CC1000 impedance matching (beginner)

Discussion in 'The Projects Forum' started by mariust, Jan 4, 2010.

  1. mariust

    Thread Starter New Member

    Aug 19, 2009
    I have a design using CC1000 RF chip for transmitting telemetry data on 433 MHz. For the range I require the project includes a low power amplifier to reach ~100 mW.

    The output impedance of the CC1000 is 140Ω according to the datasheet. Calculating a normal impedance matching circuit I would connect the components to GND. The TI recommended circuit for impedance matching connects the inductor and the capacitor to Vcc. On the other side the RF amplifier recommended circuit has a 180Ω resistor connected to GND.

    In my limited experience I never saw impedance matching components connected to Vcc. So I see two possible solutions:
    1. Connect the 180Ω resistor to Vcc and the RF signal will be referenced to the Vcc pin. But in my opinion that would mean that I should connect the antenna GND to VCC.
    2.Calculate the components for the CC1000 matching as referenced to the GND.