Zenith Electronics Corporation

Zenith Radio Corporation

Gary A Jones

Thomas J Zato

Gary J Sgrignoli

Peter C Skerlos

Gopalan Krishnamurthy

Raymond C Hauge

Paul A Snopko

Philip J Nowaczyk

Donald Ankeny

Raymond M Rees

Minglu Zhang

A translator demodulates a received digital television signal so as to produce a digital data stream, a symbol clock, and a byte clock, wherein the symbol clock and the byte clock are corrupted by phase noise. The digital data stream is written into a buffer in response to the corrupted byte clock. The corrupted symbol clock is applied to a frequency/phase locked loop having a narrowband loop filter. The frequency/phase locked loop produces a regenerated symbol clock having substantially no phase noise. The digital data stream is read from the buffer in response to the regenerated symbol clock. The digital data stream read from the buffer and the regenerated symbol clock are applied to a modulator for re-broadcasting of the received digital television signal.

VSB modulator symbol clock processing to reduce jitter/phase noise and sampling artifacts

A reference generator includes a memory that stores reference data which, when clocked out of the memory, produces an ATSC compliant VSB reference signal substantially free of sub-harmonics of the clock signal. A digital-to-analog converter converts the clocked out reference data to an analog signal. The analog signal may be at low IF. An up converter is arranged to upconvert the output of the digital-to-analog converter to an RF reference signal. The RF reference signal can be used, for example, to calibrate a VSB demodulator.

Reference generator for demodulator calibration

A video decoder includes an application specific integrated circuit (ASIC) that has the decoder address and a secure decryption key stored in a one-time-programmable memory. Encrypted messages are received and selectively supplied to a packet decrypter and to a video decrypter based upon the location of bits in the message string. The packet decrypter is responsive to a flag in the packet data for utilizing a secure key or a unsecure key for decryption of the packet data. The information derived from the secure decryption and the secure key itself are never available (or ascertainable) outside of the ASIC. Only information concerning the unsecure key is available outside of the integrated circuit.

Secure video decoder system

A microprocessor based infrared (IR) decoding system operating with binary data including data bits preceded by synchronizing bits has an input flip flop for triggering a counter responsive to a synchronizing bit and activating a latch type flip flop a predetermined time later for interrogating the data and storing the data bit. The counter also operates another flip flop which signals the microprocessor that a data bit is in the latch. The microprocessor is thus able to process the data in the latch in a time interval ending just before occurrence of the next data bit. The counter triggers the input flip flop to reset and rearm the counter before the next synchronizing bit.

IR decoder system

A digital TV system includes a CCU that is interconnected by a three-wire, high speed bus to a plurality of TV signal function modules for controlling operation thereof by means of a high speed hardware generated clock signal. A software generated clock signal in the CCU is supplied on a low speed two-wire auxiliary device bus which is connected to microprocessors in a plurality of auxiliary devices for performing functions ancillary to TV signal processing. The microprocessor in each auxiliary device is an off-the-shelf type that does not require any special hardware because the timing on the auxiliary device bus is sufficiently slow to enable software monitoring of the line and data transfer.

Digital TV with low cost auxiliary device communication system

A microprocessor based TV/TTX processor includes a stored pages ROM in the TTX processor for storing on-screen display messages and lists of functions and characteristics as pages of TTX data. An RGB switch is coupled to receive the output of a character generator in the TTX processor and to receive the video output of the TV for selectively displaying information from each source with or without the on-screen messages and lists. The stored pages ROM relieves the microprocessor of the necessity of generating the on-screen messages and lists. Items on the list are controllable by the viewer and an indication of the status of the item is given by the microprocessor changing a character in the display memory of the TTX processor.

Television receiver having teletext processor with ROM for on-screen

A system is described for synchronizing the display of characters within a character image area on a raster scanned cathode ray tube. The system's input is a composite blanking signal which includes conventional horizontal rate and vertical rate blanking pulses. In response to the composite blanking signal, the system generates a reset signal when the tube's scan reaches a reference position such as at the top of display. The reset signal and the composite blanking signal are used to develop a control signal when the composite blank signal indicates that the tube's scan has reached the character image area. Other circuitry responds to the control signal and the composite blanking signal for addressing a conventional character display circuit. The latter circuit is thus synchronized to output, to the cathode ray tube, data which is imaged within the character image area.

Synchronizing system for character display

A system is described for interfacing a SWIF with a tuner and an amplifier in the IF section of a television receiver. In the preferred arrangement, the tuner is coupled to the input of the SWIF so as to efficiently transfer signal power to the SWIF over the frequency range of the tuner's output. The output of the SWIF is coupled to an amplifier which has a low, untuned input impedance to establish a mismatch between the SWIF and the amplifier to therey reduce triple-transit effects associated with the SWIF. Preferably, the amplifier is a common-base amplifier whose input impedance is defined by a real impedance component which is substantially smaller in magnitude than its reactive impedance component. Hence, the real component of the amplifier's input impedance is dominant and the effects of stray capacitance between the SWIF and the amplifier are reduced.

Interface system for surface wave integratable filter

A television receiver signal translating system includes a tuner frequency-converting a received broadcast signal to an intermediate frequency signal. An acoustic surface wave filter and gain controlled amplifier are coupled to the tuner and drive a synchronous detecting system. An automatic gain control (AGC) maintains the output of recovered signal constant while a variable bandwidth stage changes the system frequency response as a function of signal strength. A variable influence sound carrier trap responds to the AGC providing increased sound carrier attenuation when strong signals are received and reduced attenuation during weak signal reception.

Growing community of inventors

Arlington Heights, IL, United States of America

Gary A Jones