Showing papers on "Radio frequency published in 1997"

Electrosurgical generator and system for underwater operation

Abstract: A radio frequency generator for an electrosurgical system is provided, the system including an electrode assembly having two electrodes for use immersed in an electrically conductive fluid. The generator has control circuitry for rapidly reducing the delivered radio frequency output power by at least 50 % within at most a few cycles of the peak radio frequency output voltage reaching a predetermined threshold limit. In this way, tissue coagulation can be performed in, for example, saline without significant steam generation. The same peak voltage limitation technique is used in a tissue vaporisation or cutting mode to limit the size of the steam pocket at the electrodes and to avoid electrode burning. The generator has a push-pull output stage with a series-resonant output circuit, the output stage being driven by a radio frequency oscillator at a frequency which, in general, differs from the resonant frequency of the resonant output circuit. Power control is achieved by varying the ON-time of switching transistors forming the push-pull output pair and by altering the frequency spacing between the excitation frequency and the resonant frequency of the series-resonant output circuit. In an alternative embodiment, a bridge configuration using two push-pull pairs is used, yielding a further power control variable: the relative phase of the driving signals to the respective transistor pairs.

Compact radio frequency transmitting and receiving antenna and control device employing same

Abstract: A radio frequency antenna for use with a wall mounted transmitter and/or receiver for receiving and/or transmitting signals adapted to control a control device and/or indicate status of the control device. The antenna includes an insulating substrate sized to fit within an area defined by a faceplate sized to cover an outwardly facing opening of an electrical wallbox. Conductors are disposed on both sides of the substrate forming a capacitive component. At least one of the conductors is adapted to radiate radio frequency energy into the environment. The one conductor is electrically coupled to the other conductor, and the one conductor has a pattern such that the conductor is absent in areas so as to provide the antenna with an inductive component. The at least one conductor further provides a connection to the transmitter and/or receiver. The antenna provides an antenna near-field which is substantially at the edges of the substrate and which provides insubstantial electromagnetic field coupling to an electronic circuit disposed adjacent the antenna connected to the antenna and further provides a radiated field substantially isotropic in the antenna far-field.

Common digitizing rate for multiple air interfaces for generic cell sites in cellular radio

Abstract: A basestation transceiver simultaneously addressing multiple air interface standards with cost-effective and efficient allocation of the resources available at the transceiver. The invention significantly reduces the redundancy of the radio frequency equipment used in the transceiver by the use of a common digitizing rate selected to simultaneously accomodate all of the air interface protocols serviced.

Plasma cleaning of a CVD or etch reactor using a low or mixed frequency excitation field

Abstract: An apparatus and method for cleaning the interior of a vacuum chamber of a plasma reactor which includes introducing an etchant gas through inlet ports into the vacuum chamber and applying RF power to a RF plasma excitation apparatus so as to ignite and sustain a plasma within the chamber. The frequency of the RF signal is less than 1 MHz. Alternately, an apparatus and method for cleaning the aforementioned vacuum chamber where at least two different RF power signals can be employed. In one embodiment of this alternate method the step of applying RF power involves providing a first and second RF signal, where each signal exhibits a different frequency. The first RF signal is of a higher frequency and provided to ignite a plasma within the chamber, and thereafter terminated, whereas the second RF signal is of a lower frequency, less than 1 MHz, and provided to sustain the plasma. In another embodiment, the step of applying RF power again comprises providing separate RF signals, where each signal exhibits a different frequency. However, in this embodiment, the signals are used to generate a mixed frequency RF excitation field from the RF plasma excitation apparatus to ignite and sustain a plasma within the chamber. Here again, the first RF signal is of a higher frequency and the second RF signal is of a lower frequency, i.e. less than 1 MHz.

