TRANSMITTER AND SEMICONDUCTOR INTEGRATED CIRCUIT AVAILABLE FOR IT

• US 20110059704A1
• Filed: 08/11/2010
• Published: 03/10/2011
• Est. Priority Date: 09/10/2009
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: YAMAWAKI, Taizo, AKAMINE, Yukinori, MAEDA, Koji, NORIMATSU, Takayasu
• Granted Patent: US 8,442,461 B2
• Time in Patent Office: Days
• US Class Current: 455/110
• CPC Class Codes: H03C 5/00 Amplitude modulation and angle modulation produced simultaneously or at will by the same modulating signal H03C7/00 takes precedence
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths
• CPC Class Codes: H04B 2001/0491 with frequency synthesizers, frequency converters or modulators

Abstract

The transmitter synthesizes amplitude and phase components and calibrates a delay mismatch between amplitude and phase components with high accuracy at high speed. The transmitter has: a digital-to-analog converter (DAC) and a low-pass filter (LPF) in its amplitude-signal path; and a phase modulator operable to convert up a phase component into an RF component in its phase-signal path. In an operation of delay calibration, a test input signal is supplied to a delay-calibrating unit in the amplitude-signal path, and the delay-calibrating unit provides a test input signal to DAC. Then, LPF generates a test output signal. The delay-calibrating unit detects a delay of the test output signal relative to the test input signal, calibrates an amplitude signal delay in a range from the input of the delay-calibrating unit to the output of LPF, reduces the difference between amplitude and phase signal delays of the phase modulator in the phase-signal path.

Claims

1. A transmitter operable to synthesize amplitude and phase components, comprising:

an amplitude-signal path along which the amplitude component is conveyed; and

a phase-signal path along which the phase component is conveyed,

wherein the amplitude-signal path includes a digital-to-analog converter operable to respond the amplitude component, and a low-pass filter supplied with an output of the digital-to-analog converter,

the phase-signal path includes a phase modulator operable to convert the phase component up into a radio frequency component,

the amplitude-signal path further includes a delay-calibrating unit connected with an input of the digital-to-analog converter,

in an operation of delay calibration, the delay-calibrating unit provides a test input signal to the input of the digital-to-analog converter on receipt of supply of the test input signal to an input thereof,

in the operation of delay calibration, the delay-calibrating unit detects a delay of a test output signal coming out of an output of the low-pass filter with respect to the test input signal on receipt of supply of the test output signal, and

in the operation of delay calibration, the delay-calibrating unit calibrates an amplitude signal delay from the input of the delay-calibrating unit to the output of the low-pass filter in the amplitude-signal path in response to the test output signal delay, whereby a difference between the amplitude signal delay and a phase signal delay of the phase modulator in the phase-signal path is reduced.

2. The transmitter according to claim 1, wherein the phase modulator has a phase-signal-delay-calibrating function for calibrating the phase signal delay into a predetermined value, and

in the operation of delay calibration, the phase signal delay of the phase modulator is calibrated into the predetermined value by the phase-signal-delay-calibrating function, and the delay-calibrating unit calibrates the amplitude signal delay in response to the delay of the test output signal, thereby to reduce a difference between the amplitude signal delay and phase signal delay.

3. The transmitter according to claim 2, further comprising a variable delay circuit connected between an output of the delay-calibrating unit in the amplitude-signal path and the input of the digital-to-analog converter,

wherein in the operation of delay calibration, the delay-calibrating unit controls, in quantity of delay, the variable delay circuit and the low-pass filter in response to the delay of the test output signal, thereby to calibrate the amplitude signal delay from the input of the delay-calibrating unit to the output of the low-pass filter.

4. The transmitter according to claim 3, wherein the phase modulator is composed of a phase-locked loop including a phase comparator, a charge pump, a loop filter, and a control oscillator, and

a charge/discharge current of the charge pump operable to charge and discharge the loop filter is adjusted by measuring an oscillation frequency of the control oscillator during a transient response operation of the phase-locked loop constituting the phase modulator, and the phase signal delay of the phase modulator can be calibrated into the predetermined value.

