Electro-magnetic Crosstalk Effects in a Millimeter-wave MMIC Stacked Cell

This work discusses the design of a 2-stacked cell at 36 GHz, analyzing the large discrepancies found between circuit-level and electro-magnetic (EM) simulations due to crosstalk (gate power leakage). At millimeter-wave frequencies, EM optimization of the inter-stage matching is crucial, however, its layout compactness poses several issues on the selection of the EM set-up, thus simulations reliability was put in doubt. To dispel this doubt the cell was fabricated and tested, demonstrating the effectiveness of EM predictions and the actual presence of gate power leakage. This required a deep re-design of the cell, currently on-going, based on a completely different inter-stage matching approach

Electro-magnetic Crosstalk Effects in a Millimeter-wave MMIC Stacked Cell

This work discusses the design of a 2-stacked cell at 36 GHz, analyzing the large discrepancies found between circuit-level and electro-magnetic (EM) simulations due to crosstalk (gate power leakage). At millimeter-wave frequencies, EM optimization of the inter-stage matching is crucial, however, its layout compactness poses several issues on the selection of the EM set-up, thus simulations reliability was put in doubt. To dispel this doubt the cell was fabricated and tested, demonstrating the effectiveness of EM predictions and the actual presence of gate power leakage. This required a deep re-design of the cell, currently on-going, based on a completely different inter-stage matching approach

A Balanced Stacked GaN MMIC Power Amplifier for 26-GHz 5G applications

This work reports the design and experimental characterization of a 4 W Ka-band MMIC power amplifier in GaN/SiC technology, featuring a balanced stacked architecture. The proposed amplifier is composed of a pair of 2-stage amplifier branches, each including a single-transistor driver stage and a 2-stacked-transistor power stage. Small-signal characterization exhibits very good agreement between measurements and simulations, while system-level characterization, employing a 50 MHz instantaneous bandwidth, 10 dB PAPR 5G FR2 signal, demonstrates the very promising linearity performance of the proposed amplifier. The measured minimum ACPR is better than -27 dBc up to an average output power of 24 dBm, from 25 GHz to 27 GHz

High efficiency power amplifiers for modern mobile communications: The load-modulation approach

Modern mobile communication signals require power amplifiers able to maintain very high efficiency in a wide range of output power levels, which is a major issue for classical power amplifier architectures. Following the load-modulation approach, efficiency enhancement is achieved by dynamically changing the amplifier load impedance as a function of the input power. In this paper, a review of the widely-adopted Doherty power amplifier and of the other load-modulation efficiency enhancement techniques is presented. The main theoretical aspects behind each method are introduced, and the most relevant practical implementations available in recent literature are reported and discussed

3.1-3.6 GHz 22 W GaN Doherty Power Amplifier

This paper presents a Doherty power amplifier working from 3.1 GHz to 3.6 GHz. It adopts 10 W packaged GaN HEMTs from Cree/Wolfspeed and achieves a saturated output power in excess of 43.4 dBm. Saturated efficiency ranges from 57.7 % to 75.2 %, while efficiency at 6 dB back-off is between 44.2 % and 59.8 %. System-level simulations at 3.5 GHz adopting a 16QAM signal with 5 MHz bandwidth and 4 dB peak to average power ratio showed an adjacent channel power ratio of -28 dBc/Hz without pre-distortion, at an average output power of 43 dBm and with an average efficiency of 71 %

Penile revascularization using the descending branch of the lateral circumflex femoral artery: An alternative vascular graft

