DIY DM /CM Seperator for EMC - LISN Mate

[Noy]

My LISN has ;-)

Reworked Jay_Diddy_B's LISN:

https://www.eevblog.com/forum/projects/5uh-lisn-for-spectrum-analyzer-emcemi-work/75/

You are right, will use hot glue to mount the cores.

And with the 0.4mm wire i will check if i have something here, else i have to purchase one from aliexpress / mouser.

Can you post a picture from your winding?

[T3sl4co1l]

As long as the wire length is short, and the turns fit through the core, you're fine.

Wire-wrap wire, pairs from Ethernet cable, etc. are also good candidates -- give or take exact impedance required of course.  I think... one of them should be lower and the other should be about that impedance (insulated twisted pair)?  But if you use magnet wire or insulated for both it's not going to be too far out.

Tim

[Noy]

Here are my design files, hasn't build it up completely yet. Still missing the copper wire (on its way from china)..
Also for china Hammond 1590B cases

[Knuddel]

Hi Noy,

if you do not heasitate ordering from the big "a" you can serch for "Block Kupferlackdraht Basteldraht Schmuckdraht Kupfer-lackdraht Kupferdraht Wickeldraht Kupfer Draht Cul 100/0.40".

Unfortunately I have ordered the PCBs with BNC-jacks, now.
This fits in a 1590G case that is smaller but straight BNC print jacks are not easy to buy and I need to get some adapter cables to attach it to your LISN design with SMA, that I preferred.

I should have waited for your final data from your last post #52. That comes for the larger 1590B case but has SMA-jacks...

[Noy]

My 0.4mm Cooper wire arrived.
Would somebody share a picture of their working wire wound?

10x twisted 0.4copper and the other 10x twisted cat5 cable? Or cat5e?

[Jay_Diddy_B]

My 0.4mm Cooper wire arrived.
Would somebody share a picture of their working wire wound?

10x twisted 0.4copper and the other 10x twisted cat5 cable? Or cat5e?

Noy and the group,

Pictures of the transformers can be found in this message:

https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/msg3120176/#msg3120176

I will reproduce them here:






Jay_Diddy_B

[Noy]

THX, wire arrived. Completed the build but measurment are still not done yet..

I think the cores are smaller than yours was a bit thightly to get the 10 windings of cat5 wire  onto the core but it fits.

Unfortunally i cannot do TDR measurments.. Would Luke to have a sampling scope but too expensive currently..
Have to find out how i can do it with the VNA..

[TimNJ]

With a VNA, you can make these measurements:

1. Impedance and SWR of each LISN port
2. Common-mode rejection
3. Differential-mode rejection

For all measurements, if you are not directly using a port (SMA or BNC), it should be terminated with a 50 ohm termination.

Ideally, when LISN 1 and 2 are driven with a purely common-mode signal, there should be almost no signal at the differential-mode output, over the entire frequency range. You can drive both inputs with an in-phase signal by connecting the output of the VNA to a resistive power splitter, i.e. Mini-Circuits ZFRSC-42-S+.

And, when LISN 1 and 2 are driven with a purely differential-mode signal, there should be almost no signal at the common-mode output, over the entire frequency range. You can drive both inputs with a 180-degree out-of-phase signal by using a hybrid power splitter, i.e. ZFSCJ-2-2-S.

[Knuddel]

Hi! (What is the trick to get the pictures in line with the text? OK, thanks Tim! Is it possible to keep them at default tumbnail size and only load to full size by mouseclick?)

in the meanwhile my BNC-sockets arrived from china as I missed to order the cheap TE 5-1634503-1 from Mouser when I ordered all other components for Mate and Lisn.



I measured the transmission behavior with Scope Bode Plot function:

When measuring it from Lisn2 In to CM Out it's like this: (result -6dB)



Same but leaving DM-port unterminated: (result -9dB)



When measuring from Lisn2 In to DM Out: (result -6dB)
(seems there is some signed integer treated as unsigned somewhere in the MSO5000 Bode Plot script when phase flips over 180°)



When measuring from Lisn1 In to CM out: (result -6dB)



From Lisn1 to DM out: (result -6dB)
(Why does it shows a higher edge frequency? Is there an impedance discontinuity because of too much twists in the copper ends near the solder pads? Or should I remove the last winding form CAT5 because it fills the hole in the core and coulpes in to the other side?)




