Radio Frequency Receiver Research Articles

A Microfluidic, Reversibly Stretchable, Large‐Area Wireless Strain Sensor

AbstractThis article describes the implementation and characterization of a new self‐contained large‐area wireless strain sensor, operating around 1.5 GHz, based on the concept of multi‐layer microfluidic stretchable radiofrequency electronics (μFSRFEs). Compared to existing solutions, the presented integrated strain sensor is capable of remotely detecting repeated high tensile dynamic strains of up to 15% over very large surfaces or movable parts, and gets rid of all hardwiring to external storage or data processing equipment. Unlike conventional electronic devices, the major part of the sensor is a mechanically reconfigurable and reversibly deformable patch antenna, which consists of two layers of liquid metal alloy filled microfluidic channels in a silicone elastomer. A simplified radiofrequency (RF) transmitter composed of miniaturized rigid active integrated circuits (ICs) associated with discrete passive components was assembled on a flexible printed circuit board (FPCB) and then heterogeneously integrated to the antenna. The elastic patch antenna can withstand repeated mechanical stretches while still maintaining its electrical function to some extent, and return to its original state after removal of the stress. Additionally, its electrical characteristics at frequency of operation are highly sensitive to mechanical strains. Consequently, not only is this antenna a radiator for transmitting and receiving RF signals like any other conventional antennas, but also acts as a reversible large‐area strain sensor in the integrated device. Good electrical performance of the standalone antenna and the RF transmitter sub‐module was respectively verified by experiments. Furthermore, a personal computer (PC)‐assisted RF receiver for receiving and processing the measured data was also designed, implemented, and evaluated. In the real‐life demonstration, the integrated strain sensor successfully monitored periodically repeated human body motion, and wirelessly transmitted the measured data to the custom‐designed receiver at a distance of 5m in real‐time.

Parametric Photonic Channelized RF Receiver

A new class of photonic channelized radio-frequency (RF) receiver is proposed and demonstrated. The new device relies on generation of high fidelity signal copies by wavelength multicasting in a self-seeded, two-pump parametric mixer. Signal copying to widely spaced wavelengths enables channelization of the full RF bandwidth using a single periodic filter. The channelization uses freely tunable frequencies of newly generated copies and eliminates the need for construction of a dense, narrowband filter bank. The new concept is demonstrated by channelization of four subcarrier channels with 1-GHz spacing and greater than 20-dB extinction ratio between extracted channels.

Sensing Optimization for an Receiver Structure in Cognitive Radio Systems

This paper describes the optimization of spectrum sensing in terms of the throughput of a cognitive radio (CR) system. Dealing with the optimization problem of spectrum sensing, this paper evaluates the throughput of a CR system by considering such situations as the penalty time of a channel search and incumbent user (IU) detection delay caused by a missed detection of an incumbent signal. Also, this paper suggests a serial channel search scheme as the search method for a vacant channel, and derives its mean channel search time by considering the penalty time due to the false alarm of a vacant channel search. The numerical results suggest the optimum sensing time of the channel search process using the derived mean channel search time of a serial channel search in the case of a sensing hardware structure with single radio frequency (RF) path. It also demonstrates that the average throughput is improved by two separate RF paths in spite of the hardware complexity of an RF receiver.

Reconfigurable parametric channelized receiver for instantaneous spectral analysis

We propose and demonstrate a photonic approach to a reconfigurable channelized radio frequency (RF) receiver for instantaneous RF spectrum monitoring and analysis. Our approach relies on the generation of high quality copies of the RF input by wavelength multicasting in a 2- pump self-seeded parametric mixer and the use of off-the-shelf filtering element such as Fabry-Perot etalon and wavelength division demultiplexers. The parametric channelizer scheme trades frequency non-degeneracy of the newly generated copies for ease of filtering design. Self seeding scheme employed to wavelength multicast the original RF signal to a large number of copies enables easy reconfigurability of the device by simple tuning of the three input waves, i.e. seed and pumps. Channelizer operation to up to 15 GHz bandwidth and channel spacing of 500 MHz is demonstrated. Reconfigurability is verified by tuning the receiver operating bandwidth and channel spacing.

