Abstract: An antenna configured to receive radiation at global navigation satellite system (GNSS) frequencies includes a substrate, a frontside patch arranged on a front side of the substrate, and a metamaterial ground plane. The metamaterial ground plane includes a plurality of backside patches and a cavity. The plurality of backside patches include a center backside patch surrounded in a radial direction by a plurality of intermediate backside patches. The center backside patch and the plurality of intermediate backside patches are arranged in a pattern that provides circular symmetry with respect to a center of the antenna. The cavity is coupled to the substrate, and the plurality of intermediate backside patches are electrically isolated from the cavity.

Abstract: A parasitically-coupled dual-band patch antenna is described. The antenna includes an inner conductor having one or more feed holes. The antenna also includes an outer conductor surrounding the inner conductor in a radial direction. The antenna further includes one or more feeds each having a vertical portion that passes through the feed holes and a horizontal portion that extends in an outward direction from the feed holes toward the outer conductor. The feeds are conductively connected to the outer conductor. The horizontal portion of each of the feeds is separated from and is conductively disconnected from a top surface of the inner conductor.

Abstract: A dual-band patch antenna is described. The antenna includes a ground plane. The antenna also includes an inner conductor disposed above the ground plane. The inner conductor forms a high-frequency patch for receiving radio waves at an upper frequency band. The antenna further includes an outer conductor surrounding the inner conductor. The outer conductor and the inner conductor collectively form a low-frequency patch for receiving radio waves at a lower frequency band. The antenna further includes a filter disposed between the inner conductor and the outer conductor. The filter is configured to at least partially block electrical signals at the upper GNSS frequency band and to let pass electrical signals at the lower GNSS frequency band.

Abstract: An antenna configured to receive radiation at global navigation satellite system (GNSS) frequencies includes a substrate, a frontside patch arranged on a front side of the substrate, and a metamaterial ground plane. The metamaterial ground plane includes a plurality of backside patches and a cavity. The plurality of backside patches include a center backside patch surrounded in a radial direction by a plurality of intermediate backside patches. The center backside patch and the plurality of intermediate backside patches are arranged in a pattern that provides circular symmetry with respect to a center of the antenna. The cavity is coupled to the substrate, and the plurality of intermediate backside patches are electrically isolated from the cavity.

Abstract: An antenna configured to receive radiation at global navigation satellite system (GNSS) frequencies includes a substrate, a frontside patch arranged on a front side of the substrate, and a metamaterial ground plane. The metamaterial ground plane includes a plurality of backside patches and a cavity. The plurality of backside patches include a center backside patch surrounded in a radial direction by a plurality of intermediate backside patches. The center backside patch and the plurality of intermediate backside patches are arranged in a pattern that provides circular symmetry with respect to a center of the antenna. The cavity is coupled to the substrate, and the plurality of intermediate backside patches are electrically isolated from the cavity.

Abstract: An antenna configured to receive radiation at global navigation satellite system (GNSS) frequencies includes a substrate, a frontside patch arranged on a front side of the substrate, and a metamaterial ground plane. The metamaterial ground plane includes a plurality of backside patches and a cavity. The plurality of backside patches include a center backside patch surrounded in a radial direction by a plurality of intermediate backside patches. The center backside patch and the plurality of intermediate backside patches are arranged in a pattern that provides circular symmetry with respect to a center of the antenna. The cavity is coupled to the substrate, and the plurality of intermediate backside patches are electrically isolated from the cavity.

Abstract: An antenna includes a dielectric substrate, a circular patch overlying the dielectric substrate, and a metamaterial ground plane. One or more antenna feeds are coupled to the circular patch. The antenna feeds may include impedance transformers. The metamaterial ground plane includes a plurality of conductive patches and a ground plane. The conductive patches are arranged along a first plane below the circular patch and are separated from the circular patch by at least the dielectric substrate. The conductive patches are arranged in a pattern that provides circular symmetry with respect to a center of the circularly polarized antenna. The ground plane is arranged along a second plane and is electrically coupled to at least a first portion of the conductive patches. One or more of the conductive patches and the ground plane are coupled to ground.

