CASE STUDY SNAPSHOT
Customer : Leading German Defense OEMSize : >200-1000
Project vertical : Defense & Aerospace, RF Systems
Challenge : Modernize a legacy RF control system, ensuring 100% compatibility with existing RS422 protocols while adding modern Ethernet/web-based configuration and maintenance.
Solution : A custom, three-board solution centered on a Xilinx Artix-7 FPGA, running a MicroBlaze soft processor, RTOS, and a full software stack to manage RF switches and attenuators.
Services & Products Availed : Custom Hardware Design, FPGA Design, Embedded Software Development (RTOS, Drivers, Application), Web Server Development
Tools and Technologies :
- Key Hardware: Xilinx Artix-7 FPGA (XC7A100T), DDR3 RAM, QSPI Flash, RS422 Transceiver, Gigabit Ethernet PHY, PT100 Temperature Sensor.
- Software Development: C, VHDL/Verilog (implied).
- Frameworks: MicroBlaze Soft Processor, RTOS, LwIP (Lightweight TCP/IP) Stack, HTTP Web Server.
Introduction
Embien partnered with a leading German defence OEM to engineer a sophisticated FPGA-based AFE controller for a mission-critical Antenna Front-End (AFE) unit. The primary goal was to develop a modern, robust, and reliable system to manage complex RF signal paths, replacing a legacy component while ensuring 100% backward compatibility with their existing infrastructure.
The Challenge: Bridging Legacy and Modern Systems
The customer's core challenge was to modernize the "brains" of their AFE system. This controller was responsible for managing a complex array of RF switches (multiple SP4T and SP3T) and Digital Control Attenuators (DCAs) to accurately route and condition signals across a wide frequency spectrum (0.5-40GHz). The new system had to satisfy several competing constraints. It absolutely had to interface with the existing master controller via a legacy RS422 protocol, precisely decoding its specific 49-bit command format.Simultaneously, the customer wanted a modern interface (Ethernet) for configuration, status monitoring, and secure in field firmware updates, a feature impossible with the old system. This all had to be achieved on an industrial grade platform built for the high reliability, rugged environment of a defense application.
The Solution: A Custom FPGA-based AFE System from the Ground Up
Embien’s team designed and developed a complete, turnkey solution, encompassing hardware, FPGA logic, and a full embedded software stack. The architecture was a clean, three-board design: a Power Module, the RF Card (with the customer's RF components), and Embien's custom FPGA Controller Board.
Custom Hardware Design
The heart of the solution is the FPGA-based AFE controller board, architected for performance and reliability:
We selected a Xilinx Artix-7 FPGA (XC7A100T), an industrial-grade part with over 101,000 logic cells. This provided ample resources to not only implement all control logic but also to embed a powerful MicroBlaze 32-bit soft processor. This key decision transformed the FPGA from a simple logic device into a complete system-on-a-chip (SoC). The board includes 2Gb of DDR3 RAM for the MicroBlaze application, 256Mb of QSPI Flash for the FPGA's configuration bitstream, and an additional 1Gb of QSPI Flash for onboard storage—used to hold the web server pages, application data, and multiple firmware images.
A robust power architecture was designed to take a 5V input and efficiently convert it to all necessary voltage rails (1.0V, 1.2V, 1.5V, 1.8V, and 3.3V) required by the FPGA, DDR3 RAM, and peripherals.
Connectivity & Interfaces
Embien enabled following key interfaces.
RF Control: A high-speed, high-density connector provides dozens of 3.3V TTL GPIOs for direct, high-speed control of all the switches (SP3T, SP4T) and DCAs on the RF card.
Legacy Interface: An isolated RS422 serial interface (using a MAX3461ESD+ transceiver) was implemented for communication with the customer's existing master controller.
Ethernet Interface: A Gigabit Ethernet PHY (KSZ9031RNXIC) provides a 10/100/1000 Mbps network interface for the web server.
Monitoring & Debug: The board features a debug UART (RS232), a standard JTAG connector for programming, and an external ADC connected to a PT100 RTD sensor for precise ambient temperature monitoring.
Embedded Software & FPGA Logic
With the hardware platform defined, our software team built a complete, multitasking application to manage the system.
An RTOS (Real-Time Operating System) was integrated to manage all system tasks concurrently. This ensures that high-priority tasks, like processing an incoming RS422 command, are never delayed by lower-priority background tasks, like handling a web server request.
Embien developed a complete Hardware Abstraction Layer (HAL) and all necessary low-level drivers for the MicroBlaze processor. This included drivers for GPIO, RS422/UART, Ethernet (integrated with the LwIP TCP/IP stack), ADC, and QSPI Flash.
A dedicated, high-priority RTOS task continuously monitors the custom RS422 interface imeplemented on FPGA. When a valid 49-bit command packet is received, it is immediately parsed to extract the precise settings for all 5 DCAs and 3 switches. The application then references internal truth tables (as specified in the design) to set the corresponding GPIOs, correctly configuring the RF signal path in real-time.
An HTTP server runs on the LwIP stack, serving a user-friendly web interface stored in the onboard flash. This GUI allows technicians to:
Configure Device: View and set system parameters such as Device ID, RS422 baud rate, and operational modes.
Perform Firmware Upgrades: Securely upload a new firmware file via the browser. The system includes a bootloader that validates the new image, programs it to the application region of the flash, and reboots the system, enabling simple and safe in-field maintenance.
Safety & Monitoring: Another RTOS task periodically reads the temperature from the ADC. If the ambient temperature exceeds a critical threshold (e.g., 125°C), the system triggers an emergency shutdown, turning off power to the RF card to protect the high-value, sensitive components.
The system features a state-based startup sequence. On power-up, it initializes all drivers, waits for a specific "Power Enable" command via RS422 (to ensure compatibility with the master system's boot process), and only then powers up the RF sub-modules and enters its main operational state.
Benefits of the Embien Solution
Seamless Legacy Integration: Created a 100% compatible "drop-in" replacement FPGA-Based AFE Controller that understood the legacy RS422 protocol, preserving the customer's investment in their existing master system.
Modern Maintenance & Control: Added modern network capabilities via an intuitive web interface, drastically reducing technician time for configuration, diagnostics, and updates.
Future-Proof Platform: Enabled secure, in-field firmware upgrades, future-proofing the platform and allowing for new features or patches without costly hardware recalls.
Enhanced System Reliability: Built-in, real-time temperature monitoring and an automatic emergency shutdown mechanism provide active protection for expensive RF hardware.
Powerful & Flexible Core: The Artix-7 FPGA and MicroBlaze processor provide a powerful, flexible, and scalable solution, offering far more processing headroom for future expansion than a traditional microcontroller.
Conclusion
Embien successfully delivered a custom, high-reliability FPGA-Based AFE Controller that bridged the gap between a legacy RF system and modern, network-based management. Our deep, cross-functional expertise in custom hardware design, FPGA logic, RTOS, and full-stack embedded software development allowed us to provide a complete, robust hardware and software solution for a demanding defence application. This project highlights our ability to understand complex system integration challenges and engineer a solution that delivers value, reliability, and a clear path for the future.
