Accelerating ASTRO SDR Carrier Board Design with Cadence Visual System Simulator

The Slipstream Design ASTRO Ecosystem platform provides a software-defined radio (SDR) architecture based on direct RF sampling for systems that require wide instantaneous bandwidth, channel scalability, and reconfigurable signal processing. By moving frequency conversion and waveform-dependent functions closer to the digital domain, the architecture reduces reliance on fixed analog signal-conditioning chains, enabling a common hardware platform that supports multiple operating modes. This approach is particularly relevant for radar, tactical communications, signals intelligence, and aerospace systems, where changes in waveform, frequency plan, channel count, or processing function can materially affect the hardware implementation.

ASTRO for high-bandwidth Software Defined Radio (SDR), radar, RF beamforming, and multi-channel RF capture applications.

Slipstream Design designed its ASTRO system around an AMD UltraScale+ RF-SoC device, integrating high-speed data converters, programmable logic, and embedded processing within a single processing element. With this architecture, RF signals can be digitized or synthesized directly by the RF-SoC converter, while application-specific RF front-end modules provide the frequency translation, filtering, amplification, and interface circuitry required for a given deployment. The resulting partition separates the reusable digital processing base from the frequency- and application-dependent RF hardware. This blog looks at the design flow and system-level tradeoffs associated with implementing such an RFSoC-based direct-sampling SDR platform using Cadence Visual System Simulator (VSS).

Engineering Challenges: From RF Front-End to Digital Domain 

To deliver the necessary ultra-low SWaP-C (Size, Weight, Power, and Cost) for the targeted applications, the engineering team had to account for converter performance, digital signal-processing requirements, RF front-end behavior, interconnect parasitics, thermal constraints, and mechanical form factor. The ASTRO implementation illustrates several of these considerations, including multi-channel transmit and receive operation, modular RF front-end attachment, and the use of high-density board-to-board and RF interconnects between the RF-SoC processing base and plug-in RF modules.

Throughout the ASTRO product development, Slipstream Design used Cadence VSS and Microwave Office to address key challenges across both RF and digital domains. RF design challenges ranged from achieving the required gain flatness and filter precision across the ultra-wideband transmit/receive chains to managing the efficiency and linearity of the low-power RF front ends while maintaining high bandwidth.

Using Cadence VSS System-Level Analysis Before Hardware Design

For these design challenges, Slipstream Design has relied on Cadence RF system design software for over 15 years, using Cadence software throughout the full design lifecycle—from early architecture to validation. 

In the early stages of their design cycle, Slipstream Design engineers perform link budget analysis to evaluate system linearity metrics such as BER and EVM and to identify spurious signals resulting from nonlinear interactions across the signal chain.

Cadence VSS system-level schematic.

Cadence VSS plays a critical role in modeling complete RF and digital communication systems using behavioral blocks to simulate cascaded RF chains, including gain, noise figure, and distortion. To manage the low-power specifications of the RF front ends while maintaining high bandwidth, VSS and Microwave Office are used to study the impact of system architecture and individual component performance on conflicting parameters such as noise, linearity, gain, and power consumption.

Across the RF and digital domains, the direct RF sampling calls for analysis of the ADC and DAC performance using different Nyquist zones and modeling techniques. VSS features advanced ADC models that accept continuous-time RF signals and quantize them based on user-defined dynamic ranges and bit resolutions. This dynamically handles the frequency folding (under sampling) process required for direct RF sampling.

By synchronizing RF channels across multiple waveforms, the ASTRO ecosystem enables the deployment of advanced phased array systems and adaptive digital beamforming or spatial filtering techniques. This allows users to dynamically steer and shape radar beams with high precision, improving target detection, tracking, and interference rejection in real time. 

As a result, operators benefit from greater situational awareness, increased radar sensitivity and resolution, and enhanced performance in cluttered or contested environments, which are critical for mission safety and success. VSS supports phased array and beamforming simulations, enabling designers to evaluate antenna performance and multi-element synchronization—critical for ASTRO’s use cases. This allows Slipstream Design to create a system-level model of the RF chain early in the design process, de-risking architecture decisions before committing to hardware. 

From Simulation to Silicon: Closing the Loop 

One of the most compelling aspects of Slipstream Designs’s workflow is the tight loop between simulation and measurement.  With Cadence EDA software, Slipstream Design consistently delivers close correlation between simulated and measured results, allowing for fast iteration and targeted design optimization. This aligns with the strength of Cadence’s intelligent system design initiative, which integrates system, circuit, and EM simulation into a unified workflow—reducing design iterations and accelerating time to market.  

By combining early system-level exploration in Cadence VSS with detailed RF design in Microwave Office and continuous correlation to measured hardware, Slipstream Design was able to reduce risk across the ASTRO SDR carrier board development cycle. The result is a flexible, direct-sampling platform that can adapt to evolving mission requirements while maintaining the performance, scalability, and SWaP-C advantages demanded by next-generation radar, communications, and aerospace systems. For engineering teams developing complex RFSoC-based SDR architectures, this workflow shows how integrated RF system simulation can accelerate design confidence from concept through deployment.

Video interview: Philip Wilson, Managing Director at Slipstream Design, explains how the team uses Cadence AWR software and Visual System Simulator (VSS) to model complete RF-to-digital systems, overcoming complex RF and digital design challenges while accelerating innovation in communications, radar, and signal intelligence applications.