Radio frequency tuner front end and tuner
View Patent ↗A front end for a radio frequency tuner, for example for connection to a cable distribution network, including an input connected to a signal path comprising an LNA connected via an AGC stage to a signal splitter. The input path has a bandwidth sufficiently wide to pass all of the channels in an input signal and has a substantially constant voltage standing wave ratio over the bandwidth. The splitter supplies identical signals to several filtering paths, each of which comprises a fixed filter. The paths are selectable one at a time and the filters divide the input frequency band into a plurality of contiguous or slightly overlapping sub-bands. The output of the front end is supplied to, for example, a double conversion arrangement comprising an upconverter and a downconverter with first and second IF filters.
1. A radio frequency tuner front end, comprising:
an input for receiving an input signal in an input band containing a plurality of channels;
filtering paths arranged to receive said input signal and having fixed frequency responses for dividing said input band into a plurality of sub-bands, each of which contains a plurality of said channels;
a signal path between said input and said filtering paths having a bandwidth sufficiently wide to pass said input band and a substantially constant voltage standing wave ratio over said bandwidth; and
a selecting arrangement for enabling any one of said filtering paths at a time to supply a filtered signal to a first mixer, wherein a first of said filtering paths for a lowest of said sub-bands has a low pass filtering response, a second of said filtering paths for a highest of said sub-bands has a high pass filtering response, and at least one other of said filtering paths has a bandpass filtering response.
2. A front end as claimed in claim 1 , in which ratios of an upper frequency limit to a lower frequency limit of said sub-bands are substantially equal to each other.
3. A front end as claimed in claim 2 , in which said ratios are substantially equal to two.
4. A front end as claimed in claim 1 , in which adjacent ones of said sub-bands are contiguous.
5. A front end as claimed in claim 1 , in which adjacent ones of said sub-bands overlap.
6. A front end as claimed in claim 1 , comprising two filtering paths.
7. A front end as claimed in claim 1 , in which each of said filtering paths has a bandpass filtering response.
8. A front end as claimed in claim 6 , in which said filtering paths comprise a lower path having a low pass filtering response and an upper path having a high pass filtering response.
9. A front end as claimed in claim 1 , in which said signal path comprises a buffer stage.
10. A front end as claimed in claim 9 , in which said buffer stage comprises a low noise amplifier.
11. A front end as claimed in claim 9 , in which said signal path comprises an automatic gain control arrangement between said buffer stage and said filtering paths.
12. A front end as claimed in claim 1 , further comprising a respective automatic gain control arrangement in each of said filtering paths.
13. A front end as claimed in claim 1 , in which said signal path comprises a signal splitter having outputs for driving said filtering paths.
14. A front end as claimed in claim 13 , in which said selecting arrangement is arranged to enable any one of said signal splitter outputs at a time.
15. A front end as claimed in claim 1 , comprising a single monolithic integrated circuit.
16. A tuner comprising:
a radio frequency tuner front end including:
an input for receiving an input signal in an input band containing a plurality of channels;
filtering paths arranged to receive said input signal and having fixed frequency responses for dividing said input band into a plurality of sub-bands, each of which contains a plurality of said channels;
a signal path between said input and said filtering paths having a bandwidth sufficiently wide to pass said input band and a substantially constant voltage standing wave ratio over said bandwidth; and
a selecting arrangement for enabling any one of said filtering paths at a time to supply a filtered signal to a first mixer, wherein in which a first of said filtering paths for a lowest of said sub-bands has a low pass filtering response, a second of said filtering paths for a highest of said sub-bands has a high pass filtering response, and at least one other of said filtering paths has a bandpass filtering response; and a first frequency changer.
17. A tuner as claimed in claim 16 , in which said selecting arrangement comprises individually enable input stages of said first frequency changer having inputs connected to outputs of said filtering paths.
18. A tuner as claimed in claim 16 , comprising a first intermediate frequency filter connected to an output of said first frequency changer.
19. A tuner as claimed in claim 16 , in which said first frequency changer is an upconverter.
20. A tuner as claimed in claim 16 , comprising a second frequency changer.
21. A tuner as claimed in claim 20 , in which said second frequency changer is a downconverter.
22. A tuner as claimed in claim 20 , comprising a second intermediate frequency filter connected to an output of said second frequency changer.
23. A tuner as claimed in claim 16 , comprising a single monolithic integrated circuit.
24. A tuner as claimed in claim 16 , comprising a cable tuner.