A Behavior Level Analytical Method of Electromagnetic Susceptibility for Radio Frequency Receiver

Based on simplified Volterra model, a behavior-level simulation analysis approach of electromagnetic susceptibility (EMS) for radio frequency (RF) receiver is presented in this article. Third order simplified Volterra model is adopted to analyze receiver EMS. A general criterion for EMS is proposed according to EMS response characteristics in frequency domain, and then the simulation flow charts for calculating susceptibility thresholds are given. This approach is superior to the previous EMS analysis method on receiver, which mainly relies on experiments but lack simulation analysis. Take the dual frequency GPS receiver and zero IF receiver interfered by continue wave as examples for in-band and out-of-band susceptibility threshold calculation. Simulation results show that the proposed method is not only valid and effective, but also reduces the internal storage and simulation time, which is suitable to RF receiver EMS analysis and practical in engineering and technology field.

Theoretical Performance Analysis of an Image-Band Interference Canceller with Deterministic Imbalance Estimation

It is known that a heterodyne multimode receiver implemented with a single RF (Radio Frequency) receiver suffers from image-band interference due to imbalance, i.e. the phase error and the gain imbalance of the RF Hilbert transformer. The blind image band interference canceler with deterministic imbalance estimation that has been proposed mitigates the image-band interference. This performance of the image-band interference canceler is analyzed theoretically in this paper. As a result, it is revealed that estimation accuracy of the deterministic imbalance estimation is improved slightly as the imbalance becomes greater. In addition, it is also shown that the deterministic estimation achieves better performance as the power of image-band interference increases. The performance is confirmed by computer simulation.

High‐resolution interleaved water‐fat MR imaging of finger joints with chemical‐shift elimination

To study the use of an interleaved water-fat (IWF) sequence with a custom-made radiofrequency (RF) coil for high-resolution imaging of arthritic finger joints. High-resolution finger magnetic resonance imaging (MRI) was performed using a custom-made dedicated RF receiver coil and an IWF sequence. A phantom, a cadaver finger specimen, and the fingers of two normal controls and six arthritic subjects were imaged with a resolution of 156 × 156 × 600 μm. The appearance of anatomic structures on the IWF images were compared with images acquired with a regular sequence. The images were reviewed by two musculoskeletal radiologists for the depiction of anatomical structures and for the presence of abnormalities. The high-resolution images revealed detailed structures of the finger joints not detectable using typical clinical resolution. The IWF sequence gave more realistic depiction of subchondral bone thickness, and avoided false bone erosions displayed in the regular sequence. It also allowed better visualization of ligaments and tendons. This pilot study shows the feasibility and the potential usefulness of high-resolution IWF imaging for finger joint evaluation. This technique may be useful for the diagnosis and treatment assessment of arthritis, and for the study of joint disease pathogenesis.

Pre‐LNA smart soft antenna selection for MIMO spatial multiplexing/diversity system when amplifier/sky noise dominates

AbstractDue to a beamforming capability, Soft Antenna Selection (SAS) techniques have shown great performance improvements over the traditional antenna sub‐set selection schemes for Multi‐Input and Multi‐Output (MIMO) communication systems. A SAS method is basically defined by a pre‐processing matrix which is located in RF domain, either before or after the Low Noise Amplifier (LNA). In this paper, we propose a pre‐LNA SAS module which is adaptively tuned to maximise the mutual information or the Signal to Noise Ratio (SNR) gain for spatial multiplexing or diversity transmissions, respectively. The SAS optimality is discussed for the two practical cases where either the sky noise or the amplifier noise dominates. We analytically show that the pre‐LNA SAS method even outperforms the full‐complexity MIMO system for when the number of receive Radio Frequency (RF) chains is greater than or equal to the number of the transmit RF chains. The simulation results verify this claim and also superiority of the proposed scheme to the post‐LNA SAS. Copyright © 2010 John Wiley & Sons, Ltd.

A Novel Magnetic Resonance Phased-Array Coil Designed with FDTD Algorithm

Radio-frequency receiver phased-array coils in magnetic resonance imaging systems are used to pick up the signals emitted by the nuclei with high signal-to-noise ratio and a large region of sensitivity. Since the quality of obtained images strongly depends upon the correct choice of the coil geometry and position, array coils have to be designed by minimizing the mutual interaction among nearby coil elements and this is generally achieved by overlapping such adjacent elements. In this paper, we describe the use of a numerical solver based on finite-difference time-domain method to determine the optimal overlap distance, which guarantees the maximum decoupling level between the coil loops, for array coils constituted by various geometry elements. A novel array coil was designed, constituted by a couple of elliptical geometry elements in “folding” version around the animals’ spine curvature, for small animals’ imaging applications.

