A dual technology intrusion detection device has a microwave detection sub-system, employing a bent mono-pole as an antenna to generate a symmetrical conically shaped volume of protection. The intrusion detection system also has a passive infrared intrusion detection sub-system, employing a hemispherically shaped fresnel lens having a plurality of lens segments, to detect infrared radiation from a plurality of spaced apart fields of view in a right symmetrical cone. The volume of protection for the infrared intrusion detector and microwave detector substantially coincide. In addition, the microwave detection sub-system employs a single bipolar transistor and a variable trim capacitor to generate the microwave energy and also uses the single bipolar transistor in an autodyne mode to mix the received microwave radiation.