Abstract: In making an airbridge structure, a second resist layer is applied over a first resist layer. The resist layers are exposed and developed to have a predetermined width W2. A third resist layer is applied. The third resist layer is also exposed and developed to have a predetermined width W3. An airbridge-forming material layer is applied to the layer stack structure consisting of the first, second, and third resist layers, forming an airbridge. The resist layers are removed, completing the manufacture of the airbridge, which has a stepped cross section.

Abstract: A method for manufacturing a semiconductor device comprises: forming a circuit pattern and a first metal film on a first major surface of a body wafer; forming a through-hole penetrating the body wafer from a second major surface of the body wafer and reaching the first metal film; forming a second metal film on a part of the second major surface of the body wafer, on an inner wall of the through-hole, and on the first metal film exposed in the through-hole; forming a recess on a first major surface of a lid wafer; forming a third metal film on the first major surface of the lid wafer including inside the recess of the lid wafer; with the recess facing the circuit pattern, and the first metal film contacting the third metal film, joining the lid wafer to the body wafer; and dicing the joined body wafer and lid wafer along the through-hole.

Abstract: A high frequency second harmonic oscillator includes a transistor, a first signal line connected at a first end to the base or gate of the transistor, a first shunt capacitor connected at a first end to a second end of the first signal line and at a second end to ground, a second signal line connected at a first end to the collector or drain of the transistor, a second shunt capacitor connected at a first end to a second end of the second signal line and at a second end to ground, and a high capacitance capacitor connected between the first signal line and the second signal line. The first signal line has a length equal to an odd integer multiple of one quarter of the wavelength of a fundamental signal, plus or minus one-sixteenth of the wavelength of the fundamental signal.

Abstract: Provided is an even harmonic mixer which is reduced in cost and size. The even harmonic mixer includes: a transducer in which a conductor of a microstrip line is connected to a ground plane of a waveguide, for transducing an RF signal transmitted in a waveguide mode into a transmission mode of the microstrip line; an anti-parallel diode pair which is cascade-connected to a microstrip line side of the transducer, and formed on a semiconductor substrate; a branching circuit for branching an LO signal and an IF signal; an open-end stub which is disposed between the transducer and the anti-parallel diode pair, and has a line length of about ½ wavelength at an RF signal frequency; and an open-end stub which is disposed between the anti-parallel diode pair and the branching circuit, and has a line length of about ¼ wavelength at the RF signal frequency.

Abstract: A transmitter and receiver circuit includes antennas for receiving high-frequency signals; a local oscillator for generating local oscillation signals; mixers connected to respective antennas for converting the frequency of the high-frequency signals from corresponding antennas in response to the high-frequency signals input from the local oscillator; and a switch for inputting the local oscillation signals generated by the local oscillator into a selected one of the mixers so that receiving channels are switched by the switch.

Abstract: A high frequency power amplifier comprises: a multi-finger transistor with transistor cells electrically connected in parallel; an input side matching circuit connected to gate electrodes of the transistor cells; and resonant circuits respectively connected between the gate electrode of a transistor cell and the input side matching circuit. The resonant circuit resonates at a second harmonic of the operating frequency of the transistor or within a predetermined range of frequencies having a center at the second harmonic of the operating frequency, and becomes a high-impedance load at the second harmonic, or an open load.

Abstract: A two-terminal semiconductor device is formed on a semiconductor substrate. Two wiring patterns are respectively connected to terminals of the semiconductor device, and two electrode pads are respectively connected to the wiring patterns for connecting a signal input/output circuit formed on a separate substrate. Two parallel wiring patterns are respectively connected to the wiring patterns, and two reactance-circuit connection electrode pads are respectively connected to the parallel wiring patterns for electrically connecting a reactance circuit formed on the separate substrate separately from the signal input/output circuit.

Abstract: A cascode circuit for a high-gain or high-output millimeter-wave device that operates with stability. The cascode circuit including two cascode-connected transistors includes: a first high electron mobility transistor (HEMT) including a source that is grounded; a second HEMT including a source connected to a drain of the first HEMT; a reflection gain restricting resistance connected to the gate of the second HEMT, for restricting reflection gain; and an open stub connected to a side of the reflection gain restricting resistance which is opposite the side connected to the second HEMT, for short-circuiting high-frequency signals at a predetermined frequency and nearby frequencies.

