FEATURE INTEGRATED CIRCUITS


GETTING TO THE CORE OF RADIO FREQUENCIES


As digital radio frequency modules (DRFM) become normalised, with digitisation taking itself to the forefront of contemporary electronics design, Logic-X and Teledyne e2v collaborate on an FPGA mezzanine card that looks to simplify the design of DRFM systems. Erik Barhorst, managing director, Logic-X, divulges the details


I


n order to build a high end radar jammer system or digital radio frequency memory (DRFM), one has to rely on many different types of advanced electronics. In a DRFM system, the radio frequency (RF) signal is received at the antenna, at the front end, which feeds into analogue circuitry that converts the frequency band of interest down to a more palatable frequency. This down converted signal is then digitised and processed by a computer system that modifies the RF signal, before coherently rebroadcasting it through the antenna. An important part of the DRFM system


is the analogue RF signal conditioning: it has traditionally been relying on analogue mixers, in combination with analogue to digital converters (ADC) and digital to analogue converters (DAC). Mixing steps translates the signal from its original frequency to the desired band. Classical architectures on RF systems use at least one intermediate frequency (IF) between baseband and the final carrier. This scheme applies to both


transmission and reception paths, and the process will be carried out as an upconversion or a downconversion respectively. Over the last decade, the


way we are building DRFM systems has been changing drastically, thanks to the emergence of high speed AD converters, DA converters and multi-processor system on chip (MPSOC) devices. The MPSOC devices combine advanced FPGA fabric with multiple CPU elements. With a wideband ADC and DAC, one can replace a subsystem of mixers, LO synthesizers, intermediate frequency amplifiers and filters. The MPSOC system replaces the combination of separate FPGA and processors, often spread over multiple cards. As such, these new technologies allow a DRFM system to reduce in size, weight, power and cost. Further enhancements of DRFM


systems will be possible thanks to the collaboration of Teledyne E2V and Logic-X. Both companies are collaborating on the design and development of an FPGA mezzanine card (FMC) that incorporates two of the latest converter chips from Teledyne e2v: the EV12DS460A and the EV12AS350B. Defining these chips, the EV12DS460A DAC provides an analogue bandwidth extending beyond 7GHz, facilitating multi-band, direct digital synthesis up to K-band (26.5GHz), with a short latency


of three clock cycles. The EV12AS350B is set to be a 12-bit resolution ADC on the market that combines signal digitisation at 5.4GSps, input bandwidth in excess of 4.8GHz and latency as low as 26 clock cycles with a noise floor of -150dBm/Hz. With these two products, Logic-X designs the LXD30000 with an analogue stage that has a wide input -3dB bandwidth above 4.8GHz, and the low latency 5.4GSps ADC (EV12AS350B). With this device, the FMC delivers a strong performance with regards to SFDR, close in phase noise and latency (4.8ns). Sampling at 5.4GSps, it offers a bandwidth of 2.7GHz. Surpassing the analogue input, the analogue output on the FMC offers an even lower latency (0.6ns) using the EV12DS460A DAC device. The output passband is from 0.5MHz to 7GHz and the instantaneous output bandwidth is 1.35GHz. Both the ADC and DAC offer 12-bits of resolution, further contributing to achieve best in class signal to noise ratios. The great thing about the combination


Upconversion and


downconversion frequency mixing diagrams


of these two converter devices on a single FMC card is that it allows easy upgrades to existing DRFM systems that are already using an FMC card for their analogue receivers and transmitters. By replacing their current FMC card with the LXD30000, system designers increase the resolution of their system without a complete board or system redesign. Likewise, this FMC card is a great choice for new system and board designs, as it allows for easy upgrades of these systems when new converter technology becomes available.


Logic-X www.logic-x.eu 32 SEPTEMBER 2019 | ELECTRONICS / ELECTRONICS


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