Showing papers on "Radio frequency published in 1996"

Review and Assessment of Radio-frequency and Microwave Energy for Stored-grain Insect Control

Abstract: Fundamental principles of radio-frequency (RF) and microwave dielectric heating are presented, with a basic consideration of differential or selective absorption of energy from RF and microwave fields that might be applicable for stored-grain insect control. Experimental findings of the past 50 years are reviewed, with respect to entomological and physical factors affecting the response of insects exposed to RF and microwave electromagnetic fields in grain and grain products. Practical aspects of RF and microwave energy application for stored-grain insect control are considered, and it is concluded that such use is highly unlikely without some new discovery of a nonthermal lethal mechanism that might be exploited for this purpose.

Radio frequency energy management system

Abstract: A radio frequency energy management system includes a number of battery control modules (18) and a control unit (22), each configured to transmit and receive radio frequency signals comprising information relating to the operating parameters of batteries in a battery pack (10), and control commands for regulating the operating parameters of such batteries (10). Each battery control module (18) is configured to monitor one or more operating parameters of a respective battery (10) and to regulate one or more operating parameters according to a control system program in the control unit (22). Each battery control module (18) includes one or more sensing elements to measure one or more operating parameters of a respective battery (10), a radio frequency receiver, and a radio frequency transmitter.

Apparatus, system and method for delivering radio frequency energy to a treatment site

Abstract: Described are apparatus, systems, and methods for delivering RF energy to a treatment site. The therapeutic system includes an RF power supply (32), and an RF therapeutic probe (17). The probe (17) includes at least one distal electrode (20) and a proximal power supply connector (25). A control circuit (42) is provided for controlling the amount of RF power supplied to the electrode (20). The control circuit (42) is formed upon connection of the connector (25) to the power supply (32).

On the E - H mode transition in RF inductive discharges

Abstract: In inductively coupled radio frequency (RF) plasmas a mode transition between a low-power mode with dominant capacitive coupling (E-mode) and a high-power mode with dominant inductive coupling (H-mode) has been frequently reported in the literature We investigate this transition, which results in an increase of the light emission by up to two orders of magnitude Furthermore we observe a hysteresis of this mode transition Two major aspects of the transition are addressed in this paper First we propose an explanation for the discontinuous character of the mode transition The analysis is based on a simple, electrodynamic model of the inductive discharge This analysis shows that a certain minimum maintenance RF coil current is required for the operation of an inductive discharge and that the skin effect of the RF field is essential for stable discharge operation This point is supported by experimental observations In the second part of the paper we present a simple, self-consistent analytic description of the discharge, which enables us to calculate the minimum maintenance RF coil current The theoretical results are found to be in reasonable agreement with the measured minimum maintenance coil currents

Method of magnetic resonance imaging and spectroscopic analysis and associated apparatus employing a loopless antenna

Abstract: The invention provides a method for magnetic resonance imaging and spectroscopic analysis of a specimen which includes positioning the specimen within a main magnetic field and introducing an antenna having a loopless antenna portion in close proximity to the specimen. Radio frequency pulses are provided to the region of interest to excite magnetic resonance signals, gradient magnetic pulses are applied to the region of interest with the antenna receiving magnetic resonance signals and emitting responsive output signals. A processor processes the responsive output signals to provide image information for display in a desired manner. The method in a preferred form involves employing a flexible antenna. The method in another preferred form involves employing an impedance matching circuit electrically interposed between the loopless antenna and the processor to enhance radio frequency power transfer and magnetic resonance signal-to-noise ratio from the loopless antenna to the processor. The method may be used on a wide variety of specimens and in a preferred use is introduced into small blood vessels of a patient to facilitate determination of atherosclerotic plaque. Medical intervention procedures, such as plaque removal, may be employed generally simultaneously with the imaging of the present invention. Corresponding apparatus and magnetic resonance antenna assembly are provided.

