GSM900 Base Station Research Articles

Design of broadband dual‐polarized planar antenna with triple radiators

A wideband dual-polarized planar antenna with triple radiators is proposed for the LTE600/LTE700/GSM850/GSM900 base station in this paper. A novel concept of multi-radiator for multi-resonance by close coupling feed is presented and analysed . The proposed antenna is mainly composed of two pairs of loop dipole, L-shaped radiator, step dipole, two L-shaped feed lines, balun and reflector. The reflector is designed with a centrosymmetric partible baffle for directional radiations, which contribute to stable radiations as well. Owing to the novel closely coupling scheme for multi-radiators, three resonances are simultaneously excited within the desired band, producing a wide bandwidth of 47.7% (from 0.59 to 0.96 GHz) for |S11| < −15 dB with high isolation more than 30 dB. Moreover, an average gain of 8.8 dBi as well as stable radiation patterns are achieved simultaneously.

Sensitivity measurements of a passive intermodulation near-field scanner

A passive intermodulation (PIM) near-field XY scanner for the GSM900 frequency band has been constructed to localize distortion sources in antennas and in other open structures. The equipment should be able to measure distortion levels down to -115 dBm with an input power of 2/spl times/20 W, since the noise floor of a GSM900 base station is typically around -110 dBm. The sensitivity is limited either by thermal noise or by residual intermodulation distortion, depending on the probe coupling. Various causes of residual intermodulation distortion in the passive intermodulation near-field measurement are considered and evaluated. Sensitivity measurements of the scanner have been carried out on two test devices. Sensitivities of -112 dBm and -110 dBm have been achieved with an electric and a magnetic field probe, respectively.

A wide-band dual-polarization patch antenna with directional coupler

A broad-band dual-polarization patch antenna fed by L-shaped probes at the patch corners is presented. A coupled line directional coupler mounted at the back of the ground plane is used to enhance the isolation between the L-probes to a large extent. Through using the coupler to feed the L-probes, the isolation between the input ports is 34 dB over the GSM900 operating bandwidth, which has enhanced by 14 dB. By using two plastic spacers of 0.1/spl lambda//sub o/ in height to support the patch in the air, an impedance bandwidth of 18% (for S/sub 11//spl les/-14 dB), and an average gain of 7 dBi can be obtained for both ports. The far field patterns are stable across the passband. This antenna can potentially be used as a GSM900 base station antenna.