Data Converter Paves Way for Software Defined RF Systems

Article By : Nitin Dahad

Software defined RF enables multi-system features such as adaptive digital beamforming and MIMO modes from a single solution.

As demand for RF hardware at higher frequencies grows, the diversity of often low-volume applications will make it challenging to deliver cost-effective systems. One solution is more software-defined radio, so systems can be reconfigured to operate at different frequencies. Teledyne e2V is supporting RF software-ization to enable dynamic RF system configuration up to Ka band (27-40GHz) frequencies.

With its new EV12DD700 dual-channel DACs, Teledyne e2v said at system level, designers can now migrate more RF hardware to digital code in the transmit path. Its reconfigurability enables generation of signals around any carrier frequency directly from a digital configuration, without the need to switch a local oscillator frequency as in traditional heterodyne architectures. The RF signal path is optimized without the need of up-converter block to reach such high frequencies.

By moving the data conversion and ‘digital harness’ closer to the antenna, it believes it can meet the demand for multi-purpose RF systems using the same hardware reconfigurable to work as a datalink modem or as imaging radars or for other services across a broader range of frequencies.

Speaking recently at an online press briefing from Grenoble, France, Nicolas Chantier, marketing director at Teledyne e2V, said, “There is a growing need to migrate RF systems from being heavily hardware dependent to following a more software-centric structure, thereby making them much easier and quicker to configure. It’s now becoming clear that the Ka-band is going to be where much of this activity occurs. Through the EV12DD700, and its support for higher frequency levels, it will be possible for engineers to replace a much larger proportion of RF hardware with digital code, and our evaluation kit will give them a useful head-start.”

Predominantly targeting mission-critical microwave systems, these devices support beamforming applications. They have a 25GHz output bandwidth with only 3dB attenuation and can go beyond this with just a little over 3dB attenuation. Built into each DAC is an array of sophisticated signal processing functionality, encompassing a programmable anti-sinc filter and direct digital synthesis (DDS) capabilities, as well as a programmable complex mixer. Also included is a digital up-converter (with four interpolation stages, plus sinc compensation).

Teledyne e2v LEO satellite use cases chart
A single system could enable future flexible satellite constellations from a single system using RF softwarization (Image: Teledyne e2v)

Chantier cited examples such as low earth orbit (LEO) satellite constellations, in which a single system could meet multiple service requirements requiring different frequency bands. The digital architectures could enable features such as adaptive digital beamforming, space-time adaptive processing as well as MIMO operation modes. He added there would be a race in the industry to enable more and more RF softwarization.

Future implementations from Teledyne e2v would integrate data conversion technology within the FPGA for centralized signal processing; it will also enable data converters to be located at antenna level with digitized RF on fiber instead of analog RF on coaxial cables, synchronized for advanced digital beamforming.

Teledyne e2V digital RF harness
Distributed data conversion (right) compared to current implementations (left) or centralized data conversion (center) enables a completely digital harness with several potential benefits (Image: Teledyne e2v)

The EV12DD700 reconfigurability is enabled in a couple of ways. First, interpolation factors can be applied to reduce the overall data rate and reduce the number of high-speed serial lanes (HSSL). This is of a particular interest in large channel count systems such as digital phased arrays to connect a maximum number of DACs to one single FPGA and optimize the logic resource usage associated to the serial interface the company said ESIstream protocol.

Second, the company said innovative functions are available to control amplitude, phase delays and frequency in the digital data path. These are digital beamforming, beam-hopping and very fast frequency hopping functionalities. The DUC is a complex mixer that translates baseband I/Q signal to digital LO frequency, thanks to a programmable 32-bit NCO (numerically controlled oscillator).

The company expects to be sampling product later this year. Via the EV12DD700 evaluation kit, engineers will have the opportunity to investigate the key operational parameters of the 12.5GSamples/s EV12DD700, ahead of the full production release later this year. This means they can assess its validity in respect to their particular design criteria early on.

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