Dual band mobile station employing cross-connected transmitter and receiver circuits

Abstract: A multi-mode radiotelephone (10) includes at least one antenna (12) for transmitting and receiving RF signals within at least two frequency bands. The radiotelephone also includes a first receiver (30, 34) having an input coupled to the antenna for amplifying and down-converting RF signals within a first frequency band and a second receiver (30a, 34a) having an input coupled to the antenna for amplifying and down-converting RF signals within a second frequency band. The radiotelephone further includes a first transmitter (44, 46, 48) having an output coupled to the antenna for up-converting and amplifying RF signals within the first frequency band and a second transmitter (44a, 46a, 48a) having an output coupled to the antenna for up-converting and amplifying RF signals within the second frequency band. In accordance with this invention the first receiver and the second transmitter are disposed within a first circuit package (29a), and the second receiver and the first transmitter are disposed within a second circuit package (29b). The first and second circuit packages may be integrated circuits or hybrid (e.g., thick or thin film) circuits.

Radio frequency electromagnetic exposure: tutorial review on experimental dosimetry

Abstract: Radio frequency (RF) dosimetry is the quantification of the magnitude and distribution of absorbed electromagnetic energy within biological objects that are exposed to RF fields. At RF, the dosimetric quantity, which is called the specific absorption rate (SAR), is defined as the rate at which energy is absorbed per unit mass. The SAR is determined not only by the incident electromagnetic waves but also by the electrical and geometric characteristics of the irradiated subject and nearby objects. It is related to the internal electric field strength (E) as well as to the electric conductivity and the density of tissues; therefore, it is a suitable dosimetric parameter, even when a mechanism is determined to be "athermal." SAR distributions are usually determined from measurements in human models, in animal tissues, or from calculations. This tutorial describes experimental techniques that are used commonly to determine SAR distributions along with the SAR limitations and unresolved problems. The methods discussed to obtain point, planar, or whole-body averaged SARs include the use of small E-field probes or measurement of initial rate of temperature rise in an irradiated object.

Radio frequency tag

Abstract: Disclosed is a radio frequency identification (FR ID) tag (20) which is adapted for use in identifying electronic and/or electrical systems which incorporate electronic components mounted on a printed circuit board (40) (PCB). The RF ID tag comprises semiconductor circuitry contained within an electronic package, which package is mounted onto the PCB. In addition to the various components and circuitry of the tagged system, the PCB includes the RF antenna (30) portion of the tag defined either in or on the PCB. The package is connected to the antenna via pads (32) on the PCB.

Radio transmitter and method of controlling transmission by radio transmitter

Abstract: APC circuitry used for a radio transmitter comprises a detector (7) which detects a radio frequency (RF) output signal (5) to output a detection signal (8), an integrator (15) which integrates the detection signal (8) to output a power signal (16) representing the average power level of the RF output signal (5), a control unit (18) for calculating an error level from the difference between the average power level and a reference power level which corresponds to a predetermined power of the RF output signal (5), and for multiplying the error level by a correction coefficient so as to calculate a control signal correction value for correcting the value of a control signal (14) and then generate control data the digital value of which is corrected according to the control signal correction value and a reference control value that is predetermined so as to generate the RF output signal (5) having the predetermined power.

Differential ranging for a frequency-hopped remote position determination system

Abstract: A differential ranging location system is described which uses a modified time-of-arrival technique to determine the location of a frequency-hopped spread spectrum radio signal. The transmitter simultaneously transmits two radio frequency carriers having different frequencies such that a phase difference is observed between the two carriers at a distance from the transmitter. The phase difference is proportional to the range from the transmitter that the carrier signals have observed. The two carrier signals from the single transmitter are received by at least three and in special cases four base stations which calculate the differential time of arrival based on the phase differences of the received carriers. The calculated phase differences are then sent to a central location which locates the position of the transmitter based upon a planer hyperbolic location algorithm. Since a large number of narrow band frequencies across a wide spectrum are used in a frequency hopping transmission protocol, the accuracy in determining the phase differences between the two carriers is increased and the immunity to interference is also increased.

