Passive RF Research Articles

A SU-8-Based Microfabricated Implantable Inductively Coupled Passive RF Wireless Intraocular Pressure Sensor

With the growing demand in noncontact detection of human diseases, this paper presents an implantable passive wireless pressure sensor using an inductively coupled wireless sensing technique, particularly designed to monitor the intraocular pressure (IOP) of glaucoma patients. The microfabricated IOP sensor consists of a planar spiral gold coil inductor, a two-parallel-gold-plate (metal-insulator-metal) capacitor, and a SU-8 pressure-sensitive diaphragm. The IOP sensor is fully encapsulated inside biocompatible SU-8 stacking layers to isolate the IOP sensor from the biological tissue medium environment. By measuring the impedance phase dip frequency shift from the external coil, the IOP signal can be obtained through the implanted IOP sensor. The optimized size of the manually wound external coil was investigated. The readout distance is up to 6 mm from the implanted sensor. Characterization results show that the microfabricated IOP sensor has relatively high sensitivities-7035 ppm/mmHg in air and 3770 ppm/mmHg in saline medium-with pressure resolution lower than 1 mmHg, which is adequate for IOP monitoring application.

Self-Biased Low Loss Conductor Featured With Skin Effect Suppression for High Quality RF Passives

We present experimental data for artificial metaconductors exhibiting skin effect suppression at microwave frequencies. The metaconductor consists of a stack comprising twelve periods of alternating ferromagnetic (Permalloy) and normal metal (Cu) layers. Near the effective antiferromagnetic resonant frequency the average in-plane magnetic permeability of the stack approaches zero, leading to an increase in the skin depth. Compared to a Cu-based device, up to 70% loss reduction has been achieved by a metaconductor based coplanar wave guide at ~ 10 GHz without changing the propagation wavelength. Moreover, unlike conventional magnetic devices, no external magnetic bias is required due to the large magnetic anisotropy present in the ferromagnetic layers.

Design and Development of a Novel Passive Wireless Ultrasensitive RF Temperature Transducer for Remote Sensing

A wireless, passive, and ultrasensitive temperature transducer is presented in this paper. The transducer consists of split ring resonators loaded with micro-bimorph cantilevers, which can potentially operate up to millimeter-wave frequencies (above 30 GHz). As the temperature changes, the bimorph cantilevers deflect and result in a shift of the resonant frequency of the split rings. A design is proposed, that has a maximum sensitivity of 2.62 GHz/μm, in terms of frequency shift per deflection unit, corresponding to a sensitivity of 498 MHz/°C for an operating frequency around 30 GHz, i.e., a frequency shift of 1.6% per °C. Theoretically, it's about two orders of magnitude higher than the existing sensors observed in the same class. This sensor design also offers a high Q factor and is ultra-compact, enabling easy fabrication and integration in micro-electromechanical systems technology. Depending on the choice of materials, the proposed designs can also be utilized in harsh environments. As a proof of concept, a prototype is implemented around 4.7 GHz which exhibits a frequency shift of 0.05%/°C, i.e., 17 times more sensitive than the existing sensors.

Frequency-selective plasmonic wave propagation through the overmoded waveguide with photonic-band-gap slab arrays

Confined propagation of guided waves through the periodically corrugated channel sandwiched between two staggered dielectric photonic-band-gap slab arrays is investigated with the band-response analysis. Numerical simulations show that longitudinally polarized evanescent waves within the band gap propagate with insertion loss of ∼−0.2 to 1 dB (−0.05 to 0.4 dB/mm at G-band) in the hybrid band filter. This structure significantly suppresses low energy modes and higher-order-modes beyond the band-gap, including background noises, down to ∼−45 dB. This would enable the single-mode propagation in the heavily over-moded waveguide (TEM-type), minimizing abnormal excitation probability of trapped modes. This band filter could be integrated with active and passive RF components for electron beam and optoelectronic devices.

