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In this Letter, we report on high-tunability and low-microwave-loss properties of Ba0.6Sr0.4TiO3 (BST) thin films by use of atomic-layer-deposited TiO2 films as the microwave buffer layer between BST and high-resistivity Si substrate. The interdigital capacitor fabricated on BST films grown on TiO2∕high resistivity Si (2kΩcm) substrates showed the much enhanced tunability value of 33.2% while retaining an appropriate Q factor, as compared to the tunability values of BST (21%) films grown on MgO single-crystal substrates and BST (8.2%) films grown on TiO2∕normal Si (10Ωcm) substrates. The coplanar waveguide BST phase shifter fabricated on TiO2∕high resistivity Si exhibited a phase shift of 95° and insertion loss of 3.09 dB at 15 GHz and an applied voltage of 50 V. ALD-grown TiO2 buffer layers enable the successful integration of BST-based microwave tunable devices onto high-resistivity Si wafers.

is below 2 from 8.2 GHz to 14.5 GHz. It is shown that the frequency band is very broader. Figure 3 demonstrates the magnitude distribution of electric field on the radiation patch. It is found that the grooves play an important role in the impedance matching. The grooves also largely affect the HPBW over the whole frequency band. Simultaneously, side curve edges also heavily affect the HPBW.The measured radiation patterns (E-plane and H-plane) are shown in Figures 4-6. It is shown that the HPBW of pattern at 8.4 GHz achieves 118°in E-plane, and 111°in H-plane. At the frequencies of 10.5 GHz and 12.6 GHz, the HPBW of E-plane are 119°and 114°, respectively. Both the HPBWs are 120°in the H-planes. The measured results show that this new antenna possesses the steady HPBW performance from 8.4 GHz to 12.6 GHz. It is verified that proposed antenna has good performance for wide scan phased array. CONCLUSIONA compact size linearly tapered slot antenna has been successfully investigated. Measured results show that the proposed antenna is with wider frequency band. Its half-power beamwidths are broader over the whole frequency band. ABSTRACT: In this article, g /2 open stub bandpass filters with flexible narrow bandwidth on duroid substrate are presented. This filters show flexible bandwidth with variation of the position of the open stubs using the external quality factor, Q e without changing the impedance value at microwave range. On the other hand, by replacing the series quarter-wavelength connecting-lines with the equivalent T-shaped line, a compact stub bandpass filter with second harmonic suppression can be obtained. This filter shows the insertion loss of 1.2 dB and the return loss of 21.9 dB at the center frequency of 5.8 GHz.Figure 6 Narrow-bandwidth BPF with g /2 open stubs and FBW of 10%. (a) The flexible BPF for narrow bandwidth. (b) The new type of BPF for the second harmonic suppression. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]

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This article proposed a new high‐QL resonator with a combination of a double spiral resonator and single split ring resonator with μ‐ near zero metamaterial.It is applied to the design of an X‐band oscillator. A very low phase noise for the oscillator can be obtained due to its sharp band‐ rejection characteristic of the new resonator. The oscillator is designed to operate at 9.2 GHz using the new resonator. Experimental results show the output power is 14.13 dBm, the second harmonic suppression is −46.33 dBc, and the phase noise is −104.54 dBc/Hz at 100‐kHz offset. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1577–1582, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26867

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