A 900-MHz RF front-end with integrated discrete-time filtering

Abstract: Discrete-time analog filters, rather than off-chip components, have been used to perform frequency selection and down conversion in the integrated front-end for a 900-MHz RF receiver. The first stage of frequency down conversion is implemented with a subsampling switched-capacitor sample-and-hold circuit clocked at 78 MHz. Subsequent stages of discrete-time filtering are realized using switched-capacitor biquadratic filters. An experimental prototype of the front-end had been integrated in a 0.6-/spl mu/m BiCMOS technology. The circuit provides a system gain of 36 dB and 32 dB suppression of interfering channels over a 40 MHz bandwidth. Referred to the system input, the third-order intercept-point is -16 dBm, and the spot input-referred noise is -82 dBm over a 30 kHz bandwidth. The experimental circuit dissipates 90 mW from a 3.3-V supply and occupies an active area of 1.9/spl times/1.9 mm/sup 2/.

Methods and apparatus for measuring temperatures at high potential

Abstract: A thermocouple is provided which measures the temperatures of structures at high RF potential, such as an RF electrode within a plasma CVD or plasma etch reactor. The thermocouple includes an outer conductive sheath that connects to the RF electrode at a first location, and a wire pair, connected to a second location of the RF electrode, that is used to sense the RF electrode temperature. The sheath--or a conductive member connected in circuit with the sheath--is wound into a coil to form an inductor with an impedance much greater than the impedance of the RF electrode. A large capacitor grounds the coil so that the thermocouple wires, extending through the sheath, and through and out of the coil, are available for diagnostic purposes. While RF current flows through the sheath, the wires experience the same magnetic field generated by the inductive coil, substantially grounding the thermocouple. Preferably, signal conditioning electronics remove any remaining DC bias voltages. In the case of a reactor for plasma CVD or etch, the thermocouple can be enclosed within a vacuum-sealed RF feedthrough that conducts the RF energy to the electrode.

A terminal to be coupled to a telecommuncations network using radio communication

Abstract: The present invention relates to a terminal to be coupled to a telecommunications network using radio communication, which consists of a computer (100) and a radio module (200) to be coupled thereto. The radio module is connected to the computer using a digital bus coupling, for example a PCMCIA bus. This terminal can be connected to a telecommunications network using radio communication, for example, the GSM system. It is essential to the invention that the operations required in the transmission and reception of a message and their performance have been divided between the computer and the radio module. Two alternative embodiments are presented. In the first embodiment, the radio module contains ancillary processors (213, 214) to achieve a sufficient calculation capacity; in the second embodiment, the computer's processor (110) performs the main part of the required processing. The necessary radio frequency elements (230) are located in the radio module.

Multi-Loop opto-electronic microwave oscillator with a wide tuning range

Abstract: A versatile photonic radio frequency (RF) oscillator employs multiple feedback loops of different delay times, including at least one optical feedback loop, to generate RF signals with ultra low phase noise, narrow spectral linewidth, and a continuous wide tuning range of high resolution. Specifically, an electro-optical modulator and a long optical fiber loop are implemented in one dual-loop system. In addition, a light beam from a light source can be directly modulated by using feedback signals from multi feedback loops to alter the electrical control signal to the light source. Furthermore, the disclosed system supports both electrical and optical RF outputs. External optical injection and electrical injection can be implemented.

Strain imaging using combined RF and envelope autocorrelation processing

Abstract: Considering that large displacements are desired for elasticity imaging to improve the strain signal to noise ratio, the authors have developed a method for strain imaging that is both fast to calculate and applicable to the measurement of large displacements. The method has the merits of phase domain processing but without aliasing, since it combines the result of phase correlation with that of envelope correlation both of which are calculated directly from the radio frequency (RF) signal using complex autocorrelation processing. Results from experiments using a computer simulation indicate that the method is capable of reliably estimating tissue displacement and strain over a large range of displacements beyond the Doppler aliasing limit with no prior knowledge of expected displacement.

Multi-channel transceiver having an adaptive antenna array and method

Abstract: A receiver (100), transmitter (200) and transceiver (400) in accordance with the present invention overcome the disadvantages of applying adaptive antenna array technology to multi-channel communication systems. Multi-channel radio frequency (RF) signals received via an adaptive antenna array (102) are converted from an analog form to a digital form prior to splitting and processing to recover communication channels contained therein. A number of digital communication signals are digitally combined into a multi-channel digital signal and converted from the digital form to an analog radio frequency form prior to transmission from the adaptive antenna array.

