Abstract: An embodiment of the present invention relates to impedance matching applied to a radio apparatus having an antenna. The antenna transmits and receives a signal of a predetermined frequency band. A high-frequency signal processing unit performs a signal processing on the signal transmitted from and received by the antenna. The signal path connects the antenna with the high-frequency processing unit. The signal path is structured in a manner such that, at one point between the antenna and the high-frequency signal processing unit, the signal path is branched out to a plurality of branched line paths that each include at least an inductance component and a capacitance component and, at another point between them, the respective branched-out branched line paths are gathered. By adjusting the number of a plurality of branched line paths, the impedance is matched in the predetermined frequency band.

Abstract: The present invention relates to an antenna matching device that varies a frequency bandwidth according to mobile communication services, and to a transceiver having the same. To this end, an exemplary embodiment of the present invention provides a transceiver that varies a frequency band and a bandwidth according to required services in a mobile communication system, the transceiver including an antenna matching controller that generates a prescribed switch control signal according to a service requested by a user, an antenna variable matching unit that variably forms a matching circuit according to the switch control signal to be transmitted from the antenna matching controller and varies the frequency band and the bandwidth, an analog processing unit that processes a signal to be transmitted/received through the antenna variable matching unit, and a wideband antenna that transmits/receives a radio frequency according to the frequency band and the bandwidth set by the antenna variable matching unit.

Abstract: A programmable antenna includes a fixed antenna element and a programmable antenna element that is tunable to one of a plurality of resonant frequencies in response to at least one antenna control signal. A programmable impedance matching network is tunable in response to at least one matching network control signal, to provide a substantially constant load impedance. A control module generates the antenna control signals and the matching network control signals, in response to a frequency selection signal.

Abstract: A method and apparatus for dynamically adjusting the impedance between a transmitter's power amplifier (PA) and antenna to efficiently transfer power from the PA to the antenna. The impedance between the PA and the antenna is adjusted based on power level measurements and/or PA direct current (DC) consumption measurements, depending on whether the PA is a linear PA or a switch-mode PA. In another embodiment, a hybrid PA including a first stage linear PA and a second stage switch-mode PA is implemented in a transmitter. The hybrid PA selectively connects the output of the first stage linear PA to one of the input of the second stage switch-mode PA and the output of the hybrid PA, depending on the output power level of the first stage linear PA, the output power level of the hybrid PA, or a requirement indicated by a transmit power control (TPC) command.

Abstract: A cellular phone covering a plurality of frequency bands, includes (a) an antenna, (b) a high-frequency circuit, (c) an antenna-matching circuit electrically connecting in series between the antenna and the high-frequency circuit, and (d) a first unit which varies a ground length in accordance with a frequency band in which the cellular phone makes communication with others, the ground length being defined as a length of a ground area for the antenna-matching circuit.

Abstract: A power supply creates a voltage difference between high and low power supply rails. The power supply has a voltage signal source, a capacitive coupling element, energy storage element 12, first and second rectifying diodes, a regulator, and bypass means for selectively decreasing the impedance between the voltage signal source and the low power supply rail or increasing the load presented to the voltage signal source. The capacitive coupling element is connected to the voltage signal source. Energy storage element 12 stores energy between the high and low power supply rails. The first rectifying diode is positioned between the capacitive coupling element and energy storage element 12. It is coupled to the voltage signal source through the capacitive coupling element and arranged to favor current flow toward energy storage element 12 from the capacitive coupling element. The second rectifying diode is positioned between the capacitive coupling element and the low power supply rail.

Abstract: A wide-band antenna comprises a series-resonant antenna and a resonant circuit. The antenna has a radiative element and a feed pin. The resonant circuit comprises an inductive element connected to the feed pin and a capacitor connected in parallel to the inductive element, which has a center tap for adjusting the impedance of the resonant circuit relative to the antenna impedance. The antenna can be a low-impedance PILA, a helix, monopole, whip, stub or loop antenna. The wide-band antenna can be used for the low (1 GHz range) or high (2 GHz range) band. The antenna can be made to simultaneously cover both 850 & 900 bands with the ground plane small enough to be implemented in a mobile phone or the like. The center tap is either connected to the feed of the antenna or connected to an RF front-end dependent upon the impedance level of the antenna element.

