Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P5/00—Coupling devices of the waveguide type
  • H01P5/08—Coupling devices of the waveguide type for linking dissimilar lines or devices
  • H01P5/10—Coupling devices of the waveguide type for linking dissimilar lines or devices for coupling balanced lines or devices with unbalanced lines or devices
  • H01P5/107—Hollow-waveguide/strip-line transitions

Definitions

• the present invention relates generally to feed structures for electromagnetic waveguides, cavities and antennas, and, particularly, but not exclusively, to a feed structure for feeding RF radiation from integrated circuits to RF waveguides, cavities and antennas, to an integrated circuit incorporating an RF feed structure, to an assembly comprising a waveguide, cavity, antenna or mounting flange and an integrated circuit comprising a RF feed structure, and to a method of constructing a monolithic integrated circuit .
• feed structure is usually used to refer to the arrangement of electrical conductors which are used to transfer RF energy between adjoining transmission lines (such as icrostrips, striplines, coplanar transmission lines etc.) and an RF guiding structure, such as a waveguide, cavity or antenna, preferably in such a way that the energy is efficiently coupled from one medium to the other and propagates freely within the waveguide, cavity or free space.
• adjoining transmission lines such as icrostrips, striplines, coplanar transmission lines etc.
• RF guiding structure such as a waveguide, cavity or antenna
• Waveguides are typically used to convey microwave and millimeter wave signals because of their relatively low loss and controlled propagation characteristics at high RF frequencies. Since waveguides need to be interfaced to electronic circuitry of some form, it is necessary to employ structures which efficiently couple RF energy from the waveguide to other transmission line structures which in turn interface to electronic circuitry.
• a Microwave Monolithic Integrated Circuit might typically be mounted on a planar substrate (eg a circuit board) so that signals propagate from the MMIC to the substrate via bond wires and then along substrate transmission lines, through an aperture and into the waveguide by means of a portion of the substrate which acts as the radiating element (a monopole feed, for example) .
• a monopole feed for example
• Expensive substrate materials such as quartz must be used to ensure low RF loss and to allow high precision conductor patterning which is typically needed for the radiating element .
• the characteristic impedance of the overall feed assembly is difficult to predict and control during manufacture which results in poor RF reproducibility .
• Each component of the assembly introduces a degree of variability in circuit impedances, particularly any MMIC- to-substrate bond wires used, (iv) Heatsinking:
• a dielectric substrate is typically used to allow transmission lines and radiating elements to be patterned on the surface. This often means that the thermal conductivity of the substrate is relatively poor and does not provide adequate heatsinking for MMICs .
• the present invention provides an integrated circuit comprising: - an RF circuit element, and an RF coupling means for coupling RF energy between the integrated circuit and an RF guiding structure, the coupling means including a ground plane referenced transmission line structure which traverses a region of the integrated circuit where a portion of the ground plane reference is absent.
• the RF circuit element may be an RF transmitter or receiver or transceiver.
• the RF circuit element is arranged to transmit or receive high RF frequencies, and may be a microwave circuit element or millimeter wave circuit element.
• the RF coupling means directly couples the RF energy between the integrated circuit and the RF guiding structure. This means that the coupling means couples the
• RF guiding structure includes, but is not limited to, a waveguide, cavity, antenna or mounting flange.
• the ground plane reference is preferably formed by electrically conductive material and the absent portion is formed by an aperture in the electrically conductive material, which acts as a radiating element, for radiating coupled RF energy.
• the aperture is preferably formed by removing a portion of the electrically conductive material of the integrated circuits ground plane to form a re-entrant feature in the outline of the ground plane.
• the re-entrant feature may be formed by a polygon of more than four sides.
• the radiating element may be formed by removing a portion of the electrically conductive material of the
• the RF guiding structure is a waveguide, cavity, antenna or mounting flange
• the aperture acts as the radiator.
• the aperture is a slot formed in the ground plane. Preferably, it extends only part way across the ground plane .
• the integrated circuit is mounted in direct contact with a wall of the RF guiding structure (the wall containing the feed aperture) , so that an entire surface of the integrated circuit is in contact with the wall .
• the present invention further provides an assembly comprising: - an RF guiding structure, and an integrated circuit for transmitting or receiving RF signals in accordance with any one of the preceding claims, the integrated circuit being mounted such that it couples RF signals between the waveguide, cavity, antenna or mounting flange and integrated circuit through an aperture in a surface or wall of the RF guiding structure.
• the present invention yet further provides a feed structure wherein the ground plane reference is formed by electrically conductive material and the absent portion is formed by an aperture in the electrically conductive material which acts as a radiating element, for radiating coupled RF energy.
• the present invention yet further provides a method of constructing a monolithic integrated circuit, comprising the steps of forming a feed structure in the monolithic integrated circuit, feeding RF signals directly to an RF guiding structure, for transmission or reception of RF energy from the RF guiding structure, the feed structure comprising a ground plane referenced transmission line structure which traverses a region of the integrated circuit where a portion of the ground plane reference is absent .
• the present invention yet further provides an RF coupling arrangement comprising an RF circuit element, and an RF coupling means for directly coupling RF energy between the integrated circuit and an RF guiding structure, the coupling means including a ground plane reference transmission line structure which traverses a region of the integrated circuit where a portion of the ground plane reference is absent.
• FIG. 1 is a schematic of a perspective view of a prior art assembly illustrating a prior art RF feed structure
• Fig. 2 is a schematic of an exploded perspective view of an assembly in accordance with an embodiment of the present invention pertaining to waveguides and/or resonant cavities,
