GB2082845A - Microwave components - Google Patents

Abstract

In a dielectric waveguide transmission path including a corner or bend a planar conductive member (5) is secured at the outside of the corner or bend to reflect microwave energy around the bend from one section (1) of the transmission path to the other (2). The conductive member (5) may be electrically connected to the conductive substrate (3) of the transmission path. <IMAGE>

Description

SPECIFICATION Microwave components The present invention relates to microwave components.

In particular but not exclusively the invention relates to microwave transmission paths incorporating bends The use of dielectric waveguides as open planar transmission lines at millimetric microwave frequencies is receiving increasing attention as a low-loss alternative to conventional waveguide and microstrip lines.

One of the problems associated with the realisation of components and systems in dielectric waveguide concerns the design and production of low-loss bends. Microwave loss at bends due to radiation is dependent upon the permittivity of the dielectric material and upon the operating frequency. In generai, however, to achieve an acceptably low loss at a bend the radius of curvature of that bend has to be not less than about seven times the guide wavelength, with the attendant disadvantages of increased iine lengths and overall area to realise complex circuits.

According to one aspect of the present invention Ih a microwave component comprising an elongated member of solid dielectric material secured to a conductive substrate to act as a dielectric waveguide, said member is cut transversely of the length thereof and a conductive member is secured to the cut face so as to interact with microwave energy in said dielectric waveguide.

The conductive member may ba arranged at substantially forty five degrees to the length of said member and may be connected directly to the conductive substrate, so as to form a reflector to direct microwave energy from said elongated member into another member of dielectric material extending at right angles to said first member.

The conductive member may alternatively be arranged to provide a predetermined value of resistance such as to act as a resistive load for said waveguide, preferably matched to the characteristic impedance of said waveguide.

In another embodiment the conductive member may be connected to said conductive substrate by way of a semiconductor diode to form a microwave mixer or detector.

According to another aspect of the present invention in a microwave transmission path comprising an elongated body of a solid dielectric material secured to a substantially planar conductive substrate to act as a dielectric waveguide, a waveguide bend between two substantially straight sections of said dielectric waveguide that are at an angle to one another in the plane of said planar substrate comprises a substantially planar conductor secured to a substantially planar surface of said dielectric material at the outside of said bend, said planar surface being substantially perpendicular to said planar substrate and disposed at substantially equai angles to said two sections of said waveguide.

A microwave transmission path in accordance with the present invention will now be described by way of example with reference to the accompanying drawing, of which:- Figure 1 shows a perspective view of part of the transmission path, Figure 2 shows part of the path of Figure 1 in plan view, and Figure 3 shows a microwave device utilising transmission paths of the form shown in Figures 1 and 2.

Referring first to Figure 1 the transmission path comprises first and second limbs 1 and 2 of solid dielectric material secured to a planar metal substrate or ground plane 3. Each of the limbs 1 and 2 is of rectangular cross-section, 0.056 inches wide and 0.028 inches thick, and acts as a section of dielectric wave-guide for use at frequencies in a band from 60 to 95 gigahertz. The dielectric material may be Z - cut quartz, and the ground plane 3 may be of copper.

As shown in Figure 2 the limbs 1 and 2 are formed integrally and contain a right-angle bend.

The outside of the bend is chamfered at forty-five degrees to each limb by a cut perpendicular to the ground plane 3 so as to halve the area of the notional square 4 at the bend, and a copper plate 5 is secured in contact with the chamfered face, this plate 5 being electrically connected to the ground plane 3.

The transmission path shown in Figures 1 and 2 is virtually identical in performance to a similar length of straight dielectric waveguide, whereas the bend before chamfering gave rise to a considerable level of radiation of microwave signals, resulting in high transmission loss.

As shown in Figure 3 the chamfered bend is particularly useful in proximity directional couplers, where the use of right-angle bends not only reduces the overall size of the circuit but enables the coupling length L to be defined precisely.

The transverse cut with conductive plate 5 may form the basis of other components of dielectric waveguide. For example, if the plate 5 is of a resistive material or if it is connected to the ground plane 3 by way of a resistor (not shown) the plate may act as a microwave load. Similarly if the plate 5 is connected to the ground plane 3 by way of a semiconductor diode (not shown) the arrangement may be utilised as a microwave mixer or detector.

