Frequency changer and digital tuner
View Patent ↗A zero or near zero IF frequency changer for use in a digital tuner comprises multipliers which receive the RF input signal from an input. The multipliers receive quadrature local oscillator signals from a first oscillator of an arrangement which comprises first and second phase-locked loops. The first phase-locked loop comprises a programmable divider, a comparator and a control loop so that the first oscillator is phase-locked to a second oscillator. A second phase-locked loop comprises the second oscillator and a synthesizer containing a reference oscillator to which the second oscillator is phase-locked. The output frequency of the second oscillator is in a frequency band which is outside the RF input frequency band of the frequency changer.
1. A digital tuner comprising a single frequency changer of one of a zero intermediate frequency changer and a near-zero intermediate frequency changer, said frequency changer comprising: an oscillator arrangement; a first multiplier having a first input for receiving an input signal in a first frequency band, and a second input connected to said oscillator arrangement; and said oscillator arrangement comprising a first oscillator for supplying a first signal in said first frequency band to said second input of said first multiplier, said first oscillator having a control input a second oscillator for producing a second signal in a second frequency band outside said first frequency band, said first and second oscillators forming part of a first phase-locked loop which comprises a first programmable divider, a first comparator having an output, a first input connected via said first programmable divider to said first oscillator, and a second input connected to said second oscillator, and a first control loop connected between said output of said first comparator and said control input of said first oscillator, said first control loop comprising an amplifier and a loop filter whose bandwidth is at least as large as the bandwidth of the input signals supplied to an antenna input, and a fixed frequency reference oscillator, said first oscillator being phase-locked to said second oscillator, and said second oscillator being phase-locked to said reference oscillator.
2. The tuner as claimed in claim 1 , in which said second frequency band is lower than said first frequency band.
3. The tuner as claimed in claim 1 , in which said first frequency band is within 950 to 2150 MHz.
4. The tuner as claimed in claim 1 , in which said second frequency band is within a UHF band.
5. The tuner as claimed in claim 4 , in which said second frequency band is within 400 to 600 MHz.
6. The tuner as claimed in claim 1 , comprising a low pass filter, said first multiplier having an output for supplying an output signal to said low pass filter.
7. The tuner as claimed in claim 6 , in which said low pass filter has a cut-off frequency of between 5 MHz and 40 MHz.
8. The tuner as claimed in claim 1 , comprising a second multiplier having a first input for receiving said input signal, and a second input connected to said oscillator arrangement for receiving a quadrature signal which is in quadrature with said first signal.
9. The tuner as claimed in claim 8 , comprising a phase adjusting network, to which said first oscillator is connected, for forming said first signal and said quadrature signal.
10. The tuner as claimed in claim 8 , in which said first oscillator comprises a ring oscillator having first and second outputs for supplying said first signal and said quadrature signal.
11. Th tuner as claimed in claim 1 , in which said first programmable divider has selectable divisors of two, three and four.
12. The tuner as claimed in claim 1 , in which said second oscillator has a control input, and said second and reference oscillators form part of a second phase-locked loop comprising: a second programmable divider; a third programmable divider; a second comparator having an output, a first input connected via said second programmable divider to said second oscillator, and a second input connected via said third programmable divider to said reference oscillator; and a second control loop connected between said output of said second comparator and said control input of said second oscillator.
13. The tuner as claimed in claim 1 , in which said first multiplier and said oscillator arrangement are formed in a monolithic integrated circuit.
14. A frequency changer of one of a zero intermediate frequency changer and a near-zero intermediate frequency changer, comprising: an oscillator arrangement; a first multiplier having a first input for receiving an input signal in a first frequency band, and a second input connected to said oscillator arrangement; and said oscillator arrangement comprising a first oscillator for supplying a first signal in said first frequency band to said second input of said first multiplier, a second oscillator for producing a second signal in a second frequency band outside said first frequency band, and a reference oscillator, said first oscillator being phase-locked locked to said second oscillator, said second oscillator being phase-locked to said reference oscillator, said first oscillator having a control input, and said first and second oscillators forming part of a first phase-locked loop comprising: a first programmable divider having selectable divisors of two, three and four; a first comparator having an output, a first input connected via said first programmable divider to said first oscillator, and a second input connected to said second oscillator; and a first control loop connected between said output of said first comparator and said control input of said first oscillator, said first control loop comprising an amplifier and a loop filter whose bandwidth is at least as large as the bandwidth of the input signals supplied to an antenna input.
