Television – Receiver circuitry – Tuning
Reexamination Certificate
1998-07-30
2001-05-22
Kostak, Victor R. (Department: 2611)
Television
Receiver circuitry
Tuning
C348S552000, C343S720000, C343S822000
Reexamination Certificate
active
06236437
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tuner card for use with a notebook-size personal computer as well as to a tuner incorporated in the tuner card.
2. Description of the Related Art
Recent years have seen the development of a thin-sized television signal receiving unit mounted on a card-type printed-circuit board (called a tuner card) for use with a personal computer Equipped with the tuner card, the personal computer may have television pictures displayed on its display unit.
A conventional tuner card will now be outlined with reference to
FIGS. 7 and 8
. At one end of a rectangular printed-circuit board
41
is formed a connector part
41
a
for connection with a personal computer (not shown). At another end of the printed-circuit board
41
in the opposite direction of the connector part
41
a
is a tuner
42
mounted along the end. The tuner
42
comprises a metal case incorporating a tuner board (not shown) carrying necessary circuitry. On one edge of the metal case is a connector
42
a
. The tuner
42
is mounted on the print-circuit board
41
so that the connector
42
a
is oriented in the opposite direction of the connector part
41
a
. The connector
42
is fed with television signals from an external antenna (not shown).
A region
41
b
between the connector part
41
a
and the tuner
42
on the printed-circuit board
41
comprises electronic parts (not shown) constituting digital circuits. These circuits serve as an interface that allows video and other signals from the tuner
42
to be admitted to the personal computer.
The tuner card is inserted into the personal computer through a slot (not shown) on one side of the PC body, so that the connector part
41
a
is plugged into a connector (not shown) inside the PC. In this state, the region
41
b
carrying the electronic parts making up the digital circuits is located within the slot while the tuner
42
extends laterally outside the PC. The height of the region
41
b
on the printed-circuit board
41
is about 5 mm so that the card fits snugly into the PC slot.
An antenna, not shown, is connected to the connector
42
a
on the side of the tuner
42
. Through the antenna and the connector
42
a
, television signals are input to the tuner
42
.
FIG. 8
is a schematic block diagram of the tuner
42
. As illustrated, an input terminal
51
connected to the connector
42
a
admits television signals on the VHF and UHF bands The television signals are split by a branching circuit
52
into the signals on the VHF band and those on the UHF band The branched signals are input respectively to a VHF tuner unit
53
and a UHF tuner unit
54
wherein the television signal of a desired channel is selected and converted in frequency to an intermediate frequency signal. The intermediate frequency signal is amplified and accorded a selective specificity by an intermediate frequency circuit
55
. From the circuit
55
, the signal is sent to a demodulator
56
which derives video signal V and audio signal A from the received signal.
The tuner
42
has a band switching voltage generating circuit
57
for selecting a reception band to which the selected television signal belongs. A channel selecting signal S either from a television set or from the personal computer is admitted to the band switching voltage generating circuit
57
. There are three kinds of reception bands: the UHF band, the VHF high-band, and the VHF low-band. Where a UHF band television signal is to be received, the band switching voltage generating circuit
57
outputs a UHF band switching voltage UB through its output terminal
57
a
to the UHF tuner unit
54
. Likewise, upon reception of a VHF high-band television signal, the circuit
57
outputs a high-band switching voltage HB through its output terminal
57
b
to the VHF tuner unit
53
; for receiving a VHF low-band television signal, the band switching voltage generating circuit
57
outputs a low-band switching voltage LB through its output terminal
57
c
to the VHF tuner unit
53
.
There are some disadvantages involved in the use of the conventional tuner above constituting a tuner card for use with the notebook-size personal computer. The notebook computer is originally intended for portable and mobile use free from constraints specific to the location. If an antenna is available at the site of use or if an antenna cable connected to an exterior antenna is led into the site, that antenna or antenna cable may be connected to the connector
42
a
of the tuner
42
. In many cases, however, neither antenna nor antenna cable is available where the notebook computer is desired to be operated. This poses limits to where the notebook computer may be used if television signals need to be admitted to the computer.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a tuner card and a television signal receiving tuner incorporated in the tuner card for use with a notebook-size personal computer, the tuner card and the tuner being arranged to receive television signals free from constraints specific to the site of PC use.
In carrying out the invention and according to one aspect thereof, there is provided a television signal receiving tuner comprising: an input terminal for admitting VHF and UHF band television signals; a correcting circuit connected to the input terminal and having inductors to correct an effective length of an antenna; a branching filter for branching the signals from the correcting circuit into VHF band television signals and UHF band television signals to be output separately; a VHF tuner unit for receiving the VHF television signals from the branching filter; and a UHF tuner unit for receiving the UHF television signals from the branching filter; wherein values of the inductors are made variable.
In a preferred structure according to the invention, the inductors of the correcting circuit in the television signal receiving tuner may be switched progressively from small to large inductance values from the time of UHF band reception wherein the UHF band television signals are received, to the time of VHF high-band reception wherein high-frequency VHF television signals are received, to the time of VHF low-band reception wherein low-frequency VHF band television signals are received.
In another preferred structure according to the invention, the television signal receiving tuner may further comprise a band switching voltage generating circuit for generating a band switching voltage from different terminals depending on the reception band. With this structure, the correcting circuit may include: a first and a second inductors connected in series; a first switching diode connected parallel to the serial connection of the first and the second inductors; and a second switching diode connected parallel to the second inductor. At the time of UHF band reception, the band switching voltage is supplied to the first switching diode to turn on the diode; at the time of VHF high-band reception, the band switching voltage is supplied to the second switching diode to turn on the diode.
In a further preferred structure according to the invention, a television signal receiving unit for use with a personal computer may comprise a rectangular printed-circuit board having a connector unit formed on one end thereof, the connector unit being inserted into a slot of a body of the personal computer so as to be coupled with a connector within the body, the rectangular printed-circuit board further comprising the television signal receiving tuner.
In an even further preferred structure according to the invention, the inductors of the correcting circuit in the television signal receiving unit for use with a personal computer may be switched progressively from small to large inductance values from the time of UHF band reception wherein the UHF television signals are received, to the time of VHF high-band reception wherein high-frequency VHF television signals are received, to the time of VHF low-band reception wherein low-frequency VHF ba
Furuta Toshiro
Osada Shigeru
Suzuki Takeo
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kostak Victor R.
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