1. A voltage-tunable phase shifter comprising a conducting line and a ground electrode separated by a layer of dielectric material, the phase shifter configured to generate an electric field when a potential difference is applied between the conducting line and ground electrode, the electric field configured to change the phase of an electromagnetic signal propagating along the conducting line, wherein the ground electrode comprises graphene, and wherein the change in phase is dependent upon the strength of electric field and can be controlled by varying the potential difference between the conducting line and the ground electrode.
2. The phase shifter of claim 1, wherein the phase of the electromagnetic wave is dependent upon the quantum capacitance of the ground electrode, and wherein the applied electric field is configured to change the quantum capacitance of the ground electrode.
3. The phase shifter of claim 1, wherein the conducting line and ground electrode are configured such that the electric field is substantially perpendicular to the direction of propagation of the electromagnetic signal.
4. The phase shifter of claim 1, wherein the conducting line is a microstrip line.
5. The phase shifter of claim 1, wherein the electromagnetic signal has a frequency in the range of 30 kHz-3000 GHz.
6. The phase shifter of claim 1, wherein the phase shifter is formed on top of a flexible supporting substrate.
7. The phase shifter of claim 1, wherein the flexible supporting substrate is a flexible printed circuit board or a flexible region of a rigid-flex printed circuit board.
8. An apparatus comprising the phase shifter of claim 1.
9. The apparatus of claim 8, wherein the apparatus is one or more of a portable telecommunications device, a module for a portable telecommunications device, a cellular network server, a cellular network base station, and a phased array antenna.
10. A method for making a voltage-tunable phase shifter, the method comprising:
providing a layer of dielectric material;
providing a ground electrode comprising graphene on one surface of the dielectric material; and
providing a conducting line on the opposite surface of the dielectric material to produce a voltage-tunable phase shifter comprising a conducting line and a ground electrode separated by a layer of dielectric material, the phase shifter configured to generate an electric field when a potential difference is applied between the conducting line and ground electrode, the electric field configured to change the phase of an electromagnetic signal propagating along the conducting line, wherein the ground electrode comprises graphene, and wherein the change in phase is dependent upon the strength of electric field and can be controlled by varying the potential difference between the conducting line and the ground electrode.
11. The method of claim 10, wherein the ground electrode comprises a graphene film.
12. The method of claim 11, wherein the graphene film comprises one or more layers of graphene.
13. The method of claim 12, wherein at least one of the one or more layers of graphene is doped with one or more other materials.
14. The method of claim 11, wherein the graphene film is formed on the surface of the dielectric material by:
growing the graphene film on the surface of a copper foil;
adhering a thermal release layer to the graphene film;
removing the copper foil from the graphene film; and
pressing the graphene film against the surface of the dielectric material whilst applying sufficient heat to detach the thermal release layer from the graphene film.
15. The method of claim 14, wherein the graphene film is grown using chemical vapour deposition.
16. The method of claim 14, wherein the copper foil is removed using an etching process.
17. The method of claim 14, wherein one or more of the following steps are performed using roll-to-roll processing:
adhering the thermal release layer to the graphene film;
removing the copper foil from the graphene film; and
pressing the graphene film against the surface of the dielectric material whilst applying sufficient heat to detach the thermal release layer from the graphene film.
18. A method for changing the phase of an electromagnetic signal, the method comprising:
providing a voltage-tunable phase shifter comprising a conducting line and a ground electrode separated by a layer of dielectric material, the phase shifter configured to generate an electric field when a potential difference is applied between the conducting line and ground electrode, the electric field configured to change the phase of an electromagnetic signal propagating along the conducting line, wherein the ground electrode comprises graphene, and wherein the change in phase is dependent upon the strength of electric field and can be controlled by varying the potential difference between the conducting line and the ground electrode; and
applying a potential difference between the conducting line and ground electrode.
19. A computer program, recorded on a carrier, the computer program comprising computer code configured to perform the method of claim 10.
20. A computer program, recorded on a carrier, the computer program comprising computer code configured to perform the method of claim 18.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A disposable liquid absorbing cleaning pad for a butterfly mop, the butterfly mop including a pair of hingedly connected base plates, said disposable liquid absorbing cleaning pad comprising:
(a) a layer of a flexible open cell foam material made from melamine resin, wherein the layer of melamine resin is greater than or equal to \u215b inch in thickness,
(b) a layer of sponge material attached to said layer of a flexible open cell foam material made from melamine resin,
(c) a backing plate attached to the layer of sponge material wherein the backing plate comprises a first and second plate section connected by a hinge portion, and
(d) means for removably attaching said backing plate to said pair of base plates.
2. The disposable liquid absorbing cleaning pad for a butterfly mop of claim 1, wherein the means for removably attaching the backing plate to the mop comprise two tabs and one slot on each of the first and second plate sections.
3. The disposable liquid absorbing cleaning pad for a butterfly mop of claim 1 wherein the layer of a flexible open cell foam material made from melamine resin is greater than or equal to 716 inches in thickness.
4. The disposable liquid absorbing cleaning pad for a butterfly mop of claim 1 wherein the layer of sponge material is selected from the group consisting of polyester foam, natural sponges, polyurethane foam and cellulose.
5. The disposable liquid absorbing cleaning pad for a butterfly mop of claim 1, wherein the thickness of the layer of a flexible open cell foam material made from melamine resin is about 30% of the thickness of the cleaning pad.