Microwave Engineering Europe - January/February 2008 - (Page 29)

FAST SMALL ANTENNA TEST 29 Figure 4: Bluetest High Performance chamber with an isolation of 100 dB. the propagation paths in a Rayleigh fading environment look like between the MIMO antennas and the three ﬁxed antennas, i.e. the channel matrix H. If you know this matrix it is possible to calculate the throughput capacity with Shannons capacity formula: C = log2(det (IM +(SNR/3)HH*)) With a multi port network analyzer such a measurement can be performed in only one minute in the High Performance chamber. The reverberation chamber also offers completely new types of MIMO measurements in a repeatable and controllable environment, for example complete system tests with both a WLAN base station and a laptop terminal. It is then possible to optimise the antenna conﬁgurations at both base station and laptop for optimal transmission speed in a environment with rich scattering. Pros and cons with reverberation chambers One advantage compared with the traditional measurement method in anechoic chambers is that you can start your measurements much faster since it is very easy to position the DUT communication must also take place in a fading environment, so there are different propagation paths that are relatively uncorrelated. The more fading the better. Furthermore, the most important parameter is that the antennas used have high antenna efﬁciency. We saw in the diversity case above that the antenna efﬁciency is decreased when antennas are in close proximity. In the reverberation chamber it is possible to measure what in the chamber. The measurements are very fast and it takes only one minute for antenna efﬁciency, total radiated power, diversity and MIMO to be measured and only ﬁve minutes to measure receiver sensitivity at a certain bit error rate. The measurements have high accuracy, the chambers are small and in relation to anechoic chambers have low cost (Figure 4). A possible disadvantage is that you cannot measure antenna patterns. Antenna patterns are usually not important or of interest for small antennas since their patterns are omni directional with low directivity. Even if there is a small directivity, the orientation of the antenna, at least for mobile phones etc., is rather random depending on how you hold or position the mobile phone. The p most important parameter for small antennas is its antenna efﬁciency which can take a long time to measure in an anechoic chamber but is easy and fast to measure in a reverberation chamber. Company Information Bluetest AB www.bluetest.se U M T S P o w e r A m p l i f i er WCDMA PA orld C Mobile W - 14th February 11th na Barcelo 7C74 , Stand Hall 7 at: Visit usngress 2008 o Mitsubishi Electric is offering a complete set of high efficiency power amplifiers for UMTS mobile applications. Mitsubishi's PA's are well recognized in the cellular market for highest efficiency and excellent performance. They are available for several interfaces and many UMTS bands. www.mitsubishichips.com · semis.info@meg.mee.com MITSUBISHI ELECTRIC EUROPE B.V. (Semiconductor European Business Group) Gothaer Straße 8 · D-40880 Ratingen · Phone: +49 (0) 2102/486 0 · Fax: +49 (0) 2102/486 4140 Microwave Engineering ● January/February 2008 ● www.mwee.com 024_025_026_028_029_MWEE.indd 29 24/01/08 15:16:32 http://www.bluetest.se http://www.mitsubishichips.com http://www.mitsubishichips.com http://www.mwee.com

Table of Contents Feed for the Digital Edition of Microwave Engineering Europe - January/February 2008

Microwave Engineering Europe - January/February 2008 Contents News Comment Radio: Raising the Bar for the Radio: Making 802.11n Work Cover Feature: The RF-System-In-Package Trend - Efficient Design with Advanced Design System 2008 Wireless Sensor Networks: The Zigbee PRO Feature Set: More of a Good Thing Very Fast Measurements of Wireless Devices with Small Antennas in Reverberation Chambers WiMAX Update 2008 Bridging the Gap from the CMOS DSP to the Antenna in OFDM Systems Products Calendar

Microwave Engineering Europe - January/February 2008

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