Abstract: A resonant circuit including a resonator provided on the surface of a circuit board and a main line connected to a negative resistance circuit. The resonator is structured such that a resonant electrode is formed on a dielectric substrate, and a coupling electrode coupled to the resonant electrode is provided on the dielectric substrate. A branch line extends toward the resonator from a main line, and bonding wires are used to connect a leading end of the branch line and the coupling electrode. With this structure, it is possible to use the branch line to shift an unnecessary resonant frequency due to the ground capacitance of the coupling electrode and the inductance of the bonding wires toward a frequency band lower than the resonant frequency of the resonator.

Abstract: In a wireless communication apparatus which has the functions of both ASK modulation and QPSK modulation, which can be manufactured at a low cost, and which is small in size, an output terminal of a QPSK modulator is connected to a carrier wave input terminal of an ASK modulator via a switch. Also, an antenna is connected to an output terminal of the ASK modulator via a switch. Furthermore, a mixer is provided between the switches and. The switch connects the QPSK modulator and the ASK modulator at the time of a transmission, whereas it connects the QPSK modulator and the mixer at the time of a reception. The switch connects the ASK modulator and the antenna at the time of a transmission, whereas it connects the antenna and the mixer at the time of a reception. Thus, at the time of a transmission, an ASK-modulated wave or a QPSK-modulated wave is output using the ASK modulator and the QPSK modulator.

Abstract: A ground electrode and a terminal electrode are formed on a first main surface of dielectric substrate forming a circuit board. Wiring electrodes are formed on a second main surface of the dielectric substrate. A semiconductor device and a filter are mounted on the wiring electrodes. A strip line electrode of the filter is connected to the ground electrode of the circuit board for conducting direct current, via a through-hole provided in the filter, a ground electrode of the filter, the wiring electrode, and a through-hole provided in the circuit board. With this arrangement, the terminal electrode is connected to a high-frequency signal terminal of the semiconductor device via the filter.

Abstract: A resonance type SPST switch is formed by connecting an inductive element in series with the drain of an FET, and then by connecting a capacitive element in parallel with the series connection of the FET and the inductive element. A constant-voltage source for feeding a voltage Vs is connected to the source of the FET, and a variable-voltage generator for switching the FET between an on state and a state in the vicinity of pinchoff is connected to the gate of the FET. When the variable-voltage generator feeds a voltage V&agr; in the vicinity of a pinchoff voltage to the gate of the FET, the SPST switch is closed while the amount of attenuation between first and second terminals is variably set. The resulting variable attenuator is thus compact in size, allows a large amount of attenuation to be set, and involves low manufacturing costs.

Abstract: A field effect transistor (FET) is formed on a semiconductor substrate. A drain terminal, a source terminal, and a gate terminal connected to the FET are also formed on the semiconductor substrate. In an embodiment of the invention, a metal insulator metal (MIM) capacitor for blocking a bias current is disposed between the FET and the drain terminal. A bias terminal is provided between the MIM capacitor and the FET. Passive circuits connected to the drain terminal, the source terminal, and the gate terminal, and a bias circuit connected to the bias terminal are formed on a dielectric substrate. With this arrangement, the circuitry on the semiconductor substrate can be simplified. The general versatility of a resulting semiconductor device can be increased, and the size of the semiconductor device can be reduced.

Abstract: An SPDT switch used for a communication unit includes first and second terminals, a common terminal, and first and second FETs with Schottky connection gates. The drain of the first FET is connected to the first terminal, and the source of the second FET is connected to the second terminal. The source of the first FET and the drain of the second FET are directly connected to each other, and are then connected to the common terminal. The pinch-off voltage Vp1 of the first FET is set to satisfy 0 >Vp1>&agr;−&ggr;, and the pinch-off voltage Vp2 of the second FET is set to satisfy 0 >Vp2>&ggr;−&bgr;, where &agr;<&ggr;<&bgr;. A fixed potential &ggr; is applied to the gate of the second FET, and one of potentials &agr; and &bgr; is applied to the gate of the first FET, so that one of the first and second terminals can be electrically connected to the common terminal. Additional resonance and/or switching elements may be included as well.

Abstract: A field effect transistor (FET) is formed on a semiconductor substrate. A drain terminal, a source terminal, and a gate terminal connected to the FET are also formed on the semiconductor substrate. In an embodiment of the invention, a metal insulator metal (MIM) capacitor for blocking a bias current is disposed between the FET and the drain terminal. A bias terminal is provided between the MIM capacitor and the FET. Passive circuits connected to the drain terminal, the source terminal, and the gate terminal, and a bias circuit connected to the bias terminal are formed on a dielectric substrate. With this arrangement, the circuitry on the semiconductor substrate can be simplified. The general versatility of a resulting semiconductor device can be increased, and the size of the semiconductor device can be reduced.

