Special Component Designs for Differential-Amplifier MMICs

Special designs of two types of electronic components transistors and transmission lines have been conceived to optimize the performances of these components as parts of waveguide-embedded differential-amplifier monolithic microwave integrated circuits (MMICs) of the type described in the immediately preceding article. These designs address the following two issues, the combination of which is unique to these particular MMICs: Each MMIC includes a differential double-strip transmission line that typically has an impedance between 60 and 100 W. However, for purposes of matching of impedances, transmission lines having lower impedances are also needed. The transistors in each MMIC are, more specifically, one or more pair(s) of InP-based high-electron-mobility transistors (HEMTs). Heretofore, it has been common practice to fabricate each such pair as a single device configured in the side-to-side electrode sequence source/gate/drain/gate/source. This configuration enables low-inductance source grounding from the sides of the device. However, this configuration is not suitable for differential operation, in which it is necessary to drive the gates differentially and to feed the output from the drain electrodes differentially. The special transmission-line design provides for three conductors, instead of two, in places where lower impedance is needed. The third conductor is a metal strip placed underneath the differential double-strip transmission line. The third conductor increases the capacitance per unit length of the transmission line by such an amount as to reduce the impedance to between 5 and 15 W. In the special HEMT-pair design, the side-to-side electrode sequence is changed to drain/gate/source/gate/ drain. In addition, the size of the source is reduced significantly, relative to corresponding sizes in prior designs. This reduction is justified by the fact that, by virtue of the differential configuration, the device has an internal virtual ground, and therefore there is no need for a low-resistance contact between the source and the radio-frequency circuitry. The source contact is needed only for DC biasing. These designs were implemented in a single-stage-amplifier MMIC. In a test at a frequency of 305 GHz, the amplifier embedded in a waveguide exhibited a gain of 0 dB; after correcting for the loss in the waveguide, the amplifier was found to afford a gain of 0.9 dB. In a test at 220 GHz, the overall gain of the amplifier- and-waveguide assembly was found to be 3.5 dB

Nothing to Do with Politics, Only Art? On Wassily Kandinsky\u27s Work in Paris, from 1934 until the Outbreak of the War

Following his move to Paris at the end of 1933, Wassily Kandinsky clung to his conviction that art must remain free of politics. The purpose of this essay is to consider both the limitations and advantages of this position in the polarized political climate of the French capital and to chart the aesthetic path he embarked on after his arrival, with particular reference to the personal ties and artistic alliances that he forged (or not) in this complex cultural terrain. Far from having nothing to do with politics, the transformation his painting underwent in Paris, the period he dubbed “synthetic,” was the result of both the maturation of his ideas on abstract art and his adaptation to a rocky political and cultural landscape

Update on Waveguide-Embedded Differential MMIC Amplifiers

There is an update on the subject matter of Differential InP HEMT MMIC Amplifiers Embedded in Waveguides (NPO-42857) NASA Tech Briefs, Vol. 33, No. 9 (September 2009), page 35. To recapitulate: Monolithic microwave integrated-circuit (MMIC) amplifiers of a type now being developed for operation at frequencies of hundreds of gigahertz contain InP high-electron-mobility transistors (HEMTs) in a differential configuration. The MMICs are designed integrally with, and embedded in, waveguide packages. The instant work does not mention InP HEMTs but otherwise reiterates part of the subject matter of the cited prior article, with emphasis on the following salient points: An MMIC is mounted in the electric-field plane ("E-plane") of a waveguide and includes a finline transition to each differential-amplifier stage. The differential configuration creates a virtual ground within each pair of transistor-gate fingers, eliminating the need for external radio-frequency grounding. This work concludes by describing a single-stage differential submillimeter-wave amplifier packaged in a rectangular waveguide and summarizing results of tests of this amplifier at frequencies of 220 and 305 GHz

