Abstract: A signal receiving apparatus according to an embodiment of the present invention includes: an amplifier that controls a gain according to a gain control signal and amplifies a received signal to generate an amplified signal; an analog-to-digital (A/D) converter that converts the amplified signal into a digital signal; a Fourier transform unit that performs Fourier transform of the digital signal to a frequency domain signal to generate a Fourier transform signal; a demodulator that demodulates the Fourier transform signal to generate a demodulated signal; and an automatic gain control unit that divides the Fourier transform signal into a noise period and a symbol period, calculates the signal level of the noise period based on the signal level of the symbol period, and generates the gain control signal according to the signal levels of the symbol period and the noise period.

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: Provided is an apparatus and method for controlling power in a mobile communication system. The apparatus includes a moving speed measuring unit for measuring a moving speed of the terminal, a Channel Quality Indicator (CQI) processing unit for requesting a base station to adjust a CQI report frequency when the moving speed measured by the moving speed measuring unit exceeds a threshold value, and determining a CQI report frequency based on information on the CQI report frequency received from the base station to report CQI, and a power controller for performing a power control in response to a power control signal created by the CQI reported from the base station.

Abstract: The present invention relates to a scalable bandwidth system and a method of controlling a tunable filter. In the present invention, the scalable bandwidth system inputs, as a control signal of a tunable filter, a voltage corresponding to a section in which the capacitance according to an applied voltage is not practically changed for characteristics of varactor diodes, and inputs each control bit of the control signal to each varactor diode of the tunable filter to adjust the capacitance of each of the varactor diodes, and consequently adjusts the capacitance of the tunable filter by adding the capacitance of the varactor diodes.

Abstract: There is provided a windmill-shaped loop antenna including: a dielectric substrate; a first radiation unit disposed on a top surface of the dielectric substrate and including a metal pattern having loop pieces; a second radiation unit disposed at a bottom surface of the dielectric substrate and including a metal pattern having loop pieces arranged not to face the loop pieces of the first radiation unit; and a plurality of identical transmission line from a center of the top and bottom surfaces of the dielectric substrate to the first and second radiation units, which form windmill-shaped metal pattern with the first and second radiation unit.

Abstract: The present invention relates to transmitting/receiving apparatuses of a wideband radio channel measuring device using a multi-carrier. The wideband radio channel measuring device using the multi-carrier may measure radio channel characteristics at a frequency domain. Since the radio channel is measured at the frequency domain by the wideband radio channel measuring device using the multi-carrier, the channel characteristics may be simultaneously measured while maintaining a maximum Doppler measurement frequency at a predetermined level regardless of increase of the number of transmitting and receiving antennas, in an MIMO configuration.

Abstract: A transmitting apparatus according to the present invention includes a prefilter for compensating a previously measured estimated impulse response of a communication system by assuming a communication system in which the transmitting apparatus and the receiving apparatus are directly connected. The prefilter included in the transmitting apparatus compensates an original characteristic of a communication system. Accordingly, the prefilter enables an accurate channel measurement of a receiving apparatus without any increase of calculation.

Abstract: Provided is a wired Multiple-Input Multiple-Output (MIMO) link tester. The wired link tester, includes: a simulating unit for constructing a wired link corresponding to a wireless link for a multiple-input multiple-output system and simulating wireless-link characteristics using each variable element located on the wired link; and a control means for prestoring a predetermined value of the variable element depending on the state change time and the number of the state changes and controlling the variable element according to the predetermined value of the variable element.

Abstract: Provided are a method for measuring a variable bandwidth wireless channel, and a transmitter and a receiver therefor. The transmitter, includes: a pre-processing unit for performing variable over-sampling and band-limited filtering on an original sequence for measuring the wireless channel according to a pre-determined digital-to-analog (D/A) operation speed and measurement bandwidth, and creating and storing a probing sequence whose frequency is up-converted into a fixed transmitting intermediate frequency; and a real-time processing unit for transmitting a probing signal that the stored probing sequence is converted according to the D/A operation speed to the wireless channel.

