Search

In this letter, a general approach to synthesize arbitrary order dual-band narrow-band bandstop filter (BSF) is proposed. Simple formulas are derived to calculate the design parameters for the filter. To validate the method, a third-order dual-band BSF using substrate integrated waveguide (SIW) technology is fabricated. Taking the advantage of the high Q SIW resonators, the fabricated filter shows good stopband suppression. The measured center frequencies of the filter are 6.81 and 7.213 GHz, and the corresponding relative 3-dB bandwidths are 4.6% and 4.1%. [ABSTRACT FROM AUTHOR]

A novel 2×2 broadband circularly polarized low-profile monopole array antenna adopting the sequential rotation technique is presented and experimentally studied in this article. The array is very lightweight and is printed on the 0.2 mm flexible substrate. The basal antenna element of the 2×2 arrays is a printed curve-shaped monopole with good bandwidth and circular polarization property. The simulated and measured impedance bandwidth and axial ratio bandwidth are presented. Moreover, radiation patterns are also presented. The advantages of the proposed antenna include low-profile, light-weight, simple structure, and broad working bandwidth. [ABSTRACT FROM AUTHOR]

A high power gain magnetron amplifier with output phase control based on load–pull characterization has been developed. The equivalent resonant cavity method was first introduced to facilitate the proposed magnetron amplifier system as a basic injection model, and the system behavior was qualitatively evaluated based on Alder’s equation. It is the first time that a magnetron has been locked at a 58-dB gain. The magnetron amplifier shows an enhanced power-added efficiency of 72.0%, wide output phase control range, and 18.5-MHz bandwidth at a ratio of the output to the input power of 45 dB. This is the first time a successful magnetron output phase control based on load–pull at a power gain of 45 dB has been demonstrated. The magnetron output spectra were fully synchronized with a reference signal and the phase noise of the magnetron amplifier reached −106.3 dBc/Hz at an offset of 1 kHz. An output amplitude stability of 0.01 dB (peak to peak), a phase stability of 0.5° (peak to peak), and a high-efficiency dual 1-kW magnetron amplifier coherent-power combination based on the load–pull characterization was achieved. To the best of the authors’ knowledge, this is one of the highest power gains and phase noise performances ever reported for an S-band injection-locked magnetron with a power output of over 1 kW. [ABSTRACT FROM AUTHOR]

The resonant cavity antenna (RCA) is a class of widely used high gain antennas, but usually suffers from narrow impedance bandwidth owing to its strong resonant property, as well as relatively low aperture efficiency because of its non-uniform electromagnetic (EM) field distribution on the aperture. This article explores enhancing the RCA's impedance bandwidth and aperture efficiency by designing a non-uniform metamaterial inspired superstrate, on which the metal patches vary their sizes with respect to their distances to the superstrate's center. After optimized by the Genetic Algorithm, the proposed RCA is designed, fabricated and tested. Measured results agree well with simulated ones and show that in comparison with a RCA with a uniform metamaterial inspired superstrate, this work significantly improves the | S11| < −10 dB impedance bandwidth from 2.1% to 6.1%, the gain at the working frequency 10 GHz from 19.07 dBi to 20.55 dBi, and correspondingly the aperture efficiency from 50.5% to 71%. A further analysis estimates that due to the non-uniform metamaterial inspired superstrate, a more homogeneous distribution for both the amplitude and phase of the EM field is observed on the superstrate's aperture. [ABSTRACT FROM AUTHOR]

A novel design of 1×2 and 2×2 circularly polarized (CP) microstrip patch antenna arrays is presented in this paper. The two CP antenna arrays are fed by sequentially rotated coplanar waveguide (CPW) to slotline networks and are processed on 1 mm thick single-layer FR4 substrates. Both of the two arrays are low-profile and lightweight. An air-bridge free CPW-slotline power splitter is appropriately designed to form the feeding networks and realize the two CP antenna arrays. The mechanism of circular polarization in this design is explained. The simulated and measured impedance bandwidths as well as the 3 dB axial ratio bandwidths and the radiation patterns of the two proposed antenna arrays are presented. This proposed design can be easily extended to form a larger plane array with good performance owing to its simple structure. [ABSTRACT FROM AUTHOR]

