Abstract: There is provided a voltage standing wave ratio detection circuit which includes a filter that limits a frequency of a transmission wave, a detection circuit that detects a reflected wave of the transmission wave, the transmission wave being reflected from a load connected in a later stage of the filter and having passed through the filter, a storage device that stores correction information on the basis of a reflected wave generated at a time which a reference load has been connected in the later stage of the filter, and an arithmetic circuit that corrects a voltage standing wave ratio calculated on the basis of the reflected wave and the transmission wave by correcting the reflected wave detected by the detection circuit on the basis of the correction information.

Abstract: A signal transmitting/receiving circuit includes a transmitter, a receiver, a balun and an impedance matching circuit. The transmitter is utilized for transmitting an output signal. The receiver is utilized for receiving an input signal. The balun includes a first input terminal, a second input terminal and an output terminal. The impedance matching circuit, which is coupled between the transmitter, the receiver, and the balun, provides transmitting impedance when the transmitter transmits the output signal such that an output signal may be output at an output terminal of the balun via a transmitting path. Also, the impedance matching circuit provides transmitting impedance when the receiver receives the input signal such that the input signal may be transmitted from the output terminal of the balun to the receiver via a receiving path.

Abstract: An antenna arrangement comprising an input/output connection and a first and a second tuning network with different transfer functions. The arrangement additionally comprises an antenna and a switch for connecting the input/output connection of the arrangement to one of said tuning networks, with a second switch for connecting the antenna of the arrangement to the tuning network to which the input/output connection of the arrangement has been connected. The arrangement comprises a sensor for sensing a form factor of the arrangement or of an apparatus in which the arrangement is used, and said sensor can be used for influencing said first and second switches, so that a device which has been connected to the arrangement may be connected to the antenna via a tuning network optimal for the current form factor of the arrangement.

Abstract: A power amplifier system includes a first power detector configured to detect a forward power output of a power amplifier, the first power detector configured to provide a first power detector output and an adjustable load coupled to the output of the power amplifier and configured to receive the first power detector output, the adjustable load configured to provide an adjustable impedance at the output of the power amplifier in response to one of the output of the power amplifier and the first power detector output.

Abstract: The present disclosure relates to the efficient transmission of voice and data signals using mobile terminals, and in particular to optimizing the power added efficiency (PAE) of a power amplifier (PA) by controlling the amplifier's load impedance over a range of radio frequency (RF) output power levels. A power amplifier having a first power level and at least a second power level is provided along with a first impedance matching network section with an output. A second impedance matching network section and at least a third impedance network section in communication with the output are selectably coupled to a load network by switches that are opened and close in response to various power levels of operation for the load switch circuit.

Abstract: According to an aspect of the present invention, the magnitude and phase angle of looking-in impedance driven by an amplifier are computed in digital domain during normal operation within a module containing the amplifier. In an embodiment, the computed magnitude and phase angle are used for impedance matching at a node driven by the amplifier. As a result, impedance matching may be obtained even in situations when the impedance changes during operation.

Abstract: When the change speed is instructed, without changing value of a suppressing vibration flag set to value 1 as initial value, a fast fill as the preparation of a brake to be engaged when the change speed is executed and low pressure standby of hydraulic pressure to set the brake in a half-engaged state. Then the suppressing vibration flag is set to value 0 when a predetermined time passed since the change speed is instructed, a sum of a drive torque required for driving and a suppressing vibration torque, which is in the same direction as suppressing rotational fluctuation of a drive shaft, is output from a motor when the suppressing vibration flag is set to value 1.

Abstract: A down-conversion filter is provided, using first and second input terminals to receive signals that are differentially outputted by a preceding circuit, and using an output terminal to output a down-converted and filtered signal. An output capacitor is coupled to the output terminal. A first switched-capacitor network is arranged between the first input terminal and the output terminal. A second switched-capacitor network is arranged between the second input terminal and the output terminal. Each switched-capacitor network has capacitors, charging switches and charge-summing switches. The charging switches are designed to alternatively couple the capacitors to the first (or second) input terminal. The charge-summing switches are designed to couple the capacitors to the output terminal.

