Transmitter and communication device
AssigneePanasonic Corporation
InventorToru Matsuura
Life of this patent
Estimating the term…
Abstract
A transmitter compensates for AM/PM distortion and operates with low distortion and high efficiency. A compensation section calculates an amplitude signal M representing the magnitude of a vector consisting of IPL and QPL signals which pass through LPFs, respectively, thereby predicting variation of the envelope of a radio frequency signal Pi, which variation occurs due to Ip′ and Qp′ signals passing through LPFs, respectively. The compensation section calculates a phase compensation amount θcomp, based on the calculated amplitude signal M, and adds the phase compensation amount θcomp to a phase signal θ.
Claims11
A transmitter which outputs a transmission signal, the transmitter comprising:
- a signal generation section for performing predetermined signal conversion processing on an input signal, and generating first I and Q signals, a phase signal representing a phase component of the input signal, and a first amplitude signal representing a magnitude of the input signal;
- an IQ mapping section for converting the phase signal into second I and Q signals;
- a first low-pass filter (LPF) for removing a spurious component from the second I and Q signals;
- a quadrature modulator for performing quadrature modulation on the second I and Q signals inputted via the first LPF, and outputting a radio frequency signal;
- an amplitude modulator for performing amplitude modulation on the radio frequency signal with the first amplitude signal, and outputting the transmission signal;
- and
- a compensation section for compensating for amplitude modulation/phase modulation (AM/PM) distortion contained in the transmission signal, based on the first I and Q signals,
- wherein the compensation section includes:
- a second low-pass filter (LPF) having the same characteristics as those of the first LPF for receiving the first I and Q signals, predicting a variation of an output caused by the first LPF, and removing a spurious component from the first I and Q signals;
- an amplitude calculation section for calculating a second amplitude signal representing a magnitude of the first I and Q signals inputted via the second LPF;
- a look-up table (LUT) in which a coefficient corresponding to the magnitude of the second amplitude signal is stored in advance;
- a control section for reading, from the LUT, the coefficient corresponding to the magnitude of the second amplitude signal, and calculating, based on the read coefficient, a phase compensation amount corresponding to the second amplitude signal;
- and
- an adder for adding the phase compensation amount to the phase signal.
Dependencies are inferred from the claim text.