Video apparatus having improved antenna transfer switching system
First Claim
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1. Apparatus, comprising:
- a pair of supply lines for connection to a source of A.C. power;
a power switch, subject to switching between open and closed conditions;
power supply means coupled to said supply lines via said power switch for providing a D.C. supply voltage when said power switch is in said closed condition;
RF signal source means responsive to said D.C. supply voltage for providing an RF output signal within a predetermined frequency band;
RF transfer switch means having a first circuit path for coupling said RF output signal to an RF output connector and a second circuit path for coupling an RF input connector to said RF output connector, the first path including a series connected diode means, the second path including a shunt connected diode means; and
control means for applying a forward bias signal to each diode means in each path when said power switch is in said closed condition and for applying a reverse bias signal to each diode means in each path when said power switch is in said open condition.
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Abstract
RF switching diodes in the antenna transfer switch of a video disc player are reverse biased by means of a bias supply when the main power supply of the player is turned off. The reverse bias counteracts any tendency for RF signals applied to the player antenna input connector from forward biasing the diodes which otherwise could result in intermodulation distortion of antenna input signals coupled to the player RF output connector. The effect of the reverse bias is augmented by a high pass filter in the antenna transfer switch which attenuates RF input signals at frequencies below the lowest assigned television channel frequency.
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Citations
12 Claims
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1. Apparatus, comprising:
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a pair of supply lines for connection to a source of A.C. power; a power switch, subject to switching between open and closed conditions; power supply means coupled to said supply lines via said power switch for providing a D.C. supply voltage when said power switch is in said closed condition; RF signal source means responsive to said D.C. supply voltage for providing an RF output signal within a predetermined frequency band; RF transfer switch means having a first circuit path for coupling said RF output signal to an RF output connector and a second circuit path for coupling an RF input connector to said RF output connector, the first path including a series connected diode means, the second path including a shunt connected diode means; and control means for applying a forward bias signal to each diode means in each path when said power switch is in said closed condition and for applying a reverse bias signal to each diode means in each path when said power switch is in said open condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Apparatus as recited in claim l wherein said second circuit path comprises high pass filter means having an input node connected to said RF input connector, an output node connected to said RF output connector and wherein said shunt connected diode means comprises at least one semiconductor diode connected between an intermediate node or the output node of said high pass filter means and a point of reference potential.
Specification