# [Solved] Do frequency multipliers multiply the frequency?

#### ballsystemlord

Joined Nov 19, 2018
107
Hello,
Instead of getting a frequency generator, I opted to use the one inside of my oscilloscope. It only goes up to 25MHz and only for sine waves.
I thought, "I'll get a frequency multiplier and multiply the signal." Now I have read about multipliers here: https://adsantec.com/a-basic-introduction-to-frequency-multipliers/ , so it's not like I'm just guessing what they do.
I bought this one: Frequency Multiplication 2~50MHz Clock Multiplier Frequency Multiplication Module as it fits well within what my oscilloscope can do and can multiply the signal quite a bit.

I attached it to my oscilloscope, turned the oscilloscope's signal generator to 1MHz sine wave, and connected my 10x probe that came with the oscilloscope.

I got a square wave...
I turned the frequency up to 25Mhz, and I got something that looked like a square wave...

I don't understand. I expect a sine wave out when I put a sine wave in. I expect a square wave out when I put a square wave in. I expect a saw wave out... etc., etc., etc...

What's going on?
Is this how frequency multipliers are supposed to work?

Thanks!

Pictures below:
PS: I just chose channel 4 because I liked the color.
PPS: The scope is calibrated and the probe has been compensated.

#### WBahn

Joined Mar 31, 2012
28,179
It says that it is a "clock multiplier", which implies that it is expecting the input signal to be a square wave, so it is probably using a comparator to condition the input signal into a square (or rectangular) waveform and then multiplying that.

What's the bandwidth of your scope?

#### LowQCab

Joined Nov 6, 2012
2,916
It's not an RF-Amplifier, it's a "Clock" ( Square-Wave ) Frequency-Multiplier.
A "Clock" Signal is virtually always a Square-Wave, ( or should be ).
It's just a fluke that it just happened to be able to "sort-a-kinda" work with a Sine-Wave-Input.

What You want probably doesn't exist.
You need a very expensive Signal-Generator,
and at the frequencies that Yo want, every single little aspect of anything
carrying that Signal will have to be treated as any other very high Frequency RF-Signal.
This means special Cables and Connectors that carefully maintain a
uniform Impedance throughout whatever Circuit You are working with.
.
.
.

#### ballsystemlord

Joined Nov 19, 2018
107

#### ronsimpson

Joined Oct 7, 2019
2,617
Please indicate what frequency range you want output. sign wave

#### ballsystemlord

Joined Nov 19, 2018
107
Please indicate what frequency range you want output. sign wave
I do not currently need any particular frequency. I made the purchase of the multiplier knowing that I probably would not want to wait (or couldn't wait, as the case may be), +30 days for a package from china.

#### Papabravo

Joined Feb 24, 2006
19,850
Frequency multiplication is a bit tricky. You might be tempted to think that if you multiply a 5 MHz sinewave by a 7 MHz sinewave the result would be a 35 MHz sinewave. Such is not the case. The output actually can contain 4 different frequency components. You have the original 5 & 7 MHz components, but you also have components at 2 MHz (the difference of 7 and 5) and 12 MHz (the sum of 7 and 5).

#### WBahn

Joined Mar 31, 2012
28,179
Frequency multiplication is a bit tricky. You might be tempted to think that if you multiply a 5 MHz sinewave by a 7 MHz sinewave the result would be a 35 MHz sinewave. Such is not the case. The output actually can contain 4 different frequency components. You have the original 5 & 7 MHz components, but you also have components at 2 MHz (the difference of 7 and 5) and 12 MHz (the sum of 7 and 5).
Frequency multiplication and multiplying two signals together (a.k.a., mixing) are not the same thing.

Frequency multiplication involves a single input signal, while mixing involves two signals.

#### WBahn

Joined Mar 31, 2012
28,179
I have a suspicion that it may be using a NB3N502 or something similar:

https://www.onsemi.com/pdf/datasheet/nb3n502-d.pdf
Something similar, but it doesn't use that one. Not only are the frequency ratios quite different, but so is the pinout.

None-the-less, that datasheet likely gives a good feel for whatever part is actually used.

#### ballsystemlord

Joined Nov 19, 2018
107
I have a suspicion that it may be using a NB3N502 or something similar:
I'd tell you the exact chip, but the top has been rubbed off.I checked online and I cannot find any photos of the board with the chip numbers displayed.

#### DickCappels

Joined Aug 21, 2008
9,621
I prefer a DDS approach when a programmable sine wave is needed, though sometimes the jitter is bothersome.

In the mean time for the curious, you can use analog multipliers to raise sine wave frequencies by powers of two:

Take a sine wave and shift it 90° then multiplying that with the original sine wave doubles your frequency.

This is discussed on page 23 of the attached application note from Analog Devices.
The entire publican can be downloaded here: Analog Devices : Multiplier Application Guide

It is tough to do this well above the low MHz range.

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#### DickCappels

Joined Aug 21, 2008
9,621
Sorry the link does not work. I thought I checked. Yes, that looks like the same applications note. Thank you for catching the error.