Down conversion is an essential part of many complex signal processing operations us and the process is usually too computationally intensive for
software to handle in real time while its mathematical complexity makes implementing it from scratch in hardware far from straightforward.
RF Engines Limited (Isle of Wight, UK) has extended the range of its digital down converter (DDC) technology so that it can now process up to 1 GHz of bandwidth (2Gsps ADC rate) input and provide a narrower band output.
The wideband DDC core is optimized for size and speed, on a range of Xilinx or Altera FPGA devices. The technology can operate with fixed frequencies and bandwidths or be fully flexible as required.
With options like fractional re-sampling for arbitrary output bandwidth selection and the ability to implement the design in either logic-rich or DSP-rich FPGA architectures, the RFEL wideband DDC is suitable for a variety of applications.
Being FPGA-based, they can be tailored to meet particular processing and interface requirements, such as input/output format, number of channels, tuning resolution, rate change resolution, dynamic range and filter shape. Selectable filters and non-integer sample rate conversion factors can also be supported.
One of the main application areas is for electronic surveillance in military digital receivers, where this approach enables a desired signal band to be extracted from a wide slice of the spectrum in order that further analysis of the signal content can be carried out.
For example a radar warning receiver can rapidly spot the signal ‘signature’ of an incoming missile or other threat, and the downconverter will extract the specific signal and measure its parameters.
In scientific applications, for example in the latest radio telescopes, this approach allows very wide sections of the spectrum to be monitored at one time, in order to acquire weak or hidden signals.
RFEL has already completed several custom projects for customers which use different variants of the wideband DDC core.
RFEL is currently engaged to research DDC designs in the +10GHz range. It also plans to release a demodulation core in a few months.