POLAR MODULATOR WITH PATH DELAY COMPENSATION

• US 20090311979A1
• Filed: 07/14/2008
• Published: 12/17/2009
• Est. Priority Date: 06/12/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Atheros Communications Incorporated (Qualcomm, Inc.)
• Inventors: Weber, David J., Si, William W., Husted, Paul J., Zhang, Xiaoru
• Granted Patent: US 8,498,589 B2
• Time in Patent Office: Days
• US Class Current: 455/102
• 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 2001/0491 with frequency synthesizers, frequency converters or modulators

Abstract

A modulation system comprising a signal processing unit and a modulator. The signal processing unit may generate a low frequency modulator signal, a high frequency modulator signal, and a modulator amplitude control signal. The modulator may generate a modulated signal for transmission via a wireless network based, at least in part, on the low frequency modulator signal, the high frequency modulator signal, and the modulator amplitude control signal. The signal processing unit comprises a delay compensation unit for delaying the generation of the high frequency modulator signal and the modulator amplitude control signal based, at least in part, on signal generation and modulation path delays associated with the low frequency modulator signal to substantially align the modulator signals at the output of the modulation system.

Claims

1. A transmitter comprising:

a signal processing unit operable to generate a low frequency modulator signal and a high frequency modulator signal; and

a modulator coupled to the signal processing unit and operable to generate a modulated signal for transmission based, at least in part, on the low frequency modulator signal and the high frequency modulator signal;

wherein the signal processing unit comprises a delay compensation unit operable to delay the generation of the high frequency modulator signal based, at least in part, on signal generation and modulation path delays associated with the low frequency modulator signal.

2. The transmitter of claim 1, wherein the signal processing unit is further operable to generate a modulator amplitude control signal, wherein the modulator is operable to generate a modulated signal for transmission based, at least in part, on the low frequency modulator signal, the high frequency modulator signal, and the modulator amplitude control signal, and wherein the delay compensation unit is operable to delay the generation of the high frequency modulator signal and the modulator amplitude control signal based, at least in part, on signal generation and modulation path delays associated with the low frequency modulator signal.

3. The transmitter of claim 2, wherein the delay compensation unit is operable to delay the generation of the high frequency modulator signal based, at least in part, on a path delay difference between the signal generation and modulation path delays associated with the low frequency modulator signal and signal generation and modulation path delays associated with the high frequency modulator signal, and operable to delay the generation of the modulator amplitude control signal based, at least in part, on a path delay difference between the signal generation and modulation path delays associated with the low frequency modulator signal and signal generation and modulation path delays associated with the modulator amplitude control signal.

4. The transmitter of claim 3, wherein the delay compensation unit is operable to delay the generation of the high frequency modulator signal and the modulator amplitude control signal to substantially time align the low frequency modulator signal, the high frequency modulator signal, and the modulator amplitude control signal at an output of the modulator.

5. The transmitter of claim 1, wherein the signal processing unit comprises signal generation circuitry that is operative on a first clock domain and the modulator comprises modulator circuitry that is operative on a second clock domain, wherein the signal processing unit further comprises an interpolation unit coupled between the signal generation circuitry and the modulation circuitry, wherein the interpolation unit is operable to adapt the low frequency modulator signal from the first clock domain associated with the signal generation circuitry to the second clock domain associated with the modulation circuitry before being provided to the modulator.

6. The transmitter of claim 2, wherein the signal processing unit comprises signal generation circuitry that introduces a first generation path delay into the generation of the low frequency modulator signal, a second generation path delay into the generation of the high frequency modulator signal, and a third generation path delay into the generation of the modulator amplitude control signal, and wherein the modulator comprises modulator circuitry that introduces a first modulator path delay into processing of the low frequency modulator signal, a second modulator path delay into processing of the high frequency modulator signal, and a third modulator path delay into processing of the modulator amplitude control signal.

7. The transmitter of claim 6, wherein the delay compensation unit is operable to add a delay to the generation of the high frequency modulator signal based on a path delay difference between the generation and modulator path delays of the low frequency modulator signal and the generation and modulator path delays of the high frequency modulator signal, and operable to add a delay to the generation of the modulator amplitude control signal based on a path delay difference between the generation and modulator path delays of the low frequency modulator signal and the generation and modulator path delays of the modulator amplitude control signal.

8. The transmitter of claim 2, wherein the delay compensation unit comprises a delay generation unit and a synchronization unit, wherein the delay generation unit is operable to add a first programmable delay to the generation of the high frequency modulator signal and a second programmable delay to the generation of the modulator amplitude control signal, wherein the synchronization unit is operable to control an activation of the delay generation unit based, at least in part, on the generation of the low frequency modulator signal, wherein the synchronization unit is operable to delay the activation of the delay generation unit until the generation of the low frequency modulator signal.

9. The transmitter of claim 2, wherein the delay compensation unit comprises:

a fractional divider coupled to a first clock, wherein the fractional divider is operable to generate a second clock from the first clock by generating a first number of pulses during an interval having a second number of the first clock cycles; and

a dual port FIFO coupled to the fractional divider and operable to receive low frequency modulator data at an input port, wherein the low frequency modulator data is clocked into the input port by the second clock when a first control input is asserted, wherein the dual port FIFO is operable to generate the low frequency modulator signal at an output port based on the low frequency modulator data, wherein the output port of the dual port FIFO is clocked by a third clock operative on a different clock domain than the first clock.

