Abstract: A radar system includes a transmitter stage for generating a certain transmission signal; a circularly polarized antenna for emitting the transmission signal in a form of a circularly polarized signal, and receiving a reflection signal; a polarizer for isolating the reflection signal received from the circularly polarized antenna from the transmission signal, and outputting the reflection signal to a next stage; and a receiver stage for receiving the reflection signal output from the polarizer, converting the reflection signal into a signal of a certain frequency by using as a certain mixer switching signal the leakage signal leaking from the transmitter stage, and outputting the converted reflection signal. Therefore, the high-sensitivity radar system can be built in a compact size.

Abstract: A small-sized on-chip complementary metal-oxide semiconductor (CMOS) Power Amplifier having improved efficiency is provided herein. The on-chip CMOS power amplifier is capable of improving efficiency and maximizing output thereof by enhancing a K factor, which may cause a problem in a power amplifier having a distributed active transformer structure. The on-chip CMOS power amplifier having an improved efficiency and being fabricated in a small size, the on-chip CMOS power amplifier includes a primary winding located at a first layer, secondary windings located at a second layer, which is an upper part of the first layer, the secondary windings being located corresponding to a position of the primary winding, and a cross section for coupling the second windings with each other.

Abstract: A radar system includes a transmitter stage for generating a certain transmission signal; a circularly polarized antenna for emitting the transmission signal in a form of a circularly polarized signal, and receiving a reflection signal; a polarizer for isolating the reflection signal received from the circularly polarized antenna from the transmission signal, and outputting the reflection signal to a next stage; and a receiver stage for receiving the reflection signal output from the polarizer, converting the reflection signal into a signal of a certain frequency by using as a certain mixer switching signal the leakage signal leaking from the transmitter stage, and outputting the converted reflection signal. Therefore, the high-sensitivity radar system can be built in a compact size.

Abstract: A small-sized on-chip complementary metal-oxide semiconductor (CMOS) Power Amplifier having improved efficiency is provided herein. The on-chip CMOS power amplifier is capable of improving efficiency and maximizing output thereof by enhancing a K factor, which may cause a problem in a power amplifier having a distributed active transformer structure. The on-chip CMOS power amplifier having an improved efficiency and being fabricated in a small size, the on-chip CMOS power amplifier includes a primary winding located at a first layer, secondary windings located at a second layer, which is an upper part of the first layer, the secondary windings being located corresponding to a position of the primary winding, and a cross section for coupling the second windings with each other.

Abstract: A radar system using a quadrature signal includes a quadrature push—push oscillator for generating four harmonics with a 90-degree phase difference from each other, and producing two-balanced 2nd harmonic signals from the harmonics; a first coupler block for radiating one of the 2nd harmonics through an antenna; a second coupler block for terminating the other 2nd harmonic to ground; and a power combiner for combining a transmitted signal that is leaked from the first and second coupler blocks with the received signal that is radiated through the antenna. The radar system features an improved receiving sensitivity by offsetting the leakage signals of the sending end. Also, the radar system can be made very small by using a single antenna for transmitting and receiving.

Abstract: A radar system using a quadrature signal includes a quadrature push-push oscillator for generating four harmonics with a 90-degree phase difference from each other, and producing two-balanced 2nd harmonic signals from the harmonics; a first coupler block for radiating one of the 2nd harmonics through an antenna; a second coupler block for terminating the other 2nd harmonic to ground; and a power combiner for combining a transmitted signal that is leaked from the first and second coupler blocks with the received signal that is radiated through the antenna. The radar system features an improved receiving sensitivity by offsetting the leakage signals of the sending end. Also, the radar system can be made very small by using a single antenna for transmitting and receiving.

Abstract: Disclosed is a method for manufacturing a hetero junction bipolar transistor capable of forming a ledge by using a low-priced contact aligner and in a selective wet etching manner, without having any expensive stepper and dry etching and forming a ballasting resistor, without having an additional NiCr thin film, whereby the manufacturing processes thereof can be embodied in simple and easy manners, thereby improving productivity and an economical efficiency.

Abstract: The present invention relates to a circuit for controlling waveform distortion resulting from nonlinearity of the impedance of a control terminal (gate or base) capacitance of a transistor, which can be employed in circuits showing a nonlinearity performance of high frequency amplifier or oscillator. According to the circuit of the invention, the waveform distortion can be properly controlled to improve the efficiency of power conversion in a high frequency circuit employing FET, regardless of the frequency band, while assuring a favorable matching of input for the circuit. Also, it can provide the reliability of an integrated circuit by employing outside voltage control circuit. Moreover, it can be fabricated on a wafer substrate of FET circuit with an inexpensive cost, which affords unrestricted designing of the circuit.

Abstract: The present invention relates to an optical coupler 2.times.2 optical switch which can efficiently shorten the length of device by employing a cantilever and a movable optical waveguide and a method for optical switching with the optical coupler 2.times.2 optical switch. An optical coupler 2.times.2 optical switch of the present invention comprises: an optical coupler in which two fixed optical waveguides are provided on a substrate; an optical waveguide positioned between the fixed optical waveguides, which is moved up and down; and, a cantilever which is linked to the optical waveguide to move the optical waveguide up and down by the voltage applied to electrodes. Since the coupling length of the optical coupler(22) is changed depending on the distance between the fixed optical waveguides(21, 21') and the optical waveguide(23), length(D) of the optical, coupler(22) can be shortened to a great extent compared to the prior art optical coupler 2.times.

Abstract: The present invention relates to an optical coupler sensor employing a fixed optical waveguide and a movable optical waveguide which allows detection of every small physical quantities and their changes with a high sensitivity, and a process for preparing the same. The optical coupler sensor of the present invention comprises: a fixed optical waveguide formed on a substrate and disposed along a predetermined path. A movable optical waveguide is linked to a cantilever formed on the substrate, which is moved up and down by an external force. The moveable waveguide is disposed outside of the predetermined path.

Abstract: An area-variable varactor diode is disclosed, in which the capacitance can be arbitrarily varied under an applied bias voltage. The area-variable varactor diode is characterized in that, in order to ensure freedom to designing the epi-layer, to obtain the desired capacitance characteristics, and to facilitate the integration with other elements, a steeply varied depletion layer area is provided through a variation of the surface layout area, and thus, varied capacitance characteristics are obtained. In steeply varying the area of the depletion layer, an etching of the active layer, a selective epi-layer growth, and an ion implantation are carried out or a combination of them is carried out. The capacitance characteristics are varied in accordance with the pattern of the mask, and therefore, a restriction is not imposed on the epi-layer, with the result that an integration with other elements becomes easy.