Receiving apparatus shared by multiple tuners

Telecommunications – Wireless distribution system – Receiver for satellite broadcast

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

C455S255000, C455S133000

Reexamination Certificate

active

06728513

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to receiving apparatuses and particularly to a receiving apparatus shared by a plurality of tuners.
2. Description of the Background Art
FIG. 5
is a block diagram showing a structure of a receiving unit of a conventional satellite broadcasting system. Referring to
FIG. 5
, the receiving unit of the satellite broadcasting system includes an antenna
30
having a reflector
31
and an LNB (Low Noise Block down converter)
32
, a receiver
33
having a DBS (Direct Broadcasting by Satellite) tuner
34
, an FM demodulator
35
, a video+audio circuit
36
and an amplifier
37
, and a television receiver
38
.
Radio waves &agr; emitted from a satellite are supplied via reflector
31
to LNB
32
. LNB
32
extracts from the received radio waves a image signals of a plurality of channels, amplifies the signals with noise kept low, and supplies an image signal of a channel selected by DBS tuner
34
to DBS tuner
34
. An output signal of LNB
32
is supplied via DBS tuner
34
to FM demodulator
35
which FM-demodulates the output signal.
The FM-demodulated image signal is converted to a video signal and an audio signal by video+audio circuit
36
, amplified by amplifier
37
and then supplied to television receiver
38
. An image of the channel selected by DBS tuner
34
is displayed on the screen of television receiver
38
.
FIG. 6
is a perspective view showing from the outside a structure of LNB
32
. Referring to
FIG. 6
, LNB
32
has a casing member
41
, and a feed phone
42
and a signal input/output terminal
43
are provided on the surface of casing member
41
. Radio waves &agr; reflected from reflector
31
of antenna
30
are supplied into an opening
42
a
of feed phone
42
. In casing
41
, a signal processing circuit is provided for processing the radio waves &agr; supplied to feed phone
42
. Signal input/output terminal
43
is connected to DBS tuner
34
via a cable.
FIG. 7
is a circuit block diagram showing a structure of the signal processing circuit of LNB
32
. Referring to
FIG. 7
, the signal processing circuit includes LNAs (Low Noise Amplifiers)
44
a
and
44
b
, bandpass filters (BPFs)
45
a
-
45
d
, local oscillators
46
a
and
46
b
, mixers
47
a
-
47
d
, a selector
48
, an IF amplifier
49
, a low-pass filter (LPF)
50
and a regulator
51
.
A horizontally polarized wave signal &phgr;h and a vertically polarized wave signal &phgr;v received by feed phone
42
are respectively amplified by LNAs
44
a
and
44
b
with noise kept low. An output signal of LNA
44
a
is supplied to bandpass filters
45
a
and
45
c
and an output signal of LNA
44
b
is supplied to bandpass filters
45
b
and
45
d.
Signals &phgr;h and &phgr;v have a frequency band of 10.7-12.75 GHz. Bandpass filters
45
a
and
45
b
pass only the frequency components in the range of 10.7 to 11.7 GHz of respective signals &phgr;h and &phgr;v. Bandpass filters
45
c
and
45
d
pass only the frequency components in the range of 11.7 to 12.75 GHz of respective signals &phgr;h and &phgr;v. Respective signals &phgr;h
1
, &phgr;v
1
, &phgr;h
2
and &phgr;v
2
passed through bandpass filters
45
a
-
45
d
are supplied respectively to mixers
47
a
-
47
d.
Local oscillator
46
a
generates a high-frequency signal of 9.75 GHz and supplies it to mixers
47
a
and
47
b
. Local oscillator
46
b
generates a high-frequency signal of 10.6 GHz and supplies it to mixers
47
c
and
47
d
. Signals &phgr;h
1
and &phgr;v
1
are converted respectively by mixers
47
a
and
47
b
into respective IF signals &phgr;
1
and &phgr;
2
of 950-1950 MHz. Signals &phgr;h
2
and &phgr;v
2
are converted respectively by mixers
47
c
and
47
d
into respective IF signals &phgr;
3
and &phgr;
4
of 1000-2150 MHz.
Selector
48
selects any of four IF signals &phgr;
1
-&phgr;
4
according to a DC voltage V
1
and a clock signal CLK supplied from DBS tuner
34
via input/output terminal
43
and low-pass filter
50
and supplies the selected IF signal to DBS tuner
34
via IF amplifier
49
and input/output terminal
43
. The DC voltage V
1
