saulbit
Member level 4
I am designing a IQ modulator circuit. The main chip is HMC497. When I chose the LO frequency as 700MHz, and the baseband I,Q frequency as 10kHz, there would be a spur in 618.08MHz with a level of -83.44dBm and in 536.16 MHz with a level of -82.77dBm. The two band of the output was about -13dBm. The LO power is 0dBm. The I,Q baseband power was supplied by E8367D from Aglient and could be adjusted in a wide range. What was worse, the spurs got little change when I adjust the power of baseband and even of the LO.
However, when I change the baseband frequency from 10kHz to 100kHz, keeping the same LO frequency, the two spurs would locate in 853.60MHz and in 546.60MHz
. When I change the LO freuency from 700 MHz to 701MHz, the two spurs (with 100 kHz baseband IQ) would locate in 854.60MHz and in 547.40MHz.
Would sombody tell me some suggestions about such spurs? I couldn't even explain the cause of such spurs which can't be filtered by low pass filter.
However, when I change the baseband frequency from 10kHz to 100kHz, keeping the same LO frequency, the two spurs would locate in 853.60MHz and in 546.60MHz
. When I change the LO freuency from 700 MHz to 701MHz, the two spurs (with 100 kHz baseband IQ) would locate in 854.60MHz and in 547.40MHz.
Would sombody tell me some suggestions about such spurs? I couldn't even explain the cause of such spurs which can't be filtered by low pass filter.