| 摘要 |
PROBLEM TO BE SOLVED: To provide an envelope tracking type transmitter that can prevent power supply efficiency from decreasing even when a modulation rate becomes fast.SOLUTION: A multi(N)-phase switching power supply is used as an envelope tracking power supply, and an envelope waveform is approximated by an N-stage step-like waveform. A pulse width of the switching power supply having a cycle T is set to be integer number times of T/N to cancel a high harmonic wave generated at the N switching power supply units. Consequently, a switching rate that was conventionally required to be proportional to a modulation rate for the purpose of reducing a power density of switching noise to a predetermined value or less can be independent of the modulation rate, and therefore, an envelope tracking transmitter that can prevent power supply efficiency from decreasing even when a modulation signal with a higher speed is inputted can be achieved. |
