Amplitude Modulator / linear in voltage controlled Amplifier

[Andree Henkel]

Hi, there. I´m thinking of designing a driver circuit for acusto optical modulators. Short AOM:
https://en.wikipedia.org/wiki/Acousto-optic_modulator

Basic building blocks I guess: fractional PLL based XO, LC Bandpass, Amplitude modulation + On/Off Keying, Power Stage.

I´m currently stuck at the amplitude Modulation:
Analog Multiplier AD835 should work fine, but I would like to have somewhat higher max Bandwidth.

All voltage controlled Amplifier IC I found are linear in dB, which is not what I need, I would need linear to control voltage.

Any hints?

[NiHaoMike]

Have you considered a DDS with a microcontroller or FPGA driving a DAC?

[RoGeorge]

I remember Bragg cells working at much lower frequencies.  Why is it needed more than the max 250MHz of an AD835, what AOM model do you use?

There are many ways to get AM, one of the most used topology for an analog multiplier is the Gilbert cell.

[Andree Henkel]

@Nihaomike

DDS I considered, but XO + Bandpass is much less effort.

I want to be able to do analog modulation by external signal. So the DAC in the DDS doesn´t help.

[Andree Henkel]

@RoGeorge

yeh, it´s probably best to go for it with AD835. And limit carrier to 250MHz. Modulation will be maybe 1MHz.

In case I later move to higher carrier which I doub´t, maybe use a minicircuits part:
https://www.minicircuits.com/WebStore/dashboard.html?model=ADE-1%2B
Didn´t think of that.

[dmendesf]

Ad834 goes to 500MHz.

[RoGeorge]

There were a few topics about AOM here, on EEVblog, but can not find them any more, Google search was broken this month, like they would have wiped out their indexes or something, don't know what's happening there.

Could only find a couple of driver schematics:  https://www.eevblog.com/forum/rf-microwave/designingbuilding-2w-rf-amplifier-for-40-5mhz-fixed-frequency-sinewave/

[MasterT]

VCA824 710 MHz

[Andree Henkel]

@Master T:
thanks a lot, that´s exactly what Ì´m looking for.