Unformatted text preview: Measuring Antennas in Reverberation Chamber
Per-Simon Kildal, Fellow IEEE, Charlie Carlsson, Kent Rosengren, Jan Carlsson, Andreas Wolfgang, Jian Yang Bluetest AB and Chalmers University of Technology, Sweden The radiation efficiency is the most important performance parameter of an antenna on a mobile terminal in a multipath propagation environment. The radiation efficiency can be measured in a reverbaration chamber. The radiation efficiency is reduced by three contributions: Reflections due to mismatch at input port of antenna. Absorption in antenna itself due to lossy materials. Absorption in lossy objects (phantom) near antenna. The input impedance can also be measured, as it would be seen if the antenna and the phantom were located in an anechoic chamber. This is obtained by complex averaging of S11 over the stirrer positions. Thereby the statistic contribution from the chamber is removed. The results below are for a validation case consisting of a dipole at distance from a PVC cylinder filled with tissue equivalent liquid. Bluetest RC800 reverberation chamber and setup for antenna measurements. The field is stirred by 2 mechanical stirrers, a platform stirrer, polarization stirring and 25 MHz frequency stirring. Example of real antennas on phones provided with cable for measuring RL and radiation efficiency.
0 -1 -2 Radiation efficiency [dB] -3 -4 -5 -6 -7 -8 -9 -10 750 800 850
. Photo shows validation case when it is located in anechoic chamber. 0
55mm distance Reflection Coefficient (dB) -10 20mm distance -20
Me asurement in Anechoic chamber Measurement in reverberation chamber 10mm distance 900 950 1000 Frequency [MHz] 1050 1100 -30 600 700 800 Frequency (MHz) 900 1000 1100 1200 Comparison between radiation efficiencies of validation case measured in reverberation chamber and computed with FDTD, at different distances from lossy cylinder. Comparison between reflection coefficients at dipole port, for 10 mm distance to lossy cylinder.. Bluetest AB, www.bluetest.se, Chalmers Teknikpark, SE-412 88 Gothenburg, Sweden. E-mail: [email protected] Measuring Radiated Power in Reverberation Chamber
Per-Simon Kildal, Fellow IEEE, Charlie Carlsson, Yngve Hamnerius, Nikolay Serafimov Bluetest AB and Chalmers University of Technology, Sweden The total radiated power of the phone must satisfy GSM standards, otherwise the performance of the phone is not satisfactory. The total radiated is strongly reduced in talk position. The difference is the head loss (due to absorption and mismatch). There is a correlation between head loss in W and SAR values in W/kg. TCO'01 is the first quality marking of mobile phones that has requirements to the total radiated power. This is referred to by the positive term TCP = Telephone Communication Power. The TCP can be measured in the Bluetest RC800 reverberation chamber with an expanded uncertainty of less than 1 dB (2 value).
Mean head loss in W 2,5 2,0 1,5 1,0 0,5 0,0 Max head loss in W SAR values Bluetest RC800 reverberation chamber and setup for radiated power measurements. The field is stirred by 2 mechanical stirrers, a platform stirrer, polarization stirring and 25 MHz frequency stirring. Comparison between measured TCP in W and SAR values in W/kg of same 20 phones as below.
35 34 33 32 31 30 TCP (dBm) 29 28 27 26 25 24 23 22 21 20 Free space Mean TCP The 20 measured phones (left) and example of hand phantom used in other measurements. (right).