is 18 V or 13 V. The clock signal CLK has a frequency of 22 KHz and an amplitude of 0.6 V. Low-pass filter
50
allows DC voltage V
1
and clock signal CLK to pass while it does not pass IF signals &phgr;
1
-&phgr;
4
.
If DC voltage V is 18 V, signals &phgr;
1
and &phgr;
3
are selected. If DC voltage V
1
is 13 V, signals &phgr;
2
and &phgr;
4
are selected. If no clock signal CLK is input, signals &phgr;
1
and &phgr;
2
are selected and signals &phgr;
3
and &phgr;
4
are selected if clock signal CLK is input. Accordingly, signal &phgr;
1
is selected if DC voltage V
1
is 18 V and no clock signal CLK is input, signal &phgr;
2
is selected if DC voltage V
1
is 13 V and no clock signal CLK is input, signal &phgr;
3
is selected if DC voltage V
1
is 18 V and clock signal CLK is input, and signal &phgr;
4
is selected if DC voltage V
1
is 13 V and clock signal CLK is input.
DC voltage V
1
is also used as the supply voltage of regulator
51
. Regulator
51
uses DC voltage V
1
as the supply voltage to generate a DC constant voltage V
2
of 9 V and a DC constant voltage V
3
of 5 V. DC constant voltage V
2
of 9 V generated by regulator
51
is applied to IF amplifier
49
as its supply voltage, and DC constant voltage V
3
of 5 V generated by regulator
51
is applied to LNAs
44
a
and
44
b
and local oscillators
46
a
and
46
b
as their supply voltage.
In recent years, there arises a need to share one LNB by a plurality of DBS tuners
34
. For example, referring to
FIG. 8
, an LNB
55
shared by two DBS tuners
34
is provided with one feed phone
57
and two signal input/output terminals
58
a
and
58
b
on a casing member
56
.
Regarding such an LNB
55
, there is a problem that how supply voltages V
2
and V
3
for the LNA, local oscillator and IF amplifier should be generated. For example, according to the following description in conjunction with
FIG. 9
, two signal input/output terminals
58
a
and
58
b
are connected to a power supply node
61
a
of a regulator
61
via respective low-pass filters
59
a
and
59
b
and respective diodes
60
a
and
60
b
. Diodes
60
a
and
60
b
are provided for preventing, when one of the two signal input/output terminals
58
a
and
58
b
is supplied with 18 V and the other thereof is supplied with 13 V, current flow from one signal input/output terminal to the other signal input/output terminal to cause malfunction or breakdown of DBS tuners
34
.
In this case, supposing that consumption current of LNB
55
is 200 mA, if DC voltages applied respectively to two signal input/output terminals
58
a
and
58
b
are the same (18 V or 13 V), currents of the same value (100 mA) flow through respective two signal input/output terminals
58
a
and
58
b
. However, if 18 V and 13 V are supplied respectively to signal input/output terminals
58
a
and
58
b
, current of 200 mA flows through signal input/output terminal
58
a
and no current flows through signal input/output terminal
58
b
. On the contrary, if signal input/output terminals
58
a
and
58
b
are supplied with 13 V and 18 V respectively, current of 200 mA flows through signal input/output terminal
58
b
and no current flows through signal input/output terminal
58
a
. For this reason, each time a channel is switched, current flowing from two DBS tuners
34
to LNB
55
greatly varies, generating noise. This noise causes a selector to malfunction, resulting in selection of a channel different from a desired channel or disorder of an image on a television receiver
38
.
SUMMARY OF THE INVENTION
One object of the present invention is accordingly to provide a receiving apparatus which can be shared by a plurality of tuners while noise is reduced.
According to the present invention, a receiving apparatus includes a plurality of signal input/output terminals connected respectively to a plurality of tuners, an extraction/amplification circuit extracting/amplifying a plurality of i

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Receiving apparatus shared by multiple tuners does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Receiving apparatus shared by multiple tuners, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Receiving apparatus shared by multiple tuners will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-3204190

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.