Abstract: A mobile wireless communications device includes a portable housing, a transmitter carried by the portable housing and configured to modulate an input signal, and an adjustable impedance matching network coupled downstream from the transmitter. An antenna is coupled downstream from the adjustable impedance matching network, and a non-directional coupler is coupled between the adjustable impedance matching network and the antenna. A feedback receiver is coupled to the non-directional coupler to generate a feedback signal. A controller is configured to control the adjustable impedance matching network based upon the input signal and the feedback signal.

Abstract: Methods and apparatus are disclosed for automatically adjusting antenna impedance match in a wireless transceiver employing phase-amplitude modulation. According to some embodiments of the invention, a wireless transceiver comprises a transmitter circuit and a receiver circuit connected to the antenna by a transmit/receive duplexer. An electronically adjustable matching network is located between the transmitter output and the antenna. To control the adjustable matching network, a directional coupler is located between the transmitter output and the matching network to separate transmit signals reflected from the antenna system, including the antenna, the matching network and the T/R duplexer. The reflected transmit signals are routed to the receiver circuit, which digitizes the reflected signal and determines an antenna reflection coefficient based on the digitized reflected signal and the modulation signal used to create the transmit signal.

Abstract: A radio communication device capable of lightening the influence of a frequency selective fading in the wide-band transmission of a single carrier thereby to prevent deterioration of error rate characteristics. In this device, an FFT unit subjects a modulated signal inputted from a modulation unit to a Fourier transformation. A pilot insertion unit inserts a pilot symbol into a plurality of individual frequency components of the modulated signal. Weight multiplication units multiply the individual frequency components and the pilot symbols inserted into the individual frequency components, by weight coefficients set at a weight coefficient setting unit. IFFT units subject the frequency components to an inverse Fourier transformation, thereby to convert the frequency components into time domains.

Abstract: The present invention concerns a load modulation arrangement adapted to be connected to an amplifying device. The load modulation arrangement comprises a first reactive element, a second reactive element and at least one variable capacitive element. Further, the load modulation arrangement comprises a quarter wave transforming element adapted to be connected to the first reactive element. The present invention also concerns a method for load modulation, a wireless transceiver and a radio transmission device.

Abstract: The present disclosure relates to combining tunable antenna matching circuit adjustments and RF power amplifier output power adjustments of a first RF terminal in response to output power adjustment commands received from a second RF terminal. The output power adjustment commands may be part of an output power control loop between the first RF terminal and the second RF terminal to control the output power from the first RF terminal. The first RF terminal may include an RF receiver, an RF power amplifier, and a tunable antenna matching circuit coupled between an output of the RF power amplifier and an antenna. The tunable antenna matching circuit adjustments may be impedance adjustments of the tunable antenna matching circuit and the RF power amplifier output power adjustments may result from adjustments to one or more input signals to the RF power amplifier.

Abstract: Embodiments include methods and apparatus for detecting a phase angle between an incident signal and a reflected signal. The apparatus comprises a plurality of phase shifters and additional circuitry. The plurality of phase shifters is adapted to apply first phase shifts to a representation of the incident signal and to apply second phase shifts to a representation of the reflected signal. The additional circuitry, which is operatively coupled to the plurality of phase shifters, is adapted to produce a first indication of a location of a relative phase difference between the incident signal and the reflected signal within a first region of a first reference circle, and to produce a second indication of the location of the relative phase difference within a second region of a second reference circle, wherein the second reference circle is rotated with respect to the first reference circle.

