IntroductionAfter COVID-19, many continue to experience persistent debilitating symptoms, that is, long COVID. Its most prevalent symptoms are chest pain, difficulties with breathing, painful ...muscles, ageusia or anosmia, tingling extremities and general tiredness. This paper describes the protocol of the Long COVID Cohort Study to assess the prognosis and prognostic determinants of patients with long COVID by implementing patient-reported outcome measures (PROMs), patient-reported experience measures (PREMs) and clinical examinations during a 1-year follow-up.Methods and analysisThis is a prospective, single-site cohort study consisting of administering questionnaires and clinical examinations to adult patients referred to the Clinic for Long-Term Effects of COVID-19 at Helsinki University Hospital (Hospital district of Helsinki and Uusimaa). The referrals are from all healthcare units within HUS and other hospital districts during years 2021–2023. All admitted patients have had laboratory-confirmed COVID-19. The targeted study sample size is 500 participants. The questionnaires are administered at 0, 3, 6 and 12 months. The main outcome variables are the changes in self-reported functional abilities and quality of life. In addition, we will evaluate functional abilities at baseline using neurocognitive evaluation, a 6MWT and a measurement of hand grip strength. The Long COVID Cohort Study will form a quality register for the clinic and characterise the first systematic collection of PROMs, PREMs, questionnaire and clinical examinations related to long COVID in Finland. The Study belongs to a study consortium Long COVID—HORIZON-HLTH-2021-DISEASE-04 that aims to reveal the biomechanisms of long COVID.Ethics and disseminationThis study has been approved by the Helsinki University Hospital research ethics committee board, ID HUS/1493/2021 on 6 March 2021. All study participants sign written informed consent for participation. The study findings will be reported for publication in peer-reviewed journals.Trial registration numberNCT05699512; Pre-results.
This paper focuses on the design aspects of the key components for a scalable phased-array system over the 200 GHz frequency range. A high-gain phase shifter chain for 220 to 240 GHz frequency range ...and a high-gain power amplifier (PA) with a high output power are designed in a 0.13-μm SiGe BiCMOS technology. The phase shifter chain includes a low-noise amplifier (LNA), a vector modulator phase shifter (PS), and a gain-enhancing amplifier. The LNA is a five-stage cascode design. The vector modulator core is realized by two variable gain amplifiers based on the Gilbert cell architecture. A four-stage cascode design is used for the gain-enhancing amplifier. The phase shifter chain shows a measured gain of 18 dB at 230 GHz with a 360° phase tuning range and more than 10 dB of gain control. The chip achieves a minimum measured noise figure of 11.5 dB at 230 GHz and shows a wideband noise characteristic. The complete phase shifter chain chip consumes a dc power of 153 mW and occupies a 1.41 mm 2 area. A high-power PA that is critical for a large phased-array system is designed. This paper presents a unique 4-way power combining technique utilizing a differential quadrature coupler. The realized balanced PA occupies an area of 0.67 mm 2 and shows a measured peak gain of 21 dB at 244 GHz. The PA consumes 819 mW of dc power and delivers a maximum saturated output power ( P sat ) of 7.1 dBm at 244 GHz and more than 4.3 dBm of P sat from 230 to 255 GHz.
A beam-switching array is designed using a <inline-formula> <tex-math notation="LaTeX">4\times 6 </tex-math></inline-formula> Rotman lens as a beam-forming network to switch the beam towards −30°, ...−10°, 10°, and 30°. Six substrate integrated waveguide fed <inline-formula> <tex-math notation="LaTeX">1\times 4 </tex-math></inline-formula> microstrip patch arrays are used as the radiating elements. The beam-switching array is designed on the LTCC substrate to operate at 71-76 GHz. In this work, the feasibility of implementing a beam-switching network with a vector modulator (VM) integrated circuit as switching element is studied for the first time. The measured radiation pattern of the beam-switching array with the VM is in line with the simulated radiation pattern. The measured peak realized gain of the beam port 1, 2, 3, and 4 with 3-dB backoff gain of the VM are 17, 17, 17.8, 16.9 dBi at 75 GHz, respectively. In addition, the work demonstrates the possibility of beam-reconfigurability in beam-switching array by simultaneous excitation of the beam ports in optimum phase using the VM. The simultaneous excitation of the adjacent two ports, 1-2, 2-3, and 3-4, steer the beam towards −19°, 0°, and 19°, respectively, which improves the beam cross-over level. With various combinations of simultaneous excitation, the half power beam-width of the beam-switching array is varied from 17.8° to 75°.
