Distortion compensation circuit

Patent metadata

Field	Value
Publication number	US-9929700-B2
Application number	US-201515306382-A
Country	US
Kind code	B2
Filing date	Apr 24, 2015
Priority date	Apr 25, 2014
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

A distortion compensation circuit includes a low-pass circuit to block the passage of two-wave RF signals and intermodulation distortions and to allow the passage of a difference-frequency signal. The low-pass circuit is connected between a signal path and an intermodulation distortion adjustment circuit.

First claim

The invention claimed is:

1. A distortion compensation circuit that compensates for intermodulation distortions occurring in the amplifier by generating intermodulation distortions which have opposite characteristics to the intermodulation distortions occurring in the amplifier, the amplifier being connected to a stage previous to an input terminal of a signal path or to a stage subsequent to an output terminal of the signal path, the distortion compensation circuit comprising:
a linearizer circuit to generate, in response to an input of a plurality of radio frequency signals through the input terminal, a difference-frequency signal and intermodulation distortions of the radio frequency signals, the linearizer circuit being inserted in the signal path;
a low-pass circuit to block passage of the radio frequency signals and the intermodulation distortions generated by the linearizer circuit and to allow passage of the difference-frequency signal, one end of the low-pass circuit being connected to the signal path; and
an intermodulation distortion adjustment circuit to adjust intermodulation distortions appearing in the signal path by reflecting the difference-frequency signal having passed through the low-pass circuit to return to the linearizer circuit, the intermodulation distortion adjustment circuit being connected between another end of the low-pass circuit and a ground,
wherein
the linearizer circuit includes a diode and a resistor, the diode being connected between the signal path and a ground, the resistor being connected between a DC terminal and the signal path,
the low-pass circuit includes a transmission line whose one end is connected to the signal path and another end is connected to the intermodulation distortion adjustment circuit, and an open stub whose one end is connected to the transmission line, each of the transmission line and the open stub having a length of a quarter wavelength at a center frequency of the radio frequency signals, and
the intermodulation distortion adjustment circuit includes a reactance element.

2. The distortion compensation circuit according to claim 1 , wherein the intermodulation distortion adjustment circuit adjusts an impedance of the difference-frequency signal such that the intermodulation distortions appearing in the signal path have opposite characteristics to the intermodulation distortions occurring in the amplifier.

3. The distortion compensation circuit according to claim 1 , further comprising a harmonic impedance adjustment circuit to adjust the intermodulation distortions appearing in the signal path by reflecting harmonic components of the radio frequency signals generated by the linearizer circuit to return to the linearizer circuit, one end of the harmonic impedance adjustment circuit being connected to the signal path,
wherein the harmonic impedance adjustment circuit adjusts impedances of the harmonic components such that the intermodulation distortions appearing in the signal path have opposite characteristics to the intermodulation distortions occurring in the amplifier.

4. A distortion compensation circuit that compensates for intermodulation distortions occurring in the amplifier by generating intermodulation distortions which have opposite characteristics to the intermodulation distortions occurring in the amplifier, the amplifier being connected to a stage previous to an input terminal of differential signal paths or to a stage subsequent to an output terminal of the differential signal paths, the differential signal paths including a first signal path and a second signal path, the distortion compensation circuit comprising:
a differential signal converter to convert radio frequency signals, which are input through the input terminal and have different frequencies, into a pair of differential signals, and outputs first radio frequency signals to the first signal path as one part of the differential signals and outputs second radio frequency signals to the second signal path as another part of the differential signals;
a linearizer circuit to generate, on the first signal path, a difference-frequency signal and intermodulation distortions of the first radio frequency signals in response to an input of the first radio frequency signals, and to generate, on the second signal path, a difference-frequency signal and intermodulation distortions of the second radio frequency signals in response to an input of the second radio frequency signals, the linearizer circuit being inserted in the differential signal paths;
a first low-pass circuit to block passage of the first radio frequency signals and the intermodulation distortions generated on the first signal path and to allow passage of the difference-frequency signal generated on the first signal path, one end of the first low-pass circuit being connected to the first signal path;
a second low-pass circuit to block passage of the second radio frequency signals and the intermodulation distortions generated on the second signal path and to allow passage of the difference-frequency signal generated on the second signal path, one end of the second low-pass circuit being connected to the second signal path;
a first intermodulation distortion adjustment circuit to adjust intermodulation distortions appearing in the first signal path by reflecting the difference-frequency signal having passed through the first low-pass circuit to return to the linearizer circuit, the first intermodulation distortion adjustment circuit being connected between another end of the first low-pass circuit and a ground;
a second intermodulation distortion adjustment circuit to adjust intermodulation distortions appearing in the second signal path by reflecting the difference-frequency signal having passed through the second low-pass circuit to return to the linearizer circuit, the second intermodulation distortion adjustment circuit being connected between another end of the second low-pass circuit and a ground; and
a single-phase signal converter to convert the differential signals having been transmitted on the first and second signal paths into single-phase signals,
wherein
the linearizer circuit includes a diode, a first resistor and a second resistor, the diode being connected between the first and second signal paths, the first resistor being connected between the first signal path and a DC terminal, the second resistor being connected between the second signal path and the ground,
the first low-pass circuit includes a first transmission line whose one end is connected to the first signal path and another end is connected to the first intermodulation distortion adjustment circuit, and a first open stub whose one end is connected to said another end of the first transmission line, each of the first transmission line and the first open stub having a length of a quarter wavelength at a center frequency of the first radio frequency signals,
the first intermodulation distortion adjustment circuit includes a first reactance element,
the second low-pass circuit includes a second transmission line whose one end is connected to the second signal path and another end is connected to the second intermodulation distortion adjustment circuit, and a second open stub whose one end is connected to said another end of the second transmission line, each of the second transmission line and the second open stub having a length of a quarter wavelength at a center frequency of the second radio frequency signals, and
the second intermodulation distortion adjustment circuit includes a second reactance element.

5. The distortion compensation circuit according to claim 4 , wherein
the first intermodulation distortion adjustment circuit adjusts an impedance of the difference-frequency signal generated on the first signal path such that the intermod

Assignees

• Mitsubishi Electric Corp

Inventors

• Otsuka Hiroshi
• Komatsuzaki Yuji
• Nishihara Jun
• Noto Hifumi
• Yamanaka Koji

Classifications

• H03F1/02

  Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation · CPC title

• H03F3/189

  High-frequency amplifiers, e.g. radio frequency amplifiers · CPC title

• H03F1/3241

  using predistortion circuits (H03F1/3211, H03F1/3217 take precedence) · CPC title

• H03F1/565

  using inductive elements · CPC title

• H03F2200/451

  the amplifier being a radio frequency amplifier · CPC title