Television – Receiver circuitry – Tuning
Reexamination Certificate
2000-02-01
2003-10-28
Miller, John (Department: 2614)
Television
Receiver circuitry
Tuning
C348S732000, C348S725000, C348S705000, C348S706000
Reexamination Certificate
active
06639630
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to TV-signal receiving tuners, and more particularly, to a TV-signal receiving tuner for both VHF and UHF frequency bands, which prevents an oscillation signal of a local oscillator in the TV-signal receiving tuner from leaking.
2. Description of the Related Art
FIG. 6
shows a conventional TV-signal receiving tuner. This V-U integrated-type TV-signal receiving tuner is formed by integrating a VHF-band TV-signal receiving tuner and a UHF-band TV-signal receiving tuner into one unit, and includes a VHF-band input terminal
31
, a VHF-band high-frequency circuit section
32
, a VHF-band frequency converter
33
, a UHF-band input terminal
34
, a UHF-band high-frequency circuit section
35
, a UHF-band frequency converter
36
, an intermediate-frequency amplifier
37
, a band switcher
38
, and an output terminal
39
. The VHF-band frequency converter
33
has a VHF-band mixer
40
and a VHF-band local oscillator
41
. The UHF-band frequency converter
36
has a UHF-band mixer
42
and a UHF-band local oscillator
43
.
The VHF-band high-frequency circuit section
32
includes a high-frequency amplifier, a tuning circuit, and a filter none of them are shown), selects a VHF-band TV signal to be received, and amplifies it.
In the same way, the UHF-band high-frequency circuit section
35
includes a high-frequency amplifier, a tuning circuit, and a filter (none of them are shown), selects a UHF-band TV signal to be received, and amplifies it.
The band switcher
38
is connected to the VHF-band frequency converter
33
and to the UHF-band frequency converter
36
, and supplies a switching voltage to one of the VHF-band frequency converter
33
and the UHF-band frequency converter
36
according to the band to be received. When a VHF-band TV signal is to be received, the switching voltage is generated only at a first control terminal
44
, the switching voltage is supplied to the VHF-band frequency converter
33
, the VHF-band frequency converter
33
is set to an operating state, and the UHF-band frequency converter
36
is set to a not-operating state. When a UHF-band TV signal is to be received, the switching voltage is generated only at a second control terminal
45
, the switching voltage is supplied to the UHF-band frequency converter
36
, the UHF-band frequency converter
36
is set to an operating state, and the VHF-band frequency converter
33
is set to a not-operating state.
When a VHF-band TV signal is received, the VHF-band TV signal received at an antenna (not shown) passes through the VHF-band high-frequency circuit section
32
, is frequency-converted by the VHF-band mixer
40
and the VHF-band local oscillator
41
in the VHF-band frequency converter
33
, is amplified by the intermediate-frequency amplifier
37
as an intermediate-frequency signal IF, and is output from the output terminal
39
. The intermediate-frequency signal IF output from the output terminal
39
is detected by a detection circuit (not shown).
When a UHF-band TV signal is received, the UHF-band TV signal received at an antenna (not shown) passes through the UHF-band high-frequency circuit section
35
, is frequency-converted by the UHF-band mixer
42
and the UHF-band local oscillator
43
in the UHF-band frequency converter
36
, is amplified by the intermediate-frequency amplifier
37
as an intermediate-frequency signal IF, and is output from the output terminal
39
. The intermediate-frequency signal IF output from the output terminal
39
is detected by a detection circuit (not shown).
In the above conventional V-U integrated-type TV-signal receiving tuner, since the distances between the circuits are short, isolation between the VHF-band frequency converter
33
and the UHF-band frequency converter
36
cannot be sufficiently provided. Therefore, an oscillation signal generated by the local oscillator of an operating frequency converter leaks to the not-operating frequency converter, and is emitted from the antenna to the air to give disturbance to other receivers.
When a VHF-band TV signal is received, an oscillation signal generated by the VHF-band local oscillator
41
leaks to the UHF-band frequency converter
36
, and is emitted to the air through the UHF-band high-frequency circuit section
35
and the antenna. When a UHF-band TV signal is received, an oscillation signal generated by the UHF-band local oscillator
43
leaks to the VHF-band frequency converter
33
, and is emitted to the air through the VHF-band high-frequency circuit section
32
and the antenna.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a TV-signal receiving tuner which prevents a case in which an oscillation signal generated by an operating local oscillator leaks to an not-operating frequency converter and is emitted to the air through an antenna as extraneous emission to give disturbance to other receivers.
The foregoing object is achieved by the present invention through the provision of a TV-signal receiving tuner for both VHF and UHF frequency bands, including a VHF-band frequency converter having a VHF-band mixer and a VHF-band local oscillator, for converting a VHF-band TV signal to a signal having an intermediate frequency; a UHF-band frequency converter having a UHF-band mixer and a UHF-band local oscillator, for converting a UHF-band TV signal to a signal having an intermediate frequency; and a band switcher for selectively operating the VHF-band frequency converter or the UHF-band frequency converter, wherein a switch circuit is provided for at least one of a previous stage of the VHF-band frequency converter and a previous stage of the UHF-band frequency converter; and the switch circuit passes a high-frequency signal when a frequency converter at a subsequent stage of the switch circuit is operating, and does not pass a high-frequency signal when the frequency converter at the subsequent stage of the switch circuit is not operating.
Therefore, even if an oscillation signal generated by the local oscillator of the operating frequency converter leaks to the not-operating frequency converter, the oscillation signal is not emitted from the antenna to the air. Extraneous emission is suppressed.
The TV-signal receiving tuner may be formed such that a VHF-band high-frequency circuit section is provided at a previous stage of the VHF-band frequency converter; a UHF-band high-frequency circuit section is provided at a previous stage of the UHF-band frequency converter; and the switch circuit is provided at at least one of a location between the VHF-band high-frequency circuit section and the VHF-band frequency converter, and a location between the UHF-band high-frequency circuit section and the UHF-band frequency converter.
In this case, since the oscillation signal which causes extraneous emission can be blocked near the emission source, extraneous emission is effectively reduced.
The TV-signal receiving tuner may be formed such that the switch circuit is provided at at least one of a location immediately before the VHF-band frequency converter and a location immediately before the UHF-band frequency converter.
In this case, the switch circuit can be combined with the frequency converter and other circuits into an integrated circuit to make the circuit compact.
The TV-signal receiving tuner may be formed such that the switch circuit includes a transmission line to which an input end and an output end of the switch circuit are connected, and a transistor or a diode for making and breaking a connection between the transmission line and the ground is provided.
The TV-signal receiving tuner may be formed such that the switch circuit is provided with a transistor or a diode for making and breaking a connection between an input end and an output end of the switch circuit.
In this case, since the switch circuit is formed of a transistor or a diode, the switch circuit is made compact and extraneous emission is suppressed without increasing the volume of the tuner.
The TV-signal receiving
Osada Shigeru
Sato Yoshihiro
Yamamoto Masaki
Alps Electric Co. ,Ltd.
Desir Jean W.
Miller John
LandOfFree
TV-signal receiving tuner with reduced extraneous emission does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with TV-signal receiving tuner with reduced extraneous emission, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and TV-signal receiving tuner with reduced extraneous emission will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3114268