We present two W-band amplifiers, one implemented using conventional coplanar waveguides and unshielded passives and the other using slow-wave shielded waveguides and passives, realized in a 65-nm ...baseline CMOS technology. The measured results suggest that the slow-wave shielding of the passives is useful in achieving high performance and high frequency of operation. Our custom layout slotted plate capacitor employing slow-wave shield has low parasitic series resistance. Furthermore, as the substrate losses are minimal the modeling becomes more accurate. The measured based amplifier achieves +10 dBm output power at 100 GHz with a 1.2 V supply and 70 mA total DC-current consumption. The noise figure and gain at 100 GHz are 7.5 dB and 13 dB, respectively. The chip size of the implemented slow-wave amplifier is 0.33 mm 2 .
In this letter, we have presented a design of on-chip millimeter-wave 3-dB quadrature coupler that utilizes the coupled slow wave coplanar waveguide. The designed CMOS coupler covers the whole ...<inline-formula> <tex-math notation="LaTeX">E </tex-math></inline-formula>- and <inline-formula> <tex-math notation="LaTeX">W </tex-math></inline-formula>-band and occupies a silicon area of only 0.0115 mm 2 , which is significantly smaller compared to the conventional microstrip-line-based Lange couplers. Measurement of the quadrature coupler shows a −3.5 dB through and a −4.4-dB coupling at 90 GHz. A less than ±1-dB amplitude and a ±4° phase errors from 55 to 110 GHz are recorded.
We describe an integrated radiometer at 240 GHz consisting of a direct detection MMIC fabricated in BiCMOS SiGe and a silicon gradient refractive index (GRIN) lens. The planar GRIN lens enables ...placing the MMIC with an on-chip dipole antenna directly on the GRIN lens in the focal point of the lens. We describe, how this method of integration can be extended to larger detector arrays while presenting results of a single pixel in this article. The direct detection MMIC includes an on-chip dipole antenna, a low-noise amplifier (LNA), and a diode detector. The radiometer bandwidth (BW) is 38 GHz, defined by the monolithic microwave integrated circuit (MMIC). The GRIN lens is fabricated in high-resistivity silicon and has a gain of 12.2 dBi at 240 GHz with an on-chip feed antenna. The integrated radiometer achieves noise-equivalent temperature difference (NETD) of 0.5 K/Hz1/2. The radiometer with external chopping is stable up to an integration time of 100 s, as demonstrated by the Allan variance measurement, where an NETD of 0.03 K with 100-s integration time is measured.
In this article, a 60-GHz frequency-modulated continuous-wave (FMCW) multiple-input multiple-output (MIMO) radar system using frequency-division multiplexing for TX signal separation is presented. ...Four-channel transmitter and receiver chips were designed using 130 nm SiGe process. The total number of TX and RX channels can be scaled by the number of chips in the system while still maintaining phase coherence between the channels. 2-D and 3-D object localization measurements are made with four TX and eight RX channel systems. In the 2-D configuration, the radar system is capable of a 5-cm range resolution and 3.5° angular resolution.
We aimed to identify clinically relevant clusters among patients with post-Covid-19 condition (PCC) and assess prognosis overall and within clusters.
Prospective cohort study of patients with PCC ...attending a rehabilitation clinic. We monitored patient reported outcome measures (PROMs): EuroHIS quality of life and symptoms. Unsupervised hierarchical cluster analyses were performed to identify clusters of patients with different quantity of symptoms, and symptoms presenting together. Preliminary findings on symptom prevalence and quality of life at 12 months are reported.
Among 409 patients, 70.4% were women, with an average baseline of 20.3 (SD 6.8) symptoms. Three clusters emerged based on symptom quantity, labelled by the average number of symptoms at baseline: Cluster-11 (17% of all patients), Cluster-17 (35%), and Cluster-25 (48%). Multinomial logistic regression showed female sex, multiple comorbidities predicting more symptoms. Four symptom-based clusters were defined: fatigue and cognitive complaints; pain, trouble sleeping, palpitations and other symptoms; gastrointestinal symptoms; and emotion-related symptoms. Linear regression models showed that female sex, multiple comorbidities, anxiety, use of antidepressants, BMI and smoking were among the determinants of symptom clusters. In 12-month follow-up, symptom count decreased, and quality of life improved across all clusters, with 9% having good quality of life at baseline and 33% at 12 months.
Four patient clusters based on symptoms were identified in the PCC cohort. Prognosis was favorable across all clusters, with symptom reduction and improved quality of life observed. Female sex, comorbidities, BMI, and mental-health related variables predicted higher symptom burden, suggesting multifactorial origins of PCC.
•Patients with post-Covid condition were studied at a rehabilitation clinic.•They had on average 20 symptoms from the list of 35 symptoms at baseline.•Four symptom clusters were defined in hierarchical clustering.•At follow up at 12 months, the patients had on average 15 symptoms.•Quality of life measured by EuroHIS improved in all symptom clusters.
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