Abstract: An oscillator circuit comprising first and second mutually electromagnetically couplable resonant circuits, the second circuit comprising a dielectric element and excitation means operable to produce a first frequency of oscillation, the first circuit comprising the dielectric element, excitation means including a two-terminal Schottky device, preferably a Schottky diode, operable, responsive to an applied signal, to vary the resonant frequency of the first resonant circuit, and thereby vary the frequency of oscillation of the oscillator circuit.

Abstract: An oscillator circuit comprising first and second mutually electromagnetically couplable resonant circuits, the second circuit comprising a dielectric element and excitation means operable to produce a first frequency of oscillation, the first circuit comprising the dielectric element, excitation means including a two-terminal Schottky device, preferably a Schottky diode, operable, responsive to an applied signal, to vary the resonant frequency of the first resonant circuit, and thereby vary the frequency of oscillation of the oscillator circuit.

Abstract: A unit for detecting a moving person or object by means of doppler frequency shift. The unit comprises a microwave circuit board (1) accommodating an oscillator and a mixer, and an antenna board (2) carrying transmit (8) and receive (9) patch arrays. In the assembled unit the two boards (1,2) are disposed adjacent one another. Coupling between the microwave circuit and the antenna arrays is achieved by two slots (6,11) resonant at the oscillator fundamental frequency and formed in a ground plane (5) on the microwave board (1). Feed striplines (7,10,12) on the two boards (1,2) lie orthogonal to the slots (6,11) and are terminated in T-sections (15,14). The stripline/slot arrangement suppresses emission at the oscillator second harmonic frequency. The antenna board (2) has no electrical connection to the microwave circuit, enabling the radiated beam shape to be changed by simply replacing the antenna board with one having a different patch array pattern.

Abstract: A dielectric resonant oscillator for use in frequency conversion of X-band signals comprises a dielectric `puck` (1) of high dielectric constant mounted on a printed circuit board (3) adjacent a stripline conductor (5). The puck (1) forms a resonant cavity to signals in the stripline and the system oscillates typically at X-band. The puck (1) has an inherent temperature compensating dielectric/temperature characteristic which generally compensates temperature dependent circuit characteristics. However the substrate (3) dielectric/temperature characteristic (FIG. 1 ) upsets the balance, the substrate (3) being coupled to the cavity by the electric field. The balance is regained by introducing a metallic pad (7) under the puck of (1) half the puck diameter thus bringing the temperature driven variation to 1.25 ppm. A further development provides two or more radial extensions (9) of the pad (7) which shift unwanted hybrid modes away from the wanted TEM mode and prevent mode jumping and consequent instability.