AM modulator- carrier wave

Thread Starter

max.azeem

Joined Nov 7, 2023
4
I am trying to produce a carrier wave whose frequency should be generated using a dielectric resonator oscillator with an output power of 15 dBm at an output frequency in the range of 2.0 GHz to 10 GHz. But my oscillator isn't working.
1699341596653.png

1699341648484.png

In summary, I'm trying to make an amplitude modulator, the modulated signal should have a mean power of 30 dBm with a modulation depth of +/-5 dB.

1699341767815.png
 

Ian0

Joined Aug 7, 2020
9,993
A TL071 is a poor choice.
1. You need a comparator, not an op-amp
2. TL071 suffers from phase reversal under certain circumstances.

why don’t you use a 555?
 

BobTPH

Joined Jun 5, 2013
9,116
A TL071 is a poor choice.
1. You need a comparator, not an op-amp
2. TL071 suffers from phase reversal under certain circumstances.

why don’t you use a 555?
None of which will work anywhere near the 2 to 10 GHz he is targeting. In fact, most will not get near 10 MHz.

GHz frequencies need very specialized devices and circuits. The physical layout is critical.
 

Ian0

Joined Aug 7, 2020
9,993
None of which will work anywhere near the 2 to 10 GHz he is targeting. In fact, most will not get near 10 MHz.

GHz frequencies need very specialized devices and circuits. The physical layout is critical.
I assumed that part of it wasn’t meant to be 10GHz (as it isn’t the missing dielectric resonator) Timing resistors/capacitors suggest about 700kHz.
 

DickCappels

Joined Aug 21, 2008
10,224
It would be best to study RF oscillators using a single transistors as the oscillating component.

Any particular reason for specifying a dialectic resonator?

You mentioned a modulator. What is the nature of the signal that will be used to modulate the carrier, and what type of modulation do you want?
 

AnalogKid

Joined Aug 1, 2013
11,126
Just winging the numbers, I got something around 250 kHz. Still, not 2 GHz. And it's a squarewave.
U2 has its + power pin tied to its output.
The - power pin is not connected.
If this thing made an output, I think it would be the modulating signal on a DC offset that is shifted up and down at the oscillator frequency.
And there's that whole TL072 thing.

ak
 

Thread Starter

max.azeem

Joined Nov 7, 2023
4
It would be best to study RF oscillators using a single transistors as the oscillating component.

Any particular reason for specifying a dialectic resonator?

You mentioned a modulator. What is the nature of the signal that will be used to modulate the carrier, and what type of modulation do you want?
It's an audio file that I am modulating (amplitude modulating)
 

Thread Starter

max.azeem

Joined Nov 7, 2023
4
It would be best to study RF oscillators using a single transistors as the oscillating component.

Any particular reason for specifying a dialectic resonator?

You mentioned a modulator. What is the nature of the signal that will be used to modulate the carrier, and what type of modulation do you want?
so this is the project I'm working on:

Design an amplitude modulator using anyone of the methods covered in the class. The baseband signal is an audio signal x(t), which can be generated from an actual recorded clip of your favorite music.
The carrier frequency should be generated using a dielectric resonator oscillator with an output power of 15 dBm at an output frequency in the range of 2.0 GHz to 10 GHz. The modulated signal should have a mean power of 30 dBm with a modulation depth of +/-5 dB. Download the data sheets of the components from the manufacturer or distributor websites to design your modulator circuit to meet the specifications.
 

Ian0

Joined Aug 7, 2020
9,993
so this is the project I'm working on:

Design an amplitude modulator using anyone of the methods covered in the class. The baseband signal is an audio signal x(t), which can be generated from an actual recorded clip of your favorite music.
The carrier frequency should be generated using a dielectric resonator oscillator with an output power of 15 dBm at an output frequency in the range of 2.0 GHz to 10 GHz. The modulated signal should have a mean power of 30 dBm with a modulation depth of +/-5 dB. Download the data sheets of the components from the manufacturer or distributor websites to design your modulator circuit to meet the specifications.
So where does the 700kHz square-wave oscillator made from a TL071 fit in?
 

DickCappels

Joined Aug 21, 2008
10,224
You need an oscillator for the carrier frequency you need. Not sure you can find one that covers the range you mentioned, and you need a modulator.

I would discard the circuit you posted because it cannot be made to work, and start looking for your oscillator and modulator at minicircuits.
https://www.minicircuits.com/
 

MrAl

Joined Jun 17, 2014
11,559
I am trying to produce a carrier wave whose frequency should be generated using a dielectric resonator oscillator with an output power of 15 dBm at an output frequency in the range of 2.0 GHz to 10 GHz. But my oscillator isn't working.
View attachment 306953

View attachment 306954

In summary, I'm trying to make an amplitude modulator, the modulated signal should have a mean power of 30 dBm with a modulation depth of +/-5 dB.

View attachment 306955
Hello there,

Taking a quick look, it appears that you have overestimated the ability of a somewhat normal op amp to work at frequencies more than 10000 times greater than that op amp can do. I would guesstimate that one has a gain-bandwidth-product of maybe 1MHz, and you want to go to 10GHz, which is a long way to go.

Either that, or you just want to use this as some sort of proof of concept where you can design at a lower frequency (like 10kHz) then move the design to a better set of parts that work up around 10GHz or greater.

To get to that high of a frequency, even 1GHz, you have to get parts that can do that. These will be devices that are made for that and show that in the data sheets.
Also, your wiring technique and/or circuit board design will have to follow some strict rules regarding high frequency routing and bypassing and all that stuff. You are going to have to read up on this if you want to build a successful circuit.
 
Top