Tilt right Cheek left Tilt left Cheek right TCP in dBm GSM900 band B (BI) T (BI) X (E) I (E) J (E) E (BI) L (EL) H (EL) Measured TCP values of 20 different phones in different CENELEC positions relative to head phantom . The phones are grouped according to their antenna type. EL = Extractable Long antenna, E = External antenna, BI = Built-In antenna
Bluetest AB, www.bluetest.se, Chalmers Teknikpark, SE-412 88 Gothenburg, Sweden. E-mail: [email protected] W (E) A (BI) C (BI) U (BI) Q (E) O (E) F (E) M (E) G (E) P (E) S (E) K (E) R (E) N (E) V (E) D (E) Measuring Diversity Gain in Reverberation Chamber
Per-Simon Kildal, Fellow IEEE, Kent Rosengren, Charlie Carlsson Bluetest AB and Chalmers University of Technology, Sweden A reverberation chamber simulates a uniform multipath environment when the modes are stirred. Diversity antennas will be used to improve performance of future mobile communication systems. The reverberation chamber is the only laboratory equipment that can measure diversity gain. The alternative is to drive the measurement equipment around in a real multipath environment, such as a in a city. The measurement setup in the Bluetest RC800 chamber is shown in the drawing. The simulated multipath environment is repeatable, so we can measure the two antenna branches one after the other. We can measure diversity gain relative to different singleantenna references. The apparent diversity gain is measured relative to one of the branches. A more practical effective diversity gain is measured relative to an ideal reference antenna, which is lossless and matched to 50 Ohms. The actual diversity gain is measured relative to an existing single-antenna solution, with a certain radiation efficiency. Definition formulas of the different diversity gains (SNR=signal-to-noise ratio): Bluetest RC800 reverberation chamber and setup for diversity measurements. The field is stirred by 2 mechanical stirrers, a platform stirrer, polarization stirring and frequency stirring. Geffdiv = Gapparentdiv (SNR ) = (SNR ) (SNR ) (SNR ) (SNR ) , G = (SNR )
div idealref div branch div (erad )branch = branch actualdiv (SNR ) (SNR ) div refcase Example of simple two-dipole diversity antenna located 2 cm from a cylinder filled with tissue-equivalent liquid. Results are given below.
Diversit y gain 10
Cu m u lat ive p ro b ab ilit y 0 Dip o le sep arat io n 2 cm
Divers it y Gain (d B) 9 8 7 6 5 4 3 2 Diversit y Bran ch es
-1 10 Act u al d iversity gain Id eal Referen ce Referen ce 2 cm clo se t o lo ssy cylin d er Co m b in ed sign al 10 -2 Effective d iversity gain 3 4 5 Distan ce b etween d ip o les (cm ) 6 -25 -20 -15 -10 -5 Relat ive p o wer level (d B) 0 Example of statistics of measured signal levels at 900 MHz. Diversity gains by selection combining at 1% cumulative probability level. The actual diversity gain is measured relative to a single dipole located the same 2 cm distance from the cylinder. 900 MHz. Bluetest AB, www.bluetest.se, Chalmers Teknikpark, SE-412 88 Gothenburg, Sweden. E-mail: [email protected] Bluetooth Measurements in a Reverberation Chamber
Charlie Orlenius, Andreas Wolfgang, Per-Simon Kildal, Fellow IEEE, Bluetest AB and Chalmers University of Technology, Sweden The radiated power of Bluetooth units can be measured in a reverberation chamber. The reverberation chamber supports a uniform field environment, i.e. all incident angles is represented in the chamber. Possible to easily include objects, such as a head phantom or a metallic table, in the setup to simulate the influence on the performance of the unit. The present setup can be used without the need for a radio communication tester. An example of a test case is shown below, where a commercial Bluetooth dongle is tested in free space and a position corresponding to normal use. Bluetest RC800 reverberation chamber and setup for Bluetooth measurements. The field is stirred by 2 mechanical stirrers, a platform stirrer, polarization stirring and 25 MHz frequency stirring.
Radios that comply with the Bluetooth wireless specification operate in the unlicensed, 2.4 GHz radio spectrum ensuring communication compatibility worldwide. These radios use a spread spectrum, frequency hopping, full duplex signal at up to 1600 hops/sec. The signal hops among 79 frequencies at 1 MHz intervals to give a high degree of interference immunity. Up to seven simultaneous connections can be established and maintained. The Bluetooth word mark and logos are owned by the Bluetooth SIG, Inc. and any use of such marks by Bluetest AB is under license. Other trademarks and trade names are those of their respective owners. Output power of a commercial Bluetooth module in free space location and inside a case mounted to a laptop computer, both measured in a reverberation chamber. Bluetest AB, www.bluetest.se, Chalmers Teknikpark, SE-412 88 Gothenburg, Sweden. E-mail: [email protected] ...
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This note was uploaded on 05/19/2010 for the course ELECTRICAL ECSE 493 taught by Professor Tholengoc during the Spring '10 term at McGill.
- Spring '10