Radio frequency isolator

Abstract

A Differential Phase Shift Isolator is disclosed. The isolator comprises: an input configured to receive a radio frequency signal; an output; a waveguide cavity, between the input and the output, wherein a trench is provided along a surface of the waveguide cavity, and a piece of phase shifting material having an edge. The piece is affixed to the surface of the waveguide cavity and the edge is bordered by the trench. The phase shifting material is arranged to provide a phase shift to the radio frequency signal received by the input.

Description

[0001] Radio Frequency Isolator

[0002] Technical Field

[0003] The present invention relates to isolators for use in high power communication systems, and in particular to differential phase shift isolator apparatus and their method of manufacture.

[0004] Background of the Invention

[0005] Isolators are devices which may be used in the transmission of microwave or radio frequency power, to ensure the transmission of power in only one direction. For example, they may be used in high-powered communication systems to isolate an antenna from an amplifier or other RF power source, e.g. in the E-band frequency range, and prevent signal reflection.

[0006] Differential phase shift isolators are arranged to divide an input microwave or radio frequency signal into two channels, and provide a phase offset between the two parts of the signal which are then recombined. The phase offset is such that, when the signals from the two channels are recombined, the power is directed towards the desired output. Any part of the signal that does not pass through the desired output or is reflected is directed to a termination or back towards the output, rather than towards the input.

[0007] To achieve the necessary phase offset, specific phase shifting materials are provided. The extent of the phase shift that is provided is highly dependent on the dimensions and positioning of this phase shifting material. Therefore, in order to attain necessary level of accuracy, it is important that the dimensions of the phase shifting materials are tightly controlled, and that they are precisely positioned within the isolator.

[0008] Summary of Invention

[0009] Embodiments of the present invention aim to address the above problems and others. Aspects of the disclosure are set out in the independent claims and optional features are set out in the dependent claims. Aspects of the disclosure may be provided in conjunction with each other, and features of one aspect may be applied to other aspects.

[0010] In an aspect, there is provided a differential Phase Shift Isolator comprising: an input configured to receive a radio frequency signal; an output; a waveguide cavity, between the input and the output, wherein a trench is provided along a surface of the waveguide cavity, and a piece of phase shifting material having an edge, wherein the piece is affixed to the surface of the waveguide cavity, wherein the edge is bordered by the trench, and wherein the phase shifting material is arranged to provide a phase shift to the radio frequency signal received by the input.

[0011] The piece may be affixed to the surface of the waveguide cavity using an adhesive. The adhesive may be an epoxy resin. The trench may be less than 0.02mm deep. The trench may be more than 0.01 mm deep. The trench may have a side wall that is perpendicular to the surface onto which the piece is affixed. The phase shifting material may be a ferrite, (a ferrimagnetic material), such as a millimetre-wave ferrite e.g. TT2-111. Additionally or alternatively, the phase shifting material may be a dielectric material, such as the dielectric D6.

[0012] The waveguide cavity may comprise a first channel and a second channel, and the piece may be provided in the first channel. The second channel may comprise a second piece comprising a second phase shifting material and a third piece comprising a third phase shifting material. The second phase shifting material may be a ferrite, and the third phase shifting material may be a dielectric. The first piece may be configured to provide a phase shift of 90° to the signal passing through the first channel. The second piece may be configured to provide a phase shift of 90° to the signal passing through the second channel. The third piece may be configured to provide a phase shift of 90° to the signal passing through the second channel. The second piece and the third piece may therefore provide a total phase shift of 180° to the signal passing through the second channel.

[0013] The isolator may comprise one or more terminations at which power is dissipated and / or at which power is reflected. The isolator may comprise two, three, fourorfive terminations, or more. The isolator may be configured such that a radio frequency signal received by the input is split between the first channel and the second channel, e.g. equally split. For example, the isolator may comprise a splitter configured to split the signal between the first and second channel, e.g. said splitter may be arranged between the input and the first and second channels. The splitter may be configured to provide a phase shift to the signal provided to the first channel and / or the signal provided to the second channel, e.g. such that the signal provided to the second channel is offset (e.g. lags) the signal provided to the first channel, e.g. by 90°. The splitter may comprise four ports. The splitter may be a riblet coupler.

[0014] The isolator may further comprise a combiner. The combiner may comprise four ports, e.g. two input ports and two output ports. A first input port may be arranged to receive a first signal from the first channel and a second input port may be arranged to receive a second signal from the second channel. The combiner may be configured such that, in the event that the phase difference between the first signal and the second signal is 180°, a single (e.g. combined) signal is directed entirely to a first output port. The combiner may be configured such that, in the event that the phase difference between the first signal and the second signal is not exactly 180°, the output signal is divided between the first output port and the second output port. The first output port may be configured to direct a signal to an output of the isolator. The second output port may be configured to direct a signal to a termination. The combiner may be a second riblet coupler.