15. The frequency changer as claimed in claim 14 , in which said second frequency band is lower than said first frequency band.
16. The frequency changer as claimed in claim 14 , in which said first frequency band is within 950 to 2150 MHz.
17. The frequency changer as claimed in claim 14 , in which said second frequency band is within a UHF band.
18. The frequency changer as claimed in claim 17 , in which said second frequency band is within 400 to 600 MHz.
19. The frequency changer as claimed in claim 14 , comprising a low pass filter, said first multiplier having an output for supplying an output signal to said low pass filter.
20. The frequency changer as claimed in claim 19 , in which said low pass filter has a cut-off frequency of between 5 MHz and 40 MHz.
21. The frequency changer as claimed in claim 14 , comprising a second multiplier having a first input for receiving said input signal, and a second input connected to said oscillator arrangement for receiving a quadrature signal which is in quadrature with said first signal.
22. The frequency changer as claimed in claim 21 , comprising a phase adjusting network, to which said first oscillator is connected, for forming said first signal and said quadrature signal.
23. The frequency changer as claimed in claim 21 , in which said first oscillator comprises a ring oscillator having first and second outputs for supplying said first signal and said quadrature signal.
24. The frequency changer as claimed in claim 21 , in which said second oscillator has a control input, and said second and reference oscillators form part of a second phase-locked loop comprising: a second programmable divider; a third programmable divider; a second comparator having an output, a first input connected via said second programmable divider to said second oscillator, and a second input connected via said third programmable divider to said reference oscillator; and a second control loop connected between said output of said second comparator and said control input of said second oscillator.
25. The frequency changer as claimed in claim 14 , in which said first multiplier and said oscillator arrangement are formed in a monolithic integrated circuit.
26. A frequency changer of one of a zero intermediate frequency changer and a near-zero intermediate frequency changer, comprising: an oscillator arrangement; a first multiplier having a first input for receiving an input signal in a first frequency band, and a second input connected to said oscillator arrangement; and said oscillator arrangement comprising a first oscillator for supplying a first signal in said first frequency band to said second input of said first multiplier, a second oscillator for producing a second signal in a second frequency band outside said first frequency band, and a reference oscillator, said first oscillator being phase-locked to said second oscillator, said second oscillator being phase-locked to said reference oscillator, said first oscillator having a control input, and said first and second oscillators forming part of a first phase-locked loop comprising: a first programmable divider; a first comparator having an output, a first input connected via said first programmable divider to said first oscillator, and a second input connected to said second oscillator; and a first control loop connected between said output of said first comparator and said control input of said first oscillator, said first control loop comprising an amplifier and a loop filter whose bandwidth is at least as large as the bandwidth of the input signals supplied to an antenna input.
27. The frequency changer as claimed in claim 16 , in which said second frequency band is lower than said first frequency band.
28. The frequency changer as claimed in claim 27 , in which said first frequency band is within 950 to 2150 MHz.
29. The frequency changer as claimed in claim 26 , in which said second frequency band is within a UHF band.
30. The frequency changer as claimed in claim 29 , in which said second frequency band is within 400 to 600 MHz.
31. The frequency changer as claimed in claim 26 , comprising a low pass filter, said first multiplier having an output for supplying an output signal to said low pass filter.
32. The frequency changer as claimed in claim 31 , in which said low pass filter has a cut-off frequency of between 5 MHz and 40 MHz.
33. The frequency changer as claimed in claim 26 , comprising a second multiplier having a first input for receiving said input signal, and a second input connected to said oscillator arrangement for receiving a quadrature signal which is in quadrature with said first signal.
34. The frequency changer as claimed in claim 33 , comprising a phase adjusting network, to which said first oscillator is connected, for forming said first signal and said quadrature signal.
35. The frequency changer as claimed in claim 33 , in which said first oscillator comprises a ring oscillator having first and second outputs for supplying said first signal and said quadrature signal.
36. The frequency changer as claimed in claim 26 , in which said first programmable divider has selectable divisors of two, three and four.
37. The frequency changer as claimed in claim 26 , in which said second oscillator has a control input, and said second and reference oscillators form part of a second phase-locked loop comprising: a second programmable divider; a third programmable divider; a second comparator having an output, a first input connected via said second programmable divider to said second oscillator, and a second input connected via said third programmable divider to said reference oscillator; and a second control loop connected between said output of said second comparator and said control input of said second oscillator.
38. The frequency changer as claimed in claim 26 , in which said first multiplier and said oscillator arrangement are formed in a monolithic integrated circuit.