General Instrument Corporation

Videotek, Inc.

Donald E Groff

Marlin F McGregor, Jr

Edgar Rhodes

Robert E Stenzel

Marlin F Mcgregor

An upconverter for converting IF television signals to VHF or UHF signals prior to broadcast is configured to process either analog or digital television signals. The upconverter identifies the type of incoming television signal and generates an appropriate reference signal depending on whether the incoming television signal is digital or analog. In an analog format, the reference signal is used by the modulator generating the IF signal to synchronize phase with the signals output by various other upconverters. In a digital format, the reference signal is used, for example, as a test signal for the upconversion circuit.

Upconverter for a television signal headend distribution center handling analog and digital signals and method of making and using the same

An improved electronic device, for example, an upconverter for converting an IF television signal to a VHF or UHF television signal at a broadcast signal headend provides an external, shielded bus interface which connects to filtered internal input and output lines leading to control circuitry. The resulting device suppresses unwanted electromagnetic emissions.

Method and apparatus for suppressing electromagnetic emissions from a bus interface with electronic equipment

An upconverter unit for a cable television system upconverts multiple channel signals from a common intermediate frequency to a VHF or UHF signal ready for transmission to subscribers. The two-stage upconverter provides a first stage in which different channel signals are upconverted to different frequencies which are spaced apart by same frequency difference characteristic of different channels in the cable system. A second stage of the upconverter uses a common oscillator signal to convert the various channel signals from the first stage to the frequencies at which they will be transmitted over the cable system.

Multiple channel upconverter having adjacent channel output and method of implementing the same

The proposed phase lock technique uses various feedback loops to lock the frequency and phase of a CATV modulator output signal to that of an off-air signal without directly measuring the output frequency. One embodiment includes a tuner for receiving the off-air signal and generating an intermediate frequency signal and a phase-frequency detector for comparing the frequency and phase of the intermediate frequency signal generated by the tuner with the frequency and phase of an intermediate frequency signal generated by the modulator based on a reference input signal. The output of the phase-frequency detector is used to control the reference input signal into the modulator and the reference input signal to the tuner such that the frequency and phase of the modulator output signal is locked to the frequency and phase of the received off-air signal. A second embodiment uses two tuners with a common reference frequency and a third embodiment eliminates the need for a tuner, using direct counting of the broadcast signal to derive the modulator reference signal.

Off-air phase lock technique

A digital converter controllably modifies input video data representing pixel luminance and color information, in two color space formats. Two color space converters are coupled in cascade. Serial video data is converted to parallel and demultiplexed. A first color space converter converts 4:2:2 sampled YCbCr luminance and color difference input data to RGB red/green/blue format. A second color space converter changes the data back to YCbCr before remultiplexing at the output. Under operator control from front panel inputs, a controller varies the conversion coefficients at the input-side color space converter, including by trigonometric functions applied to the coefficients to provide controllable hue phase shifting, modifies the transfer function in RGB color space by adjusting data in the lookup tables, and applies maximum/minimum clipping levels. Interpolation doubles the sample rate of CbCr color difference data at the input for co-siting each Y sample with a CbCr color difference for processing samples at 4:4:4. Two's complement computations, including for luminance Y, employ the full dynamic quantization range of the color space converters. An auxiliary color space converter operates on divided coefficients for detecting overflow. A bypass delay route is provided for non-video data, and error detection and handling signals are passed through as well as compared and generated for the changed data.

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Hatfield, PA, United States of America

Donald E Groff