Jianyi Zhou

Planar Ultrawideband Antennas With Multiple Notched Bands Based on Etched Slots on the Patch and/or Split Ring Resonators on the Feed Line

Three types of ultrawideband (UWB) antennas with triple notched bands are proposed and investigated for UWB communication applications. The proposed antennas consist of a planar circular patch monopole UWB antenna and multiple etched slots on the patch and/or split ring resonators (SRRs) coupled to the feed line. Good agreement is achieved between the simulated and measured results. These techniques are significant for designing UWB antennas with multiple narrow frequency notched bands or for designing multiband antennas.

A Multibeam Antenna Based on Substrate Integrated Waveguide Technology for MIMO Wireless Communications

A 24-beams slot array antenna, which achieves 360-degrees coverage over azimuth direction, based on substrate integrated waveguide (SIW) technology is designed, fabricated and measured for supporting the concept of triangle cell, beam diversity and multiple input multiple output (MIMO) wireless communications. Constructed by six 4-beams single layer SIW antennas which integrate the 4times8 modified Butler matrix with a low side lobe level (SLL) amplitude distribution, measured SLLs are reduced as low as -14.5 dB for all beams in E-plane. The size of the SIW single layer multibeam antenna is 385 mm times 110 mm including feeding network. The usable bandwidth of the proposed antenna is 3.75% at 16 GHz.

Design of High-Q Tunable SIW Resonator and Its Application to Low Phase Noise VCO

In this letter, a low-cost continuously tunable substrate integrated waveguide (SIW) resonator and a low phase noise SIW voltage-controlled oscillator (VCO) are presented. A simple new structure for coupling varactor to the SIW cavity is proposed, which realizes a simple circuit layout for the tuning resonator. Equivalent circuit model is given for the varactor coupled resonator. Relation between the coupling coefficient and the relative tuning bandwidth is analyzed. Prototypes of tunable SIW resonator and a low phase noise SIW VCO have been designed and fabricated. Measured results show that the proposed resonator possesses unloaded Q factor of 286-299 for a tuning range of 492 MHz, and the phase noise of the SIW VCO is -93 --95.6 dBc/Hz at 100 kHz offset for the whole oscillating frequency range of 455 MHz at X-Band.

Behavioral Modeling of Power Amplifiers With Dynamic Fuzzy Neural Networks

In this letter, dynamic fuzzy neural networks (D-FNN) are applied to model power amplifiers (PAs) with memory effects. The D-FNN model implements Takagi-Sugeno-Kang (TSK) fuzzy systems based on extended radial bias function (RBF) neural networks. The parameters of the model are trained by the online self-organized learning algorithm, in which the neurons can be recruited or deleted dynamically according to their significance to system performance, and the over fitting or over training problems can be avoided. The D-FNN model is validated in our test bench in which a Doherty PA is excited with 10 MHz and 20 MHz worldwide interoperability for microwave access (WiMAX) signals. Experimental results show that the D-FNN model can give an accurate approximation to characterize the wideband PAs with memory effects.

The Dynamic Behavioral Model of RF Power Amplifiers With the Modified ANFIS

The adaptive neuro-fuzzy inference system (ANFIS) has been widely used for modeling different kinds of nonlinear systems including RF power amplifiers (PAs). The modified ANFIS (MANFIS) architecture is simpler than that of ANFIS, but with nearly the same performance for modeling nonlinear systems. In this paper, the MANFIS is applied to model RF PAs with memory effects. The simulation and experimental results both in the time and frequency domains show that this model has good modeling accuracy and the characteristics of faster convergence and lower computational complexity compared with the ANFIS model. The normalized mean squared errors of the MANFIS model are slightly lower than those of some other neural network models such as the real-valued time delay neural network, radial basis-function neural network, etc. Finally, the MANFIS model is successfully used in a digital predistortion system, which can provide over 10- dB adjacent channel leakage ratio improvement for three-carrier wideband code division multiple access signals.

