Multi‐narrowband‐reconfigurable slot dipole antenna

Abstract

network in which two low-frequency (LF) signals are subtracted allows to minimize losses, as LF signal is virtually not subject to dielectric absorption and parasitic radiation. Furthermore, the presented solution does not use any LF fixed phase shifters which cause significant difficulties in wideband systems. As a result, 15% shortening of the microwave signal path has been achieved in the presented receiver. Figure 8 presents the measured radiation pattern of the developed radar receiver. As it is seen, the obtained beams measured at intermediate frequency f 5 10 MHz are in close agreement with the ones presented in Figures 2 and 4, although minor asymmetry between L and R beams can be seen, which is caused by imbalance of mixers' characteristics, mainly the input impedance. The gain and the losses of the receiver's antenna array could not be precisely measured due to uncertainty of the mixers' conversion gain. However, the receiver's antenna gain and the losses can be estimated from the fact that the receiver's feeding network is 15% shorter than feeding network of the antenna from Figure 1. Hence the gain equal 7.4 dBi and the insertion losses equal 1.8 dB have been estimated. The manufactured receiver is shown in Figure 9. CONCLUSIONA novel concept of the switched-beam antenna array with broadside beam has been presented. The proposed antenna array utilizes a modified Butler matrix as a feeding network and allows for achieving two symmetrically placed beams and a broadside beam. Moreover, the proposed network rearrangement allows for fully planar realization without the need of transmission line crossovers. The developed concept has been applied in a Doppler radar receiver, in which a low frequency differential amplifier has substituted the RF power divider and a constant 180 phase shifter, minimizing the dissipation losses and parasitic radiation of the feeding network. The proposed concept of a switched-beam antenna has been verified experimentally. The obtained measurement results fully confirm the theoretical predictions. ACKNOWLEDGMENT

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