Electronic countermeasure system

Claim 2

An airborne electronic countermeasures systems for intercepting and imitating responding IFF signals from aircraft identified as friendly by an interrogator, said system comprising: a receiver-decoder means for receiving and decoding responding IFF signals from said aircraft, said receiver-decoder means including means for inhibiting and decoding of received signals having a pulse width less than a selected amount; control means (coupled and responsive to said receiver-decoder means) for selecting a code similar to that of said decoded IFF signal; and transponder means coupled to said control means for receiving interrogation signals from said interrogator and for transmitting (coded signals) the selected code in response to said interrogation signals, thereby imitating responding IFF signals from said aircraft.

Claim 3

An airborne electronic countermeasures system as recited in claim 1 wherein said transponder means further comprises: tuning means for scanning a frequency band for the presence of said interrogation signals; electrical means coupled to said tuning means for receiving and amplifying said interrogation signals; coder means responsive to said control means and operatively connected to said electrical means for determining the code of said coded signals; and transmitter means coupled to said tuning means and responsive to said coder means and to said electrical means for transmitting said coded signals in response to said interrogation signals.

Claim 4

An airborne electronic countermeasures system as recited in claim 2 wherein said electrical means comprises: detector means coupled to said tuning means for detecting the presence of said interrogation signals; amplifier means coupled to said detector means for amplifying the detected interrogation signals; modulator means responsive to said amplifier means and coupled to said transmitter means and said coder means for controlling the operation of said transmitter means; said detector means, amplifier means and modulator means forming a feedback loop with said transmitter means for initiating operation of the said transmitter means in response to said interrogation signals by causing an immediate build-up of signals in said feedback loop many times the amplitude of said interrogation signals, thereby causing said transmitter means to transmit a signal with a pulse repetition frequency determined by said interrogating signals and the pulse widths determined by said coder means.

Claim 5

An airborne electronic countermeasure system as recited in claim 2 wherein said coder means comprises: a plurality of switching means connected to said control means; and means operatively connected with said plurality of switching means for determining the code of said coded signals in accordance with the selected code from said control means.

Claim 6

An airborne electronic countermeasure system for intercepting and imitating responding IFF signals from aircraft identified as friendly by an interrogator, said system comprising: a receiver-decoder means for receiving and decoding responding IFF signals from said aircraft, said receiver-decoder means including: scanning means for searching a frequency band for said responding IFF signals; circuit means coupled to said scanning means for amplifying and detecting said responding IFF signals, thereby forming detected pulses having envelopes similar to said responding IFF signals; discriminator means coupled to said circuit means for rejecting said detected pulses narrower than a selected pulse width and differentiating said detected pulses greater than said selected pulse width, thereby forming positive and negative pulse portions; selector means coupled to said discriminator means for separating said positive and negative pulse portions; (and) decoder means coupled to said selector means for decoding said positive and negative pulse portions and for identifying said responding IFF signals; control means for selecting a code similar to that of said decoded IFF signal; and transponder means coupled to said control means for receiving interrogation signals from said interrogator and for transmitting the selected code in response to said interrogation signals, thereby imitating responding IFF signals from said aircraft.

Claim 7

An airborne electronic countermeasure system for intercepting and imitating responding IFF signals from aircraft identified as friendly by an interrogator, said system comprising: a receiver-decoder means for receiving and decoding responding IFF signals from said aircraft, said receiver-decoder means including: scanning means for searching a frequency band for said responding IFF signals; circuit means coupled to said scanning means for amplifying and detecting said responding IFF signals, thereby forming detected pulses having envelopes similar to said responding IFF signals; discriminator means coupled to said circuit means for rejecting said detected pulses narrower than a selected pulse width and differentiating said detected pulses greater than said selected pulse width, thereby forming positive and negative pulse portions; selector means coupled to said discriminator means for separating said positive and negative pulse portions; (and) decoder means coupled to said selector means for decoding said positive and negative pulse portions and for identifying said responding IFF signals; control means for selecting a code similar to that of said decoded IFF signal; and transponder means coupled to said control means for receiving interrogation signals from said interrogator and for transmitting the selected code in response to said interrogation signals, thereby imitating responding IFF signals from said aircraft.

