LISN-mate for a dual channel DC LISN
This design is for a “LISN mate”, suitable for a dual channel LISN. In particular, it was designed for the dual DC LISN published in Elektor (part 1 in the Sept./Oct. 2021 issue, part 2 in the Nov./Dec. 2021 issue), and which is available from the “elektorstore”. as a kit.
A LISN lets you test the conducted emissions in power cables. If the emissions exceed the limit, and you need to adjust the design to reduce the RF noise, the first thing you will want to know is, whether the noise is “common mode” or “differential mode”. The LISN-mate is a tool that tells you that.
When you want a quantitative value for the common mode noise and/or the differential mode noise, a LISN-mate is actually somewhat involved. However, for the qualitative answer of whether emissions are primarily either common more or differential mode, all it takes is a transformer (suitable for the frequency range).
The design is in KiCAD. Gerber files for the PCB are provided as well. The components are:
|RF Transformer 50 Ohm, 30 kHz - 125 MHz
|SMA receptable, edge-mount
|copper foil, 0.1 mm thick
The case is 3D printed; an STL file is provided. The design is in OpenSCAD (and the design source file is provided as well). Since the case is in plastic, and therefore not shielded, I added a shield from copper foil over the entire top of the PCB. It is soldered onto the SMA connectors. (The bottom of the PCB is an uninterrupted ground plane over the entire surface.)
The LISN-mate is distributed under the CC BY-NC-SA 4.0 license (Attribution-NonCommercial-ShareAlike 4.0 International). All files are available from the GitHub project (see the link below).
For the 3D printed case, this project uses the Chamfered primitives for OpenSCAD v1.2 by TimeWaster, which is published under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 licence.
|3D printed case on Printables.com