nonlinear renewal process approach (RPA) is applied to analyze the noncoherent sum-difference loop (SDL) with gain and phase imbalance for spread spectrum systems. In the analysis, the code acquisition boundary is equal to the branch offset, 0<δ&les;1. The results indicate that under phase imbalance, when δ&ges;0.5 and with gain balance, the values of the DC bias of the SDL are small and will not change with the loop signal-to-noise ratio (SNR); when δ<0.5 and with a low loop SNR, the DC bias becomes larger which will result in the SDL loss of lock. A larger branch offset may result in a higher mean-time-to-lose-lock (MTLL) for the SDL with gain and phase imbalance; however, the RMS tracking error has not obviously changed with the increasing branch offset. Furthermore, it is shown that in case where the early and late branch of the SDL can not be implemented with equal gain, one can get better performance results by putting the arm with smaller gain in the late branch of the SDL

Modified tracking loop for DS spread spectrum systems

F Nouvel — 2008-05-15T17:46:36-00:00

Electronics Letters, Vol. 29, No. 21. (1993), pp. 1827-1828.

A nonconventional pseudo-noise (PN) code tracking loop for direct sequence (DS) spread spectrum systems is presented. It solves problems of component imbalance while maintaining hardware simplicity

A Modified PN Code Tracking Loop: Its Performance Analysis and Comparative Evaluation

R Yost — 2008-05-15T17:46:35-00:00

Communications, IEEE Transactions on [legacy, pre - 1988], Vol. 30, No. 5. (1982), pp. 1027-1036.

A modified noncoherent PN code tracking loop (MCTL) has been previously presented by the authors [3]. The loop was shown to have the hardware simplicity of the tau-dither loop and a tracking performance superior to the traditional delay-locked code tracking loop (TCTL). Further work conducted herein expands on these previous results by considering the band-limiting effects of the bandpass arm filters on the performance of the MCTL. It will be shown that an even greater improvement in tracking performance is experienced by the MCTL over the TCTL when such effects are included. Furthermore, it was mentioned in [3] that a specific<tex>S/N</tex>existed below which the MCTL acquisition behavior was superior to the TCTL and above which its behavior was inferior. The bandlimiting effects will be shown to have a more deleterious effect on the TCTL and, as such, the crossover<tex>S/N</tex>will increase, thus enhancing the comparable capabilities in favor of the MCTL. This paper also discusses the implementation sensitivities to hardware gain and phase imbalance by expanding on the noise-free work in [3] to include the noisy case.

A new tracking loop for direct sequence spread spectrum systems on frequency-selective fading channels

Wern-Ho Sheen — 2008-05-15T17:35:11-00:00

Communications, IEEE Transactions on, Vol. 43, No. 12. (1995), pp. 3063-3072.

A new tracking loop is proposed for direct-sequence spread-spectrum signaling on a frequency-selective fading channel. By exploiting the inherent multipath diversity of the channel, the new tracking loop overwhelmingly outperforms a traditional noncoherent delay-locked loop (DLL) for all cases under consideration. Linear and nonlinear (based on the renewal process approach) methods are employed to analyze the new tracking loop with perfect channel estimation. Although the analytical methods are developed under the guise of a slowly time-varying channel, the analytical and simulation results show close agreement for channels with a code Doppler shift βD as large as 0.117598 (Doppler shift fD=83 Hz). Consequently, the analytical methods, especially those based on linear methods, can be easily employed to characterize the new tracking loop. The performance degradation caused by imperfect channel estimation is determined by computer simulations. Over a range of signal-to-noise-ratios (SNRs) of practical interest, the simulation results show a degradation of about 2 dB and 1 dB for βD=0.0117598 (fD=8.3 Hz) and βD =0.117598 (fD=83 Hz), respectively

Anti multipath cellular radio location for DS/CDMA systems using a novel EKF subchip RAKE tracking loop

E Fishler — 2008-05-09T15:42:49-00:00

Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE, Vol. 2 (1999), pp. 1328-1332 vol.2.