[0015] In another aspect there is provided a method for the manufacture of a differential phase shift isolator, the method comprising: providing a trench in a surface of a waveguide cavity, to define an area for placement of a phase shifting material; adding a layer of adhesive to the area, wherein an edge of the layer of adhesive is bordered by the trench; placing a piece comprising the phase shifting material onto the adhesive.

[0016] The method may further comprise a step of trimming the piece using a laser such that an edge of the piece is bordered by the trench.

[0017] Adding the adhesive to the surface of the waveguide may comprise adding the adhesive as a series of microdroplets. Placing a piece may comprise placing one or more of the first, second and / or third pieces onto the adhesive. Placing a piece may comprise placing a plurality of phase shifting materials onto the adhesive.

[0018] Providing a trench in the surface of the waveguide cavity may comprise cutting the surface with a laser.

[0019] Providing a trench may comprise providing a plurality of trenches in the surface of the waveguide cavity. For example, the method may comprise providing a first trench and a second trench in the surface, wherein the surface between the first and second trench is arranged to receive the piece of phase shifting material. The distance between the first trench and the second trench may be substantially the same as the width of the piece of phase shifting material and / or a desired width of said piece.

[0020] Brief Description of Figures

[0021] Some examples of the present disclosure will now be described with reference to the figures, in which:

[0022] Figure 1 shows a diagram of an example Differential Phase Shift Isolator;

[0023] Figure 2 shows a cross-sectional view of the Differential Phase Shift Isolator of Figure 1 ; Figure 3 shows a close-up view of a waveguide channel of the differential phase shift isolator of figure 2;

[0024] Figure 4 shows a perspective view of an example waveguide channel;

[0025] Figure s shows a flow chart illustrating a method of construction for a waveguide channel;

[0026] In the drawings like reference numerals are used to indicate like elements.

[0027] Detailed Description

[0028] The present disclosure relates to Differential Phase Shift Isolators in which a differential phase-shift is performed by pieces, e.g. square or rectangular tiles, of phase-shifting material that extend along a waveguide and are affixed to the interior surface of the waveguide. Trenches are provided in the surface of the waveguide, to enable accurate and precise positioning of the pieces. Figure 1 shows a top view of a Differential Phase Shift Isolator 1 . The isolator 1 comprises an input 100, which is configured to obtain power signals from an RF power source, such as a solid-state power amplifier or a travelling wave tube amplifier. The input 100 provides the signal to a power splitter 101 , which in figure 1 takes the form of a riblet coupler with four . The splitter 101 comprises four ports, and is arranged to obtain the input signal at a first port, and to split the signal equally between second and third output ports, which respectively provide a first signal to a first waveguide channel 102 and a second signal to a second waveguide channel 103. The splitter 101 is further arranged to provide a phase shift between the signal provided to the first channel 102 and the signal provided to the second channel 103, such that the phase of the first signal lags the second by 90°.

[0029] The first waveguide channel 102 contains a first plurality of rectangular ferrimagnetic “ferrite” tiles 104. The first plurality of ferrite tiles 104 is arranged to provide a phase shift of 90° to the first signal which passes through the first waveguide channel 102.

[0030] The second waveguide channel 103 contains a second plurality of ferrite tiles 105 and a plurality of dielectric tiles 106. The second plurality of ferrite tiles 105 is arranged to provide a phase shift of 90° to the second signal. The plurality of dielectric tiles 106 is arranged to provide a phase shift of 90° to the second signal. The second waveguide channel 103 is thereby arranged to provide a total phase shift of 180° to the second signal which passes through it.

[0031] The first waveguide channel 102 and the second waveguide channel 103 each comprise an output which is configured to provide the signal to a respective input of a power combiner 107. The power combiner 107 may be a second Riblet coupler comprising four ports.

[0032] The phase shifts provided by each of the splitter 101 , the first waveguide channel 102 and the second waveguide channel 103 are such that that when the signals reach the power combiner, there is a phase difference of 180° between the first and second signals. The power combiner 107, comprises two input ports and two output ports. The power combiner 107 is configured such that, when the phase difference between the two signals is 180°, the power combiner 107 outputs a single signal to the output 108. When the phase difference is not exactly 180°, the output signal is divided between the two output ports of the power combiner, with a portion provided to the output 108 and another portion directed towards a termination 109, where the signal may be dissipated.

