RF Network Research Articles

State-space modeling of the radio frequency inductively-coupled plasma generator

Computational fluid dynamics models of RF-ICP are useful in understanding the basic transport phenomenon in an ICP torch under a wide variety of operating conditions. However, these models lack the ability to evaluate the effects of the plasma condition on the RF generator. In this paper, simulation of an induction plasma generator has been done using state space modelling by considering inductively coupled plasma as a part of RF network .The time dependent response of the RF-ICP generator circuit to given input excitation has been computed by extracting the circuit's state-space variables and their constraint matrices. MATLAB 7.1 software has been used to solve the state equations. The values of RF coil current, frequency and plasma power has been measured experimentally also at different plate bias voltage. The simulated model is able to predict RF coil current, frequency, plasma power, overall efficiency of the generator. The simulated and measured values are in agreement with each other. This model can prove useful as a design tool for the Induction plasma generator.

Cgs compensating V-band resistive mixer with low conversion loss at low LO power

A C gs compensating resistive mixer with low conversion loss at a low LO power level is proposed. In the proposed mixer with an additional transistor, C gs looking at the gate applying an LO signal is reduced by C gd , C gs , and C ds of the additional transistor. This enables the proposed resistive mixer to have low conversion loss at a low LO power level. This enables the circuit to have high LO-RF isolation and facilitates an RF and IF matching network design. The fabricated chip size using 0.13 m CMOS technology is 0.71 × 0.69 mm 2 . It achieves a conversion loss of 6.2 to 9.7 dB at an RF frequency of 56 to 63 GHz, and an input P 1dB of -2.5dBm at an LO power of 0dBm. This is believed to be the lowest conversion loss among V-band resistive mixers.

Communication coverage in wireless passive sensor networks

System lifetime of wireless sensor networks (WSN) is inversely proportional to the energy consumed by critically energy-constrained sensor nodes during RF transmission. In that regard, modulated backscattering (MB) is a promising design choice, in which sensor nodes send their data just by switching their antenna impedance and reflecting the incident signal coming from an RF source. Hence, wireless passive sensor networks (WPSN) designed to operate using MB do not have the lifetime constraints of conventional WSN. However, the communication performance of WPSN is directly related to the RF coverage provided over the field the passive sensor nodes are deployed. In this letter, RF communication coverage in WPSN is analytically investigated. The required number of RF sources to obtain interference-free communication connectivity with the WPSN nodes is determined and analyzed in terms of output power and the transmission frequency of RF sources, network size, RF source and WPSN node characteristics.

Response of RF Networks to Transient Waveforms: Interference in Frequency-Hopped Communications

The long-tail transient responses of a bandpass network to pulsed and switched-tone stimuli are examined and a time-domain closed-form expression of the envelope response is developed. It is shown that the long-tail response leads to interference in frequency-hopping communication systems. Interference, and in particular co-site interference, can result in any radar, communication, or RF sensor system becoming exposed to unintentional pulsed RF signals. In the experimental study, 900-MHz Chebyshev bandpass filters are considered.

Some Design Issues in Infrared Wireless Networks

In this paper, some issues involved in the design of optical wireless networks are highlighted. Merits and demerits of such networks over the RF networks are given. Sources of noise in indoor optical wireless networks, transmission techniques and modulation schemes used in these networks are discussed.

Assessment of the performance characteristics of a prototype 12-element capacitive contact flexible microstrip applicator (CFMA-12) for superficial hyperthermia

The electrical performance of the CFMA-12 operating at 433 MHz is assessed under laboratory conditions using a RF network analyser. From measurements of the scattering parameters of the CFMA-12 on both a multi-layered muscle- and fat/muscle-equivalent phantom, the optimal water bolus thickness, at which the transfer of the energy to the phantom configuration is maximal, is determined to be ∼1 cm. The SAR distribution of the CFMA-12 in a multi-layered muscle-equivalent phantom is characterized using Schottky diode sheets and a TVS-600 IR camera. From the SAR measurements using the Schottky diode sheets it is shown that the contribution of the Ex component to the SAR (SARx) is maximal 7% of the contribution of the Eycomponent to the SAR (SARy) at different layers in both phantom configurations. The complete SAR distribution (SARtot) at different depths is measured using the power pulse technique. From these measurements, it can be seen that SARyat a depth of 0 cm in the muscle-equivalent phantom represents up to 80% of SARtot. At 1 and 2 cm depth, SARy is up to 95% of SARtot. Therefore, in homogeneous muscle-equivalent phantoms, Ey is the largest E-field component and measurement of SARy distribution is sufficient to characterize SAR-steering performance of the CFMA-12. SAR steering measurements at 1 cm depth in the muscle-equivalent phantom show that the SAR maximum varies by 40% (1 SD) around the average value of 38.8 W kg−1 (range 10–65 W kg−1) between single antenna elements. The effective fieldsize (E50) varies by 14% (1 SD) around the average value of 19.1 cm2.

