1
\$\begingroup\$

I'm working with a transmitting radio connected to two antennas. I understand that the power split between the two should result in a loss of 3dB, but a VNA shows a loss of 5.6dB. Does this mean an additional 2.6dB is lost to heat within the power splitter?

What kinds of modifications can I make on an off-the-shelf power splitter to solve this issue?

\$\endgroup\$
2
  • \$\begingroup\$ Do you have a datasheet for your splitter? \$\endgroup\$
    – The Photon
    May 6 '18 at 22:28
  • \$\begingroup\$ In one of the comments you mention that you only did two-port measurements. Was the other port terminated properly? \$\endgroup\$
    – Joren Vaes
    May 7 '18 at 7:21
1
\$\begingroup\$

Does this mean an additional 2.6dB is lost to heat within the power splitter?

Or there is a reflection back toward the generator.

Or there is some radiation from the splitter (this is unlikely to account for all of the excess loss you measured if you paid more than $1 for the splitter).

Did you measure \$S_{11}\$ when you had the thing on the VNA?

When you measured \$S_{21}\$, did you terminate port 3 properly?

What kinds of modifications can I make on an off-the-shelf power splitter to solve this issue?

If the additional loss is a problem for your setup, your best bet is probably buy a better splitter.

If the problem is due to reflection, you could conceivably improve the performance with some kind of matching transformer. If the problem is resistive or radiative loss, buying a better splitter is probably the only realistic choice.

\$\endgroup\$
2
  • \$\begingroup\$ I can't recall the results of the S11 tests that were done. And the S21 measurements only involved 2 ports (I'm not familiar with using a third/I don't think the VNA had a third) \$\endgroup\$ May 7 '18 at 3:16
  • \$\begingroup\$ If the VNA doesn't have a 3rd port to connect, you must terminate port 3 when measuring the parameters for ports 1 and 2. If you didn't do that, it can easily explain the bad results you saw. \$\endgroup\$
    – The Photon
    May 7 '18 at 16:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.