Multiple Differential-Amplifier MMICs Embedded in Waveguides

Compact amplifier assemblies of a type now being developed for operation at frequencies of hundreds of gigahertz comprise multiple amplifier units in parallel arrangements to increase power and/or cascade arrangements to increase gains. Each amplifier unit is a monolithic microwave integrated circuit (MMIC) implementation of a pair of amplifiers in differential (in contradistinction to single-ended) configuration. Heretofore, in cascading amplifiers to increase gain, it has been common practice to interconnect the amplifiers by use of wires and/or thin films on substrates. This practice has not yielded satisfactory results at frequencies greater than 200 Hz, in each case, for either or both of two reasons: Wire bonds introduce large discontinuities. Because the interconnections are typically tens of wavelengths long, any impedance mismatches give rise to ripples in the gain-vs.-frequency response, which degrade the performance of the cascade

Differential InP HEMT MMIC Amplifiers Embedded in Waveguides

Monolithic microwave integrated-circuit (MMIC) amplifiers of a type now being developed for operation at frequencies of hundreds of gigahertz contain InP high-electron-mobility transistors (HEMTs) in a differential configuration. The differential configuration makes it possible to obtain gains greater than those of amplifiers having the single-ended configuration. To reduce losses associated with packaging, the MMIC chips are designed integrally with, and embedded in, waveguide packages, with the additional benefit that the packages are compact enough to fit into phased transmitting and/or receiving antenna arrays. Differential configurations (which are inherently balanced) have been used to extend the upper limits of operating frequencies of complementary metal oxide/semiconductor (CMOS) amplifiers to the microwave range but, until now, have not been applied in millimeter- wave amplifier circuits. Baluns have traditionally been used to transform from single-ended to balanced configurations, but baluns tend to be lossy. Instead of baluns, finlines are used to effect this transformation in the present line of development. Finlines have been used extensively to drive millimeter- wave mixers in balanced configurations. In the present extension of the finline balancing concept, finline transitions are integrated onto the affected MMICs (see figure). The differential configuration creates a virtual ground within each pair of InP HEMT gate fingers, eliminating the need for inductive vias to ground. Elimination of these vias greatly reduces parasitic components of current and the associated losses within an amplifier, thereby enabling more nearly complete utilization of the full performance of each transistor. The differential configuration offers the additional benefit of multiplying (relative to the single-ended configuration) the input and output impedances of each transistor by a factor of four, so that it is possible to use large transistors that would otherwise have prohibitively low impedances. Yet another advantage afforded by the virtual ground of the differential configuration is elimination of the need for a ground plane and, hence, elimination of the need for back-side metallization of the MMIC chip. In turn, elimination of the back-side metallization simplifies fabrication, reduces parasitic capacitances, and enables mounting of the MMIC in the electric-field plane ("E-plane") of a waveguide. E-plane mounting is consistent with (and essential for the utility of) the finline configuration, in which transmission lines lie on a dielectric sheet in the middle of a broad side of the waveguide. E-plane mounting offers a combination of low loss and ease of assembly because no millimeter-wave wire bonds or transition substrates are required. Moreover, because there is no ground plane behind the MMIC, the impedance for the detrimental even (single-ended) mode is high, suppressing coupling to that mode. Still another advantage of E-plane mounting is that the fundamental waveguide mode is inherently differential, eliminating the need for a balun to excite the differential mode

180-GHz I-Q Second Harmonic Resistive Mixer MMIC

An indium phosphide MMIC (monolithic microwave integrated circuit) mixer was developed, processed, and tested in the NGC 35-nm-gate-length HEMT (high electron mobility transistor) process. This innovation is very compact in size and operates with very low LO power. Because it is a resistive mixer, this innovation does not require DC power. This is an enabling technology for the miniature receiver modules for the GeoSTAR instrument, which is the only viable option for the NRC decadal study mission PATH