10. The transmitter of claim 9, wherein the delay compensation unit further comprises:

a first synchronizer operable to receive the first control input at an input port, wherein the first synchronizer is clocked by the second clock, wherein the first synchronizer is operable to generate a first synchronizer output based on the first control input and the second clock;

a second synchronizer coupled to the first synchronizer and operable to receive the first synchronizer output at an input port, wherein the second synchronizer is clocked by the third clock, wherein the second synchronizer is operable to generate a second control signal based on the first synchronizer output and the third clock, wherein the second control signal is provided to the dual port FIFO to enable the output port; and

a third synchronizer coupled to the second synchronizer and operable to receive the second control signal at an input port, wherein the third synchronizer is clocked by the first clock, wherein the third synchronizer is operable to generate a third control signal based on the second control signal and the first clock.

11. The transmitter of claim 10, wherein the delay compensation unit further comprises a delay generation unit coupled to the third synchronizer and operable to receive the third control signal at an input port, wherein the third control signal enables the delay compensation unit, wherein the delay generation unit is operable to add a first programmable delay to the generation of the high frequency modulator signal and a second programmable delay to the generation of the modulator amplitude control signal.

12. The transmitter of claim 1, wherein the modulator is a polar modulator operable to perform two-point modulation.

13. The transmitter of claim 1, wherein the transmitter is operable to transmit the modulated signal via a wireless network.

14. A method for delay compensation in a modulator circuit of a transmitter, the method comprising:

initiating generation of a low frequency modulator signal, a high frequency modulator signal, and a modulator amplitude control signal;

delaying the generation of the high frequency modulator signal based, at least in part, on a path delay difference between signal generation and modulation path delays associated with the low frequency modulator signal and signal generation and modulation path delays associated with the high frequency modulator signal;

delaying the generation of the modulator amplitude control signal based, at least in part, on a path delay difference between the signal generation and modulation path delays associated with the low frequency modulator signal and signal generation and modulation path delays associated with the modulator amplitude control signal; and

generating a modulated signal for transmission based, at least in part, on the low frequency modulator signal, the high frequency modulator signal, and the modulator amplitude control signal.

15. The method of claim 14, wherein said delaying the generation of the high frequency modulator signal and the modulator amplitude control signal comprises delaying the generation of the high frequency modulator signal and the modulator amplitude control signal such that the low frequency modulator signal, the high frequency modulator signal, and the modulator amplitude control signal are substantially time aligned at an output of the modulator circuit.

16. A modulation system comprising:

a signal processing unit operable to generate a low frequency modulator signal, a high frequency modulator signal, and a modulator amplitude control signal; and

a modulator coupled to the signal processing unit and operable to generate a modulated signal based, at least in part, on the low frequency modulator signal, the high frequency modulator signal, and the modulator amplitude control signal;

wherein the signal processing unit comprises a delay compensation unit operable to delay the generation of the high frequency modulator signal and the modulator amplitude control signal based, at least in part, on signal generation and modulation path delays associated with the low frequency modulator signal.

17. The modulation system of claim 16, wherein the delay compensation unit is operable to delay the generation of the high frequency modulator signal based, at least in part, on a path delay difference between the signal generation and modulation path delays associated with the low frequency modulator signal and signal generation and modulation path delays associated with the high frequency modulator signal, and operable to delay the generation of the modulator amplitude control signal based, at least in part, on a path delay difference between the signal generation and modulation path delays associated with the low frequency modulator signal and signal generation and modulation path delays associated with the modulator amplitude control signal.

18. The modulation system of claim 17, wherein the delay compensation unit is operable to delay the generation of the high frequency modulator signal and the modulator amplitude control signal to substantially time align the low frequency modulator signal, the high frequency modulator signal, and the modulator amplitude control signal at an output of the modulator.

19. The modulation system of claim 16, wherein the signal processing unit comprises signal generation circuitry that is operative on a first clock domain and the modulator comprises modulator circuitry that is operative on a second clock domain, wherein the signal processing unit further comprises an interpolation unit coupled between the signal generation circuitry and the modulation circuitry, wherein the interpolation unit is operable to adapt the low frequency modulator signal from the first clock domain associated with the signal generation circuitry to the second clock domain associated with the modulation circuitry before being provided to the modulator.

20. The modulation system of claim 16, wherein the delay compensation unit comprises a delay generation unit and a synchronization unit, wherein the delay generation unit is operable to add a first programmable delay to the generation of the high frequency modulator signal and a second programmable delay to the generation of the modulator amplitude control signal, wherein the synchronization unit is operable to control an activation of the delay generation unit based, at least in part, on the generation of the low frequency modulator signal, wherein the synchronization unit is operable to delay the activation of the delay generation unit until the generation of the low frequency modulator signal.

21. The modulation system of claim 16, wherein the modulator is a polar modulator operable to perform two-point modulation.