Abstract: An active balun for improving a phase matching characteristic includes a transistor part which has an input terminal receiving an input signal and first and second output terminals which output signals corresponding to the input signal, and a capacitance matching part provided on the side of one of the first and second output terminals which matches capacitances as seen from the first and second output terminals. The capacitance matching part may be composed of a transistor which bleeds a current from the one output terminal.

Abstract: A source coupled differential complementary Colpitts oscillator is described, which enables a differential oscillation and also can improve phase noise performance by source-coupling a complementary Colpitts oscillator using an inductor. A differential complementary Colpitts oscillator includes: a plurality of complementary Colpitts oscillators and a source coupler which couples a source node of the plurality of complementary Colpitts oscillators, enables the Colpitts oscillators to differentially oscillate.

Abstract: A radio frequency (RF) filter is provided which includes a band pass filter unit and an amplifying unit. If a signal having a frequency in a first band is input, the RF filter performs band pass filtering, and if a signal having a frequency in a second band is input, the RF filter performs an amplifying process. The RF filter can be used for various RF signal processing devices, such as digital broadcast receiving tuners.

Abstract: A quadrature signal generator capable of phase-tuning with respect to all of four generated quadrature signals. The quadrature signal generator includes four phase tuning units each having two input terminals, one receiving a differential signal, the other being grounded, and changing a phase of the differential signal to thereby generate quadrature signals. Accordingly, it is possible to tune phases of all the four generated quadrature signals. It is also possible to prevent the amplitude of quadrature signals from being deviated from a reference value.

Abstract: A frequency synthesizer for mixing reference frequencies using at least one control signal has a local oscillator, frequency dividers for dividing a frequency generated from the local oscillator and generating at least one control signal, and a single side band (SSB) mixer for mixing the reference frequencies, using the frequency generated from the local oscillator and the control signal. The frequency synthesizer has a simplified structure, and can easily mix reference frequency signals without a need for additional power.

Abstract: A frequency synthesizer in an ultra wide band (UWB) wireless communication system which transmits and receives data through multiband includes a frequency generation means which generates a plurality of frequency signals; and a frequency adjustment means which receives the plurality of frequency signals from the frequency generation means and generates center frequencies of all or part of sub-bands within the UWB through the frequency adjustment. Since all of the center frequencies of the sub-bands are generated, the utilization of the sub-bands can be enhanced for the wideband wireless communication. Furthermore, it is possible to enable the stable UWB communications by flexibly utilizing all of fourteen sub-bands since the sub-bands suffer less from the frequency interference in a complicated and variable wireless frequency environment.

Abstract: A source coupled differential complementary Colpitts oscillator is described, which enables a differential oscillation and also can improve phase noise performance by source-coupling a complementary Colpitts oscillator using an inductor. A differential complementary Colpitts oscillator includes: a plurality of complementary Colpitts oscillators and a source coupler which couples a source node of the plurality of complementary Colpitts oscillators, enables the Colpitts oscillators to differentially oscillate.

Abstract: A multi-input multi-frequency synthesizing apparatus and method for a multi-band radio frequency (RF) receiver. The frequency synthesizing apparatus may generate an output from a greater number of high frequency signals by using one multi-input single side band (SSB) mixer. The multi-input SSB mixer may generate a signal whose frequency is an addition of frequencies of two signals selected from a signal selection control unit, or a difference of frequencies therebetween. According to a circuit configuration of the multi-input SSB mixer, the signal selection control unit may select more than two signals.

Abstract: A fast mode switching frequency synthesizing apparatus and method for operating in low power consumption. In the frequency synthesizer, according to a mode control signal, an SSB mixer selectively generates and outputs a signal having a frequency which is identical to an input signal RF or outputs a signal having a frequency which is a synthesized frequency of the input signals RF and LO. Frequency synthesized signals having a frequency which is a sum of frequencies of the input signals RF and LO, or a difference of frequencies therebetween, may be generated by changing wiring of a path switch according to a phase control signal.

