Compensation for the carrier frequency offset in a receiving apparatus, which is designed for a plurality of modulation types, in a mobile communications system

• US 7,545,885 B2
• Filed: 10/31/2005
• Issued: 06/09/2009
• Est. Priority Date: 11/02/2004
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Infineon Technologies AG
• Inventors: Hammes, Markus, Puma, Giuseppe Li
• Primary Examiner(s): Ahn; Sam K
• Application Number:
  US11/263,423
• Publication Number:
  US 20060115021A1
• Time in Patent Office: 1,317 Days
• Field of Search: 375/269, 375/272, 375/303, 375/316, 375/329, 375/330, 375/331, 375/332, 375/333, 375/334, 375/335, 375/336, 375/337, 329/300, 332/100
• US Class Current: 375/316
• CPC Class Codes: H04L 2027/0065 Frequency error detectors H04L2027/0067 takes precedence
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 2027/0095 in a preamble or similar structure
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/2332 using a non-coherent carrier

Abstract

The present invention relates to a receiving apparatus for a mobile communications system which can be modulated using different modulation types at the transmitter end. According to one embodiment of the invention, in the middle of a data burst of a Bluetooth communications system, a GFSK modulation method is switched to an M-DPSK modulation method, which is used for the payload data. A frequency offset estimation unit is provided for GFSK-modulated signals in a first receiving section and estimates the frequency offset by averaging over a bit sequence of a trailer of a data burst. The frequency offset is corrected in a second receiving section, by means of a frequency correction unit which operates on the basis of the CORDIC algorithm.

Claims

1. A receiving apparatus for a mobile communications system, comprising:

a first receiving section configured to demodulate received signals of a first modulation type, the first receiving section comprising a frequency offset estimation unit; and

a second receiving section configured to demodulate received signals of a second modulation type, the second receiving section comprising a frequency correction unit configured to correct the frequency offset;

wherein the first receiving section is connected to the second receiving section configured to transmit the estimated frequency offset from the first receiving section to the second receiving; and

wherein the first modulation type comprises a two-value frequency modulation method, and the second modulation type comprises a modulation method having an M-value of M≧

4.

2. The receiving apparatus of claim 1, wherein the apparatus is used in a Bluetooth communications system.

3. A receiving apparatus for a mobile communications system, comprising:

a first receiving section configured to demodulate received signals of a first modulation type, the first receiving section comprising a frequency offset estimation unit; and

a second receiving section configured to demodulate received signals of a second modulation type, the second receiving section comprising a frequency correction unit configured to correct the frequency offset;

wherein the first receiving section is connected to the second receiving section configured to transmit the estimated frequency offset from the first receiving section to the second receiving section; and

wherein the frequency offset estimation unit estimates the frequency offset by evaluation of a known bit sequence in a frequency-modulated received signal.

4. The receiving apparatus of claim 3, wherein

the first modulation type comprises a Gaussian Frequency Shift Keying modulation method;

the known bit sequence has the same number of 0 bits and 1 bits; and

the frequency offset estimation unit calculates the mean value of the demodulated Gaussian Frequency Shift Keying signals, and determines the frequency offset from the calculated mean value.

5. The receiving apparatus of claim 3, wherein the apparatus is used in a Bluetooth communications system.

6. A receiving apparatus for a mobile communications system, comprising:

a first receiving section configured to demodulate received signals of a first modulation type, the first receiving section comprising a frequency offset estimation unit; and

a second receiving section configured to demodulate received signals of a second modulation type, the second receiving section comprising a frequency correction unit configured to correct the frequency offset;

wherein the first receiving section is connected to the second receiving section configured to transmit the estimated frequency offset from the first receiving section to the second receiving section;

an analogue receiving section having an input connected to an antenna and having two outputs respectively connected to the first receiving section and to the second receiving section;

a mixer configured to mix the analogue received signal to an intermediate frequency, or directly to baseband;

wherein the received signal which has been mixed to an intermediate frequency or directly to baseband is supplied to a first input of the frequency correction unit and a signal which represents the estimated frequency offset is supplied to a second input of the frequency correction unit; and

wherein the received signal which has been mixed to an intermediate frequency is supplied to the first input of the frequency correction unit, and a signal which represents the sum of the frequency offset and the intermediate frequency is supplied to the second input of the frequency correction unit.

7. The receiving apparatus of claim 6, wherein the frequency correction unit comprises a digital frequency correction unit, the received signal which has been mixed to the intermediate frequency or directly to baseband is supplied to an analogue/digital (A/D) converter, and the output of the A/D converter is connected to the first input of the digital frequency correction unit.

8. A receiving apparatus for a mobile communications system, comprising:

a first receiving section configured to demodulate received signals of a first modulation type, the first receiving section comprising a frequency offset estimation unit;

a second receiving section configured to demodulate received signals of a second modulation type, the second receiving section comprising a frequency correction unit configured to correct the frequency offset;

wherein the first receiving section is connected to the second receiving section configured to transmit the estimated frequency offset from the first receiving section to the second receiving section;

an analogue receiving section having an input connected to an antenna and having two outputs respectively connected to the first receiving section and to the second receiving section;

a mixer configured to mix the analogue received signal to an intermediate frequency, or directly to baseband;

wherein the received signal which has been mixed to an intermediate frequency or directly to baseband is supplied to a first input of the frequency correction unit and a signal which represents the estimated frequency offset is supplied to a second input of the frequency correction unit;

a first frequency correction unit and a second frequency correction unit;

wherein the received signal which has been mixed to an intermediate frequency is supplied to a first input of the first frequency correction unit and a signal which represents the intermediate frequency is supplied to a second input of the first frequency correction unit; and

wherein the output signal from the first frequency correction unit is supplied directly or indirectly to a first input of the second frequency correction unit, and a signal which represents the frequency offset is supplied to a second input of the second frequency correction unit.