Abstract: A radiocommunications terminal includes a send circuit and a receive circuit connected to a send/receive antenna of the terminal and respectively defining, when in operation, a send mode and a receive mode. The terminal also includes a circuit in a common part of the connection of the send and receive circuits to the antenna for matching the send and receive circuits to the antenna. A device for controlling and monitoring the power of signals sent/received by the terminal decenters the impedance matching of the antenna of the terminal only when the device is in send mode. Applications include reducing the energy impinging on the user of a mobile radio communications terminal.

Abstract: A transmitting apparatus and a transmitting method for improving a channel deviation in a mobile communication terminal are provided. The transmitting apparatus includes a power amplifier for amplifying a transmitting signal by a predetermined level and outputting an amplified transmitting signal, a controller for outputting a signal to control a variable capacitor according to a channel of the transmitting signal and a phase transition unit for varying each capacitance value according to a control of the controller and transiting a phase of a signal outputted from the power amplifier.

Abstract: Fuzzy logic is utilized to control an RF amplifier and associated tuner for continuous self-optimization and automatic load matching to at least double the battery life of a battery-powered transmitter.

Abstract: An antenna device for a portable wireless terminal is provided. The antenna device includes a main antenna for mobile communication for transmitting and receiving signal in a first frequency band, a Transmit (Tx) sub-antenna for transmitting signals in a second frequency band, a Receive (Rx) sub-antenna for receiving signals in a third frequency band, and a controller for selectively using one of the Tx sub-antenna and the Rx sub-antenna if the second frequency band overlaps with the third frequency band, and for providing control such that the Tx sub-antenna and the Rx sub-antenna are simultaneously used if the second frequency band does not overlap with the third frequency band. Accordingly, without increasing the volume of the portable wireless terminal, an antenna space can be ensured and radiation performance can be improved.

Abstract: Systems and methods for tuning an antenna for a frequency modulation (FM) transceiver are provided. A representative system includes: a network of electrical adjustable passive components that receives and sends radio frequency (RF) signals to a receiver circuitry via the network of electrical adjustable passive components. The receiver circuitry determines the received signal strength indication (RSSI) of the RF signal. The system further includes a transmitter circuitry that transmits RF signals via the network of electrical adjustable passive components, and a peak detector circuitry that receives and determines a voltage output of the RF signals from the variable capacitors. An auto-tune circuitry receives the RSSI and output value from the receiver circuitry and the peak detector circuitry, respectively.

Abstract: Electronic devices are provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. A parallel-fed loop antenna may be formed from portions of an electronic device bezel and a ground plane. The antenna may operate in multiple communications bands. An impedance matching circuit for the antenna may be formed from a parallel-connected inductive element and a series-connected capacitive element. The bezel may surround a peripheral portion of a display that is mounted to the front of an electronic device. The bezel may contain a gap. Antenna feed terminals for the antenna may be located on opposing sides of the gap. The inductive element may bridge the gap and the antenna feed terminals. The capacitive element may be connected in series between one of the antenna feed terminals and a conductor in a transmission line located between the transceiver circuitry and the antenna.

Abstract: Aspects of a method and system for a transformer in an integrated circuit package are provided. In this regard, signals may be transmitted and/or received via an antenna communicatively coupled to a transformer embedded in multi-layer integrated circuit package. The windings ratio of the transformer may be configured based on an impedance of the antenna, an impedance of a transmitter coupled to the transformer, an impedance of an LNA coupled to the transformer, and/or a power level of the received and/or transmitted signals. The windings ratio may be configured via one or more switching elements which may be MEMS switches embedded in the multi-layer IC package. The transformer may comprise a plurality of loops fabricated on a corresponding plurality of metal layers in the multi-layer IC package, and the loops may be communicatively coupled with one or more vias. The multi-layer IC package may comprise ferromagnetic and/or ferromagnetic materials.

