Active antenna

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

Very Compact and Broadband Active Antenna for VHF Band Applications

Abstract: An active receiving antenna with small size consisting of a monopole loaded with a transistor bipolar is presented in this paper. A transistor is used in order to miniaturize the receiving active antenna size in VHF band. The vertical size of the structure is equal to λ/175, where λ is the wavelength at the lower frequency of the bandwidth. Despite the very small size of the antenna, the frequency bandwidth is very wide and the gain is suitable for FM application with sensitive receivers.

Portable radio equipment

Abstract: PURPOSE:To miniaturize a diversity receiver by using a microphone cord and an earphone cord as the 2nd antenna CONSTITUTION:The circuit of an antenna 2 is connected to an input circuit of a reception section 14 via an output circuit of a transmission section 13 or a diversity antenna changeover switch 12 by a transmission/reception changeover switch 11 When the reception wave intensity is lowered than the squelch level, the antenna changeover switch 12 is thrown from the position of the active antenna 2 to the diversity 2nd antenna 31 by an antenna switching output 15 generated from the reception 14 The microphone cord and the earphone cord are utilized as the diversity 2nd antenna 31

Link quality metric based antenna selection for transceivers

Abstract: A method and system for link quality metric based antenna selection for transceiver are disclosed. In one embodiment, a method for selecting an antenna from multiple antennas associated with a receiver, includes receiving multi-carrier modulated signals via a currently active antenna of the receiver, and estimating a predicted packet error rate (PER) associated with a current receive path of the receiver. The current receive path is used to process the multi-carrier modulated signals. The method further includes selecting a next antenna from the multiple antennas for forming a next receive path of the receiver based on the predicted PER and a packet error history associated with at least one previous receive path.

Reconfigurable antenna structure for RFID system applications using varactor-loading technique

Abstract: A novel method is presented for electrically tuning the frequency of a compact radio-frequency identification (RFID) tag antenna. A tuning circuit, comprising a radio frequency (RF) switch and discrete passive components, was completely integrated into the antenna element, which is thus free of DC wires. The low-profile printed antennas were fabricated together with the layouts of the DC control circuits and other RF/baseband circuit footprints. A surface-mounted varactor was applied as a frequency-tuning element at the proper places of the meandered slots in the compact antenna. Prototype designs showed that the in-band frequency (return loss < 10 dB) was tunable from 2.4 GHz to 2.8 GHz when the bias voltage varied from 4 V to 7 V. The impact of the tuning circuit on the antenna's return loss and radiation pattern were experimentally studied through comparison with the performance of a reference antenna not incorporating the tuning circuit. The proposed frequency tuning concept can be extended to more complex compact structures as well as other types of antennas to give enhanced electrical performance.

Piezoceramic actuated aperture antennas

Abstract: Recently, it has been demonstrated that aperture antennas can have their performance improved by utilizing PVDF as a shape controlling actuator. Since PVDF is a polymer with limited control authority, these antennas can only be employed in space based applications. This study examines more robust antenna structures devised of a thick metalized substrate with surface bonded piezoceramic (PZT) actuators. In this work, PZT-actuated adaptive antennas of cylindrical- cut shape are studied. First, the PZT-actuated antenna surface is modeled based on the classical curved beam theory and Newton's method. Second the Voltage vs. Deflection relationship is experimentally verified. Third, the resulting far field radiation pattern is simulated on computer.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.