Jianqiao Wang

Miniaturized Dual-Mode Bandpass Filter with Controllable Harmonic Response for Dual-Band Applications

A miniaturized dual-mode bandpass filter with controllable harmonic response for dual-band applications is presented in this paper. The new bandpass filter is designed with loading distributed capacitors in the inner area of conventional dual-mode loop resonator. This loading can realize both compact size and controllable harmonic response of the filter. A demonstrated filter with the dual-band operating at 1.8 and 2.6 GHz was designed, fabricated and measured. Simulated and measured results indicate that a high selective dual-mode dual-band filter with its size reduced to 34.5% of the conventional case at about 1.8 GHz has been achieved.

An Accurate Imaging Algorithm for Millimeter Wave Synthetic Aperture Imaging Radiometer in Near-Field

Due to the fact that the imaging distance is similar to the dimension of synthetic aperture antenna in near-fleld, the Fourier imaging theory used in the traditional synthetic aperture imaging radiometer (SAIR), which is based on the far-fleld approximation, is invalid for near-fleld synthetic aperture imaging. This paper is devoted to establishing an accurate imaging algorithm for near- fleld millimeter wave SAIR. Firstly, the near-fleld synthetic aperture imaging theory is deduced and its relationship to the far-fleld imaging theory analyzed. Then, an accurate imaging algorithm based on the near-fleld imaging theory is established. In this method, the quadratic phase item and antenna pattern are taken into consideration, and the image reconstruction is performed by minimizing the Total- Variation norm of brightness temperature image, which reduces the in∞uence of the visibility observation error and improves imaging precision. Finally, the efiectiveness of the proposed imaging algorithm has been tested by means of several simulation experiments, and the superiority is also demonstrated by the comparison between it and the existing Fourier transform methods. The results demonstrate that the proposed method is an e-cient, feasible imaging algorithm for near- fleld millimeter wave SAIR.

Compact Microstrip Ring Branch-Line Coupler with Harmonic Suppression

A novel ring branch-line coupler is presented in this paper. To minimize the physical size of the coupler, four high-low impedance resonator cells are loaded within the free area of the conventional coupler. A design methodology calling for united optimization is used to optimize the structure parameters of the main transmission lines and loading high-low impedance resonators. Furthermore, an equivalent circuit of one loaded cell is proposed to model the operation of the coupler. The proposed new coupler not only effectively reduces the occupied size to 22% of the conventional one at the operating frequency of 1.39 GHz, but also has high third harmonic suppression.

Double-folded substrate integrated waveguide band-pass filter with transmission zeros in LTCC

A miniaturized substrate integrated waveguide (SIW) band-pass filter with two transmission zeros is proposed in low-temperature co-fired ceramic (LTCC) technology. The miniaturization of the filter is achieved by vertically stacking three double-folded SIW resonators. To strengthen the coupling between the feeding structure and the resonators, a new meandered microstrip feeding line is introduced. In addition, to realize better out-of-band rejection performance, two short-circuited lines are adopted in the filter design to achieve two transmission zeros outside the passband. To verify the design concept, an X-band LTCC band-pass filter was designed, fabricated, and measured. Both simulation and measurement results indicate that the proposed filter has good frequency response, high selectivity, and a size reduction of about 87% in comparison with conventional planar direct-coupled waveguide filter.

Adaptive CLEAN algorithm for millimetre wave synthetic aperture imaging radiometer in near field

High-resolution millimetre wave images of contiguous targets often suffer from the influence of sidelobe artefacts, partial correlation between targets and so on. Owing to the characteristics of near-field synthetic aperture imaging radiometers [such as the changing point spread function (PSF) and slender sideline], the existing CLEAN algorithms are unsuitable for near-field synthetic aperture imaging. This study is devoted to establishing a novel CLEAN algorithm (named adaptive CLEAN) to clean the reconstructed millimetre wave images accurately. First, the characteristics of near-field synthetic aperture imaging are studied. Then, the adaptive CLEAN algorithm is established based on these characteristics. In this study, the authors amend the amplitude of the targets and select the matching PSF for them according to their azimuths. Unlike other CLEAN algorithms, the parameters of this adaptive CLEAN algorithm are calculated by a formula, which is concluded from a lot of simulation experiments. Finally, the effectiveness of the proposed adaptive CLEAN algorithm is tested by several simulation experiments, and the superiority is also demonstrated by comparing it with the existing CLEAN algorithm. The results demonstrate that the proposed method is an efficient, feasible algorithm for cleaning the reconstructed images, irrespective of the point or contiguous targets.