A direct-conversion receiver for 900 MHz (ISM band) spread-spectrum digital cordless telephone

Abstract: Direct conversion (or zero intermediate-frequency) is an attractive architecture in radio design because it eliminates expensive filters at both radio frequencies (RF) (for image rejection) and intermediate frequencies (IF). Instead, an inexpensive low-pass filter is used for channel selection, and no image rejection is required. A digital code that has negligible energy below 30 kHz is used, so that a combination of ac coupling and dc servo feedback prevents propagation of dc offsets in the IF chain. A class AB servo stage reduces the turn-on time of the receiver to 200 /spl mu/s, so it may be used in a time-division duplex (TDD) system. The typical phase accuracy of the I/Q output is one degree. The IC is designed for use in the 902-928 MHz industrial-scientific-medical (ISM) Band. It operates on a supply voltage of 2.7-5.0 V and draws 50 mA. It uses a 25 GHz f/sub T/ silicon-bipolar process.

Radio-frequency accelerating system and ring type accelerator provided with the same

Abstract: In a radio-frequency accelerating system, a loop antenna is coupled with at least one of a plurality of magnetic core groups each including a plurality of magnetic cores or with at least one of the plurality of magnetic cores, and an impedance adjusting means is connected to the loop antenna. A relatively low voltage is applied to the impedance adjusting means. Therefore, the impedance adjusting means may be a circuit element having a low withstand voltage and hence the radio-frequency accelerating system can be formed to have a small construction.

Fast scan trainable transmitter

Abstract: A trainable transmitter for learning the characteristics of a received RF signal and for transmitting a coded RF signal having the learned characteristics to a receiver for remote activation of a device, such as a garage door opener. The trainable transmitter includes a tunable RF circuit and a controller coupled to the RF circuit for selectively tuning the RF circuit during a training sequence. To provide a user with an early indication that a valid RF signal is being received at the initiation of the training sequence, the control circuit quickly sweeps the frequency at which the RF circuit is tuned from the lowest frequency to the highest frequency of a frequency range in which the carrier frequency of a valid RF signal would fall. If a signal is not detected during this initial fast scanning procedure, the training sequence is terminated and the user is so informed.

High selectivity plasma etching of silicon dioxide with a dual frequency 27/2 MHz capacitive radio frequency discharge

Abstract: A 27 MHz/2 MHz Ar/CO/CFx rf capacitive discharge was used to selectively etch submicron SiO2/Si, SiO2/TiSi2 and SiO2/TiN structures. The borophosphosilicate glass etch rate (∼1.0 μm/min) was observed to decrease with bottom electrode temperature, whereas etch selectivity to TiSi2 (≳50:1) was found to increase with temperature, with a photoresist selectivity ≳50:1. Plasma emission of the dual frequency discharge indicated the presence of an abundant concentration of the CF2 radical (249 nm) as compared to a lower frequency (400 kHz) rf discharge with low etch selectivity (<20:1). Langmuir probe measurement indicated an enhancement of ion density of an order of magnitude (∼5×1010 cm−3) as compared to the low frequency (400 kHz) rf discharge. Particle‐in‐cell simulation was used to calculate plasma density as a function of excitation frequency. Plasma density scales with the square of the source frequency while it remains relatively independent of the substrate frequency.

Method for adaptively adjusting weighting coefficients in a cDMA radio receiver

Abstract: A method (300) for adaptively adjusting weighting coefficients (188, 190, 192) in a code division multiple access (CDMA) radio receiver (100). A representation (172) of a desired RF signal (166) is received (108, 124, 127). A plurality of pilot signals (178, 182, 186) are generated responsive to the representation (172) of a desired RF signal (166). Each of a plurality of weighting coefficients (188, 190, 192) is determined responsive to more than one of the plurality of pilot signals (178, 182, 186).

