Theory and performance of high frequency lattice mixers

Restricting the local oscillator to a sinusoidal current drive the performance of four types of lattice mixers is examined by deriving closed form equations (as compared with the usual numerical computer-aided approach), the effects of the diode parasitics being included. It is shown that the duality between Z and Y and between G and H mixers is not generally valid (as has been assumed by several workers) except when the diode is regarded as having bi-linear or exponential characteristics and in addition the effect of the diode parasitics is neglected. It is concluded that the H lattice mixer offers the best possibility of producing the lowest conversion loss in practice. The effect of the diode reactive parasitics (diode package and junction capacitances) on the performance of lattice mixers is also examined. In all the known literature, the diode capacitance parasitics are only included in small-signal analysis and their effect on the local oscillator waveform is ignored. It is shown, however, that the main effect of the diode capacitive parasitics is to modify the local oscillator current waveform present at each diode. It is further shown that this effect has a considerable influence on the performance of lattice mixers. Microstrip coupled-lines constitute a fundamental building block for the realization of filters associated with image-rejection mixers. The design information on such lines is normally presented in graphical form and only for particular values of relative permittivities of the substrate. To overcome this problem an analytical solution has been developed which relates the physical dimensions of the lines to the odd and even-mode impedances

Randomized phase 1b trial of MOR103, a human antibody to GM-CSF, in multiple sclerosis

Objectives: To determine the safety, pharmacokinetics (PK), and immunogenicity of the recombinant human monoclonal antibody MOR103 to granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with multiple sclerosis (MS) with clinical or MRI activity.Methods: In this 20-week, randomized, double-blind, placebo-controlled phase 1b dose-escalation trial (registration number NCT01517282), adults with relapsing-remitting MS (RRMS) or secondary progressive MS (SPMS) received an IV infusion of placebo (n = 6) or MOR103 0.5 (n = 8), 1.0 (n = 8), or 2.0 (n = 9) mg/kg every 2 weeks for 10 weeks. Patients had to have ≤10 gadolinium (Gd)-enhancing brain lesions on T1-weighted MRI at baseline. The primary objective was safety.Results: Most treatment-emergent adverse events (TEAEs) were mild to moderate in severity. The most frequent was nasopharyngitis. Between-group differences in TEAE numbers were small. There were no TEAE-related trial discontinuations, infusion-related reactions, or deaths. Nine patients experienced MS exacerbations: 3, 5, 1, and 0 patient(s) in the placebo, 0.5, 1.0, and 2.0 mg/kg groups, respectively. A few T1 Gd-enhancing lesions and/or new or enlarging T2 lesions indicative of inflammation were observed in all treatment groups. No clinically significant changes were observed in other clinical assessments or laboratory safety assessments. No anti-MOR103 antibodies were detected. PK evaluations indicated dose linearity with low/no drug accumulation over time.Conclusions: MOR103 was generally well-tolerated in patients with RRMS or SPMS. No evidence of immunogenicity was found.Classification of evidence: This phase 1b study provides Class I evidence that MOR103 has acceptable tolerability in patients with MS

Investigation of the equivalent circuit parameters and design of a dual polarised dual frequency aperture coupled microstrip antenna.

This communication presents a simplified approach to the design of a single feed dual polarised, dual frequency (1.9 and 2.4 GHz) aperture coupled microstrip antenna. Using simulation and practical investigation, the coupling between the microstrip feed line and aperture, along with the coupling between the aperture and patch, is investigated and modelled using equivalent transformers. The results obtained are used to reduce the number of interdependent design parameters, thereby allowing initial approximate values to be determined more directly with only fine tuning subsequently required to obtain good matching at both frequencies. Excellent agreement is obtained for the simulation and practical results of the return loss and the gain of the antenna

Application of segmentation analysis to a matched U-slot patch antenna

A wide impedance matching bandwidth or multi-band response can be obtained using a single layer U-slot rectangular antenna with a probe feed. However, the determination of the input impedance of this antenna has not been reported. In this letter using segmentation analysis a new explicit matrix input impedance formula has been derived. The U-slot rectangular antenna is partitioned into rectangular segments and the system of coplanar matrix circuit equations is reduced by cojoining pairs of equations. The reduced system is then solved to obtain a new explicit matrix input impedance formula. This technique has the potential to be applied to other multi-segmented antenna geometries. Two antennas operating at 2.45 GHz were fabricated, one with a substrate of thickness 1.575 mm and the other with a substrate of thickness of 3.175 mm. For both antennas there is an excellent agreement between the predicted, simulated, and measured results for the input impedance