[0033] Some portion of the output signal may be reflected back through the waveguide channels 102, 103. In this case, due to the configuration of the power combiner 107, the power splitter 101 and the phase shifting materials in the waveguide channels 102, 103, the signal is directed by the power splitter towards further terminations 110 to 113. At each of the terminations the signal may be dissipated and / or be reflected back towards the output 108 via the power splitter 101 , waveguide channels 102, 103, and the power combiner 107.

[0034] The power splitter 101 also has an output to a second primary termination channel 116 that leads to a first secondary termination channel 114 that leads to a second termination 110 and a third termination 111 , and a second secondary termination channel that leads to a fourth termination 112 and a fifth termination 113. This is so that any power reflected back toward the input 100 can be dissipated, as the power splitter 101 works the same way in this direction as the power combiner 107 does in the other.

[0035] Figure 2 illustrates a cross section of the Differential Phase Shift Isolator 1 across the plane A- A that is shown in Figure 1. Here, cross sections of the first waveguide channel 102 and the second waveguide channel 103 can be seen, with the firstwaveguide channel

[0036] 102 containing a first plurality of ferrite tiles 104, and the second waveguide channel 103 containing a second plurality of ferrite tiles 105 and a plurality of dielectric tiles 106. As shown, the waveguide channels 102, 103, are formed from recesses into the surface of the isolator 1 , and run as tracks that are parallel to each other between the power splitter 101 and the power combiner 107.

[0037] In order for the above phase shifting effects to be realised, it is necessary for the position of the ferrite and dielectric tiles discussed to be precisely positioned and affixed in the channels 102, 103.

[0038] Figure 3 shows a close-up view of the cross-section of the second waveguide channel

[0039] 103 shown as region B in Figure 2. Figure 3 shows an end face of one of the plurality of ferrite tiles 105, and one of the plurality of dielectric tiles 106. Each of the ferrite tiles 105 are affixed to the surface of the second waveguide channel 103 with a first adhesive layer 300 that is arranged between the tiles 105 and the surface of the channel 103. The dielectric tiles 106 are similarly affixed to the surface of the second waveguide channel 103 with a second adhesive layer 301 arranged between the tiles 106 and the surface of the channel 103. The first and second adhesive layers 300, 301 may be provided by an epoxy resin.

[0040] The ferrite tiles 105 are bordered on each of their side faces by a first trench 302 and a second trench 303. There plurality of dielectric tiles 106 are similarly bordered by a third trench 304 and a fourth trench 305 each of their side faces. The trenches 302 to 305 are provided as small recesses in the surface of the waveguide channel 103, which run parallel to each other and to the sides of the waveguide channel. The first and second trenches 302, 303 thereby define a track on the surface of the waveguide channel 10 in which the ferrite tiles 105 can be positioned, and the third and fourth trenches 304, 305, thereby define a track in which the dielectric tiles can be positioned.

[0041] Figure 4 shows a perspective view of the first waveguide channel 102, in which the plurality of ferrite tiles 105 have been affixed to the channel 102 between the first trench 302 and the second trench 303, using the adhesive layer 300. The third trench 304 and the fourth trench 304 are also shown prior to affixing the dielectric tiles to the channel 102.

[0042] The trenches 302 to 305 have a square or rectangular cross section. As such, each trench 302 to 305 has a pair of opposing side walls and a base extending therebetween. As shown, the ferrite tiles 105 each have a side face 110 which is aligned with a side wall of the trenches 302, 303. The same applies with respect to the dielectric tiles and trenches

[0043] 304, 305, when they are affixed to the waveguide channel 102. The width of each of the tiles 105 106 therefore corresponds to the width of the track defined between each of the pairs of trenches 302, 303 and 304, 305. Each of the plurality of tiles 105 and 106 may be laid end to end along the track defined between the pairs of trenches 302, 303 and 304,

[0044] 305. Each of the tracks may have a width of approximately 0.05 mm. Each of the tiles 105, 106 may also have a width of approximately 0.05mm, and may also have a length of approximately 0.05mm. Each of the trenches 302 to 305 may be between 0.01 mm and 0.02mm deep.

