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ADF4159 Configuration with divide by 16 VCO

Question asked by wtidd on May 16, 2018

Hello,

I am using the ADF4159 with a divide-by-16 Prescaler VCO , and I am unable to configure the unit to get basic functionality, i.e. sawtooth chirp.  The VCO is a combined TX and RX and has some similar characteristics to the ADF5901 VCO:

 

E.g.    Tuning voltage = 0.7 to 2.5V

           VCO sensitivity = 720 MHz/V

 

Are there some specific settings I am overlooking for the ADF4159 to work with a lower frequency prescaler?

 

My current setup utilizes a reference clock of 30 MHz and I have tried many values of f_PFD including, 15 MHz, 30 MHz, and 60 MHz without success.

 

For instance, are two example outputs from my ADC that is digitizing the down-converted time wave, i.e. the beat and doppler frequencies:

 

1. Parameters for first attachment: f_PFD = 15 MHz, pll_DEV = 6.246 MHz (rf_DEV = 100 MHz),  t_chirp = 5 ms, f_adc = 50 KS/s.

2. Parameters for second attachment: f_PFD = 15 MHz, pll_DEV = 6.246 MHz (rf_DEV = 100 MHz),  t_chirp = 5 ms, f_adc = 100 KS/s.

 

Any insight would be appreciated.

 

Regards,

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