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Abstract Passive intermodulation (PIM) is usually expressed by the third‐order intermodulation power excited by two‐tone signal, which has limitations in characterising nonlinear distortion of signal in actual communication system. The effect of PIM on modulated signals are analysed at both the transmit and receive port with multiple passive nonlinear sources. Four types of coaxial connectors are adopted to represent four different levels of PIM. The equivalent circuits of PIM sources in series or parallel are proposed. With the circuit simulations and theoretical modelling, the effect of PIM on the analog and the digital modulation signals are analysed respectively. Two indexes of adjacent channel leakage ratio and error vector magnitude are modelled, showing the PIM effect at transmit port. A system model of a transmit‐receiver is provided, investigating the effect of PIM on the symbol error rate in a receiver. The effects of PIM distortion on different modulated signals are observed both in experimental measurements and simulation tests, verifying the theoretical models.

Abstract Third‐order intermodulation (IM3) is considered as a typical metric to evaluate passive intermodulation (PIM) in electrical connectors, which may be affected by the second‐order effect in the circuit with cascaded non‐linearities. In this study, the effects of second harmonics and second‐order intermodulation on the IM3 powers were theoretically modelled and experimentally verified. Combined with mathematical modelling, an equivalent circuit model of a passive non‐linear source was presented to investigate the effect of second‐order signals on the IM3 powers. A modified non‐linear transfer function was developed by considering multiple non‐linear superpositions in cascaded non‐linearities. Based on the designed two‐tone test, a mathematical expression was provided with the determination of correlation model coefficients. Numerical simulations were performed by using the proposed model, demonstrating the effect of signals induced by the second‐order non‐linearity on the IM3 powers in series passive components. The IM3 powers resulting from cascaded connectors associated with different signal frequencies were predicted. Coaxial connector samples were designed as cascaded PIM sources in circuits, which were experimentally measured in a GSM 900 MHz frequency band. Good agreement was obtained between the predictions and measurements with error of 0.76 dB in average.

This paper presents a high precision adaptive slope compensation circuit for for DC -DC converter in wearable devices. Compared with the traditional adaptive slope compensation circuit, the comparator is used to sample the output voltage and input voltage, which greatly improves the accuracy.ln this paper, the circuit is designed in UMC 0.18-p,m CMOS Technology and verified by Virtuoso Spectre Circuit Simulator. The simulation results show that the accuracy of the adaptive slope compensation circuit in this paper can reach more than 96%.

Further to China’s plan that was introduced in 2017 for attracting more students into engineering, many Chinese universities have started to explore new teaching methods that can be adopted into their programs. This shift was geared towards developing student-centred teaching materials rather than traditional teacher centred instruction. In this manuscript, we compare two different methods of instruction for a course on energy harvesting using embedded systems. We describe the learning materials and showcase the impact that project-based learning has had on a cohort of Chinese students that were enrolled in a joint master’s program between the University of Electronic Science and Technology of China (UESTC) and the Royal Institute of Technology (KTH). KTH has made remarkable progress in the teaching of embedded systems technology for energy harvesting applications, with great emphasis on active as well as collaborative learning. We demonstrate two examples of projects that Chinese students have completed in KTH and present evaluative data regarding their experiences. Our results show that KTH’s approach in teaching this module has had a positive impact on student learning, with an average of 80% of students think that teaching in KTH is conducive to students’ independent exploration.

This paper proposes a 16-bit 6-channel high-voltage successive approximation register (SAR) ADC with an optimized 5 + 5 + 6 segmented capacitor array. The lower 10 bits of the capacitor array are all composed of unit capacitors without any calibration unit. Without calibration, the lower 10 bits of the capacitor array can ensure 10-bit conversion accuracy. Every of the upper 6 bits of the capacitor array contains a linearity calibration unit. The linearity error of the upper 6 bits is calibrated by the linearity calibration unit. The 16-bit is manufactured by a $0.6~\mu m$ standard COMS process, and the total chip area of 6-channel ADC including pads is 6.6mm $\times6.6$ mm. As for single channel SAR ADC, the area is 0.9mm $\times2.0$ mm. The measurement results show that the effective conversion accuracy of the SAR ADC reaches 13 bits by using novel differential nonlinearity (DNL) and integral nonlinearity (INL) calibration methods. The power is 80mW, corresponding to a Figure of Merit (FOM) of 48 pJ/conv.-step.