Abstract: In a wireless communication apparatus which has the functions of both ASK modulation and QPSK modulation, which can be manufactured at a low cost, and which is small in size, an output terminal (5D) of a QPSK modulator (5) is connected to a carrier wave input terminal (1A) of an ASK modulator (1) via a switch (15). Also, an antenna (4) is connected to an output terminal (1C) of the ASK modulator (1) via a switch (16). Furthermore, a mixer (13) is provided between the switches (15) and (16). The switch (15) connects the QPSK modulator (5) and the ASK modulator (1) at the time of a transmission, whereas it connects the QPSK modulator (5) and the mixer (13) at the time of a reception. The switch (16) connects the ASK modulator (1) and the antenna (4) at the time of a transmission, whereas it connects the antenna (4) and the mixer (13) at the time of a reception. Thus, at the time of a transmission, an ASK-modulated wave or a QPSK-modulated wave is output using the ASK modulator (1) and the QPSK modulator (5).

Abstract: A resonance type SPST switch is formed by connecting an inductive element in series with the drain of an FET, and then by connecting a capacitive element in parallel with the series connection of the FET and the inductive element. A constant-voltage source for feeding a voltage Vs is connected to the source of the FET, and a variable-voltage generator for switching the FET between an on state and a state in the vicinity of pinchoff is connected to the gate of the FET. When the variable-voltage generator feeds a voltage V&agr; in the vicinity of a pinchoff voltage to the gate of the FET, the SPST switch is closed while the amount of attenuation between first and second terminals is variably set. The resulting variable attenuator is thus compact in size, allows a large amount of attenuation to be set, and involves low manufacturing costs.

Abstract: An SPST switch having a small transmission loss and a small power consumption is provided. The drain and the source of an FET are connected to each other in series through an induction element and a capacitor element, one terminal of the capacitor element is connected to a first terminal, the other terminal is connected to a second terminal, the gate of the FET is connected to a control terminal, the capacitance of the capacitor element is made equal to the OFF capacitance of the FET, and the inductance of the induction element is set to be such a value that the induction element resonates at a signal frequency with the capacitor element.

Abstract: A ground electrode and a terminal electrode are formed on a first main surface of dielectric substrate forming a circuit board. Wiring electrodes are formed on a second main surface of the dielectric substrate. A semiconductor device and a filter are mounted on the wiring electrodes. A strip line electrode of the filter is connected to the ground electrode of the circuit board for conducting direct current, via a through-hole provided in the filter, a ground electrode of the filter, the wiring electrode, and a through-hole provided in the circuit board. With this arrangement, the terminal electrode is connected to a high-frequency signal terminal of the semiconductor device via the filter.

Abstract: An SPST switch having a small transmission loss and a small power consumption is provided. The drain and the source of an FET are connected to each other in series through an induction element and a capacitor element, one terminal of the capacitor element is connected to a first terminal, the other terminal is connected to a second terminal, the gate of the FET is connected to a control terminal, the capacitance of the capacitor element is made equal to the OFF capacitance of the FET, and the inductance of the induction element is set to be such a value that the induction element resonates at a signal frequency with the capacitor element.

Abstract: An ASK modulator can be operated with only a positive-voltage power source. A source-voltage switching circuit that applies a positive voltage to the source of a FET when a data signal is at an L level in relation to the source of the FET is connected to the source of the FET which has a negative pinch-off voltage. Since the L level of the data signal can be set to 0 V, the ASK modulator can be configured only with the positive-voltage power source. This allows miniaturization and cost reduction to be implemented.

Abstract: An SPST switch having a small transmission loss and a small power consumption is provided. The drain and the source of an FET are connected to each other in series through an induction element and a capacitor element, one terminal of the capacitor element is connected to a first terminal, the other terminal is connected to a second terminal, the gate of the FET is connected to a control terminal, the capacitance of the capacitor element is made equal to the OFF capacitance of the FET, and the inductance of the induction element is set to be such a value that the induction element resonates at a signal frequency with the capacitor element.

Abstract: An electronic blood pressure meter capable of performing a proper automatic pressuring operation according to a blood pressure of a subject and measuring the blood pressure rapidly with accuracy.