Abstract: Disclosed is a circuit and method for automatic tuning of a resonant circuit in a transceiver having a receiver and a transmitter that includes a power amplifier for driving the resonant circuit. During a transmit mode of the transceiver, a resonance voltage of the resonant circuit is compared to an input voltage signal to the power amplifier to determine an error signal that is converted into a control word. The control word drives an adjustable capacitance bank that is part of the resonant circuit. During a receive mode of the transceiver, the control word value is held constant to substantially maintain resonance of the resonant circuit during operation of the receiver.

Abstract: A dual-band antenna matching system and a method for dual-band impedance matching are provided. The method comprises: accepting a frequency-dependent impedance from an antenna; and, selectively supplying a conjugate impedance match for the antenna at either a first and a second communication band, or a third and a fourth communication band. More specifically, the method comprises: tuning a first tuning circuit to a first frequency; and, simultaneously tuning a second tuning circuit to a second frequency. In response, a conjugate match is supplied to the antenna in the first communication band in response to the first frequency. Simultaneously, the antenna is matched in the second communication band in response to the second frequency. When the first tuning circuit is tuned to a third frequency, and the second tuning circuit is tuned to a fourth frequency, then conjugate matches are supplied for the third and fourth communication bands, responsive to the third and fourth frequencies, respectively.

Abstract: A sub-band antenna matching method and an antenna matching system for selectively matching a communication bandwidth segment impedance have been provided. The method comprises: accepting a frequency-dependent impedance from an antenna; and, selectively supplying a conjugate impedance match for the antenna at a sub-band of a first communication band. In some aspects, the method selectively supplies a conjugate impedance match for the antenna at a sub-band of a second communication band. More specifically, the method comprises: tuning a first tuning circuit to a first frequency; simultaneously tuning a second tuning circuit to a second frequency to match the antenna at a low end of the first communication band. Likewise, the first tuning circuit is tuned to a third frequency and the second tuning circuit is tuned to a fourth frequency to match the antenna at a high end of the first communication band in response to the third and fourth frequencies.

Abstract: Described is a universal dipole which may include a feed line coupled to a first fitting; a balun coupled to a second fitting; a first variable length antenna element coupled to the first fitting; a second variable length antenna element coupled to the second fitting; a support plate holding the feed line and the balun at a fixed spacing, the support plate including a short circuit path between the feed line and the balun; and a sliding short assembly attachable between the feed line and the balun to create a short circuit at variable distances along the feed line and the balun.

Abstract: Proximity of a user body part can be detected by measuring the effects such proximity has on antenna impedance mismatches. The amount of mismatch affects the amount of RF signal energy reflected back into a transmission line connecting the antenna to a RF signal source. A directional coupler has a main line electrically connected to the transmission line, as well as a coupled line. The directional coupler produces a signal on its coupled line in relation to the magnitude of reflected energy on the transmission line; the amount of reflected energy varies in response to how well the antenna impedance matches the transmission line impedance. A signal detector is electrically connected to the coupled line, and responds to signals produced in the coupled line by the main line. The signal detector output is then used to determine whether a body part is in proximity. Other aspects the invention include an adaptive algorithm to adjust a threshold for proximity determination.

Abstract: There is provided a flat antenna that includes a feed conductor, and at least one non-feed conductor positioned on either one side or both sides of the feed conductor depending on the required reception band. Thus, a flat antenna that is capable of receiving television broadcast can be miniaturized. In addition, a matching circuit that is so configured that the resonant frequency of the flat antenna is made variable is provided integrally. Through this matching circuit, the resonant frequency of the flat antenna can be varied so as to correspond to the desired reception channel.

