This letter presents a two-element conformal antenna for receiving the GPS L1, L2 and GLONASS L1 signals for precision artillery applications. The antenna consists of two stub-loaded shorted conformal patches fed by coaxial cables and a stripline power combiner. The patch is realized on a cylindrical polymer substrate wrapped around an artillery fuze body. Two patches are placed 180 apart and combined to realize an omni-directional pattern. The fabricated antenna shows good GNSS signal receiving performance.

This study presents a new S-band-receiving phased-array antenna with a phase-deviation-minimized calibration method for the ground station of a low Earth orbit (LEO) satellite. The proposed antenna consists of 16 subarrays, 16 beamforming receiving RF modules (BF-RFMs), a power/control board, and a 16-way feed network. The subarray was achieved by joining two 8 × 1 arrays with a two-way power combiner. The 16-element antenna subarrays showed a gain of 16.1 dBi and a reflection coefficient of less than −10 dB from 2.12 GHz to 2.45 GHz. The BF-RFM, which consists of three low-noise amplifiers (LNAs), a power combiner, a phase shifter, and a digital attenuator, was designed and fabricated. The BF-RFMs were provided by the power/control board and showed a gain of 30.8 ± 0.8 dB, an amplitude root-mean-square (RMS) error from 0.25 dB to 0.28 dB, and a phase RMS error from 1.8° to 2.5° over the Rx frequency range. The arrangement procedures of the 16 BF-RFMs are presented to increase beam pointing accuracy at the desired angle. A commercial 16-way feed network was employed to combine all the output ports of the 16 BF-RFMs. The assembled antenna, which has dimensions of 1.58 m × 1.58 m × 0.2 m, was measured by partial and full scans in the near-field scanning system. The back-projected algorithm was employed to calibrate the antenna’s gain patterns in the partial scan. The implemented phased-array antenna had a gain greater than 28.14 dBi, sidelobe levels less than −17.1 dB, and beam pointing errors less than 0.07° over the beam pointing angle of −20~+20°. Based on the implemented antenna system, we conducted a field test using KOMPSAT-5, which is actually operating in South Korea, in order to verify the performance of the low Earth orbit (LEO) satellite ground station system.

This paper presents a new dual circularly polarized feed that provides good axial ratio over wide angles and low cross-polarized radiation in backward direction. A circular waveguide open end is fed with two orthogonally polarized waves in phase quadrature by a pair of printed crossed dipoles and a compact connectorized quadrature hybrid coupler. The waveguide aperture is loaded with a dielectric cylinder to reduce the cross-polarization beyond 90 degrees off the boresight. The fabricated feed has, at 5.5 GHz, 6.33-dBic copolarized gain, 3-dB beamwidth of 106°, 10-dB beamwidth of 195°, 3-dB axial ratio beamwidth of 215°, maximum cross-polarized gain of −21.4 dBic, and 27-dB port isolation. The reflection coefficient of the feed is less than −10 dB at 4.99–6.09 GHz.

본 논문에서는 W-대역 탐색기용 새로운 이중편파 모노펄스 반사경 안테나의 설계를 제안한다. 4개의 정사각형 도파관으로 급전되는 새로운 이중편파 단일개구 다중모드 혼을 이용하여 모노펄스 패턴을 구현하였다. 기존의 단일개구 다중모드 혼은 단일편파에서만 동작한다. 제안된 혼의 치수변수를 반복적으로 조정하여 요구되는 합과 차패턴과 낮은 입력 반사계수를 얻었다. 설계된 피드는 다음의 합 및 차패턴 특성을 갖는다: 18.2㏈i의 합채널 이득, 22.3°에서 11.6㏈와 12.4㏈의 전계면 및 자계면 이득 테이퍼; 16.8㏈i의 차채널 이득, 22.3°에서 2.8㏈와 4.4㏈의 전계면 및 자계면 이득 테이퍼, 50㏈ 이상의의 영점깊이. 설계된 피드 혼을 50파장 카세그레인 반사경과 결합하여 고성능 W-대역 모노펄스 탐색기 안테나를 구현하였다. 설계된 탐색기 안테나는 42.2㏈i의 합패턴 이득, 1.41°의 빔폭, 1.61°의 교차각, 49.7㏈의 영점깊이, -16.8㏈의 부엽준위를 갖는다.

