A Study on the Frequency-Domain Black-Box Modeling Method for the Nonlinear Behavioral Level Conduction Immunity of Integrated Circuits Based on X-Parameter Theory.

During circuit conduction immunity simulation assessments, the existing black-box modeling methods for chips generally involve the use of time-domain-based modeling methods or ICIM-CI binary decision models, which can provide approximate immunity assessments but require a high number of tests to be performed when carrying out broadband immunity assessments, as well as having a long modeling time and demonstrating poor reproducibility and insufficient accuracy in capturing the complex electromagnetic response in the frequency domain. To address these issues, in this paper, we propose a novel frequency-domain broadband model (Sensi-Freq-Model) of IC conduction susceptibility that accurately quantifies the conduction immunity of components in the frequency domain and builds a model of the IC based on the quantized data. The method provides high fitting accuracy in the frequency domain, which significantly improves the accuracy of circuit broadband design. The generated model retains as much information within the frequency-domain broadband as possible and reduces the need to rebuild the model under changing electromagnetic environments, thereby enhancing the portability and repeatability of the model. The ability to reduce the modeling time of the chip greatly improves modeling efficiency and circuit design. The results of this study show that the "Sensi-Freq-Model" reduces the broadband modeling time by about 90% compared to the traditional ICIM-CI method and improves the normalized mean square error (NMSE) by 18.5 dB.

Low-noise co-arm differential sensor for an optical frequency comb sampling an E-field test system.

Optical frequency comb (OFC) technology can realize the rapid measurement of electric fields (E-fields) with large bandwidth. However, this technology suffers from the problem of high intensity noise, resulting in low sensitivity and a blind frequency region. In order to solve the above problems, a dual-path optical E-field sensor with a common reference arm based on a lithium niobate optical waveguide is proposed. The introduction of the reference arm improves the balance of optical paths and the degree of integration. A segmented electrode is also designed to ensure the generation of reverse electrical signals on two Mach-Zehnder interferometers (MZIs). After exiting from the differential photodetector (PD), the intensity noise can be removed, and the sensitivity of the sensor can be improved. After testing, the maximum intensity noise reduction is about 37 dB, the average noise reduction is about 22.3 dB, and the blind frequency region can be eliminated with the co-arm differential optical E-field (CDOE) sensor in the process of measuring the signal. This sensor can be used in the 1 MHz-12 GHz bandwidth with a sensitivity better than 10 mV/m·âˆšHz.

Electromagnetic Susceptibility Analysis of the Operational Amplifier to Conducted EMI Injected through the Power Supply Port.

Operational amplifiers (op-amps) are widely used in circuit systems. The increasing complexity of the power supply network has led to the susceptibility of the power supply port to electromagnetic interference (EMI) in circuit systems. Therefore, it is necessary to investigate the electromagnetic susceptibility (EMS) of op-amps at the power supply port. In this paper, we assessed the effect of EMI on the operational performance of op-amps through the power supply port by a bulk current injection (BCI) method. Firstly, we conducted the continuous sine wave into the power supply port by a current injection probe and measured the change in the offset voltage under EMI. Secondly, we proposed a new method of conducted susceptibility and obtained the susceptibility threshold regularities of the op-amps at the power supply port under the interference of different waveform signals. Our study provided conclusive evidence that EMI reduced the reliability of the op-amp by affecting the offset voltage of op-amps and demonstrated that the sensitivity type of op-amps was peak-sensitive at the power supply port. This study contributed to a deep understanding of the EMS mechanism and guided the design of electromagnetic compatibility (EMC) of op-amps.

Bandpass filter and frequency-time mapping method for pulse measurement with optical delay.

