A method and apparatus are provided for nulling a radio frequency (RF) beam for a high-altitude platform (HAP). A transmitter generates an RF signal. A primary antenna system generates an RF beam based on the RF signal. One or more processors determine a result indicating whether to modify the RF beam. When the result indicates to modify the RF beam, a detachable nulling subassembly generates nulling signals based on the RF signal to modify the RF beam generated by the primary antenna system.

A single frequency, or very narrow frequency band, microwave imaging system is described herein. A microwave imaging system can include an array transmitter; an array receiver; and a computing device that receives signals detected from the array receiver, transforms the signals received by the array receiver into independent spatial measurements, constructs an image using the independent spatial measurements, and outputs a reconstructed image. The array transmitter and the array receiver may each have a plurality of independently controllable metasurface resonant elements.

A system and method for nulling or suppressing interfering signals directed toward moving platforms based, at least in part, on dynamic motion data of the moveable platform is provided. The system may be an interference nulling system carried by a moveable platform and may include an antenna array including two or more antenna elements that generates at least one initial steerable null radiation pattern, dynamic motion data logic that determines dynamic motion data of the moveable platform; and update logic that updates the at least one initial steerable null radiation pattern based, at least in part, on the dynamic motion data. The at least one updated steerable null radiation pattern is directed toward a direction from which interfering signals are being transmitted from an interfering signal source.

A technique is described where the switch and/or tunable control circuit for use with an active multi-mode antenna is positioned remote from the antenna structure itself for integration into host communication systems. Electrical delay and impedance characteristics are compensated for in the design and configuration of transmission lines or parasitic elements as the active multi-mode antenna structure is positioned in optimal locations such that significant electrical delay is introduced between the RF front-end circuit and multi-mode antenna. This technique can be implemented in designs where it is convenient to locate switches in a front-end module (FEM) and the FEM is located in vicinity to the transceiver.

Described is an antenna structure including a first antenna configured to emit electromagnetic radiation having a first operational frequency band; a second antenna configured to emit electromagnetic radiation having a second operational frequency band; and wherein the second antenna comprises an inductive element configured to inhibit interference of the second antenna with the electromagnetic radiation emitted from the first antenna.

A base station system may include at least one base station radio, at least one antenna, the at least one antenna including at least a first antenna comprising a linear array of antenna elements arranged in a vertical plane, and at least a one antenna distribution network for distributing radio frequency (RF) signals as component RF signals across the linear array of antenna elements of the at least the first antenna to form at least one beam in an elevation plane. In one example, the at least the one antenna feed network applies amplitude and phase weights to the component RF signals, wherein the amplitude and phase weights are selected to minimize RF coupling between the at least the first antenna and passive intermodulation sources in a near-field of the at least the first antenna.

Methods of mitigating interference to a Mobile Satellite Service (MSS) satellite from terrestrial Broadband Wireless Access (BWA) base stations are provided. A method includes receiving, at the terrestrial BWA base station, a pilot signal on a satellite downlink frequency, and adjusting terrestrial BWA communication on a satellite uplink frequency that corresponds to the satellite downlink frequency, responsive to the pilot signal.

A communication system utilizing reconfigurable antenna systems is described where beam steering and null forming techniques are incorporated to limit the region or volume available for communication with client devices. The communication system described restricts communication to defined or desired area and degrades signal strength coverage outside of a prescribed region. An algorithm is used to control the antenna system to monitor and control antenna system performance across the service area. This antenna system technique is applicable for use in communication systems such as a Local Area Network (LAN), cellular communication network, and Machine to Machine (M2M).

A modal antenna array is described where modal antenna elements capable of generating multiple radiation modes are used to form array radiation patterns. Nulls in the array radiation pattern can be formed and positioned by proper modal antenna element mode selection, with these nulls used to provide interference suppression or mitigation. The shift in array radiation pattern maxima generated by modal element mode selection can be used to improve communication system link quality by optimizing array radiation pattern characteristics. Specifically, a ring or circular array configuration is described where a simplified common feed port can be implemented to feed multiple modal antenna elements used to form the array. A switch can be used to connect or disconnect one modal element from the array, with this feature providing additional unique array beam states. The modal array can be commanded via a look-up table or algorithm.

An antenna assembly may include a right hand circularly polarized (RHCP) antenna, a left hand circularly polarized (LHCP) antenna, an RF nuller operably coupling the RHCP antenna and LHCP antenna to a difference element, and a digital nuller operably coupled to the difference element.