9. The receiving apparatus of claim 8, wherein the frequency correction unit comprises a digital frequency correction unit, the received signal which has been mixed to the intermediate frequency or directly to baseband is supplied to an analogue/digital (A/D) converter, and the output of the A/D converter is connected to the first input of the digital frequency correction unit.

10. The receiving apparatus of claim 9, wherein the digital frequency correction unit corrects the frequency based on a Coordinate Rotation Digital Computer algorithm.

11. A receiving apparatus for a mobile communications system, comprising:

a first receiving section configured to demodulate received signals of a first modulation type, the first receiving section comprising a frequency offset estimation unit;

a second receiving section configured to demodulate received signals of a second modulation type, the second receiving section comprising a frequency correction unit configured to correct the frequency offset;

wherein the first receiving section is connected to the second receiving section configured to transmit the estimated frequency offset from the first receiving section to the second receiving section;

an analogue receiving section having an input connected to an antenna and having two outputs respectively connected to the first receiving section and to the second receiving section;

a mixer configured to mix the analogue received signal to an intermediate frequency, or directly to baseband;

wherein the received signal is mixed by the mixer to the intermediate frequency, and the output signal from the mixer is supplied to a polyphase filter, the polyphase filter is connected to a filter matching unit which is connected to a frequency error calculation unit;

wherein a first frequency correction unit and a second frequency correction unit are provided;

wherein the received signal which has been mixed to an intermediate frequency is supplied to a first input of the first frequency correction unit, and a signal that represents the sum of the intermediate frequency and the frequency error calculated by the frequency error calculation unit is supplied to a second input of the first frequency correction unit; and

wherein a signal that represents the frequency offset is supplied to the second frequency correction unit.

12. A receiving apparatus for a mobile communications system, comprising:

a first receiving section configured to demodulate received signals of a first modulation type, the first receiving section comprising a frequency offset estimation unit; and

a second receiving section configured to demodulate received signals of a second modulation type, the second receiving section comprising a frequency correction unit configured to correct the frequency offset;

wherein the first receiving section is connected to the second receiving section configured to transmit the estimated frequency offset from the first receiving section to the second receiving section; and

wherein the receiving apparatus is configured for burst data transmission, and the frequency offset estimation unit is operable to estimate the frequency offset in one example, once and only once for the duration of a burst, and the frequency correction unit is operable to perform the correction based on the frequency offset that has been supplied from the frequency offset estimation unit throughout the duration of the burst.

13. The receiving apparatus of claim 12, wherein the second modulation type comprises a phase modulation method, and wherein a phase correction unit is arranged in the signal path downstream from the frequency correction unit in the second receiving section, and is operable to continuously compensate for any drift in the frequency offset, based on phase corrections by the phase correction unit.

14. The receiving apparatus of claim 13, further comprising:

a delay demodulator configured to produce phase difference values of sample values that are separated by the time duration of a data symbol; and

wherein the phase difference values are supplied to the phase correction unit.

15. A receiving apparatus for a mobile communications system, comprising:

a first receiving section configured to demodulate received signals of a first modulation type, the first receiving section comprising a frequency offset estimation unit;

a second receiving section configured to demodulate received signals of a second modulation type, the second receiving section comprising a frequency correction unit configured to correct the frequency offset; and

an analogue receiving section having an input connected to an antenna and having two outputs respectively connected to the first receiving section and to the second receiving section; and

wherein the first receiving section is connected to the second receiving section, and is configured to transmit the estimated frequency offset from the first receiving section to the second receiving section; and

wherein the first modulation type comprises a two-value frequency modulation method, and the second modulation type comprises a modulation method having an M-value greater than or equal to 4.

16. The receiving apparatus of claim 15, further comprising a mixer configured to mix the analogue received signal to an intermediate frequency, or directly to baseband.

17. A receiving apparatus for a mobile communications system, comprising:

a first receiving section configured to demodulate received signals of a first modulation type, the first receiving section comprising a frequency offset estimation unit;

a second receiving section configured to demodulate received signals of a second modulation type, the second receiving section comprising a frequency correction unit configured to correct the frequency offset; and

an analogue receiving section having an input connected to an antenna and having two outputs respectively connected to the first receiving section and to the second receiving section; and

wherein the first receiving section is connected to the second receiving section, and is configured to transmit the estimated frequency offset from the first receiving section to the second receiving section; and

wherein the frequency offset estimation unit estimates the frequency offset by evaluation of a known bit sequence in a frequency-modulated received signal.

18. The receiving apparatus of claim 17, wherein the first modulation type comprises a Gaussian Frequency Shift Keying modulation method;

the known bit sequence has the same number of 0 bits and 1 bits; and

the frequency offset estimation unit calculates the mean value of the demodulated Gaussian Frequency Shift Keying signals, and determines the frequency offset from the calculated mean value.

19. The receiving apparatus of claim 17, further comprising a mixer configured to mix the analogue received signal to an intermediate frequency, or directly to baseband.

20. The receiving apparatus of claim 19, wherein the digital frequency correction unit corrects the frequency based on a Coordinate Rotation Digital Computer algorithm.