Product Manual for Tornado X and Tornado XR
17
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Digital Processing System (DPS)
•
Transceiver (TRCVR)
•
Duplexers (DPLXR)
These modules are described in detail in the sections that follow.
User data (Ethernet or serial) passes from the various interfaces into the Digital Processing System (DPS) where
sophisticated processing takes place to code the data into a MIMO signal. This MIMO signal is created completely
digitally inside the DPS. The DPS then generates two signals at an IF frequency. There are two uncorrelated
signals because ultimately the signals will pass onto separate elements on the antenna. The Intermediate
Frequency (IF) signals are then passed on to the Transmitter module which mixes the signals up to the desired
frequency and also amplifies the signals to the required levels. The signals then pass through the duplexers. The
duplexers are special filters which prevent the transmitted signals from feeding back into the receiver module. Next
the signals are fed to the antenna.
The antenna is a special MIMO antenna which is able to transmit and receive on both the vertical and horizontal
polarisations at the same time. The MIMO antennas are essentially two antennas in one.
On the receive path, the radio signals are picked up by the MIMO antenna and fed through the duplexers and into
the receiver module. The receiver selects the radio frequency to receive and mixes this signal down to an IF. This
IF signal is then sampled by Analogue to Digital Converters (ADCs) on the DPS module. The DPS module then
performs very complex MIMO processing to decode the user data that was sent. This data is then passed to the
appropriate interface.
3.2
D
IGITAL
P
ROCESSING
S
YSTEM
The DPS is the heart of the radio unit. It provides an accurate and stable 40MHz system reference clock from which
all the required digital clocks and RF local oscillator frequencies for transmit and receive functions are derived. It
processes signals that have been transmitted or received and provides overall control and monitoring to the rest of
the system via the built-in Configuration, Control and Management Software CCMS software. Power supplies are
also provided by the DPS.
3.2.1
POWER SUPPLY
The power supply operates off a 10.5 to 60 VDC input and generates stable 13.6V, 5.8V, 5.0V, 3.3V, 2.5V,1.8V
1.2V and 18V internal power supply rails, that all the other circuitry runs off.
The base station Tornado has an isolated input power supply, and the Remote Tornado has a non-isolated Power
supply.
3.2.1.1 Tornado X Radio
The input of the power supply is isolated from the rest of the circuitry and the chassis. Input voltage monitoring is
provided via CCMS.
3.2.1.2 Tornado XR Radio
The input of the power supply is non-isolated. Input voltage monitoring is provided via CCMS.
3.2.2
CENTRAL PROCESSOR UNIT
An ARM Cortex A8 based microcontroller is used as the CPU in the DPS board. It uses a reference clock of 26MHz.
The CPU provides external device connectivity through the built-in and external peripherals.
The CPU runs a Linux embedded operating system which provides various services such as scheduling, process
management, memory management, device and resource management, TCP/IP stacks and inter-networking,
applications, user interface, system configuration and control etc. An integral part of the Linux operating system is
the Mimomax specific network driver, which configures the radio unit as a standard Ethernet device.
3.2.3
FPGA
An Altera Cyclone IV Field Programmable Gate Array is used to implement the physical layer TX and Rx signal
processing, MAC layer and signalling protocols on the serial interfaces.
