A system for using wireless signals to detect objects of a certain type, such as concealed weapons, leverages the fact that different objects have different resonance characteristics. The system transmits wireless signals of different frequencies, and returns from such signals are measured. The return of a signal from an object at a resonant frequency of the object will be stronger than a return of a signal from the object at a non-resonant frequency. The system analyzes the returns in an effort to determine when a return is sufficiently large to indicate that it was reflected from an object of interest. When an object of interest is detected, the system adjusts a characteristic of the system, such as antenna orientation or pulse shape, based on an estimated location of the object, and then runs a test to confirm the detection of the object, thereby eliminating at least some false positives.