Transmitter with delay mismatch compensation
A transmitter device comprises a digital part and an analog part. The digital part comprises a digital modulator for receiving bits and for digitally modulating the received bits. The transmitter device includes first and second digital-to-analog converters. The transmitter device furthermore comprises at least one filter unit arranged in the digital part and coupled between at least one of the first and second digital-to-analog converters and the digital modulator. A table unit is coupled to the at least one filter unit and is used to store pre-defined compensation filter values for the at least one filter unit to compensate different delay mismatches in the analog part of the transmitter device. The filter values of the at least one filter unit are set to those compensation filter values as stored in the table unit (TU) which correspond to a determined delay mismatch.
1. A transmitter device, comprising:
a digital part and an analog part;
a digital modulator arranged in the digital part and configured to receive bits and digitally modulate the received bits;
a first digital-to-analog converter and a second digital-to-analog converter;
a digital filter unit arranged in the digital part and coupled between the digital modulator and one of the first and second digital-to-analog converters; and
a table unit coupled to the digital filter unit and configured to store pre-defined compensation filter values for the digital filter unit, the compensation filter values being configured to compensate different analog delay mismatches;
wherein the digital filter unit is configured to receive from the table unit selected compensation filter values of the compensation filter values stored in the table unit, the selected compensation filter values corresponding to a determined delay mismatch of the analog part.
2. A transmitter device according to claim 1 , wherein:
said digital modulator is configured to receive a digital signal and to output a digital in-phase signal and a digital quadrature signal;
said first digital-to-analog converter is configured to convert said digital in-phase signal to an analog in-phase signal, and
said second digital-to-analog converter is adapted to convert said digital quadrature signal to an analog quadrature signal.
3. A transmitter device according to claim 2 , wherein:
the digital filter unit comprises a first order all-pass filter with a pole and zero constellation, which is tunable according to the compensation filter values stored in the table unit.
4. A transmitter device according to claim 3 , further comprising:
a delay selector unit coupled to the table unit and configured to provide the delay mismatch of the analog part of the transmitter device.
5. A transmitter device according to claim 1 , wherein:
the digital modulator is configured to receive a digital signal and output a digital amplitude signal and a digital phase signal;
said first digital-to-analog converter is configured to convert said digital amplitude signal to an analog amplitude signal; and
said second digital-to-analog converter is configured to convert said digital phase signal to an analog phase signal,
wherein the digital filter unit is coupled between the digital phase output and the second digital-to-analog converter.
6. Transmitter device according to claim 5 , wherein:
the digital filter unit comprises a first order all-pass filter with a pole and zero constellation, which is tunable according to the compensation filter values stored in the table unit.
7. Transmitter device according to claim 6 , further comprising:
a delay selector unit coupled to the table unit for providing the delay mismatch of the analog part of the transmitter device.
8. A method for controlling a transmitter device, wherein the transmitter device comprises a digital and an analog part, a digital modulator, first and second digital-to-analog converters and a filter unit coupled between the digital modulator and one of the first and second digital-to-analog converters, the method comprising:
digitally modulating received bits;
storing in a table unit pre-defined compensation filter values configured to compensate for different analog delay mismatches; and
providing to the filter unit selected compensation filter values of the stored compensation filter values, the selected compensation filter values corresponding to a determined delay mismatch of the analog part.
9. A method according to claim 8 , wherein the delay mismatch in the analog part of the transmitter device is determined by:
feeding a first digital test signal to the digital modulator of the transmitter device,
converting, to a digital in-phase test signal, an analog in-phase test signal output from said transmitter device based on said first digital test signal,
feeding a second digital test signal to said modulator, wherein said further predetermined digital test signal comprises a same bit stream as said first digital test signal,
converting, to a digital quadrature test signal, an analog quadrature test signal output from said transmitter device based on said second digital test signal,
measuring a time shift between said digital in-phase test signal and said digital quadrature signal, and
determining a delay value for correcting a time shift between an analog part of a path of said transmitter device for an in-phase signal and a path of said transmitter device for a quadrature signal based on said time shift measured.
10. A transmitter device, comprising:
a digital part and an analog part;
a digital modulator arranged in the digital part and configured to receive bits and digitally modulate the received bits;
a first digital-to-analog converter and a second digital-to-analog converter;
a digital filter unit arranged in the digital part and coupled between the digital modulator and one of the first and second digital-to-analog converters;
a table unit coupled to the digital filter unit and configured to store pre-defined compensation filter values for the digital filter unit, the compensation filter values being configured to compensate different analog delay mismatches; and
means for determining a delay mismatch of the analog part and providing the determined delay mismatch to the table unit, wherein the digital filter unit is configured to receive from the table unit selected compensation filter values of the compensation filter values stored in the table unit, the selected compensation filter values corresponding to the determined delay mismatch of the analog part.
11. A transmitter device according to claim 10 , wherein:
said digital modulator is configured to receive a digital signal and to output a digital in-phase signal and a digital quadrature signal;
said first digital-to-analog converter is configured to convert said digital in-phase signal to an analog in-phase signal, and
said second digital-to-analog converter is adapted to convert said digital quadrature signal to an analog quadrature signal.
12. A transmitter device according to claim 10 , wherein:
the digital filter unit comprises a first order all-pass filter with a pole and zero constellation, which is tunable according to the compensation filter values stored in the table unit.
13. A transmitter device according to claim 12 , further comprising:
a delay selector unit coupled to the table unit and configured to provide the delay mismatch of the analog part of the transmitter device.
14. A transmitter device according to claim 10 , wherein:
the digital modulator is configured to receive a digital signal and output a digital amplitude signal and a digital phase signal;
said first digital-to-analog converter is configured to convert said digital amplitude signal to an analog amplitude signal; and
said second digital-to-analog converter is configured to convert said digital phase signal to an analog phase signal, wherein the digital filter unit is coupled between the digital phase output and the second digital-to-analog converter.
15. Transmitter device according to claim 14 , wherein:
the digital filter unit comprises a first order all-pass filter with a pole and zero constellation, which is tunable according to the compensation filter values stored in the table unit.