AlGaN/GaN HEMT TRAP CHARACTERISTIC FREQUENCY DEPENDENCE ON TEMPERATURE AND ITS IMPACT ON THE RF POWER AMPLIFIER LINEARIZABILITY

This paper presents a study of the linearizability of AlGaN/GaN HEMT based RF power amplifiers, RFPAs, and its relation with the active device trap activation energy. Based on the theory of thermally activated traps and on the experimental determination of the trap activation energy, we could show that despite different devices may exhibit traps with the same emission timeconstant at room temperature, their characteristic frequency may change significantly under nominal operation because of their temperature rise. And this was found to be key to explain the distinct linearizability performance of the tested devices because different stimulus dynamics excite the long-term memory effects imposed by traps with sensible different levels.

Analysis and design of the biasing network for 1 GHz bandwidth RF power amplifier

The bandwidth of the wireless communication has increased due to the various applications of the wireless devices. A radio frequency power amplifier (RFPA) is one of the crucial components of the transceiver. So, to meet the requirement of the bandwidth, wideband RFPA is needed. The RFPA not only requires a wideband matching network but importantly the biasing network. For the next-generation communication system, a wideband biasing network is needed to operate in the wide GHz bandwidth range. In this paper, a wideband biasing network for the power amplifier is designed using a quarter-wave transmission line and a butterfly stub for the frequency band of 3.3 GHz to 4.3 GHz. Roger’s RO3006 is used as the substrate for the design of the biasing network. The designed network performed well in the required frequency range. The performances of the biasing network have shown 9 dB to 19 dB return loss, the radio frequency (RF) isolation has more than 35 dB, and 0 dB to 1.5 dB insertion loss. This wideband biasing network can be used for the next generation communication system.

Characterization of RF Power Amplifier for Narrow and Wide Band Memory Polynomial Implementations

Linearly efficient RF power amplifiers have a tremendous role in wireless communication and radar systems as they lie at the front end of most RF systems. In today’s world of wireless communication, it is not an easy task to design a RF power amplifier that is linearly efficient. There are two main key challenges that one face for making RF power amplifier’s behavior linearly efficient. First is to characterize RF power amplifier’s coefficients smartly. Second is to propose an approach that works on input signal and make its behavior inverse to that of the designed amplifier behavior so that overall response of the system becomes linear. For countering first challenge, most advanced universally accepted algorithms like Memory Polynomial, Generalized Hammerstein, Cross-term Memory Polynomial and Cross-term Hammerstein are implemented to design RF power amplifier models. For countering second challenge, latest DPD algorithms are implemented which make net response of a system linear. The memory models for modelling RF power amplifier are categorized for narrowband and wideband applications. The narrowband power amplifier models include Memory Polynomial and Cross-term Memory Polynomial models whereas wideband power amplifier models include Generalized Hammerstein and Cross-term Hammerstein models. In this paper, various performance indicators like Standard Deviation (SD), Third Order Intercept (TOI), Intermodulation Distortion Products (IMD3), Modulation Error Ratio (MER), Spurious Free Dynamic Range (SFDR) and Error Vector Magnitude (EVM) are used to characterize RF power amplifier for both narrow and wide band applications. The simulation results show that under narrowband applications, Cross-term Memory Polynomial model works best as it has least standard deviation and is also satisfying other performance parameters up to appreciable level with and without DPD algorithm implementation. While for wideband applications, Cross-term Hammerstein model satisfies the performance measuring parameters excellently.

The Evolution of Manufacturing Technology for GaN Electronic Devices

GaN has been widely used to develop devices for high-power and high-frequency applications owing to its higher breakdown voltage and high electron saturation velocity. The GaN HEMT radio frequency (RF) power amplifier is the first commercialized product which is fabricated using the conventional Au-based III–V device manufacturing process. In recent years, owing to the increased applications in power electronics, and expanded applications in RF and millimeter-wave (mmW) power amplifiers for 5G mobile communications, the development of high-volume production techniques derived from CMOS technology for GaN electronic devices has become highly demanded. In this article, we will review the history and principles of each unit process for conventional HEMT technology with Au-based metallization schemes, including epitaxy, ohmic contact, and Schottky metal gate technology. The evolution and status of CMOS-compatible Au-less process technology will then be described and discussed. In particular, novel process techniques such as regrown ohmic layers and metal–insulator–semiconductor (MIS) gates are illustrated. New enhancement-mode device technology based on the p-GaN gate is also reviewed. The vertical GaN device is a new direction of development for devices used in high-power applications, and we will also highlight the key features of such kind of device technology.

Theoretical and Experimental Investigation Into Machining Characteristics of VHF Micro-EDM

To further explore the machining characteristics of very high-frequency micro-electrical discharge machining (VHF micro-EDM), the range of radio-frequency (RF) power amplifier was expanded to 110 MHz, and the power of the RF power amplifier was also greatly increased up to 91 W. The principle of the VHF pulse generator was discussed in detail, and an electro-thermal model suitable for VHF micro-EDM was established to determine the diameter of the plasma channel and the energy distribution ratio. Experimental studies for VHF micro-EDM were also carried out, and the effects of power and frequency on machining characteristics were then analysed and discussed. The results show that at the same frequency, the higher the power is, the higher the material removal rate (MRR) and the larger the number of discharge craters. At the same power, the MRR and the size of discharge craters both first increase and then decrease with increasing frequency and reach the maximum value at 65 MHz. For the copper workpiece, when the frequency is 110 MHz and the total power of the power amplifier is 8.0 W, 5.6% of the energy is used for the material removal of the workpiece, and the finest processing surface is obtained with the surface roughness Ra=12 nm. The average diameter of the discharge craters is as small as 0.268 μm, and the diameter of the plasma channel is only 0.350 μm. In addition, the effects of different workpiece materials and dielectric fluids are also analysed in this paper.