Effects of finite weight resolution and calibration errors
on the performance of adaptive array antennas
IEEE Transactions on Aerospace and Electronic Systems.
Vol.37, No.2, April 2001, pp.549-562
Adaptive antennas are now used to increase the spectral efficiency in
mobile telecommunication systems. In this paper, a model of the
received carrier to interference plus noise ratio (CINR) in the
adaptive antenna beamformer output is derived, assuming
that the weighting units are implemented in hardware. The finite
resolution of weights and calibration is shown to reduce
the CINR. When hardware weights are used, the phase or amplitude step size in the
weights can be so large that it affects the maximum achievable CINR. It is shown how these errors makes the interfering
signals ``leak'' through the beamformer and we show how the output CINR
is dependent on power of the input signals. The derived model is
extended to include the limited dynamic range
of the receivers, by using a simulation model. The theoretical
and simulated results are
compared to measurements on an adaptive array antenna testbed receiver,
designed for the GSM-1800 system. The theoretical model was used to
find the performance limiting part in the testbed as the 1 dB
resolution in the weight magnitude. Furthermore, the derived models are used in
illustrative examples and can be
used for system designers to balance the phase and magnitude resolution
and the calibration requirements of future adaptive array antennas.
Auto-Calibrating Adaptive Array for Mobile Communications
IEEE Transactions on Aerospace and Electronic Systems publication, April 2000
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