Label Reconstruction based Laplacian Score for semi-supervised feature selection

In many real world learning tasks, we often face the situation that there is no shortage of unlabeled samples but only a small number of samples are labeled. How to make full use of the limited label information to improve the learning performance is widely studied. In this paper, we consider one of learning methods: semi-supervised feature selection, and we present a novel semi-supervised method, called Label Reconstruction based Laplacian Score (LRLS). The basic assumption of our method is that the labels share the same similarity with the samples. We utilize the geodesic distance to measure the similarity between two samples. Then, we reconstruct the labels of the unlabeled samples by using label reconstruction technique. The weight matrix can be obtained from these labels and the Laplacian score can be calculated. We select the features according to the score. The experimental results have demonstrated the effectiveness of our proposed method.

A Laplacian based semi-supervised learning algorithm for radar target classification

We consider the classification problem of radar high range resolution profile with semi-supervised learning algorithm. Traditional practices are always supervised. They utilize the labeled data but discard the distribution information. In this paper, we take into consideration the unlabeled data and present a novel semi-supervised classification algorithm, called Laplacian Weighted Discriminant (LWD). Inspired by active learning, we first select the most representative points with Laplacian Transductie Optimal Design (LTOD). The sequence of selected points is used as the weight. Then the rate of average weighted distance to different kinds of labeled samples indicates the category of unlabeled samples. The experimental results have demonstrated the effectiveness of our proposed method.

A compressive sensing imaging algorithm for millimeter-wave synthetic aperture imaging radiometer in near-field

In order to overcome the disadvantage of large data amount and receiver number in near-field passive millimeter-wave synthetic aperture imaging radiometer (PMSAIR), an imaging algorithm based on Compressive Sensing (CS) theory is proposed in this paper. Due to the fact that the brightness temperature distributions of the observed target have a sparse representation in some proper transform domain (such as the spatial finite-differences and wavelet coefficients), we use the CS approach to reconstruct the brightness temperature images from very few visibilities. Thus the amount of data and number of receivers can be further reduced than those traditional methods based on the Fourier transform. The reconstruction is performed by minimizing the Total-Variation norm of brightness temperature image. Finally, the numerical simulation of synthetic aperture imaging demonstrates that the proposed algorithm is an efficient, feasible imaging algorithm for near-field PMSAIR.

Imaging simulation modeling for millimeter wave synthetic aperture imaging radiometer in near-field

Due to the fact that theoretical analysis and instrument construction for antenna array of synthetic aperture imaging radiometer (SAIR) are both complicated, and designers usually hope to predict the imaging effect and analysis the influence of the parameters of SAIR before the system design. The simulation is a very useful method in the system design of SAIR. This paper is devoted to establishing an accurate imaging model of near-field millimeter wave SAIR for simulating the imaging process that include target radiating electromagnetic wave, antenna collecting target radiation and transforming them into RF signal, and antenna array collecting the visibility function. By using the equivalent complex baseband signals to represent the practical target radiation and RF signals in time domain, the efficiency of this simulation model is improved significantly. Some characteristics of near-filed millimeter wave SAIR are verified by a series of simulation experiments, and the effectiveness of this imaging model is tested by these simulation experiments. Results of the imaging simulation experiment show that this model is an efficient, feasible imaging model for near-field millimeter wave SAIR.

A low insertion loss 60 GHz band pass filter using wafer transfer

In this paper, a low insertion loss band pass filter using WTT for 60 GHz band applications is presented. The filter geometry was pre-fabricated on a Si wafer with 3-um-thick Cu and 1KA SiN dielectric layer. Then this filter pattern was transferred onto the substrate Rogers RT/Duroid 5880. In this design, by replacing the silicon substrate with the Rogers RT/Duroid 5880 base, a low insertion loss 60 GHz band pass filter has been achieved. The measurement results show this filter has a 3dB band width of 7.5 GHz and insertion loss is 1.8 dB. Measured results are consistency with the HFSS simulation results.