British Gas Plc

The Secretary of State for Defence in Her Britannic Majesty's Government

David J Gunton

Roger Philip Ashworth

Paul B Cordes

Michael P Stansfield

Howard F Scott

Edward George Paige

Lucy J Manning

A mixer circuit (1), comprised of two planar dipoles (3, 5), mounted upon a dielectric insulator or semiconductor body. Mixer elements (M1, M2) are incorporated in the path of each dipole (3, 5), there being two such elements each fed by both dipoles. The first of these dipoles, dipole (5) is split along part of its length, this split section (23) serving as a delay-line between one of the mixer elements, element (M1), and the second dipole (3). The second dipole (3) is split along at least a part of its length and is open at one end. A connective link (29C) is provided between one of the delay-line conductors (25/11) and one of the split parts (9) of the second dipole (3). Intermodulation signal developed in the one mixer (M1;M2) can then be extracted from the split ends (9, 13; 7, 11)of the second dipole (3). The link (29C) is formed outside the envelope of the delay-line (23) and does not affect its broad band properties. A slowing mechanism--for example, combine interdigitated structure (31) can be included in the delay-line (23). Preferably the link (23C) runs parallel to a significant portion of the length of the second dipole (3), the latter thus modified forming a folded dipole.

Mixer circuit

A wheeled support assembly 10 is manually pushed over the ground and has a motor 22 rotating an antenna assembly 60 about a vertical axis 24. Encoders 28 on the antenna shaft 20 and on a wheel axle encode antenna angular position and position over the ground. Transmitted pulses and received data pass through a rotary microwave connector 26. For example, 400 sets of pulses are emitted at equal angular intervals in each revolution of the antenna assembly. The interval between pulses is e.g. 12 microseconds, with 256 pulses per set. Noise reduction is achieved by processing the received data accordingly. In a modification the rotary connector 26 is single channel with some electronic stages mounted on the rotating antenna assembly. Power is coupled to them via the microwave cable. An umbilical connects the assembly 10 to a support facility including a computer. Alternatively, battery power is used with data transferred radiatively.

Ground probing radar method and apparatus

A method and apparatus for producing data indicative of the presence of buried objects, wherein two waveforms I(t) Q(t) are combined with two reference waveforms Ir(t) Qr(t) using filters 10, 12, 14, 16 of two types A, B. Type A has time response Ir(-t) and type B has time response Qr(-t). The products {I(t)@Ir(t)}.multidot.{Q(t)@Qr(t)} and {I(t)@Qr(t)}.multidot.{Q(t)@Ir(t)} from multipliers 18, 20 are subtracted to give V1 and added to give V2 in the combiner 30. A list of object distances (36) is derived from V1. A list of object orientations (46) is derived from V2. Object times (34) are used to section V2 at (40) on a time basis. A correlation operation is represented by @. The invention is particularly applicable to location of buried pipes using ground probing radar, but is also useful in locating planar objects and in other systems. The waveform combination suppresses noise and clutter. I(t) and Ir(t) are quadrature versions of Q(t) and Qr(t). The emitted radiation is circularly polarized.

Method and apparatus for combining waveforms

An antenna assembly which comprises a first laminar structure which includes a sheet of dielectric material having on one side a contiguous metal sheet and on the other side a strip transmission line adapted to be coupled with signal feeding means, and a second laminar structure, one side of which is in contact with the transmission line, and having on the other side, at least one region but preferable at least two concentrically arranged regions of a coated or cladded metal which serves as a radiator, characterized in that the transmission line is non-symetrically disposed with respect to the radiator.

Broadband microstrip antenna

An antenna assembly is provided for use in locating buried objects, particularly long thin objects such as pipes can be located, determining the position, and ascertaining the pipe direction by taking measurements from a single point, without mechanical movement of the antenna, and allowing a better suppression of spurious signals and reduction in false indications; which assembly has a plurality of antenna arms adapted and arranged to transmit and receive radiation into the ground and is characterized in that the arms have, on at least the surface nearest the ground, a cladding of a substantially lossless dielectric material, the relative permitivity of said dielectric being at least 3.5 and the thickness of said coating being at least .lambda..sub.d /20 where .lambda..sub.d is the wavelength of lowest frequency of the radiation to be transmitted from the antenna.

Antenna assembly for microwave reflection survey equipment

A method and antenna assembly for transmitting into the ground polarizeable radiation whereby buried objects, and particularly long thin objects such as pipes can be located, the position determined, and the pipe direction ascertained, by taking measurements from a signle point, without mechanical movement of the antenna, and thereby allowing for good suppression of spurious signals and a reduction in false indications. The method includes the steps of transmitting into the ground polarizeable radiation, receiving reflected signals, indicative of the objects, incident upon at least two co-located angularly disposed transducers and comparing the signals thus received, wherein the radiation is transmitted from a transducer source which is co-located but angularly disposed with respect to each receiver transducer. An antenna assembly suitable for use in the method of the invention includes a substantially planar arrangement of at least three, co-located, two-terminal antennas wherein the antennas are angularly disposed with respect to each other around a common point and each antenna is adapted to be capable of selectively transmitting polarizeable radiation into the ground and receiving reflected radiation from out of the ground.

Microwave reflection survey technique for determining depth and

A two track surface acoustic wave device is provided with a phase plate interposed between input and output transducers on one of the two tracks. An electrical coupler is connected across the output transducers to produce a sum signal at at least one of its outputs corresponding to surface waves making a single transit of each track. The coupler combines other signals having a different phase relationship--eg those corresponding to a triple transit of each track to give a null at one of these outputs. The coupler is connected into matched output loads to provide mutual isolation at its inputs. Tracks of different length may be used instead of the phase plate. Instead of electrical coupling, acoustic coupling may be provided between the two tracks to produce a similar result.

Surface acoustic wave devices and systems including such devices

A microstrip or stripline coupling device in which coupling is effected between two spaced transmission line electrodes at least one of which is a comb electrode comprising a bus bar having a series of electrode fingers projecting transversely from both sides thereof along the coupled length. Preferably both electrodes are comb electrodes, the fingers of which are interdigitated to improve the coupling. In a broadband coupler in accordance with the invention, the difference between the phase constants of the two electrodes is varied along the coupled length, e.g. by varying the lengths of the fingers, enabling the concept of warped mode coupling to be realized. Preferably also the coupling coefficient between the two electrodes is varied along the coupled length, e.g. by varying the spacing between the electrodes or the degree of overlap between the electrode fingers.

Stripline coupler having comb electrode in coupling region

A directional coupler comprising a dielectric substrate having two opposing faces carrying a sheet electrode on one face and two comb like electrode structures on the other face. Each comb electrode has finger like electrodes projecting from a bus bar towards the other comb. Varying the length of finger electrodes and the amount of overlap varies the amount of signal power coupled between the two combs. Couplers may be arranged to couple up to 100% of signal power. When half signal power is coupled, a 3dB coupler, various microstrip circuits may be built e.g. balanced mixers, power dividers, or power combiners.

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Stakeford, United Kingdom

David J Gunton