Abstract: A matching circuit including a main matching block 51 inserted in a signal path and a series matching block 522, one end of which is connected to the main matching block 51, in which one end of a series connection of a switch 542 and a parallel matching block 532 is connected to the signal path at the other end of the series matching block 522 and impedance matching between input/output is performed at any one of two frequencies by setting the switch to ON/OFF.

Abstract: A signal switching device including a plurality of transmission paths connected to an input path, the signal switching device outputting a signal from the input path through one of the transmission paths, including a first variable impedance unit connected to a first transmission path, the first variable impedance unit including a first section formed from a superconducting material, the first section being set to a non-superconducting state when the signal is to be output through a second transmission path, the first section including a portion of a predetermined length at an input end, the portion having an area of a cross section less than an area of a cross section of the first section at an output end.

Abstract: A signal switching device is disclosed that is capable of transmitting signals with less signal loss while securing a good isolation characteristic. The signal switching device includes a first section formed from a superconducting material connected to a first transmission path. The first section has a smaller cross section at the input end than at the output end or, the signal switching device may include a first section formed from a superconducting material connected to a first transmission path in series, and a second section formed from a superconducting material connected to a second transmission path in parallel. The cross section of the second section is smaller than that of the second transmission path. The length of the second transmission path is determined in such a way that an input impedance of the second transmission path is sufficiently large when the second section is in a superconducting state.

Abstract: A signal switching device including a plurality of transmission paths connected to an input path, the signal switching device outputting a signal from the input path through one of the transmission paths, including a first variable impedance unit connected to a first transmission path, the first variable impedance unit including a first section formed from a superconducting material, the first section being set to a non-superconducting state when the signal is to be output through a second transmission path, the first section including a portion of a predetermined length at an input end, the portion having an area of a cross section less than an area of a cross section of the first section at an output end.

Abstract: A plurality of one-quarter wavelength coplanar resonators 5a to 5d are formed in series on a dielectric substrate 1, and coplanar input/output terminal sections 4a and 4b are formed on the dielectric substrate at opposite ends of the series connection for coupling with resonators 5a and 5d, respectively. A center conductor line width w1 of each of the resonators 5a to 5d is equal to a center conductor line width wio of each of the input/output terminal section 4a and 4b, but a ground conductor spacing d1 of each of the resonators 5a to 5d is greater than a ground conductor spacing dio of each of input/output terminal section 4a and 4b. Maintaining the accuracy of design is facilitated and a reduction in the maximum current density in the resonator is enabled.

Abstract: A filter is provided which maintains a low insertion loss characteristic of a filter contained in a casing with a very simple construction that the internal wall of the casing is formed by a superconductor. A coplanar waveguide filter 22 comprises a dielectric substrate 1, a plurality of resonators 5a, 5b, 5c and 5d and input/output terminal sections 4a and 4b, each of which is formed by a center conductor 2 and ground conductors 3a and 3b, both formed on the same surface of the dielectric substrate 1, with the ground conductors 3a to 3d being formed on the opposite sides of and in parallel relationship with the center conductor 2. The filter 22 is contained within a casing 21 having an internal wall, the surface of which is formed with a layer of superconductor 23.

Abstract: A combined signal of a digital pilot signal and a digital transmission signal is applied to a digital predistorter (20), wherein it is added with odd-order distortions based on a power series model to generate a predistorted signal, then the predistorted signal is converted by a DA converter (31) to an analog signal, then the analog signal is upconverted by a frequency upconverting part (33) to a send frequency band, and the upconverted signal is output after being amplified by a power amplifier (37). A pilot signal component is extracted from the power amplifier output, then odd-order distortion components of the power series model are extracted by a digital predistorter control part (50) from the pilot signal component, and the odd-order distortions in the digital predistorter (20) are controlled to decrease the levels of the distortion components.

Abstract: A matching circuit including a main matching block 51 inserted in a signal path and a series matching block 522, one end of which is connected to the main matching block 51, in which one end of a series connection of a switch 542 and a parallel matching block 532 is connected to the signal path at the other end of the series matching block 522 and impedance matching between input/output is performed at any one of two frequencies by setting the switch to ON/OFF.

