U.S. Philips Corporation

Other

Ian M Clarke

Andrew D Stewart

Eryk Stefan Doerman

David Antony Homer

William J Turner

David Hillary Evans

Stuart M Feeney

Leo Kool

In a microwave transmission system a microwave signal is transmitted by a transmitter (1) using an antenna (2) to a receiver (4) which employs an antenna (3). The received signal is coupled to a mixer (17) via a waveguide section (15) having a cut off frequency being higher than the frequency of the signal generated by the local oscillator unit (18). In this way undesired emission of local oscillator signal is avoided. Furthermore no additional image rejection filter is required.

Microwave transmission system

A receiver comprising an antenna array having a number of antenna elements. The antenna array is fed by a feeder. Switching apparatus are arranged for switching at least a first antenna element to the feeder or at least a second antenna element to the feeder. This provides a spatial shift of the antenna array without changing its radiation pattern. This improves the signal level when poor signal reception occurs due to multipath fading.

Antenna array switchable to provide spatial shift without change of

In a cell of a microwave cellular video distribution system, e.g a multichannel video distribution system operating at frequencies of around 29 GHz or 40 GHz, the transmitting antenna is composed of individual antenna sectors (62a,62b,62c . . . ) for transmitting the microwave signal towards different sectors (216a,216b,216c . . . ) of the cell. In accordance with the present invention, a respective monitor (D,R) is present in each of the different sectors (216a,216b,216c . . . ) of each/the cell to monitor the microwave signal transmitted in that sector. The antenna sectors (62a,62b,62c . . . ) are individually fed through controllable feed means (59,60,61) which permit individual control of the power level of the microwave signals transmitted by the individual antenna sectors (62a,62b,62c . . . ), including the switching off of that sector. A feedback coupling (40,44,49) is present between each monitor (R,D) and the controllable feed means (59,60,61) of the respective antenna sector (62a,62b,62c . . . ) to control individually the power levels transmitted towards the different sectors (216a,216b,216c . . . ) of each cell. In this manner the transmission pattern in each cell can be controlled and adapted to improve the quality of signal reception as requested by subscribers (R), to increase the operational life of the transmitter(s) by minimizing transmitter power, and to enhance responsiveness to other desirable and/or acceptable demands placed on the signal transmission.

Microwave video distribution system and adaptable microwave transmitter

In multiple-channel microwave transmitters and communications systems, such as multi-point video distribution systems operating at frequencies of around 29 GHz or 40 GHz, good frequency stability for each of the channel frequencies is achieved with a feed-back loop including an error detector circuit. The error detector circuit (39,29) is coupled between a sampler and an input circuit of the source. This detector circuit detects any drift or other error in the carrier frequency of the sample from the desired microwave frequency for that channel signal and provides a corrective signal to the input circuit. The part of the feed-back loop comprising at least a part of the detector circuit is common to a group of the channels. Switch means couple the common part of the feed-back loop between the sampler and the source input circuit of each channel, and so permit this common part to be time multiplexed between the respective feed-back loops of the group of channels. The input circuit for each source applies an up-datable bias signal for regulating the frequency of the source in accordance with the last corrective signal generated by the detector circuit for that source. By adopting such a stabilisation arrangement in accordance with the present invention, expensive component parts of the feed-back loop can be common to a group of the channels, so reducing the assembly cost of the multiple-channel transmitter. Good long-term frequency stability for all the channels can be obtained, including a reliably constant frequency relationship between the channels.

Microwave transmitter and communications system

A communications system includes a plurality of directional signal propagators, each defining a cell. The cells are arranged in a plurality of rows (R1 to R12), each row including repeating sequences of four propagators transmitting first, second, third and fourth signals (A, B, C, D), respectively, wherein the sequences in successive pairs of contiguous rows (R1, R2 etc.) are offset by one cell, and wherein diagonally arranged pairs of the propagators in pairs of contiguous rows transmit the same signal.

Communications system having diagonally-arranged pairs of signal

To weigh objects in quick succession, the objects are projected with a known horizontal velocity onto a ramp which has a surface which curves down through 90.degree.. The ramp can move horizontally in response to the impulse corresponding to the change in horizontal momentum of the object. A transducer senses the movement of the ramp and the output horizontal velocity of the object is sensed, enabling the change in horizontal velocity to be calculated. The mass of the object is calculated from the horizontal movement of the ramp and the change in horizontal velocity of the object. In order to obtain accurate sensing of the movement of the ramp, the transducer is a linear variable differential transformer having a primary winding energized by a cyclical carrier signal and two matched secondary windings in series; the secondary winding output signal is rectified to a corresponding DC voltage having ripple components, and a sample is taken of the signal at the zero voltage of the principal ripple component.

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Disley, United Kingdom

Ian M Clarke