• Fig. 3 is a schematic of a partial cross-section view of the assembly of Fig. 2, with the addition of a back- cover cavity cap,
• Fig. 4 is a schematic of an exploded perspective view of an assembly in accordance with an embodiment of the present invention pertaining to antennas, and
• Fig. 5 is a schematic of an exploded perspective view of an assembly in accordance with an embodiment of the present invention pertaining to mounting flanges.
• Fig. 1 illustrates a prior art feed structure for coupling RF energy produced by a monolithic integrated circuit 1 to a waveguide or resonant cavity 2.
• the integrated circuit 1 is mounted on a planar substrate 3 (e.g. a circuit board), which may be of an expensive substrate material such as quartz, so that signals propagate from the integrated circuit 1 to the substrate via bond wires 4 and then along substrate transmission lines, in this case a microstrip 5 having a microstrip ground plane 6, through an aperture (not shown) and into the waveguide 2 by means of a portion of the substrate 3 which acts as a radiating element, in this case being a monopole antennae 7.
• This arrangement suffers from the disadvantages which are discussed above, i.e. expensive substrate materials required, expensive, high precision, manufacturing techniques required; difficulties in controlling characteristic impedance, and inadequate thermal conductivity of the substrate material.
• Fig. 2 illustrates an assembly in accordance with an embodiment of the present invention, which includes a waveguide or resonant cavity 10 and an integrated circuit 11.
• the integrated circuit 11 includes a coupling means 12 which is arranged to couple directly to corresponding coupling means 13 in the waveguide or resonant cavity 10 for coupling RF radiation to or from a RF circuit element 14 formed in the integrated circuit 11.
• the integrated circuit is mounted directly to the waveguide 10, with no interconnecting substrate.
• the RF signal is instead coupled directly from the integrated circuit 11 to the waveguide 10.
• the integrated circuit incorporates a ground plane 15 on its under side (i.e. the opposite side to that containing the active circuit elements such as transistors) .
• the ground plane 15 usually provides a ground plane reference for circuit elements formed in the integrated circuit.
• the ground plane 15 is usually a continuous metallic layer.
• the coupling means 12 includes an aperture 12, in this case in the form of a slot extending partially along the ground plane 15.
• An RF transmission line 16 in this case a microstrip-like structure, extends from the RF circuit element 14 (which may be a microwave transmitter, receiver or transceiver) , across the region where the aperture 12 is located but spaced from the aperture within the integrated circuit, (in this case the transmission line 16 is formed on the opposite side of the integrated circuit to the ground plane) to a "via hole" 17.
• the via hole 17 provides the return connection to the ground plane 12.
• the positioning of the aperture 12 is such that return currents of the microstrip transmission line 16 are diverted around the aperture 12 , so that RF energy radiates outwardly from the aperture 12 in a direction perpendicular to the integrated circuit 14 surface.
• the integrated circuit is positioned against the waveguide 10 such that the aperture 12 is positioned against corresponding aperture 19 in the waveguide 10. RF energy thus can be made to couple directly to or from waveguide cavity 20 formed by the waveguide 10.
• the shape of the aperture 19 in the waveguide 10 may be designed to optimise coupling into the waveguide and may incorporate various three dimensional angular features to achieve this .
• An ideal shape may be established by the skilled person.
• cap 21 is mounted to the waveguide 24/integrated circuit 14 assembly to enclose the integrated circuit 11 (thereby providing mechanical and environmental protection) and to form a cavity which reflects RF energy propagating away from the waveguide or resonant cavity 20 back towards the waveguide aperture 19, as illustrated by RF propagation lines 22.
• the cap may include a means 23 for tuning the cavity 24, the means may be a screw 23 which protrudes into the cavity
• the width of the slot 12 can be made relatively small (e.g. 0.2 x 2mm) and occupies only a small fraction of the total integrated circuit area (which might be of the order approximately 3 by 3mm) .
• the integrated circuit may be a microwave monolithic integrated circuit.
• feed structures on the integrated circuit would be encompassed by the present invention, conventional feed structures such as patches or monopoles would lead to a dramatic increase in size of the integrated circuit and are not preferred.
• Fig. 4 illustrates an assembly in accordance with an embodiment of the present invention, which includes horn antenna 30 and an integrated circuit 11.
• the integrated circuit 11 includes a coupling means 12 which is arranged to couple directly to corresponding coupling means 13 in the antenna 30 for coupling RF radiation to or from a RF circuit element 14 formed in the integrated circuit 11.
• the integrated circuit is mounted directly to the antenna 20, with no interconnecting substrate.
• the RF signal is instead coupled directly from the integrated circuit 11 to the antenna 30.
• Fig. 5 illustrates an assembly where the integrated circuit 11 is mounted on a mounting flange 40.
• the integrated circuit contains coupling means 12 which couples RF radiation through the flange aperture 43 and into whatever structure the flange is mounted against (not shown) .
• the flange is mechanically fixed to this structure by means such as screws through mounting holes 44.
• the integrated circuit may be secured to the waveguide resonant cavity, antenna or mounting flange by gluing, soldering or mechanically fitting the circuit to the outer surface, without the need for specialised RF bonding techniques. Assembly processes are therefore very simple. Further, there is no need for expensive substrates.
• the integrated circuit is attached directly to the metallic surface of the structure, in the preferred embodiment.
• the waveguide, antenna or mounting flange may contain structures such as filters which modify the spectral composition of signals coupled from the integrated circuit. These filter structures can be used to increase the efficiency of which the integrated circuit aperture radiates into the waveguide, cavity, antenna or mounting flange.
• the structure (which is usually metallic or metallic matrix) provides excellent heat sinking for the integrated circuit.

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• 2000
  • 2000-09-04 WO PCT/AU2000/001042 patent/WO2001018901A1/en not_active Application Discontinuation
  • 2000-09-04 EP EP00960224A patent/EP1221181A4/de not_active Withdrawn

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