Hybrid radio frequency (RF) simulation is now widely used for radar, electronic warfare (EW), or laboratory communication equipment tests. This laboratory-based simulation reproduces "real life" electromagnetic environments seen by receivers such as handsets or complex radar systems.
Because RF simulation involves the generation of millions of RF pulses and signals, it consumes much real-time computing power to control the synthesizers in charge of microwave generation. This real-time data processing was traditionally dedicated to digital signal processing (DSP) equipment, while high-level software ran on workstations or multiprocessor-networked PCs.
OMEGA-TECHNOLOGIES S.A., a subsidiary of Thomson-CSF in Massy Cedex, France, is now introducing its new CARIBOU real-time simulation engine, which replaces the 200-MHz TMS320C6201 device with a single Altera® APEXTM device. This APEX device offers a 100% increase in computing power.
A Typical DSP Job
In DSP-based simulations, the system architecture is based on a real-time unit (RTU) with a PCI interface plugged into a multiprocessor PC (Windows NT). The first DSP-based RTU had a multiprocessor 320C40 board (see Figure 1), which evolved into a single 320C6 board.
Figure 1. Former C40 Multiprocessor Board
Nevertheless, drawbacks of DSP sets the following system-wide limitations:
- High price of DSPs and associated circuits
- Need for a very detailed code optimization (assembly level) to get full performance of parallel computing (Software was written in C for portability, but optimization was difficult.)
- Speed limitation due to memory architecture
Using an APEX Device: The CARIBOU Project
The first phase of replacing a DSP-based system is to transfer the C core algorithms for pulse processing into VHDL. Simulation in the QuartusTM II software helps to define the new system architecture.
During each 100-ms time slice, the CARIBOU architecture performs the following tasks:
- Downloads up to 800 Kbytes of raw data from the PCI interface to memory bank A or B
- Extracts from the other bank (A or B) up to 32 emitter parameters from the same amount of data
- Computes up to 50,000 pulse descriptors
- Generates up to 8 RF channel control words (amplitude or phase) for each descriptor
- Emits output data to a proprietary bus (32 bits wide) The CARIBOU system is simple: one PCI main board with one APEX device, one PCI interface chip, and two SRAM banks on two daughter boards.
Table 1 shows the CARIBOU system features.
| Table 1. CARIBOU System | |
|
Feature
|
Description
|
| APEX devices (1) |
EP20K400E EP20K600E EP20K1000E |
| APEX device usage | < 25 % |
| Clocks | 32 & 64 MHz (PLL) (2) |
| SRAMS | 8 Mbytes per bank |
| Memory | 256 Mbytes |
| Power Supplies |
5 V @ 0.9 A 3.3 V @ 1.2 A |
Notes:
(1) The basic CARIBOU system includes the EP20K400EFC672-1X device in the 672-pin ball-grid array (BGA) package.
(2) PLL: phase-locked loop
Figure 2 shows the CARIBOU printed circuit board (PCB).
Figure 2. The CARIBOU System PCB
Conclusion
Implementing the Altera APEX device not only allows OMEGA-TECHNOLOGIES S.A. to double the processing power of their new CARIBOU system, but it also reduces production costs by 40%.
Using VHDL core simulation provides programming flexibility, and system implementation is greatly simplified: no boot ROMs, no loader codes, and no power-greedy digital signal processors. The new CARIBOU system shows that using an APEX device for high-end signal processing is faster and much more flexible than classical DSP-based simulation.
About Omega-Technologies S.A.
OMEGA-TECHNOLOGIES S.A. is a subsidiary of THOMSON-CSF and is located in the high-tech area of Massy (20 km from Paris). The Company is developing innovative products in the frequency synthesis field and is a major player in the EW simulator business. Products range from microwave modules and digital synthesizers to radar and communications simulators, mainly in the DC to 26 GHz range.
