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This presents a broadband high-efficiency power amplifier (PA). The branch line coupler is used to design the output circuits of the PA. By appropriately selecting the impedance conditions of terminal ports, the branch line coupler can not only realize impedance conversion but also realize harmonic impedance control. Two-stage couplers are exploited to expand the working bandwidth. To verify the effectiveness of the proposed method, a broadband high-efficiency PA is designed and fabricated by using CGH40010F. Measurements demonstrate that the saturated output power is from 41.0 to 42.5 dBm, the drain efficiency is between 64% and 75%, and the gain is from 10.2 to 11.5 dB.

This letter proposes a novel broadband, high-efficiency power amplifier (PA). The high-efficiency characteristics of Class-EF PAs and the large bandwidth advantages of Class-J PAs are effectively combined in the proposed PA. By theoretically analyzing the impedances of traditional Class-EF PAs and class-J PAs, we can consider the possibility of combining these two types of PAs. The conditions that need to be met are derived. In order to verify the effectiveness of the proposed method, a high-efficiency wideband Class-EFJ PA is designed and fabricated by using CGH40010F GaN HEMT. The measurement results demonstrate that the Class-EFJ PA has saturated output power of 40.5–42.7 dBm in 1.2–3.6 GHz. Drain efficiency of 63%–73% was achieved over the same frequency band. The Adjacent Channel Leakage Ratio (ACLR) was also better than −31.2 dBc at an average output power of 35.6 dBm.

This paper proposes a method that employs novel hybrid continuous class-EFJ power amplifiers (PAs) as carrier PA to design a broadband high-efficiency Doherty power amplifier (DPA). Bandwidth characteristic of the proposed DPA is analyzed in detail. By proper selection of related parameter values, up to 78% fabrication bandwidth can be obtained. Post-harmonic tuning network is applied to improve the bandwidth and enhance the efficiency. Then, a closed design process is presented to design broadband DPA based on derived theories. For validation, a broadband DPA operating in 1.2-2.8 GHz is designed and fabricated. Measurements illustrate that the DPA can deliver saturated output power between 43.7 dBm and 44.1 dBm in 1.2-2.8 GHz, and the saturated drain efficiency from 60.5% to 74.2 % is achieved. Moreover, drain efficiency is 48.1%-57.6% at the 6 dB power back-off. Compared with conventional DPAs, the proposed DPA exhibits superior performance of bandwidth characteristics and power back-off efficiency over a wide bandwidth.

To cover the working frequency bands of the three mobile carriers of China Mobile, China Telecom, and China Unicom, power amplifiers (PAs) are required to own broadband. A PA with bandwidth 1.3–2.7 GHz is designed (fully covers the operating bands of the three mobile carriers). Measured results show that greater than 68% efficiency is attained over a 75% bandwidth from 1.3 to 2.7 GHz. The output power is larger than 40.2 dBm with gain varying from 10 to 13 dB across the band. In this article, three-frequency point matching method is applied in order for broadband matching. High-efficiency is achieved by a specially designed impedance matching topology which realizes short-circuits of the second harmonics and open-circuits of the third harmonics at different frequencies. The designed broadband high-efficiency GaN PA provides a new approach and method for the development of PAs in 4G base stations.

This article presents a novel efficiency‐enhanced Doherty power amplifier (DPA) by using a Chireix‐like compensation technique. This technique introduces a compensation circuit structure at the combiner to offset the phase difference effect of a DPA for enhancing drain efficiency. A DPA based on the proposed structure is fabricated with two 10 W GaN high electron mobility transistor (HEMT) transistors. The fabricated DPA with such proposed compensation structure manifests a measured saturated output power of 43.5 dBm and drain efficiency of 68% to 71% in the frequency range of 3.2 to 3.7 GHz. Forty‐five percent of drain efficiency can be achieved at 6 dB power back‐off. And the adjacent channel leakage ratio (ACLR) is better than −48.6 dBc with digital predistortion.

The design, implementation, and measurements of a high efficiency and high power wideband GaN HEMT power amplifier are presented. Package parasitic effect is reduced significantly by a novel compensation circuit design to improve the accuracy of impedance matching. An improved structure is proposed based on the traditional Class-F structure with all even harmonics and the third harmonic effectively controlled, respectively. Also the stepped-impedance matching method is applied to the third harmonic control network, which has a positive effect on the expansion bandwidth. CGH40025F power transistor is utilized to build the power amplifier working at 0.8 to 2.7 GHz, with the measured saturated output power 20–50 W, drain efficiency 52%–76%, and gain level above 10 dB. The second and the third harmonic suppression levels are maintained at −16 to −36 dBc and −16 to −33 dBc, respectively. The simulation and the measurement results of the proposed power amplifier show good consistency.

In this work, a tunneling magnetic flux controlled memristor emulator is presented. It imitates the behavior of the memristor with off-the-shelf solid state components. Two current conveyors, a multiplier, an IC with four operational amplifiers and several lumped-components are employed in the emulator. The two terminals of the emulator is float. The measured results with periodic unbalance input voltage are consistent with the SPICE simulation ones. The emulator provides an alternative solution of memristor model in real circuit applications.

Magnetic mesoscopic and nano-sized structures have promising applications such as high-density data storage, magnetic field sensors, and microwave devices. Patterned magnetic structures are especially interesting because their constitutive material, sizes and geometry are easily adjustable in fabrication. This makes manipulation of electromagnetic properties possible and creates many novel features never discovered in conventional bulk materials. The artificial magnetic structures that can be engineered to meet specific application purposes are called magnetic metamaterials. This thesis aims to investigate magnetic materials nanostructured to produce high permeability and low loss performance at gigahertz (GHz) frequency region. Such property is highly desired for communication devices with miniaturized size, reduced energy consumption and enhanced signal detection sensitivity. Antennas, microwave field sensors are the examples of applications. We first analyze the single domain model for ac magnetization to get theoretical understanding and prediction. Then we evaluate all free energy terms for a magnetic dipole to know which energies (or fields) are contributing to the effective magnetic field in our real experiments. Secondly experiment work including fabrication, dc characterization and ac characterization of Permalloy and cobalt nanoscale magnetic structures, as well as FePt nanoparticles are covered. Different microwave techniques regarding sensitive magnetic permeability measurements are discussed in detail for comparison. In the last chapter, micromagnetic simulations are performed to obtain broadband ac magnetization response spectrum for a single Permalloy nanowire and two interacting Permalloy nanowires.