Showing papers on "Radio frequency published in 2004"

Digital wireless position sensor

Abstract: A method is provided for tracking an object, including positioning a radio frequency (RF) driver to radiate an RF driving field toward the object, and fixing to the object a wireless transponder that includes a power coil and at least one sensor coil. The method also includes receiving the RF driving field using the power coil and storing electrical energy derived therefrom. A plurality of field generators are driven to generate electromagnetic fields at respective frequencies in a vicinity of the object that induce a voltage drop across the at least one sensor coil. A digital output signal is generated at the wireless transponder indicative of the voltage drop across the sensor coil, and the generation of the digital output signal is powered using the stored electrical energy. The digital output signal is transmitted from the wireless transponder using the power coil, and the transmission of the digital output signal is powered using the stored electrical energy. The digital output signal is received and processed to determine coordinates of the object.

Recycling ambient microwave energy with broad-band rectenna arrays

Abstract: This paper presents a study of reception and rectification of broad-band statistically time-varying low-power-density microwave radiation. The applications are in wireless powering of industrial sensors and recycling of ambient RF energy. A 64-element dual-circularly-polarized spiral rectenna array is designed and characterized over a frequency range of 2-18 GHz with single-tone and multitone incident waves. The integrated design of the antenna and rectifier, using a combination of full-wave electromagnetic field analysis and harmonic balance nonlinear circuit analysis, eliminates matching and filtering circuits, allowing for a compact element design. The rectified dc power and efficiency is characterized as a function of dc load and dc circuit topology, RF frequency, polarization, and incidence angle for power densities between 10/sup -5/-10/sup -1/ mW/cm/sup 2/. In addition, the increase in rectenna efficiency for multitone input waves is presented.

Applications of a travelling wave-based radio-frequency-only stacked ring ion guide.

Abstract: The use of radio-frequency (RF)-only ion guides for efficient transport of ions through regions of a mass spectrometer where the background gas pressure is relatively high is widespread in present instrumentation. Whilst multiple collisions between ions and the background gas can be beneficial, for example in inducing fragmentation and/or decreasing the spread in ion energies, the resultant reduction of ion axial velocity can be detrimental in modes of operation where a rapidly changing influx of ions to the gas-filled ion guide needs to be reproduced at the exit. In general, the RF-only ion guides presently in use are based on multipole rod sets. Here we report investigations into a new mode of ion propulsion within an RF ion guide based on a stack of ring electrodes. Ion propulsion is produced by superimposing a voltage pulse on the confining RF of an electrode and then moving the pulse to an adjacent electrode and so on along the guide to provide a travelling voltage wave on which the ions can surf. Through appropriate choice of the travelling wave pulse height, velocity and gas pressure it will be shown that the stacked ring ion guide with the travelling wave is effective as a collision cell in a tandem mass spectrometer where fast mass scanning or switching is required, as an ion mobility separator at pressures around 0.2 mbar, as an ion delivery device for enhancement of duty cycle on an orthogonal acceleration time-of-flight (oa-TOF) mass analyser, and as an ion fragmentation device at higher wave velocities.

Semi-passive radio frequency identification (RFID) tag with active beacon

Abstract: A radio frequency beacon device for use with a backscatter interrogator includes a processor; a receiver coupled to the processor; a backscatter modulator coupled to the processor; and an active transmitter coupled to the processor, the active transmitter being configured to transmit an RF signal, in response to a trigger signal, regardless of whether the interrogator is providing a carrier wave for backscatter modulation by the backscatter modulator. Other methods and apparatus are provided.

Toward Epoch of Reionization Measurements with Wide-Field Radio Observations

Abstract: This paper explores the potential for statistical epoch of reionization (EOR) measurements using wide-field radio observations. New developments in low-frequency radio instrumentation and signal processing allow very sensitive EOR measurements, and the analysis techniques enabled by these advances offer natural ways of separating the EOR signal from the residual foreground emission. This paper introduces the enabling technologies and proposes an analysis technique designed to make optimal use of the capabilities of next-generation low-frequency radio arrays. The observations we propose can directly observe the power spectrum of the EOR using relatively short observations and are significantly more sensitive than other techniques that have been discussed in the literature. For example, in the absence of foreground contamination the measurements we propose would produce five 3 � power spectrum points in 100 hr of observation with only 4 MHz bandwidth with LOFAR for simple models of the high-redshift 21 cm emission. The challenge of residual foreground removal may be addressed by the symmetries in the three-dimensional (two spatial frequencies and radio frequency) radio interferometric data. These symmetries naturally separate the EOR signal from most classes of residual unsubtracted foreground contamination, including all foreground continuum sources and radio line emission from the Milky Way. Subject heading gs: cosmology: observations — early universe — radio lines: general