Abstract: A power amplifier for receiving and amplifying an input signal and outputting an output signal includes N power amplifying units (N is an integer larger than 1) connected in parallel so as to output amplified signals in response to the input signal; an output combining unit for combining the output signals from the N power amplifying units and outputting a combined signal as the output signal of the power amplifier; and an amplitude controlling unit for selectively turning ON each of the N power amplifying units based on an amplitude of the input signal. In the power amplifier, the amplitude controlling unit may includes N amplitude adjusters connected in parallel for adjusting the amplitude of the input signal of the power amplifier; and a controller for selectively turning ON each of the N power amplifying units and controlling the amplitude adjusters so that an amplitude of the output signal becomes a substantially continuous function with respect to the amplitude of the input signal.

Abstract: In a quadrature hybrid circuit which has first and second two-port circuits 11 and 12 inserted between I/O ports P1 and P2 and between I/O ports P4 and P3, respectively, and third and fourth two-port circuits inserted between I/O ports P1 and P4 and between I/O ports P2 and P3, respectively, and which is configured so that under the condition that the I/O ports P1 to P4 are matched, a high-frequency signal fed via the I/O port P1 is divided between the I/O ports P2 and P3 and the divided two signals are output 90° out of phase with each other but no signal is provided to the I/O ports P4, there are provided SPST switches 7 and 8 responsive to external control to control electromagnetic connections or coupling across a plane of symmetry 5 of the quadrature hybrid circuit passing through intermediate points of symmetry 23 and 24 of the third and fourth two-port circuits 21 and 22.

Abstract: A radio communication system is comprised of: a transmitting system in which N transmission signals, frequency-converted to the same transmission frequency, are generated by N transmitters, N being an integer equal to or greater than 2, and the transmission signals are each applied to each one of N elements of an antenna for transmission; and a receiving system in which each transmitted signal is received by N-element antenna and the cross correlation coefficient between the transmitted signals received by the N-elements is minimized to thereby reconstruct each transmitted signal. The plural transmitted signals of the same frequency are received and the cross correlation coefficients of the received transmitted signals are minimized to thereby permit multiplexing of the transmission signal.

Abstract: A transmission signal and a pilot signal are predistorted by a digital predistorter 13 by use of a power-series model, and the predistorted output is converted by a digital-analog converter 14 to an analog signal. The analog signal is up converted by a frequency converter 15 to an RF-band signal, which is transmitted after being power-amplified by a Doherty amplifier 16. The pilot signal is extracted by a pilot signal extractor 17 from the output from the Doherty amplifier, and the extracted pilot signal is down converted by a frequency converter 18 to a baseband signal. The baseband pilot signal is converted by an analog-digital converter 19 to a digital pilot signal. A control part 21 detects an odd-order distortion component from the digital pilot signal, and based on the detected result, controls parameters of the digital predistorter.

Abstract: A plurality of one-quarter wavelength coplanar resonators 5a to 5d are formed in series on a dielectric substrate 1, and coplanar input/output terminal sections 4a and 4b are formed on the dielectric substrate at opposite ends of the series connection for coupling with resonators 5a and 5d, respectively. A center conductor line width w1 of each of the resonators 5a to 5d is equal to a center conductor line width wio of each of the input/output terminal section 4a and 4b, but a ground conductor spacing d1 of each of the resonators 5a to 5d is greater than a ground conductor spacing dio of each of input/output terminal section 4a and 4b. Maintaining the accuracy of design is facilitated and a reduction in the maximum current density in the resonator is enabled.

Abstract: A filter is provided which maintains a low insertion loss characteristic of a filter contained in a casing with a very simple construction that the internal wall of the casing is formed by a superconductor. A coplanar waveguide filter 22 comprises a dielectric substrate 1, a plurality of resonators 5a, 5b, 5c and 5d and input/output terminal sections 4a and 4b, each of which is formed by a center conductor 2 and ground conductors 3a and 3b, both formed on the same surface of the dielectric substrate 1, with the ground conductors 3a to 3d being formed on the opposite sides of and in parallel relationship with the center conductor 2. The filter 22 is contained within a casing 21 having an internal wall, the surface of which is formed with a layer of superconductor 23.