Abstract: An antenna is constituted in which a variable capacitance capacitor portion Ct is connected between an antenna element and a ground. In the variable capacitance capacitor, a plurality of variable capacitance elements using a thin film dielectric layer whose dielectric constant is changed by a voltage applied are connected in parallel with regard to direct current component and in series with regard to high frequency component between an antenna-element-side terminal and a ground-side terminal. The capacitance change ratio of the variable capacitance capacitor that depends on the bias signal can be utilized to the maximum so as to perform impedance matching so that the electrical length of the antenna element is changed, and thus, the operating frequency can be changed. In addition, the antenna having small waveform distortion and intermodulation distortion, high power handling capability and low loss at high frequencies can be realized.

Abstract: Disclosed is a circuit and method for continuous automatic tuning of a resonant circuit. A resonance voltage of the resonant circuit is phase shifted by a predetermined phase shift ? degrees and an input voltage signal to a power amplifier driving the resonant circuit is phase shifted by ?±90 degrees to place the signals in quadrature. The phase shifted signals are mixed to obtain a error signal. The error signal is compared to a predetermined voltage range in order to generate control signals for a control word generator, such as an up-down counter. The control word generator produces a control word that drives a capacitance bank that is part of the resonant circuit. The present invention continuously automatically adjusts the capacitance of the capacitance bank to tune the resonant circuit.

Abstract: An antenna device includes a ground conductor plate, and a radiating conductor plate made of a metal plate, which is spaced from the ground conductor plate. The radiating conductor plate is provided with adjusting means for adjusting the electrical length. Thus, the correction of the electrical lengths can be made even if there is a difference between the electrical lengths of the radiating conductor plate caused by assembling errors, etc. In addition, when the antenna device is used in a state in which it is connected to external equipment, the adjusting means allows the adjustment of the electrical lengths of the radiating conductor plate even if the electrical lengths of the radiating conductor plate are subjected to the electrical influence from the electrical equipment and its surrounding environment.

Abstract: A transponder 14.1 for a radio frequency (RF) identification system comprises an antenna 22.1 having an antenna impedance (ZA) having a real part (RA) connected to transponder circuitry presenting a load impedance (ZL) having a real part (RL), a ratio ( R L R A ) of the real part (RL) of the load impedance and the real part (RA) of the antenna impedance having a first value that is bigger than one when the transponder is not transmitting data. During transmission of data the ratio is switched between the first value and a second smaller value.

Abstract: A dual-band antenna matching system and a method for dual-band impedance matching are provided. The method comprises: accepting a frequency-dependent impedance from an antenna; and, selectively supplying a conjugate impedance match for the antenna at either a first and a second communication band, or a third and a fourth communication band. More specifically, the method comprises: tuning a first tuning circuit to a first frequency; and, simultaneously tuning a second tuning circuit to a second frequency. In response, a conjugate match is supplied to the antenna in the first communication band in response to the first frequency. Simultaneously, the antenna is matched in the second communication band in response to the second frequency. When the first tuning circuit is tuned to a third frequency, and the second tuning circuit is tuned to a fourth frequency, then conjugate matches are supplied for the third and fourth communication bands, responsive to the third and fourth frequencies, respectively.

Abstract: A duplexer structure for allowing an RF transmitter and an RF receiver to share a common antenna includes impedance matching circuitry to match the receiver input impedance to the antenna impedance during a receive operation and impedance transformation circuitry to transform the antenna impedance to a lower impedance at the receiver input terminals during a transmit operation. The impedance matching circuitry and the impedance transformation circuitry of the duplexer share one or more passive components, thus reducing the overall number of components required to implement the duplexer. This reduction in component count reduces the amount of chip area required to implement the duplexer and increases the ease with which the RF transceiver is integrated onto a semiconductor chip. In one embodiment, the duplexer uses a differential topology to provide common mode noise rejection and even harmonic distortion cancellation within a transceiver.

Abstract: Disclosed is an apparatus for commonly using an antenna for a call signal and a television (TV) broadcasting signal in a radio communication terminal including an antenna, a phone duplexer, a TV tuner, an LC parallel circuit, connected between the antenna and the phone duplexer, for forming an LC resonance circuit for a call signal frequency band, an LC series circuit connected to a connected point of the LC parallel circuit and the antenna and to a DC power supply terminal, a stub for impedance matching one terminal of which is connected between a capacitor and an inductor of the LC series circuit and the other terminal of which is connected to the TV tuner, and a path providing section for providing a path between a connected point of the stub and the TV tuner and a ground terminal in accordance with a switching control signal provided according to a TV or call operating mode.

