what is difference between upconverter and modulator

Thread Starter

paragingle123

Joined May 21, 2018
2
I need to know what is difference between upconverter and modulator.both upconverter and modulator multiply the signal in time domain which ultimately do addition of frequency in frequency domain so what is difference between them
 

andrewmm

Joined Feb 25, 2011
1,752
up convertor as you say, makes copy of original signal at a different frequency,

A modulator can be of many types
you could be modulating to AM, FM, PSK etc , without up converting
or it could also up convert,
 

Delta Prime

Joined Nov 15, 2019
1,149
Hello there :)
I need to know what is difference between upconverter and modulator
It depends on the user the user selects either to up convert the signal or down convert the signal what you really want to know is the difference between mixers and modulators!
Allow me to clarify please...
A mixer takes an RF input signal at a frequency fRF, mixes it with a LO signal at a frequency fLO,and produces an IF output signal that consists of the sum and difference frequencies, fRF ± fLO.
The user provides a bandpass filter that follows the mixer and selects the sum (fRF + fLO) or
difference (fRF – fLO) frequency.
Some points to note about mixers and their terminology:
• When the sum frequency is used as the IF, the mixer called an upconverter; when the
difference is used, the mixer is called a downconverter. The former is often used in a transmit
channel, the latter in a receive channel.
In a receiver, when the LO frequency is below the RF, it is called low-side injection and the
mixer a low-side down converter; when the LO is above the RF, it is called high-side injection,
and the mixer a high-side down converter.
Modulators (sometimes called balanced-modulators, doubly-balanced modulators or even on
occasions high level mixers) can be viewed as sign-changers. The two inputs, X and Y, generate
an output W, which is simply one of these inputs (say, Y) multiplied by just the sign of the other
(say, X), that is W = Ysign(X). Therefore, no reference voltage is required. A good modulator
exhibits very high linearity in its signal path, with precisely equal gain for positive and negative
values of Y, and precisely equal gain for positive and negative values of X. Ideally, thea amplitudeof the X input needed to fully switch the output sign is very small, that is, the X-inpute exhibitsa comparator-like behavior.
 
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Thread Starter

paragingle123

Joined May 21, 2018
2
Hi sir
In AM demodulator the LO need to be in sync with carrier frequency in order to demodulate the signal. The same applies with mixer? In downconversion local oscillator (LO)need to be in synch with transmitter(upconverter)?
 

Delta Prime

Joined Nov 15, 2019
1,149
Oh my goodness . I just wanted to hit this thread not marry it! :p you have taken too big of a bite and in no way am I trying to beat you up,
Your reply dictates my response,
You need more theory not a bunch just a little bit more then it'll all come together you're almost there.
ARRL - the National Association for Amateur Radio. Do not let the word amateur fool you their experts . With that said you should also know that I am a contributor to the latest ARRL RF handbook, research Beat frequency, harmonics, Spurs.
You only need reinforcement in the nomenclature of this particular subject. I believe you will do well now get out of here!;)
 
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