5. The transmitter according to claim 4, wherein the delay-calibrating unit includes a register, a digital comparator, a delay logic circuit, a phase comparator, an analog-voltage comparator, and a delay-adjust unit,

the digital comparator compares the test input signal with a digital value with a reference code set on the register,

the delay logic circuit generates a reference delay output signal in response to a compare-output signal from the digital comparator,

the analog-voltage comparator compares the test output signal at the output of the low-pass filter with a reference voltage, thereby to generate a voltage-compare-output signal,

the phase comparator generates a phase-difference-detection signal in response to the reference delay output signal generated by the delay logic circuit, and the voltage-compare-output signal generated by the analog-voltage comparator,

the delay-adjust unit generates a first delay control signal for controlling the quantity of delay of the variable delay circuit, and a second delay control signal for controlling the quantity of delay of the low-pass filter in response to the phase-difference-detection signal generated by the phase comparator, and

a voltage value of the reference voltage can be set to be substantially equal to a voltage value of an analog voltage which the digital-to-analog converter converts the reference code set on the register into.

6. The transmitter according to claim 5, further comprising a signal generator operable to supply the test input signal to the input of the delay-calibrating unit in the operation of delay calibration,

wherein the signal generator is activated to generate the test input signal at time of power-on of an information-communication terminal equipped with the transmitter, and in the operation of delay calibration before a transmit operation by use of the information-communication terminal, which makes possible to reduce a difference between the amplitude signal delay and phase signal delay.

7. The transmitter according to claim 6, further comprising a digital calculation system operable to convert an inphase signal and a quadrature signal of an orthogonal coordinate system which can be supplied through a digital interface, thereby to generate the amplitude component and the phase component,

wherein during the transmit operation, the amplitude component and phase component generated by the digital calculation system can be conveyed through the amplitude-signal path and phase-signal path respectively, and then synthesized, and

in the operation of delay calibration before the transmit operation, the phase signal delay of the phase modulator is calibrated into the predetermined value by the phase-signal-delay-calibrating function, and in parallel with this, the signal generator is activated to generate the test input signal, whereby the reduction of the difference between the amplitude signal delay and phase signal delay is enabled.

8. The transmitter according to claim 7, further comprising at least one of a mixer and regulator for synthesizing the amplitude component and phase component.

9. The transmitter according to claim 7, wherein the variable delay unit is composed of an equalizer having a waveform-equalizing function.

10. The transmitter according to claim 1, composed of a transmitter based on Polar Modulation system and arranged to be capable of coping with both cases where the inphase and quadrature signals of the orthogonal coordinate system, which can be supplied to the digital calculation system, are in conformity with GSM, and where the inphase and quadrature signals are in conformity with EDGE.

11. A semiconductor integrated circuit available for a transmitter operable to synthesize amplitude and phase components, comprising:

an amplitude-signal path along which the amplitude component is conveyed; and

a phase-signal path along which the phase component is conveyed,

wherein the amplitude-signal path includes a digital-to-analog converter operable to respond the amplitude component, and a low-pass filter supplied with an output of the digital-to-analog converter,

the phase-signal path includes a phase modulator operable to convert the phase component up into a radio frequency component,

the amplitude-signal path further includes a delay-calibrating unit connected with an input of the digital-to-analog converter,

in an operation of delay calibration, the delay-calibrating unit provides a test input signal to the input of the digital-to-analog converter on receipt of supply of the test input signal to an input thereof,

in the operation of delay calibration, the delay-calibrating unit detects a delay of a test output signal coming out of an output of the low-pass filter with respect to the test input signal on receipt of supply of the test output signal, and

in the operation of delay calibration, the delay-calibrating unit calibrates an amplitude signal delay from the input of the delay-calibrating unit to the output of the low-pass filter in the amplitude-signal path in response to the test output signal delay, whereby a difference between the amplitude signal delay and a phase signal delay of the phase modulator in the phase-signal path is reduced.