Predictions of ion energy distributions and radical fluxes in radio frequency biased inductively coupled plasma etching reactors

Abstract: Inductively coupled plasma (ICP) reactors are being developed for low gas pressure (<10s mTorr) and high plasma density ([e]≳1011 cm−3) microelectronics fabrication. In these reactors, the plasma is generated by the inductively coupled electric field while an additional radio frequency (rf) bias is applied to the substrate. One of the goals of these systems is to independently control the magnitude of the ion flux by the inductively coupled power deposition, and the acceleration of ions into the substrate by the rf bias. In high plasma density reactors the width of the sheath above the wafer may be sufficiently thin that ions are able to traverse it in approximately 1 rf cycle, even at 13.56 MHz. As a consequence, the ion energy distribution (IED) may have a shape typically associated with lower frequency operation in conventional reactive ion etching tools. In this paper, we present results from a computer model for the IED incident on the wafer in ICP etching reactors. We find that in the parameter spac...

Dual mode transceiver

Abstract: A dual mode transceiver architecture suitable for adaptation in either a handset or a base station and capable of operating in both Frequency Division Duplex (FDD) mode or in Time Division Duplexing (TDD) mode is disclosed. Such a transceiver has an up conversion path capable of up converting an Intermediate Frequency (IF) to a Radio Frequency (RF) signal in either an upper band frequency range or a lower band frequency range. Also the transceiver has a down conversion path, used for receiving, for down converting a RF signal in either the upper band or lower band to a desirable IF frequency. The transceiver includes a switch array capable of switching the up conversion path to either the upper band port or the lower band port of a diplexer and the switch array also switches the upper band port and lower band port of the diplexer to the down conversion path depending on whether the transceiver is operating in TDD mode or FDD mode. Also, if in TDD mode, the switch array determines whether the transceiver is transmitting or receiving.

Radio frequency security system with direction and distance locator

Abstract: The radio frequency (RF) security system includes a central control unit and a plurality of portable transmitters (up to 128 transmitters) which are in radio frequency communication with the central control unit This communication is one-way from the portable transmitters to the central control unit The central control unit and the portable transmitters both include microprocessors and associated memory Each portable transmitter is assigned a unique unit binary code In order to detect destruction of the transmitter unit, a powerline is imbedded in an elongated band which is placed on the wrist of a child or attached to an inanimate object When the band is severed, the powerline is severed and the microprocessor in the portable transmitter is shut down During normal operation (without the band being severed), the portable transmitter has an RF transmitting circuit which is fed the unique unit code and which frequency modulates (FM) the RF carrier signal with the unit code The resulting FM signal is transmitted to the central control unit When power is severed to the microprocessor, the RF transmitter in the portable transmitter continuous emitting an RF carrier signal The central control unit, in addition to the microprocessor and memory, includes a keypad input device, an antenna system, an RF directional detection circuit, a threshold detection circuit, an identification circuit, distance measuring circuit, and several displays One display shows the orientation or bearing as well as the distance between the central control unit and each portable transmitter unit This is accomplished by the directional detection circuit generating phase differential signals which are analyzed by the microprocessor in order to determine the relative position and a distance measuring circuit which determines distance by the relative strength of the received RF signal The threshold detection circuit determines when the received RF signal fails below a certain threshold At that time, the threshold detection circuit issues an alarm which stops the scan cycle of the microprocessor Upon issuance of an alarm, the unique unit code is displayed to the operator so that the operator can easily determine which transmitter has been severed or which transmitter has left the security region (approximately 1,000 feet)

CHESS a new reliable high speed HF radio

Abstract: This paper presents the design and performance of an advanced digital signal processing (DSP) based high frequency (HF) radio developed (patent pending) by Sanders, a Lockheed Martin Company. The radio is called Correlated Hopping Enhanced Spread Spectrum (CHESS). CHESS represents a new generation of spread spectrum HF radio technology, designed to enhance spectrum sharing while providing reliable HF communications at high data rates (4800-19200 bps). The Defense Information Systems Agency (DISA) determined that CHESS does not interfere with conventional HF signals. By employing the technique of correlated fast frequency hopping, CHESS achieves desirable performance features of non-interfering spread spectrum operation, spectral re-use, multipath fading mitigation, and interference resistance.

