Patent ID: 8873611

Claim:
A transmitter comprising: a Δ-Σ modulation means which performs Δ-Σ modulation of a predetermined input signal; and a control means which changes a parameter of said Δ-Σ modulation means in accordance with a predetermined condition, wherein said Δ-Σ modulation means performs Δ-Σ modulation of an envelope signal generated at a baseband extracted from an orthogonal radio signal, said Δ-Σ modulation means includes an adding means and a quantization means, said quantization means outputs three or more output values which correspond to the results of comparison between two or more threshold values and an input of said quantization means, a signal inputted to said Δ-Σ modulation means is inputted to said adding means, a signal outputted from said quantization means, after a predetermined signal processing, which includes a signal processing provided by said adding means, is fed back to said quantization means, said signal outputted from said quantization means is outputted from said Δ-Σ modulation means, said parameter is at least one of a threshold value of a quantization means constituting said Δ-Σ modulation means and an output value of said quantization means, said predetermined condition is at least one of a transmission signal type of said input signal, a back-off request value to an amplification means constituting said transmitter, a modulation method of said input signal, a magnitude of transmission power measured by said transmitter, a time slot of transmission, amplitude distribution of said input signal, and a result of identifying whether a null signal or not, said control means changes said parameter for improving radio characteristics based on ACPR (Adjusted Channel Leakage Power Radio) measured by said transmitter, and SIR (Signal to interference Ratio) measured at a receiving side, and efficiency of said amplification means, and said control means selects one output value other than a maximum output value and a minimum output value from among said three or more output values and sets said one output value to the closest possible value to a time average value of said envelope signal.