This article introduces a novel Ultra Wide Band (UWB) Multiple Input Multiple Output (MIMO) antenna with Triple-band notched characteristics. The overall dimensions of the antenna are 18 × 34 mm2. The designed antenna has two similar flower-shaped radiators with L-shape strips, common ground with two flag-shaped decoupling stubs and T-shape strips for notched band characteristics. Two flag-shaped stubs are used to achieve 22 dB improved isolation. The S11 of the designed antenna is less than −10 dB between 3.07 GHz and 12.40 GHz, having various stopped bands of WiMAX, WLAN and X bands. The presented antenna is examined and investigated in terms of S-parameters, Mutual Coupling, Gain, Envelope Correlation Coefficient (ECC), Efficiency and Diversity Gain (DG).

This paper presents a statistics-optimized organization technique to achieve better element matching in successive approximation register (SAR) analog-to-digital converter (ADC) in smart sensor systems. We demonstrate the proposed technique ability to achieve a significant improvement of around 23 dB on a spurious free dynamic range (SFDR) of the ADC than the conventional, testing with a capacitor mismatch σu = 0.2% in a 14-bit SAR ADC system. For the static performance, the max root mean square (rms) value of differential nonlinearity reduces from 1.63 to 0.20 LSB and the max rms value of integral nonlinearity (INL) reduces from 2.10 to 0.21 LSB. In addition, it is demonstrated that by applying grouping optimization and strategy optimization, the performance boosting on the SFDR can be effectively achieved. Such a great improvement on the resolution of the ADC only requires an off-line pre-processing digital part.

A novel 4th-order cross-coupled electrical tunable bandpass filter with constant absolute bandwidth and high frequency selectivity is proposed. The electric coupling coefficients and the magnetic coupling coefficients of the cross-coupled resonators and the external quality factor of the tunable filter are investigated. The design curves of coupling coefficients and external quality factor versus the resonant frequency are synthesized for the cross-coupled tunable filter. Tunable resonator with separate electric dominant and magnetic dominant coupling regions is designed to build the cross-coupled tunable filter topology. Theoretical analysis is derived to estimate the coupling coefficients and the performance of the proposed filter. A prototype is fabricated and measured. The measurement shows that the filter has a −3 dB bandwidth of 117 ± 3MHz from 0.95 to 1.48 GHz. Two cross-coupled transmission zeros beside the passband are generated, and the frequency selectivity is enhanced. The −30 dB/−3 dB bandwidth shape factor is 1.83~1.93.

In this paper, an underlay cognitive radio system, which consists of a primary-user (PU) transmitter (TX), a PU receiver (RX), a secondary-user (SU) TX, and a SU_RX, is considered. Benefitting from the underlay mode, SU_TX can deliver its information to SU_RX by sharing the spectrum resource authorized to PU. It is assumed that SUs are equipped with a single transmitting antenna and a single receiving antenna, which are isolated, and work in full-duplex (FD) mode. By considering that the information signal transmitted from PU_TX to PU_RX may be eavesdropped by SU_TX if SU_TX is malicious, we investigate the secrecy outage performance of the PU system. The approximated closed-form expression for secrecy outage probability (SOP) and the lower boundary of the asymptotic SOP have been derived and verified by simulation results. Our results reveal the impact of the eavesdropping of the SU and the FD mode adopted at the SU transmitter on the secrecy performance of the PU system in underlay spectrum sharing mode.

In this study, nanocrystalline ZnAl2O4 (ZA) were introduced to Z-type barium hexaferrite (Co2Z) and the effects of ZA addition upon the crystal-phase composition, microstructure, permeability and permittivity as well as losses characteristics over a wide frequency range of 10 MHz–1 GHz have been systematically investigated. With increasing ZA content (x) from 0 to 15 wt%, the permeability μ′ at low frequencies decreased from 12.0 to 4.3, while the permittivity ε′ was decreased from 27.4 to 10.7. Correspondingly, the frequency stability of permeability and permittivity were improved and the losses were effectively reduced. When x is in the range of 5–10 wt%, the magnetic loss tan δμ is in the order of 10-2 and the dielectric loss tan δε is in the order of 10-3 at 300 MHz, which is lower by one order of magnitude compared with that of undoped Co2Z. The modified magnetic and dielectric properties are closely related to the changing phase composition and microstructure.