The pulse signal's transients and low duty cycle characteristics lead to excessive omission and erroneous amplitude measurement in signal capture. We offer a combined microwave photonics frequency-time mapping and optical delay electrical pulse measurement system. Beneficial from the true delay of a long fiber with several paths, the pulse is extended to have a more significant duty cycle so as to boost the capturing possibility. We adopt the bandpass filter to avoid sampling the low-frequency range, prevent phase noise from affecting the signal measurement, and improve the signal-to-noise ratio (SNR). This solves the phase noise issue induced by multiple optical delay paths. The proof-of-concept experiments conduct that a 25 µs pulse with a 50 µs period is stretched to a continuous wave, and the SNR is improved by 7 dB.

DOA Estimation Based on Weighted l1-norm Sparse Representation for Low SNR Scenarios.

In this paper, a weighted l1-norm is proposed in a l1-norm-based singular value decomposition (L1-SVD) algorithm, which can suppress spurious peaks and improve accuracy of direction of arrival (DOA) estimation for the low signal-to-noise (SNR) scenarios. The weighted matrix is determined by optimizing the orthogonality of subspace, and the weighted l1-norm is used as the minimum objective function to increase the signal sparsity. Thereby, the weighted matrix makes the l1-norm approximate the original l0-norm. Simulated results of orthogonal frequency division multiplexing (OFDM) signal demonstrate that the proposed algorithm has s narrower main lobe and lower side lobe with the characteristics of fewer snapshots and low sensitivity of misestimated signals, which can improve the resolution and accuracy of DOA estimation. Specifically, the proposed method exhibits a better performance than other works for the low SNR scenarios. Outdoor experimental results of OFDM signals show that the proposed algorithm is superior to other methods with a narrower main lobe and lower side lobe, which can be used for DOA estimation of UAV and pseudo base station.

Coherent Noise Suppression Using Adaptive Homomorphic Filtering for Wideband Electromagnetic Imaging System.

The wideband electromagnetic imaging system using a parabolic reflector is a device for detecting and locating electromagnetic interference sources (EMIS). When multiple coherent interference sources are detected, the confusion will occur due to the coherent noise that is caused by interference phenomenons. Previous works have removed the coherent noise by using iterative techniques, but they face a limitation in removing noise in that the coherent noise pattern changes with frequency in a wideband. In this paper, an adaptive homomorphic filtering is proposed to overcome the limitations of conventional methods from 1 GHz-6 GHz. The coherent noise existing in the several electromagnetic images is studied, and it is confirmed that the variation of the coherent noise pattern is related to the position, the number, and the frequency of EMIS. Then, by analyzing the probability density of coherent noise intensity, an adaptive Gaussian filter is carefully designed to remove coherent noise. The filter parameters are selected by the minimum description length criterion (MDL) to apply to compute directly the local amount of Gaussian smoothing at each pixel of each image. The results of the experiments and simulations demonstrate that the proposed method can significantly improve the quality of electromagnetic images in terms of maximum sidelobe level (MSL) by 15 dB and dynamic range (DR) of the system over 20 dB, compared with conventional narrowband denoising methods.

Dual-comb spectroscopy of methane based on a free-running Erbium-doped fiber laser.

Dual-comb spectroscopy has been developed into a high-precision technique that is capable of sensing many important species of samples, such as methane. Recent studies on single-cavity, dual-comb light sources further reduce the system complexity of such schemes. In contrast to the previous demonstrations around the lasing spectrum, this work significantly expands the spectral coverage of a dual-comb spectroscopy setup using one free-running laser to a region far beyond the laser's emission wavelengths. Nonlinear wavelength conversion based on soliton self-frequency shift is adopted to convert and tune the wavelengths of both dual-comb pulses to ~1650nm. It is shown that this process has introduced little additional intensity noise. The 2ν3 absorption band of methane from 1647 nm to 1663nm is measured with very good agreement with HITRAN, and the standard deviation of the residual is < ~0.006 after averaging ~1.96 seconds of data. Our results further elucidate the potential of dual-comb spectroscopy using one laser, and could pave the way for the development of low-cost, power-efficient, and compact dual-comb instrument targeting more spectral regions.