Single-Pole Double-Throw MMIC Switches for a Microwave Radiometer

In order to reduce the effect of gain and noise instabilities in the RF chain of a microwave radiometer, a Dicke radiometer topology is often used, as in the case of the proposed surface water and ocean topography (SWOT) radiometer instrument. For this topology, a single-pole double-throw (SPDT) microwave switch is needed, which must have low insertion loss at the radiometer channel frequencies to minimize the overall receiver noise figure. Total power radiometers are limited in accuracy due to the continuous variation in gain of the receiver. High-frequency SPDT switches were developed in the form of monolithic microwave integrated circuits (MMICs) using 75 micron indium phosphide (InP) PIN-diode technology. These switches can be easily integrated into Dicke switched radiometers that utilize microstrip technology

The STRIP instrument of the Large Scale Polarization Explorer: microwave eyes to map the Galactic polarized foregrounds

In this paper we discuss the latest developments of the STRIP instrument of the “Large Scale Polarization Explorer” (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the “B-modes” of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the “Observatorio del Teide” in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization

Mediakonvergenssi kohtaa matkapuhelimen : käyttäjien kokemuksia mobiilipalvelujen käytöstä ja tulevaisuuden mobiiliviestinnästä

Only abstract. Paper copies of master’s theses are listed in the Helka database (http://www.helsinki.fi/helka). Electronic copies of master’s theses are either available as open access or only on thesis terminals in the Helsinki University Library.Vain tiivistelmä. Sidottujen gradujen saatavuuden voit tarkistaa Helka-tietokannasta (http://www.helsinki.fi/helka). Digitaaliset gradut voivat olla luettavissa avoimesti verkossa tai rajoitetusti kirjaston opinnäytekioskeilla.Endast sammandrag. Inbundna avhandlingar kan sökas i Helka-databasen (http://www.helsinki.fi/helka). Elektroniska kopior av avhandlingar finns antingen öppet på nätet eller endast tillgängliga i bibliotekets avhandlingsterminaler.Tutkielmassa tarkastellaan käyttäjien kokemuksia mobiilipalveluiden käytöstä ja tulevaisuuden mobiiliviestinnästä. Tutkielmani tavoitteena on tutkia käyttäjien nykyistä mobiilipalveluiden käyttöä ja heidän tulevaisuuden mobiiliviestinnälle antamia merkityksiä. Tutkimuskysymyksiä ovat: 1. Mobiilipalvelujen nykykäyttö?, 2. Mobiiliviestinnän tulevaisuus, mielikuvat tulevaisuuden mobiilipalveluista ja sovellutuksista?, 3. Mobiilipalveluiden käytön diskursiivinen jäsentyminen? ja 4. Mobiiliviestinnän tulevaisuuden diskursiivinen jäsentyminen? Lisäksi tutkielmassani pohditaan yleisesti matkapuhelinta mediana ja mediakonvergenssikehitystä. Tutkielmani empiirinen aineisto on kerätty haastattelemalla kuutta 24-32-vuotiasta nuorta aikuista. Haastattelut olivat avoimia teemahaastatteluja ja ne toteutettiin heinä-syyskuun aikana 2001. Teoreettinen viitekehys on diskurssianalyyttinen, mutta tutkimuskysymysten asettelun ja tulosten analyysin ja tulkinnan suhteen olen nojautunut myös nk. faktanäkökulmaan. Olen analyysissä lähestynyt aineistoani sekä faktuaalisesti että diskursiivisesti, sosiaalisen konstruktionismin näkökulmasta. Kulttuurintutkimuksen ja diskurssianalyysin näkökulmasta näen uusien ratkaisujen ja sovellutusten nykyisen ja tulevan käytön perusluonteeltaan kulttuurisena ja sosiaalisena prosessina. Faktanäkökulmasta käsin tarkastelen mobiilipalveluiden