Continue to Site

# What is the advantage of using Harmonic Balance solver when compared to Transient solver in ADS?

#### mwlab

##### Newbie
Hello,
I am performing a simulation of a half wave rectifier (HWR) in ADS. I had developed a MATLAB code for Harmonic balance solver and Transient solver in MATLAB. The code gives comparable results when compared with ADS. After understanding the internal workings of both algorithms, I am having the following question.

The harmonic balance expresses the periodic signal as sum of sinusoids (using Fourier series) with KCL getting satisfied for the linear and nonlinear part of the circuit at each node. HB gives the steady state response of the circuit. The transient solver on the other hand reaches the steady state and will contain all the harmonics, instead of a subset of harmonics that will approximate the node voltages. So, what exactly is the advantage in using HB solver when compared to the Transient solver? Is it the speed at which the steady state solution of the circuit can be reached?

#### BigBoss

HB Simulation is a subset of transient but it's much faster because HB does not calculate ALL nodes' voltages and branches' currents in a circuit at every time step. When the circuit is settled down ( transient regime ended ) it computes all nodes' voltages and branches' currents at sampling points then applies a FFT to find spectral illustrations.
Transient simulation computes all voltages and currents for ALL time step.
This is the difference.

#### volker@muehlhaus

For RF we might have a range of very different frequencies in simulation.

Imagine you want to simulate a mixer that operates at 10GHz with 1kHz IF frequency. In transient analysis, that will require many small timesteps (to sample 10 GHz) over a very long period (to sample 1kHz). Harmonic Balance is more efficient in these cases.

#### mwlab

##### Newbie
For RF we might have a range of very different frequencies in simulation.

Imagine you want to simulate a mixer that operates at 10GHz with 1kHz IF frequency. In transient analysis, that will require many small timesteps (to sample 10 GHz) over a very long period (to sample 1kHz). Harmonic Balance is more efficient in these cases.
Thank you, for your reply. So basically HB is used for the speed at which a steady state solution can be reached.