Reader Receiver Research Articles

A switchable dual‐mode fully‐differential common‐source low‐noise amplifier in 0.18‐μm CMOS technology

AbstractA highly‐integrated switchable dual‐mode low‐noise amplifier (LNA) is proposed and implemented in standard 0.18 μm complementary metal‐oxide‐semiconductor (CMOS) technology for ultra‐high frequency‐radio‐frequency identification (UHF RFID) reader receivers. This dual‐mode LNA can be controlled to operate in two different modes in order to meet the requirements for the listen‐before‐talk mode and the normal mode of the UHF RFID reader receiver, respectively. The fully‐differential common‐source cascode topology with perfect input impedance matching, capacitive cross‐coupling, and common‐mode feedback techniques are employed to improve its performance. Measurement results show that, from a single power supply of 1.8 V, the LNA achieved the power gain (S21) of 9.1 dB, the input power reflection (S11) of −20 dB, the minimum noise figure (NF) of 3.6 dB, and the P1dB of −5 dBm in high‐gain mode. In high‐linearity mode, S21 of 3.2 dB, S11 of −17 dB, NF of 5.2 dB, and P1dB of −1.3 dBm were obtained.

Relationship between Roe and Metz simulation model for multireader diagnostic data and Obuchowski-Rockette model parameters.

For the typical diagnostic radiology study design, each case (ie, patient) undergoes several diagnostic tests (or modalities) and the resulting images are interpreted by several readers. Often, each reader is asked to assign a confidence-of-disease rating to each case for each test, and the diagnostic tests are compared with respect to reader-performance outcomes that are functions of the reader receiver operating characteristic (ROC) curves, such as the area under the ROC curve. These reader-performance outcomes are frequently analyzed using the Obuchowski and Rockette method, which allows conclusions to generalize to both the reader and case populations. The simulation model proposed by Roe and Metz (RM) in 1997 emulates confidence-of-disease data collected from such studies and has been an important tool for empirically evaluating various reader-performance analysis methods. However, because the RM model parameters are expressed in terms of a continuous decision variable rather than in terms of reader-performance outcomes, it has not been possible to evaluate the realism of the RM model. I derive the relationships between the RM and Obuchowski-Rockette model parameters for the empirical area under the ROC curve reader-performance outcome. These relationships make it possible to evaluate the realism of the RM parameter models and to assess the performance of Obuchowski-Rockette parameter estimates. An example illustrates the application of the relationships for assessing the performance of a proposed upper one-sided confidence bound for the Obuchowski-Rockette test-by-reader variance component, which is useful for sample size estimation.

Collision Detection and Signal Recovery for UHF RFID Systems

In this paper, we present a novel high-throughput anti-collision algorithm for passive ultrahigh-frequency (UHF) radio-frequency identification (RFID) systems. Our algorithm utilizes signal recovery techniques of collided tag signals to both recover tag communications and obtain an accurate count of all tags in the field. Passive UHF RFID systems are used for long-range passive communications for applications including supply chain management and electronic tolling. Anti-collision algorithms are used to ensure successful RFID tag communications due to the likelihood of multiple tags being in the field and attempting to communicate simultaneously. The limited on-tag functionality necessitates the use of simple anti-collision algorithms such as a dynamic frame slotted Aloha (DFSA) algorithm. With our novel collision detection and signal recovery anti-collision algorithm, the RFID reader can retrieve multiple valid communications from each collided slot in a DFSA-based anti-collision protocol, while our algorithm allocates an optimal number of slots resulting in more collided but recoverable slots and fewer empty slots. Our algorithm achieves a nearly 100% throughput improvement with an expected throughput of 0.85 compared with an expected throughput of 0.426 for a standard DFSA algorithm. The reader receiver with the proposed algorithm is implemented in a field-programmable gate array and the whole reader system is verified using the communication tests with commercial tags. According to the synthesized results in an SMIC 0.13- $\mu \text{m}$ CMOS technology, the collision detection and signal recovery module consumes about 135k GE. Note to Practitioners —Signal recovery methods are capable of extracting information from collided signals. In this paper, we introduce and analyze a signal recovery method based on the voltage histogram of the received signal. Both the original signals and the number of collided signals are recovered. The information of tags is used by our novel algorithm to increase the system throughput in DFSA-based anti-collision algorithms. The recovered signals allow our algorithm to directly obtain the tag identifier. By determining the number of collided signals, our algorithm is able to calculate an accurate estimate of the total number of tags in the reader’s field. With signal recovery and an accurate tag count, our algorithm is able to reduce the total number of slots needed to identify all tags, thereby increasing the throughput. We present a novel frame length optimization method that increases throughout by shrinking the number of slots, thereby intentionally causing collisions and reducing the total number of empty slots. In addition, we present a hardware implementation of our novel method that is suitable for integration into RFID readers. When the signal strengths of the tags in collision in the in-phase or quadrature path are not close to each other, the performance of our method is much better than that of the traditional method in which the collision signal is treated as ineffective and ignored.

