Delay adjustment to reduce distortion in an envelope tracking transmitter

摘要

A transceiverâ s receiver is tuned to a frequency which rejects the transmit frequency but allows reception of a signal caused by distortion in the transmitter. This signal leaks through the duplex filter 122. One of the delays 108,116, or the shaping table 112, or other setting, is adjusted to minimise the effect of the received distortion signal as assesssed by measuring RSSI, BER, EVM, the signal to noise plus interference ratio or another quality of service (QoS) parameter. The calibration signal may be transmitted during factory adjustment (figure 2). Alternatively the adjustment value may be perturbed by a code when the transmitter is in normal service, the sequence allowing the effect of the leakage signal to be discriminated from the effect of other received signals. The technique requires comparatively little extra circuitry.