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 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; and
a digital signal processing circuit communicatively coupled to the analog-to-digital converter and operable to convert the digital signal to a baseband frequency by multiplying 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 sampling frequency is greater than twice the bandwidth of the signal of interest and less than the frequency of the intermediate frequency signal.
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 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; and
performing digital signal processing on the digital signal to convert the digital signal to a baseband frequency by mixing the digital signal with a signal that is 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].
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 sampling frequency is greater than twice the bandwidth of the signal of interest and less than the frequency of the intermediate frequency signal.
28. 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.
29. 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.
30. 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.
31. 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.
32. 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.
33. 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; and
performing digital signal processing on the digital signal to convert the digital signal to a baseband frequency by mixing the digital signal with a signal that is 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].
34. The method of claim 33 , wherein the digital signal is at a frequency that is one-quarter of the sampling frequency.
35. The method of claim 33 , wherein the sampling frequency comprises the frequency of the radio frequency signal divided by three and one-quarter.
36. The method of claim 33 , wherein the sampling frequency comprises the frequency of the radio frequency signal divided by four and one-quarter.
37. The method of claim 33 , wherein the sampling frequency comprises the frequency of the radio frequency signal divided by five and one-quarter.
38. The method of claim 33 , wherein the sampling frequency comprises the frequency of the radio frequency signal divided by six and one-quarter.
39. The method of claim 33 , wherein the digital signal is at a frequency that is the frequency of the radio frequency signal minus three times the sampling frequency.
40. The method of claim 33 , wherein the digital signal is at a frequency that is the frequency of the radio frequency signal minus four times the sampling frequency.
41. The method of claim 33 , wherein the digital signal is at a frequency that is the frequency of the radio frequency signal minus five times the sampling frequency.
42. The method of claim 33 , wherein the digital signal is at a frequency that is the frequency of the radio frequency signal minus six times the sampling frequency.
43. The method of claim 33 , wherein the sampling frequency is greater than twice the bandwidth of the signal of interest and less than the frequency of the intermediate frequency signal.
44. The method of claim 33 , wherein the radio frequency signal comprises at least one of an AM signal, an FM signal, and a WX signal.