phase noise of pll

Phase Noise
The Phase noise in a synthesizer is, most likely, the most difficult problem to resolve.
The noise appears in the system due to a noise of 1/f and thermal noise in the devices that it is
generated particularly by the VCO.
The noise injected into the oscillator by its devices or by external means, can influence
both the phase as well as the amplitude of the output signal, although in most cases the effect
of the distortion in the amplitude is negligible. The phase noise can be seen as a random
variation of the zero crossings from its ideal position throughout the time axis. The
designation phase noise is used in the frequency domain, whereas in the time domain, we use
the designation jitter


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  1. Oussama

    Hi Luis,I have only one board assembled at the monmet. It does not have a microcontroller on it, but can be controlled via a Bus Pirate or microcontroller connected to the pin header. I would like to do a revision of the board that has a simple USB microcontroller onboard (probably an NXP ARM Cortex-M0 or M3), so I can use it without having to hook it up to other hardware first. But it will probably be a couple of months before I finish that project. How soon do you want to have an LO board?In the meantime, you might want to look at . Their ADF4350 board looks like a good design at a reasonable price.Free free to e-mail me at , if you want to talk more.

  2. guru


    A Phase Lock Loop is a feedback system that allows us to generate a phase signal with
    the input signal. It is a mixed analog/digital circuit with many applications including
    frequency synthesizers, data acquisition, in RF transmitters/receivers to generate frequencies
    for the local oscillator, etc.
    PLLs with Frequency and Phase detectors have been widely used because they have a
    wide capture band and the frequency detection, aside from the phase, reduces the acquisition
    time. Besides this, the capture and lock bands are only limited by the excursion allowed at the
    VCO voltage control. Generally, the PLLs with a phase/frequency detector (PFD) have a
    circuit that accompanies the PFD, the charge-pump (CP). This circuit, in conjunction with a
    loop filter, converts the logic states produced by the PFD into analog signals that serve to
    control the VCO.

    • Maria

      Thanks. I am using my Bus Pirate to do the SPI configuration of the ADF4350. I have Python code that will write the restriegs in the correct order. I use the ADF4350 register tool (Windows application) from Analog Devices to compute register values, then I put them into the Python code. It would be fairly simple to modify my code to assume a certain reference frequency and configuration, and have the code calculate the appropriate PLL settings. I can post the code to my GitHub repository if you’re interested in building on it.