The development of mobile 5G technology poses new challenges for high-frequency and high-performance filters. However, current commercial acoustic wave filters mainly focus on 4G LTE, which operates below 3 GHz. It is necessary to accelerate research on high-frequency acoustic wave filters. A high-selectivity film bulk acoustic resonator (FBAR) filter chip for the 3.4–3.6 GHz range was designed and fabricated in this paper. The design procedure includes FBAR parameter fitting, filter schematic analysis, and the generation principle of transmission zeros (TZs). The measured results show that the filter chip is of high roll-off and stopband suppression. Most of the stopband suppression is better than 35 dB. Finally, error analysis was conducted, and FBAR parameters were modified after testing for future filter design work.

This paper introduces a low-dropout regulator (LDO) with a quick transient response to the load and no off-chip capacitance. The LDO in this work powers digital modules in system-on-chip (SoC). It has low output voltage variation and fast recovery time during load changes. This paper proposed a novel tri-loop regulation method. The basic loop is a conventional feedback loop for LDO to ensure output voltage accuracy. The transient-enhanced loop is an improved design based on the flipped voltage follower (FVF) that compensates for the effect of removing off-chip capacitance on circuit stability. The introduced Miller capacitor is used to form the AC-coupled loop, further ensuring pole separation. It is worth mentioning that this paper introduces 2 FVFs for building basic loop and transient-enhanced loop. In addition, a bandgap reference (BGR) with a self-starting circuit is designed in this paper. The LDO described in this paper operates at 5V. The LDO is based on a 0.18 um CMOS process. The dropping and rising voltages are merely 24.5 mV and 25 mV when the load current (I ) fluctuates between 1 and 50 mA. And the corresponding settling times are 2.5 us and 1.9 us respectively. The LDO described in this paper has an output of 1.8 V and the load regulation (LDR) is as low as 6.68 uV/mA.

“Authorized Shared Access” (ASA) is a spectrum management policy which enables the secondary system to opportunistically utilize the licensed spectrum of the primary systems. In the coexistence of LTE-A system with primary systems, one of the constituent cells of the CoMP cooperating set may be affected because it has to vacate the ASA frequency for it overlaps with the protected area of the primary system. As a result, the CoMP cooperating set will be changed, and the operation of the CoMP can’t be continued execution. In this case, the UE’s QoS can’t be guaranteed and even the UE experiences call drop when using the traditional method. In this paper, by utilizing a central controller, we propose an efficient method for managing CoMP cooperating set on the ASA spectrum. The change information about the affected cell is sent to the serving cell of the CoMP through the central controller in advance. Then, the serving cell may reselect a new CoMP cooperating set or determine CoMP information indicating whether the CoMP cooperating set will be continued based on this change information, which effectively ensures continued execution of CoMP and the UE’s QoS. Simulation results show that the proposed method can provide better performance compared with the traditional method.

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