A waveguide unit (2) is closed at one end thereof by a short circuit plane (2a) provided with through holes (3-1 to 3-6). Radio wave absorbers (4-1 to 4-6) absorb a frequency signal being a non-reflective target in the state of being inserted through the through holes (3-1 to 3-6) toward the inside of the waveguide unit (2) and contacting inner surfaces (3′-1 to 3′-6) of the through holes (3-1 to 3-6).

A waveguide unit (2) is closed at one end thereof by a short circuit plane (2a) provided with through holes (3-1 to 3-6). Radio wave absorbers (4-1 to 4-6) absorb a frequency signal being a non-reflective target in the state of being inserted through the through holes (3-1 to 3-6) toward the inside of the waveguide unit (2) and contacting inner surfaces (3′-1 to 3′-6) of the through holes (3-1 to 3-6).

A waveguide unit (2) is closed at one end thereof by a short circuit plane (2a) provided with through holes (3-1 to 3-6). Radio wave absorbers (4-1 to 4-6) absorb a frequency signal being a non-reflective target in the state of being inserted through the through holes (3-1 to 3-6) toward the inside of the waveguide unit (2) and contacting inner surfaces (3-1 to 3-6) of the through holes (3-1 to 3-6).

A waveguide unit (2) is closed at one end thereof by a short circuit plane (2a) provided with through holes (3-1 to 3-6). Radio wave absorbers (4-1 to 4-6) absorb a frequency signal being a non-reflective target in the state of being inserted through the through holes (3-1 to 3-6) toward the inside of the waveguide unit (2) and contacting inner surfaces (3-1 to 3-6) of the through holes (3-1 to 3-6).

According to one embodiment, a high-frequency semiconductor amplifier includes an input terminal, an input matching circuit, a high-frequency semiconductor amplifying element, an output matching circuit and an output terminal. The input terminal is inputted with a fundamental signal. The fundamental signal has a first frequency band and a first center frequency in the first frequency band. The input matching circuit includes an input end and an output end. The input end of the input matching circuit is connected to the input terminal. The high-frequency semiconductor amplifying element includes an input end and an output end. The input end of the high-frequency semiconductor amplifying element is connected to the output end of the input matching circuit. The high-frequency semiconductor amplifying element is configured to amplify the fundamental signal.

According to one embodiment, a high-frequency semiconductor amplifier includes an input terminal, an input matching circuit, a high-frequency semiconductor amplifying element, an output matching circuit and an output terminal. The input terminal is inputted with a fundamental signal. The fundamental signal has a first frequency band and a first center frequency in the first frequency band. The input matching circuit includes an input end and an output end. The input end of the input matching circuit is connected to the input terminal. The high-frequency semiconductor amplifying element includes an input end and an output end. The input end of the high-frequency semiconductor amplifying element is connected to the output end of the input matching circuit. The high-frequency semiconductor amplifying element is configured to amplify the fundamental signal.

According to one embodiment, a high-frequency semiconductor amplifier includes an input terminal, an input matching circuit, a high-frequency semiconductor amplifying element, an output matching circuit and an output terminal. The input terminal is inputted with a fundamental signal. The fundamental signal has a first frequency band and a first center frequency in the first frequency band. The input matching circuit includes an input end and an output end. The input end of the input matching circuit is connected to the input terminal. The high-frequency semiconductor amplifying element includes an input end and an output end. The input end of the high-frequency semiconductor amplifying element is connected to the output end of the input matching circuit. The high-frequency semiconductor amplifying element is configured to amplify the fundamental signal.

A radio frequency load for absorbing a radio frequency wave having a frequency in a predetermined frequency band and a wavelength comprises a waveguide with a portion having an opening for said radio frequency wave. In addition, the radio frequency load comprises at least one metal rod provided in said waveguide, said at least one metal rod having a length of one-half of said wavelength to damp said radio frequency wave.

A radio frequency load for absorbing a radio frequency wave having a frequency in a predetermined frequency band and a wavelength comprises a waveguide with a portion having an opening for said radio frequency wave. In addition, the radio frequency load comprises at least one metal rod provided in said waveguide, said at least one metal rod having a length of one-half of said wavelength to damp said radio frequency wave.