Quadrature Amplitude Modulated Backscatter in Passive and Semipassive UHF RFID Systems

Passive and semipassive UHF RF identification (RFID) systems have traditionally been designed using scalar-valued differential radar cross section (DRCS) methods to model the backscattered signal from the tag. This paper argues that scalar-valued DRCS analysis is unnecessarily limiting because of the inherent coherence of the backscatter link and the complex-valued nature of load-dependent antenna-mode scattering from an RFID tag. Considering modulated backscatter in terms of complex-valued scattered fields opens the possibility of quadrature modulation of the backscatter channel. When compared with binary amplitude shift keying (ASK) or phase shift keying (PSK) based RFID systems, which transmit 1 bit of data per symbol period, and thus 1 bit per on-chip clock oscillator period, tags employing vector backscatter modulation can transmit more than 1 bit per symbol period. This increases the data rate for a given on-chip symbol clock rate leading to reduced on-chip power consumption and extended read range. Alternatively, tags employing an M-ary modulator can achieve log2 M higher data throughput at essentially the same dc power consumption as a tag employing binary ASK or PSK. In contrast to the binary ASK or PSK backscatter modulation employed by passive and semipassive UHF RFID tags, such as tags compliant with the widely used ISO18000-6c standard, this paper explores a novel CMOS-compatible method for generating M-ary quadrature amplitude modulated (QAM) backscatter modulation. A new method is presented for designing an inductorless M-ary QAM backscatter modulator using only an array of switched resistances and capacitances. Device-level simulation and measurements of a four-state phase shift keying (4-PSK)/four-state quadrature amplitude modulated (4-QAM) modulator are provided for a semipassive (battery-assisted) tag operating in the 850-950-MHz band. This first prototype modulator transmits 4-PSK/4-QAM at a symbol rate of 200 kHz and a bit rate of 400 kb/s at a static power dissipation of only 115 nW.

Respiratory Monitoring and Clutter Rejection Using a CW Doppler Radar With Passive RF Tags

A Doppler radar system was built to detect the motion of modulated backscatter data from a passive tag, while rejecting the unmodulated backscatter from other elements. A harmonic tag was designed and fabricated to show the feasibility of sensing cardiopulmonary related Doppler shift in the received second harmonic signal. A fundamental frequency of 2.45 GHz was transmitted at a target and a quadrature homodyne receiver was used to sense the received second harmonic signal. The setup was used to first successfully isolate periodic motion from a tag on a programmable mechanical target in close proximity to other moving objects and to sense respiratory motion of a human subject. Respiratory data obtained from the tag was compared to a reference. The harmonic radar setup was then successfully used to isolate the respiration of a tagged human subject from an untagged large scattering object. The response of the harmonic radar was also compared to a 2.45 GHz Doppler radar for some experiment scenarios that clearly indicate the utility and potential for such systems.

A Wide-Swing Low-Noise Transconductance Amplifier and the Enabling of Large-Signal Handling Direct-Conversion Receivers

In this paper, the design of a wide-swing low-noise transconductance amplifier (LNTA) is presented in the context of passive mixer-based direct-conversion RF receivers, noting that the compression performance of such systems is limited by the initial voltage-to-current conversion. The proposed LNTA utilizes a stacked PMOS/NMOS common-gate configuration with its input common-mode voltage maintained by a class-AB operational transconductance amplifier (OTA). Linearization mechanisms and design procedures are explained both quantitatively and intuitively. Simulations of the LNTA at the typical corner, when ideally loaded, show an IIP3 + 32.8 dBm extrapolated at +12.5 dBm/-16.5 dBm CW blocking condition and an out-of-band 1-dB desensitization point of +22 dBm. These results are also shown to qualitatively agree with those extracted from an analytical model of the LNTA.

