Radar Field Analyser - RFA641 Edition Date: 28-Feb-18
10. PRIMARY TARGET INJECTION
10.1. Theory
The RFA641 will use a number of trigger signals from the radar to generate a simulated target on RF. The TX
output of the RFA641 shall be connected to the Radar Under Test (RUT) using a coupler or circulator
connected in the reception path of the radar. The RFA641 shall generate a square pulse-shaped return, with
a fixed power (depending on the target range) and width. The pulse is created independently from the
transmission pulse, so no correlation (e.g. in Doppler speed) between the transmitted pulse and the
reception pulse may be expected. Therefore this target injection tool is limited to radars without Doppler
processing (although due to the uncorrelated local oscillator of the target generator, the targets generated
should pass the Doppler filter banks of such radars).
10.1.1. Calculation of External Attenuation
Please bear in mind to use sufficient attenuation between the radar coupling connection and the RFA641 in
order not to damage the RFA641 output. This output can accept no more than 30 dBm ( 1W) reverse power,
so use sufficient attenuation.
A typical application with a 1 MW ( 60 dBW) power and 30 dB circulator, would still require minimal 30 dB
attenuation between the circulator port and the RFA641. From range equation calculations the user can
easily determine the exact value required for the external attenuation, but a typical value of 70 dB is
acceptable.
The attenuation value is also determined from the dynamic range required for the generation of the scenario.
The RFA typically has an output dynamic range of +15 to -45 dB (accurate to 1 dB). This implies that using a
70 dB attenuator, targets between -55 and -115 dBm can be generated.
The following example shows a test flight over 10-100 Nm using a fixed RCS of 1 m
2
. Obviously, when RCS
is changed or swirling cases are included, the dynamic range may change and the attenuator value should
be changed according to the output dynamic range.
IE-UM-00165-005 RFA641 User Manual.odt 88/110
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