PLL output signal with an offset

[sushie96]

I have used your program in raspberry pi3 for controlling the adf4351 evaluation module, I have connected the rf_out+ with my spectrum analyzer, but I am receiving the output with an offset. When writing 437MHz it is outputting signal at around 390MHz. I haven't modified the code and ran the default code after compiling. Please help me with this. Thanks

[sushie96]

Also the compilation of the library gave these warnings

In file included from adf4351.c:75:0: adf4351.c: In function ‘adf4350_set_freq’: adf4351.h:88:44: warning: result of ‘9 << 29’ requires 34 bits to represent, but ‘int’ only has 32 bits [-Wshift-overflow=]

define ADF4350_REG2_NOISE_MODE(x) ((x) << 29)

                                        ^

adf4351.c:367:30: note: in expansion of macro ‘ADF4350_REG2_NOISE_MODE’ ADF4350_REG2_MUXOUT(0x7) | ADF4350_REG2_NOISE_MODE(0x9))); ^~~~~~~

[F5OEO]

No problem with warning, however, it assume that RefClock if 10Mhz which could be maybe an other value on your board. You can change it here according to your value : https://github.com/F5OEO/rpiadf4351/blob/a2c5de3eaa08bac6fd5af4ac88f58b6c1dbb7913/ctladf4351.c#L15

And recompile (make)

[sushie96]

Sir, I am not using any ref in, i want to use the 25Mhz internal vco

[F5OEO]

Replace 10000000 by 25000000

[sushie96]

Thanks Sir, Now the offset is gone I tested with 437MHz and 2GHz signal. but now when I am writing 2.1GHz and even for 1.95GHz frequency, it is not showing any output at that frequency is it something to do with channel spacing value?

[sushie96]

I also tried sweeping from 1000 MHz to 1100MHz with a sweep step of 10MHz, with a delay of 2seconds. I didnt work as properly and after 1050 MHz the frequency output was at random frequencies.