Introduction and relevance: Microsurgical revascularization stands as the preferred method for addressing erectile dysfunction (ED) resulting from traumatic penile arterial insufficiency. Traditional microarterial bypass surgery (MABS) techniques have typically relied on utilizing the inferior epigastric artery (IEA) as the graft vessel. However, issues such as endothelial dysfunction in the vessel and alterations in abdominal tissue can negatively impact surgical outcomes. MABS using the descending branch of the lateral circumflex artery of the femur (DLCFA) should be proposed as a surgical option for penile arterial revascularization. Case presentation: A 29-year-old who experienced ED after a pelvic bone fracture with hypogastric vascular injury was referred to our center. Preoperatory penile Doppler ultrasound (PDU) examination documented the presence of arterial insufficiency. Selective hypogastric angiography pointed out the interruption of arterial blood flow at the level of the distal right internal pudendal artery. Case discussion: Access to the dorsal penile artery was gained through an infrapubic incision, the DLCFA pedicle was isolated through an incision along the anterolateral right thigh. After its transposition, the arterial bundle was anastomosed to the dorsal penile artery in an end-to-end fashion. Intraoperative PDU has been used to verify the patency of the anastomosis. At 6 months follow-up, optimal flow parameters on PDU were persistently registered, and the patient had consistent clinical improvement on the IIEF-5 score. Conclusion: DLCFA grafting for penile revascularization is a suitable therapeutic option in traumatic ED due to its size and accessibility. Further experience is necessary to compare clinical outcomes among different revascularization techniques

Design strategy of a 2.8–3.6 GHz 20W GaN Doherty power amplifier

This paper presents the design of a 20W GaN Doherty Power Amplifier working in the range 2.8 GHz–3.6 GHz. The design strategy adopted for the design of the Doherty output combiner is discussed, which consists in embedding the device parasitics into the latter, implemented as a multi-stage quarter-wavelength transformer, in order to achieve wideband behaviour. The saturated output power ranges from 42dBm to 44 dBm, with a corresponding drain efficiency in excess of 47%. The efficiency at 6 dB of output back-off is higher than 42% over the whole frequency band, and the small-signal gain is higher than 10 dB. Due to the discrepancies of the measured scattering parameters compared to the simulated ones, which could not be corrected with post-tuning, a redesign of the prototype is ongoing

Arterial Pressure Management in a Reconstructive Microsurgery Patients by Dopamine Infusion in a Nonintensive Care Ward

Free flap perfusion and arterial pressure management have always had a crucial role in free flap reconstruction. Blood pressure values requested can be reached either by using vasoactive agents or fluid replacement or the combination of both.1,2 In contrast to the most frequently tested phenylephrine, norepinephrine, and dobutamine,3,4 this work evaluates dopamine efficacy in perioperative blood pressure management. In our institution, dopamine infusion is the only vasoactive agent authorized in a non-intensive care unit department. This drug stimulates \u3b1- and \u3b2-adrenergic receptors with positive chronotropic and inotropic effects and reduces peripheral vascular resistance helping in this way to achieve an increase of blood pressure and free flap perfusion.

A 3-3.8 GHz Class-J GaN HEMT Power Amplifier

This paper presents a wideband class J power amplifier (PA) based on a packaged 10 W GaN HEMT device covering the 3 GHz to 3.8 GHz frequency range. A good trade-off between efficiency and gain has been pursued in synthesizing the second harmonic output termination. The achieved output power is in excess of 41 dBm with drain efficiency ranging from 59 % to 65.5 % and a small signal gain above 14 dB. Preliminary large signal measurements at 3.3 GHz confirm the proper behavior of the PA

Broadband Class-J GaN Doherty Power Amplifier

This paper presents a broadband 3 GHz–3.7GHz class-J Doherty power amplifier exploiting second harmonic tuning in the output network. Furthermore, the output impedance inverter is eliminated and its effect is embedded in the main device’s output matching network, thus trading off among bandwidth, efficiency, and gain. The proposed amplifier adopts two 10W packaged GaN transistors, and it achieves in measurement 60–74%, and 46–50% drain efficiency at saturation and 6 dB output back-off, respectively, with a saturated output power of 43 dBm–44.2dBm and a small-signal gain of 10 dB–13 dB. The proposed DPA exhibits a simulated adjacent channel power ratio less than 30 dBc at 36dBm average output power when a 16-QAM modulation with 5 MHz bandwidth is applied to the 3.5 GHz carrier