Abstract: A network communication device includes a processor, an amplifier circuit, a matching circuit including a transmitting route and a coupling route, a storage module, and a detection and control module. The network communication device generate electronic signals, and outputs the electronic signals to a load via the transmitting route after the electronic signals being amplified and matched. Then the network communication device detects output signals and reflection signals of the coupling route to calculate a safety parameter accordingly, compares the calculated safety parameter with one or more safety parameter thresholds, and generates control signals to control the amplifier circuit. The network communication device determines if the load is abnormal according to the control signals and generates load abnormal signals if the load is abnormal.

Abstract: A transmission circuit for radio frequency signals has a power mixer and includes a radio frequency input port, a first radio frequency output port, a second radio frequency output port, and a dummy load port. The transmission circuit also has a first switch unit and a second switch unit. The first switch unit is connected to the first radio frequency output port and outputs the radio frequency signals which are emitted from the first radio frequency output port or reflects the radio frequency signals which are emitted from the first radio frequency output port back to the first radio frequency output port. The second switch unit is connected to the second radio frequency output port and outputs the radio frequency signals which are emitted from the second radio frequency output port, or reflects the radio frequency signals which are emitted from the second radio frequency output port back to the second radio frequency output port.

Abstract: An object is to provide a semiconductor device which operates normally even when the communication distance is extremely short, while the maximum communication distance is maintained, and which can make amplitude of a response waveform large even when a large amount of electric power is supplied to the semiconductor device and a protection circuit operates. The object is achieved with a semiconductor device including a first modulation circuit and a second modulation circuit each of which performs load modulation by an input signal, a detection circuit which determines an output signal by electric power supplied externally, a protection circuit which is controlled by the output signal of the detection circuit, and a modulation selecting circuit which switches the first modulation circuit and the second modulation circuit depending on the output signal of the detection circuit.

Abstract: An antenna sense circuit includes a detector and a level shifter. The detector consists of a voltage drop component, a transistor component, a first resistor component, and a second resistor component. The voltage drop component is coupled between a first power supply and a first terminal of the first resistor component. The second resistor component has a first terminal coupled to a second terminal of the first resistor component and a second terminal coupled to a second power supply. The transistor component has a control terminal coupled to the second terminal of the first resistor component and the first terminal of the second resistor component, a second connection terminal coupled to the first power supply, and a first connection terminal for outputting a first detecting signal. The level shifter adjusts a voltage level of the first detecting signal to generate a second detecting signal.

Abstract: A transmitting arrangement includes a matching circuit, a reference circuit and a comparator. The output of the matching circuit can be coupled to an antenna and comprises an adjustable impedance. The reference circuit is connected to an input of the matching circuit and comprises a reference impedance. Inputs of the comparator are coupled to the matching circuit and the reference circuit and its output is coupled to the adjustable impedance via a control input of the matching circuit.

Abstract: A driver amplifier in an integrated circuit is suitable for driving a signal onto an output node and through an output terminal, and through a matching network to a power amplifier. A novel Programmable Output Impedance Adjustment Circuit (POIAC) within the integrated circuit is coupled to the output node and affects an output impedance looking into the output terminal. When the output impedance would otherwise change (for example, due to a driver amplifier power gain change), the POIAC adjusts how it loads the output node such that the output impedance remains substantially constant. The POIAC uses a series-connected inductor and capacitor L-C-R circuit to load the output node, thereby reducing the amount of capacitance and die area required to perform multi-band impedance matching with a power amplifier. Multi-band operation is accomplished by changing an effective capacitance in the L-C-R circuit depending on communication band information received by the POIAC.

Abstract: Embodiments include methods and apparatus for detecting a phase angle between an incident signal and a reflected signal. The apparatus comprises a plurality of phase shifters and additional circuitry. The plurality of phase shifters is adapted to apply first phase shifts to a representation of the incident signal and to apply second phase shifts to a representation of the reflected signal. The additional circuitry, which is operatively coupled to the plurality of phase shifters, is adapted to produce a first indication of a location of a relative phase difference between the incident signal and the reflected signal within a first region of a first reference circle, and to produce a second indication of the location of the relative phase difference within a second region of a second reference circle, wherein the second reference circle is rotated with respect to the first reference circle.

