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Microwave microfluidic sensors have been employed for dielectric characterization of different liquids. Intuitively, the microfluidic channel plays a vital role in determining the sensor performance. In this article, for the first time, numerical optimization design of microfluidic channel route is carried out with the aim of improving the sensor sensitivity. Two swarm intelligence algorithms, i.e., particle-ant colony optimization algorithm and wolf colony algorithm, are implemented for the route optimization. Through the developed optimization procedure, the sensor sensitivity of the original design can be increased significantly. Several prototypes of optimized sensors are fabricated and tested, and they exhibit good capability in retrieving the liquid properties. In comparison with original complementary split-ring resonator-based sensor with a sensitivity of 0.308% for water measurement, the optimized sensor achieves a high sensitivity value of 0.55%, i.e., the sensor sensitivity is increased by 78.6% after optimization. The developed methodology can also be used in other designs, such as series LC -based sensor, whose sensitivity can be improved by about 50%. It is demonstrated that the developed methodology possesses good automatic optimization ability and universality for the optimal design of microwave microfluidic sensors.

This article presents a novel class of dual-mode substrate-integrated waveguide (SIW) bandpass filters exploiting perturbed SIW rectangular cavities. By introducing metallized via-holes along the central line of an SIW rectangular cavity, the resonant frequency of TE101 mode can be shifted close to that of TE201 mode, thus creating a dual-mode resonator. This structure implements a doublet, which provides two poles and one or two transmission zeros (TZs). The pass bandwidth, spurious-free bandwidth, and positions of the TZs can be fully controlled by modifying the length of the perturbation, the side ratio of the rectangular cavity, and the offset of the input/output ports, respectively. Eight two-pole SIW filters are designed and investigated to demonstrate the high design flexibility. Moreover, a four-pole SIW filter with the asymmetric response and a five-pole SIW filter with quasi-elliptic response are designed, fabricated, and measured to describe the extension of the proposed approach to higher order filters.

In this letter, a 24-GHz high-isolation ON–OFF keying (OOK) modulator with reduced input impedance variation in a 65-nm CMOS technology is proposed. A modified magnetic coupled triple-cascode configuration with a series inductor and two shunt transistors, which can simultaneously improve the ON/OFF isolation and reduce the input return loss variation between the ON- and OFF-states, is designed and analyzed for the first time. Based on this configuration, the OOK modulator achieves a 45.7-dB ON/OFF isolation and maintains better than 10-dB return loss for both the ON- and OFF-states. In addition, a data rate of 3.3 Gbps is achieved.

An explosion field is random and nonuniform, and test sensors can be damaged by fragments during blast wave monitoring. When accurately and comprehensively obtaining the experimental data and the dynamic distributions from an explosion field, the quantity and positioning of sensors during blast wave monitoring are important parameters. In this paper, an optimization method of sensor placement based on an improved inertia and adaptive particle swarm optimization (IIAPSO) algorithm is proposed to solve this problem. This work considers two new aspects: 1) the adaptive mutation mechanism and the inertia weight into classic particle swarm optimization (PSO) and 2) the propagation law of blast waves, the data errors and the probability of sensor damage during IIAPSO. These mechanisms are employed to enhance the global search ability and to increase data accuracy. First, the 12 benchmark functions are utilized to test the performance of the IIAPSO. The performance of the IIAPSO is compared with PSO, linear decreasing weighted particle swarm optimization (LDW-PSO) and adaptive particle swarm optimization (APSO) in terms of parameter accuracy and convergence speed. The results confirm that the proposed IIAPSO is more successful than PSO, LDW-PSO and APSO algorithms. Finally, the IIAPSO is used to optimize the sensor placement in an explosion field. The simulation and experimental results show that the feasibility of this algorithm is demonstrated.

This letter presents a miniaturized eighth-mode substrate-integrated waveguide (EMSIW) filter with tunable center frequency and variable bandwidth. The filter uses a stub-capacitor-loaded EMSIW structure which not only achieves miniaturization but also tunes the center frequency. The edge electrical coupling strength between the two resonators can be adjusted by loading varactor to achieve the bandwidth tunability. In addition, two transmission zeros are introduced to improve the upper stopband rejection. Both the simulated and measured results show a center frequency tuning range of 2.17–2.72 GHz, as well as demonstrate a 3-dB BW tuning range of 140–208 MHz around 2.17 GHz, 231–355 MHz around 2.45 GHz, and 314–435 MHz around 2.72 GHz. The measured insertion loss is 1.7–4.8 dB, and the return loss is better than 10 dB for all tuning ranges.

This letter presents a half-mode substrate integrated cavity bandpass filter with both continuous center frequency and 3 dB bandwidth tuning capabilities. The filter adopts a superposed two layers PCB with lumped varactors loading the central resonator to tune the center frequency. The first-invented semicircular metal sheet on the center rod not only reduces the filter size given a certain resonant frequency significantly by increasing the capacitance between the semicircular metal and the upper ground metal but also facilitates fine frequency tuning by using appropriate varactor $C_{\mathrm{tune}}$ . Surface mount varactors between two resonators change the inter-resonator coupling to adjust the 3 dB BW. Another varactor on the feed line can be used to adjust the external coupling. This filter demonstrates a BW range of 75–130 MHz around 1.5 GHz, a 3 dB BW range of 46–130 MHz around 1.3 GHz and a 3 dB BW range of 55–90 MHz around 1.11 GHz with 10 dB minimum return loss. Insertion loss ranging from 2.262 dB to 7 dB have been obtained.

A novel varactor tunable dual-band bandpass filter (BPF) using stub-loaded stepped-impedance resonators is proposed in this letter. Compared with the traditional tunable filters, the source-load coupling and T-shape stub-loaded lines are employed in this design. The proposed BPF architecture has the advantages of high selectivity and less control voltages. In the overall tuning range, the proposed filter is designed with 5–6 transmission zeros and more than 30 dB rejection between the two passbands. Meanwhile, only one control voltage is needed for each passband. A prototype of this filter is fabricated and measured. The measurement results show great agreement with simulated results, which show that the first passband can be tuned in a frequency range from 0.8 to 1.02 GHz, and the second passband varies from 2.02 to 2.48 GHz.

A 0.9 V third-order double-sampled delta-sigma audio ADC is presented. A new method using a combination of a switched-RC technique and a floating switched-capacitor double-sampling configuration enabled low-voltage operation without clock boosting or bootstrapping. A three-level quantizer with simple dynamic element matching was used to improve linearity. The prototype IC implemented in a 0.13 CMOS process achieves 92 dB DR, 91 dB SNR and 89 dB SNDR in a 24 kHz audio signal bandwidth, while consuming 1.5 mW from a 0.9 V supply. The prototype operates from 0.65 V to 1.5 V supply with minimal performance degradation.