Intelligent teletext decoder

• US 4,449,145 A
• Filed: 06/13/1983
• Issued: 05/15/1984
• Est. Priority Date: 01/24/1980
• Status: Expired due to Term

• Current Assignee: Zenith Radio Corporation (LG Corporation)
• Original Assignee: Zenith Radio Corporation (LG Corporation)
• Inventors: Ciciora, Walter S.
• Primary Examiner(s): Chin, Tommy P.
• Application Number:
  US06/493,129
• Time in Patent Office: 337 Days
• Field of Search: 358/147, 358/160, 358/167, 358/905, 375/13, 375/14, 375/101, 364/724, 364/825, 333/18, 455/65
• US Class Current: 348/466
• CPC Class Codes: H04N 7/035 Circuits for the digital non-picture data signal, e.g. for slicing of the data signal, for regeneration of the data-clock signal, for error detection or correction of the data signal

Abstract

An equalizer and decoder system compensating for multipath distortion in digital format signals sent by teletext, for example. The system loads demodulated data signals and a received reference signal into a charge coupled device clocked in real time by a clock circuit. Later, the reference pulse is clocked to a microprocessor which determines tap coefficients for a transversal filter to correct the multipath distortion in the reference signal. The data signals are then applied to a transversal filter weighted with the calculated tap weights. After filtering, signals are decoded by the microprocessor.

In another embodiment a charge coupled device with tapped stages is used at one time for receiving the data signals in real time, and at a later time for part of a transversal filter.

In a simplest embodiment, distortions are removed by the microprocessor itself, without any separate transversal filter.

Claims

1. A machine implemented method for use with a receiver which receives both transmitted digital format data signals and a transmitted reference signal, for equalizing said digital format data signals according to distortion exhibited by said reference signal and decoding said digital format data signals, comprising the steps of:

loading said reference signal into a time base expander having an input and an output in real time;

then

applying the reference signal from the output of said time base expander at a selectable rate to another circuit and therein automatically and electronically calculating adjustment signals based on said reference signal for correcting said reference signal;

adjusting a filter having tap weights in accordance with an adjustment signal to obtain weighted taps;

loading said digital format data signals into said filter;

equalizing said digital format data signals in said filter, including generating weighted signals in accordance with the weighted taps and said digital format data signals in said filter thereby to obtain an equalized data signal; and

then

decoding said equalized data signal.

2. The method according to claim 1 wherein said time base expander comprises a charge coupled device.

3. The method according to claim 1 wherein said another circuit includes a microprocessor.

4. The method according to claim 1 wherein said filter comprises a charge coupled device transversal filter having a plurality of stages and corresponding taps coupled to be weighted in accordance with said adjustment signals, and wherein said equalizing step includes generating signals weighted in accordance with said taps and the data in said stages and summing the weighted signals.

5. A machine implemented method for use with a receiver which receives both transmitted digital format data signals and a transmitted reference signal, for equalizing said digital format data signals according to distortion exhibited by said reference signal and decodng said digital format data signals, comprising the steps of:

loading said reference signal in real time into tapped timed base expander having an input and an output;

applying said reference signal from said output of said time base expander at a selectable rate to another circuit and therein automatically and electronically calculating adjustment signals based on said reference signal for correcting said reference signal;

storing said adjustment signals;

loading said digital format data signals into said tapped time base expander in real time;

equalizing said digital format data signals in the tapped time base expander, including generating weighted signals in accordance with said stored adjustment signals and said digital format data in said tapped time base expander thereby to obtain an equalized data signal; and

then

decoding said equalized data signal.

6. The method according to claim 5 wherein said storing step includes storing said adjustment signals in a tap weight storage.

7. The method according to claim 6 wherein said equalizing step includes applying signals from said tapped time base expander to weighting circuits adjusted in accordance with said adjustment signals stored in said tap weight storage, and summing the output of said tap weighting circuits.

8. The method according to claim 5 wherein said reference signal and said digital format data signals are loaded into a tapped time base expander in real time, and wherein said applying said reference signal step includes clocking said reference signal to said tapped time base expander to said another circuit at a selected rate slower than the real time rate.

9. A machine implemented method for use with a receiver which receives both transmitted digital format data signals and a transmitted reference signal for equalizing said digital format data signals according to distortion exhibited by said reference signals and decoding said digital format data signals, comprising the steps of:

clocking said reference signal in real time to a charged coupled device having an input, an output, and several tapped stages;

clocking said reference signal from said input to said output and applying it therefrom to a microprocessor device;

calculating, in said microprocessor device, tap weights for an equalizer for correcting distortion based on said reference signal received by said microprocessor device;

storing said calculated tap weights in a tap weight storage;

clocking said digital format data signals into said charge coupled device in real time;

weighting said digital format data signals in said charge coupled device in accordance with said tap weights and obtaining equalized data signals;

decoding said equalized signal.

10. The method according to claim 9 wherein said clocking said reference signal from said input to said output occurs at a rate slower than the real time rate.