Instrumentation

To generate a 94GHz signal, AVTIS initially uses a 7.2GHz source fed through a x13 IMPATT frequency multiplier to provide a 94GHz 20mW signal.  This is then delivered to  the main transmit/receive subplate:

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Main IF plate for AVTIS 1 instruemnt

The 20mW input is boosted to 200mW by an IMPATT Injection Locked Amplifier (IILA).  Part of this signal is then coupled off to provide the Local Oscillator (LO) port with power, either as the reference copy of the transmit (Tx) signal for radar measurements or as a static LO for radiometric down-conversion of incoming thermal signals.

The main transmit path to the antenna proceeds through a Voltage Controlled Variable Attenuator (VCVA) (to turn Tx power on and off), a power monitor (Pmon) (to keep a record of the Tx level) and through the primary Tx/Rx circulator to the antenna. Power transmitted by the antenna is approximately 100mW.

Incoming signals are sent to the RF port of the mixer via the main circulator. The IF output of the mixer is then switched between a choice of Radar or Radiometer filtering and amplification.
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Assembled AVTIS 1 instruemnt

(i) Weight was always a primary consideration during the construction of AVTIS. The stand-alone Tx/Rx component subplates were made from light-weight honeycomb aluminium panels to minimise weight

(ii) The main housing consists of a rigid aluminium framework with three removable panels.

(iii) Inner view of the stepper motor driven pan and tilt gimbal

(iv) First ever AVTIS complete assembly with antenna

The finished radar assembly weighs just under 10kg, with the gimbal adding an additional 6kg.