A 10-Mb/s Uplink Utilizing Rectifier Third-Order Intermodulation in a Miniature CMOS Tag

This letter introduces an inductive power transfer (IPT) uplink to a miniature CMOS tag. The transmitter (Tx) sends a two-tone waveform at 5.728/5.768 GHz to charge the tag and excites a third-order intermodulation frequency at 5.808 GHz from the tag rectifier, which is then modulated and returned to the reader receiver (Rx) via the same coupled coils used for the IPT. The Tx/Rx frequency separation, incorporating an appropriate duplexer, allows significant filtering on the Tx-to-Rx leakages. The achieved uplink data rate is 10 Mb/s.

Hepatocellular Carcinoma Screening With Computed Tomography Using the Arterial Enhancement Fraction With Radiologic-Pathologic Correlation.

The aim of this study was to investigate the performance of the arterial enhancement fraction (AEF) in multiphasic computed tomography (CT) acquisitions to detect hepatocellular carcinoma (HCC) in liver transplant recipients in correlation with the pathologic analysis of the corresponding liver explants. Fifty-five transplant recipients were analyzed: 35 patients with 108 histologically proven HCC lesions and 20 patients with end-stage liver disease without HCC. Six radiologists looked at the triphasic CT acquisitions with the AEF maps in a first readout. For the second readout without the AEF maps, 3 radiologists analyzed triphasic CT acquisitions (group 1), whereas the other 3 readers had 4 contrast acquisitions available (group 2). A jackknife free-response reader receiver operating characteristic analysis was used to compare the readout performance of the readers. Receiver operating characteristic analysis was used to determine the optimal cutoff value of the AEF. The figure of merit (θ = 0.6935) for the conventional triphasic readout was significantly inferior compared with the triphasic readout with additional use of the AEF (θ = 0.7478, P < 0.0001) in group 1. There was no significant difference between the fourphasic conventional readout (θ = 0.7569) and the triphasic readout (θ = 0.7615, P = 0.7541) with the AEF in group 2. Without the AEF, HCC lesions were detected with a sensitivity of 30.7% (95% confidence interval [CI], 25.5%-36.4%) and a specificity of 97.1% (96.0%-98.0%) by group 1 looking at 3 CT acquisition phases and with a sensitivity of 42.1% (36.2%-48.1%) and a specificity of 97.5% (96.4%-98.3%) in group 2 looking at 4 CT acquisition phases. Using the AEF maps, both groups looking at the same 3 acquisition phases, the sensitivity was 47.7% (95% CI, 41.9%-53.5%) with a specificity of 97.4% (96.4%-98.3%) in group 1 and 49.8% (95% CI, 43.9%-55.8%)/97.6% (96.6%-98.4%) in group 2. The optimal cutoff for the AEF was 50%. The AEF is a helpful tool to screen for HCC with CT. The use of the AEF maps may significantly improve HCC detection, which allows omitting the fourth CT acquisition phase and thus making a 25% reduction of radiation dose possible.

RFID Reader Receiver Using Blind Signal Estimation for Multiuser Detection

 Abstract—Radio frequency identification (RFID) is a wireless technology that uses radio backscatter signals to purpose of identify objects. Especially, in the microwave frequency as 2.45 GHz is growing rapidly. Since the physical environment surrounding the propagation path of radio identification is generally difficult to control, the channel characteristics in backscattering are often channel fading. There are two major sources of impairment of the RFID reader is unreadable as the tag signal propagate through channel. Some works provides to use the multiple antennas for both transmit and receive of RFID readers. In this paper, we propose a perspective of blind channel estimation is presented to the RFID reader receiver for multiuser detection. Furthermore, the multiple-input and multiple-output (MIMO) of channel measurement is verified with the multiple antennas at the RFID reader and provides the multiple tags are under test. We also propose a linear receiver to estimate the received signal, where provides a zero-forcing (ZF) and a minimal mean square error (MMSE) in order to estimate the channel state information (CSI) at the reader receiver. Under the signal estimation, we shown the blind order signal estimated so that the reader can adapt as the multiple tag and available the detection simultaneously.

