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400 GHz HBT Differential Amplifier Using Unbalanced Feed Networks
Hacker, J.,Urteaga, M.,Lin, R.,Skalare, A.,Mehdi, I.,Rieh, J.-S,Kim, M. IEEE 2012 IEEE microwave and wireless components letters Vol.22 No.10
<P>A terahertz differential eight-stage amplifier fabricated using state-of-the-art 125 nm double-heterojunction bipolar transistors (DHBT) is presented. The four-port unit-cell chain is designed for optimum forward differential gain with no even and odd-mode reverse gains. Unbalanced single-ended feed networks are added to preserve the amplifier gain without inducing oscillations. The proposed feed scheme is validated by a stable amplifier operation in 325-to-450 GHz range with the peak gain of 22 dB at 375 GHz.</P>
A Fully-Integrated 40–222 GHz InP HBT Distributed Amplifier
Sangwoo Yoon,Lee, Iljin,Urteaga, Miguel,Kim, Moonil,Sanggeun Jeon IEEE 2014 IEEE microwave and wireless components letters Vol.24 No.7
<P>This letter presents an ultra-wideband distributed amplifier (DA) implemented in a 250 nm InP HBT technology. Four cascode gain cells are distributed along the input and output microstrip lines to achieve wideband operation. Each cascode cell employs inductive peaking at the output to further enhance the bandwidth and to align the phase delay between the input and output lines. All dc bias components are fully integrated on-chip. The DA exhibits a measured gain of 10 dB with a 3 dB bandwidth extending from 40 to 222 GHz. The maximum output power was measured to be 6.0, 9.2, and 8.5 dBm at 60, 77, and 134 GHz, respectively, which allows the DA to also be used as a medium-power amplifier. To the authors' best knowledge, the DA achieves the highest 3 dB bandwidth of 182 GHz reported thus far, while showing low dc power consumption (105 mW) compared to other state-of-the-art DAs.</P>
A 275 GHz Active Vector-Sum Phase Shifter
Quan, C.,Heo, S.,Urteaga, M.,Kim, M. THE INSTITUTE OF ELECTRICAL ENGINEERS 2015 IEEE Microwave and Wireless Components Letters Vol. No.
<P>Terahertz vector-sum phase shifters capable of 360<SUP>°</SUP> phase control over the frequency range of 240 to 310 GHz are presented. Because the impedance mismatch of the variable-gain amplifiers employed in the phase shifter determines the flatness of the offset phases, a new broadband VGA design with its input and output impedances unaffected by dc bias is introduced. The measured results on the phase shifter fabricated using 0.25 μm InP HBT technology show incremental phase shifts of 45<SUP>°</SUP> with an average RMS offset phase error of 3.6<SUP>°</SUP> and insertion loss of -1 to -13 dB for eight basis dc bias states.</P>
600 GHz InP HBT frequency multiplier
Choi, S. H.,Urteaga, M.,Kim, M. IET 2015 Electronics letters Vol.51 No.23
<P>A 600 GHz monolithic frequency multiplier circuit fabricated using 0.25 μm InP HBT (heterojunction bipolar technology) technology is reported. The multiplier uses two 6 μm finger devices in common-base push-push configuration to obtain extremely simple matching networks. Measurements using on-wafer RF probes indicate maximum output power of -8.3 dBm at 590 GHz with a wide operation bandwidth of better than 50 GHz.</P>
H-Band Power Amplifier Integrated Circuits Using 250-nm InP HBT Technology
Jungsik Kim,Sanggeun Jeon,Moonil Kim,Urteaga, Miguel,Jinho Jeong IEEE 2015 IEEE transactions on terahertz science and technol Vol.5 No.2
<P>In this paper, H-band (220-325 GHz) power amplifier (PA) integrated circuits (ICs) are presented using 250-nm InP HBT technology, where a cascode topology was adopted to achieve high gain and high output power. Three PAs were designed: PA1 was implemented with two-stage cascode HBTs, PA2 combined two PA1s, and PA3 combined four PA1s, by using Wilkinson couplers without isolation resistors. Electromagnetic simulations were carried out for the accurate design of passive circuits such as a microstrip line, a capacitor, and RF pads. The measured insertion loss of the RF pad and Wilkinson coupler was as low as 0.24 dB and 0.70 dB, respectively, at 300 GHz. The three PAs exhibited a measured gain higher than 15 dB with good return losses at 300 GHz. The output powers scaled well with total emitter area of the PAs. PA3 exhibited a maximum output power of 13.5 dBm at 301 GHz. To the best of the authors' knowledge, this corresponds to the highest output power among the previously reported solid-state PAs in this frequency range.</P>
Younghwan Kim,Sooyeon Kim,Iljin Lee,Urteaga, Miguel,Sanggeun Jeon Professional Technical Group on Microwace Theory a 2015 IEEE Transactions on Microwave Theory and Techniqu Vol. No.