Temperature sensing system for use in a radio frequency environment

Abstract: The invention relates to a temperature sensing system that accurately measures temperatures of articles or areas using a contact sensor even in a high radio frequency environment. The temperature sensing system includes a sensor probe that contacts with an article or area that is to have its temperature monitored, and a control circuit to amplify signals from the sensor probe. When significant amounts of radio frequency (RF) interference are present, the temperature sensing can be provided with RF shielding, RF filtering, isolated amplifying and/or multiple stages of low pass filtering that suppress the RF interference. The temperature sensing system is particularly well suited for monitoring and measuring temperatures within semiconductor manufacturing equipment, such as etching, deposition, and other processing chambers.

Method and system providing RF distribution for fixed wireless local loop service

Abstract: A system and method is disclosed for distributing a radio frequency (RF) signal within a building structure or other structure not readily transparent to radio frequencies. The RF signal originates at a wireless local loop (WLL) base station and is intercepted by a main antenna on the building structure. The intercepted RF signal, which is contained in a RF bandwidth, is distributed throughout the building structure over a low bandwidth medium, e.g., in-building cabling, which has a transmission bandwidth below the RF bandwidth. In order to accomplish this, the system has a global reference oscillator for distributing a global reference tone of high stability to the entire system. Local oscillators controlled by this global reference tone deliver RF reference tones of high stability required for mixing the RF signal to obtain an intermediate frequency (IF) signal which is fed through the low bandwidth medium to remote sites. At the remote sites the RF signal recovered from the IF signal by mixing with the RF reference tone and re-transmitted, often to WLL communication units. When the WLL base station has a connection to the Public Switch Telephone Network (PSTN), the WLL communication units provide users with wireless telephone services.

Distribution of radio-frequency signals through low bandwidth infrastructures

Abstract: A system and method for transmitting a radio frequency (RF) signal in a RF bandwidth over a low bandwidth medium (60), e.g., in-building cabling, which has a transmission bandwidth below the RF bandwidth. The system (50) has a unit (52) for receiving the RF signal and global reference oscillator (66) for distributing a global reference tone of high stability to the entire system (50). Local oscillators (58 and 86) are controlled by adjustement signals derived from this global reference tone to deliver RF reference tones of high stability required for mixing the RF signal to obtain an intermediate frequency (IF) signal which is fed through the low bandwidth medium (60). The global reference tone is preferably delivered through the same low bandwidth medium (60) to desired locations, such as remote coverage sites in a network for cellular communications, cordless telephony, local RF communications, interactive multi-media video, and high bit-rate communications.

Method and system for radio frequency measurement and automatic frequency planning in a cellular radio system

Abstract: A mobile station operating in a digital cellular system such as GSM is ordered to perform signal strength measurements on non-BCCH carrier frequencies by including an identification of those frequencies twice in the bit map comprising the BA-list. The mobile station formats a measurement report containing signal strength measurements of both BCCH and non-BCCH carrier frequencies and send it to the network which uses the data for automatic frequency allocation within the network.

Challenges in the design of frequency synthesizers for wireless applications

Abstract: This paper describes the challenges in the design of frequency synthesizers used in wireless transceivers. Following a review of design issues and the effect of nonidealities, we present a number of synthesizer architectures along with their merits and drawbacks. We also describe the difficulties in the design of some of the building blocks and consider the role of synthesizers in emerging applications.

Radio frequency sharing methods for satellite systems

Abstract: Methods and apparatus are disclosed which allow satellites (A1-M, B1-N) in a plurality of systems (A, B) to use the same radio frequencies (f1-n) with minimal interference. A timing algorithm is used that does not allow two satellites (Ai, Bi), 'visible' at the same point on the Earth (E), to transmit on the same frequency (fi).

High efficiency power amplifier

Abstract: A high efficiency power amplifier 600 consists of a non-linear radio frequency (RF) Doherty power amplifier (67) and a linearization circuit, such as, for example, a Cartesian Feedback circuit (33), an RF feedback circuit (38), an IF feedback circuit (48), or a feedforward circuit (55). The Doherty amplification stage (67) may be implemented with a BJTs, FETs, HBTs, H-FETs, PHEMTs, or any other type power transistor technology or device.