Claim 8

An airborne electronic countermeasures system as recited in claim 5 wherein said transponder means further comprises: tuning means for scanning said frequency band for the presence of said interrogation signals; electrical means coupled to said tuning means for receiving and amplifying said interrogation signals; coder means responsive to said control means and operatively connected to said electrical means for determining the code of said coded signals; and transmitter means coupled to said tuning means and responsive to said coder means and said electrical means for transmitting said coded Signals in response to said interrogation signals.

Claim 9

An electronic countermeasures system as recited in claim 6 wherein said electrical means further comprises: detector means coupled to said tuning means for detecting the presence of said interrogation signals; amplifier means coupled to said detector means for amplifying the detected interrogation signals; modulator means responsive to said amplifier means and coupled to said transmitter means and said coder means for controlling the operation of said transmitter means; said detector means, said amplifier means and said modulator means forming a feedback loop with said transmitter means for initiating operation of said transmitter means in response to said interrogation signals by causing an immediate build-up signals in said feedback loop many times the amplitude of said interrogation signals, thereby causing said transmitter means to transmit a signal with a pulse repetition frequency determined by said interrogating signals and the pulse widths determined by said coder means.

Claim 10

An airborne electronic countermeasure system as recited in claim 6 wherein said coder means comprises: a plurality of switching means connected to said control means; and means operatively connected with said plurality of switching means for determining the code of said coded signals in accordance with the selected code from said control means.

Claim 11

An electronic countermeasure system as recited in claim 5 wherein said discriminator means comprises: input means coupled to said circuit means for receiving said detected pulses; delay means coupled to said circuit means of receiving said detected pulses and for delaying said detected pulses a selected amount of time; coincidence means coupled to said input means and to said delayed detected pulses for generating a coincidence pulse having a width equal to the coincidence time of said pulses; and pulse forming means coupled to the output of said coincidence means for differentiating said coincidence pulse and for generating positive and negative pulse portions.

Claim 12

An airborne electronic countermeasure system as recited in claim 5 wherein said decoder means comprises: a plurality of generator means each having an input and first and second outputs, the input of a first generator means connected to said selector means and the inputs of the other of said plurality of generator means connected to the first outputs of a preceding generator means in a series relationship; a coincidence bus means connected to the second outputs of said plurality of generator means; a plurality of multivibrator means each having an input connected to said coincidence bus means; a plurality of indicator means operatively coupled to the outputs of said plurality of multivibrator means for causing said indicator means to display said decoded IFF signals.

Claim 13

An airborne electronic countermeasure system operating in a hostile IFF environment for deceiving a hostile interrogator into identifying an aircraft equipped with said system as friendly to said environment, said system comprising: receiver-decoder means for receiving and decoding a responding IFF radio frequency signal from an aircraft friendly to said interrogator, said receiver-decoder means including: scanning means for searching a frequency band for said responding IFF signals; circuit means coupled to said scanning means for amplifying and detecting said responding IFF signals, thereby forming detected pulses having envelopes similar to said responding IFF signals; discriminator means couples to said circuit means for rejecting said detected pulses narrower than a selected pulse width and differentiating said detected pulses greater than said selected pulse width, thereby forming positive and negative pulse portions; selector means coupled to said discriminator means for separating said positive and negative pulse portions: (and) decoder means coupled to said selector means for decoding said positive and negative pulse portions and for identifying said responding IFF signals; control means for selecting a code substantially similar to that of the responding aircraft; and transponder means coupled to said control means for receiving interrogation signals from said interrogator, and for transmitting said selected code in response to said interrogation signals thereby causing said interrogator to identify said selected code as emanating from a friendly aircraft.

