Why do some systems use a frequency doubler instead of a PLL? Do DDS spurs change with phase shift of, for example, 90 degrees versus 0?

Why do some systems use a frequency doubler instead of a PLL? Do DDS spurs change with phase shift of, for example, 90 degrees versus 0?

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    •  Analog Employees 
    on Mar 27, 2017 11:29 PM

    On behalf of Jeff Keip.

    A simple frequency doubling design can be much simpler to design than a full PLL, and require less circuitry.  If you are shifting phase repeatedly, you will introduce some spurious, but it is likely to be pretty close to the noise floor I would expect.  I