Prediction system for RF power distribution

Abstract: A method for simulating RF energy distribution comprises obtaining a binary tree representation of a geometric environment in three-dimensions and forming a 3-D geometric database model therefrom, obtaining one or more specified receive locations within the 3-D geometric database model where RF energy distribution is desirable, simulating the propagation of an RF signal within the geometric database model, the RF signal being represented as a beam having magnitude and direction, the propagation including querying the database model to trace the beam in the geometric environment; and, determining one or more intersections of the traced beam with one or more receive locations to determine RF energy distribution at the receive locations.

Electrically tunable microwave filters

Abstract: The tunable filters of the present invention incorporate tunable dielectric materials (e.g., bulk and thin film ferroelectric and paraelectric materials) in contact with segments of resonators that are at an RF voltage maximum to alter the pass band or stop band characteristic of an RF signal outputted by the filter. The biasing circuitry in contact with the tunable dielectric material can include components for inhibiting or retarding the coupling of RF energy to the biasing circuit.

Summary of measured radiofrequency electric and magnetic fields (10 kHz to 30 GHz) in the general and work environment.

Abstract: We have plotted data from a number of studies on the range of radiofrequency (RF) field levels associated with a variety of environmental and occupational sources. Field intensity is shown in units of volts/meter (V/m) for electric field strength and amps/meter (A/m) for magnetic field strength. Duty factors, modulation frequencies, and modulation indices are also reported for some sources. This paper is organized into seven sections, each cataloging sources into appropriate RF frequency bands from very-low frequency (VLF) to super-high frequency (SHF), and covers frequencies from 10 kHz to 30 GHz. Sources included in this summary are the following: Coast Guard navigational transmitters, a Navy VLF transmitter, computer visual display terminals (VDTs), induction stoves or range tops, industrial induction and dielectric heaters, radio and television broadcast transmitters, amateur and citizens band (CB) transmitters, medical diathermy and electrosurgical units, mobile and handheld transmitters, cordless and cellular telephones, microwave ovens, microwave terrestrial relay and satellite uplinks, and police, air traffic, and aircraft onboard radars. For the sources included in this summary, the strongest fields are found near industrial induction and dielectric heaters, and close to the radiating elements or transmitter leads of high power antenna systems. Handheld transmitters can produce near fields of about 500 V/m at the antenna. Fields in the general urban environment are principally associated with radio and TV broadcast services and measure about 0.1 V/m root-mean-square (rms). Peak fields from air traffic radars sampled in one urban environment were about 10 V/m, 300 times greater than the rms value of 0.03 V/m when the duty factor associated with antenna rotation and pulsing are factored in.

RF tuning method for an RF plasma reactor using frequency servoing power, voltage, current or dI/dt control

Abstract: In an RF plasma reactor including a reactor chamber with a process gas inlet, a workpiece support, an RF signal applicator facing a portion of the interior of the chamber and an RF signal generator having a controllable RF frequency and an RF signal output coupled to an input of the RF signal applicator, the invention tunes the RF signal generator to the plasma-loaded RF signal applicator by sensing an RF parameter at the RF signal generator or at the RF signal applicator and then adjusting the frequency of the RF signal generator so as to optimize the parameter. The invention further controls the RF signal generator output magnitude (power, current or voltage) by optimizing the value of the same RF parameter or another RF parameter. The reactor preferably includes a fixed tuning circuit between the RF signal generator and the RF signal applicator.

Radio receiver and radio transmitter

Abstract: A dual mode radio frequency receiver or transmitter capable of operating in a terrestrial mode in which signals are routed over a terrestrial network, and a satellite mode in which signals are routed over a satellite network. The radio frequency receiver includes a terrestrial front-end RF stage which receives signals from a terrestrial network, a satellite front-end RF stage which receives signals from a satellite network, and a common RF stage which includes mixing circuitry for frequency down-converting the signals received from the front-end RF stages.