Abstract: An antenna includes a dielectric substrate, a circular patch overlying the dielectric substrate, and a metamaterial ground plane. One or more antenna feeds are coupled to the circular patch. The antenna feeds may include impedance transformers. The metamaterial ground plane includes a plurality of conductive patches and a ground plane. The conductive patches are arranged along a first plane below the circular patch and are separated from the circular patch by at least the dielectric substrate. The conductive patches are arranged in a pattern that provides circular symmetry with respect to a center of the circularly polarized antenna. The ground plane is arranged along a second plane and is electrically coupled to at least a first portion of the conductive patches. One or more of the conductive patches and the ground plane are coupled to ground.

Abstract: An antenna includes a dielectric substrate, a circular patch overlying the dielectric substrate, and a metamaterial ground plane. One or more antenna feeds are coupled to the circular patch. The antenna feeds may include impedance transformers. The metamaterial ground plane includes a plurality of conductive patches and a ground plane. The conductive patches are arranged along a first plane below the circular patch and are separated from the circular patch by at least the dielectric substrate. The conductive patches are arranged in a pattern that provides circular symmetry with respect to a center of the circularly polarized antenna. The ground plane is arranged along a second plane and is electrically coupled to at least a first portion of the conductive patches. One or more of the conductive patches and the ground plane are coupled to ground.

Abstract: An antenna configured to receive radiation at global navigation satellite system (GNSS) frequencies includes a dielectric substrate, a circular patch overlaying the dielectric substrate, one or more impedance transformers, and a metamaterial ground plane. The metamaterial ground plane includes a plurality of conductive patches and a cavity. The conductive patches are arranged along a first plane on a backside of the dielectric substrate and are separated from the circular patch by the dielectric substrate. The cavity includes a ground plane and a conductive fence. The ground plane is arranged along a second plane below the first plane. The ground plane is electrically coupled to at least a first portion of the plurality of conductive patches by conductive vias. The conductive fence is spaced from the backside of the dielectric substrate and from the plurality of conductive patches by a gap.

Abstract: An antenna configured to receive radiation at global navigation satellite system (GNSS) frequencies includes a dielectric substrate, a circular patch overlaying the dielectric substrate, one or more impedance transformers, and a metamaterial ground plane. The metamaterial ground plane includes a plurality of conductive patches and a cavity. The conductive patches are arranged along a first plane on a backside of the dielectric substrate and are separated from the circular patch by the dielectric substrate. The cavity includes a ground plane and a conductive fence. The ground plane is arranged along a second plane below the first plane. The ground plane is electrically coupled to at least a first portion of the plurality of conductive patches by conductive vias. The conductive fence is spaced from the backside of the dielectric substrate and from the plurality of conductive patches by a gap.

Abstract: An antenna configured to receive radiation at global navigation satellite system (GNSS) frequencies includes a dielectric substrate, a circular patch overlaying the dielectric substrate, one or more impedance transformers, and a metamaterial ground plane. The metamaterial ground plane includes a plurality of conductive patches and a cavity. The conductive patches are arranged along a first plane on a backside of the dielectric substrate and are separated from the circular patch by the dielectric substrate. The cavity includes a ground plane and a conductive fence. The ground plane is arranged along a second plane below the first plane. The ground plane is electrically coupled to at least a first portion of the plurality of conductive patches by conductive vias. The conductive fence is spaced from the backside of the dielectric substrate and from the plurality of conductive patches by a gap.

