Transmit Power Monitor (TPM) functionality - AD936x
The on-board transmit (TX) power monitor can be used as a power detector, enabling highly accurate TX power measurements in TDD mode. Maximum input power to TPM port is +4dBm and it has an accuracy of 1 dB. TPM functionality is described under ‘Tx Power monitor section’ in User Guide (UG-570).
TPM reuses RX circuitry, hence same is only useful in TDD mode. In TDD mode you cannot take the IQ data out using TPM port. A few points to take care while using TPM port:
- TX Mon DC Offset Cal is redundant, no need to execute
- In TDD mode, bit 0x015[D2] (Dual Synth Mode) should be set HIGH. This allows the RX Synth and associated circuitry to stay high when needed for TPM
- TX1 and TX2 Transmit Attenuation should be equal to avoid crosstalk
TPM Test mode. (I,Q data out using TPM port)
If the application is TDD, it is not possible to output TPM IQ data on the RX data port as the TDD state machine is overriding the 0x14[D7] bit and is not enabling the Rx port for data transmission. But this is possible in FDD mode, where both the data paths are enabled. Steps for doing this are:
- Register 0x001[D6:D5] – set the Bits high.
- Register 0x014 Bit D7 (Enable Rx Data Port) - needs to be set high.
- Register 0x06E Bits D7 and D5 (TPM Enable) - needs to be set high.
- Register 0x057 Bits D2 and D3 ( Analog Power Down Override) – needs to be cleared
TPM(TX RSSI) is possible in TDD and FDD mode, for TDD mode is as explained in UG but for FDD mode set Register 0x001[D6:D5] – set the Bits high