Abstract: In a quadrature hybrid circuit which has first and second two-port circuits 11 and 12 inserted between I/O ports P1 and P2 and between I/O ports P4 and P3, respectively, and third and fourth two-port circuits inserted between I/O ports P1 and P4 and between I/O ports P2 and P3, respectively, and which is configured so that under the condition that the I/O ports P1 to P4 are matched, a high-frequency signal fed via the I/O port P1 is divided between the I/O ports P2 and P3 and the divided two signals are output 90° out of phase with each other but no signal is provided to the I/O ports P4, there are provided SPST switches 7 and 8 responsive to external control to control electromagnetic connections or coupling across a plane of symmetry 5 of the quadrature hybrid circuit passing through intermediate points of symmetry 23 and 24 of the third and fourth two-port circuits 21 and 22.

Abstract: A power amplifier (1) for receiving and amplifying an input signal (10) and outputting an output signal (11) is disclosed. The power amplifier comprises: N power amplifying units (12) (N is an integer larger than 1) connected in parallel so as to output amplified signals in response to the input signal (10); an output combining unit (14) for combining the output signals from the N power amplifying units (12) and outputting a combined signal as the output signal (11) of the power amplifier; and an amplitude controlling unit (15) for selectively turning ON each of the N power amplifying units (12) based on an amplitude of the input signal (10).

Abstract: A transmission signal and a pilot signal are predistorted by a digital predistorter 13 by use of a power-series model, and the predistorted output is converted by a digital-analog converter 14 to an analog signal. The analog signal is up converted by a frequency converter 15 to an RF-band signal, which is transmitted after being power-amplified by a Doherty amplifier 16. The pilot signal is extracted by a pilot signal extractor 17 from the output from the Doherty amplifier, and the extracted pilot signal is down converted by a frequency converter 18 to a baseband signal. The baseband pilot signal is converted by an analog-digital converter 19 to a digital pilot signal. A control part 21 detects an odd-order distortion component from the digital pilot signal, and based on the detected result, controls parameters of the digital predistorter.

Abstract: A combined signal of a digital pilot signal and a digital transmission signal is applied to a digital predistorter (20), wherein it is added with odd-order distortions based on a power series model to generate a predistorted signal, then the predistorted signal is converted by a DA converter (31) to an analog signal, then the analog signal is upconverted by a frequency upconverting part (33) to a send frequency band, and the upconverted signal is output after being amplified by a power amplifier (37). A pilot signal component is extracted from the power amplifier output, then odd-order distortion components of the power series model are extracted by a digital predistorter control part (50) from the pilot signal component, and the odd-order distortions in the digital predistorter (20) are controlled to decrease the levels of the distortion components.

Abstract: A signal switching device is disclosed that is capable of transmitting signals with less signal loss while securing a good isolation characteristic. The signal switching device includes a first section formed from a superconducting material connected to a first transmission path. The first section has a smaller cross section at the input end than at the output end or, the signal switching device may include a first section formed from a superconducting material connected to a first transmission path in series, and a second section formed from a superconducting material connected to a second transmission path in parallel. The cross section of the second section is smaller than that of the second transmission path. The length of the second transmission path is determined in such a way that an input impedance of the second transmission path is sufficiently large when the second section is in a superconducting state.

Abstract: A transmitter comprises: an N-channel input side multi-port directional coupler which inputs thereto transmission signals of N channels and outputs signals of N channels, the input side multi-port directional coupler being implemented by digital signal processing. Digital signal processing type predistorters of N channels for linearizing respective transmission channels; digital-to-analog converters of N channels which input thereto the output signals from the digital signal processing type predistorters of N channels; and transmitting parts of N channels each including the output signal from the corresponding one of the digital-to-analog converters of N channels and an amplifier; and an N-channel output side multi-port power combiner which inputs thereto the output signals from the transmitting parts of N channels and outputs signals of N channels.