OsmocomTETRA

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h1. RF Distribution System (CFX4041A)

This is a sophisticated combiner for the high-power output signals of the PA of up to 4 Base Radios.

In order to ensure optimal impedance matching, the combiner is mechanically tuned by electrical motors

which are controlled by some control logic.

The combiner inside the system has the following connections (external connections in *bold*):

* *4 high-power radio input ports* (N socket on the front, one close to each motor)

** this is where the RF signal emitted by the PA of the BR enters

* 4 RF taps, one for each of the high-power radio inputs

** they are connected to the controller unit attached to the inside of the front lid

* 1 high-power radio output port (N socket)

** this output is connected to a power meter inside the same cabinet

* 4 stepper motor electrical connections

** connected to the controller unit attached to the inside of the front lid

* RS-232 serial line for control+monitoring

** this is a DB-9 port of the controller unit attached to the inside of the front lid

** interconnected to one of the Base Radios (typically BR1) inside the rack

The flow of the signals is as follows:

* RF from the PA enters at the four combiner inputs

* combined RF output leaves through central output of the combiner, from where

* it is routed to the FR power meter

* whose output socket is routed to the transmit antenna (or a duplexer in case of a shared Rx/Tx antenna)

{{graphviz_link()

digraph G {

  graph [ rankdir = LR  ];

  //{ rank=same; combiner; controller; };

  br1_pa_out -> combiner

  br2_pa_out -> combiner

  br3_pa_out -> combiner

  br4_pa_out -> combiner

  combiner -> power_meter

  power_meter -> tx_antenna

  combiner -> controller [ dir=both color=red ]

  power_meter -> controller [ color=red ]

  power_meter [ shape=box ];

  combiner [ shape=box ];

  controller [ shape=box ];

}

}}

h2. Images ==

 View into RF Distribution System after front lid is removed ===

[[Image(tetra_rf_distribution_open.jpg, 75%)]]

h3. Forward and reverse measurement inputs into controller

[[Image(tetra_rf_distribution_controller_in.jpg, 75%)]]