Abstract: An antenna configured to receive radiation at global navigation satellite system (GNSS) frequencies includes a dielectric substrate, a circular patch overlaying the dielectric substrate, one or more impedance transformers, and a metamaterial ground plane. The metamaterial ground plane includes a plurality of conductive patches and a cavity. The conductive patches are arranged along a first plane on a backside of the dielectric substrate and are separated from the circular patch by the dielectric substrate. The cavity includes a ground plane and a conductive fence. The ground plane is arranged along a second plane below the first plane. The ground plane is electrically coupled to at least a first portion of the plurality of conductive patches by conductive vias. The conductive fence is spaced from the backside of the dielectric substrate and from the plurality of conductive patches by a gap.

Abstract: An antenna includes a dielectric substrate, a circular patch overlying the dielectric substrate, and a metamaterial ground plane. One or more antenna feeds are coupled to the circular patch. The antenna feeds may include impedance transformers. The metamaterial ground plane includes a plurality of conductive patches and a ground plane. The conductive patches are arranged along a first plane below the circular patch and are separated from the circular patch by at least the dielectric substrate. The conductive patches are arranged in a pattern that provides circular symmetry with respect to a center of the circularly polarized antenna. The ground plane is arranged along a second plane and is electrically coupled to at least a first portion of the conductive patches. One or more of the conductive patches and the ground plane are coupled to ground.

Abstract: A connected-slot antenna includes a dielectric substrate, a circular patch overlying the dielectric substrate, and a first conductive ring surrounding the circular patch and overlying the dielectric substrate. The first conductive ring is isolated from the circular patch by a first connected slot. At least four feeds are coupled to the circular patch. Each of the at least four feeds are spaced from adjacent ones of the at least four feeds by approximately equal angular intervals. A metamaterial ground plane includes a plurality of conductive patches and a ground plane. The plurality of conductive patches are separated from the circular patch and the first conductive ring by at least the dielectric substrate. The ground plane is electrically coupled to at least a first portion of the plurality of conductive patches. One or more of the plurality of conductive patches and the ground plane are coupled to ground.

Abstract: A microwave stethoscope measurement method and sensor design employ a microwave transmission sensor and a microwave reception sensor placed on a patient's chest in spaced-apart side-by-side configuration for monitoring patient vital signs, lung water content and other critical measurements. The side-by-side sensors are spaced apart a separation distance of about 1-3 cm in lateral chest orientation. The sensors may be formed with a textile fabric for wearer comfort and to improve contact with the patient's skin. The microwave sensor measurements are digitally processed using a modified short time Fourier Transform (STFT) spectrum windowed-averaged algorithm. Output data extracted from the microwave sensor measurements may be transmitted wirelessly to a mobile device such as a smartphone for remote monitoring of the patient's medical condition.

Abstract: A connected-slot antenna includes a dielectric substrate, a circular patch overlying the dielectric substrate, and a first conductive ring surrounding the circular patch and overlying the dielectric substrate. The first conductive ring is isolated from the circular patch by a first connected slot. At least four feeds are coupled to the circular patch. Each of the at least four feeds are spaced from adjacent ones of the at least four feeds by approximately equal angular intervals. A metamaterial ground plane includes a plurality of conductive patches and a ground plane. The plurality of conductive patches are separated from the circular patch and the first conductive ring by at least the dielectric substrate. The ground plane is electrically coupled to at least a first portion of the plurality of conductive patches. One or more of the plurality of conductive patches and the ground plane are coupled to ground.

Abstract: A microwave stethoscope measurement method and sensor design employ a microwave transmission sensor and a microwave reception sensor placed on a patient's chest in spaced-apart side-by-side configuration for monitoring patient vital signs, lung water content and other critical measurements. The side-by-side sensors are spaced apart a separation distance of about 1-3 cm in lateral chest orientation. The sensors may be formed with a textile fabric for wearer comfort and to improve contact with the patient's skin. The microwave sensor measurements are digitally processed using a modified short time Fourier Transform (STFT) spectrum windowed-averaged algorithm. Output data extracted from the microwave sensor measurements may be transmitted wirelessly to a mobile device such as a smartphone for remote monitoring of the patient's medical condition.