Method for realtime digital processing of communications signals

• US 20040037253A1
• Filed: 08/22/2002
• Published: 02/26/2004
• Est. Priority Date: 08/22/2002
• Status: Active Grant

• Current Assignee: Callahan Cellular LLC (Intellectual Ventures LLC)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Luthi, Peter O., Boland, Robert P., Thiele, Matthew J., Simonson, Peter
• Granted Patent: US 7,573,864 B2
• Time in Patent Office: Days
• US Class Current: 370/337
• CPC Class Codes: G01S 13/222 using random or pseudorandom pulse repetition frequency
• CPC Class Codes: G01S 7/282 Transmitters
• CPC Class Codes: H04J 3/0685 Clock or time synchronisation in a node; Intranode synchronisation
• CPC Class Codes: H04W 56/00 Synchronisation arrangements

Abstract

In a communications or jamming system, accurate timing of the transmission of digitally processed signals is accomplished through the use of standard off-the-shelf components. In order to eliminate the need for high-cost, difficult to develop, specific digital hardware or realtime synchronous software not available from the standard off-the-shelf components, the output from the non-real time components is coupled to a realtime interface that assures nanosecond timing accuracy regardless of timing errors introduced by the off-the-shelf components. In one embodiment, the signals to be transmitted are digitized and then packetized, with the data to be transmitted reconstructed using non-real time digital processing. In order to establish the exact time for transmission, the packet is given a time stamp in the form of a header which indicates the exact time at which the packet is to be transmitted by the communications system, with the packet with header being transmitted to a storage buffer, the output of which is coupled to a realtime interface including a precise time output gate, the timing of which is controlled by a precision time reference having nano-second accuracy.

Claims

1. A method for assuring the accurate timing of a packetized transmission, comprising the steps of:

generating a packet of data having a header including a timestamp indicating the time that the packet is to be transmitted using a non-realtime off-the-shelf digital processor; and

,

gating out the packet at a precise time for transmission in accordance with the timestamp using a realtime precision time reference, whereby timing errors associated with the generation of the packet by standard off-the-shelf digital processors do not affect the timing of the transmission of the packet.

2. A method for using standard off-the-shelf components to generate and transmit packetized data at precise times, comprising the steps of:

generating the packets using non-realtime off-the-shelf components; and

,

gating the packets for transmission using a realtime interface including a precision clock, whereby timing errors of the off-the-shelf components are not dominant.

3. The method of claim 2, wherein this generating step includes providing each of the packets with a header having a timestamp indicating the precise time at which the packet is to be transmitted, and wherein the gating step includes gating the packet at the time specified by the timestamp.

4. The method of claim 3, wherein the gating step includes buffering the packets prior to gating.

5. The method of claim 4, wherein the gating step includes providing time from a realtime clock and comparing the time from the realtime clock with that of the timestamp, and when the two times match gating the packet for transmission.

6. The method of claim 5, wherein the realtime clock has a nanosecond accuracy.

7. The method of claim 6, wherein the realtime clock includes a rubidium oscillator.

8. The method of claim 2, wherein the timing accuracy for the non-realtime components is in the millisecond range.

9. The method of claim 2, wherein the realtime timing accuracy is greater than that of the non-realtime components.

10. The method of claim 2, wherein the realtime accuracy is in the nanosecond range.

11. The method of claim 5, wherein the realtime clock includes a GPS receiver for providing an absolute time reference.