Television – Receiver circuitry – Tuning
Reexamination Certificate
1998-06-09
2002-02-26
Hsia, Sherrie (Department: 2614)
Television
Receiver circuitry
Tuning
C348S729000
Reexamination Certificate
active
06351294
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a television signal receiving tuner, and more particularly to an input circuit unit for a television signal receiving tuner in the U.S. specification, which is utilized for use on a vehicle and/or for used in a personal computer, and which is also adapted to receive Frequency Modulation (FM) broadcasting signals.
2. Description of the Related Art
A conventional television signal receiving tuner in the U.S. specification (hereinafter, it is simply referred to as a tuner) will be described with reference to
FIGS. 4 and 5
.
FIG. 4
shows an input circuit unit for a conventional tuner, and
FIG. 5
shows a selectivity characteristic for a part of the input circuit unit shown in FIG.
4
. First, in
FIG. 4
, a VHF input circuit unit is constituted such that an induction-M high-pass filter
53
in a parallel type, a constant-K high-pass filter
54
, an induction-M high-pass filter
55
in a serial type, a shunt trap
56
, and a VHF input tuning circuit
57
are connected in series sequentially between an input terminal
51
and a VHF high-frequency amplifier
52
. Also, a UHF input circuit unit
58
including a UHF input tuning circuit (not shown), etc. is connected to the input terminal
51
.
The induction-M high-pass filter
53
in the parallel type is constituted of a first inductor
59
and a first capacitor
60
connected in parallel each other, and a shunt inductor
61
, the respective one ends of the first inductor
59
and the first capacitor
60
are connected to the input terminal
51
, and the other ends thereof are grounded through the shunt inductor
61
. Further, a cut off frequency of this induction-M high-pass filter
53
in the parallel type is set to approximately 54 MHz, and the parallel resonance frequency by the first inductor
59
and the first capacitor
60
is set to approximately 41 MHz.
Moreover, the constant-K high-pass filter
54
is constituted of a shunt inductor
61
and a series capacitor
62
in which one end thereof is connected to the one end of this shunt inductor
61
, and a cut off frequency thereof is also set to approximately 54 MHz. Accordingly, it leads to the shunt inductor
61
being commonly used by the induction-M high-pass filter
53
in the parallel type and the constant-K high-pass filter
54
.
The induction-M high-pass filter
55
in the serial type is constituted of a series capacitor
62
, a second inductor
63
and a second capacitor
64
, which are connected in serial each other, which are connected between the other end of this series capacitor
62
and the ground, and a cut off frequency thereof is set to approximately 54 MHz, and also a serial resonance frequency of the second inductor
63
and the second capacitor
64
is set to approximately 26 MHz.
Furthermore, the shunt trap
56
is constituted of a third inductor
65
and a third capacitor
66
which are connected in parallel each other, and a parallel resonance frequency by the second inductor
65
and the second capacitor
66
is set to approximately 46 MHz.
Then, by the induction-M high-pass filter
53
in the parallel type, the constant-K high-pass filter
54
, the induction-M high-pass filter
55
in the serial type, and the shunt trap
56
, as shown in
FIG. 5
, passing through a frequency band equal to or more than approximately 54 MHz as well as attenuating sharply with a frequency equal to or less than 54 MHz, in particular, the attenuations in the middle frequency band of a television (approximately 41 MHz to 46 MHz in the U.S. specification), and in the citizen band (26 MHz) to be used in a transceiver are made larger as equal to or more than 55 dB. As a result, it is arranged that an interference signal of in the middle frequency band of the television and an interference signal in the citizen band are not to be inputted into the VHF input tuning circuit
57
, and the VHF high-frequency amplifier
52
, etc.
The VHF input tuning circuit
57
is constituted of four tuning inductors
67
,
68
,
69
,
70
and a varactor diode
71
, and is arranged such that a tuning frequency thereof can be varied by varying a capacitance value of the varactor diode
71
. In this VHF input tuning circuit
57
, the tuning inductors
67
,
68
,
69
and the varactor diode
71
are connected in a pai-shape, and one end of the tuning inductor
67
is grounded with a direct current blocking capacitor
72
, and an anode of the varactor diode
71
is also grounded. A connecting point of the tuning inductor
67
and the tuning inductor
68
is connected to the shunt trap
56
through the direct current blocking capacitor
73
and the coupling inductor
74
being in series, and a connecting point of the tuning inductor
69
and a cathode of the varactor diode
71
is connected to the VHF high-frequency amplifier
52
through the coupling capacitor
75
. Further, it is arranged such that the tuning inductor
70
is connected in parallel to the tuning inductor
67
, through switch diodes
76
,
77
respectively connected to the respective both ends thereof.
Further, the respective anodes of switch diodes
76
,
77
are connected to a high-band switch terminal
79
through a resistor
78
, and the respective cathodes thereof are connected to a low-band switch terminal
81
through a resistor
80
, and moreover, the other terminal (cathode) of the varactor diode
71
is connected to a tuning voltage terminal
83
through a tuning inductor
69
, a resistor
82
.
Then, when receiving the television signals of the high-band, the switch diodes
76
,
77
are set in the conducting state by applying a high-band switch voltage to the high-band switch terminal
79
(at this time a low-band switch voltage is not applied to the low-band switch terminal
81
), and the tuning inductor
67
and the tuning inductor
70
are connected in parallel as high-frequency wise, thereby a tuning frequency of the VHF input tuning circuit
57
is made higher. Further, when receiving the television signals of the low-band, the switch diodes
76
,
77
are set in the non-conducting state by applying a low-band switch voltage to the low-band switch terminal
81
(at this time a high-band switch voltage is not applied to the high-band switch terminal
79
), and the tuning inductor
70
is being separated from the tuning inductor
67
as high-frequency wise, thereby a tuning frequency of the VHF input tuning circuit
57
is made lower. Then, a capacitance value of the varactor diode
71
is varied by a tuning voltage from the tuning voltage terminal
83
, thereby it turns to be a tunable for the frequencies of the television signals of the respective channels in the low-band and the high-band which are allocated to the frequencies equal to or more than 54 MHz.
Further, although they are not shown, but a hybrid circuit, a local oscillator, etc. are connected to a post VHF high-frequency amplifier. Then, the television signals output from the VHF high-frequency amplifier
52
are frequency-converted to a middle frequency in the hybrid circuit.
Such a conventional tuner is incorporated into a car navigation system, for example, when utilizing as for use on a vehicle, but it was not enabling to receive the FM broadcasting. Therefore, it needs to incorporate an extra FM receiver or FM tuner and the like for receiving the FM broadcasting, and thus the car navigation system is turned to be complex, thereby a planning of the miniaturization and the lower price could not be made.
Furthermore, recently, a tuner is mounted on a personal computer, and it is considered that on a display thereof a picture (video) of a television is shown, or characters of a teletext are displayed, but in a conventional tuner the FM broadcasting could not be received, thereby the characters of the teletext in the FM broadcasting could not displayed.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a television signal receiving tuner which is capable of easily receiving the FM broadcasting signals, and also which is adapted to
Furuta Toshiro
Yamamoto Masaki
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Hsia Sherrie
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