WILSONVILLE, Ore. — Mentor Graphics Corp. will announce this week a version of its radio frequency circuit simulator, Eldo RF, that supports phase-noise analysis and larger circuit models than earlier versions of the simulator.
While Eldo is best known for operating in the time domain, Eldo RF is a harmonic balance simulator operating in the frequency domain. Cyril Descleves, product marketing manager for Eldo RF products, believes that frequency domain simulation offers the best analysis for radio frequency circuits. "Time domain simulation is too tricky," he said.
"With harmonic balance, you don't have problems with time step control and numerical integration — especially where multiple carriers are operating within a GHz of each other," Descleves said.
Eldo's harmonic balance simulator — a third-generation implementation — has built-in support for multitone analysis, it can distinguish interference and intermodulation products from legitimate carrier frequencies, and the user need not be concerned with the spacing between frequencies.
"With time domain simulation, you have a long simulation and can't tell at the end of the day whether you're looking at the noise of the circuit or signal or noise of the simulation," he said.
This may be something of a "religious war," he acknowledged. When it first appeared, the Eldo software suite was known for its speedups of Spice circuit simulation. The tool suite had a built-in partitioning algorithm that would divide a circuit into elements using feedback and demonstrating complex nodal behavior, and those functioning like switches (particularly MOS circuits).
Newton-Rafson equations were applied to the current nodes while a one-step relaxation algorithm was applied to the switches; that is, the use of complex matrix equations was avoided where the partitioner detected switch-like behavior.
As a result, Eldo could claim a 10x to100x speedup over traditional circuit simulators.
Eldo and Eldo RF are both fast transistor-level structure simulators, driven by a Spice netlist, said Descleves.
The new version of Eldo RF (2.0) includes algorithm support for the analysis of oscillators, voltage-controlled oscillators (VCOs) and frequency synthesizers, the building blocks of the RF transceivers in all wireless communications devices. The phase-noise-analysis capability, in particular, allows reliable prediction of RF IC behavior by simulating phase noise, which may reside close to the carrier. This phase-noise analysis can also be applied to frequency dividers as well as VCOs.
Eldo RF also features all standard RF measurements such as harmonic distortion, conversion gain, image rejection, feed through and isolation analysis, 1-dB compression points, intermodulation products, nth order intercept points, power-added efficiency and noise figure.
The release also supports the simulation of larger circuits, Descleves said.
