Ultra-wideband Radio Frequency Research Articles

Spectral extrapolation for ultra-wide band radio frequency super-resolution tumor localization in the breast.

The use of ultra-wide band (UWB) radio frequency (RF) as an alternative to x-ray mammography for the detection and localization of breast tumors has been an area of focused research over the last decade. Unlike x-rays, UWB RF is non-ionizing and poses no risk of inducing cancer in examined patients. However, the reduction in operating frequency of UWB RF compared to x-rays results in much poorer localization when using classical space-time adaptive signal processing. This work investigates the synergistic use of a temporal signal spectrum extrapolation technique and contemporary basis pursuit de-noising (BPDN) beamforming to achieve medically relevant tumor localization accuracy within a heterogeneous simulated breast volume. If the beamforming process is viewed as a matched filtering operation, the spectrum extrapolation technique artificially increases the bandwidth of the received signal to afford much sharper correlations and hence contributing to increased localization accuracy. BPDN also contributes to increased localization accuracy by employing L1-norm constraints which shows marked clutter suppression effects in this context.

Rapidly Tunable Dual-Comb RF Photonic Filter for Ultrabroadband RF Spread Spectrum Applications

We demonstrate a rapidly frequency-tunable radio frequency (RF) filter using microwave photonics technology for ultrawideband RF spread spectrum applications. A pair of electro-optic frequency combs is arranged as a dispersive tapped delay line in a differential detection configuration to implement a programmable finite impulse response RF filter. Our photonic scheme enables both fast frequency tuning on the order of tens of nanoseconds and wide tuning range (>7.5 GHz) with minimal variation of RF gain and passband shape. The low control voltage (ca. 1 V) and the linear relationship between control voltage and passband frequency facilitate agile frequency tuning for processing of signals with time-varying frequency content, while differential detection increases the photocurrent by a factor of two and suppresses common mode intensity noise. We exploit the rapid tunability of the implemented filter to demonstrate dynamic tracking of frequency-hopped and chirped RF signals. An experiment that performs dynamic filtering of an input chirp signal (3.92-GHz center frequency, up-chirped by >2 GHz within 100 ns) obscured by strong broadband noise achieves $\sim 11$ -dB signal-to-noise ratio (SNR) improvement. The SNR obtained is in addition to that available from standard matched filtering or pulse compression processing, suggesting strong potential for enhanced resistance against broadband noise jamming.

Signal Processing Techniques for Chipless UWB RFID Thermal Threshold Detector Detection

This letter presents signal processing techniques to detect a passive thermal threshold detector based on a chipless time-domain ultrawideband (UWB) radio frequency identification (RFID) tag. The tag is composed by a UWB antenna connected to a transmission line, in turn loaded with a biomorphic thermal switch. The working principle consists of detecting the impedance change of the thermal switch. This change occurs when the temperature exceeds a threshold. A UWB radar is used as the reader. The difference between the actual time sample and a reference signal obtained from the averaging of previous samples is used to determine the switch transition and to mitigate the interferences derived from clutter reflections. A gain compensation function is applied to equalize the attenuation due to propagation loss. An improved method based on the continuous wavelet transform with Morlet wavelet is used to overcome detection problems associated to a low signal-to-noise ratio at the receiver. The average delay profile is used to detect the tag delay. Experimental measurements up to 5 m are obtained.

Wireless Concrete Mixture Composition Sensor Based on Time-Coded UWB RFID

This work presents a non-destructive wireless, concrete quality sensor based on chipless ultra-wideband radio frequency identification. The sensor is based on detecting the delay between two scattering modes induced by permittivity changes in the concrete. Theoretical, simulated and measured results with several embedded tags in samples are shown. The composition of the concrete blocks is remotely detected and classified.

Solar-Powered Wireless Temperature Sensor Based on UWB RFID With Self-Calibration

This paper presents a solar-powered wireless temperature sensor based on time-coded ultrawideband (UWB) radio frequency identification. A negative temperature coefficient resistor acts as the sensing element. It controls the current of a PIN diode connected to a UWB scattering antenna. The wireless sensor is self-calibrated using a narrowband tone, making its performance independent of the distance or orientation between the reader and the sensor. A consumption of 82 μA is demonstrated. An error under 0.6 °C within a 35 °C-70 °C temperature range is obtained for most of the cases.