<P>This paper presents a wideband vector-sum phase shifter (VSPS) that operates over the entire WR-3 band (220-320 GHz). Compared to conventional VSPSs with double Gilbert cells, the proposed phase shifter employs a single Gilbert-cell structure for vector modulation. This reduces the output current combining ratio from 8:2 to 4:2, and boosts the impedance at the combining node, thus facilitating wideband output matching at upper millimeter-wave and terahertz bands. The simplified structure leads to a reduction in dc power consumption and chip area without sacrificing the 360 <SUP>°</SUP> phase-shifting property. Lossy matching is applied at the Gilbert-cell output to further increase bandwidth and stability at the expense of relatively high loss. The phase shifter is implemented using a 250-nm InP DHBT technology that provides f T and f max exceeding 370 and 650 GHz, respectively. The measurements exhibit a wideband phase shift with continuous 360 <SUP>°</SUP> coverage and average insertion loss ranging from 11.8 to 15.6 dB for the entire WR-3 band. The root mean square amplitude and phase error among different phase states are less than 1.2 dB and 10.2 <SUP>°</SUP>, respectively. The input-referred 1-dB compression is measured at 0.7 dBm on average. The dc power consumption is 21.8-42.0 mW at different phase states.</P>
Cushing disease in pediatrics: an update
Concepción-Zavaleta Marcio José,Armas Cristian David,Quiroz-Aldave Juan Eduardo,García-Villasante Eilhart Jorge,Gariza-Solano Ana Cecilia,Durand-Vásquez María del Carmen,Concepción-Urteaga Luis Albert 대한소아내분비학회 2023 Annals of Pediatirc Endocrinology & Metabolism Vol.28 No.2
Cushing disease (CD) is the main cause of endogenous Cushing syndrome (CS) and is produced by an adrenocorticotropic hormone (ACTH)-producing pituitary adenoma. Its relevance in pediatrics is due to the retardation of both growth and developmental processes because of hypercortisolism. In childhood, the main features of CS are facial changes, rapid or exaggerated weight gain, hirsutism, virilization, and acne. Endogenous hypercortisolism should be established after exogenous CS has been ruled out based on 24-hour urinary free cortisol, midnight serum or salivary cortisol, and dexamethasone suppression test; after that, ACTH dependence should be established. The diagnosis should be confirmed by pathology. The goal of treatment is to normalize cortisol level and reverse the signs and symptoms. Treatment options include surgery, medication, radiotherapy, or combined therapy. CD represents a challenge for physicians owing to its multiple associated conditions involving growth and pubertal development; thus, it is important to achieve an early diagnosis and treatment in order to control hypercortisolism and improve the prognosis. Its rarity in pediatric patients has led physicians to have limited experience in its management. The objective of this narrative review is to summarize the current knowledge about the pathophysiology, diagnosis, and treatment of CD in the pediatric population.