Software Defined Radio Made Easier
Software defined radio (SDR) requirements are starting to exceed the performance capabilities of many traditional RF components. This challenge invites RF system architects to select connectors that were originally designed to meet the demanding signal integrity specifications of high-speed digital applications.
This blog highlights some key details from a recent case study. The study explains how designers at Slipstream Engineering Design Ltd. (Slipstream) used Samtec SEARAYTM connectors with a customized PCB launch (connector to board transition) to achieve the necessary RF performance for their next-generation modular ASTROTM card for SDR. Samtec refers to this approach as Analog over ArrayTM .
Slipstream’s SDR platform includes the ASTRO card that houses a Gen 3 RFSoC and an 8T8R channel RFFE in a dual-slot PCIe form-factor. The ASTRO card uses the Samtec SEARAY connectors, and the carrier card is equipped with Samtec Magnum RF ganged connectors.
The Design
An SDR platform offers functional flexibility and adaptability through reconfigurable hardware. The Slipstream approach uses RFSoC devices that incorporate multiple RF channels in a compact PCIe and VPX form factor. Their modular approach to system design incorporates RF cards that are application and frequency specific. These cards can be plugged into the Slipstream digital hardware platform to create a customized SDR platform. The compact, multi-board, SDR platform uses a dual-slot PCIe form factor and a high-density interconnect (HDI) approach.
The figure below illustrates the ASTRO SDR platform, incorporating an 8-lane PCIe carrier card. The application specific RF Front-end (RFFE) card incorporates 8 transmit 8 receive (8T8R) channels and is designed to operate in the 5G NR N78 and N77u bands (3.4-4.2 GHz).
The ASTRO SDR platform allows for the RFFE board to be a plug-and-play module that can be swapped depending on the application of interest. In addition to the SEARAY connectors, the platform also includes Samtec Magnum RF® to route the 8 Tx/Rx signals and some clock signals to the front panel. Slipstream engineers selected the Magnum RF connectors because they are ganged and miniaturized, which is beneficial for a very small form factor, as well as for their inter-channel isolation.
Overcoming Challenges
Routing the RF signals from the RFSoC device to the RFFE board through multiple connectors while maintaining return loss and crosstalk performance was the major design challenge.
To achieve the desired functionality, a high layer-count PCB with fine track widths and microvias was required. High-density field array SEARAY connectors were used in the multi-board transitions. These Samtec connectors are traditionally used for high-speed digital signal interconnections, but, in this implementation, they route RF signals up to 6GHz.
Download the full PDF of the case study “Slipstream Design Adapts Samtec SEARAY connectors for RF Performance in SDR” to learn how the differential traces were routed, get details about the test board, PCB stackup, and simulation.
