Topics

• WP 2.2.F.2 (Transmitter Architecture) has started
• TARGET feature article on "IST Results"

Events

• 2nd TARGET Winter School: "Microwave Transistors: Materials and Devices"
• TARGET at the GigaHertz 2005 - I
• TARGET at the GigaHertz 2005 - II

TOPICS

WP 2.2.F.2 (Transmitter Architecture) has started

On October 1st, at the occasion of the European Microwave Conference, the kick-off of the WP 2.2.F.2, TX Architecture of Broadband Wireless Access, was held. This WP collects the efforts of 17 academic and industrial partners spread among 7 European countries. The duration of the WP will be 24 months and during this period the main focus will be on the investigation of the analysis and design issues in the frame of reconfigurable radio systems. These are radios that can change to different communication protocols as they move between different radio environments. An example would be moving from 802.11b to 802.11a and then to W-CDMA (Wideband Code Division Multiple Access). This activity tries to give a contribution to the dreams of having access to radio technologies able to connect anytime, anywhere, using single radio platforms integrated into any device one could choose.

The WP activities are aimed at the development of possible Multiband Multistandard Reconfigurable Radio (MMRR) Architectures that will concurrently support multiple radio protocols over multiple frequency bands across multiple wireless networking environments. Analog RF SiGe BiCMOS demonstrators will also be produced as an efficient vehicle to test new design solutions that will enable multiple, and eventually reconfigurable, RF front-end.

The most challenging design problems relates the PA efficiency and linearity obtained in a reconfigurable scenario, the PLL frequency generation and hopping over the desired bands, the filtering requirements just to cite the most relevant. All the above features must consider a non ideal environment that poses further complexity in the design. The reconfigurability is generally addressed with switched passive components, the selection of different active devices or different bias conditions, all these options take paramount benefits from the RF-MEMS features.

MMRR systems that consider IEEE 802.16 (WiMAX) have to face the problems related to high degree of linearity. Linearity implies higher power consumption and this collide with efficiency. For WiMAX, a power amplifier can work at 4 to 5% efficiency for about a 6 dB backoff from output. Such a backoff results in about a 2.5% Error Vector Magnitude (EVM) or 32 dBc of Signal to Noise plus Distortion (SNDR). With a class AB Power Amplifier (PA) the efficiencies can run as high as 15 to 18% with similar EVM numbers. A much overlooked parameter in PA design is settling time. When a PA is switched on from cold the power level will overshoot (or undershoot), then settle out. This settling time can be as poor as hundreds of msec to get within 0.1 dB of the final value. For OFDM symbols, the RX has to estimate the power of a tone from the beginning of a frame to the end of a frame. If there is a droop of power from the beginning to the end of >0.1 dB, the BER for 64 Quadrature Amplitude Modulation (QAM) will increase. The primary cause for this power droop is related to the thermal memory effects. In some cases the PA may have to be turned on ahead of the TX cycle to allow the PA to stabilize and remove some of the droop. This implies having a trigger signal added when data is to be transmitted. Having the MAC and PHY realize this trigger is not a simple matter. The budget of 100 usec for HFDD is taken up by the synthesizer settling and any PA turn-on issues. A possible solution is to design the PA so that the PA settling is <5 usec.

The above highlights are just to give the flavor of the challenging and fascinating problems WP 2.2.F. "TX Architecture of Broadband Wireless Access" is expected to provide solutions.

Alessandro Cidronali

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TARGET feature article on "IST Results"

On 2 December 2005 IST Results publicised a 1-page feature on TARGET entitled "Collaboration brings results on microwave amplifiers" describing the goals as well as the latest achievements of the NoE (read the article). The IST Results service (http://istresults.cordis.lu/) gives online news and analysis on the emerging results from the EU Information Society Technologies research programme.

Sue Raab

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EVENTS

2nd TARGET Winter School: "Microwave Transistors: Materials and Devices"

This intensive, four-day course will provide a thorough understanding of the essential background of RF transistor function and production methods. Intended for PhD students and engineers new to the field this course will focus both on theoretical and practical issues of established techniques and most up-to-date methods as well.

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TARGET at the GigaHertz 2005 - I

On November 8-9 the GigaHertz 2005 Symposium took place in Uppsala, Sweden. The conference is the natural meeting point in Sweden for scientists and engineers in the broadening field of device and circuit technology for microwave and RF applications. For the first time TARGET was also present at this event.

Special topics for the symposium this year were microwave technologies for medicine, security, vehicles and space applications. Of particular interest were technologies for microwave sensors.

This year a TARGET special event was also arranged. A highlight of the symposium was the special joint session on “Microwave circuits and RF MEMS” with invited presentations from the NoE’s TARGET and AMICOM. From TARGET J. Würfl and I. Magrini gave much appreciated presentations on the topics of GaN/AlGaN HEMT technology and SiGe BiCMOS transceiver solutions, respectively.

All together the conference and the TARGET special event were a big success. Over one hundred participants from both academy and industry had the chance to get together and exchange information, experience and new ideas.

Jörgen Olsson

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TARGET at the GigaHertz 2005 - II

On behalf of TARGET Dr. I. Magrini from MIDRA - University of Florence, presented a joint paper entitled “System Level Analysis of a Transceiver Solution for the UWB IEEE 802.15.3a in SiGe BiCMOS Technology”. The paper was aimed at the description of the most recent achievements in terms of system-level analysis in the frame of the WP22F1 ‘Transmitter modelling for wireless broadband access’. In particular, possible transceiver architecture for the UltraWide Band (UWB) standard IEEE 802.15.3a was discussed that was designed to support a Multi-Band OFDM (MB-OFDM) modulation scheme and was based on direct conversion in the TX and RX paths. Particular emphasis was reserved to the system-level analysis for the determination of the sub-systems specifications; in particular, it considered the LNA noise figure, the mixer LO isolation and gain, and the synthesizer specifications. On the TX side it was demonstrated that a proper design of the mixer leads to a removal of the PA connected with a dramatic reduction of system complexity. The spectrum mask compliance was verified implementing appropriate behavioural models in the co-simulator under the Agilent-ADS CAD, allowing a full investigation and optimization of the sub-systems’ key parameters.

Agilent-ADS co-simulation environment for the UWB-TX analysis

The approach based on the use of subsystem behavioural models, developed within the framework of the TARGET - WP22F1 ‘TX modelling for broadband wireless access’, allows not only a reduction of the analysis time but also the verification of available sub-systems specifications with the required system level performance. The latter opportunity turns out to be quite important for the reduction of the time to market and the development of early products. The presentation gathered a lot of interest from the audience stimulating new efforts and development in this emerging fields and confirming that the activities carried on by the TARGET NoE are on the right track.

The occasion was interesting to foster technical discussions that were previously undertaken with the NoE-AMICOM fellows. Liaison with AMICOM was procured by Prof. Yasar Gurbuz (Sabanci University) under the initiative of Dr. Alessandro Cidronali (Univ. of Florence).The main topics under evaluation are: a joint meeting between TARGET and AMICOM, the organization of a MPW runs for MEMS and the contribution to the open platform on RF MEMS and RF Microsystems.

Alessandro Cidronali

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Imprint

published by: ftw. Forschungszentrum Telekommunikation Wien Betriebs-GmbH, Donau-City-Straße 1, 1220 Vienna, Austria, Phone +43/1/5052830-0

responsible for content: Prof. Dr. Gottfried Magerl, Mag. Sue Raab