Television – Television transmitter circuitry
Reexamination Certificate
1998-09-10
2002-10-15
Miller, John (Department: 2614)
Television
Television transmitter circuitry
C348S705000, C333S101000, C333S117000, C455S101000, C455S103000, C455S428000, C455S451000, C455S107000
Reexamination Certificate
active
06466276
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an output distributing/synthesizing apparatus in a current/spare operation scheme or parallel operation scheme using TV (Television) and FM (Frequency Modulation) broadcasting units and the like.
FIGS. 4A and 4B
show the schematic arrangements of conventional output switching apparatuses. The output switching apparatus shown in
FIG. 4A
is disclosed in Japanese Patent Laid-Open No. 57-197901. This apparatus is constituted by 4-terminal hybrid circuits
21
and
22
and variable phase shifters
41
and
42
connected between the output terminals of the 4-terminal hybrid circuit
21
and the input terminals of the 4-terminal hybrid circuit
22
. The output switching apparatus having this arrangement switches outputs from first and second broadcasting units
26
and
28
to an antenna
27
and a pseudo-antenna
29
without interruption. Reference numeral
43
denotes a quarter-wavelength line for a phase shift of 90°.
FIG. 4B
shows an output switching circuit for switching output signals from first and second broadcasting units
26
and
28
to antennas
27
a
and
27
b
without interruption. This circuit differs from that shown in
FIG. 4A
in that 4-terminal switches
71
to
74
are arranged in twos between the first and second broadcasting units
26
and
28
and a 4-terminal hybrid circuit
21
and between a 4-terminal hybrid circuit
22
and the antennas
27
a
and
27
b
, and the pseudo-antenna is replaced with the antenna.
The first problem posed by the output switching apparatus having the arrangement is that while a program is put on the air in the first broadcasting unit
26
, the second broadcasting unit
28
cannot perform maintenance using a test signal and the pseudo-antenna
29
.
The reason for this is that since the degree of isolation between the first and second broadcasting units
26
and
28
is only about −40 dB at the antenna output terminal, the test signal from the second broadcasting unit
28
may be superimposed on the signal from the first broadcasting unit
26
while the program is on the air.
The second problem is that in the 2-line feeding system using two antennas, the plurality of 4-terminal switches
71
to
74
are required to independently switch output signals from the first and second broadcasting units
26
and
28
to the antennas
27
a
and
27
b
, as shown in FIG.
4
B.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a distributing/synthesizing apparatus which can attain a reduction in size of a broadcasting system for current/spare operation and parallel operation, a simplification of the circuit arrangement, and an improvement in maintainability.
In order to achieve the above object, according to the present invention, there is provided a signal distributing/synthesizing apparatus comprising signal distributing/synthesizing means for distributing a signal input to a first terminal to second and third terminals, and synthesizing signals input to the second and third terminals into a signal to be output to the first terminal, first and second antennas forming a radio transmission channel for an output signal from the signal distributing/synthesizing means, a pseudo-antenna forming a pseudo-radio transmission channel for an output signal from the signal distributing/synthesizing means, and first, second, and third switching means, wherein the first switching means complementarily switches/connects a first broadcasting unit and the second antenna to the first terminal of the signal distributing/synthesizing means and the third switching means, the second switching means complementarily switches/connects a second broadcasting unit and the second antenna to the second terminal of the signal distributing/synthesizing means and the third switching means, and the third switching means complementarily switches/connects the pseudo-antenna and the third terminal of the signal distributing/synthesizing means to the first and second switching means.
REFERENCES:
patent: 3800222 (1974-03-01), Kowalewski
patent: 4016503 (1977-04-01), Rambo
patent: 4723307 (1988-02-01), Clark et al.
patent: 4748423 (1988-05-01), Jinich
patent: 5023575 (1991-06-01), Stojan
patent: 5128627 (1992-07-01), Wendt
patent: 5146190 (1992-09-01), Firmain
patent: 5203018 (1993-04-01), Hiroso
patent: 5258995 (1993-11-01), Su et al.
patent: 5594394 (1997-01-01), Sasaki et al.
patent: 5625894 (1997-04-01), Jou
patent: 5822684 (1998-10-01), Kitakubo
patent: 3713086 (1987-04-01), None
patent: 0622911 (1994-04-01), None
patent: 57-135528 (1982-08-01), None
patent: 57-159140 (1982-10-01), None
patent: 57-197901 (1982-12-01), None
patent: 60-30642 (1985-03-01), None
patent: 63-31601 (1988-03-01), None
patent: 63-316940 (1988-12-01), None
patent: 1-280901 (1989-11-01), None
patent: 4-29201 (1992-03-01), None
patent: 5-18132 (1993-03-01), None
patent: 6-177781 (1994-06-01), None
patent: 9-36781 (1997-02-01), None
Miller John
Natnael Paulos M.
Sughrue & Mion, PLLC
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