This paper, for the first time, proposes a novel stochastic model-based eye-diagram estimation method for 8B/10B and transition-minimized differential signaling (TMDS)-encoded high-speed channels. A stochastic model describes a behavior of an encoder with respect to probability. The previous eye-diagram estimation methods are based on an assumption that each bit has the same probability for 1 s and 0 s. However, the assumption limits to estimate an accurate eye-diagram for encoded high-speed channels. We first propose and apply the stochastic model for two types of 8B/10B encodings: 8B/10B and TMDS. For verification, we design the 8B/10B and TMDS encoder within MATLAB. The transient simulation for the 8B/10B encoded channels requires 9700 and 6600 s, respectively. However, the proposed method only requires 23 s in both cases. Furthermore, in the bit-error rate, the transient simulation provides the bathtub curve up to ${10^{ - 2}}$ due to processing time and computing resources. In contrast, the proposed method with the stochastic model provides the bathtub curve up to ${10^{ - 8}}$. In conclusion, this paper successfully proposes and verifies the stochastic model-based eye-diagram estimation method for 8B/10B-encoded high-speed channels.

A method of moment (MoM)-based current reconstruction method is proposed to estimate the surface current density on the ground plane. Current continuity property is automatically enforced with Rao-Wilton-Glisson basis function. Both the least square method and the optimization method are utilized to solve the inverse problem and obtain the ground current. The proposed optimization method is successfully validated with numeric simulations and also a real-world measurement example. The reconstructed current distribution on the ground plane is further used in a typical radio frequency interference (RFI) example to perform RFI estimation and provide guidelines for RFI design. The proposed MoM-based ground current reconstruction method can be valuable to estimate and debug RFI issues in early design stage.

This paper, for the first time, proposes and verifies a new coaxial silicone rubber socket for high-bandwidth and high-density package test using a fabricated sample. In addition, this paper also characterizes and verifies the coaxial silicone rubber socket. Because of the proposed coaxial socket's novel coaxial structure, the proposed socket successfully achieves the electrical performance improvement. For verification, we compare the proposed socket and the previous noncoaxial socket in time domain. The proposed socket has greater eye height and eye width in the measured eye diagram than those of the noncoaxial socket. Moreover, the slope in the eye diagram is also improved in the case of the proposed socket. Therefore, the measured eye diagram for the coaxial socket shows the improvement in electrical performances. This paper also characterizes the equivalent RLGC model for the coaxial silicone rubber socket. In order to verify the RLGC model, we compare the insertion losses and eye diagrams from measurement, 3-D electromagnetic simulation, and the proposed RLGC model, respectively. Their insertion losses are comparable up to 20 GHz. Furthermore, the obtained eye diagrams are almost identical at the data rate of 9.6 Gb/s. In conclusion, this paper successfully proposes, verifies, and characterizes a new coaxial silicone rubber socket for the first time.

For high-speed communication services such as 5G technology, the use of millimeter-wave (mmWave) components substantially increases in mobile applications. The interconnect based on a substrate-integrated waveguide (SIW) is an efficient solution for connecting these devices. However, the SIW characteristics in the mmWave frequency range are not sufficiently presented from the practical viewpoint. In this paper, the experimental characterization of mmWave SIWs in flexible printed circuit boards (FPCBs) and their simulation results are presented. A practical method using balanced/single slot transition is proposed for microstrip-to-SIW transition. Using a full-wave simulation and genetic algorithm, the proposed slot technique is optimized. It is experimentally demonstrated that the cutoff frequency affects the operating band of the SIW differently. The per-unit-length losses of the full-mode and half-mode SIWs are obtained as 0.0375 dB/mm and 0.0609 dB/mm, respectively. Using the measurements, the SIW type effect on the transmission loss is quantitatively analyzed, and the loss is increased up to 62.4% at 39 GHz.

Recently, new form factors, such as foldable, have increased demand for mobile products. Moreover, mobile phones should support the RF signal frequency up to the mm-wave frequency due to the expansion of 5G mobile products. Therefore, 5G foldable products require components that facilitate both mm-wave RF transmission and ultra-high flexibility for interconnecting through the hinge structure of foldable products. To improve flexibility, a flexible PCB must be thin with no ground vias in its bending section; in contrast, the low-loss flexible PCB for mm-wave transmission must be thick and have many ground vias, so there is a trade-off relationship between flexibility and RF characteristics. This paper proposes a new flexible PCB structure that does not experience problems regarding signal transmission to the mm-wave band, even when folded 200,000 times. To overcome the physical limits of the trade-off relationship, an interlayer air-gap was formed; a structure with a via-less and meander ground shape is proposed. The simulated loss of the proposed structure was 0.0254 dB/mm @ 10 GHz, and the isolation between signals ranged from 21.98 dB to 10 GHz. The simulated results of insertion loss and isolation were experimentally verified. The proposed structure is currently being applied to the RF flexible PCB that interconnects through the hinge of a foldable phone, and is currently being mass-produced.

An on-die oscilloscope circuit is proposed to monitor the power noise waveforms inside IC due to the transient stress events for a more complete analysis of the effects of the transient stress events on the electronic systems. When the transient stress event occurs, the induced noise voltage waveform in the power supply is sampled and converted to digital data in real time. A trigger signal created by the event detector circuit is used to hold the digital data. The stored digital data inside the on-die oscilloscope are reconstructed back to the analog noise waveform based on the sampling process. The operation of each circuit block in the on-die oscilloscope is analyzed and validated by simulation and measurement results. The approximate bandwidth of the proposed on-die oscilloscope is extracted from simulation results. The power noise waveforms due to the transmission line pulse events and electrostatic discharge events are measured with an external oscilloscope instrument using cables and directly sampled and reconstructed by the on-die oscilloscope, and these measured and reconstructed analog noise waveforms are compared with each other.