Abstract: A power amplifier (PA) provides dynamic stability and gain control for linear and non-linear operation. The PA operates with a baseband processor and a transmitter, in which the PA receives a signal from the transmitter for power amplification prior to transmission of the signal. The PA is configured to select between the linear mode of operation and the non-linear mode of operation, in which device scaling within the PA is achieved by changing a device sizing of at least one stage of the PA. Further to changing the device size, the PA changes biasing resistance and impedance of a matching network in response to the changing of the device size to control power output and stability for the PA.

Abstract: A novel antenna system for receiving transmissions in the VHF and UHF frequency bands particularly suitable as a miniaturized antenna for UHF reception, such as of digital video broadcasting transmissions. The antenna system utilizes a combination of three techniques including (1) the use of dialect loading using a high dielectric constant ceramic substrate; (2) an antenna dielectrically loaded and tuned to a significantly higher frequency than desired; and (3) use of a tuning circuit to compensate for the frequency offset of the antenna thereby shifting the resonant frequency to cover the entire band. The antenna is intentionally designed to be too small to radiate at the frequency of interest. The antenna element is then ‘forced’ to be tuned to the desired lower frequency using passive (or active) reactive components as part of a tuning circuit. Multi-band operation is achieved by providing a bypass switch to connect the antenna element either to (1) a first receiver without the tuning circuit (i.e.

Abstract: A method of matching a receive-only antenna (60) for use in receiving video signals in which measurements made on a transceiver's antenna (14) when in an transmitting mode are used in matching the receive-only antenna. The ratio of the amplitude of the reflected signal to the strength of the transmitted signal strength is used not only in selecting components for matching the transceiver's antenna (14) but also in selecting components for matching the receive-only antenna (60). The ratio may be applied to respective look-up tables (54, 64) for selecting the components to be used in matching the respective antennas.

Abstract: A closed-loop controlled antenna tuning unit (ATU) system includes a return loss detector connected to sample an RF signal generated by a signal source to provide a return loss signal. A matching state searching circuit is connected to receive the return loss signal and, in response, selectively store a return loss value and an impedance matching state. A central controller is connected to provide a switch control signal and apply an optimum matching state to the impedance synthesizer at the conclusion of the matching state search. An impedance synthesizer is responsive to the switch control signal for coupling a radio frequency signal and matching the impedance of an antenna to a signal source.

Abstract: The invention is a radio transmitter that includes an antenna having at least one driven element and at least one reflector element. The driven element is electrically coupled to a radio carrier source. At least one of the driven elements or the at least one reflector element, includes at least one switch to modulate the radio carrier. Also, a secure communication system includes a radio transmitter configured to transmit a modulated signal within an information beam width. Also, a method for modulating a radio signal includes the steps of causing the transmitted carrier signal to be modulated by the modulation signal in response to switching the at least one reflector switch. Also, a method for selecting desirable antenna reflector switch combinations includes performing a mathematical simulation to determine whether the combination of reflector switch positions results in a modulated signal that can be demodulated within an information beam width.

Abstract: A method of tuning an antenna circuit includes: (a) receiving a signal on an antenna, (b) producing a received signal strength indication based on the received signal, (c) using the received signal strength indication to produce a control voltage, (d) using the control voltage to control a capacitance in an antenna matching circuit, (e) changing the control voltage to minimize a ratio of a change in the received signal strength indication to a change in the control voltage and (f) repeating steps (a), (b), (c), (d) and (e). An apparatus that implements the method is also provided.

