DC offset correction device and method

• US 20070176806A1
• Filed: 04/20/2006
• Published: 08/02/2007
• Est. Priority Date: 01/31/2006
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Ohba, Takeshi, Funyu, Yasuhito, Shako, Hideharu
• Granted Patent: US 7,352,308 B2
• Time in Patent Office: Days
• US Class Current: 341/118
• CPC Class Codes: H03C 3/406 using a feedback loop containing mixers or demodulators

Abstract

It is an object of the present invention to provide a DC offset correction means capable of correctly performing DC offset correction even when transmitting a non-modulation signal in radio communication equipment for performing orthogonal modulation by a direct RF modulation method. The DC offset correction device comprises a fixed value setting unit for setting a value for outputting a non-modulation signal with a specific phase from a modulator, a non-modulation signal switch unit for switching between a main signal and the value set by the fixed value setting unit and a DC offset correction control unit for sequentially changing the specific phase of the non-modulation signal outputted from the modulator by sequentially changing the value set by the fixed value setting unit and operating a DC offset correction value to be added to an input signal by a DC offset correction unit, based on feedback signal data generated from the non-modulation signal whose phase is sequentially changed.

Claims

1. A feedback type DC offset correction method of radio communication equipment for performing orthogonal modulation by a direct RF modulation method when the radio communication equipment transmits a non-modulation signal, comprising:

transmitting the non-modulation signal after changing its phase sequentially;

integrating feedback signals of the non-modulation signal transmitted after changing the phase; and

correcting DC offset by an integration value of the integrated feedback signals.

2. The DC offset correction method according to claim 1, wherein the non-modulation signal is transmitted after its phase is changed by a predetermined angle of one integer order of 360 degrees.

3. A DC offset correction device which applies a feedback type DC offset correction to radio communication equipment for performing orthogonal modulation by a direct RF modulation method and which comprises a DC offset correction unit for adding a DC offset correction value to its input signal and outputting it to an orthogonal modulator side, comprising:

a fixed value setting unit for setting a value for outputting a non-modulation signal with a specific phase from the modulator;

a non-modulation signal switch unit for switching between a main signal and the value set by the fixed value setting unit and outputting it; and

a DC offset correction control unit for sequentially changing the specific phase of the non-modulation signal outputted from the modulator by sequentially changing the value set by the fixed value setting unit and operating the DC offset correction value to be added to the input signal by the DC offset correction unit, based on the summed value of a plurality of pieces of feedback signal data generated from the non-modulation signal whose phase has been sequentially changed.

4. The DC offset correction device according to claim 3, wherein the radio communication equipment adopts a frequency multiplexing method and comprises the fixed value setting unit and non-modulation signal switch unit for each carrier of the frequency multiplexing method.

5. The DC offset correction device according to claim 3 or 4, wherein the DC offset correction control unit sequentially changes the value set by the fixed value setting unit in such a way as to sequentially change the phase of the non-modulation signal by a predetermined angle of one integer order of 360 degrees every time.

6. The DC offset correction device according to claim 3, wherein the fixed value setting unit comprises an I-channel signal amplitude value setting unit and a Q-channel signal amplitude value setting unit and the DC offset correction control unit makes a specific phase of the phase of the non-modulation signal by setting an I-channel signal amplitude value and a Q-channel signal amplitude value in the I-channel signal amplitude value setting unit and the Q-channel signal amplitude value setting unit, respectively.

7. A computer-readable storage medium on which is recorded a DC offset correction program for enabling a computer for the feedback type DC offset correction device according to claim 3 to execute a DC offset correction control process, comprising steps of:

initializing an accumulated integration value storage unit for storing a sum of a plurality of pieces of the feedback signal data;

instructing a demodulation unit for generating feedback data, based on the non-modulation signal to write feedback signal data in feedback memory;

reading the plurality of pieces of feedback signal data stored in the feedback memory and summing them;

reading the value stored in the accumulated integration value storage unit and storing a sum of the read value and the sum in the accumulated integration value storage unit;

setting a value for rotating a phase of a non-modulation signal currently being transmitted by n degrees being a predetermined angle of one integer order of 360 degrees in a phase setting unit;

determining whether the phase of the non-modulation signal has been rotated by (360−

n) degrees from the initial phase and branching it into the write instruction step if it has not been rotated; and

reading the value stored in the accumulated integration value storage unit and calculating a DC offset correction value based on the value.

8. A computer-readable storage medium on which is recorded a DC offset correction program for enabling a computer for the feedback type DC offset correction device according to claim 3 to execute a DC offset correction control process, comprising steps of:

initializing a first integration value storage unit and a second integration value storage unit which store the sum of the plurality of pieces of feedback signal data;

instructing a demodulation unit for generating feedback data, based on the non-modulation signal to write feedback signal data in feedback memory;

reading the plurality of pieces of feedback signal data stored in the feedback memory and summing them;

storing the sum in the first integration value storage unit;

setting a value for rotating a phase of a non-modulation signal currently being transmitted by 180 degrees in a phase setting unit;

instructing the demodulation unit to write the feedback signal data onto the feedback memory again;

reading the plurality of pieces of feedback signal data stored in the feedback memory and summing them;

storing the sum in the second integration value storage unit;

summing the values stored in the first integration value storage unit and the second integration value storage unit; and

calculating a DC offset correction value, based on the obtained sum.

9. A computer-readable storage medium on which is recorded a DC offset correction program for enabling a computer for the feedback type DC offset correction device according to claim 3 to execute a DC offset correction control process, comprising steps of:

initializing a first integration value storage unit and a second integration value storage unit which store the sum of the plurality of pieces of feedback signal data;

instructing a demodulation unit for generating feedback data, based on the non-modulation signal to write feedback signal data in feedback memory;

reading the plurality of pieces of feedback signal data stored in the feedback memory and summing them;

storing the sum in the first integration value storage unit;

sequentially setting a value for gradually rotating a phase of a non-modulation signal currently being transmitted up to 180 degrees in a phase setting unit;

instructing the demodulation unit to write the feedback signal data onto the feedback memory again;

reading the plurality of pieces of feedback signal data stored in the feedback memory and summing them;

storing the sum in the second integration value storage unit;

summing the values stored in the first integration value storage unit and the second integration value storage unit; and

calculating a DC offset correction value, based on the obtained sum.