Reflectarray antenna

A reflectarray including a plurality of antenna elements, each antenna element including:

• a patch of electrically conductive material for reflecting an electromagnetic field;
• a dielectric substrate providing an RF ground;
• first and second phase control lines of electrically conductive material arranged to interact with electromagnetic radiation with a first polarisation;
• a first binary switching device having an ON or OFF state disposed between the patch and ground, and configured to selectively electrically couple the patch to ground via the first phase control line;
• a second binary switching device having an ON or OFF state disposed between the patch and ground, and configured to selectively electrically couple the patch to ground via the second phase control line;
• wherein the first switching device is a first PIN diode having a diode direction from the patch to the ground;
• and the second switching device is a second PIN diode having a diode direction from the ground to the patch;
• a single DC bias input electrically coupled to the patch and configurable to different discrete voltage levels for selectively controlling the states of the switching devices;
• wherein selective operation of the first and second binary switching devices by means of the DC bias input provides phase control of electromagnetic radiation dependent on the state of the switching devices configured to provide three phase states for electromagnetic radiation for each polarisation and frequency.

A method of operating an antenna element, the antenna element including:

• a patch of electrically conductive material for reflecting an electromagnetic field;
• a dielectric substrate providing an RF ground;
• first and second phase control lines of electrically conductive material arranged to interact with electromagnetic radiation with a first polarisation;
• a first binary switching device having an ON or OFF state disposed between the patch and ground, and configured to selectively electrically couple the patch to ground via the first phase control line;
• a second binary switching device having an ON or OFF state disposed between the patch and ground, and configured to selectively electrically couple the patch to ground via the second phase control line;
• wherein the first switching device is a first PIN diode having a diode direction from the patch to the ground;
• and the second switching device is a second PIN diode having a diode direction from the ground to the patch;
• a single DC bias input electrically coupled to the patch and configurable to different discrete voltage levels for selectively controlling the states of the switching devices;
• wherein selective operation of the first and second binary switching devices by means of the DC bias input provides phase control of electromagnetic radiation dependent on the state of the switching devices configured to provide three phase states for electromagnetic radiation for each polarisation and frequency;
• the method including the steps of:
• controlling a DC bias signal to the DC bias input to provide a desired reflection phase control for electromagnetic radiation with the first polarisation at a first frequency and optionally also for electromagnetic radiation with a second polarisation at a second frequency.