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HMC778 RF output power too low

Question asked by 朱煦然 on Jul 17, 2018
Latest reply on Jul 30, 2018 by MRichardson

Refer to HMC778 evaluation board, I have made a PLL board and its schematic is shown below. The RF output power of hmc778 should be 9dbm@10GHz. And I want to get 9-5+14=18dbm output power through a attenuation network and PA hmc441.

 

The problem is the output power of hmc778 only reaches 2dbm@10GHz. So when I use a 100pF capacitor to replace the attenuation network, total output power reaches 16dbm@10GHz. Do you know any possible reasons that could cause the decrease of output power?

 

The RFOUT signal is correctly locked with REFRF signal. 

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