Claim 14

An airborne electronic countermeasure system operating in a hostile IFF environment for deceiving a hostile interrogator into identifying an aircraft equipped with said system as friendly to said environment, said system comprising: receiver-decoder means for receiving and decoding a responding IFF radio frequency signal from an aircraft friendly to said interrogator, said receiver-decoder means including: scanning means for searching a frequency band for said responding IFF signals; circuit means coupled to said scanning means for amplifying and detecting said responding IFF signals, thereby forming detected pulses having envelopes similar to said responding IFF signals; discriminator means couples to said circuit means for rejecting said detected pulses narrower than a selected pulse width and differentiating said detected pulses greater than said selected pulse width, thereby forming positive and negative pulse portions; selector means coupled to said discriminator means for separating said positive and negative pulse portions: (and) decoder means coupled to said selector means for decoding said positive and negative pulse portions and for identifying said responding IFF signals; control means for selecting a code substantially similar to that of the responding aircraft; and transponder means coupled to said control means for receiving interrogation signals from said interrogator, and for transmitting said selected code in response to said interrogation signals thereby causing said interrogator to identify said selected code as emanating from a friendly aircraft.

Claim 15

An airborne electronic countermeasure system as recited in claim 11 wherein said transponder means comprises: tuning means for scanning a frequency band for the presence of said interrogation signals; electrical means coupled to said tuning means for receiving and amplifying said interrogation signals; coder means responsive to said control means and operatively connected to said electrical means for determining the code of said coded signals; and transmitter means coupled to said tuning means and responsive to said coder means and to said electrical means for transmitting said coded signals in response to said interrogation signals.

Claim 16

An airborne electronic countermeasure system as recited in claim 12 wherein said control means comprises: means for providing a plurality of sequential signals; and a plurality of code lines selectively engageable to said plurality of sequential signals for establishing a coded signal to control said coder means.

Claim 17

An airborne electronic countermeasure system for receiving and decoding radio frequency signals in a frequency band and transmitting decoded signals in reply to an interrogation, said system comprising: a ground-based interrogator means; a first aircraft friendly to said interrogator means having means for receiving interrogation signals from said interrogator means and responder means for transmitting to said interrogator means coded signals for identifying itself; a second aircraft having means for intercepting and imitating said coded signals; and means within said second aircraft for transmitting reply signals to said interrogator means in response to said interrogation signals from said interrogator means, said reply signals having characteristics similar to said coded signals from said first aircraft, thereby causing said second aircraft to be identified as friendly in a hostile environment.

Claim 18

An airborne electronic countermeasure system for receiving and decoding radio frequency signals in a frequency band and transmitting decoded signals in reply to an interrogation, said system comprising: a ground-based interrogator means; a first aircraft friendly to said interrogator means having means for receiving interrogation signals from said interrogator means and responder means for transmitting to said interrogator means coded signals for identifying itself; a second aircraft having means for intercepting and imitating said coded signals; and means within said second aircraft for transmitting reply signals to said interrogator means in response to said interrogation signals from said interrogator means, said reply signals having characteristics similar to said coded signals from said first aircraft, thereby causing said second aircraft to be identified as friendly in a hostile environment.

Claim 19

An airborne electronic countermeasure system as recited in claim 14 wherein said means for intercepting and initiating comprises: scanning means for searching said frequency band for said coded signals; circuit means coupled to said scanning means for amplifying and detecting said coded signals, thereby forming detected pulses having envelopes similar to said coded signals; discriminator means coupled to said circuit means for rejecting said detected pulses narrower than a selected pulse width and differentiating said detected pulses greater than a selected pulse width, thereby forming positive and negative pulse portions; selector means coupled to said discriminator means for separating said positive and negative pulse portions; decoder means coupled to said selector means for decoding said positive and negative pulse portions, thereby identifying and displaying the code of said coded signals; means actuated by said scanning means for generating a plurality of sequential signals; and a plurality of code lines selectively engageable in accordance with the displayed code for establishing the code of said reply signals.

Claim 20

An airborne electronic countermeasure system as recited in claim 15 wherein said means within said second aircraft comprises: tuning means for scanning said frequency band for the presence of said interrogation signals; electrical means coupled to said tuning means for receiving and amplifying said interrogation signals; and transmitter means couPled to said tuning means and responsive to said plurality of code lines for transmitting said reply signals to said interrogator means.