Digital radio system and method of operation
View Patent ↗A digital radio system comprises a mixer and an analog-to-digital converter communicative coupled to the mixer. The mixer generates an intermediate frequency signal based at least in part upon a radio frequency signal and a local oscillator signal, wherein the intermediate frequency signal comprises a signal of interest having a particular bandwidth. The analog-to-digital converter generates a digital signal by quantizing the intermediate frequency signal using a sampling frequency that is greater than twice the bandwidth of the signal of interest and less than the frequency of the intermediate frequency signal.
1. A digital radio system, comprising:
a first mixer operable to generate an intermediate frequency signal based at least in part upon a radio frequency signal and a local oscillator signal, wherein the intermediate frequency signal comprises a signal of interest having a particular bandwidth;
an analog-to-digital converter communicatively coupled to the mixer and operable to generate a digital signal by quantizing the intermediate frequency signal using a sampling frequency that is greater than twice the bandwidth of the signal of interest and less than the frequency of the intermediate frequency signal; and
a second mixer communicatively coupled to the analog-to-digital converter, the second mixer operable to receive the digital signal and generate a baseband signal based at least in part upon a multiplication of the digital signal using (a) an in-phase component, I, of [1, −1, −1, and 1] and quadrature component, Q, of [1, 1, −1, and −1]; or (b) an in-phase component, I, of [1, 0, −1, and 0] and quadrature component, Q, of [0, 1, 0, and −1].
2. The digital radio system of claim 1 , wherein the digital signal is at a frequency that is one-quarter of the sampling frequency.
3. The digital radio system of claim 1 , wherein the sampling frequency comprises the frequency of the intermediate frequency signal divided by three and one-quarter.
4. The digital radio system of claim 1 , wherein the sampling frequency comprises the frequency of the intermediate frequency signal divided by four and one-quarter.
5. The digital radio system of claim 1 , wherein the sampling frequency comprises the frequency of the intermediate frequency signal divided by five and one-quarter.
6. The digital radio system of claim 1 , wherein the sampling frequency comprises the frequency of the intermediate frequency signal divided by six and one-quarter.
7. The digital radio system of claim 1 , wherein the digital signal is at a frequency that is the frequency of the intermediate frequency signal minus three times the sampling frequency.
8. The digital radio system of claim 1 , wherein the digital signal is at a frequency that is the frequency of the intermediate frequency signal minus four times the sampling frequency.
9. The digital radio system of claim 1 , wherein the digital signal is at a frequency that is the frequency of the intermediate frequency signal minus five times the sampling frequency.
10. The digital radio system of claim 1 , wherein the digital signal is at a frequency that is the frequency of the intermediate frequency signal minus six times the sampling frequency.
11. The digital radio system of claim 1 , wherein the second mixer comprises a part of a digital signal processing circuit communicatively.
12. The digital radio system of claim 1 , wherein the radio frequency signal comprises at least one of an AM signal, an FM signal, and a WX signal.
13. The digital radio system of claim 1 , wherein the mixer and the analog-to-digital converter reside on the same integrated circuit chip.
14. The digital radio system of claim 1 , wherein:
the frequency of the intermediate frequency signal comprises 12.0 MHz;
the sampling frequency comprises 1.920 MHz; and
the frequency of the digital signal comprises 480 kHz.
15. The digital radio system of claim 1 , wherein:
the frequency of the intermediate frequency signal comprises 11.025 MHz;
the sampling frequency comprises 1.764 MHz; and
the frequency of the digital signal comprises 441 kHz.
16. The digital radio system of claim 1 , wherein:
the frequency of the intermediate frequency signal comprises 10.7 MHz;
the sampling frequency comprises 1.712 MHz; and
the frequency of the digital signal comprises 428 kHz.
17. A method for processing a frequency signal, comprising:
generating an intermediate frequency signal based at least in part upon a radio frequency signal and a first local oscillator signal, wherein the intermediate frequency signal comprises a signal of interest having a particular bandwidth;
generating a digital signal by quantizing the intermediate frequency signal using a sampling frequency that is greater than twice the bandwidth of the signal of interest and less than the frequency of the intermediate frequency signal;
generating a second local oscillator signal based at least in part upon (a) an in-phase component, I, of [1, −1, −1, and 1] and quadrature component, Q, of [1, 1, −1, and −1]; or (b) an in-phase component, I, of [1, 0, −1, and 0] and quadrature component, Q, of [0, 1, 0, and −1];
mixing the digital signal and the second local oscillator signal; and
generating a baseband frequency signal in response to mixing the digital signal and the second local oscillator signal.
