Hey,
after following the instructions of another post of mine (https://ez.analog.com/rf/f/q-a/538009/using-adf4159-for-a-cw-radar-application/396330#396330), I tried to get the ADF5902 running this week. Im trying to lock the ADF5902 to a single frequency (no ramps), but cant get it to work. When using a spectrum analyzer I see the signal over a wide bandwith:
Im using the initialization sequence (via SPI) mentioned in the datasheet (slighty modified, by neglecting the writes to register R13-R16 as mentioned here: https://ez.analog.com/rf/f/q-a/544087/adf5902-cannot-be-locked) and setting the frequency to 24.1 GHz with the following:
- 20 MHz Oscillator
- Reference Doubler D=1
- Reference division factor R= 1
- Reference divide by 2 bit T=0
- N=301
- F_MSB =1024
- F_LSB=0
Here ist the sequence:
0x02000007 // R7 0x0000002B // R11 0x0000000B // R11 0x1D32A64A // R10 0x2A20B929 // R9 0x40003E88 // R8 0x800FE520 // R0 // delay of 10 microseconds 0x01800827 // R7 0x00000006 // R6 0x01E38005 // R5 0x00000004 // R4 0x01897803 // R3 0x00020642 // R2 0xFFF7FFE1 // R1 0x800FE720 // R0 // delay of 1200 microseconds 0x800FE560 // R0 0x800FED60 // R0 // delay of 500 microseconds 0x800FE5A0 // R0 0x800FF5A0 // R0 // delay of 500 microseconds 0x00000011 // R17 0x004F000C // R12 0x2800B929 // R9 0x01800427 // R7; here i deploy my pll settings 0x00000006 // R6 0x025A8005 // R5 0x00002004 // R4 0x0189F803 // R3 // delay of 100 microseconds 0x0000010B // R11
The used loop-filter:
What I tried so far:
- using a different ADF5902 Chip
- using a recalibration sequence
- changing the pfd frequency by disabling the referncy doubler
- setting the center frequency to a different frequency
- measured the 20 MHz Oscillator (works fine)
So far, nothing helped. I would really appreciate if someone could help me with this issue.
If you need any other information, please let me know!