Seems that these cores are close to the TDK ones, are they?


When measuring the whole path from DUT+ and DUT- through
the forums final double Lisn with -10dB attenuators inside and
through the Lisn-Mate to CM out I've got the following results:

(I guess it is -6dB because the signal was divided by 2 when feeding it to DUT+ and DUT-,
but why isn't it -10dB-10dB-6dB-6dB=-32dB)



When measuring the whole path from DUT+ and DUT- to DM out: (-3dB ?)



There first I thought something went wrong, but on the other hand it reflects somehow the overlay of both DM-plots above.



P.S.: I had have only one BNC termination and used a 25cm BNC to SMA cable with a SMA termination at the end for second termination. For third termination I simply connected the Lisns SMA output to the port. You find the termination type in the file names for each plot.

For noise measurements I am still wondering how I have to set my correction level in the spectrum analyzer with the different setups:
1 Lisn with -10dB attenuator no mate                                          +10dBµV (add 10dB noise)
2 Lisn with -10dB attenuator no mate                                          +16dBµV
2 Lisn with -10dB attenuator mate DM out, CM terminated            +3dBµV
2 Lisn with -10dB attenuator mate CM out, DM terminated            +6dBµV

This is what the scope plot tells me, but the scope shows a dB relation between two peak ac voltages, how does it fits to the absolute dBµV ?
I guess as this is also relation of voltage to 1µV, it fits very well, right?

But as the CISPR standard does not distinguishes between CM and DM and only measures with two Lisn the output of one of them
do I have to compensate anyhow or is the -6dB included into the standard?
And as Jay_Diddi_B writes in post #21 that this Mate stuff is only for interest on the way to find the noise source but with correct design could stay in the setup,
then I should have to compensate the SA in the same way as without Mate like this:

1 Lisn with -10dB attenuator no mate                                          +4dBµV
2 Lisn with -10dB attenuator no mate                                          +10dBµV
2 Lisn with -10dB attenuator mate DM out, CM terminated            +10dBµV
2 Lisn with -10dB attenuator mate CM out, DM terminated            +10dBµV

Please correct me if I am wrong!
For me it's same: "Also, I have no idea what I'm talking about."
And: "I appreciate all of your guidance (and patience with me)."

Kind Regards,
Hanno

[T3sl4co1l]

After posting, right-click copy link address on an attachment (at default thumbnail size) and paste inside an img tag.  The inline thing was, half ass disabled I guess, not just removed, because image cache was getting corrupted or something.

Tim

[HallWu]

Hi group,
I spent most of the day designing and building a clone of the HP35676A Reflection/Transmission Test Set. This work with the HP3577A Network Analyzer. I will described the design and construction of the RT Test Set in another thread.

I have the S-parameter Test set, but this has a lower frequency limit of 100kHz.

The RT Test Set will work down to 5Hz.

DM Impedance Measurements

The target impedance is 100

(Attachment Link)

The measure impedance was 97

-3dB point is

  (Attachment Link)


CM Input Impedance

The target impedance is 25

(Attachment Link)


And at low frequencies

(Attachment Link)

The theoretical number should 12.5

The measured impedance for DM and CM signals is very close to the values expected.
The low frequency corner is sufficiently low, so it will not impact EMC measurements.

Regards,
Jay_Diddy_B

Dear Jay_Diddy_B,

Thanks for your excellent work on LISN Mate, that helps me a lot. If I want to move the corner frequency below 10kHz, should I increase the inductance of T1 and T2? To be more specific, should I increase the turns of T1 and T2 from 10 to 15? Dose the copper below the T1 will affect the CMRR of DM_out port? I have tested the CMRR of DM_out port based on the paper ‘Characterization, Evaluation, and Design of Noise Separator for Conducted EMI Noise Diagnosis’ , but it is only -30dB at 150kH~30MHz. What should I do to improve the performance of CMRR at DM_out port? I am looking forward to your reply.

Best wish,
Jerry.

[Smokey]

What did you guys decide about alternate cores that you can actually get?  What are the best ones?