Improvement of the envelope – transient S-parameters' simulation in circuit and system simulation

This paper focuses on the behavioral modeling of the passive RF blocks from frequency-domain samples. This work is based on vector fitting (VF) approach which is a robust method for MIMO system identification in the frequency domain. This paper addresses firstly the problem of convergence using envelope transient (ET) on complex circuits, i.e. power amplifiers (PAs), where linear sub-circuits are widely described through S-parameters matrices derived from ElectroMagnetic (EM) simulations. An alternative way leads to combine VF method with an RLC synthesis process at the circuit level. This approach is validated on a simple circuit case and generalized to MIMO systems. Second application is the behavioral modeling of MIMO blocks at system level in a high-level spice-like system simulation tool which allows “Control Flow” simulations. The proposed approach combines on one hand the VF method with and impulse responses evaluation on the other hand. In consequence, bilateral behavioral models of MIMO system can be efficiently achieved irrespective of the number of access. This method is validated at once on simple and complex MIMO blocks. As a result, the topological behavioral modeling of complex PAs, which distinguish linear sub-circuits and nonlinear ones, is now possible in a high-level time-domain CAD tool.

Wafer-level multilayer integration of RF passives with thick BCB/metal interlayer connection in silicon-based SiP

This paper presents an integration technology for RF passives using benzocyclobutene (BCB)/metal multilayer interconnection for system-in-package applications. This technology has been specially developed for RF subsystem packages in which a thick polymer, BCB (more than 15 μm thick), is adopted as dielectric with lossy silicon as substrate for its excellent characteristics. Both dry-etch BCB and photosensitive BCB are applied in this work, and their processes are briefly introduced and compared. An RF power divider, an MIM capacitor, different types of RF inductors as well as a coupled microstrip based band-pass filter are fabricated and measured at wafer level. The results show good electrical performances, and accordingly the passives are well applicable in RF band. Moreover, the subsystem models including monolithic chips connected with passives are presented.

Graphene: Its Fundamentals to Future Applications

Currently, graphene is a topic of very active research fields from science to potential applications. For various RF circuit applications, including low-noise amplifiers, the unique ambipolar nature of graphene field-effect-transistors can be utilized for high-performance frequency multipliers, mixers, and high-speed radiometers. Potential integration of graphene on silicon substrates with CMOS compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene MOSFETs to minimize parasitics and improve gate modulation efficiency in the channel with zero or a small bandgap. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antennas, where its success depends on the quality of materials. We also attempt to discuss future applications and challenges of graphene.

Passive RFID at Millimeter Waves

This paper introduces a novel way to implement passive RF identification (RFID) at millimeter waves. Passive operation is achieved by adding an external mixing element between the tag antenna and a standard RFID chip. The mixing element converts the RFID reader signal from millimeter waves to RFID carrier frequency-the RFID chip operates as usual. Either passive or semipassive RFID circuits at any RFID carrier frequency can be used. The reader's TX and RX ports are similarly equipped with external mixers to convert the reader output to millimeter waves and received millimeter-wave signal to RFID carrier frequency. The paper analyses the concept theoretically with a Schottky diode as the mixing element. The design and experimental demonstration of the operation at 10 GHz are presented. Using an EPC-compliant UHF tag integrated circuit and reader, a range of 30 cm is demonstrated, but range extension to over a meter is feasible.

A Fully Integrated HF-Band Passive RFID Tag IC Using 0.18-$\mu\hbox{m}$ CMOS Technology for Low-Cost Security Applications

We present a fully integrated small-size HF-band passive RF identification (RFID) tag chip with authentication and security functions. The design of the RF transceiver and digital control of the tag IC is based on the International Organization for Standardization-14443 type-B protocol. The design of the key analog part of the tag IC is presented, which includes a robust demodulator for 10% amplitude shift keying envelope detection, a high-quality random number generator, and a voltage regulator that can handle a range of output load currents. To implement the secure data transaction with a reader, a 128-b advanced encryption standard (AES) with a new cyclic key generation is used for the data encryption and decryption. An on-chip 4-kb electrically erasable programmable ROM (EEPROM) is used to support the AES operation, tag identification, and tag self-destruction. The read and write accesses of the EEPROM are performed using a 128-b wide buffer with self-timed bursts. The tag chip is fabricated in a one-poly six-metal low-power 0.18-μm CMOS process with a CoSi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Schottky diode and EEPROM process. Using the scaled-down CMOS technology, the size of the tag chip is only 1.1 × 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , providing a cost-effective solution for everyday RFID applications.

