Wen-Jun Lu

Wideband Stub-Loaded Slotline Antennas Under Multi-Mode Resonance Operation

A novel center-fed wideband slotline antenna is proposed using the multi-mode resonance concept. By symmetrically introducing one or two pairs of slot stubs along the slotline resonator near the nulls of electric field distribution of the second odd-order mode, two modes are excited in a single slotline radiator. With the help of these stubs, the second odd-order mode can be gradually merged with its first counterpart, resulting in a wideband radiation characteristic with two resonances. Prototype antennas are then designed and fabricated to experimentally validate the principle and design approach. It is shown that the operation fractional bandwidth of the proposed slotline antenna could be effectively increased to 31.5% while keeping an inherent narrow slot structure.

Planar Endfire Circularly Polarized Antenna Using Combined Magnetic Dipoles

A novel planar circularly polarized antenna with endfire radiation beam in parallel with the antenna substrates plane is proposed. The operation principle of the antenna is analyzed and design guidelines are laid down. Then, an optimized loop-aperture combined antenna is designed and demonstrated to exhibit an endfire beam in parallel with its plane within 5.74-5.88 GHz for |S11| lower than -10 dB and axial ratio smaller than 3 dB. The proposed antenna can be used as a low-profile, cost-effective, hand-held reader antenna for radio frequency identification systems .

A Planar End-Fire Circularly Polarized Complementary Antenna With Beam in Parallel With Its Plane

Operation principle and design approach of a novel planar end-lire circularly polarized (CP) complementary antenna is proposed. A vertically polarized printed magnetic dipole and a horizontally polarized printed dipole are combined on the same substrate, and a planar CP antenna with end-lire beam in parallel with its plane is thus designed. Prototype antennas centered at 5.80 GHz are then fabricated and measured to validate the operation principle and the design approach. The experimental prototype reported that the impedance bandwidth (20 log |S11| ( <; -10 dB) is about 1.90%, from 5.75 to 5.86 GHz and the 3-dB axial ratio (AR) bandwidth is about 14.48%, from 5.19 to 6.00 GHz. Therefore, the proposed design is applicable as a low-prolile handheld reader antenna in radio-frequency identilication (RFID) systems.

Dual-Band Loop-Dipole Composite Unidirectional Antenna for Broadband Wireless Communications

The design of a novel dual-band loop-dipole composite unidirectional antenna for broadband wireless applications is proposed. First, design guidelines of the antenna are presented, and then, a step-by-step derivation of the antenna geometry is drawn. The antennas operation principle is analyzed by carrying out parametric studies of surface current distribution, impedance and radiation patterns. The reflection coefficient, radiation patterns and gain of the antenna are numerically and experimentally studied to verify the operation principle and the design approach. It is demonstrated that two pass-bands, from 1.54 to 3.24 and from 4.88 to 6.80 GHz, of reflection coefficient smaller than -10 dB are obtained. The antenna has stable and unidirectional radiation pattern with low cross polarization within its pass-bands. The average gain of the antenna is 6.7 dBi at low frequency band and 6.5 dBi at high frequency band.

Planar Wideband Loop-Dipole Composite Antenna

A novel planar wideband balanced composite antenna is presented. The proposed antenna consists of a symmetrical dipole and an antipodal loop radiator. The return loss, radiation pattern, and gain of the antenna are numerically and experimentally studied. An impedance bandwidth of 129% (20 log |S11| <; -10dB) from 3.26 to 15 GHz has been obtained. Stable end-fire radiation patterns with good polarization purity and flat gain performances are obtained across the operating frequency range. In addition, the time domain responses of the proposed antenna are investigated. The proposed antenna can be used in compact wireless devices for point-to-point applications.

A Novel Planar Endfire Circularly Polarized Antenna With Wide Axial-Ratio Beamwidth and Wide Impedance Bandwidth

A novel wideband planar endfire circularly polarized (CP) antenna with wide 3 dB axial ratio (AR) beamwidth is presented. The operation principle of the proposed CP antenna is described at first through the combination of a planar magnetic dipole and a V-shape open loop. Then, it is demonstrated how its AR beamwidth can be precisely controlled with resorting to the shape and thickness of the open loop element. Finally, the theoretical design approach is numerically verified, and the results are then experimentally validated. It is observed that a 3 dB AR beamwidth is achieved in an extremely wide angular region up to 250° within the principal elevation plane over a frequency range of 2.41-2.51 GHz. The proposed antenna has exhibited a wide impedance bandwidth of 22.23% in fraction, a 3 dB AR bandwidth of no less than 8.00% in fraction, and a simple planar profile in geometry. In addition, its endfire beam is in parallel with its plane.

Loop-Monopole Composite Antenna for Dual-Band Wireless Communications

A novel loop-monopole composite antenna for wireless communications is presented. The proposed antenna is composed of a loop, a monopole, a horizontal ground plane and a vertical reflector. The antennas operation principle is investigated and some design guidelines are laid down in the beginning. Then, an optimized loop-monopole composite antenna is designed. It is demonstrated that the antenna covers two bands from 2.16 to 3.21 GHz and from 4.24 to 7 GHz for |S11| smaller than -10 dB. The antenna has stable, unidirectional radiation pattern within its pass-bands. The average gain of the antenna is 4.5dBi (lower band) and 7.7dBi (higher band). The proposed antenna can be used as an indoor base station antenna for multiband wireless communications.

Measurement and empirical modeling of massive MIMO channel matrix in real indoor environment

A novel empirical, measurement-based massive MIMO channel matrix model under real indoor environment at 4.1 GHz is proposed. In this model, the channel matrix can be described as the sum of a fixed and a random matrices, furthermore, the random matrix can be decomposed into the product of four parts: the eigenvectors of the transmitting and receiving side correlation matrices, a coupling matrix, whose amplitude and phase are lognormal and uniform distributions, and a complex Gaussian random matrix. By comparing the capacity and singular value spread, the proposed model is validated to be more accurate than the conventional Kronecker and Weichselberger models. The proposed model is promising for the system design and implementation in future 5G systems.

A Novel Compact Dual-Polarized Antenna

A novel compact dual-polarized antenna is proposed. The antenna has a 1.43% impedance bandwidth which is from 1801 MHz to 1827 MHz for return loss larger than 10 dB. The isolation between the two ports is above 28 dB in the bandwidth, and the gain is 6.6 dBi. The proposed antenna not only consists of a full-planar structure, but also is easy to be fabricated for its simple structure. Additionally, a section of slots and slits is cut on the radiation patch to reduce the area of it to 54% compared with the conventional square patch.

Ultra-wideband antipodal slot antenna with improved radiation performance

A novel antipodal wide-slot antenna for ultra-wideband (UWB) applications is proposed and studied in detail. The antenna is fed by a microstrip line terminated with a rectangular tuning patch. An antipodal structure is employed to improve the radiation performances. The return losses, surface E-field, current distribution, radiation patterns and gains of the antenna are numerically and experimentally investigated. Results show that the proposed antipodal antenna has an impedance bandwidth from 0.79 to 4.0 GHz, which is about 5:1. Compared with conventional rectangular wide-slot antenna, more stable radiation pattern with lower cross-polarisation level and flatter gain variation over a 3:1 bandwidth can be obtained. Thus, the proposed antenna should be more suitable for future UWB-multiple-input multiple-output applications using polarisation diversity than conventional UWB rectangular slot antennas.