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Dimetra EBTS » History » Version 5

laforge, 02/21/2016 08:03 AM

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h1. Motorola Dimetra EBTS
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The Motorola Dimetra EBTS is a TETRA Base Station design.
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We have been able to get our hands on some of them.  This page documents our knowledge about the units, their configuration and how to use them.
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h2. Hardware
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h3. Motorola Dimetra Base Radio (T5931A)
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The Base Radio (BR) is a modular design in a 4U case, consisting of the following modules:
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h4. Power Supply (CPN1031B)
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As the name suggests, it is merely a power supply, converting from the 48 V input to the various voltages required within the radio
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h4. Controller (CAE010CMX)
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This is s small [[PowerPC]] based embedded system.  It communicates with the TETRA Site Controller (TSC) over 10-Base-2 Ethernet
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and controls all the other units of the Base Radio via the backplane of the BR cabinet.
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It has the following connections:
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* RS-232 on the back of the BR
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* RS-232 on the front of the BR
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* Site Alarm I/O on the back of the BR
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* 10-Base-2 Ethernet on the back of the BR (BNC)
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* Clock input on the back of the BR (BNC)
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For more details see [[[Dimetra_EBTSBase_RadioController]]]
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h4. 3x Diversity Receiver (CTX1090A)
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This is the receiver.  It has three antenna inputs in order to use antenna diversity for additional signal gain.
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The received and demodulated TETRA bursts are forwarded to the Controller via the BR backplane.
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For more details see [[[Dimetra_EBTSBase_RadioReceiver]]]
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h4. Exciter (CLN1510A)
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This is the transmitter.  It receives TETRA frames from the Controler via the backplane and encodes/modulates them.  The output
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is fed into the power amplifier over a SMA jumper connection on the back of the base radio.
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For more details see [[[Dimetra_EBTSBase_RadioExciter]]]
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h4. Power Amplifier (CTX1030A)
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This is a RF power amplifier, used to generate a high-power signal from the output of the exciter.
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It has three coaxial connections on the back, which are used as follows:
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* input from the exciter
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* feedback from PA into the exciter
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* actual RF power output (towards antenna)
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For more details see [[[Dimetra_EBTSBase_RadioAmplifier]]]
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h3. Integrated Site Controller (CLN1480A)
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This is a unit that interfaces up to 8 Base Radios with the core network of the Dimetra TETRA network (SwMI).
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Hardware-wise, it is a [[PowerPC]] based system, looking very much like an old-fashioned PC mainboard with
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both ISA and PCI slots.
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The mainboard houses the [[PowerPC]] CPU and it has slots for RAM.
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There are some extension cards plugged into the system:
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* Clock generation card (ISA, full length).
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** has an integrated GPS receiver, to which you attach a GPS antenna
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** generates the reference 5MHz clock distributed over Coaxial cable to the Base Radios
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* Ethernet Card using DEC tulip chipset (PCI)
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** This card is what talks to the Base Radios (BR) via 10-Base-2
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* Unknown card with RJ-45 jack (REDUND) on the back.  Might be E1
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There are further inputs and outputs on the system:
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* A DB-15 jack for X.21 synchronous serial backhaul (2048Mbps)
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* FIXME
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* A RS-232 serial port for local configuration
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For more details see [[[Dimetra_EBTSSite_Controller]]]
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h3. RF Distribution System (CFX4041A)
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This is a sophisticated combiner for the high-power output signals of the PA of up to 4 Base Radios.
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In order to ensure optimal impedance matching, the combiner is mechanically tuned by electrical motors
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which are controlled by some control logic.
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The combiner inside the system has the following connections (external connections in *bold*):
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* *4 high-power radio input ports* (N socket on the front, one close to each motor)
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** this is where the RF signal emitted by the PA of the BR enters
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* 4 RF taps, one for each of the high-power radio inputs
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** they are connected to the controller unit attached to the inside of the front lid
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* 1 high-power radio output port (N socket)
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** this output is connected to a power meter inside the same cabinet
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* 4 stepper motor electrical connections
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** connected to the controller unit attached to the inside of the front lid
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* RS-232 serial line for control+monitoring
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** this is a DB-9 port of the controller unit attached to the inside of the front lid
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** interconnected to one of the Base Radios (typically BR1) inside the rack
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The flow of the signals is as follows:
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* RF from the PA enters at the four combiner inputs
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* combined RF output leaves through central output of the combiner, from where
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* it is routed to the FR power meter
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* whose output socket is routed to the transmit antenna (or a duplexer in case of a shared Rx/Tx antenna)
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{{graphviz_link()
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digraph G {
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  graph [ rankdir = LR  ];
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  //{ rank=same; combiner; controller; };
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  br1_pa_out -> combiner
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  br2_pa_out -> combiner
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  br3_pa_out -> combiner
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  br4_pa_out -> combiner
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  combiner -> power_meter
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  power_meter -> tx_antenna
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  combiner -> controller [ dir=both color=red ]
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  power_meter -> controller [ color=red ]
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  power_meter [ shape=box ];
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  combiner [ shape=box ];
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  controller [ shape=box ];
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}
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}}
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h3. Rx LNA Multicoupler (CRX102A)
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The purpose of the Rx LNA multicoupler is to amplify the received signal from the antennas, and split
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the signal so each Base Radio is attached to each antenna:
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{{graphviz_link()
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digraph G {
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  graph [ rankdir = LR ];
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  antenna1 -> lna1
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  antenna2 -> lna2
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  antenna3 -> lna3
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  lna1 -> multicoupler1
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  lna2 -> multicoupler2
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  lna3 -> multicoupler3
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  multicoupler1 -> br1_rx1
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  multicoupler1 -> br2_rx1
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  multicoupler1 -> br3_rx1
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  multicoupler1 -> br4_rx1
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  multicoupler2 -> br1_rx2
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  multicoupler2 -> br2_rx2
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  multicoupler2 -> br3_rx2
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  multicoupler2 -> br4_rx2
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  multicoupler3 -> br1_rx3
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  multicoupler3 -> br2_rx3
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  multicoupler3 -> br3_rx3
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  multicoupler3 -> br4_rx3
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  lna1 [ shape=box label="LNA 1" ];
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  lna2 [ shape=box label="LNA 2" ];
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  lna3 [ shape=box label="LNA 3" ];
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  multicoupler1 [ shape=box ];
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  multicoupler2 [ shape=box ];
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  multicoupler3 [ shape=box ];
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}
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}}
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