Design of Circular Patch Microstrip Antenna with Egg Slot for 2.4 GHz Ultra-Wideband Radio Frequency Identification (UWB RFID) Tag Applications

This paper discusses concerning design of circular patch microstrip antenna for Radio Frequency Identification (RFID) tags application in microwave band. Circular microstrip antenna is designed with an egg slot on the ground plane and feed line to get ultra wideband. The design of microstrip antenna using Phenolic White Paper-FR2 with dielectric constant (or) =4.5. Based on simulation results, the antenna shows it works at frequency 2128-4807 MHz with gain of-17,398 dBi. The rectangular stub, caused the decreasing of bandwidth but the gain increase. By adding a rectangular stub on the ground plane, antenna works at frequency 1166 3475 MHz with increasing gain of-2,733 dBi.

Interaction of UWB Tag Backscattering With Close Metallic Reflectors

Ultrawideband (UWB) radio frequency identification (RFID) systems for real-time objects identification and localization represent a promising solution for a future generation of RFID, as they can overcome current narrowband technology limitations. As is well known from the literature, it is very challenging to ensure a reliable RFID communication when tags are placed in proximity of metallic reflectors. For this reason, we here investigate the interaction between a UWB RFID tag and a close metallic disturber, assuming semi-passive tags operating in modulated backscattering. The impact of the metallic reflector on the tags backscattering pattern and RFID system coverage is evaluated, showing how tag detection is affected since the energy is mainly concentrated in certain directions.

Comparative Study of UWB Communications over Fiber using Direct and External Modulations

This work presents an analysis of the Ultra Wide Band (UWB) Radio Frequency transmission over fiber using two types of modulation, direct and external. Both the modulation schemes are simulated by using OPTSIM 5.3 and optimized. Keywords: UWB, MB-OFDM, Radio Over Fiber, MZM, VCSEL, Q-Factor.

Techniques for the Analysis and Elimination of Transient Oscillations in Wideband and Ultra-Wideband Pulsed Power Amplifiers

Wideband pulsed power amplifiers (PAs) often exhibit undesirable transient oscillations at the trailing edges of the pulsed radiofrequency (RF) output. To combat this problem, this paper introduces an approach for predicting and eliminating such transient oscillations in pulsed PAs. Root causes for the transient oscillations are identified and contrasted with other time-domain pulse-distortion phenomena. Effective analytical techniques are presented for predicting transient instability during the PA design process. These techniques are demonstrated using a series of monolithic GaAs HBT Class-A and Class-C ultra-wideband (UWB) pulsed PA RF integrated circuits (RFICs). RFIC variants designed to exhibit no transient oscillations successfully show no such effects; RFIC variants designed without considering transient stability as a design tradeoff do indeed generate pulsed transients with measured oscillation frequencies and damping ratio parameters in less than 2% error with predictions. These results should greatly facilitate the design of pulsed transmitters for wideband/UWB communications and radar applications.

Transmission of 60 GHz Ultra Wideband Radio over Optical Fiber Using MB-OFDM

Ultra wideband radio over optical fiber (UROOF) technique enables the transmission of ultra wideband (UWB) radio signals over optical fibers by superimposing the UWB radio frequency signals of several gigahertz's on the optical continuous-wave carrier. UWB signals are characterized by an extremely large bandwidth. UWB frequency bands belong to 3.1-10.6 GHz according to the spectral mask defined by the Federal Communications Commission. This paper examines how by using multi-band orthogonal frequency division multiplexing (MB-OFDM) technique UWB transmission can be extended up to 60 GHz. MB-OFDM divides the spectrum into six band groups and 14 non-overlapping sub bands of 528 MHz bandwidth each. Each OFDM symbol is composed of 128 orthogonal subcarriers spaced 4.125 MHz apart.

