Experimental investigation of adaptive impedance matching for a MIMO terminal with CMOS SOI tuners

It is well known that user proximity introduces absorption and impedance mismatch losses that severely degrade multiple-input multiple-output (MIMO) performance of handset antennas. In this work, we experimentally verified the potential of adaptive impedance matching (AIM) to mitigate user interaction effects and identified the main AIM gain mechanism in realistic systems. A practical setup including custom-designed CMOS silicon-on-insulator (SOI) impedance tuners implemented on a MIMO handset was measured in three propagation environments and 10 real user scenarios. The results indicate that AIM can improve MIMO capacity by up to 42% equivalent to 3.5 dB of multiplexing efficiency (ME) gain. Taking into account the measured losses of 1 dB in the integrated tuners, the maximum net ME gain is 2.5 dB suggesting applicability in practical systems. Variations in ME gains of up to 1.5 dB for different hand-grip styles were mainly due to differences in impedance mismatch and tuner loss distribution. The study also confirmed earlier results on the significant differences in mismatch and absorption between phantoms and real users, in which the phantoms underestimated user effects and therefore AIM gains. Finally, propagation environments of different angular spreads were found to give only minor ME gain variations

The negative effects of social capital in organisations: a review and extension

yesNumerous studies have examined the positive effects of social capital in organizations, whereas the possible negative effects have attracted considerably less scholarly attention. To rectify this imbalance, this paper first undertakes a rigorous review of the published scholarly empirical evidence pertaining to the negative effects of social capital in organizations through a search of Web of Knowledge and Scopus, and then enumerates six potentially negative effects arising from increased levels of social capital. Our analysis focuses on negative effects arising from bonding social capital and those arising from dense networks and closure, advancing new theory to elucidate the generative mechanisms that give rise to the proposed negative effects. Finally, we identify potential moderators of the negative effects thus theorized. Using the lens of social identification theory, we argue that dysfunctional identification processes restrict the processing of information and stimulate over commitment to established relationships, diluting in turn the dialectical process, and inhibiting individual learning within organizations, culminating in groupthink, the postponement of structural adjustments, the non-rational escalation of commitment, and the blurring of firms’ boundaries. Our analysis thus furthers the agenda of a more balanced inquiry into the effects of social capital in organizations

Integrated Transmitters for Cellular User Equipment–Wideband CMOS Power Amplifiers and Antenna Impedance Tuners

The digital cellular systems era started about thirty years ago with the release of the first digital cellphones. These first digital cellphones were very different from today’s slim and esthetic cellular pocket computers. They were not mass-produced in million units a day, and they were designed for radio performance rather than appearance. Today, all components are integrated inside the mobile phone to enable a product for the masses and not only the lucky few. For the radio performance this makes a large difference, especially the cellphones interaction with the user, which has a tendency to load the integrated antennas. This loading of the antennas means that the electronics inside the cellphone works sub-optimally, and a decrease in radio performance is inevitable, resulting in increased power consumption and reduced data rates. This problem can, however, be reduced by a concept called adaptive antenna impedance matching. This compensates for antenna loading effects, so that the electronics inside the cellphone can still operate with a close to optimum impedance, although the antenna impedance is changed due to user interaction. For adaptive impedance matching, the key component is the so called impedance tuner, which is studied, designed, and evaluated in this thesis. The requirements on this impedance tuner are very high, with low insertion loss, in-band distortion, out-of-band distortion, high tunability, and good power handling. The cost should also be as low as possible, which means that it should be implemented in a CMOS based technology suitable for mass-production. In this thesis, an impedance tuner is therefore designed and implemented in a CMOS-SOI technology. It has been verified to fulfill the requirements for use in a modern cellphone, with all measurements of key merits indicating high performance. Finally, it is worth to mention that this impedance tuner has also been used in a different project, where adaptive impedance matching was used in MIMO channel measurements with real cellphone users, but that project is outside the scope of this thesis.The range of frequencies used for cellular communication has increased over the years, and today a large part of the so called sub-6 GHz frequency range is used. Most of the wireless services we have today use this decade wide frequency range (~600-6000 MHz), and although it is a wide frequency range, the spectrum is congested with a high density of communication. The circuits used to communicate in the sub-6 GHz bands must therefore have high RF-performance, and they should also be low cost since a large number of circuits is used to cover the complete frequency range. Difficulties reducing the cost per frequency band has drastically increased the cost of today’s cellphones. This thesis therefore proposes an alternative concept for the power amplifier, the key component in the transmitter of the mobile phone, with the goal to reduce the cost of and the number of power amplifier circuits required to cover the complete sub-6 GHz range. The core of the concept was first designed and verified by measurements, an injection-locked power amplifier with supply modulation and dynamic transistor bias, resulting in high efficiency and bandwidth. To further reduce the cost of the cellphone more of the transmitter functionality, i.e. the frequency up-conversion, was added to the power amplifier circuit, which also improved the overall transmitter performance. Furthermore, a new version of polar modulation is proposed, to reduce the baseband signal bandwidth expansion, which polar modulation is notorious for. The reduction in bandwidth expansion decreases the overall power consumption of the transmitter, since the baseband circuits can then have lower bandwidth and clock-frequency. To further reduce the number of power amplifier circuits needed to cover the entire sub-6 GHz range, the bandwidth of the circuit was improved using a new higher order output matching network, together with a dual output power amplifier, resulting in a circuit that can operate with high performance over the complete sub-6 GHz frequency range. The proposed solutions in this thesis can reduce the number of ICs in cellular devices, which benefits not only the production cost, but also has positive effects on the environment

