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 harmonics 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 in continuous fashion;
frequency translating said processed RF signal to a low IF signal, said low IF signal comprising an in-phase component and a quadrature component, wherein frequency translating said processed RF signal to a low IF signal is accomplished, at least in part, by mixing said RF signal with a plurality of harmonic reject mixers;
lowpass filtering the in-phase and quadrature components of said low IF signal;
frequency translating each of said low pass filtered in-phase and low pass filtered quadrature components of said low IF signal to a high IF signal having in-phase and quadrature components; and
converting said high IF in-phase and quadrature components to a digital signal.
2. The method of claim 1 wherein said processing said RF signal comprises bandpass filtering said RF signal with a filter comprising a switched filter structure with analog trim.
3. The method of claim 1 wherein said harmonic reject mixers operate on said RF signal to suppress harmonics associated with said harmonic reject mixers.
4. The method of claim 3 wherein said plurality of harmonic reject mixers comprises a first mixer stage and a second mixer stage.
5. The method of claim 4 wherein said first mixer stage generates said in-phase components of said low IF signal.
6. The method of claim 5 wherein said second mixer stage generates said quadrature component of said low IF signal.
7. The method of claim 4 wherein said first and second mixer stages each comprise a plurality of mixers, the signals of the first stage mixers being offset from the signals of the second stage mixers by ninety degrees.
8. A circuit for converting a wide portion of a received RF signal into an IF signal, said circuit comprising:
a bandpass filter comprising a switched filter structure with analog trim;
a down conversion stage operable to frequency translate said filtered RF signal to a low IF signal, said low IF signal comprising an in-phase component and a quadrature component;
a first lowpass filter for filtering the in-phase component of said low IF signal;
a second lowpass filter for filtering the quadrature component of said low IF signal; and
at least one analog-to-digital converter, said at least one analog-to-digital converter operable to convert said in-phase and quadrature components into digital signals.
9. The circuit of claim 8 wherein said bandpass filter is operable to filter said RF signal prior to said down conversion stage.
10. The circuit of claim 8 wherein said down-conversion stage comprises a plurality of harmonic reject mixers.
11. The circuit of claim 10 wherein the signals of said harmonic reject mixers operate on said RF signal to suppress harmonics associated with said harmonic reject mixers.
12. The circuit of claim 10 wherein said plurality of harmonic reject mixers comprises a parallel mixers.
13. The circuit of claim 12 wherein a first mixer of said parallel mixers generates said in-phase components of said IF signal.
14. The circuit of claim 13 wherein said second mixer of said parallel mixers generates said quadrature component of said IF signal.