Rapid signal validity checking apparatus

• US 4,864,158 A
• Filed: 01/28/1988
• Issued: 09/05/1989
• Est. Priority Date: 01/28/1988
• Status: Expired due to Term

• Current Assignee: TC License Limited
• Original Assignee: Amtech Corporation (McClarin Plastics LLC)
• Inventors: Speirs, Donald F., Koelle, Alfred R., Hendrick, Peter L.
• Primary Examiner(s): Heyman, John S.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US07/149,609
• Time in Patent Office: 586 Days
• Field of Search: 307/231, 307/518, 307/528, 307/234, 328/108-112, 328/119, 328/130.1, 377/33, 377/51, 377/107, 377/45, 342/44, 371/55
• US Class Current: 327/31
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: H03K 5/19 Monitoring patterns of pulse trains indicating amplitude G01R19/00; indicating frequency G01R23/00; measuring characteristics of individual pulses G01R29/02

Abstract

This invention relates to an improved signal reader for reading signals from transponders placed on moveable objects such as ship containers, automobiles or railroad cars. The reader sends out a continuous signal, which is modified by the information contained in the transponder attached to the moveable object. Multiple antennas, each of which receive separate signals, may be multiplexed at the reader. The improved circuit of the invention provides quick recognition of the receipt of a valid signal from a transponder or, in the alternative, the absence of such a valid signal.

Claims

1. A circuit for early detection of a predetermined pulse stream having a given periodicity, comprising:

means for providing a detection pulse stream wherein the width of the pulses include the expected edges of said predetermined pulse stream;

first and second detecting means connected to receive said predetermined pulse stream for detecting the presence of the expected pulse edges during the duration of every other pulse of said detected pulse stream, and for providing a first output signal in the event of such detection, said second detecting means being out of phase with said first detecting means, said first and second detecting means also detecting the presence of a pulse edge in said predetermined pulse stream in the absence of coincidence with a pulse of said detection pulse stream, and providing a second output signal in the event of such detection; and

means for counting the number of said first output signals and said second output signals from each of said first and second detecting means and for providing a validity signal depending on a predetermined net number of said first output signals received from the one of the first and second detection means having the higher count for a given number of detection pulses.

2. The circuit of claim 1 wherein said means for counting is incremented once for the receipt of each first output signal and decremented once for the receipt of each second output signal, and said means for counting provides said validity signal when its net count reaches said predetermined net number.