[0045] Figure 5 shows a flow chart for a method 500 of manufacturing of the differential phase shift isolator, including several steps. At a first step 501 a trench is provided in a surface of a waveguide cavity, to define an area for placement of a phase shifting material, such as the tiles discussed above. At this step 501 , further trenches may also be provided in the surface, e.g. to provide the plurality of trenches described above, although it will be appreciated that this is not essential. The trench can be provided in the surface using a laser. A second step 502 involves adding a layer of adhesive such as epoxy to the area, wherein an edge of the layer of adhesive is bordered by the trench. The adhesive can be added as a series of microdroplets. A third step 503 involves placing a piece comprising the phase shifting material onto the adhesive 502. It will be appreciated that the step of placing a piece may include placing a plurality of tiles onto the adhesive, such as the tiles of ferrite and / or dielectric described above.

[0046] In certain examples it may be that the piece of phase shifting material is larger, e.g. wider, than the area in which it is to be placed. In such examples the piece is trimmed, e.g. using a laser, and the method includes an additional step (not shown) of trimming the piece with a laser.

[0047] It will be appreciated from the discussion above that the examples shown in the figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein.

[0048] As will be appreciated by the skilled reader in the context of the present disclosure, each of the examples described herein may be implemented in a variety of different ways. Any feature of any aspects of the disclosure may be combined with any of the other aspects of the disclosure. For example, method aspects may be combined with apparatus aspects, and features described with reference to the operation of particular elements of apparatus may be provided in methods which do not use those particular types of apparatus. In addition, each of the features of each of the examples is intended to be separable from the features which it is described in combination with, unless it is expressly stated that some other feature is essential to its operation. Each of these separable features may of course be combined with any of the other features of the examples in which it is described, or with any of the other features or combination of features of any of the other examples described herein. Furthermore, equivalents and modifications not described above may also be employed without departing from the invention. Other examples and variations of the disclosure will be apparent to the skilled addressee in the context of the present disclosure.

Claims

Claims:

1. A Differential Phase Shift Isolator comprising;An input configured to receive a radio frequency signal;An output;A waveguide cavity, between the input and the output, wherein a trench is provided along a surface of the waveguide cavity, and;A piece of phase shifting material having an edge, wherein the piece is affixed to the surface of the waveguide cavity, wherein the edge is bordered by the trench, and wherein the phase shifting material is arranged to provide a phase shift to the radio frequency signal received by the input.

2. The Differential Phase Shift Isolator of claim 1 , wherein the piece is affixed to the surface of the waveguide cavity using an adhesive.

3. The Differential Phase Shift Isolator of claim 2, wherein the adhesive is an epoxy resin.

4. The Differential Phase Shift Isolator of any previous claim, wherein the trench is less than 0.02mm deep.

5. The Differential Phase Shift Isolator of any previous claim, wherein the trench is more than 0.01 mm deep.

6. The Differential Phase Shift Isolator of any previous claim, wherein the trench has a side wall that is perpendicular to the surface onto which the piece is affixed.

7. The Differential Phase Shift Isolator of any previous claim, wherein the phase shifting material is a ferrite.

8. The Differential Phase Shift Isolator of any of claims 1-6, wherein the phase shifting material is a dielectric material.

9. The Differential Phase Shift Isolator of any of claims 1-8, wherein the waveguide cavity comprises a first channel and a second channel, wherein the piece is provided in the first channel.

10. The Differential Phase Shift Isolator of claim 9, wherein the second channel comprises a second piece comprising a second phase shifting material and a third piece comprising a third phase shifting material.11 . The Differential Phase Shift Isolator of claim 10, wherein the second phase shifting material is a ferrite, and the third phase shifting material is a dielectric.

12. The Differential Phase Shift Isolator of claim 11 , wherein the isolator is configured such that the radio frequency signal received by the input is split between the first channel and the second channel.

13. A method for the manufacture of a differential phase shift isolator, the method comprising:Providing a trench in a surface of a waveguide cavity, to define an area for placement of a phase shifting material;Adding a layer of adhesive to the area, wherein an edge of the layer of adhesive is bordered by the trench;Placing a piece comprising the phase shifting material onto the adhesive.

14. The method of claim 13, further comprising a step of trimming the piece using a laser such that an edge of the piece is bordered by the trench.

15. The method of any of claims 13-14, wherein the adhesive is an epoxy resin.

16. The method of any of claims 13-15, wherein adding the adhesive to the surface of the waveguide comprises adding the adhesive as a series of microdroplets.

17. The method of any of claims 13-16, wherein the phase shifting material is a ferrite.

18. The method of any of claims 13-16, wherein the phase shifting material is a dielectric material.

19. The method of any of claims 13 to 18, wherein the trench has a side wall that is perpendicular to the surface onto which the piece is affixed.

20. The method of any of claims 13 to 19, wherein providing a trench in the surface of the waveguide cavity comprises cutting the surface with a laser.

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