# Signal Multiplication: Circuit Diagrams & Electronic Processes

• n0_3sc
In summary: A diode is used to multiply two separate signals because its a nonlinear element. The circuit diagram for a mixer would look like a circle with an X inside it.
n0_3sc
In engineering we're always taught block diagrams in communication systems, specifically multiplying two signals...
How exactly do you multiply 2 separate signals electronically? What does the circuit diagram look like?

You use a mixer. Block diagram of a mixer is a circle with an X inside. How does a inside of a mixer look like is another story.

The simplest type of mixer is just a non-linear element of some sort, usually a diode.
Nowadays mixer can be quite comlicated but in old-style crystal radios you can even see the diode which in their case consists of a thin wire in contact with a semiconducting crystal, the voltage-current characteristics of the metal-semiconductor interface is non-linear and can therefore be used to down-convert the radio signal back to audio frequencies.

a PWM chopper circuit, with an LPF, can multiply two signals at low frequencies. it's just a sort of variation of looking at the "mixer" or "non-linear element" way of doing it.

also, there used to be these things we called Analog Computers that had very high quality op-amps in them in blocks for integrators, abs(), exp(), and log(). with a exp() and log() blocks, you can accomplish multiplication of positive voltages ("one quadrant multiply"). to do 2-quadrant multiply, i think there is something called a Gilbert cell that does it and i think they've been put together in a manner to accomplish 4-quadrant multiply (where you don't care about the sign of either voltage getting multiplied).

check out

http://www.analog.com/en/subCat/0,2879,770%255F847%255F0%255F%255F0%255F,00.html
http://www.analog.com/en/subCat/0,2879,770%255F848%255F0%255F%255F0%255F,00.html
http://www.analog.com/en/subCat/0,2879,773%255F862%255F0%255F%255F0%255F,00.html

http://www.analog.com/analog_root/static/raq/moreInfo/computation.pdf

you can get some pretty good app note and other information like that from Analog Devices. now they do a few different kick-ass DSPs (with warts) but when i was in college, they were purely analog.

Last edited by a moderator:
f95toli:
How is a diode used to multiply them? I understand its a nonlinear element but is their an example circuit of how you would implement a diode and use it too multiply two separate signals?

rbj:
That pdf file was exactly what I wanted to see - thanks.

## What is signal multiplication?

Signal multiplication is a process in which a circuit or electronic device combines two or more input signals to produce an output signal that is a multiple of the inputs. This can be achieved through various methods such as amplification, modulation, or mixing.

## How does signal multiplication work?

The exact process of signal multiplication depends on the specific circuit or device being used. In general, it involves manipulating the properties of the input signals, such as their amplitude, frequency, or phase, to create a new output signal that is a multiple of the inputs.

## What are some common applications of signal multiplication?

Signal multiplication has a wide range of applications in various fields, including telecommunications, audio and music production, and scientific research. It can be used to improve signal quality, increase data transmission rates, and create complex waveforms for various purposes.

## What are some common circuit diagrams used for signal multiplication?

Some common circuit diagrams used for signal multiplication include operational amplifiers, mixers, and frequency multipliers. These circuits typically consist of various electronic components such as resistors, capacitors, and transistors, arranged in a specific configuration to achieve the desired multiplication effect.

The main advantage of signal multiplication is that it allows for the creation of complex signals that would not be possible with a single input. This can be useful in various applications, such as in telecommunications where multiple signals need to be transmitted simultaneously. However, signal multiplication can also introduce noise and distortion to the output signal, which can be a disadvantage in some applications.

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