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TRF7970AEVM with External Power Amplifier

SeugnMin Lee
Prodigy 160 points
Other Parts Discussed in Thread: RF430FRL152HEVM

Hello, 

I am using TRF7970EVM and commercialized external power amplifier to increase reading range. 

As shown in schematic attached, I inserted inductor and two capacitors for 45 degree phase shift and those were connected to RX pins. 

The waveform at RX pins showed perfect 45 degree shift and its amplitude was adjusted to be 3V. 

Surprisingly, when output power is less than 1W, it worked but it does not work anymore when I increase a power a little bit. 

The magnetic field is strong enough: transmitting power is confirmed. 

I am reading data from RF430FRL152HEVM. 

I also tired to change Regulator & I/O control register settings (B6) but it did not help. 

Could anyone guide me to right way? I am not RF expert so I think there are terrible mistakes...

  • 0
    TI__Guru*** 135355 points
    Hi SeugnMin,

    We are looking into this, but if we could get a few more details that would help us further:

    Do you have a schematic for the Bandpass Filters and the Power Amplifier?
  • 0 in reply to Ralph Jacobi
    TI__Guru* 91206 points
    usually we would not connect to 50 ohms here - its not most efficient way really - but anyway - have a look at your mod depth (this is on downlink) - if that is incorrect, the tag will not be able to respond. (i.e. you said you have the power out...but did you check this too?)

    otherwise, then you need to make sure you are not over saturating the receivers or have blown them out. i suspect that as you raise power, you are raising this level, thus, possibly going above what it can handle