# Frequency Multipliers

New for March 2020.  Multipliers are nonlinear, two-port devices where an input signal is used to create an output signal that is at a higher harmonic. The most common multipllier is a doubler.  The idea is that you take a periodic signal (ideally a single tone) and distort it. If you look at the Fourier series, you will find various components at n x F0. Here is a great little table of fourier series content in various periiodic waves:

https://web.calpoly.edu/~fowen/me318/FourierSeriesTable.pdf

If you rectify a sine wave you will generate a DC tone, a tone at F0, and tones at even harmonics 2F0, 4F0...

In order to form odd harmonics 3F0, 5F0... you need to distort the wave with a limiting function, to create a pseudo square-wave. An ideal square wave has only odd harmonics:

https://en.wikipedia.org/wiki/Square_wave#Fourier_analysis

Yeah, we need to put our own figures on this page one of these days...

Note that there is really is no "small-signal response" in multipliers. You have to hit them at their sweet spot of input power

If you are looking for frequency multipliers, try our partner website everything RF. They have a parametric search tool which helps engineers find Frequency Multipliers from the leading manufacturers - Click here.

Why would you wasnt to use a multipler? For example, you use an integraed PLL/VCO chip and it only reaches 18 GHz but you need to source 30 GHz.  Just double it!

Phase noise in multipliers... are coming soon...

## Passive multipliers

Passive multipliers are usually an arrangement of diodes that rectify a signal. For a doubler, you can expect 8-10 dB loss.

In subharmonic mixers, there is a built-in passive doubler.

Passive doublers are usually not reciprocal, meaning one port will be defined as the input and the other defined as the output. In some case the ports will be obvious, as the input will be coax and tghe output will be waveguide.

One fairly well-known doubler uses ISIS diodes. Yet another page we need to add!

## Active multipliers

Active multipliers combine a multiplier with an amplifier on the output.  So why isn't there a portmanteau of "multifier" or ""ampliplier"? "Multifier" is the better choice as the multiplier comes first in the network.  We'll add it to our portmanteau dictionary and see if it takes hold.

Example MMICs that can be used as multiplers are:

MIMIX XX1001.  This is perhaps the first product available in this category.  It might be obsolete,

CMD213

MMA-17341

## Comb generator

A comb generator is like a mulitipler, except you excite it at a much lower frequency and it puts out a ton pr frequencey products, separated by the fundamental.  You can pick whatever product you want with a banpass filter.