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: 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: Provided are a PLL apparatus for an OFDM system having variable channel band and an operating method thereof. The PLL apparatus includes a frequency divider for dividing an oscillating signal; a phase detector for detecting a phase difference between a reference signal and the divided oscillating signal from the frequency divider and outputting the phase difference signal; a variable loop filter for filtering a phase difference signal outputted from the phase detector; a voltage control oscillator for outputting the oscillator signal to the frequency divider according to the voltage control signal filtered from the variable loop filter; and a variable loop filter controller for varying a filtering band of the variable loop filter according to each of the channel bands.

Abstract: Provided are an apparatus for receiving multi-band signals of multiple modes and a method thereof. The apparatus includes a radio frequency (RF) pre-processing unit for receiving and pre-processing a RF input; a low noise amplifier (LNA) coupled to the RF pre-processing unit; an in-phase/quadrature-phase (IQ) frequency down-converter coupled to the LNA; a low pass filter (LPF) coupled to the IQ frequency down-converter; an analog-to-digital converter (ADC) coupled to the LPF; a complex frequency down-convertor for changing a digital local oscillation frequency based on a variation of center frequency of multi-mode baseband IQ signals converted in the ADC and converting multi-mode baseband IQ signals into baseband IQ signals of each mode; a variable digital filter for low-pass filtering the baseband IQ signals of each mode based on digital filter coefficients for filtering through a predetermined bandwidth; and a baseband signal processor for demodulating the baseband IQ signals of each mode.

Abstract: A receiver is protected by reducing a transmit leakage signal leaked when a transmit signal is radiated through the antenna by using three circulators (transmitter, antenna, and receiver). The transmitter and antenna circulators output the transmit leakage signal to be reduced to less than the transmit signal through a first leakage path. The transmitter and receiver circulators output the transmit leakage signal through a third leakage path and reduce the signal. The transmit leakage signals received through the first and third leakage paths are canceled, and that received through a second leakage path is output to a receiver. The transmit leakage signal has a 40 dB signal reduction compared to the transmit signal, and is transmitted to the receiver.

Abstract: A stub printed antenna (SPDA) and a method of designing the same are provided. The SPDA include: a substrate; dipole arms disposed at both surfaces of the substrate for transmitting/receiving a signal; a parallel metal strip line disposed at both surfaces of the substrate, and each having one end connected to each of the dipole arms; a stub disposed at both surfaces of the substrate, and connected to the other end of the parallel metal strip line; a coaxial probe connected to the junction of the parallel metal strip line and the stub for feeding signals; a hole for inserting an inner conductor of the coaxial probe; and a contact for connecting to an outer conductor of the coaxial probe.

Abstract: There is provided a windmill-shaped loop antenna including: a dielectric substrate; a first radiation unit disposed on a top surface of the dielectric substrate and including a metal pattern having loop pieces; a second radiation unit disposed at a bottom surface of the dielectric substrate and including a metal pattern having loop pieces arranged not to face the loop pieces of the first radiation unit; and a plurality of identical transmission line from a center of the top and bottom surfaces of the dielectric substrate to the first and second radiation units, which form windmill-shaped metal pattern with the first and second radiation 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: The present invention relates to a method for increasing accuracy for estimating a multiple input multiple output (MIMO) channel. In the method, a maximum delay spread of a channel is estimated by using a Gold code or a Kasami code, a loosely-synchronous (LS) code having an appropriate interference free window (IFW) is selected, and the MIMO channel without any interference is accurately estimated.

Abstract: A stub printed antenna (SPDA) and a method of designing the same are provided. The SPDA include: a substrate; dipole arms disposed at both surfaces of the substrate for transmitting/receiving a signal; a parallel metal strip line disposed at both surfaces of the substrate, and each having one end connected to each of the dipole arms; a stub disposed at both surfaces of the substrate, and connected to the other end of the parallel metal strip line; a coaxial probe connected to the junction of the parallel metal strip line and the stub for feeding signals; a hole for inserting an inner conductor of the coaxial probe; and a contact for connecting to an outer conductor of the coaxial probe.