The Design of CMOS Radio-Frequency Integrated Circuits

Abstract: The Design Of Cmos Radio Frequency Integrated Circuits Solution Manual *FREE* the design of cmos radio frequency integrated circuits solution manual 4. RESISTA N CE . RESISTORS AND RESISTOR CIRCUITS Resistance is the op position to current flow in various degrees. The practical unit of resistance is called the ohm. A resistor on one ohm is physically very large but provides only a small resistance to current flow.The Design Of Cmos Radio Frequency Integrated Circuits the design of cmos radio frequency integrated circuits solution manual The Design Of Cmos Radio Frequency Integrated Circuits Solution Manual The Design Of Cmos Radio Frequency Integrated Circuits Solution Manual FREE the design of cmos radio frequency integrated circuits solution manual 4 RESISTA N CE Read The Design Of Cmos Radio Frequency Integrated Free Download Books The Design Of Cmos Radio Frequency Integrated Circuits Solution Manual You know that reading The Design Of Cmos Radio Frequency Integrated Circuits Solution Manual is beneficial because we are able to get a lot of information in the reading materials The design of cmos radio frequency integrated circuits Download The design of cmos radio frequency integrated circuits solution manual in EPUB Format In the website you will find a large variety of ePub PDF Kindle AudioBook and books Such as manual user assist The design of cmos radio frequency integrated circuits solution manual ePub comparison suggestions and The Design Of CMOS Radio Frequency Integrated Circuits The Design of CMOS Radio Frequency Integrated Circuits Solutions Manual Solutions Manuals are available for thousands of the most popular college and high school textbooks in subjects such as Math Science Physics Chemistry Biology Engineering Mechanical Electrical Civil Business and more The Design of CMOS Radio Frequency Integrated Circuits The Design of CMOS Radio Frequency Integrated Circuits Second Edition The last chapter will provide a trip down memory lane for some readers—a sampling of circuits of particular interest in RF history including the Regency TR 1 transistor radio design and the three transistor cicuit that created the first toy walkie talkie in 1962 PDF The Design of CMOS Radio Frequency Integrated PDF Student Solutions Manual Chapters 1 11 for Stewarts Single Variable Calculus Early Transcendentals 7th By James Stewart P D F PDF The Beginning Questions to Dr Malachi Z York El About By Malachi Z York El pdf PDF The Design of CMOS Radio Frequency Integrated PDF The Design of CMOS Radio Frequency Integrated Circuits Second Edition 2 DESCRIPTION This expanded and thoroughly revised edition of Thomas H Lee s acclaimed guide to the design of gigahertz RF integrated circuits features a completely new chapter on the principles of wireless systems The Design of CMOS Radio Frequency Integrated Circuits Chapter 2 Basic MOS Device Physics In studying the design of integrated circuits one of two extreme approaches can b Design of Analog CMOS Integrated Circuits Chap 3 I X1 X2 Single Stage Amplifiers Figure 3 1 Input output characteristic of a nonlinear system The Design of CMOS Radio Frequency Integrated Circuits The Design of CMOS Radio Frequency Integrated Circuits Second Edition Thomas H Lee on Amazon com FREE shipping on qualifying offers This expanded and thoroughly revised edition of Thomas H Lee s acclaimed guide to the design of gigahertz RF integrated circuits features a completely new chapter on the principles of wireless systems The chapters on low noise amplifiers The Design of CMOS Radio Frequency Integrated Circuits by The Design of CMOS Radio Frequency

User interface and time-shifted presentation of data in a system that monitors activity in a shared radio frequency band

Abstract: An intelligent spectrum management (ISM) system and method that includes sophisticated features to detect, classify, and locate sources of RF activity. The system comprises one or more radio sensor devices positioned at various locations in a region where activity in a shared radio frequency band is occurring. A server is coupled to the radio sensor devices and aggregates the data generated by the sensor devices. Data collected and processed by the server from the sensors may be coupled to a console application that displays the data in desirable user interface format. According to one aspect, the server continuously stores spectrum analysis data pertaining to activity in a frequency band over time and/or protocol analysis data pertaining to analysis of packets transmitted in the frequency band according to a communication protocol. A console application includes a time-shift display mode that permits a user to specify an instant of time prior to the current time from which to playback spectrum analysis data and/or protocol analysis data generated by one or more radio sensor devices.

