Hi,
In the testing of the a CM/DM Noise Separator I designed, I needed to test a frequencies lower than the HP34677A S-parameter Test Set. The S-parameter is designed to work down 100kHz.
I found that HP also produced the 35676A Reflection Transmission Test Set. The R/T Test Set will work down to 5Hz.
You can buy the R/T Test Set on the usual places for about $300-500.
Note: The 'B' Version is not an improvement on the A version, the A is 50
![Ohms \$\Omega\$](https://www.eevblog.com/forum/Smileys/default/omega.gif)
and the B is 75
![Ohms \$\Omega\$](https://www.eevblog.com/forum/Smileys/default/omega.gif)
.
Information SearchI found a nice summary of the 35676A:
Link:
http://www.hparchive.com/Manuals/HP-35676-SCHEMATIC.pdfI will attach a copy of the document to the end of this message.
I looks to be a pretty simple circuit, just 7 resistors and four connectors. Most of the challenges are in mechanical construction.
SchematicI entered the schematic into KICAD. The test points are connected to the chassis mounted connectors.
PCB Design ![Cloning the HP35676A Reflection Transmission Test Set for the 3577A/B VNA](https://www.eevblog.com/forum/index.php?action=dlattach;topic=246486.0;attach=1019308;image)
The coplanar Wave Guides are 50
![Ohms \$\Omega\$](https://www.eevblog.com/forum/Smileys/default/omega.gif)
.
Complete Project![Cloning the HP35676A Reflection Transmission Test Set for the 3577A/B VNA](https://www.eevblog.com/forum/index.php?action=dlattach;topic=246486.0;attach=1019312;image)
Here is a picture showing the circuit board mounted inside a Hammond 1550P Diecast box.
Mechanical Design
The mechanical design was done using Fusion 360. I started with a simplified drawing of the HP3577A front panel:
![Cloning the HP35676A Reflection Transmission Test Set for the 3577A/B VNA](https://www.eevblog.com/forum/index.php?action=dlattach;topic=246486.0;attach=1019316;image)
I downloaded the STEP file for the Hammond 1550P box and added the holes for the connectors and the PCB:
![Cloning the HP35676A Reflection Transmission Test Set for the 3577A/B VNA](https://www.eevblog.com/forum/index.php?action=dlattach;topic=246486.0;attach=1019320;image)
Here is a picture showing the assembly:
![Cloning the HP35676A Reflection Transmission Test Set for the 3577A/B VNA](https://www.eevblog.com/forum/index.php?action=dlattach;topic=246486.0;attach=1019324;image)
and the project installed on the HP3577A:
TestingAfter installation I did the one port full calibration with Open, Short and Load.
At high frequencies the results agreed with my S-parameter Test Set. At lower frequencies the R/T Test Set produced the expected results.
I have attached the pdf file.
Regards,
Jay_Diddy_B
kicad schematic.JPG (29.48 kB. 687x379 - viewed 800 times.)