12. The semiconductor integrated circuit according to claim 11, wherein the phase modulator has a phase-signal-delay-calibrating function for calibrating the phase signal delay into a predetermined value, and

in the operation of delay calibration, the phase signal delay of the phase modulator is calibrated into the predetermined value by the phase-signal-delay-calibrating function, and the delay-calibrating unit calibrates the amplitude signal delay in response to the delay of the test output signal, thereby to reduce a difference between the amplitude signal delay and phase signal delay.

13. The semiconductor integrated circuit according to claim 12, further comprising a variable delay circuit connected between an output of the delay-calibrating unit in the amplitude-signal path and the input of the digital-to-analog converter,

wherein in the operation of delay calibration, the delay-calibrating unit controls, in quantity of delay, the variable delay circuit and the low-pass filter in response to the delay of the test output signal, thereby to calibrate the amplitude signal delay from the input of the delay-calibrating unit to the output of the low-pass filter.

14. The semiconductor integrated circuit according to claim 13, wherein the phase modulator is composed of a phase-locked loop including a phase comparator, a charge pump, a loop filter, and a control oscillator, and

a charge/discharge current of the charge pump operable to charge and discharge the loop filter is adjusted by measuring an oscillation frequency of the control oscillator during a transient response operation of the phase-locked loop constituting the phase modulator, and the phase signal delay of the phase modulator can be calibrated into the predetermined value.

15. The semiconductor integrated circuit according to claim 14, wherein the delay-calibrating unit includes a register, a digital comparator, a delay logic circuit, a phase comparator, an analog-voltage comparator, and a delay-adjust unit,

the digital comparator compares the test input signal with a digital value with a reference code set on the register,

the delay logic circuit generates a reference delay output signal in response to a compare-output signal from the digital comparator,

the analog-voltage comparator compares the test output signal at the output of the low-pass filter with a reference voltage, thereby to generate a voltage-compare-output signal,

the phase comparator generates a phase-difference-detection signal in response to the reference delay output signal generated by the delay logic circuit, and the voltage-compare-output signal generated by the analog-voltage comparator,

the delay-adjust unit generates a first delay control signal for controlling the quantity of delay of the variable delay circuit, and a second delay control signal for controlling the quantity of delay of the low-pass filter in response to the phase-difference-detection signal generated by the phase comparator, and

a voltage value of the reference voltage can be set to be substantially equal to a voltage value of an analog voltage which the digital-to-analog converter converts the reference code set on the register into.

16. The semiconductor integrated circuit according to claim 15, further comprising a signal generator operable to supply the test input signal to the input of the delay-calibrating unit in the operation of delay calibration,

wherein the signal generator is activated to generate the test input signal at time of power-on of an information-communication terminal equipped with the transmitter, and in the operation of delay calibration before a transmit operation by use of the information-communication terminal, which makes possible to reduce a difference between the amplitude signal delay and phase signal delay.

17. The semiconductor integrated circuit according to claim 16, further comprising a digital calculation system operable to convert an inphase signal and a quadrature signal of an orthogonal coordinate system which can be supplied through a digital interface, thereby to generate the amplitude component and the phase component,

wherein during the transmit operation, the amplitude component and phase component generated by the digital calculation system can be conveyed through the amplitude-signal path and phase-signal path respectively, and then synthesized, and

in the operation of delay calibration before the transmit operation, the phase signal delay of the phase modulator is calibrated into the predetermined value by the phase-signal-delay-calibrating function, and in parallel with this, the signal generator is activated to generate the test input signal, whereby the reduction of the difference between the amplitude signal delay and phase signal delay is enabled.

18. The semiconductor integrated circuit according to claim 17, further comprising at least one of a mixer and regulator for synthesizing the amplitude component and phase component.

19. The semiconductor integrated circuit according to claim 17, wherein the variable delay unit is composed of an equalizer having a waveform-equalizing function.

20. The semiconductor integrated circuit according to claim 11, on condition that the transmitter which the semiconductor integrated circuit is available for is composed of a transmitter based on Polar Modulation system and arranged to be capable of coping with both cases where the inphase and quadrature signals of the orthogonal coordinate system, which can be supplied to the digital calculation system, are in conformity with GSM, and where the inphase and quadrature signals are in conformity with EDGE.