Passive RF Research Articles

A Novel Receiver Design with Joint Coherent and Non-Coherent Processing

In this paper, we propose a novel splitting receiver, which involves joint processing of coherently and non-coherently received signals. Using a passive RF power splitter, the received signal at each receiver antenna is split into two streams which are then processed by a conventional coherent detection (CD) circuit and a power-detection (PD) circuit, respectively. The streams of the signals from all the receiver antennas are then jointly used for information detection. We show that the splitting receiver creates a three-dimensional received signal space, due to the joint coherent and non-coherent processing. We analyze the achievable rate of a splitting receiver, which shows that the splitting receiver provides a rate gain of $3/2$ compared to either the conventional (CD-based) coherent receiver or the PD-based non-coherent receiver in the high SNR regime. We also analyze the symbol error rate (SER) for practical modulation schemes, which shows that the splitting receiver achieves asymptotic SER reduction by a factor of at least $\sqrt{M}-1$ for $M$-QAM compared to either the conventional (CD-based) coherent receiver or the PD-based non-coherent receiver.

Perfect Isolation: Dealing with Self-Jamming in Passive RFID Systems

Passive RF identification (RFID) readers transmit a continuous wave (CW) powering signal to remotely power up batteryless transponders, while simultaneously receiving a backscattered signal at the same frequency [1]. To separate the transmitter and receiver paths, readers use either a bistatic or monostatic antenna configuration. The first configuration employs two separate antennas, one to transmit and one to receive; in the second, the transmitter and receiver share a common antenna by means of a coupler or circulator. Both cases, however, suffer from poor transmitter-to-receiver isolation: strong CW signals can leak into the receiver, degrading its sensitivity to the weak transponder backscattered signals. Receiver sensitivity degradation occurs due to the leaked local oscillator (LO) phase noise [1] and also to the saturation of the front end caused by strong CW leakage. This requires high-dynamic-range capability in the RF stage [the low-noise amplifier (LNA) and mixer] as well as in the baseband stage [the amplifiers and analog-to-digital converters (ADCs)].

A High Temperature Passive GaN-HEMT Mixer for Downhole Communications

Abstract Declining reserves of easily accessible natural resources have motivated the oil and gas industry to drill deeper. Temperatures in these hostile wells can exceed 210 °C. Cooling and conventional heat extraction techniques are impractical in such a harsh environment. Reliable electronic designs that can sustain high temperature become necessary. This paper presents a high temperature passive RF mixer that is suited for downhole communications. The proposed mixer is designed to upconvert or downconvert the incoming signal with a low conversion loss (CL) and high linearity and reliable operation at temperature up to 250 °C. Gallium Nitride (GaN) is a wide band gap technology that can provide a reliable operation at the elevated ambient temperature, and the proposed mixer adopts a commercial GaN high electron mobility transistor (HEMT) technology. Measurement results indicate that the proposed mixer achieves CL of 6.5 dB at LO power of 2.5 dBm for the downconversion from 230–253 MHz to 97.5 MHz at 250 °C and input P1dB compression point lies at 5 dBm. The power dissipation of the mixer is virtually zero.

BSIM4 to PSP Model Conversion: A Case Study

BSIM4 model is not suitable for distortion analysis of circuits with bias point [Formula: see text], such as passive mixers and RF switches, due to discontinuities in higher order derivatives. Surface potential based PSP model has continuous derivatives to at least third-order, and is therefore suitable for intermodulation products simulation. This paper presents the case study of BSIM4 to PSP model conversion flow and comparison of active and passive mixers and SPDT RF switch simulation results. Simulation results show good agreement of original BSIM4 and converted PSP models’ CV, IV, compression point, conversion loss and noise figure, which validates the conversion flow. The converted model has a correct third-order intermodulation products (IM3) slope of three, allowing the simulation of intermodulation products, which was not possible with the original BSIM4 model.

Automatic Optimization of Single-Chip UHF RFID Tags

The automatic optimization is presented of the passive RF part of RFID, with special attention to single-chip UHF tags, and to the novel concept of RFID grids. The presented approach employs an optimization based on the Genetic Algorithm, and an efficient electromagnetic problem parameterization and novel solution strategy. A practical application example shows increase in overall performance.