Simple solutions for photonic power-efficient ultra-wideband system assisted by electrical bandpass filter

We propose and experimentally demonstrate two simple solutions for power-efficient ultra-wideband (UWB) radio frequency (RF) system assisted by an electrical bandpass filter (EBPF). In the first solution, any optical Gaussian pulse with enough bandwidth is transmitted over optical fiber link, and then converted to a power-efficient UWB pulse by an EBPF with a passband of 3.1–10.6 GHz. The transmission and modulation of UWB signal is processed in optical domain, whereas the generation of UWB is processed in electrical domain. Both UWB modulations of on-off keying (OOK) and binary phase shift keying (BPSK) are experimentally demonstrated. In the second solution, the EBPF is used to convert any electrical waveform to a power-efficient UWB pulse. Then the electrical UWB pulse is converted to an optical UWB pulse with a Mach-Zehnder modulator (MZM), and then distributed over long haul fiber link. These two solutions embody the advantages of both low-loss longhaul transmission of optical fiber and mature electrical circuits. And the millimeter-wave UWB signal is also demonstrated.

Graphene FET-Based Zero-Bias RF to Millimeter-Wave Detection

We report direct radio-frequency (RF) and millimeter-wave detection of epitaxial graphene field-effect transistors (FETs) up to 110 GHz with no dc biases applied, leveraging the nonlinearity of the channel resistance. A linear dynamic range of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$&gt;$</tex></formula> 40 dB was measured, providing at least 20-dB greater linear dynamic range compared to conventional CMOS detectors at transistor level. The measured noise power of the graphene FETs was <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim\!\hbox{7.5} \times \hbox{10}^{-18}\ \hbox{V}^{2}/\hbox{Hz}$</tex></formula> at zero bias and without <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{1}/f$ </tex></formula> noise. At a 50- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\Omega$</tex></formula> load, measured detection responsivity was 71 V/W at 2 GHz to 33 V/W at 110 GHz. The noise-equivalent power at 110 GHz was estimated to be <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim\!\hbox{80}\ \hbox{pW/Hz}^{0.5}$</tex></formula> . For the first time, we demonstrated graphene FETs as zero-bias ultrawideband direct RF detectors with comparable or better performance than state-of-the-art FET-based detectors without dc biases applied.

A Low-Cost UWB-RFID System Utilizing Compact Circularly Polarized Chipless Tags

In this letter, circularly polarized (CP) chipless tags for a ultrawideband radio-frequency identification (UWB-RFID) system are demonstrated for the first time. Different from conventional linearly polarized tags, CP tags not only help to significantly reduce the mutual coupling between the transmitting and receiving antennas in a UWB-RFID reader, but also greatly lessen the signal ratio between structural and antenna modes to improve system performance. In addition, short delay line is adopted to make the chipless CP tag with compact size. Nevertheless, a short delay line usually results in the structural and antenna modes being overlapped. To separate these signals, a time-domain processing scheme is then proposed and validated. Measured results and system demonstration show that the compact chipless CP tag is a very promising candidate for low-cost UWB-RFID applications.

A series peaked gm‐boosted 3.1–10.6 GHz CMOS CG UWB LNA for WiMedia

AbstractAn improved low noise amplifier (LNA) architecture is presented for WiMedia ultrawideband radio frequency frontend.The LNA topology addresses the issue of noise reduction keeping the power consumption to a minimum by employing the transconductance “gm” boosted common gate (CG) LNA topology with series peaking, operating in the WiMedia spectrum. This CG LNA utilizes an active gm‐boosting stage where the bias current is shared between the gm‐boosting stage and the self‐biased CG amplifying stage. In conjunction with an LC T‐network to further reduce the noise figure (NF) of the CG stage with finite output conductance (gds), inductive series peaking is used to widen the operating pass‐band. The proposed LNA is designed using the 130 nm IBM CMOS process and achieved an input return loss (S11) and an output return loss (S22) of −10 dB and −14 dB, respectively. The LNA exhibits forward power gain (S21) of around 14 dB with a NF ranging between 3.5 and 4.1 dB. The complete chip dissipates 5 mW from a 1.0 V supply with an input referred third order intercept point (IIP3) and an input referred 1‐dB compression point (ICP1dB) of −4.8 dBm and −12.1 dBm, respectively. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:532–535, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26573

