Browse Prior Art Database

Secondary Surveillance Radar Reply Code Processing

IP.com Disclosure Number: IPCOM000083909D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Lebouquin, J: AUTHOR

Abstract

In order to be identified, a target which has detected the video signal from the radar sends back a reply code composed of framing Pulses F(1) and F(2) spaced 20.3 Mu s apart, which bracket a code of 13 pulses separated from each other by 1.45 Mu s.

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Secondary Surveillance Radar Reply Code Processing

In order to be identified, a target which has detected the video signal from the radar sends back a reply code composed of framing Pulses F(1) and F(2) spaced 20.3 Mu s apart, which bracket a code of 13 pulses separated from each other by 1.45 Mu s.

After conditioning, any pulse signal received is sampled and applied to the input of digital decoding shift register 10 consisting of 14 cells. The pulse signal is shifted through each cell in 1.45 Mu s, except for the last one 10-1 where the pulse signal is shifted through in 1.45 Mu s - Delta t, to take into account the framing pulses F(1), F(2) with leading edge separation of 20.3 Mu s +/- Delta t.

Each pulse leading edge which reaches output A of register 10 is considered a framing pulse F(1) and sets a bracket test timer I1. Timer 11 provides two windows having the same axis: a bracket test window the time interval of which is 2 Delta t and a code reading window the time interval of which is less than 2 Delta t. When the pulse leading edge appears at output A, timer 11 raises a line 12 which is an input to AND gate 13. Line 12 remains up during the bracket test.

If a pulse leading edge appears at input B of register 10, during the bracket test window, it will be considered as a F pulse. This pulse, via line 14, enables AND gate 13 which in turn, sets latch 18 which enables gate 19 until the end of the bracket test window when line 12 drops and resets latch 18. Th...