Why ADRV9009 doesn't support FDD?
On behalf of Wyatt Taylor: Previous transceivers have supported FDD, and with the ADRV9009 ADI focused on TDD operation for two main raesons. First, when a transceiver is designed as an FDD device, it is inefficient when operating in TDD. There are two RFPLLs powered to the same frequency, burning extra power and risking VCO coupling. Second, many FDD systems have very high isolation requirements, 80+ dB, which cannot be met on a single chip. The ADRV9009 was optimzed for TDD systems, powering only on RFPLL in that mode, and allowing for a two chip FDD solution, improving isolation.