Abstract: An antenna (24) for minimizing reception of undesirable signals below a predetermined frequency band includes a first and a second terminal (A, A′) connectable to at least a receiver (22). The antenna components are connected to the first and second terminals, and a filter (26) is integrally connected across the first and second terminals (A, A′). The filter matches an impedance value of the antenna components with an impedance value of the receiver. Moreover, the filter effectively forms a short circuit at the undesirable frequency to minimize reception of undesirable signals below the predetermined frequency band.

Abstract: A wide-band self-tuning antenna system for the reception of VHF/UHF signals includes planar antenna elements located on both the surfaces of a printed circuit board and a tuner unit which includes a plurality of matching networks for the respective plurality of bands of frequencies. The planar elements on the respective surfaces of the printed circuit board are substantially identical in shape.

Abstract: An in-glass antenna system for a window with adjustable impedance for impedance matching. The in-glass antenna system includes an in-glass slot antenna that is defined by an upper portion, a lower portion and two respective side portions. An in-glass impedance matching circuit is connected to the slot antenna, wherein the impedance matching circuit adjusts the impedance of said slot antenna.

Abstract: A tunable antenna includes separate radiator parts coupled to one another. The coupling between the parts is changed by rotating and/or displacing the parts with respect to one another such that the antenna exhibits a radiation pattern associated with a respective degree of a rotation and/or displacement. A process for manufacturing such antennas includes constructing parts for a respective antenna, coupling the parts to one another to permit them to rotate and/or displace, measuring the radiation pattern of the parts, and adjusting the radiation pattern by rotating and/or displacing the parts with respect to one another to set a nominal radiation pattern of the respective antenna formed by the parts. The couple is changed by rotation and/or displacement of the parts. A respective degree of rotation and/or displacement creates a corresponding change of a radiation pattern of the parts.

Abstract: A transmission system delays a carrier wave and program audio in the digital domain. The carrier wave and the program audio are converted to analog and the carrier wave is modulated by the program audio. The system includes a master oscillator that generates a digital carrier wave. The digital carrier wave is transmitted to a delay stage that delays the digital carrier wave by a certain delay value. The system further receives an analog or digital signal that is representative of programming. If an analog signal is received, the signal is transmitted to an analog-to-digital converter where it is converted to digital audio. The digital audio is then transmitted to a delay stage that delays the digital audio by the same delay value. The digital carrier wave and the digital audio are converted to an analog carrier wave and analog audio respectively. A modulator modulates the analog carrier wave by the analog audio and sends the amplitude modulated carrier wave to a power amplifier.

Abstract: The invention described herein relates to an antenna system which makes use of the waveguide properties of sea ice. The antenna system broadly includes at least one antenna wire extending along and preferably in contact with a sea ice surface for transmitting and receiving substantially vertically polarized radio waves. In a first embodiment, the antenna system has a single antenna wire connected to a tuner at one end and grounded to seawater at a second end. The antenna system also has a second length of wire attached to the tuner. The second wire passes through a hole in the sea ice and is also grounded to the seawater beneath the sea ice. In an alternative embodiment, only the second wire is grounded to the seawater beneath the sea ice. The single antenna wire in this embodiment is ungrounded. In yet another embodiment, the antenna system comprises a dipole antenna wire laying on the surface of the sea ice and being connected to a radio for transmitting and receiving radio signals.

Abstract: The present invention provides a glass antenna system with improved reception, a connector of the glass antenna system and a method of producing the glass antenna system. The glass antenna system includes a glass substrate, at least one electroconductive antenna element positioned along a major surface of the substrate, wherein the antenna element provides an impedance which varies over a given frequency band, an impedance matching network secured to the glass substrate in a position such that the impedance matching network is electrically coupled to a portion of the antenna element, and means to electrically interconnect the network to a feedline of an electromagnetic energy transmitting and/or receiving unit. The impedance matching network is used to transform the impedance of the antenna element to a desired impedance. In one particular embodiment of the invention the impedance matching network is part of a connector and is formed along a first major surface of a printed circuit board.