An Injection-Locked Power Up-Converter in 65-nm CMOS for Cellular Applications

This paper presents an injection-locked 65-nm CMOS circuit that upconverts and power amplifies baseband signals to RF. The circuit delivers an RF output power of 28.7 dBm, with a power gain and maximum power added efficiency (PAE) of 20.6 dB and 68.1%, respectively. Both AM–AM-conversion and AM–PM-conversion are low, less than 1 dB and 1°, respectively, resulting in an EVM of 4.7% for Long Term Evolution (LTE) and 4.1% for WCDMA signals. The circuit provides an average output power of 20.3 dBm for LTE, with a PAE of 44.1%, andfor WCDMA, the average output power is 23.8 dBm with a PAE of 55.6%. Supply modulation improves power back-off efficiency and the voltage range is from 540 mV to 3 V. The spectral mask for LTE signals has a worst case ACLR of 33.2 dBc using predistortion. For WCDMA signals, ACLR1 is 39.9 dBc and ACLR2 is 47.2 dBc, both values worst case and using baseband predistortion. This performance is achieved by introducing a cross-coupled cascode topology, and supporting theory and simulations are presented. The startup loop-gain and smallsignal equivalents are derived, a power dissipation analysis is performed, and the injection circuit is analyzed to investigate the AM–PM behavior. Analysis and simulations show that, compared to conventional cascode amplifiers, PAE is improved by 24% (15% points). The circuit is implemented in an STM 65-nm CMOS process and occupies an area of 1.0 × 0.53 mm2

A low band cellular terminal antenna impedance tuner in 130nm CMOS-SOI technology

This paper presents a low band antenna impedance tuner in 130nm CMOS-SOI technology. It consists of three digitally controlled switched capacitor banks and two off-chip inductors and is intended for use in terminals supporting modern cellular standards like WCDMA and LTE. By using a negative gate bias in the off state, linearity can be improved and maintained. Measurements show an OIP3 exceeding +55dBm for all measured impedance states, which cover a VSWR of up to 5.4. The measured minimum loss is 1dB or lower in the frequency range from 700–900MHz with spurious emissions below −30dBm at +33dBm input power. The switched capacitors are implemented with eight stacked transistors to yield a voltage handling of at least 20V, and in order to handle the large voltages custom designed capacitors are used

Reward Attention: Förslag till ett integritetsdesignmönster

Denna uppsats syftar till att utvärdera ett förslag till ett integritetsdesignmönster. Utvärde-ringen sker genom att samla in litteratur som rör integritetsfrågor och fenomen för att se vilka faktorer som är relevanta att ta i beaktande för vårt mönster. Den empiriska delen av uppsat-sen består sedan av utvärderingar från personer som har en expertis i integritetsfrågor. I mötet mellan litteraturen och utvärderingarna från våra intervjupersoner fick vi nya perspektiv och vinklar att se vårt mönster på, något som presenteras i diskussionskapitlet. Vi har därefter ut-format en ny version av vårt ursprungliga mönster, återfinns som bilaga, och presenterat både i utvärderingsdelen och i slutsatsen vad vi har ändrat på och varför