System and method for supporting multiple reader-tag configurations using multi-mode radio frequency tag

Abstract: A system, apparatus and method for supporting multiple reader-tag configurations and reader-tag distances using a single multi-mode tag. A multi-mode radio frequency (RF) transponder (300) is provided, which includes operational tag circuitry (308, 332) configured to provide information in response to being activated by a reader device(s) (118). Multiple antenna circuits (306, 330) are coupled to the operational tag circuitry (308, 332), where each of the antenna circuits (306, 330) is configured to operate at a different reader-tag distance. At least one disabling circuit (310, 344) is coupled to the operational tag circuitry (308, 332) and to at least one of the antenna circuits (306, 330), where the disabling circuit (310, 344) is configured to disable operation of at least one of the antenna circuits (306, 330) to which it is coupled.

Micromechanical mixer-filters ("mixlers")

Abstract: A device comprised of interlinked micromechanical resonators with capacitive mixer transducers has been demonstrated to perform both frequency translation (i.e., mixing) and highly selective low-loss filtering of applied electrical input signals. In particular, successful downconversion of a 200-MHz radio frequency (RF) signal down to a 37-MHz intermediate frequency (IF) and subsequent high-Q bandpass filtering at the IF are demonstrated using this single, passive, micromechanical device, all with less than 13 dB of combined mixing conversion and filter insertion loss. The mixer-filter (or "mixler") RF-to-IF voltage transfer function is shown to depend upon a ratio of local oscillator amplitude and applied bias voltages.

Dual band, low profile omnidirectional antenna

Abstract: A low-profile dual-band antenna includes a ground plane. An “E”-shaped metal plate is located a first distance from the ground plane and includes first and second outer extensions and an inner extension of the metal plate. A feed tab connects the inner extension and the ground plane. A shorting tab connects the inner extension and the ground plane. The low-profile dual-band antenna communicates first radio frequency (RF) signals in a first RF band and second RF signals in a second RF band. The first RF signals and the second RF signals are vertical polarized signals. The low-profile dual-band antenna produces a radiation pattern that is omnidirectional in the azimuth plane and vertically polarized in a horizontal plane when communicating the first RF signals and the second RF signals. The first RF band and the second RF band can be independently tuned.

Non-simultaneous frequency diversity in radio communication systems

Abstract: A radio using non-simultaneous frequency diversity includes: an antenna (502), a radio frequency module (504) coupled to the antenna (502) such that the radio frequency module (504) is operable to transmit (556) or receive (554) radio frequency signals using the antenna, and a baseband module (506) coupled to the radio frequency module. The baseband module is operable to transmit or receive signals through the radio frequency module, such that signals transmitted or received by the radio employ non-simultaneous frequency diversity. A method for transmitting information using non-simultaneous frequency diversity includes: identifying information to be transmitted, transmitting the identified information on a first channel, and after a predetermined amount of time, transmitting the identified information on a second channel. A method for receiving information transmitted using non-simultaneous frequency diversity includes receiving a first signal transmitted on a first channel; after a predetermined amount of time, receiving a second signal transmitted on a second channel; and identifying transmitted information based on the first signal and the second signal.

Radio frequency motion tracking system and method

Abstract: A radio frequency (RF) motion capture system includes stationary sensor receivers, one or more transmitter marker tags on one or more objects to be tracked within a capture zone, at least one stationary reference tag transmitter, and a processing system for processing the received signals. The individual tags transmit burst of spread-spectrum RF signals. The transmitted signals include a common sync code, and a tag identification code that is unique to each tag. By computing double differences of pseudoranges, clock terms are cancelled out allowing the processing system to precisely determine the location of each tag as it moves through the capture zone without the need to synchronize clocks between sensors and tags. The system can be used for RF match moving.

Enhancing intrusion detection in wireless networks using radio frequency fingerprinting.

Abstract: Media access control (MAC) address spoofing can result in the unauthorized use of network resources. This paper demonstrates a novel approach, which incorporates radio frequency fingerprinting (RFF) into a wireless intrusion de tection system (IDS), for detecting this attack. RFF is a technique that is used to uniquely identify a transceiver based on the transient portion of the signal it generates. Moreover, the success rate of a wireless IDS is also improved by correlating several observations in time, using a Bayesian filter. Simulation results, with an average success rate of (94-100%), support the feasibility of employing RFF and Bayesian filtering techniques to successfully address the aforementioned problem.

