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LMX2541: Spurious emmission at VCO frequency + 430 MHz (measured with SQ2380E VCO variant)

Part Number: LMX2541

Tool/software:

Hi,

I am using the LMX2541SQ2380E in full chip mode to generate a 2400-2450 MHz RF signal. I noticed in the spectrum measurement of there is a large spurious peak at the VCO frequency + 430 MHz (for all measured VCO frequencies) in both bypass-mode (VCO_DIV=1) but also in divided mode (VCO_DIV != 1). 

I measured this spurious on multiple board designs, tested with various configurations of PLL_R, PLL_N, and loop filter settings, but none seem to have a significant impact and different reference clocks. 

Is this a known spurious from the VCO? Or is there maybe a settings that I missed?

Due to the proximity it becomes quite hard to filter out this spurious to meet certification for use in transmit applications.