Video information recovery from EM leakage of computers based on storage oscilloscope

A hardware platform using broadband antenna, oscilloscope, and spectrum analyzer is designed to receive radio frequency (RF) signals from electromagnetic radiation leakage of computers in the office environment. The process of receiving and the processing techniques have also been given. Then, the software radio-based computing models and software algorithms are proposed to demodulate and decode the RF signals. An experimental result shows that the text information can be recovered from electromagnetic (EM) leakage wave of computer by this interception system. This architecture not only reduces the cost of the system’s hardware but also makes interception more flexible. The innovation points of this paper are recovering the video information in EM leakage wave of computers in an ordinary office environment based on public equipments and proposing the process of receiving processing techniques that only use the software radio-based computing models and software algorithms.

Analysis and Design of a Multistage CMOS Band-Pass Low-Noise Preamplifier for Ultrawideband RF Receiver

A CMOS low-noise preamplifier for application in a 3.1-10.6-GHz ultrawideband radio-frequency (RF) receiver system is presented. This is essentially a wideband-pass multistage RF preamplifier using a cascade of a three-segment band-pass LC ? -section filter with a common-gate stage as the front end. Fundamental design analysis in terms of gain, bandwidth, noise, and impedance matching for the amplifier is presented in detail. The preamplifier was fabricated using the low-cost TSMC 0.18-?m 6M1P CMOS process technology. The amplifier delivered a buffered power gain (S 21) of ? 14 dB with a -3-dB bandwidth (between the corner frequencies) of around 7.5 GHz. It consumed around 30 mW from a 2.5-V supply voltage. It had a minimum passband noise figure of around 4.7 dB, an input-referred third-order intercept point of -5.3 dBm, and reverse isolation (S 12) under -65 dB.

An Energy-Efficient ASIC for Wireless Body Sensor Networks in Medical Applications

An energy-efficient application-specific integrated circuit (ASIC) featured with a work-on-demand protocol is designed for wireless body sensor networks (WBSNs) in medical applications. Dedicated for ultra-low-power wireless sensor nodes, the ASIC consists of a low-power microcontroller unit (MCU), a power-management unit (PMU), reconfigurable sensor interfaces, communication ports controlling a wireless transceiver, and an integrated passive radio-frequency (RF) receiver with energy harvesting ability. The MCU, together with the PMU, provides quite flexible communication and power-control modes for energy-efficient operations. The always-on passive RF receiver with an RF energy harvesting block offers the sensor nodes the capability of work-on-demand with zero standby power. Fabricated in standard 0.18-¿m complementary metal-oxide semiconductor technology, the ASIC occupies a die area of 2 mm × 2.5 mm. A wireless body sensor network sensor-node prototype using this ASIC only consumes < 10-nA current under the passive standby mode, and < 10 ¿A under the active standby mode, when supplied by a 3-V battery.

Optimal Biasing of a Self-Homodyne Optically Coherent RF Receiver

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We present a technique that achieves the most efficient use of the linear dynamic range of available photodiodes without sacrificing the linearity of the radio-frequency (RF) digital receiver and photonic link based on optical phase modulation and coherent in-phase quadrature <formula formulatype="inline"><tex Notation="TeX">$(I/Q)$</tex> </formula> demodulation. We demonstrate, with a relative intensity noise (RIN)-limited optical system, that under these optimal bias conditions our 1-GHz coherent receiver achieves a link spurious-free dynamic range (SFDR), gain, and noise figure of 126.8 <formula formulatype="inline"><tex Notation="TeX">$\hbox{dB-Hz}^{2/3}$</tex></formula>, 8 dB, and 18.6 dB, respectively, and show the capability, with a shot-noise-limited optical source, to achieve an SFDR of 135.3 <formula formulatype="inline"><tex Notation="TeX">$\hbox{dB-Hz}^{2/3}$</tex></formula> and a noise figure of 6 dB. </para>

Receiver I/Q Imbalance: Tone Test, Sensitivity Analysis, and the Universal Software Radio Peripheral

