In this paper, we analyze and simulate the performance of RAKE receiver for ultra wide band (UWB) systems in indoor multipath radio channel. Pulse position modulation-time hopping (PPM-TH) signal is considered. And we also consider three types of RAKE receivers, which are ideal RAKE, selective RAKE, and partial RAKE receivers. The indoor channel is modeled as the modified Saleh and Valenzuela (SV) model which has been proposed as a UWB channel model by the IEEE group, IEEE 802.15.SG3a.
Ti3C2Tx MXene was synthesized by HF (45 wt.%) etching of parent Ti3AlC2 MAX phase for 7, 15, and 24 h. Microscopic studies showed that the synthesized MXenes had two-dimensional nanosheet morphology. Furthermore, compositional analyses demonstrated the existence of -F and -OH groups on Ti3C2Tx after etching. After fabrication of gas sensors, NH3 sensing at 25°C and under 1–6 V applied voltages in self-heating condition, revealed that the Ti3C2Tx MXene sensor etched for 24 h exhibited the highest response to NH3 gas under 4 V. Furthermore, it demonstrated good flexibility on PET substrate and even after being bent 5000 times and being tilted 1000 times, its response was almost the same as its fresh state. Notably, its sensing performance at different bending angles (0 to 120°) was acceptable, indicating good flexibility in the bent condition. The results of this research showed the high potential of Ti3C2Tx MXene for NH3 sensing in the self-heating mode with low power consumption.
We studied the effects of Corbino structure amorphous indium‐galium‐zinc oxide (a‐IGZO) thin film transistors (TFTs) using TCAD and circuit simulator. The Corbino structure shows the special behavior with drain electrode in inner or outer. By simulation, we confirm the Corbino structure have better performance than conventional structure for AMOLED pixel circuit.
In this paper, developments of wafer level fan-out (WLFO) technology using organic substrates, ajinomoto build-up film (ABF) with laser ablation process and buried pattern PCB, are introduced for low cost and high electrical performance not only on low frequency ranges but also microwave applications. WLFO technology using organic substrates can enhance routing density and provide smaller form factor than flip-chip chip scale packages (fcCSP). Moreover, short signal routing paths from die out to package out can be realized to improve overall electrical performance in WLFO, In this paper, the process of WLFO using ABF with laser drilling and buried-pattern PCB substrate are explained. In addition, measurements of coplanar waveguide (CPW) structure on WLFO and interconnection models from die I/O pad to balls using 3D EM simulation are conducted to estimate effectiveness in microwave ranges.
Conventional flip chip technologies such as the mass reflow (MR) process and the thermal compression bonding (TCB) process are commonly used technologies in the micro assembly field. However, there is a continuous need for next generation interconnection technology to achieve a low form factor with increasing die and substrate complexities. Moreover, very thin 3D integrated packages and 2.5D packages with thin interposer die promise advanced interconnection technologies for mobile and wearable applications. With this point of view, the most important factor in interconnection is optimal thermal energy control for soldering. However, a conventional MR process cannot provide any selectivity and controlled thermal energy transferring with the traditional convection reflow. Its high thermal budget makes warpage an issue, aside from other side effects. To overcome the MR process problems, recent researches and industries have focused on developing a TCB process with non-conductive paste (NCP) or non-conductive film (NCF) due to TCB's unique advantages of low mechanical and thermal stress. However, the productivity of the TCB process is not comparably to the conventional process. Laser-assisted bonding (LAB) with beam homogenizer is considered to be the next generation interconnection technology due to its excellent thermal selectivity, extremely fast ramping up speed with purely controlled wavelength. This LAB process offers a very stable interconnection quality as well as robust functional and reliability result. Interestingly, it also achieves excellent results with thin coreless substrate due to its selective heating area availability. This paper will discuss the laser heating mechanism, multi-chip & component bonding availability and advantage of LAB from an assembly industrial perspective.
Parametric array transducers are used for highly directional speaker in an air environments. The power amplifiers for them should have sufficient linear output characteristic to amplify high-frequency ultrasonic waves with low THD, and also have high efficiency to avoid system heating and fuel problems. Piezoelectric micromachined ultrasonic transducers for parametric array transducers need DC-biased voltage driving signals in order to get high-directional quality-sound features. The existing power amplifier such as class A amplifiers has low efficiency and require large volume heatsinks. To overcome the above-mentioned disadvantages of the conventional amplifier, this paper proposes a new power amplifier and also its power supply. The proposed power amplifier system ensures high linearity of output characteristic by utilizing the push-pull class B type amplifier, and furthermore gets high efficiency by providing the DC-DC converter-type power supply of energy recovery feature as well as applying the peak envelope tracking technique. Also the paper suggests the detailed circuit topology. Its characteristics are verified by the detailed experimental results.
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