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A Multioutput and Highly Efficient GaN Distributed Power Amplifier for Compact Subarrays in Wideband Phased Array Antennas

Helalian, Hamid | 2023

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 56478 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Atarodi, Mojtab
  7. Abstract:
  8. New applications such as high data rate telecommunications, millimeter-wave imaging systems, positioning systems, wall, and ground-penetrating radars, and vital sign monitoring radars require specifications of heavy-duty systems. In summary, in advanced applications with high bandwidth, having multiple inputs and multiple outputs, phased arrays, and optimal energy efficiency are in demand and desirable. Despite the diverse applications of these radars, commercial products in this field are very rare, expensive, and bulky. Therefore, research work in this area is justified from an applied perspective. Increasing the power amplifier's efficiency results in the creation of a smaller, more reliable, and lower-cost RF transmitter chain. This thesis includes the design and implementation, as well as the first test results of a four-output Distributed Power Amplifier (DPA). Because the wasted power in the standard distributed power amplifier's termination resistor is used, and all forward and reverse waves are delivered to the outputs, the new structure significantly contributes to improving the Power Added Efficiency (PAE) of the DPA. The flexibility and feasible implementation of the distributed power amplifier with multiple outputs (MODPA) substantially reduce the cost and complexity of designing phased array transceivers and ultra-broadband massive antenna arrays. The chip, based on AlN-GaN-AlGaN technology with a gate length of 100 nm, is fabricated on a 3 mm2 silicon substrate using pHEMT technologies and has been tested. This structure is suitable for implementing compact phased array systems. Phased array systems increase the signal-to-noise ratio, provide the ability to control beam position and beam steering in space, make it easier to overcome challenges arising from multi-pathing, and are efficient in sectorized cellular communications. However, the use of multiple antennas in phased array systems improves system performance while increasing design complexity, system size, and manufacturing cost. To leverage the advantages of phased array systems, it is necessary to use methods that mitigate the complexity of these systems. For this purpose, a structure is proposed to reduce the number of phased array elements. The high-power capabilities of GaN technology make it a suitable option for power amplifiers. A small GaN transistor can provide power levels at high frequencies that are not practical in other high-power technologies; therefore, this technology is a suitable choice for implementing high-power broadband distributed power amplifiers with high output power. The proposed structure is based on distributed power amplification. In the proposed structure, in the transmitter, two power amplifier (PA) and power divider blocks are integrated and replaced with a simple block with a wide bandwidth. In the receiver, two low-noise amplifiers (LNA) and a power combiner block are combined, and a structure with a wide bandwidth is provided. The integrations performed in the proposed structure result in system and circuit compression, reducing chip size and power consumption and reducing the overall cost. An optimal design method has been proposed for selecting load and source impedances at the fundamental and harmonic frequencies to maximize the Power Added Efficiency (PAE) in a distributed power amplifier with high efficiency and wide bandwidth.The presented broadband design methodology addresses an ambiguity for picking optimum load/source impedance at a single frequency caused by higher order harmonics of operating frequencies dropping in the band. The results of chip measurements show that this power amplifier has a maximum output power of 37-41 dBm in its four outputs, PAE = 22-73%, maximum power gain of 17-21 dB, and a bandwidth from near DC to 25 GHz. The maximum difference in power among the four output ports is 1.5 dB, making this power amplifier an attractive choice for implementing phased array systems
  9. Keywords:
  10. Class J Power Amplifier ; Distributed Amplifier ; Spatial Power Combining ; High Electron Mobility Field Effect Transistor (HEMT) ; Phased Array Antenna ; GaN Technology ; Wideband Phased Array System

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