Numerical Surrogates for Human Observers in Myocardial Motion Evaluation From SPECT Images

In medical imaging, the gold standard for image-quality assessment is a task-based approach in which one evaluates human observer performance for a given diagnostic task (e.g., detection of a myocardial perfusion or motion defect). To facilitate practical task-based image-quality assessment, model observers are needed as approximate surrogates for human observers. In cardiac-gated SPECT imaging, diagnosis relies on evaluation of the myocardial motion as well as perfusion. Model observers for the perfusion-defect detection task have been studied previously, but little effort has been devoted toward development of a model observer for cardiac-motion defect detection. In this work, we describe two model observers for predicting human observer performance in detection of cardiac-motion defects. Both proposed methods rely on motion features extracted using previously reported deformable mesh model for myocardium motion estimation. The first method is based on a Hotelling linear discriminant that is similar in concept to that used commonly for perfusion-defect detection. In the second method, based on relevance vector machines (RVM) for regression, we compute average human observer performance by first directly predicting individual human observer scores, and then using multi reader receiver operating characteristic analysis. Our results suggest that the proposed RVM model observer can predict human observer performance accurately, while the new Hotelling motion-defect detector is somewhat less effective.

Myometrial invasion in endometrial cancer: diagnostic performance of diffusion-weighted magnetic resonance imaging 3.0-T

A total of 68 patients with histologically proven endometrial cancer were preoperatively evaluated with a 3.0 T magnetic resonance (MR) unit. Two radiologists interpreted the depth of myometrial invasion on T2-weighted and diffusion-weighted(DW)MR (b=700 s/mm2) imaging. Myometrial tumor spread was classified as superficial (<50%) or deep (≥50% myometrial thickness). Statistical methods included Kappa statistics for reader agreement, accuracy assessment and receiver operating characteristic analysis for diagnostic performance comparison. For assessing the depth of myometrial invasion, the diagnostic accuracy, sensitivity and specificity were as follows: T2-weighted imaging-reader 1st, 61.8%, 60.0% and 65.2%; reader 2nd, 66.2%, 64.4% and 69.6%; T2-weighted combined DW imaging-reader 1st, 86.8%, 84.4% and 91.3%; reader 2nd, 89.7%, 86.7% and 95.7%. Reader agreement was excellent for T2-weighted combined DW imaging (Kappa=0.818). For assessing deep myometrial involvement, ROC analysis showed that the diagnostic accuracy was significantly higher on T2-weighted combined DW imaging than that on T2-weighted imaging. The AUC (area under the curve) values measured by two readers on T2-weighted and T2-weighted combined DW imagings were 0.626, 0.879 and 0.670, 0.912 respectively. The addition of 3.0T MR diffusion-weighted to T2-weighted imaging can improve the diagnostic performance of MR imaging in the assessment of myometrial invasion. Key words: Endometrial neoplasms; Diffusion-weighted imaging

Extending Reading Range of Commercial RFID Readers

In this paper, multisine excitation signals are used to extend the reading range of commercial RF identification readers. To do so, a commercial reader is equipped with an external multisine front-end that implements previous mathematical proposals. A mathematical description is presented in order to show the ability of multisine signals to communicate data, with minimal changes in the downlink path, while no changes are required in the conventional tag architecture. Moreover, and most important, if a proper multisine design is performed, a conventional reader receiver is still able to demodulate and decode the backscattered multisine signal from the tag, without any hardware change. Thus, guidelines are presented for multisine design, including multisine nature, central tone positioning, tone separation, and bandwidth requirements. In order to evaluate the reading range improvement, when compared with the conventional single carrier approach with the same average power, two experiments are conducted: in the first one, an oscilloscope is used to measure the tag response and to decide whether the tag does or does not respond. In the second measurement scenario, the downlink path is implemented by the reader combined with the front-end and the uplink is implemented solely by the reader. In this case, the decision on successful tag response is taken when the reader reads the tag identification. The first measurement scenario has pointed out for a maximum reading range improvement of near 43% for an eight-tone multisine signal with 2-MHz tone separation. In the second scenario, a more realistic one, a reading range improvement of almost 25% has been obtained for a 8 + 1 tones multisine.

