Transponder

Claim 2

A frequency agile transponder, comprising: means for receiving a relatively narrow interrogating signal pulse of a particular frequency falling within a given frequency band, and means responsive to said interrogating signal pulse for transmitting a coded series of reply pulses that are frequency synchronized with said interrogating signal pulse, said responsive means including frequency memory means for receiving a frequency coherent pulse indicative of the interrogating signal pulse and converting the frequency coherent pulse to a coded series of frequency coherent pulses, said frequency memory means being phase coded to prevent envelope cancellation in the series of pulses.

Claim 3

The transponder according to claim 1, wherein said transponder is responsive to incoming signal pulses in an RF frequency range and wherein said responsive means includes means for down-converting the incoming RF pulse into an IF pulse and supplying the IF pulses to the frequency memory means for pulse encoding the IF pulse into a series of delayed wider duration IF pulses that are frequency synchronized with the IF pulse, and means for up-converting the series of delayed wider duration IF pulses into a corresponding series of delayed wider RF pulses which are frequency synchronized with the incoming RF pulse.

Claim 4

The transponder according to claim 1, wherein said frequency memory means is an acoustic surface wave device.

Claim 5

The transponder according to claim 3, wherein said acoustic surface wave device includes a Barker coded input transducer for generating an acoustic pulse without signal cancellation at discrete frequencies within the IF band of an interrogating radar receiver and an output transducer for encoding said acoustic pulse into the series of coded and delayed IF pulses.

Claim 6

The transponder according to claim 4, wherein said Barker coded input transducer includes transducer pairs designed to lengthen the received IF pulse and convert the stretched IF pulse into an acoustic pulse.

Claim 7

A frequency agile transponder comprising: means for receiving a relatively narrow segment of an interrogating signal pulse, the pulse having a frequency falling within a given frequency band; frequency memory means responsive to said segment for transmitting a series of variously delayed segments substantially similar to the received segment; and means coupled to said frequency memory means for augmenting the phase shift produced by the time delay of any transmitted segment by a phase angle substantially independent of frequency, said augmenting phase angle being chosen for each segment to enhance the peak response of a receiver responsive to signals in a band including the segment frequency, which band is narrow relative to the given frequency band and to the inverse of the segment duration.

Claim 8

A frequency agile transponder comprising: means for receiving a relatively narrow segment of an interrogating signal pulse, the pulse having a frequency falling within a given frequency band; frequency memory means responsive to said segment for transmitting a series of variously delayed segments substantially similar to the received segment; and means coupled to said frequency memory means for augmenting the phase shift produced by the time delay of any transmitted segment by a phase angle substantially independent of frequency, said augmenting phase angle being chosen for each segment to enhance the peak response of a receiver responsive to signals in a band including the segment frequency, which band is narrow relative to the given frequency band and to the inverse of the segment duration.

Claim 9

The transponder according to claim 6 wherein the transmitted series of variously delayed and phase shifted segments is further modulated to convey information to the narrow band receiver.

Claim 10

The transponder according to claim 6 wherein the series of variously delayed segments is three segments.

Claim 11

The transponder according to claim 8 wherein the means for augmenting the phase shift of the three delayed segments provides phase angles of 0°, 0° and 180°, respectively.

Claim 12

The transponder according to claim 8 wherein the means for augmenting the phase shift of the three delayed segments provides phase angles of 0°, 180° and 180°, respectively.