Broadband software-defined radio satellite modem design
Client
A European company, specializing in software for the ground segment of satellite communications. It works with equipment manufacturers and providers of broadband & multimedia services.
Challenge
To design a hardware & software platform for a satellite modem. The customer decided to integrate a new hardware solution to extend its product line with the original branded solution.
Solution
We designed the device in a compact 1U form factor by dividing it into digital and analog boards. This approach helped us reach the highest flexibility: in case you want to scale the device functionality, you only need to repurpose the analog front end board.
We chose Zynq Ultrascale+ as a development platform. We used the Linux OS and the programmable logic for the functionality implementation.
Our engineers have developed a dedicated front end using high-speed ADC/DAC converters and modern high-frequency analog modulators/demodulators.
Block diagram:
We reached high-speed data exchange between server and device with the help of four 10G interfaces and the DPDK framework. Data transmission is carried out via a specially developed MCP protocol, which ensures reliable data transmission over UDP.
We used the following development tools:
- Mentor Pads for hardware design
- Vivado for FPGA firmware development
- MATLAB/Simulink for the modem and control software development.
We implemented the system model with the use of model-based design, which means the communication system full implementation in Simulink with the subsequent HDL code generation. That resulted in the following advantages:
- Rapid design and verification
- Processing several ADC sample per clock cycle (parallelization, unrolling, pre-calc)
- Smooth conversion to a fixed point
- Channel model
- BER evaluation at the design stage
Our engineers also tested new approaches to AGC implementation and analog front end calibration. We implemented the AGC subsystem in the form of a Simulink model from which the HDL code was generated.
Tools used:
- Simulink State Flow
- HDL coder
- AXI4-Lite Write Master model
Hardware blocks in the demodulator (LTC5586), DAC (DAC37J82) and ADC (ADS54J60) compensate the following effects:
- IQ imbalance in the receiving path;
- IQ imbalance in the transmission path;
- carrier leakage;
- group delay.
The Surrogate optimization method was used for figuring out optimal parameters in the specified operation mode. Chip registers served as parameter space. The target functions were: suppression of the mirror channel TX & RX and that one of the carrier channels.
To configure the device and measure the signal parameters, we developed a graphic application.
Business value
The customer received a satellite modem with the following features:
- frequency range: 300 MHz – 2 GHz; bandwidth:
- up to 500 MHz;
- ZERO-IF scheme;
- Two receiving paths (ADC 1Gsps) and one transmitting path (1xDAC 1.5Gsps);
- 4 х 10G Ethernet for data transmission;
- Zynq Ultrascale+ platform.
Supported operating modes:
- PSK, QAM-manipulations.
- LDPC and convolutional error correction codes.
