Abstract: A radar detector includes features to reduce emissions such as those typically generated by the detector's local oscillator. Two low noise amplifiers (LNA's), operating in X band and a combined K/Ka band, respectively amplify X and K/Ka band signals from separate antennae, and deliver those signals over separate, elongated and narrow signal paths to X and K/Ka mixers, where those signals are mixed with local oscillator (LO) signals to produce IF for detection. The elongated, narrow signal paths from the antennae to the mixers reduce LO emissions, and those emissions are further reduced by incorporating radar absorbers between the circuit board and detector case along the antenna-mixer path, including radar absorptive paint on the circuit board itself along this path, and sealing the case with a conductive sealing gasket.

Abstract: The invention concerns radar detectors which are capable of monitoring at least two frequency bands. A broad band antenna is provided, together with a mixer comprising an anti-parallel pair of diodes, and at least one local oscillator. The local oscillator frequency is mixed with radar frequency from the antenna to produce an intermediate signal which is amplified further down converted detected and fed to signal processing circuitry to actuate an alarm when radar frequency of interest is detected. The most effective mixing with the RF input takes place at twice the local oscillator frequency. By application of direct current bias to the mixer, the most effective mixing with the RF input is changed to occur at the local oscillator frequency. The local oscillator is used to monitor two different radar frequencies by application and non-application of DC bias to the mixer. For multiband detectors, more than one local oscillator may be used.

Abstract: The invention concerns radar detection devices sensitive to signals from various different frequency bands. A broad band antenna is provided, together with a mixer and a plurality of local oscillators. Signals from the local oscillators are mixed one at a time with signals from the antenna, there being one local oscillator signal for each radar frequency or pair of frequencies of interest which may be received by the antenna. Each local oscillator signal is chosen so that when it is mixed with the respective radar frequency signal, an intermediate signal is produced which is the same for all mixtures. This intermediate signal is further down converted and fed to signal processing circuitry to produce an alarm when radar frequencies of interest are detected.