Handset MIMO antenna measurement using a Spatial Fading Emulator

Transcription

1 Handset MIMO antenna measurement using a Spatial Fading Emulator Atsushi Yamamoto Panasonic Corporation, Japan Panasonic Mobile Communications Corporation, Japan NTT DOCOMO, INC., Japan Aalborg University, Denmark Tokyo Institute of Technology, Japan

2 Principle of the emulator Waves coming from the same direction are affected by the same Doppler effect, regardless of delay time. We can give a Doppler effect to all the waves in the same direction using one phase shifter. A phase shifter in the RF band enables us to evaluate antenna performance of a handset array excluding demodulator performance. Rx y #i #3 φ #2 #1 #31 r=1.5m #30 x 2

3 Configuration Phase shifter in the RF band can directly vary phase of the RF signal according to a Doppler frequency to perform a moving test for a handset. Proposed spatial fading emulator Scattering unit The scattering unit are arranged around the handset antenna. Waves radiated from the scattering units can produce a multipath environment. Receiver Multipath environment Attenuator Phase Shifter Power Divider Transmitter Uniform distribution Non-uniform angular power spectrum (APS) D/A Converter Computer 3

4 Scenario for MIMO channel M base station (BS) antennas create a set of M uncorrelated waves. M uncorrelated waves comprises Qc clusters surrounding around N handset antennas moving toward the azimuth direction, φ 0. Channel model of M-by-N MIMO system m=1 M TX q Cluster q=1 n=1 N RX k=1 Qc k scatterer φ 0 Moving direction K m 4

5 Purpose The purpose is to confirm effectiveness of the RF-controlled spatial fading emulator in MIMO OTA with regard to antenna measurement and handset evaluation. 5

6 Handset antennas For antenna evaluation, we made a comparison between MIMO channel capacities of a radio propagation test and OTA testing using the emulator. we used four types of handset antennas. (A) (B) (C) (D) #2 #1 #2 #1 #2 #1 #2 # [mm] 6

7 Radio propagation test The MIMO propagation test was conducted in a central area of a downtown in Aalborg city in Denmark. The handset antenna was set on a car trailer to be moved along the test route. Radio frequency was 2.35 GHz. We used the experimental data along the route 4. Base station 1 Mobile terminal

8 Channel model for the emulator We used angular power spectrum (APS) of incoming waves with a Laplacian distribution in the same manner as the spatial channel model (SCM) of 3GPP. Number of scattering unit: 31 y #i #3 φ #2 Rx #1 #31 r=1.5m #30 p x θ Model for spatial cluster ( θ, φ ) = δ ( θ ) exp σ 1 2 φ μ σ μ φ and σ are 0 and 35 degrees. The XPR is set at 9 db. φ 8

9 MIMO channel capacity The MIMO channel capacities of the OTA testing are in good agreement with those of the propagation test. The emulator is effective in evaluating the MIMO antenna by the agreement between the data obtained from the emulator and (A) the propagation (B) (C) test. (D) MIMO capacity [bps/hz] Propagation test Emulator A B C D Antenna type 9

10 2-by-2 MIMO measurement system For handset evaluation, we have constructed measurement system with a delay wave using a set of WLAN radio transceivers. The two digital fading simulators are used only for producing delay profile of the incoming waves. Spatial fading emulator for a 2-by-2 MIMO wireless LAN system Downlink VPA. Div. DFS Circulator Phase shifter Attenuator LO Circulator Uplink Isolator ATT ATT #2 #1 MS Client computer Server computer WAP #2 #1 Anechoic chamber 10

11 Measured throughput vs. delay time (fd=6hz) The MIMO throughput is almost similar to SISO in the case of fd = 6Hz because the low throughput causes a change of the transmission method from MIMO to SISO. The advantage of the MIMO configuration is obtained by only the maximum ratio combining (MRC) diversity effect. Dipole array One delay wave with the same power as the direct wave MIMO SISO TP [Mbps] fd=6hz With delay Radio frequency: GHz Delay [nsec] 11

12 Conclusion I presented an effectiveness of the RF-controlled spatial fading emulator with regard to both antenna measurment and handset evaluation. For antenna evaluation, the agreement between MIMO characteristics in the propagation test and OTA testing reveals that the emulator is effective in evaluating handset antennas. With respect to handset evaluation, we have made a start of the MIMO throughput measurement using the emulator. 12