18. The method of claim 17 , wherein the digital signal is at a frequency that is one-quarter of the sampling frequency.
19. The method of claim 17 , wherein the sampling frequency comprises the frequency of the intermediate frequency signal divided by three and one-quarter.
20. The method of claim 17 , wherein the sampling frequency comprises the frequency of the intermediate frequency signal divided by four and one-quarter.
21. The method of claim 17 , wherein the sampling frequency comprises the frequency of the intermediate frequency signal divided by five and one-quarter.
22. The method of claim 17 , wherein the sampling frequency comprises the frequency of the intermediate frequency signal divided by six and one-quarter.
23. The method of claim 17 , wherein the digital signal is at a frequency that is the frequency of the intermediate frequency signal minus three times the sampling frequency.
24. The method of claim 17 , wherein the digital signal is at a frequency that is the frequency of the intermediate frequency signal minus four times the sampling frequency.
25. The method of claim 17 , wherein the digital signal is at a frequency that is the frequency of the intermediate frequency signal minus five times the sampling frequency.
26. The method of claim 17 , wherein the digital signal is at a frequency that is the frequency of the intermediate frequency signal minus six times the sampling frequency.
27. The method of claim 17 , wherein the radio frequency signal comprises at least one of an AM signal, an FM signal, and a WX signal.
28. The method of claim 17 , wherein generating the intermediate frequency signal and generating the digital signal are performed by circuit elements that reside on the same integrated circuit chip.
29. The method of claim 17 , wherein:
the frequency of the intermediate frequency signal comprises 12.0 MHz;
the sampling frequency comprises 1.920 MHz; and
the frequency of the digital signal comprises 480 kHz.
30. The method of claim 17 , wherein:
the frequency of the intermediate frequency signal comprises 11.025 MHz;
the sampling frequency comprises 1.764 MHz; and
the frequency of the digital signal comprises 441 kHz.
31. The method of claim 17 , wherein:
the frequency of the intermediate frequency signal comprises 10.7 MHz;
the sampling frequency comprises 1.712 MHz; and
the frequency of the digital signal comprises 428 kHz.
32. A method for processing a frequency signal, comprising:
receiving a radio frequency signal comprising a signal of interest having a particular bandwidth;
generating a digital signal by quantizing the radio frequency signal using a sampling frequency that is greater than twice the bandwidth of the signal of interest and less than the frequency of the radio frequency signal;
generating a local oscillator signal based at least in part upon (a) an in-phase component, I, of [1, −1, −1, and 1] and quadrature component, Q, of [1, 1, −1, and −1]; or (b) an in-phase component, I, of [1, 0, −1, and 0] and quadrature component, Q, of [0, 1, 0, and −1];
mixing the digital signal and the local oscillator signal; and
generating a baseband frequency signal in response to mixing the digital signal and the second local oscillator signal.
33. The method of claim 32 , wherein the digital signal is at a frequency that is one-quarter of the sampling frequency.
34. The method of claim 32 , wherein the sampling frequency comprises the frequency of the radio frequency signal divided by three and one-quarter.
35. The method of claim 32 , wherein the sampling frequency comprises the frequency of the radio frequency signal divided by four and one-quarter.
36. The method of claim 32 , wherein the sampling frequency comprises the frequency of the radio frequency signal divided by five and one-quarter.
37. The method of claim 32 , wherein the sampling frequency comprises the frequency of the radio frequency signal divided by six and one-quarter.
38. The method of claim 32 , wherein the digital signal is at a frequency that is the frequency of the radio frequency signal minus three times the sampling frequency.
39. The method of claim 32 , wherein the digital signal is at a frequency that is the frequency of the radio frequency signal minus four times the sampling frequency.
40. The method of claim 32 , wherein the digital signal is at a frequency that is the frequency of the radio frequency signal minus five times the sampling frequency.
41. The method of claim 32 , wherein the digital signal is at a frequency that is the frequency of the radio frequency signal minus six times the sampling frequency.
42. The method of claim 32 , wherein the radio frequency signal comprises at least one of an AM signal, an FM signal, and a WX signal.