초록 ▼

Diclosed is a dual band communication receiver for use in a burst communication sytem. The receiver is capable of esentially simultaneous reception at a first carrier frequency (L), such as L-band and a higher carrier frequency (H), such as S-band, using distinct codes and replying in the frequency

Diclosed is a dual band communication receiver for use in a burst communication sytem. The receiver is capable of esentially simultaneous reception at a first carrier frequency (L), such as L-band and a higher carrier frequency (H), such as S-band, using distinct codes and replying in the frequency band received. A typical system is composed of a transponder and an interrogator. The incoming coded signal is down converted to an i.f. frequency compatible with surface acoustic wave (SAW) convolvers. The i.f. signal is then divided between two SAW convolvers, each having a convolution interval of two times the message symbol length (2T). Reference signals A and B are composite signals comprised of alternate L-band and H-band signals, each having a time period equal to T and each L- or H-band signal operating at a 50% duty cycle. Reference signals A and B are time reversed to the input signals applied to the convolver and are orthogonal to one another. Each of the convolver outputs are processed through log video detection circuits to reduce the dynamic range followed by peak detecting and stretching to reduce the pulse bandwidth. The outputs from each peak detection and stretching circuitry are coupled to a smaple-and-hold circuit which are in turn divided such that one path is to synchronization and interrogation sidelobe suppression (also referred to as sidelobe inhibit, ISLI or control signal) matched filters designed to look for the particular symbol sequences between the two convolver channels characteristic of the preamble and ISLI signals. The synchronization signal and the sidelobe suppression signal are used in order to determine if a valid preamble has been detected by the receiver and if the receiver is in a desired portion of the interrogator radiation pattern; if so, then a timing or address signal and the remaining portion of the message which contains the data is clocked into a memory.

대표청구항 ▼

A dual band IFF system comprising: (a) a plurality of interrogators each comprising an interrogator transmitter and receiver, said interrogator transmitter transmitting a multibit coded message including synchronization and data information on the sum pattern and a control signal on the difference p

A dual band IFF system comprising: (a) a plurality of interrogators each comprising an interrogator transmitter and receiver, said interrogator transmitter transmitting a multibit coded message including synchronization and data information on the sum pattern and a control signal on the difference pattern, each bit being of length T, said message being transmitted at a low (L) or high (H) carrier frequency, (b) at least one dual band transponder comprising a transponder transmitter and receiver, said dual band transponder receiver detecting and validating receipt of said message and control signal at said L or H carrier frequency and said transponder transmitter transmitting a unique message at a carrier frequency L or H corresponding to the carrier frequency detected by the transponder receiver in response thereto which is detected by said interrogator receiver, and (c) said transponder receivers each comprising: (1) a reference signal generating means for generating A and B reference signals having alternate L and H band carrier signals, such that each L or H band signal operates at a 50% duty cycle and each bit has a bit length of T, (2) at least two receiver channels A and B, channel A comprising an i.f. stage for producing a dual band i.f. representation of the coded multibit signals, a convolver having a convolution interval of 2T and having an input, reference and output port, said input port connected to the i.f. frequency stage for receiving the dual band i.f. representation of the coded multibit signals, the reference port coupled to the reference signal generating means for receiving the reference signal A whereby said convolver produces at its output port a dual band i.f. amplitude correlation of said dual band coded multibit input signal when said reference signal A and a bit of information from said coded input message exactly correlate and coincide in said first convolver, signal processing means coupled to said output port for converting such correlated dual band i.f. signal to a first video signal and producing its maximum amplitude during pre-determined time intervals to form the output signal of channel A, Channel B comprising an i.f. stage for producing a dual band i.f. representation of the coded multibit signals, a convolver having a convolution interval of 2T and having an input, reference, and output port, said input port connected to the i.f. stage for receiving the same signal as the input port of said first convolver, the reference port coupled to the reference signal generating means for receiving the reference signal B, whereby said convolver produces at its output port a dual band i.f. amplitude correlation of said dual band coded multibit input signal when said reference signal B and a bit of information from said dual band coded input message exactly correlate and coincide in said convolver, signal processing means coupled to said output port for converting such correlated dual band i.f. signal to a second video signal and producing its maximum amplitude during predetermined time intervals to form the output signal of channel B, (3) processor means coupled to receive the output signals of channels A and B for detecting, storing and de-interleaving said overlapping messages and including a plurality of memory locations, and (4) synchronization detection circuitry coupled to receive the output signals of channels A and B for detecting synchronization of said overlapping messages to establish time of arrival of said dual band overlapping coded multibit message input signals and produce signals selectively to said plurality of memory locations to transfer the data bits into selected memory locations.