Abstract: The present invention relates to a device for compensating a radio frequency distortion caused by a sample/hold operation of a digital/analog converter in an orthogonal frequency division multiplexing (OFDM) transmission system, and a method thereof. In a digital transmission system, an edge frequency signal of a transmission signal band is distorted by a sample/hold operation of a digital/analog converter such that a signal attenuation is generated at a frequency domain by a sync function having a zero point at a sample frequency of a transmission signal. In the present invention, the signal distortion may be compensated by multiplying a coefficient of an inverse sync function by a signal weight value at the frequency domain, and it may be compensated by using a single multiplier and a lookup table storing the coefficient of the inverse sync function.

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 gain control apparatus in a receiver of multiband OFDM system includes: an amplifier amplifying a received signal based on a first auto gain control signal; an analog-to-digital converter for converting the amplified signal into a digital signal; band reception signal extractor for extracting a signal of a desired reception band from the converted digital signal for each reception band, and controlling gain of the extracted signal according to a second auto gain control signal; a reception power detector for detecting a reception power value of whole band from the converted digital signal; and a multiband integration baseband processor for generating the first auto gain control signal by using the detected reception power value of the whole band, and generating the second auto gain control signal to be provided to the band reception signal extraction units, resource allocation information for each band and a reception power for each reception band.

Abstract: The present invention relates to an apparatus and a method for compensating carrier feedthrough in a quadrature modulation system. In order to suppress the carrier feedthrough, and minimize and compensate the carrier feedthrough, differences of baseband differential input DC voltages in an in-phase as well as a quadrature-phase are simultaneously adjusted to 0 or a certain slight voltage difference by a simple analog circuit. Therefore, it is possible to suppress carrier feedthrough using a simple analog type apparatus for compensating carrier feedthrough, and simply achieve an apparatus for carrier feedthrough using a variety of quadrature modulators.

Abstract: The present invention relates to an apparatus and a method for compensating carrier feedthrough in a quadrature modulation system. In order to suppress the carrier feedthrough, and minimize and compensate the carrier feedthrough, differences of baseband differential input DC voltages in an in-phase as well as a quadrature-phase are simultaneously adjusted to 0 or a certain slight voltage difference by a simple analog circuit. Therefore, it is possible to suppress carrier feedthrough using a simple analog type apparatus for compensating carrier feedthrough, and simply achieve an apparatus for carrier feedthrough using a variety of quadrature modulators.

Abstract: A radio signal receiving apparatus receiving a radio signal over a radio channel generates a first amplified signal by amplifying the radio signal with a first gain, and determines the first gain by measuring the strength of the first amplified signal. In addition, the radio signal receiving apparatus generates a down-converted signal by frequency down-converting the first amplified signal, and generates a second amplified signal by amplifying the down-converted signal with a second gain. In addition, the radio signal receiving apparatus determines the second gain by measuring the strength of the second amplified signal.

Abstract: The present invention relates to an RF repeater used in a time division method, and a method thereof. An RF repeater according to an exemplary embodiment of the present invention receives a downlink signal that is to be transmitted from a base station to a mobile terminal, performs first automatic gain control on the downlink signal, and extracts gain information from the downlink signal on which the first automatic gain control has been performed, on the basis of gain variation information that is the gain information for the downlink signal. Then, the RF repeater performs second automatic gain control on the downlink signal on the basis of the extracted gain information, and performs a control operation such that the downlink signal on which the second automatic gain control has been performed is transmitted to the mobile terminal.

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: Provided is a device for shaping a flat-topped element pattern using a circular polarization microstrip patch. The device includes: a microstrip patch feeding unit for generating circularly polarized signals of a basic mode; a circular waveguide for guiding the circular polarized signals and generating signals of high-order modes; and a pattern shaping unit for shaping FTEP through an electromagnetic mutual coupling between the signals of the high-order modes generated from the pattern shaping unit.

Abstract: The present invention relates to a device for compensating a radio frequency distortion caused by a sample/hold operation of a digital/analog converter in an orthogonal frequency division multiplexing (OFDM) transmission system, and a method thereof. In a digital transmission system, an edge frequency signal of a transmission signal band is distorted by a sample/hold operation of a digital/analog converter such that a signal attenuation is generated at a frequency domain by a sync function having a zero point at a sample frequency of a transmission signal. In the present invention, the signal distortion may be compensated by multiplying a coefficient of an inverse sync function by a signal weight value at the frequency domain, and it may be compensated by using a single multiplier and a lookup table storing the coefficient of the inverse sync function.

