An active antenna power interface circuit couples a supply voltage from a radio
receiver to an antenna feed. The circuit comprises a DC power input and a power
switching element connected in series between the DC power input and the antenna
feed. The power switching element has a control input for selecting a conducting
state or a nonconducting state of the power switching element. A high side voltage
sensor senses a first voltage proportional to a voltage at the DC power input.
A low side voltage sensor senses a second voltage proportional to a voltage at
the antenna feed. A controller is coupled to the control input and to the voltage
sensors. The controller places the power switching element into the conducting
state, samples the first and second voltages, calculates a voltage difference in
response to the first and second voltages, compares the voltage difference to an
upper limit and a lower limit. If the voltage difference is greater than the upper
limit then the controller signals a short-circuit fault. If the voltage difference
is less than the lower limit then the controller signals an open-circuit fault.