Abstract: Disclosed is a wideband polyphase filter using variable resistors and variable capacitors for correcting a phase and a frequency to be suitable for wideband communication. There is provided a wideband polyphase filter including: a variable resistor in which resistance varies; and a variable capacitor in which capacitance varies, wherein the variable resistor and the variable capacitor correct a wideband frequency and a phase, converts a predetermined differential input into a quadrature signal and outputs the converted quadrature signal. A wideband polyphase filter which varies resistance and capacitance to correct a phase and frequency, and also may obtain a wideband frequency range may be provided.

Abstract: A frequency synthesizer in an ultra wide band (UWB) wireless communication system which transmits and receives data through multiband includes a frequency generation means which generates a plurality of frequency signals; and a frequency adjustment means which receives the plurality of frequency signals from the frequency generation means and generates center frequencies of all or part of sub-bands within the UWB through the frequency adjustment. Since all of the center frequencies of the sub-bands are generated, the utilization of the sub-bands can be enhanced for the wideband wireless communication. Furthermore, it is possible to enable the stable UWB communications by flexibly utilizing all of fourteen sub-bands since the sub-bands suffer less from the frequency interference in a complicated and variable wireless frequency environment.

Abstract: A voltage controlled oscillator is provided. The oscillator has an oscillator amplifier core formed of a complementary pair of FETs connected with their gates in common and connected to share a bias current. An inductance is connected between the common gates and the common drains of the FETs. The inductance may be an inductor element or an inductance of a physical structure of the circuit, such as a bond wire. The voltage controlled oscillator includes a variable capacitor stage connected at the input of the oscillator amplifier stage and a buffer amplifier stage connected at the output of the oscillator amplifier stage. The buffer amplifier of one embodiment includes a pair of complementary FETs having common gates connected to the common drains of the FETs of the oscillator amplifier stage. The buffer amplifier stage also include an inductor and a capacitor connected between common drains of the buffer amplifier FETs and the output.

Abstract: A frequency synthesizer for mixing reference frequencies using at least one control signal has a local oscillator, frequency dividers for dividing a frequency generated from the local oscillator and generating at least one control signal, and a single side band (SSB) mixer for mixing the reference frequencies, using the frequency generated from the local oscillator and the control signal. The frequency synthesizer has a simplified structure, and can easily mix reference frequency signals without a need for additional power.

Abstract: A low noise amplifier (LNA) for ultra wide band recives and amplifies identical RF signals in different frequency bands, and includes more than one pair of narrow band LNAs coupled in parallel, and a load circuit which increases load impedance of the entire circuit of the narrow band LNAs. The LNA can not only amplify the RF signal in the UWB but also obtain the low noise and the high gain that are features of the conventional narrow band LNA.

Abstract: A quadrature signal generator capable of phase-tuning with respect to all of four generated quadrature signals. The quadrature signal generator includes four phase tuning units each having two input terminals, one receiving a differential signal, the other being grounded, and changing a phase of the differential signal to thereby generate quadrature signals. Accordingly, it is possible to tune phases of all the four generated quadrature signals. It is also possible to prevent the amplitude of quadrature signals from being deviated from a reference value.

Abstract: A voltage controlled oscillator is provided. The oscillator has an oscillator amplifier core formed of a complementary pair of FETs connected with their gates in common and connected to share a bias current. An inductance is connected between the common gates and the common drains of the FETs. The inductance may be an inductor element or an inductance of a physical structure of the circuit, such as a bond wire. The voltage controlled oscillator includes a variable capacitor stage connected at the input of the oscillator amplifier stage and a buffer amplifier stage connected at the output of the oscillator amplifier stage. The buffer amplifier of one embodiment includes a pair of complementary FETs having common gates connected to the common drains of the FETs of the oscillator amplifier stage. The buffer amplifier stage also include an inductor and a capacitor connected between common drains of the buffer amplifier FETs and the output.