Method and device for frequency translation in powerline communications

Abstract: A method and apparatus for transmitting and receiving RF signals for broadband communications using power lines as communication medium. A super-heterodyne structure is used to translate the signals from one frequency to another so as to avoid interference sources, which may corrupt the communication signals. In the heterodyne structure, a plurality of local oscillators are used to mix the local oscillator signals with the communication signals for frequency translation. A plurality of frequency filters are used to filtered out unwanted signals. The communication signals are imparted onto or received from the power lines via couplers operatively connected to modems.

Broadband, ultra wideband and ultra narrowband reconfigurable interoperable systems

Abstract: Broadband, ultra wideband and ultra narrowband (UWN) reconfigurable, interoperable communication and broadcasting system architectures, combinations and hybrids of ultra wideband (UWB), ultra narrowband (UNB) and efficient broadband wireless, baseband, intermediate frequency (IF) and radio frequency (RF) implementations for Bit Rate Agile (BRA) reconfigurable and interoperable systems, Adaptive Modulation and Coding (AMC). Processing the data signals, of clock signals, and/or carrier cycles waveforms leads to shaped radio-frequency (RF) cycles, waveforms and wavelets. With Multiple Input Multiple Output (MIMO) diversity and protection system configuration the performance and capacity of these systems may be further enhanced.

NMR R1 rho rotating-frame relaxation with weak radio frequency fields.

Abstract: NMR spin relaxation in the rotating frame (R(1 rho)) is one of few methods available to characterize chemical exchange kinetic processes occurring on micros-ms time scales. R(1 rho) measurements for heteronuclei in biological macromolecules generally require decoupling of (1)H scalar coupling interactions and suppression of cross-relaxation processes. Korzhnev and co-workers demonstrated that applying conventional (1)H decoupling schemes while the heteronuclei are spin-locked by a radio frequency (rf) field results in imperfect decoupling [Korzhnev, Skrynnikov, Millet, Torchia, Kay. J. Am. Chem. Soc. 2002, 124, 10743-10753]. Experimental NMR pulse sequences were presented that provide accurate measurements of R(1 rho) rate constants for radio frequency field strengths > 1000 Hz. This paper presents new two-dimensional NMR experiments that allow the use of weak rf fields, between 150 and 1000 Hz, in R(1 rho) experiments. Fourier decomposition and average Hamiltonian theory are employed to analyze the spin-lock sequence and provide a guide for the development of improved experiments. The new pulse sequences are validated using ubiquitin and basic pancreatic trypsin inhibitor (BPTI). The use of weak spin-lock fields in R(1 rho) experiments allows the study of the chemical exchange process on a wider range of time scales, bridging the gap that currently exists between Carr-Purcell-Meiboom-Gill and conventional R(1 rho) experiments. The new experiments also extend the capability of the R(1 rho) technique to study exchange processes outside the fast exchange limit.

Wave-guide-notch antenna

Abstract: A dual polarised wave-guide notch antenna array is disclosed. The device comprises a feed section (1) having at least two input transmission lines, a feed/wave-guide interface (5) providing an aperture for transferring a radio frequency electromagnetic wave between the feed section (1) and a wave-guide mode in a wave-guide section (3) having ridges. The wave-guide section transfers energy between the feed/wave-guide interface and a tapered notch section (7), thereby gradually adjusting a created electromagnetic field towards free space conditions.

Optical fiber communications method and system without a remote electrical power supply

Abstract: The present invention allows remote antenna units for radio frequency signal transmission and receipt to operate without the requirement for remote electrical power supplies or for connecting cables that incorporate electrical conductors. According to an aspect of the present invention, an optical communications system employing radio frequency signals comprises a central unit; at least one remote unit having at least one optoelectronic transducer for converting optical data signals to radio frequency signals and converting radio signals to optical signals and at least one antenna to receive and send radio frequency signals; at least one optical fiber data link between the central unit and the remote unit for transmitting optical data signals therebetween; and at least one optical fiber power link between the central unit and the remote unit for providing electrical power at the remote unit.

Intelligent gain control in an on-frequency repeater

Abstract: An intelligent gain controller (IGC) for an on-frequency repeater includes a broadband gain controller (GC) for amplifying a broadband radio frequency (RF) signal within a broadband signal path of the repeater. A narrowband receiver isolates a narrowband signal within the broadband RF signal. A processor determines a power level of the narrowband signal, and controls the gain of the broadband GC in accordance with the determined power level.