The problem of determining the gain imbalance, quadrature skew, and local oscillator leakage of contemporary radio frequency receivers by tone test is considered. A least squares approach for indirect estimation of the sought-for parameters is proposed, which is linear in six out of its seven parameters. The performance of the method, particularly its accuracy as a function of measurement time, imbalance parameters, and signal-to-noise ratios, is investigated. The theoretical predictions of the performance are illustrated by Monte Carlo simulations and experimental data that are obtained from testing several universal software radio peripheral (USRP) receivers. This paper shows that, for the studied off-the-shelf receivers, gain imbalance and quadrature skew may accurately be predicted (i.e., < 0.1 dB and <, respectively) by employing baseband data covering only a handful of full periods of the excitation stimuli. Using short records of data, this paper also shows that local oscillator leakage adding a bias term in the receiver baseband data may suffer from a systematic bias error on the order of 15 dB in the estimate. To obtain local oscillator leakage estimates with an uncertainty on the order of 1 dB, the measurement time has to be increased by two orders of magnitude.

High-resolution 3D magnetic resonance imaging and quantification of carious lesions and dental pulp in vivo

The purpose of the study was to assess the feasibility of MRI of three-dimensional visualization and quantification of carious lesions, as well as measurement of the distance between the lesion and dental pulp in vivo. High-resolution 3D MRI was performed to measure seven carious lesions in vivo using gelatinous gadolinium-based oral contrast medium in combination with an intraoral radio frequency receiver coil on a clinical 1.5 T MRI scanner. Extension of the carious lesion in three spatial dimensions and the minimum distance between the lesion and dental pulp were quantified. When possible, the result was compared to an X-ray projection and an impression of the lesion taken using a plastic impression material before and after dental treatment. Carious lesions, including pit and fissure, approximal lesions, and occult dentin caries, could be visualized due to the MRI signal rise in the porous affected dentin. The minimum distance between the carious lesion and dental pulp could be determined in all cases. The results presented demonstrate the feasibility of high-resolution dental MRI to three-dimensionally visualize and quantify carious lesions, including approximal and occult caries lesions, and measure the minimum distance to the dental pulp.

Simulative investigation on the impact of laser-spectral width in single-tone radio-over-fiber transmission system using optical single side-band technique

In this paper, we analyzed the impact of laser-spectral width incorporating dual-electrode Mach–Zehnder modulator (DEMZM) in single-tone radio-over-fiber (RoF) transmission system by simulation setup. It is shown that an improvement in the measurement of received radio frequency (RF) power is achieved by reducing the laser line width from 100 MHz to 100 kHz, which further improves the BER rate and optical link by transmitting the information with low power. The results are calculated for 20 and 50 km optical single sideband (OSSB)–RoF transmission system by varying the chirp from 0 to −3 as it requires less bandwidth than optical dual sideband (ODSB)–RoF system and is tolerable for power degradation due to a chromatic fiber-dispersion, through a standard single-mode fiber (SSMF) carried by a continuous wave (CW) laser at 1550 nm of laser-spectral width varying from 100 MHz to 100 kHz with CW power of 10 mW that modulates a single RF channel of 20 GHz. Further, deployment of such lasers with OSSB scheme helps the telecom industry to reduce the designing cost of RoF communication systems.

Drift Errors in Passive Remote Wireless SAW Sensing With Multiple DPM

This paper addresses a probabilistic analysis of drift errors in passive remote wireless surface acoustic wave (SAW) sensing with multiple differential phase measurement (DPM). The rigorous probability density of the differential phase difference (DPD) is derived and its particular functions, all having no closed forms, are given for different signal-to-noise ratios (SNRs) in the received radio frequency (RF) pulses. Employing the von Mises/Tikhonov distribution, an efficient approximation is found via the modified Bessel functions of the first kind and zeroth order. Engineering features and small errors of the approximation are demonstrated. An analysis is given of the phase difference drift rate and error probability for the drift rate to exceed a threshold.

High Speed Receiver for Capsule Endoscope

In this study, a high-speed receiver for a capsule endoscope was proposed and implemented. The proposed receiver could receive 20Mbps data that was sufficient to receive images with a higher resolution than conventional receivers. The receiver used a 1.2GHz band to receive radio frequency (RF) signal, and demodulated the signal to an intermediate frequency (IF) stage (150MHz). The demodulated signal was amplified, filtered, and under-sampled by a high-speed analog-to-digital converter (ADC). In order to decode the under-sampled data in real time, a simple frequency detection algorithm was selected and was implemented by using a FPGA. The implemented system could receive 20Mbps data.