Digital radio frequency interference canceller

Abstract: Disclosed are radio frequency (RF) interference cancellation techniques that effectively estimate RF interference to the data signals being received using a frequency domain model, and then remove the estimated RF interference from the received data signals. Improved techniques for digitally filtering multicarrier modulation samples to reduce sidelobe interference due to the RF interference are also disclosed.

System for interfacing a communication device with a radio for hands-free operation

Abstract: An interface between a portable cellular phone and an automobile radio to allow hands-free operation of the phone is housed in a remote housing connected to a battery eliminator cigarette lighter adapter plug for simple installation into an automobile The interface converts incoming signals from the cellular phone from audio frequency to radio frequency and transmits the signals to the existing automobile radio receiver, wherein the signals are reproduced over the radio speakers The interface may also be used with a power conversion system to increase the power of the phone transmissions Further, the interface may be used with any external communication source, such as a facsimile machine or laptop computer and modem The interface is also easily adapted for use with any stand-alone audio producing devices, such as a cassette deck or compact disc player

Method and system providing increased antenna functionality in a RF distribution system

Abstract: A system and method for transmitting a radio frequency (RF) signal in a RF bandwidth over a low bandwidth medium, e.g., in-building unshielded twisted pair (UTP) cabling, which has a transmission bandwidth below the RF bandwidth. The system has a unit for receiving the RF signal and a global reference oscillator for distributing a global reference tone of high stability to the entire system. Local oscillators controlled by this global reference tone deliver RF reference tones of high stability required for mixing the RF signal to obtain an intermediate frequency (IF) signal which is fed through the low bandwidth medium to remote sites. A 10 base T cable network, often pre-existing in many building structures, provides a suitable, cost effective low bandwidth medium for such RF communication. Two of the four twisted pair cables of a UTP cable are sufficient to support bi-directional communication. The remaining twisted pair cables are used to control remote site antenna functions or support other types of communication services such as data LAN, video, wired voice, or other wireless services such as PCS or wireless LAN.

Field emission and RF breakdown in high gradient room temperature linac structures

Abstract: The purpose of this article is to serve as a tutorial review on the subject of field emission and rf breakdown in high-gradient room-temperature accelerator structures and associated devices. The need to understand and control these two phenomena has become increasingly important because of the prospect of using high-gradient structures in future linear colliders. Electron field emission creates so-called dark current which parasitically absorbs rf energy, causes radiation, backgrounds, and possibly wakefields; it seems to be the precursor of rf breakdown, possibly in combination with local outgassing and plasma formation. In turn, rf breakdown limits the operation of accelerators and can cause irreversible damage to their physical structures. Research on these topics is interesting and challenging because it involves a mixture of disciplines such as surface physics, metallurgy, fabrication technologies, microwaves, beam dynamics and plasmas. This review consists of four parts: (1) field emission under dc, enhanced and rf conditions; (2) experimental set-ups; (3) prebreakdown stage--dark current and radiation; (4) experimental observations and analysis of rf breakdown. The review ends with conclusions and an outline of work that remains to be done.

Multi-frequency radio frequency transmitter with code learning capability

Abstract: A radio frequency transmitter for use in generating coded commands learned from received coded radio frequency signals. An transceiver circuit including a switching element and a tunable filter tuning element is coupled to a programmable controller, e.g, a microprocessor. The programmable controller operates the switching element of said transceiver circuit in either a first or a second mode for receiving or transmitting coded radio frequency signals, respectively via an antenna coupled to the tuning element. The switching element is operable in the first mode to demodulate received coded radio frequency signals, and the programmable controller learns the received coded radio frequency signals and stores coded commands in memory. In the second mode of operation, an oscillator is modulated by generated coded signals from the programmable controller using the stored coded commands from memory. The generation of plural coded radio frequency commands with the single radio frequency transmitter unit facilitates the learning, responsive to a received radio frequency signal, of an additional coded radio frequency command for additional door and gate operators.

