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Using Review to Extract KPIs

By Chloe Allison 10 October 2019

In this article, we will discuss the different Key Performance Indicators for devices and how these can be extracted in OnScale using Review.

What is a KPI?

In engineering, a Key Performance Indicator (KPI) is a measurement of performance to evaluate the success of a design. These KPIs are analysed to achieve optimal performance of a device. For example, in Micro-Electro-Mechanical Systems (MEMs) an engineer would aim to create a design which maximises the quality factor and coupling coefficient whilst keeping operations in a certain frequency bandwidth. A device’s KPIs differ depending on the application but many are common to lot of applications such S-parameters, Bandwidth, Resonance Modes, Quality Factor etc. All these metrics can be calculated in OnScale using Review.

What is Review?

Review is a useful post-processing language in OnScale which allows users to write personalized scripts to calculate their designs’ KPIs. In Review, users can mathematically manipulate data, plot it and save it. Review uses commands which can be found in the Command Reference. These scripts have the file extension *.revinp.

Figure 1: Example of how to save review script


Find out more about Review in our Help Center here!

Reading and Plotting Data

To read in data from OnScale outputs you must use the read command.

Figure 2: Reading + plotting code (Left) Plotted time record (right)

This code reads in all the records from a history file *.flxhst (which contains time-domain signals) and plots the first record. The read command defines a local file name for an external file so you can access its contents, in this example we will access PZT_2D.flxhst using the name f1. There are multiple records in the history file so in the plot command we must specify which record to plot. If we look inside the history file, the first record is the time function.

Figure 3: PZT_2D.flxhst contents

Manipulating Data

Once data has been read in, there are a wide range of commands that can be used to manipulate the data. A commonly used method is the Fast Fourier Transform (FTT) which transforms time-domain data into frequency-domain data.

Figure 4: Code to get FFT of the time function (Left) Plotted FFT curve (Right)

This code creates a new local file name to store the FFT of the time function f2 and then takes the FFT of the time function which is the first record in f1. Mathematical operations can also be applied using the make command.

Figure 5: Code to double amplitude of time function (Left) Plotted result (Right)

The curv command creates a new data curve and adds it to the curves contained in f3. Multiple curves can be added to a local file and must be accessed in order.

Save Data

Any new local files that users create in review can be saved as txt files.

Figure 6: Code to write data to text file (Left) Text file data (Right)

Keep reading if you want access to some basic Review templates for some KPIs.

Quality Factor

Figure 7: Conductance plot

Quality Factor (Q Factor) is a measure of efficiency and is the ratio between the centre frequency and the half conductance bandwidth.

Figure 8: Quality factor equation

It is very simple to calculate Quality Factor in Review.

  • Calculate conductance using freq command
  • Calculate f0 using symb #get { } curvmax
  • Calculate f0 / 2
  • Calculate f2 and f1 using symb #get { } curvcros
  • Calculate f0 / (f2 – f1)

Click here to download our template Review file for Quality Factor!


Figure 9: Two-port S-parameter diagram

Scattering parameters (S-parameters) represent the way power propagate through an electrical network. High frequency linear networks can be fully characterized by these parameters which are measured at the ports of the network. Two-port S-Parameters can be calculated in Review using the template here!


Figure 10: TVR graph (Left) OVC Graph (Right)

Sensitivity characterises the minimum power of a signal to be transmitted or received successfully.

Transmit and receive sensitivity can be calculate in OnScale using the Review template provided here!


KPIs are important in engineering design and can be extracted from your OnScale simulations using the simple post-processing language, Review. If you would like a template for any of the following KPIs, get in touch with our team through our forum.

  • Bandwidth
  • Crosstalk
  • Beam Profile
  • Beam Pattern
  • Coupling Coefficient


Chloe Allison
Chloe Allison

Chloe Allison is an Application Engineer at OnScale. She received her MA in Electrical and Electronics Engineering from the University of Strathclyde. As part of our engineering team Chloe assists with developing applications, improving our existing software and providing technical support to our customers.