Abstract: A cascode circuit for a high-gain or high-output millimeter-wave device that operates with stability. The cascode circuit including two cascode-connected transistors includes: a first high electron mobility transistor (HEMT) including a source that is grounded; a second HEMT including a source connected to a drain of the first HEMT; a reflection gain restricting resistance connected to the gate of the second HEMT, for restricting reflection gain; and an open stub connected to a side of the reflection gain restricting resistance which is opposite the side connected to the second HEMT, for short-circuiting high-frequency signals at a predetermined frequency and nearby frequencies.

Abstract: A voltage controlled oscillator having low phase noise and including: a variable resonator including a varactor and a control voltage terminal; and an open-end stub connected in parallel to the variable resonator, the open-end stub having a length shorter than or equal to an odd multiple of one quarter of a wavelength of a harmonic signal plus one sixteenth of the wavelength of the harmonic signal, and longer than or equal to an odd multiple of one quarter of the wavelength of the harmonic signal minus one sixteenth of the wavelength of the harmonic signal. In this structure, a high Q value is realized for a fundamental wave frequency. Fluctuation in a control voltage due to a harmonic signal is controlled.

Abstract: A high frequency power amplifier comprises: a multi-finger transistor with transistor cells electrically connected in parallel; an input side matching circuit connected to gate electrodes of the transistor cells; and resonant circuits respectively connected between the gate electrode of a transistor cell and the input side matching circuit. The resonant circuit resonates at a second harmonic of the operating frequency of the transistor or within a predetermined range of frequencies having a center at the second harmonic of the operating frequency, and becomes a high-impedance load at the second harmonic, or an open load.

Abstract: A mixer circuit includes: a rat race circuit including a ring-shaped transmission line with a first terminal, a second terminal, a third terminal, and a fourth terminal, the first to fourth terminals being disposed, in that order, clockwise along the transmission line and equally spaced ?LO/4 from one another, except that the first terminal is spaced 3*?LO/4 from the fourth terminal, where ?LO is the wavelength of the LO signal applied to the mixer circuit; an LO terminal connected to the first terminal; a first diode and a second diode connected in the same polarity to the second terminal and the fourth terminal, respectively; and an RF terminal and an IF terminal both connected to the third terminal. The frequency of the LO signal is one-half of the frequency of the RF signal applied to the mixer circuit.

Abstract: A mixer circuit includes: a rat race circuit including a ring-shaped transmission line with a first terminal, a second terminal, a third terminal, and a fourth terminal, the first to fourth terminals being disposed, in that order, clockwise along the transmission line and equally spaced ?LO/4 from one another, except that the first terminal is spaced 3*?LO/4 from the fourth terminal, where ?LO is the wavelength of the LO signal applied to the mixer circuit; an LO terminal connected to the first terminal; a first diode and a second diode connected in the same polarity to the second terminal and the fourth terminal, respectively; and an RF terminal and an IF terminal both connected to the third terminal. The frequency of the LO signal is one-half of the frequency of the RF signal applied to the mixer circuit.

Abstract: A transmitter and receiver circuit includes antennas for receiving high-frequency signals; a local oscillator for generating local oscillation signals; mixers connected to respective antennas for converting the frequency of the high-frequency signals from corresponding antennas in response to the high-frequency signals input from the local oscillator; and a switch for inputting the local oscillation signals generated by the local oscillator into a selected one of the mixers so that receiving channels are switched by the switch.

Abstract: A high frequency semiconductor integrated circuit includes a main circuit, a circuit block, a pad, and a wire. The main circuit includes an input terminal, a transistor, transmission lines, a pad, and an output terminal. The circuit block includes a passive circuit and a capacitor. The pad is disposed close to the circuit block. The wire connects the pad to the pad included in the main circuit. In the high frequency semiconductor integrated circuit, the main circuit outputs an input signal input at the input terminal from the output terminal through the transistor, the transmission line, the pad, and another transmission line. As a result, the high frequency semiconductor integrated circuit can realize various performances and can be used in many applications.

Abstract: A high frequency semiconductor integrated circuit includes a main circuit, a circuit block, a pad, and a wire. The main circuit includes an input terminal, a transistor, transmission lines, a pad, and an output terminal. The circuit block includes a passive circuit, and a capacitor. The pad is disposed close to the circuit block. The wire connects the pad to the pad included in the main circuit. In the high frequency semiconductor integrated circuit, the main circuit outputs an input signal inputted at the input terminal from the output terminal through the transistor, the transmission line, the pad and another transmission. As a result, the high frequency semiconductor integrated circuit can realize various kinds of its performances and thereby can be used to many applications.