Modems

I’m working on a series of articles on modems. It’ll be a loose collection of posts, and not a true multi-part article such as the one on tomography. Modem technology is not widely known and/or understood, even by a technical audience. However…

Tom Wed, 02/13/2019 - 10:52
How Does Phase-Shift Keying Modulation Work?

Figure 3. BPSK-modulated carrier.

After explaining how amplitude modulation and frequency modulation work, which are both analog modulation schemes, I’d now like to give an example of a digital modulation techique. A basic, but very relevant, example of a digital modulation scheme is…

Tom Sat, 01/12/2019 - 16:07

ASTRA Toolbox Tutorial: Reconstruction from Projection Images, Part 2

Figure 1. Central slice of the reconstructed object.

This is part two of a tutorial that describes how to use the ASTRA Toolbox to create a 3D reconstruction from 2D projection images that were taken with a cone-beam CT scanner. In this second part, I’ll create a reconstruction from the synthetic dataset that…

Submitted on 22 October 2018
Applying a Filter in Both Directions Makes it Zero Phase

Figure 2. Block pulse filtered in both directions.

I’d like to add another trick to your digital filter toolbox: when you apply any filter in both directions on your input signal, the combined filtering operation is zero phase. As you know from…

Tom Mon, 04/23/2018 - 10:23