Since adaptive beamformer suffers from output performance degradation in the presence of interference nonstationarity and signal steering vector mismatch, a novel robust null broadening adaptive beamforming is proposed. The proposed method is realized by the combination of projection transform and diagonal loading techniques. First, a new projection matrix with null broadening ability is constructed and then projects the array received data onto the projection matrix. With the diagonal loading technique, a new sample covariance matrix is obtained. The theoretical analysis shows that the projection transform operation can expand the incident direction of the interference and improve orthogonality between the signal-plus-interference and the noise subspaces; thus the proposed beamformer can effectively broaden the jammer null and enhance the null depth. The analytical expressions of the proposed algorithm are also provided, which are efficient and easily solved. Simulation results are presented and demonstrated that the proposed beamformer can provide strong robustness against signal steering vector mismatch and jammer motion.
This Letter proposes an approach to develop a spoof surface plasmon polariton (SSPP) transmission line (TL) by loading short-circuited (SC) shunt stubs. Lower out-of-band rejections can be flexibly controlled without affecting the upper cutoff frequency by independently modifying the stubs. Dispersion analysis of the SSPP unit is realized by theoretical calculation and circuit simulation to predict the upper cutoff frequency of the proposed SSPP TL simultaneously. Also, parametric sweeping of the SC shunt stubs is performed based on circuit simulation to investigate their impacts on the lower and upper out-of-band rejections of the proposed SSPP TL. In addition, electric field distributions of different types of TLs are simulated and compared to study the transmission characteristics of the proposed SSPP TL. The lower cutoff frequency can be flexibly tuned in a wide range, from 1.2 to 2.1 GHz, in the simulations. The measured 3-dB fractional bandwidth is about 128.1%, covering a range from 1.19 to 5.43 GHz. The numerical and experimental results are compatible, which verifies the feasibility of the proposed approach. This approach can offer more convenience and flexibility for controlling the rejections of the SSPP by introducing up to four tuning parameters. More importantly, the proposed SSPP TL avoids using the substrate integrated waveguide (SIW) technique, which shows the potential to decrease the transverse width ( 0.44 λ g ), especially at lower frequencies (e.g., 1.2 GHz), and to reduce the complexity in designing the high-efficiency transition. This work paves the way for the development of novel SSPP-based microwave devices.
In this paper, a strategy to develop a compact transition of the spoof surface plasmon polariton (SSPP) transmission line (TL) is proposed. First, an equivalent distributed circuit model is employed for the theoretical analysis and optimization design of the SSPP unit. The mapping relation between the unit performance and the geometric parameters is deduced from the transmission matrix. The calculated results are compared with the numerical ones from the three-dimensional (3D) simulations for validation. Then, a compact transition (only 0.26λg) is built with only two matching units and a tapered strip through optimizations. The optimizations are implemented with the circuit simulations based on the equivalent model, which can remarkably save time in comparison with the 3D simulations. The transition principle is also explained by quantitatively extracting the dispersion properties and impedance characteristics. Finally, a prototype of the proposed SSPP TL is fabricated and measured for demonstration. The measured operating band (0-7.7 GHz) is almost up to the cut-off frequency (about 8 GHz), which remains the inherent broadband low-pass transmission characteristics. Meanwhile, the measured in-band return loss is almost higher than 10dB, which verifies the high-efficiency propagation. This work can pave the way for building up a new SSPP-based framework of microwave circuits.
In the study of the frequency domain crosstalk for twisted pair, the traditional alternating inversion model is often built under the ideal condition of lossless and uniform media, ignoring the length of the twisted section. This paper focuses on the impact of these non-ideal conditions on crosstalk, applying the cascaded transmission line theory of Paul and McKnight to predict near-end crosstalk (NEXT) of two pairs of twisted wire pair (TWP) which are placed above a perfectly conducting ground or in a cylindrical ideal conductive shell. This paper put forward the non-uniform-media layered connection method (NLCM) to solve the parasitic parameter matrix, taking two layers as an example. Based on the deduced chain parameter matrix and boundary conditions, the exact crosstalk solution is obtained. All theories in this paper are of great significance to the EMC design of high-speed data transmission systems, providing the theoretical support for predicting NEXT within each device or system.INDEX TERMS Crosstalk, frequency domain analysis, non-uniform-media layered connection method (NLCM), transmission lines, twisted wire pair (TWP).
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