Electronics > RF, Microwave, Ham Radio

Simple SSB modulator only with DDS?

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Scratch.HTF:
I've come across a DDS-based AM modulator which uses an external connection for programming full scale DAC current (e.g. Rset in the AD9851) for RF modulation, but has anyone used only a DDS to generate SSB signals including at different RF frequencies?

antenna:
The ARRL Handbook talks about using I/Q modulators to do it.  I think you can do it with trigonometry.

ejeffrey:
Sure.  You just multiply by an amplitude scale factor after the phase to sin/cos evaluation.

radiolistener:

--- Quote from: Scratch.HTF on May 18, 2022, 01:41:22 am ---but has anyone used only a DDS to generate SSB signals including at different RF frequencies?

--- End quote ---

You're needs filters to cut-off the carrier and second side band in order to get SSB. You can do it with electromechanical or quartz filter. Another approach is to use digital signal processing (DSP) and DAC. It also needs to apply filters but with DSP it happens in digital domain.

You can do it on intermediate frequency and shift frequency up/down with mixer and additional oscillator. In such way you can do it at different RF frequencies

UR5FFR:

--- Quote from: Scratch.HTF on May 18, 2022, 01:41:22 am ---has anyone used only a DDS to generate SSB signals including at different RF frequencies?

--- End quote ---
Yes, this is possible. PE1NNZ make this on ATTINY45 micro-controller and a AD9834 DDS.
http://pe1nnz.nl.eu.org/2013/05/direct-ssb-generation-on-pll.html

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