Design of Reader Baseband Receiver Structure for Demodulating Backscattered Tag Signal in a Passive RFID Environment

In this paper, we present a demodulation structure suitable for a reader baseband receiver in a passive radio frequency identification (RFID) environment. In a passive RFID configuration, an undesirable DC-offset phenomenon may appear in the baseband of the reader receiver, which can severely degrade the performance of the extraction of valid information from the received tag signal. To eliminate this DC-offset phenomenon, the primary feature of the proposed demodulation structures for the received FM0 and Miller subcarrier signals is to reconstruct the signal corrupted by the DC-offset phenomenon by creating peak signals from the corrupted signal. It is shown that the proposed method can successfully detect valid data, even when the received baseband signal is distorted by the DC-offset phenomenon.

Design of Reader Baseband Receiver Structure for Demodulating Backscattered Tag Signal in a Passive RFID Environment

In this paper, we present a demodulation structure suitable for a reader baseband receiver in a passive radio frequency identification (RFID) environment. In a passive RFID configuration, an undesirable DC-offset phenomenon may appear in the baseband of the reader receiver, which can severely degrade the performance of the extraction of valid information from the received tag signal. To eliminate this DC-offset phenomenon, the primary feature of the proposed demodulation structures for the received FM0 and Miller subcarrier signals is to reconstruct the signal corrupted by the DC-offset phenomenon by creating peak signals from the corrupted signal. It is shown that the proposed method can successfully detect valid data, even when the received baseband signal is distorted by the DC-offset phenomenon.

A High Linearity Low Noise Integrated UHF RFID Reader Receiver Front-end

A High Linearity Low Noise Integrated UHF RFID Reader Receiver Front-end

Ultra-high-frequency radio frequency identification reader receiver with 10 dBm input P1 dB and −74 dBm sensitivity in 0.18 µm CMOS

Ultra-high-frequency radio frequency identification reader receiver is implemented in 0.18 µm CMOS. Based on the key parameter analysis for the reader receiver, the dynamic range concept is proposed to define the specifications and evaluate the performance of a reader receiver. The presented receiver utilises a quadrature direct-conversion architecture which consists of passive mixers, baseband programmable gain amplifiers (PGAs) and low-pass filters (LPFs). Both good input matching and as high as 10 dBm input P1 dB of the RF front-end is achieved by utilising the passive mixers driven by square wave local oscillators. In the analogue baseband, four PGAs provide a gain control range higher than 80 dB and the LPFs have a reconfigurable bandwidth from 100 kHz to 1.6 MHz to optimise noise performance under different Rx data rates. The on-chip DC-blocker with controllable cut-off frequency is proposed to avoid DC offset problems and obtain a fast settling time simultaneously. In the normal mode, the receiver sensitivity achieves −74 dBm with 12.9 dB output signal-to-noise ratio. An alternative radio frequency receiving path with a low noise amplifier (LNA) improves the receiver sensitivity in the listen-before-talk mode by 14 dB. The total power dissipation is only 58 mW with 1.8 V supply voltage.

Multipacket Reception of Passive UHF RFID Tags: A Communication Theoretic Approach

This paper develops a communication theoretic model for the design and analysis at the physical layer of a reader receiver structure for passive UHF Radio Frequency IDentification (RFID). The objective is attaining multipacket reception capabilities which in turn help the fast resolution of multiple tags through a more rapid and power efficient arbitration of the tags collisions. In particular, we derive a parametric continuous time model for the subspace of a tag signal at the noisy receiver/reader, which in addition to being affected by fading and receiver delay, exhibits wide variations in the symbol frequency and transmission delay, due to imperfections in the RFID hardware design. Our main contribution is in showing that channel fading, the difference in delay and the tags frequency dispersion can be transformed from foes to friends by exploiting them in a multipacket receiver. In fact, signals colliding from different tags are more easily separable by estimating the sensor specific variation in frequency and delay and using these estimates in a multiuser receiver. In our study, we specifically consider a successive interference cancellation algorithm followed by a maximum likelihood sequence decoder, that iteratively reconstructs one signal contribution at a time and then removes it from the received signal. Numerical simulations show that the estimates and proposed algorithm are effective in recovering collisions. The proposed algorithm is then incorporated into a numerical simulation of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> -protocol for UHF RFID tags and is shown to be effective in providing fast and power efficient arbitration.