Abstract: Disclosed are a mobile station unit which can obtain azimuth information with a simple construction and a radio communication system including the mobile terminal unit. According to the present invention, in a terminal station, an arrival direction obtaining section 203 obtains an arrival direction of a received azimuth designation signal from a reference station or another terminal station using an arithmetic operation or the like. A transmitting direction forming section 204 determines the direction opposite to the arrival direction obtained by the arrival direction obtaining section 203 as a transmitting direction. A reference azimuth detecting section 207 detects the transmitting direction determined by the transmitting direction forming section 204 as a reference azimuth. An azimuth designation signal generating section 205 generates an azimuth designation signal so as to radiate radio waves having directivity in the transmitting direction determined by the transmitting direction forming section 204.

Abstract: An impedance control apparatus and method for portable mobile communication terminal is disclosed capable of accurately adjusting impedances relative to environment when the portable mobile communication terminal is being used, wherein an impedance of a first variable impedance matching part is varied to receive a reception impedance correction signal transmitted by a base station and to detect a reception strength, an impedance of the first variable impedance matching part is set by a impedance value of the largest reception strength out of the reception strengths, the portable mobile communication terminal varies the impedance of a second variable impedance matching part to transmit a transmission impedance correction signal to a base station and to allow the base station to detect the reception strength, and the impedance setting of the second variable impedance matching part is performed using the reception strength detected by the base station.

Abstract: A programmable antenna interface for coupling an antenna to a transceiver having a receiver section and a transmitter section, includes a transformer that is adjustable in accordance with a control signal. A transmit/receive module couples the transformer to the receiver section in a receive mode and to the transmitter section in a transmit mode. The control signal controls the transformer to a first impedance in the transmit mode and controls the transformer to a second impedance in the receive mode.

Abstract: A transceiver is described that includes a power amplifier (PA), a low noise amplifier (LNA), and an impedance matching circuit having a first and second differential output node. The first and second differential output nodes are coupled to outputs of the PA and to inputs of the LNA. The impedance matching circuit provides a load impedance to the outputs of the PA. The transceiver further includes a first impedance device having an output impedance coupled between the first and second differential output nodes. In this way, the combination of the output impedance and the load impedance matches with an impedance at the inputs of the LNA.

Abstract: A wireless terminal includes a housing (10) containing a substrate (12) having a ground plane, RF components mounted on the substrate, a PIFA (Planar Inverted-F Antenna) (16) carried by the substrate and coupled electrically to the RF components for transmitting and receiving signals and a notch antenna (14) in the substrate for receiving signals in a frequency band at least partially overlapping the transmission bandwidth of some of the signals transmitted by the PIFA. The notch antenna is de-activated when the PIFA (16) is being used for transmitting a signal lying within the said transmission bandwidth.

Abstract: A transmitter circuit, a receiver circuit and an interface switching module for SATA or SAS interface are provided. The invention uses transistors as elements with different impedance and also provides impedance modulating method in coordination with the exterior circuit and the layout design so as to develop an auto-switching mechanism between SATA and SAS interfaces, thereby integrating two transmission interfaces in a single system.

Abstract: A matching network for matching an antenna to a transmitter or receiver comprises an input port for receiving high-frequency power, an output port and a switchable impedance transformation circuit, which is connected between the input port and the output port. The impedance transformation circuit comprises a CMOS switch in a high-frequency path, which has a first switching state and a second switching state. The impedance transformation circuit is implemented to match a first impedance applied to the output port to a first predetermined impedance in the first switching state, and to match a second impedance applied to the output port to a second predetermined impedance in the second switching state. The inventive matching network allows a particularly good utilization of power provided by a transmitting amplifier or an antenna.

Abstract: The invention refers to a circuit and a method for detecting the impedance of a load, whereby the circuit and the method can be used by an impedance matching circuit. Impedance matching circuits need a complex algorithm to adjust the impedance accordingly. This algorithm renders the response time to be long. It has been found out that the complexity partially stems from the fact that the phase of the reflection coefficient is not known over the full range of 0° to 360°. A quadrature phase detector is used to provide the full phase information.