Scalability of mobile, base‐station‐oriented RF networks

AbstractThe performance and scalability of mobile, base‐station‐oriented wireless networks with respect to routing and mobility models is addressed in this paper. Using systems‐oriented, large‐scale discrete event simulation, both performance scalability and complexity scalability are analyzed. Performance scalability addresses the effect of network size on system performance. Complexity scalability, in this case, consists of communication complexity (i.e. amount of control information exchanged to create and maintain network connectivity). Results confirmed the scalability of base‐station‐oriented networks using the routing, and mobility models, using over 2000 fully dynamic hosts and routers. Copyright © 2004 John Wiley & Sons, Ltd.

High power 121.6 nm radiation source

A high power 121.6 nm radiation source based on dielectric barrier discharge (DBD) has been developed. Lamp parameters such as gas pressure, discharge tube diameter, electrode area and gap were optimized to maximize the 121.6 nm radiation power. Higher rf power was coupled to discharge by applying a flexible rf network, which matched the impedance between the source and discharge. The discharge was optimized by simulation using XOOPIC software to model the lamp. The simulation results were in agreement with our experimental measurements. The stable, high power (8 W) radiation source was achieved and it could be used as a reliable source for lithography and other applications.

RF and microwave network characterization-a concept-map-based tutorial

Characterization of RF and microwave networks based on scattering parameters formalism is one of the most basic themes that microwave engineers need to fully comprehend. This topic is included in most of the common textbooks on microwave circuits. However, alternative tutorial presentations that help in clearer understanding of the topic are always welcome. This tutorial is such an attempt and makes use of the concept-maps and concept-modules approach discussed in another paper in this TRANSACTIONS . Concept maps are visual representations of relationship among various concepts relevant to topic and contribute to better understanding of concepts. In addition to S-parameters, this tutorial includes A-, Z-, and Y-parameters and their relevance to microwave network representation and design.

High-speed integrated transceivers for optical wireless

Optical wireless LANs have the potential to provide bandwidths far in excess of those available with current or planned RF networks. There are several approaches to implementing optical wireless systems, but these usually involve the integration of optical, optoelectronic, and electrical components in order to create transceivers. Such systems are necessarily complex, and the widespread use of optical wireless is likely to be dependent on the ability to fabricate the required transceiver components at low cost. A number of UK universities are currently involved in a project to demonstrate integrated optical wireless subsystems that can provide line-of-sight in-building communications at 155 Mb/s and above. The system uses two-dimensional arrays of novel microcavity LED emitters and arrays of detectors integrated with custom CMOS integrated circuits to implement tracking transceiver components. In this article we set out the basic approaches that can be used for in-building optical wireless communication and argue the need for an integrated and scalable approach to the fabrication of transceivers. Our work aimed at implementing these components, including experimental results and potential future directions, is then discussed.

DC SQUID series array amplifiers with 120 MHz bandwidth (corrected)

We report on the performance of dc SQUID (Superconducting Quantum Interference Device) series array amplifiers from dc to 500 MHz. The arrays consist of up to 100 dc SQUIDs, with varying degrees of intracoil damping; the flux focusing washer of each SQUID is electrically isolated from the SQUID loop (L/sub sq/=18 pH). Using an rf network analyzer, we have observed high-frequency resonances in the response at bias points corresponding to distortions in the dc transfer functions. Increasing distance between SQUIDs in the array reduces the distortions. Distortions are also more pronounced, and bandwidth reduced, in devices incorporating the flux-focusing washer into the SQUID body. With intracoil damping of 0.25 /spl Omega/ per turn on the input coil, the voltage-flux transfer characteristics of the isolated-washer design and 300 pm center-to-center SQUID spacing are free of significant distortions, and the bandwidth is not degraded compared to undamped devices. The 100-SQUID array has 150 nH input inductance, 500 V/A transimpedance, 2.5 pA//spl radic/Hz equivalent input current noise at 4 K, and 120 MHz bandwidth.

Monitoring Robot Development with Quadruped Mechanism

A quadruped robot introduced here plays a role in monitoring some place where an operator can not reach or when he may not keep watching. It has several features that travels and poses variable position by a four wheels and quadruped typed arms, transmits an image and command data via RF wireless and network communication. The robot can balance itself when it moves up and down on slope by using the quadruped mechanism. Also, the quadruped type is dedicated to adjusting camera position, thus enables to trace the particular position. By a slight modification of the robot mechanism, the robot can be adapted to general purposes such as home cleaning and remotely controlled home appliances.

Recent developments in lightwave network analysis

The widespread use of photonic systems having microwave modulation bandwidths, coupled with the inclusion of photonic components in microwave and millimetre-wave systems, is creating a demand for efficient characterisation techniques. In particular, new tools will be required for the measurement of fundamental quantities such as the microwave frequency response, bandwidth, gain and return loss of microwave photonic components. However, existing lightwave measurement techniques are primitive when compared with conventional RF and microwave network analysis. This paper provides a review of the theory and techniques used for the small-signal characterisation of microwave photonic components. State-of-the-art architectures for lightwave network analysers and the corresponding two-port calibration techniques are described.

