排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
Gunnarsson S.E. Karnfelt C. Zirath H. Kozhuharov R. Kuylenstierna D. Fager C. Ferndahl M. Hansson B. Alping A. Hallbjorner P. 《Solid-State Circuits, IEEE Journal of》2007,42(5):1143-1157
Single-chip 60 GHz transmitter (TX) and receiver (RX) MMICs have been designed and characterized in a 0.15mum (fT~ 120 GHz/f MAX> 200 GHz) GaAs mHEMT MMIC process. This paper describes the second generation of single-chip TX and RX MMICs together with work on packaging (e.g., flip-chip) and system measurements. Compared to the first generation of the designs in a commercial pHEMT technology, the MMICs presented in this paper show the same high level of integration but occupy smaller chip area and have higher gain and output power at only half the DC power consumption. The system operates with a LO signal in the range of 7-8 GHz. This LO signal is multiplied in an integrated multiply-by-eight (X8) LO multiplier chain, resulting in an IF center frequency of 2.5 GHz. Packaging and interconnects are discussed and as an alternative to wire bonding, flip-chip assembly tests are presented and discussed. System measurements are also described where bit error rate (BER) and eye diagrams are measured when the presented TX and RX MMICs transmits and receives a modulated signal. A data rate of 1.5 Gb/s with simple ASK modulation was achieved, restricted by the measurement setup rather than the TX and RX MMICs. These tests indicate that the presented MMICs are especially well suited for transmission and reception of wireless signals at data rates of several Gb/s 相似文献
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Tiina Sikanen Thomas Zwinger Santeri Tuomikoski Sami Franssila Reijo Lehtiniemi Carl-Magnus Fager Tapio Kotiaho Antti Pursula 《Microfluidics and nanofluidics》2008,5(4):479-491
This work presents experimental [infrared (IR) thermography] and computational (finite element model) results of temperature
distributions of an electrokinetic separation chip. Thermal characteristics of both the electrolyte solution and the polymer
chip (SU-8) are taken into account in modeling temperature distributions during electrokinetic flow. Multiphysics and multiscale
simulation couples electrostatics, heat transfer, and fluid dynamics. The accompanying IR thermography is a non-contact method,
which can measure fractional temperature differences with sub-second time resolution. Any structures or temperature marker
molecules interfering with the experiment are not needed. Nominal spot size in the IR measurements is 30 μm with a field of
view of several millimeters enabling both local and chip-scale temperature monitoring simultaneously. As a result, we present
a computer model for electrokinetic chips, which enables simulation of fractional temperature changes during electrophoresis
under real operating conditions. The accuracy of the model is within ±1°C when the deviation in electrochemical processes
is taken into account. The simulation results also suggest that the temperature on the chip surface qualitatively reflects
the temperature inside the microchannel with an average offset of 1–2°C. 相似文献
3.
E Feyzi F Lustig G Fager D Spillmann U Lindahl M Salmivirta 《Canadian Metallurgical Quarterly》1997,272(9):5518-5524
Platelet-derived growth factors (PDGFs) are homo- or heterodimers of two related polypeptides, known as A and B chains. The A chain exists as two splice variants due to the alternative usage of exons 6 (PDGF-AL, longer) and 7 (PDGF-AS, shorter). Exon 6 encodes an 18-amino acid sequence rich in basic amino acid residues, which has been implicated as a cell retention signal. Several lines of evidence indicate that the retention is due to binding of PDGF-AL to glycosaminoglycans, especially to heparan sulfate. We have analyzed the saccharide domains of smooth muscle cell-derived heparan sulfate involved in this interaction. Furthermore, we have employed selectively modified heparin oligosaccharides to elucidate the dependence of the binding on different sulfate groups and on fragment length. The shortest PDGF-AL binding domain consists of 6-8 monosaccharide units. Studies using selectively desulfated heparins and heparin fragments suggest that N-, 2-O-, and 6-O-sulfate groups all contribute to the interaction. Structural comparison of heparan sulfate oligosaccharides separated by affinity chromatography on immobilized PDGF-AL showed that the bound pool was enriched in -IdceA(2-OSO3)-GlcNSO3(6-OSO3)- disaccharide units. Furthermore, analogous separation of a partially O-desulfated heparin decamer preparation, using a highly selective nitrocellulose filter-trapping system, yielded a PDGF-AL-bound fraction in which more than half of the disaccharide units had the structure -IdceA(2-OSO3)-GlcNSO3(6-OSO3)-. Our results suggest that the interaction between PDGF-AL and heparin/heparan sulfate is mediated via N-sulfated saccharide domains containing both 2-O- and 6-O-sulfate groups. 相似文献
4.
