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RF Network Propagation Simulator
Under government contract, AISD, Inc. has been developing an RF network propagation simulator (RFN) that allows the government to test JTIDS terminals and navigation equipment in the lab, simulating distance related attenuation and delay as would be experienced in a dynamic combat situation. Current versions support the Link-16 bands, and are in use by US Navy. As of Q1, 2008, we are in the latter stages of RFN Increment 2 development, which is designed to support JTRS radios operating from 2 MHz through 2 GHz.

System Overview

The system consists of eight RF Delay Channel boards, a System Controller, a proprietary backplane, and lots of RF plumbing housed in a 19 inch rack mountable chassis. Connectivity to the RFN are through eight radio antenna input/outputs and eight jammer inputs (N-type). Under computer control, each radio can be connected through the RFN to any one or more (up to seven) other radios, delayed and attenuated by an amount appropriate to their distance from one another. With 56 independent programmable paths, the RFN supports up to four isolated networks of radios; from one network of eight radios to four networks of two radios each. Delay and attenuation can be varied statically or dynamically to provide a real time simulation. In a scripted environment, dynamic control allows radios in a net of 2 - 8 participants to be moved on a playing field relative to one another, each of which having an associated position, velocity and acceleration. The propagation delay of each participant relative to one another is varied at a 5 KHz rate. The attenuation is updated at a 2 Hz rate.

Control Application

The RFN GUI is a multi-threaded Windows application that allows convenient configuration of RFN settings. It communicates over a TCP/IP network with the RFN server application (on the System Controller board), and in dynamic scripted mode of operation, with a Script Controller. An operator can set up RF networks of radios, get RFN status information, and perform some RFN diagnostics.

System Controller

The System Controller includes a proprietary TCP/IP server application running on embedded Linux, and is the focal point of communications between the networked RFN GUI client application and the Delay Channel boards. The System Controller board provides 16 independently tunable local oscillator channels (200 MHz - 2500 MHz) and digital bus communication/control with the Delay Channel boards.

RF Delay Channel

The RF Delay Channel provides three functions; programmable delay, programmable attenuation, and delay bypass.

Path delay is implemented in the digital domain using FPGAs, RAM, ADCs and DACs, with a maximum of 13.2 ms configurable, which equates to roughly 2500 miles of propagation delay. Each path of the attenuation section includes a 62 dB programmable RF attenuator. These two parameters are calculated using various atmospheric models for dynamic mode or are set in various ways using the GUI in static mode.

In dynamic mode, the Delay Channel hardware calculates and updates the dynamic delay to other radios in the network at a 5 KHz rate.

A delay bypass mode is provided to support operation from 2 MHz to ~150 MHz.

RF System Backplane

The RF System Backplane provides high isolation ( >105dB ) RF distribution paths between the System Controller and the Delay Channel board. It also provides a digital bus for communication between the System Controller and the Delay Channels, and power distribution.

For more information about our design capabilities contact us at info@aisdInc.com

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RF Network Propagation Simulator

RF Channel Delay Board

System Controller, w/half of the LOs populated

Radio, jammer, network and timing inputs

Backplane and I/O splitter routing

 

 
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