This paper discusses an improved method for localization in a DS-CDMA based cellular-phone communication link. This method suggests an optimization for code synchronization, which allows for TDOA (time difference of arrival) estimations to be solved for the position of a mobile phone. It is known that the time delay of a received DS signal, derived from the classical DLL, may express severe timing errors due to multipath effects. A new anti multipath multi-tracking extended Kalman filter loop is shown to achieve far better results especially in the environment of specular multipath. Specifically, this new loop minimizes the errors due to multipath components by letting the EKF decide upon the best weights of its sub-chip processing branches, resulting in a RAKE-like tracking loop. This loop tracks not only the line of sight path, but also the other multipath components as well as their power and phase. It is shown that the implementation of this technique converges to the classical non-coherent code tracking DLL structure when no multipath is assumed, but results in a new and efficient tracking loop structure in the more realistic fading channel case. The application of this technique to the EIA IS-95 system is considered, where accurate location estimations as well as power management utilities are treated

The effect on tracking loop performance when using the efficient search method for fast fine frequency acquisition

Young Cho — 2008-02-14T16:24:22-00:00

Control, Automation and Systems, 2007. ICCAS '07. International Conference on (2007), pp. 517-522.

When implementing real-time software based GNSS receiver, the accurate and fast signal acquisition and tracking method is more necessary than the hardware based receiver owing to lots of computation time. Generally, in the software based GNSS receiver, parallel code phase signal acquisition method using FFT has been used. But it has the defect of the limited frequency resolution according to input data’s length. Considering the carrier frequency resolution must be about tens of Hz in order to perform the tracking loop correctly, the fine frequency acquisition method to minimize the computation time should be necessary to overcome this limitation. Also the examination whether the method will enhance the tracking loop’s performance and cause the reduction of computation time should be necessary. To evaluate these necessities, in this paper, the efficient search method for fine frequency acquisition will be suggested and tested. Furthermore, the effect on signal tracking loop, when the result of signal acquisition obtained by the suggested method is applied, will be analyzed.

GPS receiver architectures and measurements

MS Braasch — 2008-02-11T09:58:35-00:00

Proceedings of the IEEE, Vol. 87, No. 1. (1999), pp. 48-64.

Although originally developed for the military, the Global Positioning System (GPS) has proven invaluable for a multitude of civilian applications. Each application demands specific performance from the GPS receiver and the associated requirements often vary widely. This paper describes the architectures and functions of civilian GPS receivers and then focuses on performance considerations. The fundamental receiver measurements are described and the quality of these measurements are related to the aforementioned receiver architectures

Effects of multipath fading on delay-locked loops for spread spectrum systems

Wern-Ho Sheen — 2008-02-09T00:51:58-00:00

Communications, IEEE Transactions on, Vol. 42, No. 234. (1994), pp. 1947-1956.

A renewal process approach is used to analyze noncoherent delay-locked loops (DLLs) for spread spectrum systems operating over frequency selective and frequency nonselective slow fading channels. The effects of multipath fading are evaluated in terms of the mean-time-to-lose-lock (MTLL) and the root-mean-square (RMS) tracking error. For channels that have a specular component, the following results are observed: (i) the effect of multipath fading is more significant for tracking loops that have large loop signal-to-noise ratios (SNRs); (ii) a smaller early-late discriminator offset Δ, which is bounded by 0<Δ<1, results a better tracking error performance. However, the tracking error is insensitive to Δ, if there is a strong multipath fading effect and/or the tracking loops have small loop SNRs; (iii) a larger Δ (>0.5) may result in a higher MTLL, especially if there is a strong multipath effect. From (ii) and (iii), instead of using the popular choice of Δ=0.5, a larger Δ may be chosen for a DLL that works at low SNRs and/or strong multipath fading environments, where MTLL is an important consideration

Numerical simulation of GNSS code tracking loops using Euler-Maruyama method

JL Garrison — 2008-02-03T22:58:07-00:00

Electronics Letters, Vol. 41, No. 15. (2005), pp. 868-869.

The Euler-Maruyama (EM) method for the numerical integration of stochastic differential equations is applied to simulate tracking loops for Global Navigation Satellite System (GNSS) signals. Use of a large step size and two-point pseudorandom numbers allow for computationally efficient simulation of statistics such as the mean time to lose lock (MTLL). To demonstrate this method, non-coherent delay-lock loops are simulated using the EM method. The MTLL computed from an ensemble of 50 sample paths is compared to a numerical integration of the Fokker-Planck equation. The dependence of computational time and error on step size is evaluated.