-1
\$\begingroup\$

I have a high frequency analog signal that has to be as noiseless as possible, say no ripple of a few millivolts? Now, I need to bring it down by almost 9V.

Is it reasonable to simply use a zener or rectifying series of diodes to drop this signal? Does such a diode exist?

What are my other options?

EDIT: Alright, I thought a shorter title would be better so I wrote it as "Dropping high frequency signal using diodes". I guess it caused a bit of misunderstanding.

\$\endgroup\$
7
  • \$\begingroup\$ How high is the "high" frequency? Most common diodes have other problems when trying to operate at high frequencies. Some Zener diodes will give you their specification related to frequency. Also, remember diodes will rectify AC signals. If just trying to reduce an AC voltage without noise (or rectifying distortion) just use a resistor divider. \$\endgroup\$
    – Nedd
    Commented Nov 21, 2015 at 15:00
  • \$\begingroup\$ @Nedd Thanks for the reply. I'm actually aiming for a few gigahertz (though my implementation might fall lower than that). \$\endgroup\$
    – Derpy_Merp
    Commented Nov 21, 2015 at 15:03
  • \$\begingroup\$ How about RF diodes?? \$\endgroup\$
    – Derpy_Merp
    Commented Nov 21, 2015 at 15:03
  • \$\begingroup\$ Not too many diode types will operate at the gigahertz range. Even the capacitance of the diode will leak much of the signal at those frequencies. There are some specialized micro-wave types but putting several in series would be costly. Have you considered using a simple RF transformer or attenuator (like those used on cable TV systems) to reduce the voltage? \$\endgroup\$
    – Nedd
    Commented Nov 21, 2015 at 15:10
  • \$\begingroup\$ Why would you consider using diodes to reduce an analog high frequency signal, (rather then a resistive divider)? Do you really have a pure AC signal or might this be a mixed AC signal on a DC voltage? \$\endgroup\$
    – Nedd
    Commented Nov 21, 2015 at 15:23

1 Answer 1

Reset to default
2
\$\begingroup\$

When talking about high-frequency (RF, microwave) signals, you normally describe magnitude in decibels (dB), not volts. The correct term for "reducing" the voltage is attenuation.

Depending on your requirements, you have a couple of options:

  • Use an attenuator to give you the required signal level. This goes in series with your signal.
  • Use coupling to get a sample of the main signal. This option is non-intrusive, so you'll have the full signal to use elsewhere if you need it.
\$\endgroup\$
2
  • \$\begingroup\$ Sounds like an RF transformer or attenuator to me. \$\endgroup\$
    – Nedd
    Commented Nov 21, 2015 at 15:28
  • \$\begingroup\$ I meant voltage shifting. Yes, I'm talking about amplitude. And, yes you can keep doubling a frequency using diodes and something else. Though the modified sine wave won't be very nice. \$\endgroup\$
    – Derpy_Merp
    Commented Jan 1, 2016 at 2:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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