Magnetic film inductors for radio frequency applications

Abstract: Responding to the increasing demand for miniaturization and circuit integration of rf inductors we analyze various aspects of designing planar inductive circuits based on magnetic films as well as demonstrate substantially enhanced inductance characteristics for some prototype structures.

Method of making a radio frequency identification tag

Abstract: The invention is a radiofrequency identification tag comprising a semiconductor chip having radio frequency, logic, and memory circuits, and an antenna that are mounted on a substrate. The antenna may be used by the chip to modulate an incident RF signal to transfer information to a base station. The antenna comprises one or more lengths of thin wire that are connected directly to the chip by means of wire bonding. The chip and antenna combination are sealed with an organic film covering.

System method and apparatus for identifying and communicating with a plurality of types of radio frequency communication devices

Abstract: A system, method of use, and a plurality of types of Radio Frequency Transponders (RF Tags). The RF Tags carry a directory or a tag type number which determines the layout of information in the tag memory. The tag type numbers are arranged hierarchically.

All-optical RF filter using amplitude inversion in a semiconductor optical amplifier

Abstract: We present an all optical delay-line radio-frequency (RF) notch filter. The filter exploits cross-gain modulation in a homogeneously broadened laser medium to obtain a negative tap in an optically incoherent system. Applications including moving-target indication (MTI) in optically controlled radars are discussed.

Single chip RF tag oscillator circuit synchronized by base station modulation frequency

Abstract: A Radio Frequency (RF) transponder (tag), method, and system, whereby the tag has a low current tag oscillator, the oscillation frequency of the tag oscillator set by RF signal from a base station.

Optical communications system with wavelength division multiplexing

Abstract: A wavelength division multiplexer (WDM) in an optical fiber transmission system launches analog signals, for instance a multi-channel television signal. The WDM enhances signal quality by transmitting along a single fiber two different optical wavelength signals, each carrying identical RF information. This results in a 3 dB improvement in carrier to noise ratio. The WDM combines two or more wavelengths centered around for instance 1550 nm or 1310 nm. A typical difference between the two wavelengths is 3 nm. In other embodiments, more than two wavelengths are used. The receiver is for instance a single photosensitive element. The phase of the two RF signals is adjusted in the optical or RF domain to be the same upon arrival at the receiver. In other embodiments, the receiver includes two photosensitive elements, each receiving from a receiver end WDM a single wavelength. In this case, the phase adjustment may be applied at the receiver in the optical or RF domain.

System for measuring average speed and traffic volume on a roadway

Abstract: A vehicular traffic sensor capable of measuring traffic speed and volume in all weather conditions and at a low installed cost. The sensor makes use of multi-path interference of ambient radio frequency (RF) signals. The ambient RF signals can be, for example, control signals constantly transmitted by cellular telephone base stations. As vehicles travel along the roadway, they reflect RF signals in all directions. An antenna mounted near the side of the road will detect signals from the transmitter and signals reflected off the vehicle. Variations in the amplitude of the combination of the two signals can be processed using a method that allows the sensor to determine traffic speed and volume. This information can then be sent directly to a traffic management center. This provides an inexpensive sensor for wide-area traffic monitoring.

Dividable transmit antenna array for a cellular base station and associated method

Abstract: A time division multiple access base station communicates with a plurality of mobile stations in a cellular communications system using a plurality of time division multiple access (TDMA) time slots. The base station includes an antenna, a modulator, and a radio frequency switch. The antenna includes an array of transmit antenna elements. The modulator generates a first cellular radio signal for transmission during a first time division multiple access (TDMA) time slot, as well as second and third cellular radio signals for simultaneous transmission during a second time division multiple access (TDMA) time slot. In addition, the second and third cellular radio signals are generated on different frequencies. The radio frequency switch couples the first cellular radio signal to a first plurality of the transmit antenna elements during the first time division multiple access (TDMA) time slot, while coupling the second and third cellular radio signals to respective second and third pluralities of the transmit antenna elements during the second time division multiple access (TDMA) time slot.