Interposers: A Central Generic Technology for IoT

Also sometimes referred to as 2.5D integration, interposers are now a true and important component of the “3D world” based on die stacking technologies. Considered as an intermediate step in the field of high density die stacking (memory on logic, logic on logic, etc) this technology is on the other hand fully generic to manufacture heterogeneous systems which will constitute the basic of IoT (sensor with simple logic, RF capabilities and even energy harvesting). This paper presents first a short overview of the core technologies needed in this field. The versatility of these technical blocks, allowing to efficiently manufacture a large variety of interposer based devices, is then demonstrated through different subsystems related to IoT: sensors, passives, energy harvesters, RF communication. Some recent achievements in smart systems based on interposers mixing together passive components, microsystems and RF functions are then presented, and more particularly a system dedicated to short range high bandwidth communication for wireless HDMI and a system for implanted medical applications. In both cases, the gain in surface area is particularly important, making such solutions highly attractive.

RF-MEMS: an enabling technology for modern wireless systems bearing a market potential still not fully displayed

Since its first discussions in literature during late `90 s, RF-MEMS technology (i.e. Radio Frequency MicroElectroMechanical-Systems) has been showing uncommon potential in the realisation of high performance and widely reconfigurable RF passives for radio and telecommunication systems. Nonetheless, against the most confident forecasts for successful exploitation of RF-MEMS technology in mass-market applications, with the mobile phone segment first in line, already commencing from the earliest years of the 2000s, first design wins for MEMS-based RF passives have started to be announced just recently. This paper tries to depict and interpret the substantial circumstances that made RF-MEMS technology fail repeatedly, for about one decade, market forecasts. With the graphical support of the hype cycle concept, it will be shown that missed success of RF-MEMS was first caused by intrinsic (i.e. technology-related) factors. Subsequently, extrinsic elements linked to market acceptance and needs of such a technology, not fully weighted since the beginning, caused the second wave of disappointment around RF-MEMS. Quite unexpectedly, the context has changed rather significantly in recent years. The smartphones market segment started to generate a factual need for highly reconfigurable and high performance RF passive networks, and this circumstance is increasing the momentum of RF-MEMS technology that was expected about one decade ago. This work frames the current state of RF-MEMS market exploitation, also providing highlights on further expansion in mobile and telecommunication systems. Eventually, a focused state of the art report is developed around recent RF-MEMS research findings driven by requirements imposed by current market applications.

Third Harmonic Exploitation in Passive UHF RFID

This paper unfolds the recent concept of using harmonic signals generated by the nonlinear behavior of traditional passive UHF RF identification (RFID) chips. The harmonics generation of passive RFID chips is analyzed to highlight the influences of the matching network and the tag antenna. The proposed study relies on a theoretical model that explains the role in the harmonic production of different elements constituting the tag. The model also shows how to achieve a second communication channel exploiting the third harmonic frequency in addition to the fundamental frequency channel. Specifications and methodology are explained in a harmonic communication scenario. The regulations, harmonic RFID reader considerations, harmonic tag guidelines design, and metrics for its evaluation are discussed. In compliance with the standard regulations EPC Class-1 Gen2 RFID, a design example is presented. The performance of the solution is illustrated from simulation and measurements. The prototype example operates simultaneously at fundamental and third harmonic frequencies with a read range greater than 4.5 m.

Wireless Fully Passive Multichannel Recording of Neuropotentials Using Photo-Activated RF Backscattering Methods

Fully passive RF backscattering for wireless monitoring of neuropotentials, electrical activity generated by neurons, is a promising recording technique that may subdue some of the safety restraints observed in traditional active or passive recording schemes. The fully passive device operates without power supply or regulating elements and exhibits a highly simplified implant circuit topology. However, a critical challenge is its current limitation to single channel recording. Here, a method of integrating multiple channels onto the fully passive system is demonstrated that preserves its fully passive qualities and a single shared antenna. Multichannel recording is implemented by introducing photo-selective and photo-sensitive switches to individual channel electrodes to control the activation of individual recording operations via an external multi-band light source. These multi-modal wireless processes are simulated and implemented on Pyrex substrates that demonstrate recording of emulated neuropotential signals as low as Vm ~ 0.7 mV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> with at least 10-dB channel isolation as tested in air.

