Abstract: A feedback circuit for restoration of DC reference levels in video signals is presented. In one or more embodiments, a DC sample pulse is generated representing the back porch of an incoming video signal. A sample and hold circuit, which is controlled by the DC sample pulse, obtains the correct offset voltage in the output signal during this back porch period. The offset voltage feeds back through an integrating node in front of the circuit causing an amplifier to compensate for the signal offset thereby restoring the video signal to its proper DC voltage level with respect to ground.

Abstract: A closed loop feedback system is employed in a receiver to automatically compensate the communication signal from twisted pair cables for AC and DC losses. This is accomplished through the use of a reference pulse signal which is sent along with other digital information. At the receiver, the reference pulse signal is restored to its proper level through a Pulse Width Modulation (PWM)-controlled variable compensation amplifier circuit. The received reference signal is compared to a known reference value and the duty cycle of the PWM circuit is adjusted until the proper level reference signal is achieved. Thereafter, the digital signal is extracted. OFDM (Orthogonal Frequency Division Multiplexing) with pilot tones are used to maximize payload while minimizing crosstalk effects. The pilot tones locate the OFDM symbols in time while supplying compensation information concerning the transmission medium.

Abstract: A system capable of transmitting and receiving high frequency video signals across various lengths of a twisted pair cable while maintaining video quality is presented. The system includes a transmitter and a receiver tandem coupled together over twisted pair cable. Each video component is mixed with a reference signal in the transmitter and driven differentially onto the twisted pair cable. Upon detection of a signal in the twisted pair cable, the receiver adjusts its internal gains until the known characteristic of the reference signal is achieved. The receiver than automatically adjusts the skew & DC offset. Thus, the receiver is able to automatically measure the degradation in video quality and appropriately compensate the video signals for the accumulated degradation caused primarily by the transmission between the transmitter and the receiver. The compensated video may subsequently be provided to a video display device.

Abstract: A apparatus and apparatus for compensating for video insertion loss due to transmission over long twisted pair cable lines is presented. Transmission of video over twisted pair cable is advantageous because of its superior cost advantage over coaxial cable. However, twisted pair cables have significant loss characteristics at the higher frequencies (i.e., broadband) compared to coaxial cables. At a transmitter station, the video signal is amplified in the high frequency region for possible skin effect losses thereby brute forcing the high frequency components to the receiving station. At the receiver station, the video signal is further compensated for diffusion line and skin effect losses. The total skin effect compensation applied in both the transmitter and receiver stations is such that the square root of frequency characteristics of skin effect losses is compensated for.

Abstract: A apparatus and apparatus for compensating for video insertion loss due to transmission over long twisted pair cable lines is presented. Transmission of video over twisted pair cable is advantageous because of its superior cost advantage over coaxial cable. However, twisted pair cables have significant loss characteristics at the higher frequencies (i.e., broadband) compared to coaxial cables. At a transmitter station, the video signal is amplified in the high frequency region for possible skin effect losses thereby brute forcing the high frequency components to the receiving station. At the receiver station, the video signal is further compensated for diffusion line and skin effect losses. The total skin effect compensation applied in both the transmitter and receiver stations is such that the square root of frequency characteristics of skin effect losses is compensated for.