DC SQUID series array amplifiers with 120 MHz bandwidth

We report on the performance of dc SQUID (Superconducting Quantum Interference Device) series array amplifiers from dc to 500 MHz. The arrays consist of up to 100 dc SQUIDs, with varying degrees of intracoil damping; the flux focusing washer of each SQUID is electrically isolated from the SQUID loop (L/sub sq/=18 pH). Using an rf network analyzer, we have observed high-frequency resonances in the response at bias points corresponding to distortions in the dc transfer functions. Increasing distance between SQUIDs in the array reduces the distortions. Distortions are also more pronounced, and bandwidth reduced, in devices incorporating the flux-focusing washer into the SQUID body. With intracoil damping of 0.25 /spl Omega/ per turn on the input coil, the voltage-flux transfer characteristics of the isolated-washer design and 300 /spl mu/m center-to-center SQUID spacing are free of significant distortions, and the bandwidth is not degraded compared to undamped devices. The 100-SQUID array has 150 nH input inductance, 500 V/A transimpedance, 2.5 pA/ Hz equivalent input current noise at 4 K, and 120 MHz bandwidth.

Recent developments in lightwave network analysis

The widespread use of photonic systems having microwave modulation bandwidths, coupled with the inclusion of photonic components in microwave and millimetre-wave systems, is creating a demand for efficient characterization techniques. In particular, new tools will be required for the measurement of fundamental quantities such as the microwave frequency response, bandwidth, gain and return loss of microwave photonic components. However, existing lightwave measurement techniques are primitive when compared with conventional RF and microwave network analysis. This paper provides a review of the theory and techniques used for the small-signal characterization of microwave photonic components. State-of-the-art architectures for lightwave network analysers and the two-port calibration techniques are described.

Transparent, dynamically configurable RF network suitable for home automation applications

The design and implementation of a mobile low power RF network appliance to connect mobile intelligent nodes in one communication system. Its applicability can be found in a wide range of domains such as home automation, low speed Internet networking, data logging applications, surveillance equipment and many others. The system features self-configuring point to point routing making it particularly useful for home automation applications.

Supporting collaborative field operations with personal information processing systems

This paper describes a two-year research project to develop a personal information processing system (PIPS) solution for the roving industrial field operator. Our PIPS system comprises (1) an RF network to deliver wireless digital information, (2) a wearable computer for delivering web-based information (the hardware is a two-piece system composed of a belt-worn NetPC attached via a curly cable to a handheld unit with a mouse/display device combination), and (3) software applications that provide added value in the field. Unique challenges in designing such a system for this environment include providing: (1) good RF coverage in an environment with many metal structures; (2) an intrinsically safe, lightweight, low-cost hardware system; and (3) software that is compatible with the wearable system and supports collaboration in the field.

Proton-decoupled 19F spectroscopy of 5-FU catabolites in human liver.

An RF network and a dual-tuned surface coil are described for obtaining proton-decoupled, NOE enhanced 19F spectra from a whole body clinical imager operating at 1.5 Tesia. The network removes 19F frequency noise from the decoupler transmitter, and prevents preamplifier saturation from high-level decoupling signals. Proton decoupling of 19F spectra was optimized using a sample of urine containing 5-fluorouracil (5-FU) and its catabolite fluoro-beta-alanine (FBAL). Proton-decoupled 19F spectroscopy in vivo is demonstrated by obtaining both nonlocalized spectra and spectra localized with three-dimensional chemical shift imaging from the liver of patients undergoing 5-FU chemotherapy.

Ultrahigh-bandwidth vector network analyzer based on external electro-optic sampling

We report the development of an ultrahigh-bandwidth vector network analyzer useful for small-signal characterization of high-speed semiconductor devices. It employs 100-fs optical pulses for making terahertz-bandwidth electro-optic measurements of electrical signals, as well as for sub-picosecond, photoconductive, electrical-stimulus-signal generation. High-bandwidth coplanar strip transmission lines are used for signal transmission. A 0.15 × 50 μm gate AlGaAs/InGaAs/GaAs HFET has been characterized over a bandwidth of 100 GHz using this network analyzer. A comparison with conventional RF network analyzer measurements performed to 40 GHz demonstrated good agreement throughout this bandwidth. Such measurements of the actual device characteristics across their entire operating frequency range should improve device development and incorporation into active circuits.

A high-performance, miniaturized X-band active mixer for DBS receiver application with on-chip IF noise filter

A GaAs monolithic microwave integrated circuit (MMIC) dual-gate FET active mixer at X-band is described that is designed for direct broadcast satellite (DBS) applications. All of the components of the mixer, including biasing circuitry, RF, LO, and IF matching networks, as well as the IF noise filter, are implemented monolithically into a 25-mil*30-mil area. The design was process tolerant, and layout was compact for manufacturability and low cost. The mixer was integrated monolithically into a complete single-chip DBS low-noise block (LNB) converter. The active mixer has a conversion gain of 5.5 dB and a single-sideband noise figure of 8.5 dB. The circuit is manufactured using a 0.5- mu m gate length, buried p/sup -/ depletion mode MESFET process without substrate-through via holes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>