AREA/POWER-EFFICIENT POWER AMPLIFIERS FOR MM-WAVE 5G AND TRUE-TIME DELAY BASED MM-WAVE BEAMFORMING TRANSCEIVERS

Mohammad Ali Mokri

doi:10.7273/000007208

The global mobile network data traffic has reached 145EB(145 × 1018B) per month in the first quarter of 2024 and compared to the first quarter of 2023 there is a 25% increase[1]. The 5th generation mobile communication standard is the current solution to this huge demand for larger and faster wireless networks. The deployment of the 5G network is still ongoing and its subscriptions are expected to reach 5.6 billion by 2029 [1]. This huge amount of data transfer coupled with its rapid growth is the driving force for innovations and advancements in the wireless communication field. There are many new challenges at every level of the network stack, from the physical layer to the application layer and from software to hardware implementation. The frequency range of mm-wave 5G communication includes several bands (N257-261) within the FR2 spectrum. Specifically, N257, N258, and N261 cover 24.25 GHz to 29.5 GHz, while N260 and N258 span 37 to 40 GHz. Carriers may use one or more of these bands, requiring user equipment (UE) to support both lower and higher frequency bands for flexibility. However, designing transceivers to cover such a wide range (24.25 to 40 GHz) is challenging, leading to trade-offs in performance or the need for multiple transceivers and antennas, which increases the device's footprint. The first design presents a dual-band PA for lower and higher frequency bands of 5G FR2 based on the proposed Dual-path transformer. The proposed PA prototype is fabricated in a 65 nm CMOS process achieving 15.3 and 14.0 dBm of saturated output power in 28 and 39 GHz. Integrated silicon phased-array transceivers are crucial for mm-wave 5G and future 6G beamforming applications due to their compact size and enhanced functionality. These transceivers, which can have up to 256 elements in base stations or 4-8 elements in mobile devices, rely heavily on the performance and size of Power Amplifiers (PAs). The efficiency and linearity of PAs, especially at peak and back-off power regions, are vital for the overall system performance. However, most existing designs use simple class-AB PAs, which are not optimized for back-off efficiency. The second design presents a back-off efficient PA for mm-wave 5G and upcoming 6G beamforming phased array transceivers (PATs). A compact back-off efficient Doherty PA (DPA) with a common base structure as the core of the PA and small low-loss passive elements is proposed. The proposed architecture moves the role of the input hybrid coupler to the interstage matching network while maintaining DPA functionality. It achieves a peak gain of 20.4 dB at 28.45 GHz with a 1 dB bandwidth of 4.45 GHz. Under large-signal conditions, it archives >19.5dBm Psat with >36 % P AEsat. To mitigate the significant propagation loss at millimeter-wave frequencies, a large number of antenna elements is required, which complicates the initial access phase of beamforming systems. The large number of antennas makes beam training which is part of the initial access phase, challenging and time-consuming for conventional phased array systems. Recently, a true-time-delay (TTD) array-based beam training algorithm has been shown as an effective solution to overcome the training overhead in large arrays. In the third work, we present a custom-built over-the-air (OTA) testbed to study the effects of hardware impairments on the TTD-based beam training and verify its feasibility in a real system. Post-processing results showed that with the nonideality effects properly handled, the 3D TTD beam training algorithm can achieve high Angle Of Arrival (AOA) estimation accuracy. The proposed mm-wave testbed with some modifications is used for modulated signal measurement characterization of mm-wave PAs under modulated signal waveform.

AREA/POWER-EFFICIENT POWER AMPLIFIERS FOR MM-WAVE 5G AND TRUE-TIME DELAY BASED MM-WAVE BEAMFORMING TRANSCEIVERS

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