Efficient Training Phase for Ultrawideband-Based Location Fingerprinting Systems

Location fingerprinting utilizing ultrawideband (UWB) radio frequency (RF) signals is an attractive alternative to conventional positioning concepts based on range, angle, or received signal strength estimates. Such a location fingerprinting method proves particularly beneficial in indoor environments with dense multipath propagation and nonline-of-sight situations where conventional approaches would fail. The ultrawide bandwidth allows for location fingerprints with many degrees of freedom and thus gives the important advantage that a single anchor suffices for good localization performance. The downside is that a large amount of training data is usually required, which makes the training phase time-consuming and tedious. In this paper, we propose and study a novel and efficient training method which is based on the idea of spatial signal prediction. We develop a regional channel model which supports spatial signal prediction in the vicinity of a reference point. We show that the parameters of this regional channel model can be estimated from very few measured received signals with known transmitter and receiver positions. The prediction accuracy and the location fingerprinting performance are evaluated with measured channel impulse responses obtained in an anechoic chamber and in a typical office environment.

Low Power Digital Baseband for Impulse Radio Ultra-Wideband Transceiver

In this paper, a low power digital baseband to be used together with impulse-radio ultra wideband radio frequency front-end has been presented. It can provide received pulse synchronization required for burst mode and low power operation. It also overcomes clock drift issue between different transceivers. The clock and data recovery is implemented fully in digital domain without the need of conventional phase-locked loop, delay locked loop or analog-to-digital converter. The chip is designed using 0.18 μm CMOS technology. It consumes 5 mW and can recover data up to 20 Mbps.

Generation and Detection of Ultra-Wideband Waveforms Using Stimulated Brillouin Scattering Amplified Spontaneous Emission

A scheme for the photonic generation and coherent detection of ultra-wideband radio-frequency (RF) noise is proposed and demonstrated. The technique relies on the amplified spontaneous emission of a broadened stimulated Brillouin scattering process in an optical fiber (SBS-ASE). The SBS-ASE noise is on-off modulated, and down-converted to the RF spectral range via heterodyne beating. The spectrum of the SBS-ASE is broadened beyond 1 GHz by tailored direct modulation of the pump wave. A data transmitter and a coherent receiver are demonstrated experimentally. Coherent detection of the noise waveform is based on the transmission of a delayed, unmodulated replica alongside the data (transmit reference). A performance analysis of the receiver statistics is provided. Q parameter values of 4.6 at data rates of 4 Mb/s are demonstrated.

A novel printed antenna for ultrawideband RFID (UWB-RFID) tag

In this article, we present the design of a modified crescent antenna for ultrawideband (UWB) radio frequency identification (RFID) tag. Different studies to optimize the design of this antenna for the UWB-RFID system have been performed, particularly to overcome the main challenges such as minimizing the size of the antenna, improving its read range, and the effects of the metallic objects on the antenna performance. To avoid the effect of the metals that may exist below the partial ground plane, the antenna is designed using a foam layer below the partial ground plane and a full ground plane below the foam layer at the bottom of the structure. As a result, the proposed antenna has a maximum read range between 0.9 m and 4.4 m, with the ability to cover the UWB with the existing of metallic objects below the antenna. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2528–2531, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25536

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.

Ultra-wideband cognitive interrogator network: adaptive illumination with active sensors for target localisation

The authors explore the potential application of cognitive interrogator network (COIN) in remote monitoring of mobile subjects in domestic environments, where the ultra-wideband radio frequency identification (UWB-RFID) technique is considered for accurate target localisation. The authors first present the COIN architecture in which the central base station (BS) continuously and intelligently customises the illumination modes of the distributed interrogators in response to the system's changing knowledge of the channel condition and subject movement. Subsequently, the analytical results of the locating probability and time-of-arrival (TOA) estimation uncertainty for a large-scale COIN with randomly distributed active sensors are derived based upon the implemented cognitive intelligence. As an important component to facilitate the adaptive illumination of the environment, the sequential-hypothesis-testing framework is proposed to estimate the tag antenna orientation. Finally, numerical examples are used to demonstrate the key effects of the proposed cognitive schemes on the system performance.