Direct Signal Detection Without Data‐Aided: A MIMO Functional Network Approach

Functional network (FN) has been successfully applied in many fields, but so far no methods of direct signal detection (DSD) using FN have been published. In this chapter, a novel DSD approach using FN, which can be applied to cases with a plural source signal sequence, with short sequence, and even with the absence of a training sequence, is presented. Firstly, a multiple‐input multiple‐output FN (MIMOFN), in which the initial input vector is devised via QR decomposition of the receiving signal matrix, is constructed to solve the special issues of DSD. In the meantime, the design method for the neural function of this special MIMOFN is proposed. Then the learning rule for the parameters of neural functions is trained and updated by back‐propagation (BP) algorithm. The correctness and effectiveness of the new approach are verified by simulation results, together with some special simulation phenomena of the algorithm. The proposed method can detect the source sequence directly from the observed output data by utilizing MIMOFN without a training sequence and estimating the channel impulse response

Two-Port CPW-Fed Dual-Band MIMO Antenna for IEEE 802.11 a/b/g Applications

A coplanar waveguide- (CPW-) fed dual-band multiple-input multiple-output (MIMO) antenna for 2.45/5.5 GHz wireless local area network (WLAN) applications is presented in this paper. The presented MIMO antenna consists of two identical trapezoidal radiating elements which are perpendicular to each other. The size of the entire MIMO antenna is 50 × 50 × 1.59 mm3, which is printed on a FR4 substrate. The measured impedance bandwidth of the proposed antenna is 2.25–3.15 GHz and 4.89–5.95 GHz, which can cover IEEE 802.11 a/b/g frequency bands. A rectangular microstrip stub is introduced to achieve a good isolation which is less than −15 dB in both operation frequency bands. The measured peak gain is 5.59 dBi at 2.45 GHz and 5.63 dBi at 5.5 GHz. The measured antenna efficiency is 77.8% and 80.4% in the lower and higher frequency bands, respectively. The ECC values at the lower and higher frequencies are lower than 0.003 and 0.01, respectively

A Low Profile Dual-Band High Gain Directional Antenna for Anti-Interference WLAN Station Applications

This paper presents a low-profile dual-band antenna with directional radiation characteristics for wireless local area network (WLAN) applications. The proposed directional antenna is composed of a coupling microstrip line, two F-shaped strips, two rectangular strips, and a defected ground plane. The measured impedance bandwidth of the proposed antenna is 180 MHz (2.33–2.51 GHz) and 830 MHz (5.09–5.92 GHz), which can cover Institute of Electrical and Electronic Engineers (IEEE) 802.11 a/b/g frequency bands. The dual-band antenna exhibits a desirable directional radiation patterns in the vertical and horizontal planes with the peak gain of 6.55 dBi in the lower frequency band and 8.1 dBi in the higher frequency band. The measured antenna efficiency is 70% at 2.4 GHz and 84.5% at 5.5 GHz. The proposed dual-band WLAN station antenna is designed on a FR4 substrate with overall dimensions of 69 mm × 50 mm × 1.6 mm

Perovskite Micro-Nano Cage SrTiO3: Formation Mechanism, Vacancy Analysis, and Exciton Dynamics

In the former research, we produced the regular polyhedron single-crystalline SrTiO3 particles with multiple crystal facets exposed by a one-step hydrothermal method. In this work, the dissolution process mechanism of SrTiO3 has been analyzed based on the evidence of the crystal structure and particle morphology with a completely new point of view. The anisotropic formation process of perovskite micro-nano cage SrTiO3 was primarily summarized, and the defective vacancy composition was analyzed. Simultaneously, based on femtosecond transient absorption spectroscopy, the exciton dynamic of SrTiO3 was deduced, and it will play a key role in improving the photoelectric properties of SrTiO3. Furthermore, the abundant defective vacancies promote the ability of SrTiO3 to oxidize Co species, which has a great advantage in the wastewater treatment processes

Perovskite Micro-Nano Cage SrTiO3: Formation Mechanism, Vacancy Analysis, and Exciton Dynamics

In the former research, we produced the regular polyhedron single-crystalline SrTiO3 particles with multiple crystal facets exposed by a one-step hydrothermal method. In this work, the dissolution process mechanism of SrTiO3 has been analyzed based on the evidence of the crystal structure and particle morphology with a completely new point of view. The anisotropic formation process of perovskite micro-nano cage SrTiO3 was primarily summarized, and the defective vacancy composition was analyzed. Simultaneously, based on femtosecond transient absorption spectroscopy, the exciton dynamic of SrTiO3 was deduced, and it will play a key role in improving the photoelectric properties of SrTiO3. Furthermore, the abundant defective vacancies promote the ability of SrTiO3 to oxidize Co species, which has a great advantage in the wastewater treatment processes

