TX driver amplifier for Pluto

    I am building QO-100 station around Adalm-Pluto. I did not find exctly suitable exciter amplifier between Pluto and the TX PA. I have limited skills and experience in uwave design so I thought that this may me a good learning project for me.

    I set following spec for myself:

    - can be narrowband 2400MHz

    - should have enough gain and power to get Pluto 0dBM up to +30dBM(1W) level

    - spurious filtering

    - simple design

    - 12V powered


    Afrer searching what is available and what can be purchased somewhwre I ended up tu try with Qorvo RFPA5218 chip.


    Schematic OH2NLT_2400MHz_1W_Amp.pdf



    Only challenge with this chip is that it is 3x3mm leadless package. Thermal design needs also some attention.



    Some measurements with hp8753C



    Results looks better what I expected from my first design. PCB is ordinary 1mm FR4 material.


    Some more measurements with generator and power meter. Bellow pdf graph of gain and linearity of the amplifier. Measurement setup (cables and connectors) attenuation at 2.4GHz is about 1.4dB what should be added to the results. 28dB gain is not bad at all. Only problem is the limited thermal conductivity of 1mm FR4 board. No matter how many vias you try to put under the very small chip. 0.3...0.5W is the max continous power with this design. Output start to drop when the chip gets hot. Design is anyway good enough for SSB use.


    OH2NLT_RFPA5218_linearity.pdf


    Measurement setup. hp 20dB attenuatoe and Anritsu MA2421A/ML2437A. Generator hpE4422B


    Full 1W reached but needs little more than 0dBm drive. 3-1.4 = about 1.6dBm