PULSE SHAPING WHICH COMPENSATES FOR COMPONENT DISTORTION

• US 20070280375A1
• Filed: 08/16/2007
• Published: 12/06/2007
• Est. Priority Date: 01/21/1998
• Status: Abandoned Application

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Lobo, Natividadel
• Application Number:
  US11/839,771
• Publication Number:
  US 20070280375A1
• Time in Patent Office: Days
• US Class Current: 375/285
• CPC Class Codes: H03F 1/32 Modifications of amplifiers to reduce non-linear distortion by negative feedback H03F1/34
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04L 25/0384 Design of pulse shapes pulse shape for impulse radio H04B1/7172
• CPC Class Codes: H04L 27/10 Frequency-modulated carrier systems, i.e. using frequency-shift keying H04L27/32 takes precedence
• CPC Class Codes: H04L 27/18 Phase-modulated carrier systems, i.e. using phase-shift keying H04L27/32 takes precedence
• CPC Class Codes: H04L 27/20 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 27/2017 in which the phase changes are non-linear, e.g. generalized and Gaussian minimum shift keying, tamed frequency modulation H04L27/201 takes precedence
• CPC Class Codes: H04L 27/366 Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator
• CPC Class Codes: H04L 27/368 adaptive predistortion

Abstract

A method is provided for defining a pulse function shape for acting on a data stream for transmission in a telecommunication system which compensates for distortion by a component of the transmitter. The method comprises defining desired cost parameters (e.g. error functions for amplitude, BER, bandwidth, energy, AFC) and defining the shape of the pulse function in dependence of the desired cost parameters and the distortion to be compensated for. A pulse generator, modulator and communications device providing such a pulse function are also provided. Application in dual mode TDMA/CDMA system.

Claims

1. A method for defining the relationship between frequency and amplitude of a pulse function for acting on a data stream for transmission in a telecommunications system to compensate for distortion by a component of the transmitter, the method comprising:

defining desired cost parameters on the basis of the telecommunications system requirements and the distortion to be compensated for; and

defining the amplitude of the pulse function over a range of frequencies in dependence on the desired cost parameters.

2. A method as claimed in claim 1, wherein the compensation is for non linear distortion.

3. A method as claimed in claim 2, wherein defining the distortion to be compensated for comprises defining first and second distortions.

4. A method as claimed in claim 3, wherein the first and second distortions relate to different component tolerances.

5. A method as claimed in claim 3, wherein the method comprises weighting the first and second distortions.

6. A method as claimed in claim 1, wherein the compensation is for distortion by a linear component of the transmitter.

7. A method as claimed in claim 6, wherein the compensation is for distortion by a reconstruction filter.

8. A method as claimed in claim 2, wherein the compensation is for distortion by a non linear component of the transmitter.

9. A method as claimed in claim 8, wherein the compensation is for distortion by a power amplifier.

10. A method for defining the relationship between frequency and amplitude of a pulse function for acting on a data stream for transmission in a telecommunications system to compensate for distortion by first and second components of the transmitter, the method comprising:

the method of claim 1 for defining the amplitude of the pulse function over a range of frequencies in dependence on the desired cost parameters for the first component;

defining the cost parameters for the second component on the basis of the distortion to be compensated for in the second component; and

defining the amplitude of the pulse function over a range of frequencies in dependence upon the cost parameters of the second component and the pulse function defined for the first component.

11. A method as claimed in claim 10, wherein the compensation for distortion by the first component is compensation for distortion by a linear component of the transmitter, and wherein the compensation for distortion by the second component is compensation for non linear distortion.

12. A method as claimed in claim 11, wherein the compensation is for distortion by a non linear component of the transmitter.

13. A method according to claim 10, wherein the desired cost parameters are selected from one or more of the group including component tolerances, power efficiency, spectral efficiency, bit error rate, AFC, Nyquist, and energy.

14. A method as claimed in claim 10, wherein desired cost parameters are defined on the basis of TDMA telecommunications system requirements.

15. A method as claimed in claim 10, wherein desired cost parameters are defined on the basis of GSM requirements.

16. A method as claimed in claim 14, wherein the pulse function is defined such that a pulse of Gaussian shape may be transmitted.

17. A method as claimed in claim 1, wherein desired cost parameters are defined on the basis of CDMA requirements.

18. A method as claimed in claim 17, wherein the pulse function is defined such that a pulse of root raised cosine shape may be transmitted.

19. A method according to claim 10, wherein the amplitude of the pulse function over a range of frequencies is defined in an iterative process in which the pulse function is altered and the cost parameters determined until an acceptable balance of cost parameters is achieved.

20. A method according to claim 10, wherein the method comprises the step of weighting the respective cost parameters.

21. A method according to claim 20, wherein an acceptable balance between the cost parameters is achieved by optimizing the respective costs with the respective weightings.

22. A method according to claim 21, wherein the optimization is performed using an optimizer computer programme.

23. A pulse function generator for converting a data stream in accordance with a pulse function shaped in accordance with the relationship defined by the method of claim 10.

24. A modulator for providing a signal for transmission in a telecommunication system comprising:

means for shaping a data stream in accordance with the pulse function generator of claim 23.

25. A modulator according to claim 24, wherein the means for shaping comprises a look-up table.

26. A transceiver for a communication device comprising a modulator in accordance with claim 24 and a demodulator.

27. A communication device operable in communication system comprising a transceiver according to claim 26.

29. A dual mode communication device operable in a first mode when a first set of cost parameters are desired and in a second mode when a second set of cost parameters are desired, the radiotelephone comprising:

a first pulse function generator for converting a data stream in accordance with a pulse function shaped in dependence on the first set of desired cost parameters;

a second pulse function generator for converting data stream in accordance with a pulse function shaped in dependence on the second set of desired cost parameters; and

means for selecting the pulse function generator in accordance with the mode of operation of the phone;

wherein at least one of the pulse functions is shaped in accordance with the relationship defined by the method of claim 1.

30. A communication device as claimed in claim 29, which is operable at a first data rate in the first mode and a second data rate in the second mode.

31. A communication device as claimed in claim 29, wherein the first data rate supports voice applications and the second data rate supports data applications.

33. A method for selecting a modulation scheme for a communication system using a predetermined transmitter, the method comprising:

defining a pulse function for a first modulation scheme in accordance with the method as claimed in claim 1;

defining a pulse function for a second modulation scheme for the same desired cost parameters;

determining the resultant cost parameters for each scheme; and

selecting the modulation scheme which gives good resultant cost parameters given the desired ones.

28. A dual mode communication device operable in a first mode in a TDMA telecommunications system in which a channel is a combination of frequency and timeslot and a second mode in a CDMA telecommunications system, comprising a modulator for modulating a data stream with a carrier signal in accordance with a predetermined modulation scheme in both the first and second modes of operation and a pulse function generator for shaping a data stream in accordance with respective pulse functions responsive to the mode of operation of the radio telephone and distortion by a component of the transmitter.

32. A dual mode communication device operable in a first mode when a first set of cost parameters are desired and in a second mode when a second set of cost parameters are desired, the radiotelephone comprising:

a modulator for modulating a data stream with a carrier signal in accordance with a predetermined modulation scheme in both the first and second modes of operation;

a first pulse function generator for shaping a data stream in accordance with a pulse function shaped in dependence on the first set of desired cost parameters and distortion by a component of the transmitter;

a second pulse function generator for shaping a data stream in accordance with a pulse function shaped in dependence on the second set of desired cost parameters and distortion by a component of the transmitter; and

means for selecting the pulse function generator in accordance with the mode of operation of the phone.