Xiang-Quan Shi

Wideband Circularly-Polarized Patch Antenna

A novel wideband circularly-polarized patch antenna is presented. First, a new broadband 90deg hybrid feed network is proposed to have a bandwidth of 75% for the 10-dB return loss, good two output ports amplitude balance and a consistent 90deg (plusmn3deg) phase difference between two output ports. Then, a circular patch antenna fed by four sequential-rotation proximity-coupled L-probes orientated to have phase of 0deg, 90deg, 180deg and 270deg is presented. The four L-probes are connected to the respective ports of a feed network comprising a pair of the proposed broadband 90deg hybrid. It is found that the antenna can deliver a measured impedance bandwidth of 79.4% from 1.04 to 2.41 GHz for SWR 3 dBi. The simulated impedance bandwidth is 94% from 0.9 to 2.5 GHz for SWR 3 dBi. Good agreement is observed between simulation and measurement

Wide-band stacked double annular-ring dielectric resonator antenna at the end-fire mode operation

A novel wide-band stacked double annular-ring dielectric resonator antenna (DRA) is numerically investigated in this paper. At either layer, a larger annular-ring dielectric resonator is placed concentrically outside a smaller annular-ring one to form a stacked double annular-ring DRA. The antenna is operating at the end-fire mode. The effects of antenna parameters such as dielectric constant, probe length and air-gaps thickness are investigated. Compared to the obtained 18% bandwidth of the stacked annular-ring DRA, the proposed stacked double annular-ring DRA can offer an impedance bandwidth of /spl sim/42% for the return loss below -10 dB. The radiation patterns are stable in the passband.

135-GHz Micromachined On-Chip Antenna and Antenna Array

This paper presents the design, fabrication and “on-wafer” characterization of multi-membrane-supported and polymer-cavity-backed monopole antenna and 2× 1 patch antenna array operating in the 135-GHz frequency range. The designs were fabricated on two-layer benzocyclobutene (BCB) material membrane obtained by micromachining of the low resistivity silicon. The silicon material is removed underneath the monopole antenna to produce a cavity surrounded by metal and filled with polymer. This polymer filled cavity provides a better support to the membrane than conventional air cavity which is extremely important for practical applications. In the meantime, the higher synthesized effective dielectric permittivity of the BCB-polymer mixed region than BCB-air mixed one provides the possibility for compact antenna array designs. The proposed monopole antenna shows a measured impedance bandwidth from 124 to 136 GHz for |S11| less than -10 dB and maximum measured gain of 6.74 dBi at 131 GHz; while the 2×1 patch antenna array achieved a measured impedance bandwidth from 126.5 to 138 GHz for |S11| less than -10 dB and maximum measured gain of 8.66 dBi at 130 GHz.

Wideband circularly-polarized patch antenna

A novel wideband circularly-polarized patch antenna is presented. First, a new broadband 90deg hybrid feed network is proposed to have a bandwidth of 75% for the 10-dB return loss, good two output ports amplitude balance and a consistent 90deg (plusmn3deg) phase difference between two output ports. Then, a circular patch antenna fed by four sequential-rotation proximity-coupled L-probes orientated to have phase of 0deg, 90deg, 180deg and 270deg is presented. The four L-probes are connected to the respective ports of a feed network comprising a pair of the proposed broadband 90deg hybrid. It is found that the antenna can deliver a measured impedance bandwidth of 79.4% from 1.04 to 2.41 GHz for SWR<2, measured 2-dB and 3-dB axial-ratio bandwidths of 57% from 1.3 to 2.35 GHz and 82% from 1 to 2.4 GHz, respectively, and a measured gain bandwidth of 56.1% from 1.26 to 2.32 GHz for gain>3 dBi. The simulated impedance bandwidth is 94% from 0.9 to 2.5 GHz for SWR<2. The simulated 3-dB axial-ratio bandwidth is 63.8% from 1.25 to 2.42 GHz. The simulated gain bandwidth is 59.3% from 1.33 to 2.45 GHz for the gain>3 dBi. Good agreement is observed between simulation and measurement

Wideband Self-Complementary Quasi-Yagi Antenna for Millimeter-Wave Systems

Novel wideband quasi-Yagi antennas, each featuring a self-complementary structure together with a triangular notch on the ground plane, are proposed. The optimized proposed antenna offers an improved relative bandwidth of 74%, gain of 4-8 dBi, and stable endfire radiation patterns within the passband. Good agreement between simulation and measurement is shown.

Broadband Slot Antenna with Circular-Polarization Operation

In this paper, a novel wideband circularly polarized slot antenna is presented. The slot antenna with four microstrip line feeds orientated to have phases of 0deg, 90deg, 180deg and 270deg, using a feed network comprising a pair of broadband 900 hybrid was found to deliver a measured impedance bandwidth of 77.8% from 1.02 to 2.32 GHz for SWR<2, measured 2-dB and 3-dB axial-ratio bandwidths of 51.4% from 1.3 to 2.2 GHz and 88.9% from 1 to 2.6 GHz, respectively, and a measured gain bandwidth of 33% from 1.5 to 2.1 GHz for gain>3dBi. The simulated impedance bandwidth is 89.1% from 1.02 to 2.66 GHz for SWR < 2. The simulated 3-dB axial-ratio bandwidth is 81% from 1.1 to 2.6GHz. The simulated gain bandwidth is 27% from 1.6 to 2.1 GHz for the gain > 3dBi. Good agreement is observed between simulation and measurement.

A study on the performance of space-time coding UWB-impulse radio system in IEEE 802.15 multipath channels

In this paper, the performance of the space-time coding ultra wideband impulse radio system in a typical IEEE 802.15 multipath channel is studied. In the proposed scheme, only two transmit antennas and one receiver antenna are employed and no channel information feedback is needed. We investigate how the temporal and spatial diversity influence the multiple access performance and how the space-time coding technique is used to mitigate the multiple access interference (MAI) and the inter-symbol interference (ISI) thereby improves the bit error rate performance of the ultra wideband impulse radio system. Numerical results show that the space-time coding technique is an efficient means to improve the performance of ultra wideband impulse radio system under IEEE 802.15 multipath environment in both one single user and multi users environment.

A local stabilizing method for chaotic synchronization

In this paper, a new method for chaotic synchronization using scalar transmitted signal is proposed based on the local stabilization of the coupled systems in the synchronization manifold. The method, using conditioned coupling strength, can be considered as a general method to synchronize chaotic systems in a drive-response scenario. The validity and feasibility of the method is tested by numerical experiments performed on Rossler oscillators.

Optimal UWB Waveform Design for Antenna Dispersion Compensation

A new pulse design method for Ultra-wideband (UWB) radios is proposed. By precisely formulating the effective isotropic radiated power, the proposed method can properly pre-compensate the antenna dispersion effects. Compared to the existing waveform design methods, the proposed method can provide much more efficient utilization of the FCC assigned spectrum.

A Compact Wideband Printed Wire Antenna for Wireless Communications

This paper presents a compact dual-band printed-circuit-board wire antenna for wireless communications applications. The proposed wire antenna in F-shape with a shorted parasitic element can offer two separate impedance bandwidth of about 0.8 GHz (2.3 GHz~3.1 GHz) and 2 GHz (4.1 GHz~6.1 GHz) for a return loss less than -10 dB. Moreover, the antenna remains compact in size, making it a good candidate for Bluetooth and wireless local area network (WLAN) operation in the 2.4 GHz band and 5.2/5.8 GHz band. Measured results, including return loss and Smith chart, are presented