Abstract: A stabilised voltage controlled oscillator circuit comprises a closed loop circuit containing a voltage controlled oscillator (34), a local oscillator (40) and a harmonic mixer (38) that mixes a stabilised local oscillator (LO) frequency signal and a radio frequency (RF) signal from the voltage controlled oscillator (34) to obtain an intermediate frequency (IF) signal. An IF amplifier (42) is connected to a linear frequency discriminator (44) that provides an output signal to a summing amplifier (46), which is connected to the voltage controlled oscillator (34). The closed loop circuit uses the linear frequency discriminator (44) to provide a feedback signal that stabilises the voltage controlled oscillator (34).

Abstract: A frequency modulated continuous wave (FMCW) phase shift radar system includes a transmitter, a receiver, and a linearly-tuned oscillator circuit arranged in the transmitter as a source of electromagnetic radiation. The linearly-tuned oscillator circuit has a voltage controlled oscillator (VCO); and a closed loop feedback circuit including a local oscillator and a harmonic mixer coupled to receive a stabilized local oscillator (LO) frequency signal from the local oscillator and a radio frequency (RF) signal from an output of the voltage controlled oscillator. The harmonic mixer mixes the LO frequency signal with the RF signal to produce an intermediate frequency (IF) signal, and a linear frequency discriminator is coupled to receive the IF signal and to produce an output voltage signal which is applied to an input of the VCO to stabilize the latter, thus completing the feedback circuit.

Abstract: An electronic viewing aid according to the present invention comprises a small-scale, portable personal radar system adapted to be worn by a person, which radar system includes a miniaturised radar front end assembly (22) operating with millimeter wavelength electromagnetic radiation, an electrical power source, signal processing means and a sensory output means. In a preferred embodiment of the invention, the radar front end assembly (22) is constructed in the form of a pair of spectacles (76), in which both a transmit antenna (78) and a receive antenna (90) of the radar system are carried on respective lens elements (75) of the spectacles (76) and analogue portions of both a transmitter circuit and a receiver circuit are carried on respective side support frames of the spectacles (76); and the sensory output means is an audio output means including stereo headphones (98).