Advanced RF filters for wireless communications

This paper provides a comprehensive review of advanced radio fre-quency(RF)filter technologies available in miniature chip or inte-grated circuit(IC)form for wireless communication applications.The RF filter technologies were organized according to the time-line of their introduction,in conjunction with each generation of wireless(cellular)communication standards(1G to 5G).This ap-proach enabled a clear explanation of the corresponding invention history,working principles,typical applications and future develop-ment trends.The article covered commercially successful acoustic filter technologies,including the widely used surface acoustic wave(SAW)and bulk acoustic wave(BAW)filters,as well as electromag-netic filter technologies based on low-temperature co-fired ceramic(LTCC)and integrated passive device(IPD).Additionally,emerg-ing filter technologies such as IHP-SAW,suspended thin-film lithium niobate(LiNbO3 or LN)resonant devices and hybrid were also dis-cussed.In order to achieve higher performance,smaller form factor and lower cost for the wireless communication industry,it is believed that fundamental breakthroughs in materials and fabrication tech-niques are necessary for the future development of RF filters.

A Q-Enhanced CMOS RF Filter for Multi-Band Wireless Communications

An RF bandpass filter with a Q-enhancement active inductor is presented. The design technique for a tunable Q-enhancement CMOS active inductor operating in the wide RF-band is described. Moreover,issues related to noise and stability of the active inductor are explained. The filter was fabricated in 0.18μm CMOS technolo- gy,and the circuit occupied an active area of only 150μm ×200μm. Measurement results show that the filter centered at 2. 44GHz with about 60MHz bandwidth （3dB） is tunable in center frequency from about 2.07 to 2. 44GHz. The ldB compression point is - 15dBm while consuming 10. 8mW of DC power,and a maximum quality factor of 103 is attained at the center frequency of 2.07GHz.

A novel SMC-PHD filter based on particle compensation

As a typical implementation of the probability hypothesis density(PHD) filter, sequential Monte Carlo PHD(SMC-PHD) is widely employed in highly nonlinear systems. However, the particle impoverishment problem introduced by the resampling step, together with the high computational burden problem, may lead to performance degradation and restrain the use of SMC-PHD filter in practical applications. In this work, a novel SMC-PHD filter based on particle compensation is proposed to solve above problems. Firstly, according to a comprehensive analysis on the particle impoverishment problem, a new particle generating mechanism is developed to compensate the particles. Then, all the particles are integrated into the SMC-PHD filter framework. Simulation results demonstrate that, in comparison with the SMC-PHD filter, proposed PC-SMC-PHD filter is capable of overcoming the particle impoverishment problem, as well as improving the processing rate for a certain tracking accuracy in different scenarios.

Performanceanalysisofalowpowerlownoisetunablebandpassfilterformultiband RF front end

This paper presents a low power tunable active inductor and RF band pass filter suitable for multiband RF front end circuits. The active inductor circuit uses the PMOS cascode structure as the negative transconductor of a gyrator to reduce the noise voltage. Also, this structure provides possible negative resistance to reduce the inductor loss with wide inductive bandwidth and high resonance frequency. The RF band pass filter is realized using the proposed active inductor with suitable input and output buffer stages. The tuning of the center frequency for multiband operation is achieved through the controllable current source. The designed active inductor and RF band pass filter are simulated in 180 nm and 45 nm CMOS process using the Synopsys HSPICE simulation tool and their performances are compared. The parameters, such as resonance frequency, tuning capability, noise and power dissipation, are analyzed for these CMOS technologies and discussed. The design of a third order band pass filter using an active inductor is also presented.

Two-Dimensional Coupling Vibration Analysis of Laterally Acoustically Coupled Two-Port Thin-Film Bulk Acoustic Resonators

In this paper,we present an approach to studying the mode coupling vibrations in two-port thin-film bulk acoustic wave resonator(FBAR)devices with two pairs of electrodes deposited on the zinc oxide film.The two-dimensional plate theory established in our previous work is employed,which takes into account the coupling of the operating thickness-extensional mode with the extensional,flexural,fundamental and second-order thickness-shear modes.The propagation of straight-crested waves in the plate is studied,and the state-vector approach is successfully used to simplify the derivation process.For a structurally symmetric device,the modes are separated into quasi symmetric and antisymmetric ones.Frequency spectra and corresponding mode shapes are obtained under the stress-free boundary conditions,respectively,and then coupling effects and energy trapping phenomenon are discussed in detail.Some results for structures with asymmetric electrode distributions are also shown.It is found that the choice of aspect ratio has a great effect on mode couplings of FBAR devices.This study will be useful for the design of FBAR filters and sensors.