Pre-detection Technique Research Articles

Pre-Detection Sensing With Multistage Low-Pass Type Negative Group Delay Circuit

This paper reveals a fascinating pre-detection technique of sensor signals by means of counterintuitive negative group delay (NGD) electronic function. The sensor signal pre-detection technique is unconventionally developed thanks to the engineering of low-pass (LP) type NGD circuit. The NGD pre-detection basic principle is introduced. After topological description, the LP-NGD cell design method in function of negative time delay specification is formulated. An innovative analysis of time-advance property related to multi-stage LP-NGD cell is elaborated. To demonstrate the LP-NGD pre-detection technique feasibility, a proof of concept (POC) is designed with fabricated 3-stage LP-NGD printed circuit board (PCB) prototype integrating 4 LED detectors. The NGD pre-detection experimental setup is described. Extraordinary pre-detection with −0.5 s negative time propagation visible with LED on-lightning is demonstrated by considering a sinc pulse input signal. The developed NGD pre-detection technique can be useful in the future for the anticipation of industrial equipment damages and failure pre-detection sensor system in real-time.

Hybrid Predetection Technique for Efficient Tag Identification in Radio-frequency Identification Systems

Hybrid Predetection Technique for Efficient Tag Identification in Radio-frequency Identification Systems

A Highly Efficient Predetection-Based Anticollision Mechanism for Radio-Frequency Identification

One of the research areas in radio-frequency identification (RFID) systems is the reduction of the identification processing time for a number of tags within an RFID reader recognition region. In the last decade, many research results regarding anticollision algorithms have been presented in the literature. Most of them are tree-based protocols. However, it is important for tree-based protocols to enhance stability and system throughput, since they may face long identification delays when the network density is high. In this study, we present a highly efficient predetection tree-based algorithm to achieve more efficient tag identification performance. Our proposed mechanism can effectively reduce both collisions and idle cycles by exploiting the predetection technique and adjustable slot size mechanism. The simulation results show that the proposed mechanism can effectively improve tag identification time performance by around 29.9% to 64.8% over previous techniques. Further, the number of query cycles, number of collisions, and total number of slots are reduced compared to previous predetection-based protocols. It is also observed that the proposed scheme can have good performance in large-scale RFID systems.

SDR Lattice-Reduction-Aided Detector

Communication techniques based on multiple-input multiple-output (MIMO) have been heavily exploited in the past decade, in order to obtain high capacity communication systems, aim to dealing with increasing spectrum scarcity scenarios. In this context, the semidefinite relaxation (SDR) signal detection strategy is promising due to its very near-optimal maximum-likelihood (ML) performance combined with polynomial complexity. However, the SDR detector has proved insufficient for systems with high order modulation, exactly where the recent pre-detection technique by lattice reduction (LR) has demonstrated excellent results in terms of performance-complexity. This paper investigates the performance-complexity tradeoff of the SDR detector under high order modulation in uncorrelated MIMO channels aided by lattice reduction technique applied in the pre-detection stage.

Signal-to-noise comparison of deconvolution from wave-front sensing with traditional linear and speckle image reconstruction

It is well known that atmospheric turbulence severely degrades the performance of ground-based imaging systems. Techniques to overcome the effects of the atmosphere have been developing at a rapid pace over the past 10 years. These techniques can be grouped into two broad categories: predetection and postdetection techniques. A recent newcomer to the postdetection scene is deconvolution from wave-front sensing (DWFS). DWFS is a postdetection image-reconstruction technique that makes use of one feature of predetection techniques. A wave-front sensor (WFS) is used to record the wave-front phase distortion in the pupil of the telescope for each short-exposure image. The additional information provided by the WFS is used to estimate the system's point-spread function (PSF). The PSF is then used in conjunction with the ensemble of short-exposure images to obtain an estimate of the object intensity distribution through deconvolution. With the addition of DWFS to the suite of possible postdetection image-reconstruction techniques, it is natural to ask "How does DWFS compare with both traditional linear and speckle image-reconstruction techniques?" In the results we make a direct comparison based on a frequency-domain signal-to-noise-ratio performance metric. This metric is applied to each technique's image-reconstruction estimator. We find that DWFS nearly always results in improved performance over the estimators of traditional linear image reconstruction such as Wiener filtering. On the other hand, DWFS does not always outperform speckle-imaging techniques, and in cases that it does the improvement is small.

Gain-insensitive technique for predetection flutter noise cancellation in FM tape recorders

A predetection technique for cancelling flutter noise in FM multichannel magnetic analog tape recorders is described. Cancellation of all correlated flutter noise components is done automatically in the phase-frequency domain so the technique is insensitive to amplitude variations and does not depend on any gain adjustments in the system.

Evaluation of IF and Baseband Diversity Combining Receivers

Techniques of diversity reception have advanced rapidly with the advent of over-the-horizon communication. Because of the rapidly fluctuating signals encountered in tropospheric scatter propagation, strong-signal selection (switching diversity) has been largely supplanted by more sophisticated signal-combining techniques. Present tropospheric scatter systems commonly employ either postdetection ratio-squared combining, or more recently, a technique of predetection linear addition. A theoretical and experimental study comparing these two methods is the subject of this paper. Apart from obvious advantages of simplicity, the predetection technique exhibits lower distortion under multipath conditions, due to the linear combining process.