Broadband tuner for very wide signal conversion
View Patent ↗An agile RF tuner circuit capable of converting a wide portion of RF signal into an IF signal suitable for analog-to-digital conversion. The circuit up converts a received RF signal to a high IF signal and then down converts the high IF signal to a low IF signal. Embodiments of the RF circuit incorporate harmonic reject mixers to suppress harmonies and intermodulations typically associated with the frequency conversion process.
1. A method for converting a wide portion of a received RF signal into an IF signal, said method comprising:
processing said RF signal;
frequency translating said processed RF signal to a first IF signal, said first IF signal being higher than a second IF signal;
filtering said first IF signal with a plurality of filters, said filters operable, in combination, to ensure that said filtered first IF signal includes a minimum number of spurious products;
equalizing the spectral power of said filtered first IF signal;
frequency translating said filtered first IF signal to said second IF signal, said second IF signal being lower than said first IF signal;
wherein said processing said RF signal is accomplished, at least in part, with a filter comprising a switched filter structure with analog trim.
2. The method of claim 1 further comprising the step of bandpass filtering said second IF signal to further minimize undesirable signals in said filtered IF signal.
3. The method of claim 1 further comprising the step of lowpass filtering said second IF signal to further minimize undesirable signals in said filtered IF signal.
4. The method of claim 1 further comprising the step of converting said second IF signal into a digital signal.
5. The method of claim 1 wherein said frequency translating said processed RF signal to said first IF signal is accomplished, at least in part, by multiplying the processed RF signal by a first oscillator frequency.
6. The method of claim 1 wherein frequency translating said filtered first IF signal to said second IF signal is accomplished, at least in part, by multiplying the first IF signal by a second oscillator frequency.
7. The method of claim 6 , wherein said frequency translation of said filtered first IF signal is accomplished, at least in part, using an image rejection mixer.
8. The method of claim 1 , wherein said processing said RF signal is accomplished, at least in part, with an amplifier.
9. The method of claim 1 wherein a first filter of said plurality of filters is operable to filter a first frequency range of said first IF signal and a second filter of said plurality of filters is operable to filter a second frequency range of said first IF signal.
10. The method of claim 1 wherein at least one filter of said plurality of filters comprises a switched filter structure.
11. The method of claim 1 wherein said equalizing is accomplished using a feedback signal from a demodulator, said demodulator operable to detect a change in said spectral power of said filtered first IF signal.
12. A circuit for converting a wide portion of a received RF signal into an IF signal, said circuit comprising:
an up-conversion stage operable to translate an RF signal to a first IF signal, said first IF signal being higher than a second IF signal;
a plurality of filters operable to filter said first IF signal such that said first IF signal substantially free of spurious emission;
a slope adjustment circuit operable to equalize the spectral power of said filtered first IF signal;
a down-conversion stage operable to translate said filtered first IF signal to said second IF signal, said second IF signal being lower than said first IF signal;
wherein said first bandpass filter comprises a switched filter structure with analog trim.
13. The circuit of claim 12 further comprising a first bandpass filter operable to filter said RF signal prior to said up-conversion stage.
14. The circuit of claim 12 further comprising a bandpass filter operable to filter said low second IF signal.
15. The circuit of claim 12 further comprising a lowpass filter operable to filter said low second IF signal.
16. The circuit of claim 12 further comprising an analog-to-digital converter, said analog-to-digital converter operable to convert said second IF signal into a digital signal.
17. The circuit of claim 12 wherein said up-conversion stage comprises a local oscillator, said local oscillator having a frequency above the frequency of said RF signal.
18. The circuit of claim 12 wherein said down-conversion stage comprises a local oscillator, said local oscillator having a frequency lower than the frequency of said first IF signal.
19. The method of claim 18 , wherein said down-conversion stage comprises an image rejection mixer.
20. The circuit of claim 12 wherein a first filter of said plurality of filters is operable to filter a first frequency range of said first IF signal and a second filter of said plurality of filters is operable to filter a second frequency range of said first IF signal.
21. The circuit of claim 12 wherein at least one filter of said plurality of filters comprises a switched filter structure.
22. The circuit of claim 12 wherein said equalizing is accomplished using a feedback signal from a demodulator, said demodulator operable to detect a change in said spectral power of said filtered first IF signal.