Claims

1. A microwave component comprising an elongated member of solid dielectric material secured to a conductive substrate to act as a dielectric waveguide, wherein said member is cut transversely of the length thereof and a conductive member is secured to the cut face so as to interact with microwave energy in said dielectric waveguide.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Microwave components The present invention relates to microwave components. In particular but not exclusively the invention relates to microwave transmission paths incorporating bends The use of dielectric waveguides as open planar transmission lines at millimetric microwave frequencies is receiving increasing attention as a low-loss alternative to conventional waveguide and microstrip lines. One of the problems associated with the realisation of components and systems in dielectric waveguide concerns the design and production of low-loss bends. Microwave loss at bends due to radiation is dependent upon the permittivity of the dielectric material and upon the operating frequency. In generai, however, to achieve an acceptably low loss at a bend the radius of curvature of that bend has to be not less than about seven times the guide wavelength, with the attendant disadvantages of increased iine lengths and overall area to realise complex circuits. According to one aspect of the present invention Ih a microwave component comprising an elongated member of solid dielectric material secured to a conductive substrate to act as a dielectric waveguide, said member is cut transversely of the length thereof and a conductive member is secured to the cut face so as to interact with microwave energy in said dielectric waveguide. The conductive member may ba arranged at substantially forty five degrees to the length of said member and may be connected directly to the conductive substrate, so as to form a reflector to direct microwave energy from said elongated member into another member of dielectric material extending at right angles to said first member. The conductive member may alternatively be arranged to provide a predetermined value of resistance such as to act as a resistive load for said waveguide, preferably matched to the characteristic impedance of said waveguide. In another embodiment the conductive member may be connected to said conductive substrate by way of a semiconductor diode to form a microwave mixer or detector. According to another aspect of the present invention in a microwave transmission path comprising an elongated body of a solid dielectric material secured to a substantially planar conductive substrate to act as a dielectric waveguide, a waveguide bend between two substantially straight sections of said dielectric waveguide that are at an angle to one another in the plane of said planar substrate comprises a substantially planar conductor secured to a substantially planar surface of said dielectric material at the outside of said bend, said planar surface being substantially perpendicular to said planar substrate and disposed at substantially equai angles to said two sections of said waveguide. A microwave transmission path in accordance with the present invention will now be described by way of example with reference to the accompanying drawing, of which:- Figure 1 shows a perspective view of part of the transmission path, Figure 2 shows part of the path of Figure 1 in plan view, and Figure 3 shows a microwave device utilising transmission paths of the form shown in Figures 1 and 2. Referring first to Figure 1 the transmission path comprises first and second limbs 1 and 2 of solid dielectric material secured to a planar metal substrate or ground plane 3. Each of the limbs 1 and 2 is of rectangular cross-section, 0.056 inches wide and 0.028 inches thick, and acts as a section of dielectric wave-guide for use at frequencies in a band from 60 to 95 gigahertz. The dielectric material may be Z - cut quartz, and the ground plane 3 may be of copper. As shown in Figure 2 the limbs 1 and 2 are formed integrally and contain a right-angle bend. The outside of the bend is chamfered at forty-five degrees to each limb by a cut perpendicular to the ground plane 3 so as to halve the area of the notional square 4 at the bend, and a copper plate 5 is secured in contact with the chamfered face, this plate 5 being electrically connected to the ground plane 3. The transmission path shown in Figures 1 and 2 is virtually identical in performance to a similar length of straight dielectric waveguide, whereas the bend before chamfering gave rise to a considerable level of radiation of microwave signals, resulting in high transmission loss. As shown in Figure 3 the chamfered bend is particularly useful in proximity directional couplers, where the use of right-angle bends not only reduces the overall size of the circuit but enables the coupling length L to be defined precisely. The transverse cut with conductive plate 5 may form the basis of other components of dielectric waveguide. For example, if the plate 5 is of a resistive material or if it is connected to the ground plane 3 by way of a resistor (not shown) the plate may act as a microwave load. Similarly if the plate 5 is connected to the ground plane 3 by way of a semiconductor diode (not shown) the arrangement may be utilised as a microwave mixer or detector. Claims

1. A microwave component comprising an elongated member of solid dielectric material secured to a conductive substrate to act as a dielectric waveguide, wherein said member is cut transversely of the length thereof and a conductive member is secured to the cut face so as to interact with microwave energy in said dielectric waveguide.

2. A microwave component in accordance with Claim 1 wherein the conductive member is arranged at substantially forty five degrees to the length of said member.

3. A microwave component in accordance with Claim 1 or Claim 2 wherein the conductive member is connected directly to the conductive substrate.

4. A microwave component in accordance with Claim 2 wherein the conductive member is arranged to form a reflector to direct microwave energy from said elongated member into another member of dielectric material extending at right angles to said first member.

5. microwave component in accordance with Claim 1 wherein the conductive member is arranged to provide a predetermined value of resistance such as to act as a resistive load for said waveguide.

6. A microwave component in accordance with Claim 5 wherein said resistive load is matched to the characteristic impedance of said waveguide.

7. A microwave component in accordance with Claim 1 wherein the conductive member is connected to said conductive substrate by way of a semiconductor diode to form a microwave mixer or detector.

8. A microwave transmission path comprising an elongated body of a solid dielectric material secured to a substantially planar conductive substrate to act as a dielectric waveguide, wherein a waveguide bend between two substantially straight sections of said dielectric waveguide that are at an angle to one another in the plane of said planar substrate comprises a substantially planar conductor secured to a substantially planar surface of said dielectric material at the outside of said bend, said planar surface being substantially perpendicular to said planar substrate and disposed at substantially equai angles to said two sections of said waveguide.

9. A microwave transmission path substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawing.

10. A microwave directional coupler substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.