käyttöä, käytön syitä ja ongelmia, käyttötilannetta, käyttökokemuksia ja Internetin käyttöä suhteessa mobiilipalveluiden käyttöön. Tutkimuksessa arvioidaan myös mobiiliviestinnän tulevaisuuteen liittyviä kuvaa, ääntä, paikannusta, mobiilikaupankäyntiä ja mobiilimainontaa koskevia kysymyksiä. Olen faktanäkökulmassa tukenut omia tuloksiani tuoreella mobiilipalveluiden käytöstä tehdyllä kvantitatiivisella tutkimuksella. Tutkimusaineiston valossa nuorten aikuisten käyttämät näennäisesti ristiriitaiset merkityksellistämisen tavat systematisoituvat analyysin kuluessa neljäksi vaihtoehtoiseksi diskurssiksi, joiden kautta mobiilipalveluiden käyttö ja mobiiliviestinnän tulevaisuus merkityksellistetään. Tulkintani mukaan nuoret aikuiset jäsentävät ne hyöty-, huvi-, determinismi- ja uhkadiskurssien kautta. Tutkimuksen perusteella matkapuhelin mediana ja mobiilipalvelut eivät vielä ole juurtuneet osaksi ihmisten arkipäivää ja rutiineja. Mobiilipalvelujen käyttöä ja käytön syitä osana ihmisen arkea voidaan tutkimukseni tulosten perusteella jäsentää tilanne-, paikka- ja aikasidonnaisiin palveluihin, joihin usein liitetään hyöty, kuten ajan säästö ja arjen helpottaminen sekä elämyksellisiin palveluihin, joihin taas liittyy ajan kuluttaminen, viihde ja nautinto. Käytetyimpiä mobiilipalveluja ovat viihdepalvelut (logot ja soittoäänet) ja informaatiopalvelut. Mobiilipalveluiden käyttö merkityksellistyykin hyötydiskurssissa hyödyn; säästäväisyyden, arjen helpottamisen, ajan säästön ja huvidiskurssissa elämyskuluttamisen; ajan tappamisen, viihtymisen ja nautinnon välisenä dikotomiana. Mobiiliviestinnän tulevaisuus jäsentyy tulkintani mukaan determinismi- ja uhkadiskurssien avulla. Lähteinä on käytetty media-käsitettä (esim. Bolter & Gruisin 1999; McLuhan 1969; Lehtonen 2000), konstruktionismia (esim. Burr 1995; Berger & Luckmann 1994), diskurssianalyysia (Potter & Wetherell 1987; Jokinen ym. 1993; Suoninen 1992), mobiilipalvelujen käyttöä (Eriksson ym. 2001), kulttuurintutkimusta ja (Alasuutari 1992, 1994; Fornäs 1995, 1999; Foucault 1980) mobiiliviestintää (Pantzar 1996; Oksman 1998; Kangas & Googan 2001) käsitteleviä teoksia

Can You Label Less by Using Out-of-Domain Data? Active & Transfer Learning with Few-shot Instructions

Labeling social-media data for custom dimensions of toxicity and social bias is challenging and labor-intensive. Existing transfer and active learning approaches meant to reduce annotation effort require fine-tuning, which suffers from over-fitting to noise and can cause domain shift with small sample sizes. In this work, we propose a novel Active Transfer Few-shot Instructions (ATF) approach which requires no fine-tuning. ATF leverages the internal linguistic knowledge of pre-trained language models (PLMs) to facilitate the transfer of information from existing pre-labeled datasets (source-domain task) with minimum labeling effort on unlabeled target data (target-domain task). Our strategy can yield positive transfer achieving a mean AUC gain of 10.5% compared to no transfer with a large 22b parameter PLM. We further show that annotation of just a few target-domain samples via active learning can be beneficial for transfer, but the impact diminishes with more annotation effort (26% drop in gain between 100 and 2000 annotated examples). Finally, we find that not all transfer scenarios yield a positive gain, which seems related to the PLMs initial performance on the target-domain task.Comment: Accepted to NeurIPS Workshop on Transfer Learning for Natural Language Processing, 2022, New Orlean