A Sub-mW Fully Integrated Wide-Band Receiver for Wireless Sensor Network

This letter presents low power implementation of a fully integrated wide band receiver for wireless sensor network. The receiver targets extremely low power operation with wide band coverage. Fabricated in 28 nm CMOS process, the receiver employs a passive mixer-first RF front-end with zero-IF architecture which is driven by non-overlapping four-phase local oscillator (LO). To minimize power consumption in LO driving stage which consumes the largest portion of power in this structure, supply voltage and device size optimization techniques are introduced. Enhanced non-overlapping LO circuit is proposed to prevent degradation of the noise figure. The receiver also includes a low power base band amplifier and in-band noise reduced biquad filter. The total receiver chain achieves conversion gain of 55 dB, noise figure of 13.6 dB and IIP3 of $-$ 7.5 dBm (@10 MHz spacing) with power consumption under 1 mW at the frequency band of 0.85 $\sim$ 2.55 GHz.

A Passive FPAA-Based RF Scatter Meteor Detector

In the article, we present a hardware meteor detector. The detection principle is based on the electromagnetic wave reflection from the ionized meteor trail in the atmosphere. The detector uses the ANADIGM field programmable analog array (FPAA), which is an attractive alternative for typically used detecting equipment—a PC computer with dedicated software. We implement an analog signal path using most of available FPAA resources to obtain precise audio signal detection. Our new detector was verified in collaboration with the Polish Fireball Network, the organization which monitors meteor activity in Poland. When compared with currently used signal processing PC software employing real radio meteor scatter signals, our low-cost detector proved to be more precise and reliable. Due to its cost and efficiency superiority over the current solution, the presented module is going to be implemented in the planned distributed detectors system.

A conductive shielded compact antenna hat for inverted‐F antennas

ABSTRACTWe propose a conductive shielded compact antenna hat, which can be utilized as a low loss passive RF repeater or coupler, to perform the RF compatibility testing of the aircraft, rocket, and launch vehicle using inverted‐F type antennas. Although the onboard antenna is very closely enclosed by the proposed antenna hat without RF absorbers, the resonance of the antenna itself is hardly affected compared to the free space radiation. The antenna hat which is fabricated for the S‐band inverted‐F antenna with the size of 74 × 13 × 16 mm3 has the small enclosure of 88 × 35 × 44 mm3, the return loss of 25.6 dB, the insertion loss of 0.3 dB, and the leakage loss of 52.5 dB at 2.25 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:220–223, 2015

A 24‐GHz radar sensor with a six‐port network for short‐range detection

ABSTRACTThe miniaturized radar sensor for detecting short distances is realized using a six‐port network. The six‐port network of the radar sensor consists of passive components and RF power detectors. The power detector obtains a highly accurate DC voltage because DC offsets are cancelled using a dummy structure in the detector. The maximum error of a distance measurement to 3 m is approximately 2% for a single target. Using traveling wave antennas, the distances to two targets with different directions are measured with 6.7% maximum detection error to 1 m. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2634–2637, 2014

Wireless Power Transmission: R&amp;amp;D Activities Within Europe

Wireless power transmission (WPT) is an emerging technology that is gaining increased visibility in recent years. Efficient WPT circuits, systems and strategies can address a large group of applications spanning from batteryless systems, battery-free sensors, passive RF identification, near-field communications, and many others. WPT is a fundamental enabling technology of the Internet of Things concept, as well as machine-to-machine communications, since it minimizes the use of batteries and eliminates wired power connections. WPT technology brings together RF and dc circuit and system designers with different backgrounds on circuit design, novel materials and applications, and regulatory issues, forming a cross disciplinary team in order to achieve an efficient transmission of power over the air interface. This paper aims to present WPT technology in an integrated way, addressing state-of-the-art and challenges, and to discuss future R&D perspectives summarizing recent activities in Europe.