Radio-frequency based catheter system and method for ablating biological tissues

Abstract: An improved radio-frequency based catheter system and method for ablating biological tissues within the body vessel of a patient comprises a radio-frequency ('RF') generator for selectively generating high frequency energy in a deployable catheter having a RF co-axial transmission line with a hollow lumen, a RF antenna mounted on the distal portion of the catheter, and steering control lines in the lumen of the transmission line for steering catheter while being inserted into the body vessel and for deflecting the RF antenna to accommodate the contour of the body vessel where tissue ablation is needed.

RF spectrum analysis of optical signals using nonlinear optics

Abstract: We study a technique to measure the radio-frequency (RF) spectrum of an optical signal based on nonlinear optics. The conventional approach, based on fast photodetection and analysis of the generated photocurrent via electronics means, is replaced by a nonlinear interaction of the source under test with a quasimonochromatic source followed by an optical spectrum measurement. Our technique has the advantage of an all-optical measurement that can provide a much larger bandwidth than electronic alternatives. The properties of this diagnostic, such as resolution and bandwidth, are studied. Typical applications to the monitoring of optical signals are presented.

Use of balun chokes in small-antenna radiation measurements

Abstract: Measurements of the free-space radiation characteristics of small antennas, such as in mobile communications handsets, typically suffer from the influence of the attached radio frequency (RF) feed. A sleeve-like balun choke placed on the feed cable close to the antenna under test (AUT) prevents surface currents of the AUT from propagating onto the outer shield of the RF feed cable. Therefore, measurement results with the balun correspond well to those of an isolated AUT, much better than without any measures against cable effects. The balun can typically be used at a 10% relative bandwidth. A dual-frequency balun minimizes the cable-related effects at two separate frequency bands. This is useful in the measurements of dual-frequency antennas. The results of both simulations and measurements for a dual-band balun are presented in this paper, proving the usefulness of the proposed balun and its advantages over alternative means to decrease the cable-related effects.

3-D-integrated RF and millimeter-wave functions and modules using liquid crystal polymer (LCP) system-on-package technology

Abstract: Electronics packaging evolution involves system, technology, and material considerations. In this paper, we present a novel three-dimensional (3-D) integration approach for system-on-package (SOP)-based solutions for wireless communication applications. This concept is proposed for the 3-D integration of RF and millimeter (mm) wave embedded functions in front-end modules by means of stacking substrates using liquid crystal polymer (LCP) multilayer and /spl mu/BGA technologies. Characterization and modeling of high-Q RF inductors using LCP is described. A single-input-single-output (SISO) dual-band filter operating at ISM 2.4-2.5 GHz and UNII 5.15-5.85 GHz frequency bands, two dual-polarization 2/spl times/1 antenna arrays operating at 14 and 35 GHz, and a WLAN IEEE 802.11a-compliant compact module (volume of 75/spl times/35/spl times/0.2 mm/sup 3/) have been fabricated on LCP substrate, showing the great potential of the SOP approach for 3-D-integrated RF and mm wave functions and modules.

Electron Capture Dissociation in a Radio Frequency Ion Trap

Abstract: We report on the first evidence of electron capture dissociation (ECD) in a radio frequency (rf) ion trap. Peptide ions, [substance P]2+, trapped in a two-dimensional, linear rf ion trap were cleaved by electrons injected along the central axis of the trap. Along the axis, the rf field component was zero and a magnetic field of 50 mT was applied. This electron injection scheme keeps the energy of the electrons below 1 eV, preventing them from heating by the rf field. The present ECD efficiency is approximately 4% by irradiation of electron current of 0.2 microA for 80 ms. ECD in rf traps may open high-throughput and low-cost ECD applications to obtain molecular structure information complementary to collision-induced dissociation.

Direct RF sampling mixer with recursive filtering in charge domain

Abstract: We present a direct RF sampling technique in which an input RF signal is converted to a current waveform, gated and integrated on a sampling capacitor. A rotating capacitor shares this charge with the main sampling capacitor and transfers it to a subsequent discrete-time switched-capacitor filter stage. This action creates a first order IIR filter which serves as an anti-alias filter for subsequent stages. The transfer function of this stage can be changed by adjusting the clock signal controlling the rotating capacitor. This approach has been validated and incorporated in a commercial Bluetooth receiver IC realized in a digital 130 nm CMOS that meets or exceeds performance of other conventional Bluetooth radio architectures.

