Ultra-wideband miniaturized omnidirectional antennas via multi-mode three-dimensional (3-d) traveling-wave (tw)

A multi-mode three-dimensional (3-D) low-profile traveling-wave (TW) omnidirectional antenna covering one or more ultra-wide bandwidths at high frequencies and separate distant low-frequency bands, and conforming to a surface of a platform, the 3-D TW antenna comprising:

• a conducting ground surface, which is in the form of a canonical shape, wherein the conducting ground surface conforms to a portion of the surface of a platform, the conducting ground surface being placed under the 3-D TW antenna and having a set of dimensions at least as large as those of the surface area of the 3-D TW antenna projected on the surface of the platform;
• a plurality of TW structures on top of the conducting ground surface, wherein each of the TW structure covers separate frequency band so as to enable the omnidirectional antenna to span in aggregate multiple bands over an ultra-wide range of frequencies, wherein the TW structures include at least one ultra-wideband low-profile 2-D surface-mode TW structure, and wherein the ultra-wideband low-profile 2-D surface-mode TW structure has a diameter less than λL/2, where λL is the free-space wavelength at the lowest frequency of operation of the 2-D surface-mode TW structures, the TW structures being adjacent to each other and stacked above the conducting ground surface;
• a frequency-selective coupler placed in between adjacent TW structures;
• at least one-dimensional (1-D) transmission-line antenna positioned adjacent to the plurality of TW structures, wherein the 1-D transmission-line antenna is coupled to a top side of the plurality of TW structures via a low-pass coupler to cover a plurality of separate distant low frequencies;
• and
• a feed network matching the impedances of the TW structures and the 1-D transmission-line antenna with the impedance of an external connector.

An ultra-wideband dual-band dual-feed cable comprising:

• an assembly of two concentric cables comprising an inner cable and an outer cable, the inner and outer cables sharing a common concentric cylindrical conductor shell, wherein the common concentric cylindrical conductor shell serves as the inner conductor of the outer cable and simultaneously serves as the outer conductor of the inner cable;
• wherein the outer cable covers a frequency band of a lower median frequency and the inner cable covers a frequency band of a higher median frequency;
• wherein each cable has two ends, one end connected to a device, the other end connected to an output terminal for connection to a common output device;
• and
• wherein the inner cable is connected to a first electrical device on one end and to a coaxial output terminal on the other end to convey a high-frequency output to the common output device, and the outer cable is connected to a second electrical device on one end and to the common output device on the other end to convey a low-frequency output to the common output device through a printed circuit board.

An omnidirectional antenna comprising:

• a conducting ground surface being positioned at a bottom side of the antenna,
• a plurality of traveling-wave (TW) structures on top of the conducting ground surface and covering a range of operating frequencies, wherein each TW structure covers a separate frequency band;
• a frequency-selective coupler placed in between adjacent TW structures;
• and
• a feed network matching an impedance of the TW structures with an impedance of an external connector.