Broadband data modulation system

DETAILED DESCRIPTION OF THE INVENTION In testing and evaluating radar systems it is necessary to simulate very realistically to the radar the flights of aircraft and missiles that the radar is to sense and keep track of.
To realistically simulate aircraft and missile azimuth and elevation angles in space, a very large array of RF transmitters is necessary, to transmit toward the radar the simulations of the aircraft and missile radar reflections.
Communicating these simulations to the large array of RF transmitters is difficult and requires special circuits and subsystems.
FIG.
1 shows in simplified block form a typical system to process the actual radar transmissions to provide the desired simulation data for transmission to the array of RF transmitters.
Radar pulses typically 5250 plus or minus 250MHz are heterodyned in a mixer 11 with the continuous wave 3750MHz output from a local oscillator 12 to derive difference pulses at 1500 plus or minus 250MHz which are divided by a square root circuit 13 and are delivered as 375 plus or minus 62.
5MHz pulses to a range-delay, doppler, attenuation processing circuit 14, which is computer-controlled to modify the 375 plus or minus 62.
5MHz input pulses to delay them in time according to the desired simulated radar-to-aircraft range, set the signal level to correspond to the desired simulated range and aircraft size, and add a doppler signal in proportion to the desired simulated radial velocity of the aircraft.
The signals at 15 comprising the modified pulses from the device 14 cover a wide band width, and with standard prior technique it is difficult to satisfactorily transmit the signals to the large array of RF transmitters.
There are too many transmitters in the array to allow transmitting these signals by cables.
RF carriers are not feasible, as the antenna patterns cannot be suitably focused on to the array.
It is, therefore, necessary to perform the communication with an IR (or optical) carrier.
Designated at 16 is an optical carrier source, such as a CO