G Camejo G Fager B Rosengren E Hurt-Camejo G Bondjers 《Canadian Metallurgical Quarterly》1993,268(19):14131-14137
Chondroitin sulfate-rich proteoglycans secreted by arterial intima smooth muscle cells appear involved in low density lipoprotein entrapment and modification. Hypothetically, such a process may contribute to atherogenesis. We compared composition and size of those proteoglycans synthesized by proliferating and resting human arterial smooth muscle cells for which low density lipoprotein had affinity. Lipoprotein-binding proteoglycans secreted by proliferating cells were larger than those of resting cells (M(r) = 1.1 x 10(6) versus 0.8 x 10(6). This was primarily caused by increased M(r) of the chondroitin sulfate chains (6 x 10(4) versus 3.5 x 10(4)). The glycosaminoglycan chains of the proteoglycans from both cells were made of more than 90% chondroitin 6-sulfate and chondroitin 4-sulfate in a 6:4 ratio. Affinity chromatography indicated that low density lipoprotein had a higher affinity with the proteoglycans synthesized by proliferating cells than those from resting cells. Measured with gel mobility shift assay, the apparent affinity constant of low density lipoproteins for proteoglycans from proliferating cells was 3-fold higher than that for proteoglycans from resting cells. This increased affinity appeared related to the higher relative proportion of proteoglycans with longer glycosaminoglycan chains secreted by the proliferating cells than those secreted by the resting cells. 相似文献
5.
On the basis of the "Dollard and Miller… principle that 'increasing the strength of the drive raises the entire gradient of generalization… ' [and that]… such emotional states as fear, anxiety, and guilt can acquire the properties of a drive… . The present research investigates the hypotheses that there are differences in the shape of the SG gradients among psychotic, neurotic, and control Ss… . The results indicate that (a) the psychotics showed more generalization than the nonpsychotics; (b) the neurotics showed less… than the psychotics, but did not differ from the controls; and (c) the brain-damaged Ss showed more generalization than the nonpsychotics, but they did not differ from the psychotics." (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
An evaluation of a 26.3% relative efficiency Ge(Li) detector for low-level radionuclide analysis has been made. The detector performance for sources mounted at the detector end cap was compared with the other smaller Ge(Li) detectors and with an opposed Ge(Li) two detector system. Factors studied included resolution, peak-to-Compton ratios, background, detection efficiency at the end cap, source geometry, and relative sensitivity. The 26.3% relative efficiency detector was found to give superior end cap efficiencies, peak-to-Compton ratios, and relative sensitivities without sacrificing performance in the other factors studied. 相似文献
7.
Nadia Chagtmi Noureddine Boulejfen Weiwei Zhang Abul Hassan Christian Fager Fadhel M. Ghannouchi 《国际射频与微波计算机辅助工程杂志》2019,29(2)
Two architectures of concurrent dual‐band six‐port‐based receiver (SPR), which are modeled and calibrated using the augmented Hammerstein model (AHM) are proposed for the first time in this article. The receivers are based on six‐port junctions with one or two local oscillators (LO). The proposed single step calibration algorithms achieve the recovery of the two in‐phase (I1 and I2) and quadrature (Q1 and Q2) components of an RF signal with two frequency components (RF1 and RF2). Experimental validations have been performed to verify the performance of the proposed concurrent dual‐band receivers and to test the efficiency of the AHM based calibration algorithms. As a performance metric, the Error Vector Magnitude (EVM) has been measured to compare the transmitted and recovered baseband signals and to evaluate the performance and efficiency of the proposed calibration algorithms for the two receiver topologies. The IQ data has been recovered with EVMs no higher than 2% for the two LOs based receiver excited with a QAM modulated dual‐band RF signal. The single LO based receiver has been tested with a dual‐band LTE signal and the recovered IQ data exhibited EVMs no higher than 4%. 相似文献
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A balanced FET frequency-modulated continuous-wave radar transceiver designed to suppress AM noise is presented. The transceiver utilizes the same device for output power amplification as for down-conversion of the received signal, thereby avoiding the need for separation of these signals. This makes the transceiver suitable for integration in monolithic-microwave integrated-circuit technology. A test circuit operating at 10 GHz was designed. The AM noise suppression is characterized, as well as output power and noise performance. Comparison with an unbalanced transceiver using the same principle of operation shows an improvement of 20 dB in AM noise performance. The output power is 14 dBm at 7-dBm input power 相似文献