Lower Thoracic Spinal Cord Stimulation to Restore Cough in Patients With Spinal Cord Injury: Results of a National Institutes of Health–Sponsored Clinical Trial. Part I: Methodology and Effectiveness of Expiratory Muscle Activation

DiMarco AF, Kowalski KE, Geertman RT, Hromyak DR. Lower thoracic spinal cord stimulation to restore cough in patients with spinal cord injury: results of a National Institutes of Health–sponsored clinical trial. Part I: methodology and effectiveness of expiratory muscle activation. Objective Evaluation of the capacity of lower thoracic spinal cord stimulation (SCS) to activate the expiratory muscles and generate large airway pressures and high peak airflows characteristic of cough, in subjects with tetraplegia. Design Clinical trial. Setting Inpatient hospital setting for electrode insertion; outpatient setting for measurement of respiratory pressures; home setting for application of SCS. Participants Subjects (N=9; 8 men, 1 woman) with cervical spinal cord injury and weak cough. Interventions A fully implantable electrical stimulation system was surgically placed in each subject. Partial hemilaminectomies were made to place single-disk electrodes in the epidural space at the T9, T11, and L1 spinal levels. A radiofrequency receiver was placed in a subcutaneous pocket over the anterior portion of the chest wall. Electrode wires were tunneled subcutaneously and connected to the receiver. Stimulation was applied by activating a small portable external stimulus controller box powered by a rechargeable battery to each electrode lead alone and in combination. Main Outcome Measures Peak airflow and airway pressure generation achieved with SCS. Results Supramaximal SCS resulted in high peak airflow rates and large airway pressures during stimulation at each electrode lead. Maximum peak airflow rates and airway pressures were achieved with combined stimulation of any 2 leads. At total lung capacity, mean maximum peak airflow rates and airway pressure generation were 8.6±1.8 (mean ± SE) L/s and 137±30 cmH 2O (mean ± SE), respectively. Conclusions Lower thoracic SCS results in near maximum activation of the expiratory muscles and the generation of high peak airflow rates and positive airway pressures in the range of those observed with maximum cough efforts in healthy persons.

Nonlinear Processing in B-Mode Ultrasound Affects Carotid Diameter Assessment

Noninvasive diameter assessment in the common carotid artery (CCA) by means of ultrasound is a useful technique for estimation of arterial mechanical and dynamic properties, clinical screening and treatment monitoring. Before presentation on screen, ultrasound images are subjected to nonlinear processing, e.g., logarithmic compression and noise-level thresholding, to improve visualization. In addition, signal saturation may occur, either in the received radiofrequency (RF) signals or in their envelopes. The objective of this study is to evaluate the effect of signal nonlinearities on CCA diameter measurements by means of noninvasive B-mode ultrasound, comparing the performance of two different edge detectors. In 14 healthy subjects, three repeated ultrasonic acquisitions (6 s) without saturation were performed. The acquired RF signals were subjected off-line to envelope detection, logarithmic compression and various degrees of saturation applied to the signals before or after envelope detection. For the purpose of CCA diameter estimation, artery walls were automatically outlined frame by frame. As automatic edge detectors, we considered the sustain attack filter (SAF), based on exponentially decaying reference functions, and a derivative approach (DER), relying on the positions of first derivative maxima. Both methods are applied within a region-of-interest located on the CCA. No regularization of the detected wall positions by means of pre- or postprocessing is presently applied to directly relate the outcome of the edge detectors to the applied nonlinear processing. Diameter values assessed with SAF are unaffected by logarithmic compression because of the possibility to integrate the compression characteristic of the ultrasound system into the method. The estimated diameters values obtained with DER instead show differences in the order of 10% because of compression. Saturation affects DER more than SAF; DER exhibits larger intrarecording and intrasubject variations in the estimated diameter values. Therefore, SAF gives more precise and robust CCA diameter estimates than DER, and is more suited for integration in algorithms meant for vascular ultrasound image segmentation. This study demonstrates the relevant effects of nonlinearities such as saturation and logarithmic compression on the quality of noninvasive US CCA diameter measurements. (E-mail: peter.brands@esaote.nl)