Let’s Talk Technical with Qorvo- QSPICE - Advancing RF Circuit Simulation | DigiKey

Mike Engelhardt, known for his work on LTspice, discusses the development of Qorvo’s QSPICE and how it transforms simulation for RF engineers and mixed-signal designers. Traditional SPICE tools were not always ideal for RF design, but QSPICE addresses many of these limitations. Why RF Designers Should Care • Historically, RF engineers preferred frequency-domain or harmonic balance simulators, since SPICE struggled with spurious harmonic generation. • QSPICE introduces a time-step process that quantifies low-level non-linearities accurately, making time-domain simulation a powerful tool for RF design. • Benefits include: o Simulating the real bias point and full non-linearities. o Reduced risk of errors compared to frequency-only analysis. o Better visibility into circuit behavior without oversimplifying assumptions. Time-Step Innovation • Simulation accuracy depends on time steps. • QSPICE automatically determines the minimum necessary steps to achieve user-defined accuracy. • Unlike older tools, it leverages GPU-based graphics technology to handle and plot massive datasets at high speed, allowing FFT analysis that accurately shows spurious responses and noise floors. Advantages for RF Design • Enhanced ability to separate and analyze PCB parasitics individually. • At lower frequencies (<50 MHz), PCB parasitics are minor, but above ~100 MHz they become critical. QSPICE allows engineers to model and test these effects directly. • Handles dispersion challenges, where inductance, capacitance, or magnetic behavior vary by frequency. Improved User Experience • Unlike legacy EDA tools with outdated GUIs, QSPICE focuses on workflow efficiency: o In-place text editing instead of disruptive pop-up dialogs. o Right-click menus for immediate access to relevant commands. o Fewer eye and hand movements during schematic editing. Mixed-Signal Simulation • QSPICE supports native C++ and Verilog compilation, executing code during simulation. • Offers exceptional mixed-mode performance, running digital logic at near hardware speeds. • Simple to use—engineers can drag-and-drop a code block into a schematic and run it without external compilers. Conclusion QSPICE enables RF and mixed-signal engineers to go beyond the limitations of traditional SPICE by: • Providing robust time-domain accuracy. • Offering powerful non-linear and parasitic modeling. • Streamlining usability with a modern, intuitive interface. For RF engineers tackling GHz-level challenges and mixed-signal designers needing integrated logic simulation, QSPICE represents a major step forward in circuit simulation technology.