Jingfu Bao

An Novel Compact Quadrature Hybrid Using Broadside-Coupled Meander Lines

In this paper, we present a novel compact 3-dB quadrature directional coupler by introducing Hilbert curve to the conventional meander line structure. The proposed coupler uses a modified broadside coupled meander lines featuring Hilbert curves to achieve a smaller size. The structure of the coupler is suitable for multilayer printed circuit board (PCB) implementation. The proposed coupler with an operation range of 470 MHz–860 MHz is verified by the accordance of simulation and measurement with a measured return loss and isolation better than 19 dB and exhibiting a coupling of 3.4±0.5 dB in the working frequency range. The dimension of the manufactured coupler is 11.50 mm × 8.90 mm × 1.70 mm. It is the smallest coupler to the authors knowledge in the frequency range of 470–860 MHz.

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.

X-band low phase noise push–push oscillator utilizing High-Q differential transmission line loaded with multiple split-ring resonator

In this study, a low phase noise X-band push–push oscillator is presented employing the differential transmission lines (TLs) loaded with multiple split-ring resonator (M-SRR). In order to enhance the coupling strength between TL and resonator cell, the single M-SRR is replaced by the coupled M-SRR cell-pair in differential TL to obtain high-frequency selectivity and deep insertion loss. The resonance properties of the differential TL have been discussed with different coupling configurations and coupling strengths of the M-SRR cell-pair, and the geometries of the proposed structure are investigated to obtain the optimum resonance properties. The loaded Q-factor of the proposed differential TL adopting 3-stages cascaded array of M-SRR cell-pairs configuration is 892 from measured results. Due to the high-Q and anti-phase current properties of the differential TL, a X-band push–push oscillator with low phase noise and superior fundamental frequency suppression performances is realized. The fabricated push–push oscillator operates at 9.52 GHz with an output power of 2.7 dBm and a fundamental frequency suppression of −54.55 dBc. It shows a measured phase noise of −115.48 dBc/Hz at 100 kHz offset frequency and a figure of merit of −201.23 dBc/Hz.

A phononic crystal strip based on silicon for support tether applications in silicon-based MEMS resonators and effects of temperature and dopant on its band gap characteristics

Phononic crystals (PnCs) and n-type doped silicon technique have been widely employed in silicon-based MEMS resonators to obtain high quality factor (Q) as well as temperature-induced frequency stability. For the PnCs, their band gaps play an important role in the acoustic wave propagation. Also, the temperature and dopant doped into silicon can cause the change in its material properties such as elastic constants, Young’s modulus. Therefore, in order to design the simultaneous high Q and frequency stability silicon-based MEMS resonators by two these techniques, a careful design should study effects of temperature and dopant on the band gap characteristics to examine the acoustic wave propagation in the PnC. Based on these, this paper presents (1) a proposed silicon-based PnC strip structure for support tether applications in low frequency silicon-based MEMS resonators, (2) influences of temperature and dopant on band gap characteristics of the PnC strips. The simulation results show that the largest band...

Perturbation analysis of nonlinear signal generation in radio frequency bulk acoustic wave resonators

This paper describes perturbation analysis of nonlinear signal generation in radio frequency (RF) bulk acoustic wave (BAW) devices. Nonlinear constitutive equations with the h form are used where the electric flux density is an independent variable. In conventional ones with the e form, the electric flux density is a dependent variable. This choice makes generated nonlinear fields satisfy Gauss law for electricity automatically. It is shown that non-linear characteristics of RF BAW devices can be simulated well by the simple first order perturbation analysis, and the harmonic balance analysis is not necessary. Origin of the nonlinearity is also discussed.

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.