Active antenna

About: Active antenna is a research topic. Over the lifetime, 2246 publications have been published within this topic receiving 26493 citations.

Integrated active antenna with simultaneous transmit-receive operation

Abstract: The authors present results for a novel two element active transmit-receive array using dual linear polarisation and sequential rotation. Each element includes an integrated oscillator and amplifier mounted on orthogonal edges of a square patch, such that transmit and receive paths are isolated and polarisation duplexed. The array gives in excess of 55 dB transmit-receive isolation at 3.77 GHz.

Reactively Steered Ring Antenna Array for Automotive Application

Abstract: A novel type of smart antenna, called a reactively steered ring antenna array (RSRAA), is proposed. The antenna features a conformal configuration with three overlapping one-wavelength ring elements. Directivity can be controlled by changing the values of variable reactance circuits that are embedded in the antenna. The antenna can be mounted on the windshield of an automobile without interfering with the view of the driver. An equivalent model of six dipole elements is derived from the original antenna configuration to enable simple calculation of directivity when a set of reactance values is given. The validity of the proposed equivalent model is confirmed by comparing simulation results calculated by the equivalent model and by the method of moments. Another simulation shows that the conventional reactance domain multiple signal classification algorithm can be applied to the proposed antenna while keeping the estimated direction-of-arrival number equal to the number of reactance circuits. In addition, the characteristics of an RSRAA, which is optimized at 2.4 GHz and is mounted on an automobile, are measured in an anechoic chamber, and directivity control is found to be implemented effectively.

Active antenna near field calibration method

Abstract: In a method of calibrating an active antenna the active elements of a transfer function matrix are measured using a near field probe for each radiating source of the antenna. The probe is placed in front of each source in succession and each source is excited in turn with the opposite phase and with all the other sources of the array excited normally. In the case of linear superposition of radiated fields, the measurements obtained by this method yield the elements of the transfer function matrix directly. This allows for phase and amplitude errors due to the components of the active antenna and for the effects of coupling between adjacent sources which modify the theoretical characteristics of the antenna. In the non-linear case the measurements are repeated and the matrix is obtained by iteration based on a comparison of the theoretical values used to control the antenna and the measured fields actually obtained. Measurements carried out on individual active modules prior to assembly of the antenna can be used in one variant of the method.

A large phased-array communications satellite

Abstract: A communications satellite is disclosed which uses distributed multiplexing and demultiplexing so as to minimize the amount of cabling needed between deployable phased array panels and a central processor. Signals are distributed from the active array panels to a member of active antenna elements. Each active antenna element has at least a radiating element, a modulator and a sample and hold circuit for forming modulation waveforms.

A wideband metamaterial-inspired compact antenna using embedded non-Foster matching

Abstract: Passive electrically small antennas have a small radiation resistance and a narrow bandwidth. In this paper, a new type of active antenna is reported in which an active circuit generating a non-Foster impedance is embedded in a metamaterial-inspired small antenna with an inherent sizable radiation resistance. This circuit interacts with the reactive elements of the antenna. The end result is a compact, broadband antenna which is well matched and has the potential for a high efficiency. In this process, the need for an active (or passive) step-up transformer for the radiation resistance is eliminated. This work opens up the possibility of utilizing non-Foster components embedded in metamaterial-based antenna structures to obtain efficient antennas by manipulating the current and field distribution in and around the antenna.