Circuit Simulation Some humbling thoughts… Manfred Wendt Fermilab

Manfred Wendt, Fermilab/AD-Instrumentation 2 Nov. 30, 2006 Circuit Simulation: For What? Typical beam instrument, e.g. BPM, toroid, WCM, PMT, etc. Analog Signal Processing ADCADC Digital Signal Processing Clock & Trigger Distribution DAQ & LAN Interface Beam Pickup Detector Analog DomainDigital Domain

Manfred Wendt, Fermilab/AD-Instrumentation 3 Nov. 30, 2006 Circuit Simulation Domains –Digital signal simulation is mostly based on vendor supplied simulators (e.g. Quartex II, etc.). –No model data is available for most complex semiconductors (ADC, DAC, T&H amps, limiters, many – if not most - analog parts). +Circuit simulation may still be useful for critical sections and subsystems:  Gain stages  Passive sections (filters, diplexers, hybrids, transmission-lines)  RF- & microwave circuits  Layout effects, cross-talk, reflections  Noise and temperature analysis  Pickup detectors (button, stripline, cavity & other monitors  High-speed digital I/O (CLK distribution, PECL & LVDL circuits, single-ended to differential transition)

Manfred Wendt, Fermilab/AD-Instrumentation 4 Nov. 30, 2006 Circuit Simulator Software  “Brainware”  Pencil and paper  Apply Kirchhoff and Ohm’s law for a simple, idealized subcircuit.  Analytic result! Limited to linear circuits.  Freeware  Berkley SPICE and variants (google “free spice simulator”).  Student versions, often limited.  Simulators for special purposes.  $$$ware  Schematic entry  Combined with layout system, or add-on to layout system.  Design suites, including various circuit and EM simulators.

Manfred Wendt, Fermilab/AD-Instrumentation 5 Nov. 30, 2006 Capabilities and Characteristics  Circuit simulators can  Fully analyze the circuit (based on the models).  Have sometimes (often limited) synthesis capabilities.  Numerical solution of the circuit topology  Circuit elements  Lumped elements based on ideal models  Distributed elements based on analytic solutions or approximations of the EM problem  Nonlinearities, noise & temperature and other effects may be included in some models  User specified (analytical) models and sources.

Manfred Wendt, Fermilab/AD-Instrumentation 6 Nov. 30, 2006 Circuit Simulator Types  Linear Solvers:  DC, AC, S-parameter, etc.  Frequency domain solution in steady state  Nonlinear Solvers (e.g. Harmonic Balance):  Small signal analysis around the working point.  Spectral, distortion and other characterization of the frequency harmonics.  Transient Solvers (e.g. SPICE):  Approximate solution of the system of differential equations  Time domain approach includes all transient effects and initial values.  Special Solvers:  Analytic circuit analysis, EM solvers, circuit synthesis, etc.

Manfred Wendt, Fermilab/AD-Instrumentation 7 Nov. 30, 2006 Simulation Examples Fermilab Main Injector BPM Upgrade Project

Manfred Wendt, Fermilab/AD-Instrumentation 8 Nov. 30, 2006 Simulation Examples (cont.) MI BPM Analog Signal Processing Entire input section 2.Absorptive low-pass 3.Diplexer

Manfred Wendt, Fermilab/AD-Instrumentation 9 Nov. 30, 2006 Simulation Examples (cont.) MI BPM Analog Circuit (1 ch., 2.5 & 53 MHz)