I've tried to realise the following circuit:
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from this article:
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to demod a QPSK signal. I've tried using an AD8347 (Evaluation Board), but i'm not able to retrieve the "terms at twice the rate of the oscillator". All I can get from the outputs are the difference between the RF and LO, both I and Q.I'm using an (tunable) RF at 1.44GHz and LO at the same frequency. The LO is generated by ADF411xEB1. Even when I try to tune the RF as close to the LO, the "terms at twice the rate of the oscillator" never appears.
Is this becaues the range of AD8347 is 0.8-2.7GHz? So the doubler term,
2.88GHz, can never appear?
Has anyone tried any other components to realise this circuit?
Thanx in advance! kw