aplac the rf simulator
APLAC, a program for circuit,system, and electromagnetic FDTD simulation and design, is a joint development of the Circuit Theory Laboratory of the Helsinki University of Technology, Nokia Corporation Research Center, and Nokia Mobile Phones. The main analysis modes are DC, AC, linear and nonlinear noise, transient, oscillator, multitone harmonic steady state, switched-capacitor, small-signal mixer, steady state transient, and thermal feedback. APLAC can also be used for measurements with research-488 apparatus. APLAC’s transient analysis uses convolution for correct treatment of components with frequency-dependent characteristics. Monte Carlo analysis is available in all basic analysis modes, as is sensitivity analysis in DC and AC modes. N-port Z, Y, and S parameters, as well as two-port H and noise parameters, can be used in AC analysis. APLAC also includes a versatile collection of system level blocks for the simulation and design of analog and digital communication systems as well as an electromagnetic FDTD simulator for solving 3D field problems independently or as a part of a circuit design.
In addition to familiar Spice models, a great number of microwave components (microstrip/stripline/suspended substrate microstrip) are included. System models include phase-locked loop, formula-based and discrete-time models useful in RF design. The model parameters of the components may have any functional dependency on frequency, time, temperature, or other parameter. Users can create new components by defining their static and dynamic (and possibly nonlinear) characteristics in APLAC’s interpreter-type language. Spice- and Touchstone/MDS-syntax models can be imported.
APLAC reads its input – nodes, branches and model parameters of the components – from a text file. Model libraries can be created and included. Expressions are written in a program-like manner, user functions may be defined, and complex arithmetic is included. Conditional and looping control structures are supported.
The output results from one or several sweeps of any user-defined function of the circuit parameters, time, frequency, or temperature. The results may be printed or plotted in rectangular (including 3D) or polar coordinates, or on the Smith chart. Graphics output can be directed to an EPS-, HPGL-, CSDF-, and Meta-file, or to an internal graphics file for later viewing. Graphics includes a versatile collection of postprocessing properties like automatic creation of (Monte-Carlo) histograms and Fourier-transforms as well as cutting, copying and pasting curves.
APLAC includes several optimization methods: gradient, conjugate gradient, minmax, random, simulated annealing, tuning (manual optimization) and gravity center (design centering). Any parameter in a design problem can be used as a variable and any user-defined function may act as an objective.