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For an application I need to generate a 10 MHz sine wave signal that is modulated with 20 KHz triangle signal. This is going to be frequency modulated.

This goes into another circuit which require a low phase noise. What is my best option to generate this signal effectively with low noise and reasonable cost. So far I have seen DSS solutions from ADI.

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closed as unclear what you're asking by Andy aka, laptop2d, Finbarr, Dmitry Grigoryev, duskwuff Jul 26 '18 at 21:09

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    \$\begingroup\$ 20 kHz is the modulation frequency, or the peak deviation? \$\endgroup\$ – The Photon Jul 24 '18 at 15:18
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    \$\begingroup\$ Modulating the 10 MHz by how much? What is the frequency deviation required? \$\endgroup\$ – The Photon Jul 24 '18 at 15:29
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    \$\begingroup\$ This is hard work. Like watching paint dry! \$\endgroup\$ – Andy aka Jul 24 '18 at 15:37
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    \$\begingroup\$ You are modulating the frequency with a 20 kHz triangle wave. You could be modulating it between 9.99 MHz and 10.01 MHz, or between 2 MHz and 18 MHz. Some solutions might work for one but not the other. (Another word for this is modulation index). \$\endgroup\$ – The Photon Jul 24 '18 at 23:15
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    \$\begingroup\$ 10 MHz seems like an inconveniently low frequency (in terms of required antenna size) to do that kind of thing at. And unless you live in Somalia or someplace, a band that's likely to be cluttered with lots of licensed users who might notice your experiments. \$\endgroup\$ – The Photon Jul 25 '18 at 1:01
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Solutions that come to mind:

  • Microcontroller + DAC: The use of DSP / DDS (direct digital synthesis) techniques on a fast microcontroller (preferably with an integrated FPU) to generate a frequency modulated sine wave could be a viable/inexpensive solution, with an internal or external (parallel) DAC, and an accurate external clock source. - A 10 MHz (carrier) and a 20 kHz modulation signal could probably be generated with a microcontroller from the STM32F/H series (by ST). - Lookup tables, ARM DSP optimizations and fix point math could help. - Whether the result satisfies your application's requirements depends on the necessary quality of the signal (sampling rate/depth, aliasing effects, jitter etc.). - The signal quality could probably be improved with an external analog filter.
  • FPGA + DAC: The signal could be generated with an FPGA and digital-to-analog converted with a fast parallel DAC, all clocked from an accurate clock source. The sine wave/carrier and the modulation signal (triangle) can be generated right inside the FPGA. (Instead of using a lookup table, the CORDIC way of implementing a sine function could come in handy). This could probably already be accomplished with a small/inexpensive FPGA from the ICE40 series (by Lattice).
  • Specialized IC: The direct digital synthesis (DDS) chips by Analog Devices might be a good choice, like you've mentioned above (?). (But I've never worked with them myself yet, so I can't tell...) - Compared to the other solutions above, specialized ICs are black boxes, and your solution will strongly depend on the supply of a single manufacturer.
  • Analog cirucit: The whole thing could be done with analog techniques, but that's usually harder, in my experience. And it is probably more expensive/difficult to get reliable/stable results.
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