Sheath impedance effects in very high frequency plasma experiments

Abstract: The frequency dependence (13.56–70 MHz) of the ion energy distribution at the ground electrode was measured by mass spectrometry in a symmetrical capacitive argon discharge. Reduced sheath impedance at very high frequency allows high levels of plasma power and substrate ion flux while maintaining low levels of ion energy and electrode voltage. The lower limit of ion bombardment energy is fixed by the sheath floating potential at high frequency, in contrast to low frequencies where only the radio frequency voltage amplitude is a determinant. The capacitive sheaths are thinner at high frequencies which accentuates the high frequency reduction in sheath impedance. It is argued that the frequency dependence of sheath impedance is responsible for the principal characteristics of very high frequency plasmas. The measurements are summarized by simple physical descriptions and compared with a particle‐in‐cell simulation.

Method for Controlling a Diversity Receiver Apparatus in a Radio Subscriber Unit

Abstract: A radio subscriber unit (102) has a diversity receiver apparatus (106) including a first antenna (114) and a second antenna (116). A first representation (158) and a second representation (160) of a composite radio frequency (RF) signal are received from the first antenna (114) and the second antenna (116), respectively. The composite radio frequency (RF) signal includes a desired RF signal (156) and interfering signals (166). The desired RF signal (156) includes at least one coded pilot signal (Ec). A ratio (Ec/Io) (142) of the at least one coded pilot signal (Ec) to an estimate of the composite RF signal is determined responsive to receiving at least one of the first representation of the composite RF signal (158) and the second representation of the composite RF signal (160). A selected state of the first antenna(114) and the second antenna (116) is controlled responsive to at least one of the ratio (Ec/Io) (142) and an integrated received signal strength indication (?RSSI) of the composite RF signal.

Cdma radio subscriber unit having a switched antenna diversity apparatus and method therefore

Abstract: A radio subscriber unit (102) comprises controller (108) and a switched antenna diversity receiver apparatus (106) including a first antenna (114), a second antenna (116) and a receiver (126). The first antenna (114) is adapted to receive a first representation (158) of a radio frequency (RF) signal (156). The second antenna (116) is adapted to receive a second representation (160) of the RF signal (156). The receiver (126), selectively coupled to the first antenna (114) and the second antenna (116), generates a received signal (153) responsive to receiving at least one of the first representation (158) of the RF signal (156) from the first antenna (114) and the second representation (160) of the RF signal (156) from the second antenna (116). The controller (108), coupled to the receiver (126), selectively couples to the receiver (126), responsive to the received signal (153), one of: only the first antenna (114), only the second antenna (116) and both the first antenna (114) and the second antenna (116).

Electrical contact probe for sampling high frequency electrical signals

Abstract: An all-electrical high frequency contact sampling probe provides sub-micron spatial resolution and picosecond or sub-picosecond temporal resolution. In a preferred embodiment, the probe is a monolithic integration of a sampling circuit with a cantilever and probe tip, where the distance between the circuit and the tip is less than a wavelength of interest in an RF signal VRF !. The sampling circuit 44! uses Schottky diodes SD! for sampling the RF signal VRF ! from a device under test at a rate determined by local oscillator signals 50, 52!. An IF signal VIF ! produced by the sampling probe is an equivalent time representation of the RF signal. Applications include testing signals at interior nodes of high speed integrated circuits.

Range gated strip proximity sensor

Abstract: A range gated strip proximity sensor uses one set of sensor electronics and a distributed antenna or strip (57) which extends along the perimeter to be sensed. A micro-power RF transmitter (10) is coupled to the first end of the strip and transmits a sequence of RF pulses on the strip to produce a sensor field along the strip. A receiver (12) is coupled to the second end of the strip, and generates a field reference signal in response to the sequence of pulses on the line combined with received electromagnetic energy from reflections in the field. The sensor signals comprise pulses of radio frequency signals having a duration of less than 10 nanoseconds, and a pulse repetition rate on the order of 1 to 10 MegaHertz or less. The duration of the radio frequency pulses is adjusted to control the range of the sensor. An RF detector feeds a filter capacitor (65) in response to received pulses on the strip line to produce a field reference signal representing the average amplitude of the received pulses. When a received pulse is mixed with a received echo, the mixing causes a fluctuation in the amplitude of the field reference signal, providing a range-limited Doppler type signature of a field disturbance.