Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Reexamination Certificate
1999-09-20
2002-06-04
Trost, William (Department: 2683)
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
C455S232100, C455S241100, C455S245200, C455S253200, C330S133000
Reexamination Certificate
active
06400933
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a tuner for receiving an input signal and supplying an output signal, comprising and input amplifier, an mixer coupled to the input amplifier for supplying an IF signal, and a multi-stage amplifier for amplifying the IF signal, the multi-stage amplifier comprising a series arrangement of at least two gain stages, and supplying the output signal, and gain control means for controlling the multistage amplifier.
The invention also relates to a cascaded current comparator for use in a multistage amplifier.
2. Description of the Related Art
Such a tuner is known from U.S. Pat. No. 5,210,504. Therein, a tuner is described for satellite broadcasting.
Such a tuner is also known from the article “Monolithic TV IF system TBA 440”, E. Schatter, IEEE Transactions on BTR, Vol. 18, August 1972, pages 158-163. In the above-mentioned article, an (IF) amplifier has been described comprising a series arrangement of three gain stages.
A disadvantage of the prior-art tuner is that such a tuner adds noise and distortion to the input signal, especially at a low gain with several gain stages in series.
SUMMARY OF THE INVENTION
An object of the invention is to overcome the disadvantages of the prior-art tuner.
To this end, a first aspect of the invention provides a tuner as described above, characterized in that the multistage amplifier further comprises switching means parallel to the gain stages for shunting at least one of the gain stage.
A second aspect of the invention provides a multi-stage amplifier for use in a tuner as described above. By shunting the unnecessary gain stage/stages, the problem of the tuners and/or amplifiers of the prior art are overcome.
A third aspect of the invention provides a cascaded current comparator for use in a multi-stage amplifier as described above, in which inactive stages are turned off. By turning off inactive stages, current dissipation is reduced resulting in a low-power cascaded current comparator.
An embodiment of a tuner according to the invention in which the multi-stage amplifier comprises at least three gain stages arranged in a series.
By using three gain stages the necessary gain range can be easily obtained, and at the same time the complexity of the amplifier is kept within reasonable proportions.
An embodiment of a tuner according to the invention, characterized in that the switching means comprises a switch coupled in parallel with at least two gain stages.
By short-circuiting at least two gain stages together for the low gain range the distortion is further reduced.
An embodiment of a multistage amplifier according to the invention is characterized in that the multistage amplifier comprises a cascaded current comparator for generating tuning signal for the gain stages.
In this way a so-called thermometer code is obtained for supplying the tuning voltages of the gain stages.
REFERENCES:
patent: 3814843 (1974-06-01), Kruszewski
patent: 4794343 (1988-12-01), Yang
patent: 4910478 (1990-03-01), Koyama
patent: 5204977 (1993-04-01), Feldt
patent: 5210504 (1993-05-01), Yagita et al.
patent: 5233634 (1993-08-01), Vaisanen
patent: 5388078 (1995-02-01), Arakawa
patent: 5530405 (1996-06-01), Rydel
patent: 5638141 (1997-06-01), Bae et al.
patent: 5661434 (1997-08-01), Brozovich et al.
patent: 0777334 (1997-06-01), None
Monolithic TV IF System TBA 440, E. Schatter, IEEE Transactions on BTR, vol. 18, Aug. 1972, pp. 158-163.
Mensink Clemens H. J.
Van Lammeren Johannes P. M.
Biren Steven R.
Koninklijke Philips Electronics , N.V.
Nguyen Simon
Trost William
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