A ranging Doppler radar system for identifying, and measuring range, velocity, direction of movement of a vehicle with minimal interference from surrounding environs and with low probability of intercept by the vehicle. In order for both the small-signal gain and the large-signal response to be independent of temperature, the emitters of the two amplifier transistors are connected to one another by a compensation resistor which has a negative temperature coefficient. The system comprises a wireless receiver having an estimator programmed according to the method. The first code generator receives the first signal, and generates a first calibration code. The method comprises forming at least one coil around the magnetic sensor; connecting the coil to an alternating current power source; and modulating the current from the power source.