Study on the reader baseband receiver structure for the demodulation of subcarrier signal in a passive RFID environment

AbstractIn this article, we present a subcarrier demodulation structure to eliminate an undesirable DC‐offset phenomenon, which may appear in the baseband of the reader receiver under passive radio frequency identification environment.To achieve the requirement, the primary feature of the proposed demodulation structure is to reconstruct the signal corrupted by the DC‐offset phenomenon by creating peak signals from the corrupted signal. In the case of the Miller subcarrier signal, the phase inversion information in the symbol duration is used for generating the peak signal. It is shown that the proposed method can successfully detect valid data from the received signal, even when the received baseband signal is distorted by the DC‐offset phenomenon. In addition, the performance of the proposed method is slightly better than or comparable to that of the well‐known‐matched filter‐type baseband receiver in the band‐limited channel environments. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1264–1272, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25995

Analysis and measurement for passive tag modulationperformance of backscatter link

Optimal conditions for maximizing the effectively received power of reader receiver in passive ultra high frequency radio-frequency identification system are analyzed in this paper. The mismatched impendence affecting modulation index of tag backscatter link is discussed. Expressions of backscattered modulation indexes for calculating normalized effective received power of reader receiver, lower boundary of signal-to-noise ratio for demodulated output signal, and bit error rate are derived. Modulation indexes of backscatter link under different parameters are measured in open indoor environment. The measurement results show that the tag can be detected successfully when the modulation index of backscatter link is in a range from 5% to 10%.

Optimum ASK Modulation Scheme for Passive RFID Tags Under Antenna Mismatch Conditions

We propose optimized ON/OFF states of the backscattered amplitude shift keying (ASK) modulator for the passive RF identification (RFID) tags. This takes into account both the reader receiver sensitivity and tag antenna mismatch conditions. Based on the analysis of the power transfer between the passive RFID tag and reader, we derived the optimum configuration of the ASK modulator. It maximizes the harvestable power to enhance the identification range between the tag and reader. The performance of the proposed modulator configuration was superior to the conventional scheme. We also developed an optimization procedure of the modulator for a given receiver sensitivity of the reader and various antenna mismatch conditions of the tag.

Sensitivity improvement of the receiver module in the passive tag‐based RFID reader

AbstractIn this paper, we have designed an RFID reader receiver system for improving the performance of the passive Tag‐based 908.5–914 MHz RFID reader, and analyzed the system performance vis‐à‐vis frequency, reader, and tag properties. The commercial receiver system causes a loss in sensitivity because of its 24 capacitors and six inductors. To improve the overall sensitivity of the receiver, we have designed a system using a circulator, low noise amplifier (LNA) and a SAW filter. The experimental results show that the use of a circulator to separate the Tx/Rx paths eliminates interference, the LNA improves the sensitivity of the Rx module and SAW filter eliminates the noise and spurious components in the received signal. Copyright © 2009 John Wiley &amp; Sons, Ltd.

STUDY ON THE DEMODULATION STRUCTURE OF READER RECEIVER IN A PASSIVE RFID ENVIRONMENT

In this paper, we present a demodulation structure suitable for a reader receiver in a passive Radio Frequency IDentification (RFID) environment. In a passive RFID configuration, undesirable DC-offset phenomenon may appear in the baseband of the reader receiver. As a result, this DC-offset phenomenon can severely degrade the performance of the extraction of valid information from a received signal in the reader receiver. To mitigate the DC-offset phenomenon, we propose a demodulation structure to reconstruct a corrupted signal with the DC-offset phenomenon, by extracting useful transition information from the corrupted signal. It is shown that the proposed method can successfully detect valid data from a received signal, even when the received baseband signal is distorted with the DC-offset phenomenon.

Design criteria for the RF section of UHF and microwave passive RFID transponders

A set of design criteria for the radio-frequency (RF) section of long-range passive RF identification (RFID) transponders operating in the 2.45-GHz or 868-MHz industrial, scientific, and medical (ISM) frequency ranges is derived in this paper, focusing in particular on the voltage multiplier, the power-matching network, and the backscatter modulation. The paper discusses the design tradeoffs between the error probability at the reader receiver and the converted RF-dc power at the transponder, determining the regions of the design space that allow optimization of the operating range and the data rate of the RFID system.