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To fulfill the insatiable demand for high data-rates, the millimeter-wave (mmW) 5G communication standard will extensively use high-order complex-modulation schemes (e.g., QAM) with high peak-to-average power ratios (PAPRs) and large RF bandwidths. High-efficiency integrated CMOS power amplifiers (PA) are highly desirable for portable devices for improved battery life, reduced form factor, and low cost. To meet simultaneous requirements for high efficiency and reasonable linearity, PAs intended for use with complex modulation are often operated in Class-AB mode [1,2]. For small input amplitude in Class-AB, the device is turned-on and has an input capacitance (Cgs) of ~(2/3)WLCox. As the input amplitude becomes large, the device turns-off for part of the RF cycle, thus reducing its effective input capacitance. This input capacitance-modulation effect creates an input-amplitude-dependent phase shift in Class-AB mode resulting in an amplitude-modulation to phase-modulation (AM-PM) distortion [2]. Consequently, it degrades linearity metrics (e.g., error vector magnitude (EVM), adjacent channel power ratio (ACPR)) in complex-modulation systems. External linearization techniques (e.g., digital pre-distortion) are often used in transmitters to meet linearity requirements, but they are complex in nature and expensive to implement. Apart from these, few works at low-GHz frequencies are reported to improve the PA's intrinsic linearity using a varactor-or PMOS-based AM-PM correction methods [1,2]. These works reduce the design overhead of external linearization systems; however, the inclusion of additional capacitive element to correct AM-PM degrades gain and efficiency, which is not optimal for mmW frequencies
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Adjustable Power Modulation For A Leg Mechanism Suitable For Running
Recent work in the design of mechanical systems for terrestrial locomotion has indicated successful strategies for increasing the energetic performance of a robotic locomotor without upgrading its actuator system. We apply one such strategy, termed power modulation, in a new way: for the design of a leg mechanism useful for running. Power modulation geometrically defines force/torque ratios between robot components to mechanically achieve certain energy transmission characteristics during fast stance dynamics that increase the kinetic power output of the overall system. Furthermore, we investigate the design of a leg mechanism that can adjust to exhibit power modulation. In this way, a leg mechanism would exhibit a low power mode for flat terrain, and can adjust to a high power mode for rough terrain. The latter makes jumping possible and extends the range of available footholds that can be accessed in a single step. To find a suitable leg mechanism, we leverage the Finite Root Generation method to compute a design. The design is advanced to a prototype and basic experiments are conducted to investigate its behavior as adjusted between high-and low-power modes
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- Award ID(s):
- 1636302
- PAR ID:
- 10110013
- Date Published:
- Journal Name:
- IEEE ICRA
- Page Range / eLocation ID:
- 9137 to 9142
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/ICRA.2019.8794379
