controller and stepper driver support smooth ramp-up and ramp-down of the rotational velocity to
permit stable rotation without vibration. Nominal rotational scan velocity is in the range of 5 to 10
deg./sec.
Radio Frequency Assembly (RFA)
The radar RF electronics are mounted in an aluminum enclosure made of single aluminum slab 56mm
thick with a 6 mm central plate dividing the enclosure into two 22 mm deep cavities. (see Figure 26). A
gasket for the top and bottom plates makes the RF enclosure waterproof. The top and bottom covers are
3 mm thick aluminum plates. A single 19-pin MIL C26582 connector is used for signals and power to
the Radio Frequency Assembly (RFA). SMA microwave connectors for the TX output and RX inputs
are mounted on the side of the RFA.
The cable connecting the RFA and Instrument Computer carries power, serial communication, and the
analog receiver output. The RFA is powered by +24 volt DC that is then converted to the various
voltages used by the RFA modules in the DISTRI module inside the RFA enclosure.
The linear FM chirp generator and up-converter assembly (CHUPA) generates a programmable chirp in
the 900-1100 MHz frequency range. This signal is used both to drive the transmitter and to deramp the
received radar echo in the receiver.
The Ku-Band Microwave Assembly (KuMA) contains a Transmitter (TX) and two Receiver modules
(RX). The TX module accepts as input the chirp signal with a frequency range between 900 and 1100
MHz. This signal is up-converted, using a quadrature mixer to the 17.1 to 17.3 GHz frequency range
and then amplified. The TX RF output power level is approximately 100 mW at the TX output
connector.
The RX modules accept an microwave RF signal in the covering17.1 to 17.3 GHz and down-converts
this signal to the 900-1100 MHz band using a quadrature (IQ) mixer. The output signal level of the RX
module is approximately -60 dBm. The input local oscillator for both the TX and RX mixers has a
frequency of 8.1 GHz. The quadrature mixers have an internal x2 frequency multiplier to generate an
internal LO at 16.2 GHz that is used in the up or down conversion. An external 3-way power splitter is
used for the distribution of the 8.1 GHz local oscillator signal to the KuMa TX and RX modules.
The receiver IF amplifier assemblies (SIMA) amplify the output of the KuMA RX down-converters
and deramp the echo to obtain an echo in slant range geometry. Communication and control of the RFA
is via a micro-processor located in the CHUPA. The CHUPA can configure the chirp parameters,
receiver gain, and control power to the different modules. Thermally-controlled fans in the enclosure
circulate air to promote cooling and thermal stability.