Abstract: Provided is an antenna control apparatus for controlling an antenna mounted on a stratospheric platform of the stratospheric communication system. The apparatus includes a plurality of location signal receivers, each receiver being positioned at each of predefined different points of the stratospheric platform and receiving a location signal for the stratospheric platform, a calculating circuit for calculating an adjustable displacement for the antenna, and an antenna driver for adjusting a direction of the antenna. The calculating circuit calculates a location and attitude of the stratospheric platform based on the location signals, and then computes the adjustable displacement using the location and attitude information. This invention can reduce power consumption in the stratospheric platform and recovery time of directional point of the beam.

Abstract: A hexagonal array structure of a dielectric rod for shaping a flat-topped element pattern (FTEP) is provided. The hexagonal structure of dielectric rods forming a flat-topped element pattern (FTEP) includes: a center element for forming a unit radiation pattern of the FTEP through an electromagnetic wave mutual coupling by receiving a polarization signal of a basic mode; a plurality of first ring elements arranged at vertexes of a regular hexagon based on the center element for forming the unit radiation pattern by electromagnetic wave mutual coupling with the center element and an electromagnetic wave; and a circular waveguide array supporting unit for supporting the center element and the plurality of first ring elements.

Abstract: An open loop resonator filter employed aperture on the ground plane is disclosed. The open loop resonator filter using apertures on the ground plane formed on the dielectric substrate, the open loop resonator filter including: one or more open loop resonators formed on a upper side of the dielectric substrate and implemented by microstrip lines; and one or more apertures formed on a predetermined area of the ground plane. The present invention can control the coupling coefficient of the open loop resonator without degrading the group delay characteristics by forming the aperture on the ground plane. Therefore, by forming the aperture on the ground plane, it is possible to design a filter having a wide bandwidth characteristic.

Abstract: Provided is a device for shaping a flat-topped element pattern using a circular polarization microstrip patch. The device includes: a microstrip patch feeding unit for generating circularly polarized signals of a basic mode; a circular waveguide for guiding the circular polarized signals and generating signals of high-order modes; and a pattern shaping unit for shaping FTEP through an electromagnetic mutual coupling between the signals of the high-order modes generated from the pattern shaping unit.

Abstract: Provided is an antenna control apparatus for controlling an antenna mounted on a stratospheric platform of the stratospheric communication system. The apparatus includes a plurality of location signal receivers, each receiver being positioned at each of predefined different points of the stratospheric platform and receiving a location signal for the stratospheric platform, a calculating circuit for calculating an adjustable displacement for the antenna, and an antenna driver for adjusting a direction of the antenna. The calculating circuit calculates a location and attitude of the stratospheric platform based on the location signals, and then computes the adjustable displacement using the location and attitude information. This invention can reduce power consumption in the stratospheric platform and recovery time of directional point of the beam.

Abstract: A hexagonal array structure of a dielectric rod for shaping a flat-topped element pattern (FTEP) is provided. The hexagonal structure of dielectric rods forming a flat-topped element pattern (FTEP) includes: a center element for forming a unit radiation pattern of the FTEP through an electromagnetic wave mutual coupling by receiving a polarization signal of a basic mode; a plurality of first ring elements arranged at vertexes of a regular hexagon based on the center element for forming the unit radiation pattern by electromagnetic wave mutual coupling with the center element and an electromagnetic wave; and a circular waveguide array supporting unit for supporting the center element and the plurality of first ring elements.

Abstract: A voltage controlled oscillator using a resonator having a photonic bandgap structure and a feedforward circuit is disclosed. The voltage controlled oscillator includes a resonation unit for resonating an oscillated signal by using a resonator having the photonic bandgap structure in order to increase a quality factor and an oscillation unit for controlling a phase of the oscillated signal by using the feedforward circuit in order to reduce phase noise. The present invention can reduce phase noise and increase efficiency of integration by using the photonic bandgap structure of a resonator and the feedforward circuit is used for maintaining high Q factor.

Abstract: An open loop resonator filter employed aperture on the ground plane is disclosed. The open loop resonator filter using apertures on the ground plane formed on the dielectric substrate, the open loop resonator filter including: one or more open loop resonators formed on a upper side of the dielectric substrate and implemented by microstrip lines; and one or more apertures formed on a predetermined area of the ground plane. The present invention can control the coupling coefficient of the open loop resonator without degrading the group delay characteristics by forming the aperture on the ground plane. Therefore, by forming the aperture on the ground plane, it is possible to design a filter having a wide bandwidth characteristic.