RFID Deployment in INDIAN RAILWAYS: A case study of E-Transport Initiative in India 55 RFID

A technology lying largely unused since World War II has suddenly caught the attention of the whole world. The emergence of the industry led global RFID standard has accelerated the adoption of this new technology across sectors. It has helped to fully unlock and open existing opportunities and business applications responsive to today’s global needs. Design, Development and implementation of computer-based information systems and associated communication networks have led to the deployment and usage of this wireless technology. According to MCKINSEY &amp; COMPANY, “Railways in India is a sunrise industry! Indian Railways has got the status of super ‘JEWEL’. The Indian Railways (IR) is a truly great institution. It is a global giant that operates profitably, effectively and with relatively little government support”. The vastness of railways – cars, cargo, track, countries and conditions – presents a massive challenge for management of rolling stock and rail operations. Intellectual Property and Innovation Company’s( IPICO’s) low cost, passive RF technology enables consistently accurate identification and control of assets in virtually any operating environment. This paper tries to scrutinize the loopholes that exist in the system and examines the modus operandi of RFID technology to address such problems.

Revisiting RFID Link Budgets for Technology Scaling: Range Maximization of RFID Tags

Passive RF identification (RFID) tags are traditionally assumed to be downlink limited since typical tag sensitivity is considerably poorer than reader sensitivity, due to stringent power limitations. On the other hand, semipassive tags are generally uplink limited because of improvement in tag sensitivity for battery-assisted tags. In this paper, it is demonstrated that judicious choice and use of integrated circuit impedance for backscatter modulation will be needed to simultaneously maximize tag uplink and downlink ranges as passive tag designs improve. Optimal backscatter modulation indices for amplitude shift keying are derived for range maximization of next-generation low-power RFID tags.

DUAL-ANTENNA SYSTEM COMPOSED OF PATCH ARRAY AND PLANAR YAGI ANTENNA FOR ELIMINATION OF BLINDNESS IN CELLULAR MOBILE COMMUNICATIONS

For a cellular mobile communication system in narrow streets of urban areas, blind spots caused by shadowing of high buildings are a signiflcant problem. In this research, a new dual- antenna system (DAS) is proposed, including a power transmission network, a receiving and a reradiating antenna to realize a broad- angle beam control. An equivalent bi-static radar cross section (BRCS) is deduced to present a theoretical explanation to the operating principles of the DAS. The main advantage of this design over ordinary re∞ectarray antenna as a passive RF booster is its ∞exible beam control capabilities. The simulated BRCS of the proposed DAS, composed

UWB ranging in passive UHF RFID: proof of concept

A proof of concept for ultra-wideband (UWB)-based ranging in passive UHF RF identification (RFID) is presented. The proposed method uses the tag's backscatter modulation and thus does not require processing of the UWB signal by the tag. It is evaluated using measurements in an indoor environment similar to a warehouse portal in terms of channel impulse responses. The ranging accuracy is comparable to classical UWB ranging and thus inherently robust to multipath propagation.

A CMOS Wideband RF Front-End With Mismatch Calibrated Harmonic Rejection Mixer for Terrestrial Digital TV Tuner Applications

A wideband direct-conversion RF front-end for Advanced Television Systems Committee terrestrial digital TV (DTV) tuner applications is realized in a 0.18-μm CMOS technology. In order to effectively solve the critical local oscillator (LO) harmonic mixing problem in an ultra-wideband frequency environment of 48-860 MHz, the combination of a mismatch calibrated harmonic rejection mixer (HRM) and a simple preceding integrated third-order passive RF tracking filter with an external inductor is utilized to obtain 60-80 dB of harmonic rejection for all odd-order harmonic mixing within the DTV spectrum. In addition, an efficient novel calibration algorithm for the HRM is proposed in order to simplify the compensation process. The RF front-end also includes a broadband noise-canceling low-noise amplifier, an attenuator to cover the wide dynamic range, an LO multiphase generator, and peripheral circuits such as an I <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> C serial interface for digital control. The implemented CMOS RF front-end achieves a total gain of 40 dB, output third-order intercept point of 30 dBm, and noise figure of 5.5 dB while consuming a low power of 140 mW from a 1.8-V supply voltage.

