Mixer-oscillator for radar detector - has resonant cavity and injection diode supplied via resistor

摘要

The mixer-oscillator for use in a portable radar detector e.g. used as part of an intruder detector system, has an injection diode (2) located within a resonant cavity (3). The diode (2) is supplied from a voltage source (1) via a resistor (5) and excites the cavity (3), for emission of the radar waves (6) via a horn antenna (4). The waves are reflected back, and the movement of the obstacle (7) causes variations in frequency, phase and amplitude, with the diode (2) exhibiting a base frequency appearing across the resistor (5) due to te mixing of the output waves (6) with the reflected waves (8). Preferably the injection diode has a N+PIN+ structure or a N+PPI+ structure.