MOS parallel to antenna - antenna clamp, antenna modulator

Discussion in 'Wireless & RF Design' started by Tako, Dec 2, 2015.

  1. Tako

    Thread Starter Member

    Oct 21, 2014
    I would like to understand the following thing: in RFID passive circuits there are MOS transistors, which work as a clamp or a modulator. These transistors are in parallel to antenna. Drain is connected to one end of the antenna and source is connected to the other end. The examples can be found here:

    The question is: where is the body of the MOS transistor connected?

    Nodes on the antenna, change voltage values. Taking as the example, once there is a positive voltage on "Data In" node (node 2) and negative on node 3 and after that node 2 is negative and node 3 positive. If the transistor source was connected to the body, for the situation where node 3 is positive and node 2 negative, the body-drain diode would turn on. Is that the behavior we would like to observe?