Abstract: An unbalanced to balanced antenna matching unit (AMU) is capable of operating over a relatively large frequency range by utilizing multiple transformers connected in series, with a set of bypass switches used to control the number of transformers that are "active" in the matching unit at any particular time. Complex impedance matching by the AMU is controlled by a variable capacitor in parallel with the multiple transformers and a variable capacitor in series with the unbalanced input. The parallel variable capacitor may be located on either side of the transformer arrangement. The transformer output may be configured to switch between matching either a low impedance antenna or a high impedance antenna.

Abstract: A tuneable antenna including an elongated radiating element with a conductive loading coil positioned on an insulating member. A capacitor is formed above the loading coil with a conductive member overlying the loading coil and movable with respect to the coil and the capacitor to change the resonant frequency of the antenna.

Abstract: A matching circuit and an antenna apparatus which, though small-sized, can be used in a radio apparatus which transmits and receives radio waves having a wide range of frequencies. A matching circuit includes an inductance element formed of a chip inductor connected in series with an antenna body, a first capacitance element formed of a trimmer capacitor, and a second capacitance element formed of a chip capacitor, which capacitance elements are connected between respective ends of the inductance element and a ground terminal, and thus in parallel to the antenna body. One end of the inductance element is connected to the power supply terminal of the antenna body, and the other end is connected to a power source for applying a voltage to the antenna body. The first capacitance element is connected between a ground and the connection point of the power supply terminal of the antenna body and the inductance element.

Abstract: A new and improved antenna-transmission line coupling system is provided wherein the electro-magnetic oscillations in the antenna are prevented from entering the circuitry which couples the antenna to its transmission line. The coupling structure (called coupler) includes an impedance matching transformer and a capacitor connected to the transformer and capacitively coupled with the antenna element. Various embodiments are provided for varying the capacitive coupling with the antenna element. Antenna elements having capacitor plates on their ends are disclosed; as well as an arrangement wherein a universal coupler having a broad band impedance matching transformer can be used with any number of antenna elements each tailored for a different commercial RF frequency band.

Abstract: The present invention relates to a matching and tuning network for connecting a source of RF power to a complex load. The network is comprised of a primary circuit and a secondary circuit. The primary circuit is comprised of a fixed capacitor connected in series with a primary winding of a coupling transformer connected to said source of RF power. The secondary circuit is comprised of a series connection of a secondary winding of said coupling transformer and a variable capacitor connected to said load. The network is further comprised of an input voltage sensor; and an input current sensor both connect to an impedance detector and a phase detector. The impedance detector controls an encoder for varying the coupling between the primary winding and the secondary winding of the coupling transformer to maintain a constant input impedance. The phase detector controls the same encoder for varying the capacity of the variable capacitor so as to maintain a zero phase shift at the input to the network.

Abstract: An automatic antenna tuner which conjugately matches the impedance of an electrically small antenna to the impedance of a transmit amplifier output stage by using a pi-type impedance matching network with adjustable capacitive circuit components which are preferably implemented using a low cost escapement mechanism. During an initial set up tuning procedure, a resistive Wheatstone bridge detector is disposed between the output of the power amplifier and the input to the pi network, to feedback a measure a degree of match of the pi network to a controller. The capacitive elements in the legs of the pi network are then electromechanically adjusted under the operator of the controller until an optimum setting is found. These initial impedance values are determined for each frequency in an operating range and then stored in a non-volatile memory.

