Group delay compensation

An apparatus comprising:

• a timing shift module and a filter module for generating a filtered transmit signal from an unfiltered transmit signal using a filtering function for compensating for in-band group delay ripple of a transmit forward path of a transmitter of a mobile communication system and residual absolute delay of the transmit forward path;
• a group delay compensation module for providing the filtered transmit signal for transmission using the transmit forward path of the transmitter;
• a wideband transmit feedback path of a mobile communication system for receiving a receive signal using a wideband transmit feedback path of the transmitter of the mobile communication system;
• a calculation module for generating an estimate of a transfer function of the transmit forward path;
• and
• a coefficients update module for calculating an update of a filter function for compensating for in-band group delay ripple of the transmit forward path and residual absolute delay of the transmit forward path, wherein said filtering function includes a previous iteration of the filter function for compensating for said estimated transfer function of the transmit forward path.

A method comprising:

• generating a filtered transmit signal from an unfiltered transmit signal using a filtering function for compensating for in-band group delay ripple of a transmit forward path of a transmitter of a mobile communication system and residual absolute delay of the transmit forward path;
• providing the filtered transmit signal for transmission using the transmit forward path of the transmitter;
• receiving a receive signal using a wideband transmit feedback path of the transmitter of the mobile communication system;
• generating an estimate of a transfer function of the transmit forward path;
• and
• calculating an update of a filter function for compensating for in-band group delay ripple of the transmit forward path and residual absolute delay of the transmit forward path, wherein said filtering function includes a previous iteration of the filter function for compensating for said estimated transfer function of the transmit forward path.

A computer program, embodied on a non-transitory computer readable medium, the computer program when executed by a processor, causes the processor to perform at least the following:

• generating a filtered transmit signal from an unfiltered transmit signal using a filtering function for compensating for in-band group delay ripple of a transmit forward path of a transmitter of a mobile communication system and residual absolute delay of the transmit forward path;
• providing the filtered transmit signal for transmission using the transmit forward path of the transmitter;
• receiving a receive signal using a wideband transmit feedback path of the transmitter of the mobile communication system;
• generating an estimate of a transfer function of the transmit forward path;
• and
• calculating an update of a filter function for compensating for in-band group delay ripple of the transmit forward path and residual absolute delay of the transmit forward path, wherein said filtering function includes a previous iteration of the filter function for compensating for said estimated transfer function of the transmit forward path.