Broadband Performance Assessment of an RF Power Transistor Employing the Real Frequency Technique

selected active device is essential to design an RF power amplifier for optimum gain and power added efficiency. As they are obtained, these impedances may not be realizable network functions over the desired frequency band to yield the input and the output matching networks for the amplifier. Therefore, in this paper, first, we introduce a new method to test if a given impedance is realizable. Then, a novel “Real Frequency Line Segment Technique” based numerical procedure is introduced to assess the gain-bandwidth limitations of the given source and load impedances, which in turn results in the ultimate RF-power intake/ delivering performance of the amplifier. During the numerical performance assessments process, a robust tool called “Virtual Gain Optimization” is presented. Finally, a new definition called “Power-Performance-Product” is introduced to measure the quality of an active device. Examples are presented to test the realizability of the given source/load pull data and to assess the gain-bandwidth limitations of the given source/load pull impedances for a 45W-GaN power transistor, namely “Cree CG2H40045”, over 0.8 -3.8 GHz bandwidth.

Broadband Performance Assessment of an RF Power Transistor Employing the Real Frequency Technique

selected active device is essential to design an RF power amplifier for optimum gain and power added efficiency. As they are obtained, these impedances may not be realizable network functions over the desired frequency band to yield the input and the output matching networks for the amplifier. Therefore, in this paper, first, we introduce a new method to test if a given impedance is realizable. Then, a novel “Real Frequency Line Segment Technique” based numerical procedure is introduced to assess the gain-bandwidth limitations of the given source and load impedances, which in turn results in the ultimate RF-power intake/ delivering performance of the amplifier. During the numerical performance assessments process, a robust tool called “Virtual Gain Optimization” is presented. Finally, a new definition called “Power-Performance-Product” is introduced to measure the quality of an active device. Examples are presented to test the realizability of the given source/load pull data and to assess the gain-bandwidth limitations of the given source/load pull impedances for a 45W-GaN power transistor, namely “Cree CG2H40045”, over 0.8 -3.8 GHz bandwidth.

Muscle Activation and Torso Movement during Exercise using Novel Fiberglass Resistance Poles

Background: A novel form of functional training utilizes flexible fiberglass poles for resistance. Similar to elastic bands, as the poles flex, resistance increases. To date, no studies have examined activation patterns associated with such implements. Objective: This study examined muscle activation and torso rotation using different pole resistance intensities during a “push-pull” rotational core exercise. Methods: Twenty-one subjects (16 women, 5 men; age=20.4±1.3y) completed 6 trials of 10 repetitions each of a standing push and pull movement with 3 different pole tensions (very light, light, moderate). Muscle activation (electromyography) for the anterior and posterior deltoid, abdominal oblique, and paraspinal muscles were recorded. Concentric contractions during the push phase (PUSH) and the pull load (PULL) phases were recoded, and percent maximal voluntary contraction (%MVC) was computed. Markers on the acromion process and a vertically mounted camera were used to record torso rotation during each push and pull. ANOVA for each muscle and PUSH and PULL was used for comparisons across pole intensity. Results: Significant main effects for torso rotation were seen, with rotation with the very light pole (Push= 61.9 ± 9.20, Pull= 64.8 ± 14.00) significantly greater than moderate (Push= 52.0 ± 12.80, Pull= 54.9 ± 10.10). EMG data were highly variable, with no differences in muscle activation detected across pole resistance loads. Conclusion: Variability of the EMG data prevent clear resolution of activation patterns. However, torso rotation is limited with heavier pole resistance since increased pole flex also increases resistance.

Asymmetric Doherty Power Amplifier with Input Phase/Power Adjustment and Envelope Tracking

In this paper, the design and implementation of a Doherty power amplifier (DPA) are proposed using gallium nitride high electron mobility transistors (GaN HEMTs). Class-F and Class-C modes are combined to obtain an asymmetric DPA. The precise active load-pull controlling of fundamental and harmonic terminations of the DPA is simulated and analyzed, including the parasitics of the transistors. The measurements of the DPA with the phase difference, input power ratio adjustment, and envelope tracking of the auxiliary PA are discussed in detail in order to achieve a competitive performance. A greater than 63% drain efficiency is obtained within the 10-dB input power dynamic range at 2.1 GHz. The peak of the drain efficiency reaches 73%, with a corresponding output power of 46 dBm.

Source/Load-Pull Noise Measurements at Ka Band

This paper is focused on the extraction of the noise parameters of a linear active device by exploiting both forward and reverse noise power measurements associated with different terminations. In order for load-pull measurements to yield a significant marginal improvement (as compared to forward measurements only) it is expected that the device under test should appreciably deviate from unidirectionality. For this reason, the source/load-pull technique is applied to frequencies at which the considered devices are still usable but their reverse noise factor exhibits a measurable dependence on the output terminations. Details on the test bench set up to the purpose, covering the 20–40 GHz frequency range, are provided. A characterization campaign on a 60 nm gate length, 4×35 µm GaN-on-Si HEMT fabricated by OMMIC is illustrated.