LOAD CURRENT SENSOR FOR ENVELOPE TRACKING MODULATOR

摘要

An apparatus and method for sensing load current of an envelope tracking (ET) modulator enables load impedance of a power amplifier to be measured. Impairments associated with the load impedance characteristic can be suppressed by calibration and predistortion instead of by feedback (as done in the prior art). The ET modulator provides a switching regulator that can be reconfigured as a linear regulator for the purpose of sensing the load current. This allows the ET modulator to be operated open-loop, thereby eliminating the power consumption overhead resulting from utilization of a loop filter and error amplifier (used in the prior art) and achieving a higher overall efficiency.

主权项

1. A transmitter comprising:
an envelope generator configured to receive a data signal to be transmitted and generate an envelope signal based on the received data signal; an envelope tracking (ET) modulator coupled to the envelope generator and configured to receive the envelope signal, the envelope tracking modulator comprising a pulse width modulation (PWM) generator and a switching circuit having a first output and a sense output, wherein the PWM generator and the switching circuit are configured to:
operate as a linear regulator in a first mode and generate a first power amplifier supply signal at the first output as a function of a calibration signal, andoperate as a switching regulator in a second mode and generate a second power amplifier supply signal at the first output as a function of the received envelope signal; a current sensor circuit coupled to the second output of the ET modulator and configured to sense current of the first power amplifier supply signal at the first output; a filter coupled to the first output of the ET modulator for filtering the second output signal and generating a power amplifier switching supply source; and a power amplifier coupled to the filter, wherein when in the second mode, the power amplifier is configured to:
receive the power amplifier switching supply source as a supply voltage,receive and amplify a first transmitter signal generated from the data signal, andoutput an amplified transmitter signal.