A MIMO Antenna with High Gain and Enhanced Isolation for WLAN Applications

In this paper, a novel two-port dual-band multiple-input-multiple-output (MIMO) antenna with enhanced isolation and high gain is presented. The presented antenna is composed of a symmetrical ground element and two identical antenna radiating elements. At the bottom of the substrate, the ground part is applied to strengthen the isolation performance of the designed MIMO antenna. The measured −10 dB bandwidth according to the input reflection coefficient S11 are 650 MHz (2.25–2.9 GHz) and 980 MHz (5.05–6.03 GHz), which are in strong agreement with the 2.4 GHz frequency band (2.4–2.4835 GHz) and the 5 GHz frequency band (5.15–5.85 GHz) of wireless local area network (WLAN) applications. The measured S21 at both the lower and the higher frequency operation bands are less than −19.3 dB. In the operating frequency bands, the measured gain is from 1.5 dBi to 3.8 dBi. The measured results show that the presented MIMO antenna is a good candidate for WLAN applications

A MIMO Antenna with High Gain and Enhanced Isolation for WLAN Applications

In this paper, a novel two-port dual-band multiple-input-multiple-output (MIMO) antenna with enhanced isolation and high gain is presented. The presented antenna is composed of a symmetrical ground element and two identical antenna radiating elements. At the bottom of the substrate, the ground part is applied to strengthen the isolation performance of the designed MIMO antenna. The measured −10 dB bandwidth according to the input reflection coefficient S11 are 650 MHz (2.25–2.9 GHz) and 980 MHz (5.05–6.03 GHz), which are in strong agreement with the 2.4 GHz frequency band (2.4–2.4835 GHz) and the 5 GHz frequency band (5.15–5.85 GHz) of wireless local area network (WLAN) applications. The measured S21 at both the lower and the higher frequency operation bands are less than −19.3 dB. In the operating frequency bands, the measured gain is from 1.5 dBi to 3.8 dBi. The measured results show that the presented MIMO antenna is a good candidate for WLAN applications

Minimized Triple-Band Eight-Element Antenna Array for 5G Metal-frame Smartphone Applications

A multiple-input-multiple-output (MIMO) antenna array for triple-band 5G metal-frame smartphone applications is proposed in this paper. Each single antenna element consists of an S-shaped feeding strip and an L-shaped radiation strip on the metal frame. The dimension of the antenna element is only 6.5 mm × 7 mm (0.076 λ0 × 0.082 λ0, λ0 is the free-space wavelength at the frequency of 3.5 GHz). The −6 dB impedance bandwidth of the proposed eight-antenna array can cover 3.3–3.8 GHz, 4.8–5 GHz, and 5.15–5.925 GHz. The evolution design and the analysis of the optimal parameters for a single antenna element are derived to investigate the principle of the antenna. The measured total efficiency is larger than 70%. The measured isolation is better than 13 dB. The measurements of the prototype agree well with the simulation results

Dual-Band MIMO Antenna for 5G/WLAN Mobile Terminals

This paper presents a dual-band four-element multiple-input-multiple-output (MIMO) array for the fifth generation (5G) mobile communication. The proposed antenna is composed of an open-loop ring resonator feeding element and a T-shaped radiating element. The utilization of the open-loop ring resonator not only reduces the size of the antenna element, but also provides positive cross-coupling. The dimension of a single antenna element is 14.9 mm × 7 mm (0.27λ × 0.13λ, where λ is the wavelength of 5.5 GHz). The MIMO antenna exhibits a dual-band feature from 3.3 to 3.84 GHz and 4.61 to 5.91 GHz, which can cover 5G New Radio N78 (3.3–3.8 GHz), 5G China Band N79 (4.8–5 GHz), and IEEE 802.11 ac (5.15–5.35 GHz, 5.725–5.85 GHz). The measured total efficiency and isolation are better than 70% and 15 dB, respectively. The calculated envelope correlation coefficient (ECC) is less than 0.02. The measured results are in good agreement with the simulated results

strong synergistic effect of the (110) and (100) facets of the SrTiO3 perovskite micro/nanocrystal: decreasing the binding energy of exciton and superb photooxidation capability for Co2+

Crystal facet regulation is an effective method for preparing SrTiO3 or other perovskite semiconductor materials with high photochemical catalysis performance. In general, the edge-truncated cube of SrTiO3 micro-nano particles has been widely reported because of the multiple crystal facets exposed at the same time. However, the effect of the (110) facet and the interaction between the (100) and (110) facets on the properties of photo-induced carriers is still not very clear. In this article, we have designed and prepared two edge-truncated cube SrTiO3-a small and large area proportion of the (110) facet, respectively. In addition to the morphological and structural characterization, high-resolution XPS and femtosecond multiphoton transient absorption (fs-TA) spectroscopy were used to detect the atomic vacancy and were applied to confirm the state of carrier transition. The results showed that the larger (110) facet led to two influences-more Sr vacancies and more self-trapping excitons (STEs) with an ultra-low binding energy (E-b = 2.13 meV), about 1.17 meV lower than that of the sample with the smaller (110) facet. In particular, the larger (110) facet also caused a much higher photooxidation performance for Co2+ to Co3+. This study not only enriches the arsenal of SrTiO3 materials but also sheds new insights into the understanding of the synergistic effect essence of the (100) and (110) facets, which could promote the development of new perovskite photocatalytic materials, particularly in the recovery of heavy metals