A 100-MESFET planar grid oscillator

A 100-MESFET oscillator which gives 21 W of CW effective radiated power (ERP) with a 16-dB directivity and a 20% DC-to-RF conversion efficiency at 5 GHz is presented. The oscillator is a planar grid structure periodically loaded with transistors. The grid radiates and the devices combine quasi-optically and lock to each other. The oscillator can also be quasi-optically injection-locked to an external signal. The planar grid structure is very simple. All of the devices share the same bias, and they can be power and frequency tuned with a mirror behind the grid or dielectric slabs in front of it. An equivalent circuit for an infinite grid predicts the mirror frequency tuning. The planar property of the oscillator offers the possibility of a wafer-scale monolithically integrated source. Thousands of active solid-state devices can potentially be integrated in a high-power source for microwave or millimeter-wave applications

Bar-grid oscillators

Grid oscillators are an attractive way of obtaining high power levels from the solid-state devices, since potentially the output powers of thousands of individual devices can be combined. The active devices do not require an external locking signal, and the power combining is done in free space. Thirty-six transistors were mounted on parallel brass bars, which provide a stable bias and have a low thermal resistance. The output power degraded gradually when the devices failed. The grid gave an effective radiated power of 3 W at 3 GHz. The directivity was 11.3 dB, and the DC-to-RF efficiency was 22%. Modulation capabilities of the grid were demonstrated. An equivalent circuit model for the grid is derived, and comparison with experimental results is shown

A 100-Element MESFET Grid Oscillator

A planar grid oscillator which combines the outputs of 100 devices quasi-optically is presented. The planar configuration is attractive because it is compatible with present-day IC fabrication techniques. In addition, the grid's structure leads to a transmission-line model that can readily be applied to the design of larger grids in the future. This approach is particularly attractive for wafer-scale integration at millimeter wavelengths. The grid oscillates near 5 GHz and can be frequency tuned with mirror spacing from 4.8 GHz to 5.2 GHz. The far-field radiation patterns for the grid are shown. From the pattern, the directivity is calculated to be 16 dB. The ERP is measured to be 25 W. The DC input power is 3 W, and the power radiated from the grid is calculated to be 0.625 W. This gives a DC-to-RF efficiency of 20%

Peculiarities of SDS-PAGE of Titin/Connectin

Titin (also known as connectin) is a giant elastic protein of striated and smooth muscles of vertebrates. The molecular weight of its isoforms is 3.0–3.7 MDa in striated muscles and 0.5–2.0 MDa in smooth muscles. Titin was discovered 40 years ago using the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). At the present time, this method has not lost its relevance but has undergone a number of modifications that improve visualization of giant titin isoforms in the gel. This chapter provides historical insights into the technical aspects of the electrophoresis methods used to identify titin and its isoforms. We focus on the peculiarities of the technique because of which titin molecules remain intact and its high molecular weight isoforms can be visualized. Electrophoretic testing of changes in titin content in muscles can be used in medical practice to diagnose pathological processes and evaluate effective approaches to their correction

Taxonomic significance of palynomorphological characteristics of selected Centranthus (Caprifoliaceae) species

Pollen morphology of herbarium specimens of four Centranthus species (C. ruber, C. longiflorus, C. kellereri and C. calcitrapae) was studied using LM and SEM. The research aim was to provide data on their pollen characteristics and to evaluate the taxonomic value of these data for species-specific identification. Pollen grains are tricolpate, suboblate to prolate (P/E = 0.81–1.42); medium- or large-sized (P = 49.21–90.44 µm; E = 43.89–93.10 µm). Colpi are long or medium-length, wide at equator, tapered to acute or obtuse ends. Exine sculpture is echinate-microechinate-nanoechinate; echini (1.00–1.39 µm high) and microechini (0.55–0.98 µm) are conical, with straight or convex sides and acute apices, nanoechini are 0.22–0.46 µm high. Most important characters of taxa diagnostic at species level for the taxonomy are: size of pollen and colpi, exine structure, size of echini and microechini, and pattern of tectum in areas between echini. Pollen grains of C. calcitrapae and C. macrosiphon (sect. Calcitrapa) are generally smaller in size than grains of C. ruber, C. longiflorus and C. kellereri (sect. Centranthus). Pollen of C. kellereri was analysed for the first time in the current study

Array concepts for solid-state and vacuum microelectronics millimeter-wave generation

The authors have proposed that the increasing demand for contact watt-level coherent sources in the millimeter- and submillimeter-wave region can be satisfied by fabricating two-dimensional grids loaded with oscillators and multipliers for quasi-optical coherent spatial combining of the outputs of large numbers of low-power devices. This was first demonstrated through the successful fabrication of monolithic arrays with 2000 Schottky diodes. Watt-level power outputs were obtained in doubling to 66 GHz. In addition, a simple transmission-line model was verified with a quasi-optical reflectometer that measured the array impedance. This multiplier array work is being extended to novel tripler configurations using blocking barrier devices. The technique has also been extended to oscillator configurations where the grid structure is loaded with negative-resistance devices. This was first demonstrated using Gunn devices. More recently, a 25-element MESFET grid oscillating at 10 GHz exhibited power combining and self-locking. Currently, this approach is being extended to a 100-element monolithic array of Gunn diodes. This same approach should be applicable to planar vacuum electron devices such as the submillimeter-wave BWO (backward wave oscillator) and vacuum FET