Yulin Huang

A 4-bit switched-line phase shifter based on MEMS switches

This paper presented a 4-bit switched-line phase shifter based on the metal-contact SPDT RF MEMS switches. The phase shift module was fabricated on a 20mil RO4350 substrate and mounted with its driver module on an Aluminum platform. This electrically tunable phase shifter is suitable for taking place of mechanical phase shifters used in base station. Measurements indicated a maximum phase shift of 75 degree with a step of 5 degree, a maximum insertion loss of 0.89dB and a minimum return loss of 13.4dB at 2.7GHz. The phase accuracy is within 2 degree at 2.7 GHz.

Frequency domain FEM analysis of reflector scattering characteristics for SAW tags

This paper proposes a frequency domain analysis (FDA) based on the finite element method (FEM) for calculating reflector scattering characteristics of SAW tags. This method is applicable not only to devices employing conventional single-crystal substrates but also multi-layered ones. First, reflection characteristics are calculated for a short reflector on 128°YX-LiNbO3 and compared with the result previously reported. Then the method is applied to short reflectors on the AlN/Si layered structure, and their applicability to SAW tags is discussed.

SAW/BAW band reject filters embedded in impedance converter

This paper discusses SAW-BAW-based band reject filters. They are composed of the impedance converters, where capacitive elements are replaced with SAW/BAW resonators. First, basic properties of the unit cell are studied. It is shown how basic properties of a unit cell change with the design. It is also shown that when two notches caused by the resonators are placed in proximity, two synergy effects occur: (i) an extra matching point appears on one side of the transition band. This make the insertion loss at the point smaller and the transition band steeper, and (ii) the dip level becomes deeper, and the total rejection level becomes better. Then, the wide rejection band filter is designed by cascading multi-stages, and effectiveness of the device configurations is demonstrated.

A 1.7–2.7-GHz 4-bit Phase shifter based on packaged RF MEMS switches

This study presents a 4-bit phase shifter with a maximum phase shift degree of 75° based on packaged metal-contact single-pole double-throw (SPDT) radio frequency microelectromechanical system (RF MEMS) switches mounted on a 20 mil RO4350 substrate and assembled with its driver module on a 4-layer printed circuit board (PCB) board. Electric length of 10° and characteristic impedance of 61.7 Ω are selected for T-stub matching. Standard PCB processing makes it easy to develop and suitable for taking place of mechanical tilt employed in recent base station. Measurements indicate a maximum insertion loss of 1.37 dB at 2.7 GHz and a minimum return loss of 11.71 dB. The phase accuracy is within 1.75° at 2.7 GHz.

Influence of coupling between Rayleigh and SH SAWs on rotated Y-cut LiNbO 3 to their electromechanical coupling factor

Suppression of the SH-SAW response is mandatory to design TC SAW devices on θ degree rotated Y-cut LiNbO<inf>3</inf>. However, it is not easy because K² for SH SAW changes rapidly with θ, and its optimal value in terms of the SH-SAW suppression is dependent on electrode and SiO<inf>2</inf> thicknesses. The authors found that the optimal θ always locates close to θ where difference in velocities of two SAWs is minimum. This suggested that their coupling is responsible for variation of their K².

Multimode filter composed of single-mode surface acoustic wave/bulk acoustic wave resonators

This paper discusses the possibility of realizing multimode filters composed of multiple single-mode resonators by using radio frequency surface and bulk acoustic wave (SAW/BAW) technologies. First, the filter operation and design principle are given. It is shown that excellent filter characteristics are achievable by combining multiple single-mode resonators with identical capacitance ratios provided that their resonance frequencies and clamped capacitances are set properly. Next, the effect of balun performance is investigated. It is shown that the total filter performance is significantly degraded by balun imperfections such as the common-mode rejection. Then, two circuits are proposed to improve the common-mode rejection, and their effectiveness is demonstrated.

Design Consideration of SAW/BAW Band Reject Filters Embedded in Impedance Converter

This paper discusses design of surface acoustic wave/bulk acoustic wave (SAW/BAW)-based band reject filters composed of the impedance converters, where capacitive elements are replaced with SAW/BAW resonators. First, basic properties of the unit cell are studied. It is shown how basic properties of a unit cell change with the design. It is also shown that when two notches caused by the resonators are placed in proximity, two synergy effects occur: 1) an extra matching point appears on one side of the transition band. This makes the insertion loss at the point smaller and the transition band steeper and 2) the dip level becomes deeper, and the total rejection level improves. Then, two resonators are fabricated, measured, and combined with inductors in circuit simulator to demonstrate functionality of the basic cell design. Finally, the wide rejection band filter is designed by cascading multistages, and effectiveness of the device configurations is demonstrated.