This paper presents a new high-performance five-element monopulse feed with a simple comparator network for Cassegrain reflector applications. The radiating element is a tapered dielectric rod fed by a circular waveguide which is in turn excited by a printed dipole. The center element is used for the sum pattern, while top and bottom elements are used for the elevation difference pattern, and left and right elements for the azimuth difference pattern. Out-of-phase excitation for the difference pattern is obtained by antisymmetrically placing two dipoles and combining their outputs with a power combiner. The optimally designed feed has been fabricated and measured. Measurement shows that the feed has the maximum sum pattern gain of 16.8 dBi, the difference pattern null depth of –21 dBi, and the reflection coefficient of less than –10 dB over 13.9–16.7 GHz.

BACKGROUND: Deficiency of ADAMTS13, vWF cleaving protease, is known to be associated with TTP and some other microangiopathies, but low levels were reported in other diseases such as ITP, DIC, lupus and other thromboses. Although inhibitory autoantibodies were demonstrated in TTP, the mechanisms underlying reduced levels of ADAMTS13 in other disorders remains unclear. We tested the hypothesis that ADAMTS13 is associated with cell membranes and derived microparticles, especially from activated platelet and their microparticles (PMP), which could modulate the enzyme activities of ADAMTS13. METHODS: PRP was prepared by centrifuging citrated normal blood for 10 min at 160×g, and PPP by further centrifuging for 10 min at 3,000×g, and particle-free plasma (PFP) by further centrifuging for 15 min at 20,000×g. ADAMTS13 activity was assayed by the FRETS-VWF73 method of Kokame et al [Br J Haematol 129:93, 2005] using the Fluoroskan Ascent plate reader. Platelets were activated by ADP (10 μM) or ionophore A23187 (2 μM). RESULTS: The ADAMTS13 activity (A) of pooled PPP of 10 controls was defined as 100%. (1) In vitro study: (1a) ADAMTS13 activity was not significantly different between PPP and resting PRP. However, if the platelets in PRP were first activated by ADP for 1hr, a significant reduction of activity was observed (A = 85 ±7%, p<0.05). If the activated platelets were removed, the activity of the supernatant fell to 79 ±10% p<0.05) of the control level, and was further reduced by higher centrifugation to remove PMP (A = 66 ±12%, p<0.01). (1b) Activation by A23187, a stronger agonist producing 2–3 fold more PMP than ADP (confirmed by flow cytometry), induced a more dramatic reduction in PRP (A = 78±8%, p<0.01), and after removal of platelets (A = 71 ±11%, p<0.01), and after removal of PMP (48 ±11%, p<0.01). (1c) Interestingly, resuspending the activated platelets did not restore ADAMTS13 activity, although resuspending the PMP did partially restore the activity. (2) In vivo study: PPP from 13 patients (6 ITP, 4 APS, 3 lupus) were analyzed. The majority (11/13) of PPP samples lost activity after removal of PMP (A = 79 ±12% in PPP vs. 64 ±11% in PFP; p <0.02). CONCLUSION: These data show that a significant but variable fraction of ADAMTS13 activity is associated with activated platelets and PMP. This has several implications. First, distinguishing soluble from membrane-bound ADAMTS13 may lead to better correlation of activities with clinical findings, and may help explain low levels of ADAMTS13 in some disorders associated with platelet activation and high PMP. Second, this interaction may play a role in regulating ADAMTS13 activity. Third, membrane-bound ADAMTS13 may clear more readily from circulation, therefore inhibiting platelet activation or MP formation may have benefits for the management of microangiopathies.