Abstract: In a radio transmitter (100) that includes a power amplifier (104) and an antenna (106), a method for enhancing an operating characteristic of the radio transmitter (100) can be accomplished in the following manner. The power amplifier (104) provides a signal (113) to a variable matching network (111), wherein the signal (113) comprises energy to be radiated by the antenna (106). The variable matching network (111) couples the signal (113) to a sampler (112) that is operably coupled to an output of the variable matching network (111 ) and the antenna (106). The sampler (112) samples a forward component (114) and a reflected component (115) of the signal (113). The radio transmitter (100) processes the sampled forward and reflected components (116, 118) to produce a feedback control signal (120). The feedback control signal (120) is used to adjust the variable matching network (111 ), such that an operating characteristic of the radio transmitter (100) is enhanced.

Abstract: A bandwidth-enhanced antenna system for operating on one of a plurality of selected frequency bands includes a whip or wire antenna element having band selection wires and a contiguous set of inductors arranged in series, each of the inductors being sufficiently separated from one another and being arranged such that the resonant frequency of any of said inductors is greater than the highest operating frequency of the plurality of frequency bands. Selector means is included provide a band select signal, and a plurality of switches each having a first terminal connected to a corresponding one of the inductors and a second terminal connected to the feed-end of the antenna element. The switches are responsive to the bandwidth select signal to allow communication using a selected one of the plurality of the frequency bands. An impedance matching network may be used for coupling an external receiver or transmitter to the feed-end of the antenna element.

Abstract: A method and circuit for detecting and reducing the impedance mismatch between the directional coupler and the antenna of an RF communications system exposed to externally generated RF signals. The impedance mismatch is detected by the quadrature multiplication of the signal passing through a directional coupler in the forward and reverse directions with the detection being enhanced by the use of a forward direction signal substantially devoid of externally generated RF signal components.

Abstract: An antenna (105) for receiving radio frequency (RF) signals includes a conductive element (300) having a first electrical length and a first operating impedance and a transmission line (315) having a second electrical length and a second operating impedance for resonating the conductive element (300) at a predetermined operating frequency. A coaxial element (305) having a third electrical length is coupled to the conductive element (300) and the transmission line element (315) for converting the first operating impedance to the second operating impedance. When the conductive element (300) is resonated, the first, second, and third electrical lengths are substantially equal to a quarter wavelength or an odd multiple thereof at the predetermined operating frequency.

Abstract: A panel antenna suitable for use in cellular communication applications provided with means for mechanically and electrically adjusting the tilt of the antenna beam. Electrical down tilt being achieved by varying the length of a first feed line to a group of dipole pairs. Mechanical down tilting of the antenna beam being achieved by tilting the antenna ground plane and dipole driver assembly with respect to a housing.

Abstract: Switchable inductors for strong currents are used especially in antenna tuning circuits. The value of the inductance between the terminals of the primary winding of an air-core static transformer is different depending on whether the secondary winding of the transformer is placed in an open circuit or in a short circuit by switching means formed by power semiconductor elements. Application in particular to antenna coupling circuits for VLF stations working by frequency hop transmission with highly selective antennas.

Abstract: A portable radio apparatus having a casing thereof keeps a matching state of an antenna thereof in the call waiting state and in the operating state of the apparatus. The casing is foldable and expandable and accommodates therein a transmitting and receiving circuit connected via a variable matching circuit to the antenna. The matching circuit is connected to a sensor disposed in the casing for sensing a folded state thereof. Depending on a result of the sensing operation of the sensor, the matching circuit changes the matching state.

Abstract: A transformer having a core of soft magnetic material around which a first winding and a second winding are wound and a leakage inductance based on the magnetic coupling between these windings. The effective leakage reactance is minimized by adding a third transformer winding serially connected to a capacitor, the latter of which is varied to reduce the leakage reactance over a broad frequency range.

Abstract: An impedance matching device that is particularly suited for high speed, high power applications is disclosed. The impedance matching devices employ magnetic coupling allowing their usage in a "frequency-agile" environments such as communication as well as communication jamming and deception techniques without creating high current, high voltage and thermal conditions that might otherwise damage the related switching devices. The impedance matching device provides a predetermined impedance to transform a load impedance Z.sub.L into a desired characteristic impedance Z.sub.0 over a frequency range having a lower and an upper band. The device comprises one or more first and second inductive components. Each of the first inductive components has an impedance characteristic associated with said lower band, whereas each of the second inductive component has an impedance characteristic associated with the upper band.