Implementation of Passive Telemetry RF Sensor System Using Unscented Kalman Filter Algorithm

This article describes a newly designed and implemented capacitive sensor system. An Unscented Kalman Filter (UKF) algorithm based passive telemetry RF sensor system was modeled with parasitic parameters over a range of high frequencies of approximately 200 KHz. And the system was also successfully implemented on the DSP. Under the constraints that it should be “wireless,” “implantable,” and “batteryless,” the system was simply built to consisted of passive components R, L and C by the inductive coupling principle, and it focused on the accurate estimation of a capacitive parameter in the secondary part. The UKF algorithm, which can coped with the drawbacks of the extended Kalman filter in noisy nonlinear systems, was applied to estimate the capacitive parameter with nonlinearity. The input/output learning data for the UKF algorithm were acquired from the specially designed phase difference detector and amplitude detector. The newly suggested parameter estimation technique can be easily applied to the precise measurement system, which should coped with sensitive environmental changes, such as changes in pressure or humidity.

Amplitude Offset Estimation by Phase Comparison in Suppression Loops

In this paper, a new architecture for an RF amplitude comparator circuit is introduced. The technique employs a trigonometric relationship enacted by passive RF components to map the amplitude ratio between two co-spectral RF signals into a phase difference. The theory of operation of the circuit is discussed in detail and the results of a practical investigation are presented, validating the approach. The results demonstrate an accuracy advantage over commercially available products. Over the frequency range of 1600-2100 MHz, amplitude offset measurements to within 0.08 dB of that of a calibrated vector signal analyzer are shown.

DEVELOPMENT OF IMPLANTABLE FLOW-THROUGH LEFT VENTRICULAR PRESSURE TELEMETRIC TRANSMITTER FOR SMALL RODENT ANIMALS: PP.14.31

Objective: Although 24-hour arterial blood pressure can be monitored in a free-moving animal using pressure telemetric transmitter mostly from Data Science International (DSI), accurate monitoring of 24-hour mouse left ventricular pressure (LVP) is not available because of its insufficient frequency response to a high frequency signal such as the maximum derivative of mouse LVP (LVdP/dtmax and LVdP/dtmin). The aim of the study was to develop a tiny implantable flow-through LVP telemetric transmitter for small rodent animals, which can be potentially adapted for human 24 hour BP and LVP accurate monitoring. Design and Method: The mouse LVP telemetric transmitter (Diameter: ∼12 mm, ∼0.4 g) was assembled by a pressure sensor, a passive RF telemetry chip, and to a 1.2F Polyurethane (PU) catheter tip. The device was developed in two configurations and compared with existing DSI system: (a) prototype-I: a new flow-through pressure sensor with wire link and (b) prototype-II: prototype-I plus a telemetry chip and its receiver. All the devices were applied in C57BL/6J mice. Data are mean ± SEM. Results: A high frequency response (>100 Hz) PU heparin saline-filled catheter was inserted into mouse left ventricle via right carotid artery and implanted, LV systolic pressure (LVSP), LVdP/dtmax, and LVdP/dtmin were recorded on day2, 3, 4, 5, and 7 in conscious mice. The hemodynamic values were consistent and comparable (139 ± 4 mmHg, 16634 ± 319, -12283 ± 184 mmHg/s, n = 5) to one recorded by a validated Pebax03 catheter (138 ± 2mmHg, 16045 ± 443 and -12112 ± 357 mmHg/s, n = 9). Similar LV hemodynamic values were obtained with Prototype-I. The same LVP waveforms were synchronically recorded by Notocord wire and Senimed wireless software through prototype-II in anesthetized mice. Conclusion: An implantable flow-through LVP transmitter (prototype-I) is generated for LVP accurate assessment in conscious mice. The prototype-II needs a further improvement on data transmission bandwidth and signal coupling distance to its receiver for accurate monitoring of LVP in a free-moving mouse.