Analogue, digital and power in one connector

30 April 2024 Interconnection

In a recent white paper titled ‘Array Connectors for Mixed Signal Multi-Channel RFSoCs up to 8 GHz’, Samtec engineers described the research, development, simulation, and measurements performed in a project to design the optimal breakout region (BOR) for the use of array connectors that simultaneously carry analogue, digital, and power signals in an RF environment, as a replacement for traditional compression mount and threaded PCB connectors. The results showed that it is possible to route high-frequency, high-isolation RF signals and digital and power signals through a single connector.

System on Chip (SoC) implementations with integrated data converters, and RF front-end subsystems are being deployed in 5G/6G, phased array radar, SATCOM, FPGA cards, and test and measurement architectures. The use of these RFSoCs challenges the traditional approach of handling the RF signals with compression mount and threaded PCB connectors. A simple alternative, using multiple ganged connectors, still puts strain on form factor, weight, and financial budgets, especially as high-frequency RF channel counts increase in these SoC-based systems.

The first step of this research and development project was simple, as Samtec already had existing array connectors for high-performance, high-speed digital signalling. Adapting this technology for RF applications required the development of specific PCB stack ups and launch optimisations to achieve the differential crosstalk and return loss performance required for frequencies up to 8 GHz and beyond.

The design targets identified for this mixed-signal connector array project were based on the specifications from existing RFSoCs, such as the AMD Xilinx Zynq and included:

• 8 GHz bandwidth.

• 50 Ω system impedance for single-ended; 100 Ω for differential.

• Return loss of -12 dB up to 4 GHz, -10 dB up to 8 GHz.

• Crosstalk isolation between channels: -69 dBc to 4 GHz, -63 dBc to 8 GHz.

This work took an unconventional approach to an optimised breakout design in terms of materials, launch, connector pin field, and differential ground pattern. Because of that, a currently available 560-pin single array connector can support up to 26 differential RF signals.


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