Adaptive Base Station Antennas Research Articles

Automatic calibration method using transmitting signals of an adaptive array for TDD systems

Adaptive arrays are especially effective in reducing cochannel interference and increasing channel capacity in time-division duplex (TDD) mobile communication systems because, ideally, the optimum pattern formed in the receiving mode can be applied to the transmitting pattern. However, since the radiation pattern of the adaptive array is generally formed on a baseband, the amplitude and phase errors must be calibrated between the branches of the array due to individual differences in the radio frequency (RF) devices of the receivers and transmitters. Moreover, since these errors change over time due to temperature variations, real-time calibration is required. This correspondence proposes an automatic calibration method using transmitting signals (ACT) for adaptive base station antennas that is suitable for TDD communication systems, i.e., it enables real-time calibration. The effectiveness of the proposed calibration method is demonstrated using an experimental adaptive array testbed.

The performance enhancement of multibeam adaptive base-station antennas for cellular land mobile radio systems

The problem of meeting the proliferating demands for mobile telephony within the confinement of the limited radio spectrum allocated to these services is addressed. A multiple-beam adaptive base-station antenna is proposed as a major system component in an attempt to solve this problem. The approach is demonstrated by employing an antenna array capable of resolving the angular distribution of the mobile users as seen at the base-station site, and then using this information to direct beams toward either lone mobiles, or groupings of mobiles, for both transmit and receive modes of operation. The energy associated with each mobile is thus confined within the addressed volume, greatly reducing the amount of cochannel interference experienced from and by neighboring cochannel cells. To ascertain the benefits of such an antenna, the conventional and proposed antenna systems are modeled in a typical mobile radio environment. For a given performance criterion, the theoretical results indicate that a significant increase in the spectral efficiency, or capacity, of the network is obtainable with the proposed antenna.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>