Chroma inverter

Claim 2

A chroma inverter for selectively inverting the phase of the chroma component of a composite color television signal relative to the luminance and synchronizing pulse components thereof in response to a command signal comprising, separation means coupled in receiving relation to said composite color television signal for extracting the chroma component therefrom and transmitting the remaining luminance and synchronizing pulse components through a first channel while transmitting said chroma component through a second channel, adder means coupled to said first and second channels for recombining the luminance and synchronizing pulse components and chroma component respectively transmitted through said channels to form a composite color television output signal, and controlled phase inverter means coupled within said second channel and having a first condition in which said chroma component is transmitted therethrough with a 180* phase shift and a second condition in which said chroma component is transmitted therethrough with zero phase shift, said inverter means adapted to receive said command signal and to be selectively disposed in one of said conditions in response thereto.

Claim 3

A chroma inverter according to claim 1, further defined by said separation means comprising, a low-pass filter in said first channel and a band-pass filter in said second channel coupled in receiving relation to said composite color television signal, said low-pass filter having a cutoff frequency below that of the lower side band of said chroma component, said band-pass filter having a center frequency equal that of the color subcarrier of said chroma component and cutoff frequencies symmetrically encompassing the side bands thereof.

Claim 4

A chroma inverter according to claim 2, further comprising delay equalizer means in one of said channels providing equal time delays for signals therein and said band-pass filter having a phase versus frequency characteristic wherein zero phase occurs precisely at the frequency of said color subcarrier.

Claim 5

A chroma inverter according to claim 3, further defined by said delay means being connected in said first channel for compensating differences between the time delays of said low-pass and band-pass filters.

Claim 6

A chroma inverter according to claim 1, further defined by said phase inverter means comprising input and output transformers each having a primary and a secondary winding, said primary winding of said input transformer coupled to said separation means to receive said chroma component, said secondary winding of said output transformer coupled to said adder means, a switching network coupling said secondary winding of said input transformer to said primary winding of said output transformer, said network having first and second selectively conductive or nonconductive paths respectively coupling corresponding ends of the secondary winding of said input transformer and primary winding of said output transformer and cross coupling opposed ends of the secondary winding of said input transformer and primary winding of said output transformer, and actuating means responsive to said command signal and coupled to said paths for selectively rendering either said first paths conductive and said second paths nonconductive or said first paths nonconductive and said second paths conductive.

Claim 7

A chroma inverter according to claim 5, further defined by said separation means including a low-pass filter in said first channel and a band-pass filter in said second channel commonly coupled in receiving relation to said composite color televisIon signal, said band-pass filter having its output coupled to said input transformer, said low-pass filter having a cutoff frequency below that of the lower side band of said chroma component, said band-pass filter having a center frequency equal to that of the color subcarrier of said chroma component and cutoff frequencies symmetrically encompassing the side bands thereof.

Claim 8

A chroma inverter according to claim 6, further defined by said first and second channels having equal time delays and said band-pass filter having a phase versus frequency characteristic wherein zero phase occurs precisely at the frequency of said color subcarrier.

Claim 9

A chroma inverter according to claim 7, further defined by said first channel having channel delay equalizer means for compensating differences between the time delays of said low-pass and band-pass filters.

Claim 10

A chroma inverter according to claim 5, said network further defined by said first paths having a first pair of diodes respectively coupled between the corresponding ends of said secondary winding of said input transformer and said primary winding of said input transformer and said primary winding of said output transformer, said second paths having a second pair of diodes respectively cross coupled between opposed ends of said secondary winding of said input transformer and primary winding of said output transformer, said second pair of diodes having polarity senses reversed with respect to said first pair of diodes, and said actuating means comprising a bipolar bias circuit coupled to a center tap of said primary winding of said output transformer for applying opposite polarity biases thereto respectively in response to an absence and presence of said command signal, said secondary winding of said output transformer having a center tap connected to ground.

Claim 11

A chroma inverter according to claim 9, further defined by said separation means including a low-pass filter in said first channel having an output coupled to said adder means, a buffer amplifier in said first channel for coupling said composite signal to said low-pass filter, and a band-pass filter in said second channel coupled in receiving relation to said composite signal and having an output coupled to the primary winding of said input transformer, said low-pass filter having a cutoff frequency below that of the lower side band of said chroma component, said band-pass filter having a center frequency equal to that of the color subcarrier of said chroma component and cutoff frequencies symmetrically encompassing the side bands thereof.

Claim 12

A chroma inverter according to claim 10, further defined by said first and second channels having equal time delays, and said band-pass filter having a phase versus frequency characteristic with bipolar inverse symmetry and zero phase occurring precisely at the frequency of said color subcarrier.

Claim 13

A chroma inverter according to claim 9, further defined by said bipolar bias circuit including a first transistor having base, emitter, and collector, said base coupled in receiving relation to said command signal, means coupled to said emitter and collector to bias said transistor to be normally nonconducting in the absence of said command signal and conducting in the presence thereof, a second transistor having base, emitter, and collector, said second transistor being of an opposite conductivity type with respect to said first transistor, said base of said second transistor coupled to said collector of said first transistor, first and second opposite polarity bias sources, means including a load resistor respectively coupling said first and second bias sources to said emitter and collector of said second transistor to normally bias same to be nonconductive in response to nonconduction of said first transistor and to be conductive in response to conduction of said first transistor, said second transistor thereby developing opposite polarity biases across said load resistor respectively in response to nonconduction and condUction of said second transistor, and means coupling said load resistor to said center tap of said primary winding of said output transformer to apply said opposite polarity biases thereto.

Claim 14

A chroma inverter according to claim 12, further defined by said separation means including a low-pass filter in said first channel, said low-pass filter having an output coupled to said adder means, a buffer amplifier in said first channel for coupling said composite signal to said low-pass filter, and a band-pass filter in said second channel coupled in receiving relation to said composite signal and having an output coupled to the primary winding of said input transformer, said low-pass filter having a cutoff frequency below that of the lower side band of said chroma component, said band-pass filter having a center frequency equal that of the color subcarrier of said chroma component and cutoff frequencies symmetrically encompassing the side bands thereof.

Claim 15

A chroma inverter according to claim 13, further defined by said first and second channels having equal time delays, and said band-pass filter having a phase versus frequency characteristic with bipolar inverse symmetry and zero phase occurring at the frequency of said color subcarrier.