Encoding and decoding system

• US 6,885,716 B1
• Filed: 02/02/2000
• Issued: 04/26/2005
• Est. Priority Date: 08/20/1997
• Status: Expired due to Fees

• Current Assignee: Sarnoff Corporation (SRI International, Inc.)
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Evans, Robert M., Zalud, Peter F.
• Primary Examiner(s): Tse, Young T.
• Assistant Examiner(s): Ahn, Sam K.
• Application Number:
  US09/496,516
• Time in Patent Office: 1,910 Days
• Field of Search: 375/361, 375/354, 375/355, 375/359, 375/371, 375/376, 375/333, 375/282, 375/316, 375/236, 375/248, 375/262, 375/265, 375/341, 375/368, 375/365, 375/363, 375/240, 375/241, 341/70, 342/40
• US Class Current: 375/361
• CPC Class Codes: G07C 5/008 communicating information to a remotely located station transmission systems for measured values G08C
• CPC Class Codes: G08G 1/017 identifying vehicles G08G1/015, G08G1/054 take precedence
• CPC Class Codes: G08G 1/127 to a central station ; Indicators in a central station
• CPC Class Codes: H04J 3/0605 Special codes used as synchronising signal
• CPC Class Codes: H04L 25/4904 using self-synchronising codes, e.g. split-phase codes

Abstract

A decoder that receives a Manchester encoded signal including a start of frame sequence followed by coded data values followed by an end of frame sequence. The decoder also includes a detector that detects the start of frame sequence and the end of frame sequence to determine a beginning and end of the coded data values in the Manchester encoded frame. The decoder includes an integrator with hysteresis that includes an up-down counter and provides an output signal responsive to upper and lower threshold values. The output signal is applied to a discriminator that includes a counter which counts up in response to one value of the output signal of the integrator and is reset in response to the other value of the output signal of the integrator.

Claims

1. An integrator comprising:

receiving means for receiving a first signal including a first data value and a second data value different from the first data value;

counter means for increasing a count value up to a maximum count value when the first signal includes the first data value and decreasing the count value down to a minimum count value when the first signal includes the second data value;

data means for producing a third data value when the count value is equal to or greater than a first threshold value which is less than the maximum count value and a fourth date value when the count value is equal to or less than a second threshold value which is greater than the minimum count value; and

signal generating means for producing a second signal including the third data value and the fourth data value.

2. The integrator according to claim 1, further comprising a low pass filter comprising the counter means, the data means, and the signal generating means.

3. The integrator according to claim 1, wherein the counter means includes means for preventing the count value from exceeding the maximum count value which is greater than or equal to the first threshold value.

4. The integrator according to claim 1, wherein the counter means includes means for preventing the count value from exceeding the minimum count value which is less than or equal to the second threshold value.

5. A discriminator comprising:

receiving means for receiving a first signal including a first data value and a second data value different from the first data value;

counter means for increasing a count value when the first signal includes the first data value and resetting the count value to a predetermined value when the first signal includes the second data value; and

clock synchronization means for producing a clock synchronization signal when the count value is equal to or greater than a first threshold value.

6. The discriminator according to claim 5, wherein the clock synchronization means produces a second signal including a third data value when the count value is equal to or greater than the first threshold value and a fourth data value when the count value is reset.

7. The discriminator according to claim 5, wherein the counter means includes means for preventing the count value from exceeding a maximum value which is greater than or equal to the first threshold value.

8. A processor for decoding comprising:

an integrator including;

(a) receiving means for receiving a first signal including a first data value and a second data value different from the first data value,

(b) first counter means for increasing a first count value when the first signal includes the first data value and decreasing the first count value when the first signal includes the second data value,

(c) data means for producing a third data value when the first count value is equal to or greater than a first threshold value and a fourth data value when the first count value is equal to or less than a second threshold value, and

(d) signal generating means for producing a second signal including the third data value and the fourth data value; and

a discriminator including;

(a) second counter means for increasing a second count value when the second signal includes the third data value and resetting the second count value to a predetermined value when the second signal includes the fourth data value, and

(b) clock synchronization means for producing a clock synchronization signal when the second count value is equal to or greater than a third threshold value.

9. The processor according to claim 8, wherein the clock synchronization means producing a third signal including a fifth data value when the second value is equal to or greater than the third threshold value and a sixth data value when the second count value is reset.

10. The processor according to claim 9, further comprising decoding means for decoding the first signal in response to the third signal and the clock synchronization signals.