A novel ultra compact microwave tuneable impedance transformer topology is proposed. It consists of a classical p CLC network where an equivalent tuneable inductance is realised with a high impedance transmission line in series with fixed inductance and a diode's varactors. The realised hybrid prototype at 900 MHz operating frequency is only 0.06l-long. Impedance loads from 16.5 to 280 O can be matched with a return loss better than À20 dB, and the relative bandwidth equals AE 36% for a fixed 50 O load.Introduction: Impedance transformers are widely used for microwave applications such as matching networks, filters, power dividers, etc. Tunable impedance transformers could offer interesting possibilities and constitute a great challenge in the field of modern telecommunication systems. For example, they could be used in microwave amplifiers matching networks to modify, after realisation, their behaviour, so that the optimal characteristics of the amplifier could be reached, even if its model is not perfectly known a priori. Also, they could be used to tune amplifier matching networks for wideband applications without sacrificing the amplifier characteristics, power gain or noise factor. We could also design tunable power dividers.Some realisations have been published on microwave tuneable impedance transformers, but not many. Sinsky and Westgate have presented a topology based on a p CLC (capacitor -inductorcapacitor) network [1]. The three elements have to be tunable to achieve a tunable impedance transformer. Tunable capacitors are realised with reverse biased Schottky diodes acting as varactors. The tunable inductor, in series between the two shunt capacitors, is realised with a shunt varactor connected between two quarter wave transmission lines.The use of quarter wave transmission lines is a problem. They reduce the device bandwidth, lead to a relatively long device (half wavelength), increasing losses, and induce a cost due to the used surface for MMIC devices. In [2], we have published an original topology, not based on a p CLC network. Its length is about a third of a wavelength, and complex loads can be matched, with a wide coverage of the Smith chart.In this Letter, we propose a topology based on a p CLC network, like [1], but the tunable inductor is not realised with a varactor inserted between two quarter wavelength transformers, leading to very small devices with a length of a few percent of wavelength. The tunable inductor is achieved by inserting a varactor (C 0 ) in series with an inductor (L), leading to a resonant circuit. Working above the resonant frequency leads to the realisation of an equivalent tunable inductor. To minimise insertion losses, the inductor value L is realised in practice with a short high impedance transmission line in series with a fixed inductance. Our first concepts, at frequencies from 1 to 10 GHz, have shown that this approach leads to impedance transformers of very small length, always lower than 10% of the guided wavelength. Moreover, the bandwidth is only limited by...
Archaeological sites can be discovered and recorded in a high-resolution and non-invasive manner using geophysical methods. These measure the spatial variation of a range of physical properties of the soil which may be representative proxies of the subsurface archaeology. Less-invasive and cost-effective field procedures have become top-priority to mitigate the destructive effects on our cultural heritage from intensified land use, climate change and the current conflict panorama. At a time when many organisations are investing in advanced geophysical equipment, a major problem is that our ability to fully interpret the information available from geophysical datasets is still very limited. This deficiency prevents geophysical survey moving beyond basic prospection and becoming a significant tool for answering nuanced questions about archaeology and their host landscapes. This limitation arises from an incomplete understanding of the relationship between soil properties and geophysical measurements. Bridging this gap requires multi-disciplinary teams, testing novel methods, plus scholarly discussion to collate the outcomes of projects on this topic. Overcoming these challenges is a prerequisite for maximising the costeffectiveness of geophysical methods, realising the expected benefits of technological investment and allowing broader utility of geophysical methods in the cultural heritage sector. SAGA will build an international network of geophysicists, archaeologists, soil scientists and other experts to develop our capability to interpret geophysical data and promote research collaborations. Our vision is that after four years, SAGA will have created an environment within which emerging field procedures, enhanced data interpretation and a broader understanding of integrated geophysical methods can flourish.
International audienceThe Roman and early medieval Richeaume XIII necropolis in Provence (France) was systematically studied using magnetic prospection and electrical resistivity tomography (ERT). Remains of a limestone‐made building are embedded in a reddish clay formation bearing iron oxides. This produces an interesting negative magnetic anomaly, whereas the wall itself is resistive. Other dipolar magnetic anomalies are correlated with the location of sepulchres, either covered by roman, strongly magnetized tegulae, or corresponding to burnt layers of cremations. After normal data processing, filtering and modelling are applied to the magnetic field data in order to more precisely define the sources. Constraints using ERTsoundings, magnetic property measurements, archaeological and geological data help to build such a source model. This study particularly emphasizes that magnetic prospection combined with ERT profiles should be suitable and sufficient on other necropolis sites in the same geological environment
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.