A novel approach to widening the active reflection coefficient(ARC)bandwidth of an antenna array,employing a parasitic coupling network(PCN),is investigated in this article.Different from traditional tightly coupled a...A novel approach to widening the active reflection coefficient(ARC)bandwidth of an antenna array,employing a parasitic coupling network(PCN),is investigated in this article.Different from traditional tightly coupled arrays adopting space structures for enhancing the coupling in balanced-excitation antennas,a PCN derived from rigorous formulas is employed in the feeding lines of unbalanced-excitation ones.Based on network analysis,the mutual coupling utilization condition for an(M×N)-element antenna array is initially deduced,and the PCN is implemented.Then,the PCNs are realized by introducing a parasitic element and a coupling network between the two-element H-plane and E-plane dual-layer coupled microstrip antenna arrays,resulting in 10.9%and 30.8%bandwidth enhancements compared with the original arrays,respectively.Moreover,the PCNs are further expanded to multielement antenna arrays,including three-and five-element one-dimensional and 8×2 twodimensional arrays,exhibiting approximately 40%overlapped ARC bandwidths with normal radiation patterns,steady gains,and applicable scanning characteristics.The results indicate its potential application in large-scale wideband arrays.展开更多
It has been suggested that the importance of network architecture to species diversity and stability should be based on preference networks(comprised of niche differentiations),rather than observational networks,becau...It has been suggested that the importance of network architecture to species diversity and stability should be based on preference networks(comprised of niche differentiations),rather than observational networks,because species abundance may significantly affect interaction frequencies.Considering that resource abundance is usually greater for herbivores than parasites,we hypothesize that the abundance effect is stronger for parasitic than herbivory interactions.To test this hypothesis,we collected 80 quantitative observational networks including 34 herbivorous and 46 parasitic networks from the published literature,and derived preference networks by removing the effects of species abundance.We then determined the network nestedness using both weighted NODF and spectral radius.We also determined species degree distribution,interaction evenness,weighted connectance and robustness for both observational and preference networks.The observational networks(including both herbivory and parasitic networks)were more nested judged by weighted NODF than spectral radius.Preference networks were less nested for parasitic than herbivory networks in terms of both weighted NODF and spectral radius,possibly because removing the abundance effect increased interaction evenness.These trends indicate that the abundance effect on network nestedness is stronger for parasitic than herbivory networks.Weighted connectance and robustness were greater in most preference networks than observational networks,indicating that preference networks may have high network stability and community persistence compared with observational ones.The data indicate that future network analyses should not only address the structural difference between mutualistic and antagonistic interactions,but also between herbivory and parasitic interactions.展开更多
This paper presents a novel de-embedding technique of packaged high-powertransistors. With the proposed technique, the packaged model of the power amplifier (PA)tube can be divided into the frequency independent de-em...This paper presents a novel de-embedding technique of packaged high-powertransistors. With the proposed technique, the packaged model of the power amplifier (PA)tube can be divided into the frequency independent de-embedded intrinsic device (DID)and the frequency dependent internal parasitic network (IPN), which is of great help in reducingthe design complexity of a broadband PA. Different from the conventional techniqueof parasitic extraction, the proposed technique only requires external measurements.The frequency independent characteristic of DID is verified and the IPN is modeledand calibrated for a 50 W gallium-nitride (GaN) transistor. At last, a broadbandDoherty PA is fabricated with the de-embedding technique. According to the measured results,the PA exhibits satisfactory power and efficiency performance.展开更多
基金supported by the National Natural Science Foundation of China(Nos.62201579 and 62201580)the Youth Independent Innovation Science Foundation of National University of Defense Technology(No.ZK24-39)。
文摘A novel approach to widening the active reflection coefficient(ARC)bandwidth of an antenna array,employing a parasitic coupling network(PCN),is investigated in this article.Different from traditional tightly coupled arrays adopting space structures for enhancing the coupling in balanced-excitation antennas,a PCN derived from rigorous formulas is employed in the feeding lines of unbalanced-excitation ones.Based on network analysis,the mutual coupling utilization condition for an(M×N)-element antenna array is initially deduced,and the PCN is implemented.Then,the PCNs are realized by introducing a parasitic element and a coupling network between the two-element H-plane and E-plane dual-layer coupled microstrip antenna arrays,resulting in 10.9%and 30.8%bandwidth enhancements compared with the original arrays,respectively.Moreover,the PCNs are further expanded to multielement antenna arrays,including three-and five-element one-dimensional and 8×2 twodimensional arrays,exhibiting approximately 40%overlapped ARC bandwidths with normal radiation patterns,steady gains,and applicable scanning characteristics.The results indicate its potential application in large-scale wideband arrays.
基金This study was financially supported by National Natural Science Foundation of China(grant nos.32071605,31530007 and 31870417).
文摘It has been suggested that the importance of network architecture to species diversity and stability should be based on preference networks(comprised of niche differentiations),rather than observational networks,because species abundance may significantly affect interaction frequencies.Considering that resource abundance is usually greater for herbivores than parasites,we hypothesize that the abundance effect is stronger for parasitic than herbivory interactions.To test this hypothesis,we collected 80 quantitative observational networks including 34 herbivorous and 46 parasitic networks from the published literature,and derived preference networks by removing the effects of species abundance.We then determined the network nestedness using both weighted NODF and spectral radius.We also determined species degree distribution,interaction evenness,weighted connectance and robustness for both observational and preference networks.The observational networks(including both herbivory and parasitic networks)were more nested judged by weighted NODF than spectral radius.Preference networks were less nested for parasitic than herbivory networks in terms of both weighted NODF and spectral radius,possibly because removing the abundance effect increased interaction evenness.These trends indicate that the abundance effect on network nestedness is stronger for parasitic than herbivory networks.Weighted connectance and robustness were greater in most preference networks than observational networks,indicating that preference networks may have high network stability and community persistence compared with observational ones.The data indicate that future network analyses should not only address the structural difference between mutualistic and antagonistic interactions,but also between herbivory and parasitic interactions.
文摘This paper presents a novel de-embedding technique of packaged high-powertransistors. With the proposed technique, the packaged model of the power amplifier (PA)tube can be divided into the frequency independent de-embedded intrinsic device (DID)and the frequency dependent internal parasitic network (IPN), which is of great help in reducingthe design complexity of a broadband PA. Different from the conventional techniqueof parasitic extraction, the proposed technique only requires external measurements.The frequency independent characteristic of DID is verified and the IPN is modeledand calibrated for a 50 W gallium-nitride (GaN) transistor. At last, a broadbandDoherty PA is fabricated with the de-embedding technique. According to the measured results,the PA exhibits satisfactory power and efficiency performance.
