Investigating a Phase Conjugate Mirror for Magnon-Based Computing by Alistair Inglis

Author:Alistair Inglis
Language: eng
Format: epub
ISBN: 9783030497453
Publisher: Springer International Publishing

A working PCB after fabrication is shown to varying degrees of magnification in Figs. 3.13 and 3.14. The former clearly shows the microwave feedlines, the meander structures and the grounding pads. In Fig. 3.13, the two parallel antennae running from top to bottom act as the ‘pumps’ and were placed apart, while the perpendicular structure (top) is the ‘probe’ and is offset by from the end of the pumps. This PCB was designed with meander legs that were wide and spaced apart. The boxed region in (a) is magnified and shown in more detail in (b). The latter contains a small boxed region which is shown in much more detail in Fig. 3.14.

A comparison of the finished PCB, with the AutoCAD drawing is shown in Fig. 3.14. The effect of side-etch is noticeable in the high-magnification image. The design has a width of and a spacing of , while the image clearly differs from this in a way that is not uniform. For example, the central leg is wide, while the outer legs are only wide. Indeed, the feedline at its narrowest point is only , which is less than the thickness of the copper cladding. The different rates of side-etch can be explained by how accessible the given feature is: the central leg is partially shielded on both sides by the outer legs, which are in turn only shielded on the side closest to the centre, while the feedline is fully exposed on both sides and suffers the most erosion. The narrow feedline is a good example of the rule of thumb when designing photomasks; that the feature after fabrication will be smaller than the design by twice the thickness of the copper laminate: .

Fig. 3.13Images of PCB after fabrication. The dashed box in (a) is shown under magnification in (b). The feedlines, meanders and grounding pads are all visible. The two parallel antennae act as pumps, while the single antenna on top is the probe. The region inside the small box in (b) is shown in much more detail in Fig. 3.14

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