Automated real-time site survey in a shared frequency band environment

Abstract: An intelligent spectrum management (ISM) system and method that includes sophisticated features to detect, classify, and locate sources of RF activity The system comprises one or more radio sensor devices positioned at various locations in a region where activity in a shared radio frequency band is occurring A server is coupled to the radio sensor devices and aggregates the data generated by the sensor devices The server receives data from each of the plurality of sensor devices and executes functions to process the data One feature of the system is to correlate data collected from the sensor or from suitably equipped devices that operate (and may move about) in a space with locations where provocation of that data occurs To this end, radio frequency energy is received at each of a plurality of known positions (eg, the sensors) in a space The positions in the space of one or more devices emitting radio frequency energy in the space is determined from the received radio frequency energy at the plurality of known positions (eg, the sensors) A variety of positioning techniques may be employed, such as received signal strength, time-difference-of arrival, time-of-arrival, etc Activity data representing characteristics of received radio frequency energy in the space is generated at the sensors or at suitable equipped devices that may move about the space The server correlates the activity data with the positions in the space that are associated with the provocation of the activity data

Radio frequency digital-to-analog converter

Abstract: Dynamic performance of high-speed high-resolution digital-to-analog converters (DACs) is limited by distortion at the data switching instants. Inter-symbol interference (ISI), imperfect timing synchronization, and clock jitter are all culprits. A DAC output controlled by an oscillating waveform is proposed to mitigate the effects of switching distortion and clock jitter. This architecture has the additional benefit of mixing the DAC impulse response energy to a higher frequency, allowing a high-frequency image of the input to be used as the output. This has the potential for better noise performance and power and hardware savings relative to a conventional DAC+mixer architecture. A narrow-band sigma-delta (/spl Sigma//spl Delta/) DAC with eight unit elements is chosen to demonstrate the radio frequency digital-to-analog converter (RF DAC) concept in a 1.8-V 0.18-/spl mu/m CMOS technology. Measured single-tone SFDR is -75 dBc, SNR is 53 dB, and two-tone IMD3 is -70.8 dBc for a 17.5-MHz band centered at 942 MHz. SNR performance is shown to have the predicted dependence on the phase alignment of the data clock and oscillating pulse.

Method for automatic control of rf level of a repeater

Abstract: A method and apparatus for controlling an output power level of a radio frequency (RF) repeater (100 or 200). A system includes a receiver to receive a signal, a filtering unit configured to pass frequency components at or around a frequency band of a predetermined communication channel, an attenuator (124 or 142) to produce an attenuated signal by attenuating a parameter of the signal, a power amplifier (150) to adjust the output power level of repeater to a desired level by adjusting the gain of one or more components of the system, and a microprocessor (170) to receive an input responsive to the output power level of the repeater and, in response to the input, to transfer control signals to the receiver and the attenuator. The method includes sampling traffic load characteristics during operation of a network and adjusting a gain of one or more components of the repeater based on the traffic load characteristics.

Electronically steerable parasitic array radiator antenna

Abstract: The electronically steerable parasitic array radiator antenna consists of one feed radiating element and parasitic radiating elements placed in the near field of the active radiator. A beam is formed due to spatial electromagnetic field coupling among radiating elements. The radiation pattern is electronically controlled by means of the variable capacitance devices (varactors) loading the parasitic elements. Unlike a conventional phased array, only one transmitter and receiver are needed for system configuration. Therefore, adaptive beamforming of low dissipation power and low fabrication cost can be achieved. On the other hand, there is only one output port to observe the signal and the weights can be controlled indirectly via reactors instead of direct control. In addition, due to interelement mutual coupling and the parasitic element being directly connected to the reactive device, the linear adaptive array theory developed to date cannot be applied straightforward. In this paper, the configuration of this antenna, its operating principle and formulation, and its measurement method, control scheme, and applications to signal processing are presented. We describe a mathematical model to simulate the radio frequency behavior of the antenna, the equivalent weight vector used for formulation of the characteristics, the admittance matrix including varactors, the effective element length, the equivalent steering vector method, the method for effectively extending the variable range of the capacitance of the varactor, the reactance circuit to cancel nonlinear distortions, the method for calibration of varactors and radiation pattern by measurement of near field of the radiating element, the learning criteria used to control radiation patterns autonomously in adaptation to the electromagnetic environment, the reactance optimization algorithm, the concept of the reactance domain signal processing and the direction of arrival estimation based on such a process, and diversity reception and spatial correlation. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(10): 25–45, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20081