Abstract: In an automatic tuning system for an antenna having a single variable reactance element, the power transmitted to the antenna and the power reflected from the antenna on the feedline are sensed. The variable reactance component of the antenna is adjusted until the ratio between the transmitted and reflected power on the feedline indicates that the standing wave ratio on the feedline is at a minimum, whereupon the antenna will be tuned. The adjustment of the variable reactance component is by a stepping motor controlled by a microprocessor, which is programmed to make calculations to determine when the standing wave ratio reaches a minimum.

Abstract: A low cost, high efficiency, end fed half wave folded dipole radio frequency antenna. The antenna includes an improved balun including a conductive tubular base secured to a conventional coaxial cable connector, a conductive tube telescoped relative to the base with a slot between the base and tube having an area corresponding to the extent the tube and base are telescoped together and two wires within the tube connected to the coaxial connector and each having an insulating sleeve. A folded wire loop antenna is connected to the wires and extends away from the balun. The loop may include coils to improve the gain of the antenna. A tubular insulating housing encapsulates the antenna.

Abstract: In a circuit arrangement for matching the resonant frequency of an antenna resonant circuit (18) to the output circuit of a transmitter output stage (10), the antenna resonant circuit (18) is coupled via a reactance to the transmitter output stage (10). By means of a current sensor (16), the supply direct current of the transmitter output stage (10) is detected. The value of a tuning component (26), lying in the antenna resonant circuit (18), can be changed by a control signal; the tuning component is a governing factor for the resonance frequency of the antenna resonant circuit (18). A comparator and control unit (36)repeatedly samples the value of the supply direct current detected by the current sensor (16). In dependence upon the result of a comparison with a sequential previously sampled value, it applies th control signal to the tuning component (26) to obtain a maximization of the supply direct current detected.

Abstract: An automatic antenna coupler is disclosed. The antenna coupler automatically matches the output impedance of a 50-ohm transmitter to the input impedance of a non-broad-band antenna, such as a whip, dipole or long wire. The resulting increase in transmit coupling efficiency provides greater radiative power than that available from an unmatched antenna.

Abstract: An efficiency monitoring antenna which has a sampling pick-up loop and LED coupled to the lead-in and senses and indicates returning power flow. Tuning and impedance matching elements are also included which allow the antenna to be tuned and matched to the transmission line.

Abstract: The present invention provides within three particular aspects thereof an isolating and matching device operable to enable an electrically heatable window of a motor vehicle to be used as an efficient VHF communications aerial or antenna; wherein isolating and matching circuitry is provided for Series VHF Matching, Shunt VHF Matching and Split Passband Matching of an electrically heatable window heating element to an aerial input impedance of an aerial feeder circuit of a radio frequency receiver or transmit/receive device.

Abstract: An RF signal input circuit for a UHF tuner of a television receiver comprises a series-tuned circuit including a varactor diode and an inductance element connected in series, in the order named, between signal ground and a gate electrode of a field-effect transistor RF amplifier. The series-tuned circuit has a relatively uniform bandwidth throughout the UHF range. A capacitor connected in shunt with the gate electrode completes a "split-capacitor" configuration in which the varactor diode and the shunt capacitor form a variable impedance transformation network for making the relationship between the effective impedances of the series-tuned circuit and FET amplifier relatively uniform throughout the UHF range. The order of the varactor diode and inductance element allows a low cost adjustable capacitor comprising a grounded shield wall as one plate and a movable tab as a second plate to be connected directly across the varactor diode.

Abstract: The present invention provides within three particular aspects thereof an isolating and matching device operable to enable an electrically heatable window of a motor vehicle to be used as an efficient VHF communications aerial or antenna; wherein isolating and matching circuitry is provided for Series VHF Matching, Shunt VHF Matching and Split Passband Matching of an electrically heatable window heating element to an aerial input impedance of an aerial feeder circuit of a radio frequency receiver or transmit/receive device.