RADIO DEVICE AND DISTORTION CANCELLING METHOD

• US 20170077981A1
• Filed: 08/17/2016
• Published: 03/16/2017
• Est. Priority Date: 09/15/2015
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Tobisu, Yusuke, Sato, Tadahiro, KANNARI, HIDEYUKI
• Granted Patent: US 9,621,220 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion

Abstract

A radio device includes: a processor that outputs a transmission signal containing a plurality of signals that are transmitted at different frequencies; an amplifier that amplifies the transmission signal output from the processor; and a transmitter/receiver that transmits by radio the transmission signal amplified by the amplifier and that receives by radio a signal having a frequency different from a frequency of the transmission signal. The processor generates a cancel signal based on the plurality of signals contained in the transmission signal, the cancel signal corresponding to an intermodulation distortion that occurs due to intermodulation among the plurality of signals, and the transmitter/receiver synthesizes the cancel signal generated by the processor with the transmission signal amplified by the amplifier.

Claims

1. A radio device comprising:

a processor that outputs a transmission signal containing a plurality of signals that are transmitted at different frequencies;

an amplifier that amplifies the transmission signal output from the processor; and

a transmitter/receiver that transmits by radio the transmission signal amplified by the amplifier and that receives by radio a signal having a frequency different from a frequency of the transmission signal, wherein

the processor generates a cancel signal based on the plurality of signals contained in the transmission signal, the cancel signal corresponding to an intermodulation distortion that occurs due to intermodulation among the plurality of signals, and

the transmitter/receiver synthesizes the cancel signal generated by the processor with the transmission signal amplified by the amplifier.

2. The radio device according to claim 1, wherein

the processor calculates a frequency of the intermodulation distortion that occurs due to the intermodulation among the plurality of signals contained in the transmission signal according to frequency information containing information on a transmission frequency band and a reception frequency band in the transmitter/receiver, and

when the calculated frequency of the intermodulation distortion and the reception frequency band overlap each other, the processor generates the cancel signal.

3. The radio device according to claim 1, wherein

the processor calculates a waveform of the intermodulation distortion that occurs due to the intermodulation among the plurality of signals contained in the transmission signal, and

the processor generates a cancel signal having a waveform that is an inversion of the calculated waveform of the intermodulation distortion.

4. The radio device according to claim 3, wherein the processor adjusts an amount of delay, a phase, and a weighting coefficient of the generated cancel signal.

5. The radio device according to claim 4, wherein the processor adjusts the amount of delay, the phase, and the weighting value of the cancel signal such that correlation between the calculated waveform of the intermodulation distortion and a reception signal that is received by radio by the transmitter/receiver and is input to the processor is minimized.

6. The radio device according to claim 1, further comprising:

a first digital analogue (DA) converter that performs DA conversion on the transmission output from the processor and outputs the transmission signal to the transmitter/receiver; and

a second DA converter that performs DA conversion on the cancel signal generated by the processor and outputs the cancel signal to the transmitter/receiver.

7. The radio device according to claim 1, further comprising a filter that removes components of a transmission frequency band from an input signal, wherein

the processor outputs the transmission signal with which the generated cancel signal are synthesized, and

the filter extracts components of the cancel signal by removing the components of the transmission frequency band from the transmission signal output from the processor and outputs the components of the cancel signal to the transmitter/receiver.

8. The radio device according to claim 7, wherein

the processor changes a clipping threshold that is predetermined according to input/output characteristics of the amplifier to a value smaller than the clipping threshold by a power of the generated cancel signal, implements clipping on the transmission signal, using the changed clipping threshold, and

the processor synthesizes the cancel signal with the transmission signal on which the clipping has been implemented.

9. A distortion cancelling method performed by a radio device including a transmitter/receiver that transmits by radio a transmission signal containing a plurality of signals that are transmitted at different frequencies and that receives by radio a signal having a frequency different from a frequency of the transmission signal, the distortion cancelling method comprising:

generating, by a processor, a cancel signal based on the plurality of signals contained in the transmission signal, the cancel signal corresponding to an intermodulation distortion that occurs due to intermodulation among the plurality of signals;

amplifying the transmission signal; and

synthesizing, by the transmitter/receiver, the cancel signal with the transmission signal having been amplified.