Single-Fed Low Profile Broadband Circularly Polarized Stacked Patch Antenna

A simple technique is developed in this communication to increase the axial ratio (AR) bandwidth and achieve good impedance matching of a single-fed low profile circularly polarized (CP) stacked patch antenna. The proposed antenna is composed of a driven patch layer and a parasitic patch layer. The driven patch layer consists of a truncated main patch, a parasitic patch and a probe feeding structure while the stacked patch layer is comprised of five patches. The proposed antenna combines the attractive features such as low profile, wide impedance and AR bandwidths, high gain as well as easiness of design, manufacture and integration. The antenna operating at 6 GHz band is designed and fabricated on an FR4 substrate and the overall volume is 0.8 λ0 ×0.8 λ0 ×0.09 λ0. Measured results show that the antenna achieves an impedance bandwidth of more than 30% for dB, a 3-dB AR bandwidth of about 20.7%, and a gain level of over 7.9 dBi within the 3-dB AR bandwidth.

A compact multiple bands notched UWB antenna by loading SIR and SRR on the feed line

In this paper, a new compact circular monopole ultrawide band (UWB) antenna with multiple narrow bands notched is proposed, designed and fabricated with a standard printed circuit board (PCB) process, which is implemented by loading a stepped impedance resonator (SIR) and a split ring resonator (SRR) on the feed line. Good agreement between simulations and measurements is achieved, which shows the antenna is a promising candidate for UWB applications.

An X-Band Low Phase Noise Free-Running Oscillator Using Substrate Integrated Waveguide Dual-Mode Bandpass Filter With Circular Cavity

In this letter, a low phase noise free-running oscillator employing a substrate integrated waveguide (SIW) dual-mode bandpass filter (BPF) is presented. As a frequency stabilization element in the feedback loop, the dual-mode SIW BPF is designed at the oscillation frequency. Due to the transmission zero near the upper passband of the filter, a large group delay peak at the upper passband edge can be achieved to improve the phase noise performance significantly. An X-band oscillator using a SiGe HBT has been designed and experimentally demonstrated at 11.571 GHz. Measured results show that, the phase noise of this proposed oscillator is -135.5 dBc/Hz at 1 MHz offset frequency with a figure of merit (FOM) of -206.2 dBc/Hz.

Bandwidth- and Gain-Enhanced Circularly Polarized Antenna Array Using Sequential Phase Feed

A technique is developed in this letter to enhance the impedance and axial-ratio (AR) bandwidths as well as broadside gain of a sequential phase (SP) feed 2 × 2 patch array. The proposed antenna is composed of a probe-fed patch, a 2 × 2 corner truncated patch array with a loop, and a slotted metal wall surrounding the feeding structure. The proposed antenna combines the attractive features such as wide impedance and AR bandwidths, low profile, and easiness of design and manufacture. The antenna operating at 5-GHz band is designed and fabricated with overall volume of 1.5 λ0×1.5 λ0 ×0.06 λ0. Measured results show that the antenna array achieves an impedance bandwidth of about 20.8% for |S11|<;-10 dB, a 3-dB AR bandwidth of about 17.6%, a peak gain of 11.5 dBi, and a 3-dB gain bandwidth of 13%, which is completely within the impedance and AR bandwidths.

Dynamic Behavioral Modeling of Power Amplifiers Using ANFIS-Based Hammerstein

This letter presents a novel structure for the dynamic behavioral modeling of radio frequency power amplifiers (RF PAs) with ANFIS-based Hammerstein model for memory effects. The model is an adaptive neuro-fuzzy inference system (ANFIS) followed by a finite impulse response (FIR) filter. A hybrid learning algorithm is adopted to identify the parameters of the ANFIS. The parameters of the FIR filter are estimated by a straightforward least-squares method. The input and output signals of the PA excited with a three-carrier WCDMA signal were sampled for the model identification and validation in a test bench. Experimental results in the frequency and the time domains show that the proposed model was able to give an accurate approximation to characterize the wideband RF PAs.