A 3-D particle-in-cell simulation model of a commercial industrial heating magnetron is developed as a guide for improving a fixed-output-power magnetron. After this improvement, the magnetron is transformed into a 20-kW power-adjustable phase-locked magnetron, which can then be injection-locked with tunable power output. For the first-time ever, the output power of the injection-locked magnetron is continuously tuned from 2 to 19 kW. This large-power magnetron is both phase and amplitude controlled, and is useful for the coherent power combining of multiple magnetrons. The magnetron frequency pushing effect, which affects the injection-locked frequency range of the phase-locked magnetron, is observed in both simulations and measurements. In the injection-locking experiments, the locking bandwidth varies from 11.7 to 2.4 MHz when the output power is tuned from 5 to 19.1 kW and the injection power is kept at 120 W. Moreover, the center frequency of the phase-locked magnetron increases with increasing output power. [ABSTRACT FROM AUTHOR]

Microwave power combining based on dual 15-kW continuous-wave (CW) magnetrons in S-band is presented. The injection locking on 15-kW CW magnetrons has been successfully accomplished. The phase-locking bandwidth of each magnetron reaches 5 MHz with an improved dc power supply. Meanwhile, phase jitters are measured and analyzed briefly. The injection-locked 15-kW magnetrons have stable magnitude and tunable locked phase, which are suitable for coherent power combining. A dual-magnetron microwave power combining system has been designed and developed with an automatic phase controlling mechanism. The microwave power combining efficiency is higher than 95%. It is the first time to demonstrate a successful microwave power combining of dual 15-kW S-band CW magnetrons. The system will find industrial applications in producing diamond film from microwave plasma chemical vapor deposition. Large-power and high-efficiency microwave sources based on power combining from magnetrons are good candidates for industrial applications. [ABSTRACT FROM PUBLISHER]

Aiming at exploring the basic functional mechanism of superstrates in the resonant cavity antenna (RCA), two popular superstrates, i.e., the homogeneous dielectric superstrate and the periodic microstrip superstrate are investigated. Their reflection coefficients to normal and oblique plane wave incidences are studied by using mathematical derivation and simulations. Based on it, their effects on performances of the RCA are analyzed through simulations and measurements. Results show that, despite of different configurations, the superstrates can be purposely engineered to have the same reflection coefficients, which results in the same improving effect on the RCAs broadside gain, radiation patterns and, more interestingly, broadening effect on the return loss bandwidth. The research demonstrates the key role of their effective reflective characteristics in the RCA, and can inspire more advanced superstrates for RCA designs. [ABSTRACT FROM PUBLISHER]

ABSTRACT The transparent antenna can potentially be combined with solar cells to create multifunctional compact systems. In this article, an optically transparent broadside antenna is presented. Based on a meshed patch antenna which has three horizontal lines and three vertical lines, the antenna has four more lines to increase the bandwidth. The antenna is fed by a top fed for simple structure, and the area of the feed line is much smaller than the one of a side fed. The transparency is much better because of the low ratio of metal area, which can be further reduced without destroying the performance of the antenna. The transparent broadside antenna is studied at 2.5 GHz. On the upper surface of the antenna, the ratio of metal area is 3.2%, and the measured −10 dB impedance bandwidth is close to 60 MHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:146-149, 2015 [ABSTRACT FROM AUTHOR]

To improve the gain of microstrip antenna, it can be realized by artificially introducing metamaterials into microstrip antenna. This paper introduces four kinds of metamaterial structures, such as dendritic-type, cross-type, s-type and h-type. All can improve the antenna performance in varying degrees. Based on the analysis and comparison of the simulated results, we found that the dendritic-type metamaterial microstrip antenna has the most remarkable influence on increasing of the antenna gain with the bandwidth basically unchanged. At last, the simulated results were compared with the measured results. The good agreements can be observed. [ABSTRACT FROM AUTHOR]

A novel planar slot array antenna with omnidirectional radiation pattern in the horizontal plane is proposed. The antenna has a simple structure based on a stripline. Its fabrication employs a low-cost and accurate planar printed technique. A series of rectangular-shaped loop slots are etched on two parallel ground planes, and act as radiators. The basic principle of operation of the antenna is discussed in this study. An antenna with eight back-to-back slots is designed by employing the genetic algorithm (GA) implemented on a cluster system to achieve good omnidirectional radiation characteristics. A prototype antenna is fabricated and measured. The measurement results agree with the simulation data and show that this antenna possesses encouraging features. For example, at the working frequency of 5.8 GHz, it has a well-formed omnidirectional pattern with maximum gain variation less than 0.5 dB in the horizontal plane, a high gain level of 10 dBi, side lobes 10 dB below the main lobe and no beam squint. Meanwhile, this antenna achieves an impedance bandwidth of 4.6% of the center frequency (5.68–5.95 GHz) for S11 < -10 dB and exhibits stable omnidirectional performance over the impedance bandwidth. [ABSTRACT FROM AUTHOR]