Adaptive Noise Cancellation for Two Frequency Radar Using Frequency Doubling Passive RF Tags

The use of an adaptive noise-cancellation technique has been explored in order to separate multiple sources of motion for a two-frequency Doppler radar system. A 2.45-GHz fundamental Doppler radar system was used together with a harmonic Doppler radar receiver to measure and identify two moving reflectors; one with a harmonic tag and one without. While the tagged motion alone was detected by the harmonic receiver, least mean squares and normalized least mean squares algorithms were applied to the fundamental receiver output to filter out the tagged-related motion content and successfully isolate the information content associated with only the non-tagged motion. Simulations were performed to study the effect of various parameters on the performance of the algorithms, and experiments were conducted to validate the feasibility of the method.

Turning an SOI Into MEMS Devices for Optics and RF

This paper reports a use of SOI wafers in various MEMS (microelectromechanical systems) applications in micro optics and radio frequency devices. SOI wafer was originally developed for integrated circuits of improved performances in terms of suppressed current leakage and stray capacitance. At the same time, SOI has been used a lot in the field of MEMS due to the readiness of use as a mechanical material. Microstructures of high aspect ratio and small footprint have been made relatively easily by using the recent DRIE (deep reactive ion etching) processes compared with the anisotropic etching in a liquid phase. Despite the simple layer structure of SOI, various mechanical and electrical topologies were possible by using an electrical interconnection between the layers via a stiction bar. As an example of DRIE-processed SOI MEMS devices, we show a vertical-comb drive actuator with an initial offset angle for optical scanners, MEMS with integrated high-voltage driver circuits, micro XYZ-stages with electrostatic actuators, and all silicon passive RF device using integrated SPDT (single-pole double throw) switches.

Novel ESD protection solution for single-ended mixer in GaAs pHEMT technology

This paper develops an improved electrostatic discharge (ESD) protection solution built with a novel dual-gate, depletion-mode pHEMT device in the GaAs technology. The successful implementation of this ESD clamp in a single ended passive RF mixer with a Human Body Model (HBM) ESD protection level of over 1.8kV is also demonstrated. The ESD protected mixer is also shown to maintain its RF integrity with only a minimal degradation in the conversion loss and noise figure.

Novel Design of a Highly Sensitive RF Strain Transducer for Passive and Remote Sensing in Two Dimensions

A novel design of a highly sensitive wireless passive RF strain transducer is presented based on a patch antenna loaded with an open loop that is capable of sensing strain independently in two directions. An original idea of utilizing a cantilever at the gap of the open loop significantly improves the sensitivity of resonant frequency shifts. The frequency shifts in two distinct resonant modes are detected based on two dominant orthogonal modes of the patch resonators. In measurements, the prototypes achieved a sensitivity of 2.35% frequency shift per 1% strain, more than twice that of existing strain transducers of the same class. In simulations, the new design achieved a theoretical sensitivity up to four times as high as existing designs of RF passive wireless strain transducers. The ground plane allows for the sensitivity of the sensor to be independent from the applied surface. An implementation example of the passive remote sensing system based on the proposed strain transducer is also discussed as a proof-of-concept case. Based on calculations, the interrogation method in the example shows a radar cross section fluctuation of 3.8 dB corresponding to the strain induced at the sensor.

Handbook of RF, Microwave, and Millimeter-Wave Components. Edited by Leonid A. Belov, Sergey M. Smolskiy and Victor N. Kochemasov, Artech House, 2012; 504 pages. Price: £119.00, ISBN 978-1-60807-209-5

This unique and comprehensive resource offers you a detailed treatment of the operations principles, key parameters, and specific characteristics of active and passive RF, microwave, and millimeter-wave components. The book covers both linear and nonlinear components that are used in a wide range of application areas, from communications and information sciences, to avionics, space, and military engineering.

Equivalent Circuit Representation of Silicon Substrate Coupling of Passive and Active RF Components

Equivalent Circuit Representation of Silicon Substrate Coupling of Passive and Active RF Components