Abstract: Method and apparatus for high-efficiency radio frequency (RF) power amplification. A method high-efficiency RF power amplification comprises receiving control and power signals, sampling power output of a main stage amplifier, comparing sampled amplifier output power with output power requirement information, reconfiguring bias of the cascaded amplifiers based on power adjustment information, coupling the output of a main stage power amplifier to a load mismatch protection circuit. An electronic apparatus for a Doherty-type high-efficiency RF power amplifying subsystem comprising a power interface circuit coupled to a bias network control circuit, an output power sampling circuit, the comparator comparing signal representing amplifier output power with the power control signal, the bias network control circuit adapts bias condition of the amplifier block, a load mismatch protection circuit provides well-controlled load, thereby the amplifier block amplifies RF input signal transmitted to the subsystem output.

Abstract: A multi-coupler system for isolating radio signals in a transceiver, that includes a transmitter and a receiver, to permit simultaneous transmit by the transmitter and receive by the receiver through a single antenna in the exact same or nearby frequency ranges. This is done so that in-coming receive signals, transmitted from a remotely located radio, being detected by the receiver is much stronger than the portion of the transmit signal unintentionally coupled over by the co-site (or co-located) transmitter. The invention uses a special electronic circuit, termed the quasi-circulator, to couple the antenna to both the co-located receiver and the transmitter. The invention can also be used to couple several transceivers to a single antenna. The quasi-circulator circuit includes a simulated antenna load with an impedance matched to the antenna impedance.

Abstract: A filtering method, a transceiver and a transmitter are provided. The transmitter comprises a power amplifier amplifying an RF signal and having multiple stages, and a local oscillator, the power amplifier comprising between at least two stages of the power amplifier an impedance circuitry for forming an impedance at a frequency related to the frequency of the local oscillator, and a switch for switching the impedance of the impedance circuitry means to RF frequency.

Abstract: An antenna for suppressing harmonics of a signal transmitted from the antenna, the signal having a carrier with an imposed modulated data signal, the antenna including a modulator associated with a controlled variable impedance in series, the modulator being operable to modulate in accordance with the data signal, and being configured to produce a voltage across the antenna corresponding to a voltage provided by the controlled variable impedance.

Abstract: A transmitting arrangement includes a matching circuit, a reference circuit and a comparator. The output of the matching circuit can be coupled to an antenna and comprises an adjustable impedance. The reference circuit is connected to an input of the matching circuit and comprises a reference impedance. Inputs of the comparator are coupled to the matching circuit and the reference circuit and its output is coupled to the adjustable impedance via a control input of the matching circuit.

Abstract: A variable frequency amplifier suffering less deterioration of strain characteristic and capable of operating at plural frequencies is disclosed. In one aspect, a changeable amplifier comprises an amplifying element, a changeable matching circuit disposed at an input side of the amplifying element and including a first variable capacity element connected in series with a signal conductor and a second variable capacity element connected in parallel with the signal conductor, and a control circuit for controlling the changeable matching circuit. Based on a feedback signal, the control circuit applies DC bias voltages to the first variable capacity element and the second variable capacity element of the changeable matching circuit and also applies thereto a correction signal.

Abstract: An apparatus and method for transmitting/receiving a signal in a communication system with a plurality of antennas are provided. Received modulation symbols of channel coded transmission information data are generated using a space-time mapping scheme and processed to RF symbols. The RF symbols are transmitted through antennas among the plurality of antennas.

Abstract: Disclosed is a multi-band antenna device with a simplified design and fabrication method, which can be suitably mounted to a mobile phone, or the like. The disclosed antenna device includes a substrate, and an antenna element connected to a feed point of the substrate. The antenna element includes a right-left asymmetrical first antenna element, and a second antenna element mounted to the first antenna element, which are integrally formed, and is provided on the surface of a dielectric substance. The antenna device can be embedded in the terminal while obtaining a good VSWR value over a wide-band by the first antenna element. Also, in the antenna device, in a low frequency band which cannot be covered by the first antenna element, it is possible to obtain a good VSWR value by the second antenna element.