Technical Manual

SRT X-BAND RADAR SYSTEMS
FUNCTIONAL DESCRIPTION
304202P003 3.12 Rev. C
two-BALANCED MIXER and the LOCAL OSCILLATOR; RF_Detector is the
final amplification stage and it is of the logarithmic kind.
The RF Head is designed to generate RF pulses in the X-Band range up to 12
or 25 kW and to receive echo from targets.
During transmission time, the MAGNETRON receives a high voltage trigger
pulse, whose length ( short / medium / long ) is determined by the operator
settings on Display, and generates high power RF pulses in the X-Band range
until the high voltage pulse is applied to its cathode.
The RF energy generated is sent to the CIRCULATOR, and from this to the
waveguide which delivers the energy for the radiating Antenna.
The CIRCULATOR is a 3-way microwave device used either as a RF switch or
to send the transmission pulses to the Antenna or to apply the received echoes
to the Receiver.
The second function carried out by the RF HEAD unit is to convert, the
receiving R.F. energy, reflected from targets, into intermediate frequency, (I.F.)
and amplify it. This is provided by the R.F. HEAD block mainly consisting of:
− Limiter
− Integrated RF Amplifier composed of:
. Low Noise Front End (Low Noise Amplifier, Mixer, LO)
. RF Detector
The echo signal received by the Antenna arrives, through the Limiter and the
Low Noise Amplifier, to the Mixer where it is mixed with the signal forwarded by
the Local Oscillator. The resulting beat is the 60 MHz IF signal which is
forwarded to the RF_Detector. The Limiter is used to avoid an output above a
scheduled value. A higher output would cause a short-circuit.
The Low Noise Amplifier and the Image Rejection Filter are used to amplify the
echo signal in order to improve the noise figure of the receiver. The Local
Oscillator is integrated directly into the LNFE. It can be tuned up to the
Magnetron transmission frequency trough the VCO voltage level.
The RF Detector Assy’s function (Chapter 9, Figure 9.1.24 and Figure 9.1.25) is
to amplify the echo signals delivered by the RF HEAD Assy. It is composed of a
Group Amplifier stages, cascade connected, with specific components so to
obtain a logarithmic dynamic characteristic. The central frequency is 60 MHz
and the bandwidth is 1.8 MHz for Long Pulse, 4.5 MHz for Medium Pulse, 24
MHz for Short Pulse.
To maintain the target echo signals free from any possible external induction
that can degrade the performance of the Unit, the DC power supply voltages
and the band switching commands are applied to the module by means of a
FILTER.
3.2.3 Brushless Motor Controller