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A Study on Improved Algorithm for MIMO Antenna Measurement

Master Thesis. A Study on Improved Algorithm for MIMO Antenna Measurement. Thanh-Ngon Tran Supervisor: Professor Kyeong-Sik Min. SRANT Laboratory, Korea Maritime University November, 2006. Contents. Chapter 1: Introduction

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A Study on Improved Algorithm for MIMO Antenna Measurement

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  1. Master Thesis A Study on Improved Algorithm for MIMO Antenna Measurement Thanh-Ngon Tran Supervisor: Professor Kyeong-Sik Min SRANT Laboratory, Korea Maritime University November, 2006

  2. Contents • Chapter 1: Introduction • Chapter 2: Algorithm of antenna measurement software with noise reduction • Chapter 3: Measurement of key parameters of MIMO antenna • Chapter 4: Design of multi-band MIMO test-bed • Chapter 5: Conclusion

  3. Wireless LAN Mobile phone Home/office systems Voice/Data High Data rate Voice Multi-media Cordless phone Introduction (1) Chapter 1 Antenna development vs. Antenna measurement system Channel capacity increase Multiple Antenna Single/Multiple Antenna Single Antenna Single Antenna

  4. Improve single antenna measurement software Apply the improved mea. software for MIMO ant. mea. Design 22 MIMO testbed for MIMO measurement Future works Introduction (2) – The goal and limitation Chapter 1 • The goal: Develop measurement software & system for MIMO antenna & channel measurement. Steps: (1) (2) (3) (…) Gain, 2D/3D pattern, Polarization, w/ Filter algorithm Direct up/down converters, Software structure and algorithm MIMO antenna and channel characterization Diversities, Correlation, Mutual Coupling

  5. Single antenna measurement system Chapter 2

  6. Ref.: Young-Hwan Park, “A study on construction of antenna measurement environment,” Master Thesis, Korea Maritime University, Feb. 2005 Previous Software vs. New Software Chapter 2 • There are two independent programs • Gain • Radiation Pattern • This program is not divided in specific functions • Simple structure • When there are changes, whole program have to be changed • The program can be modified easily when equipment is changed. • 4 measurement functions: gain, 2D and 3D pattern, polarization. • New algorithm for noise reduction

  7. Software structure Software flowchart Software algorithm Chapter 2

  8. TX Ant AUT 4m TX-RX Antenna in anechoic chamber Chapter 2 For experimental measurement: TX Ant.: Horn antenna, 1-18 GHz RX Ant.: Helical antenna, ~ 3 GHz Distance: ~4 meter

  9. Measurement Results with filter algorithm Chapter 2 Signal processing algorithm Original Signal (pattern) Measured by conventional measurement system Filtered Signal (pattern) Measured and processed real-time by noise reduction algorithm

  10. Noise Reduction Algorithm Chapter 2 • Combination of time and space mean filter • Noise in measurement system is Additive White Gaussian Noise (AWGN) • Mean filter is suitable for removing AWGN Measured Power Expected Power Noise Time Mean Filter Space Mean Filter

  11. #2 #3 z #1 #4 110 mm y x 7 mm 75 mm MIMO antenna measurement Chapter 3 This EUT is chosen because it is: • One of MIMO appli-cation. • Elements have differ-ent polarization, pattern, gain, coupling … Measure and evaluate: • Diversities: pattern, polarization. • Pattern correlation. • Mutual coupling. (a) Front view (b) Inside view Metal box, PDA-size with 4 IFA antennas (PDA: Personal Data Assistant)

  12. x x y y z z Gain of antenna elements on x-y plane Gain of antenna elements on x-z plane Gain of antenna elements on y-z plane Pattern (gain) diversity Chapter 3 #3 is the best choice #1 is the best choice #4 is the best choice #2 is the best choice • Maximum gain of EUT antenna elements on three planes is about 6 dBi (y-z plane). • In any direction, there is at least one element with high gain. Difference between the highest and lowest gain is higher than 3 dB at any direction. • Conclusion: This difference of gain pattern shows good gain diversity.

  13. x x x x y y z z Polarization diversity Chapter 3 Element #2, x-y plane XPD = 20dB @ 89o Element #1, x-z plane XPD = 22dB @ 178o Element #3, x-y plane XPD = 20dB @ 268o Element #4, x-z plane XPD = 20dB @ 183o Eco and Ecross are co-polarization and cross-polarization components of E-field, respectively. • Element #1 and #4: linear horizontal polarization. • Element #2 and #3: linear vertical polarization. • Conclusion: Good the polarization diversity.

  14. x x y y Element #3, x-y plane Element #2, x-y plane Pattern Correlation Chapter 3

  15. Mutual Coupling Measurement Chapter 3 EUT MW Receiver & Freq. converter

  16. MIMO Testbed Chapter 4 Block diagram of 22 MIMO testbed • Freq.: 1.8 – 5.8 GHz • Use direct-conversion technique for analog RF circuits • RF analog circuits are coupled with DSP algorithm

  17. Design the wide bandwidth direct down-conversion receivers by: Combine the analog front-end circuit with base-band DSP Freq.: 1.8 – 5.8 GHz 3 Analog front-end Baseband DSP RF LO 1 2 Bandwidth is Wider Q I Power div. Mixer Phase shifter Analog front end circuit is simpler Baseband Amp. RX - Design of Down-converter Chapter 4

  18. 5% amplitude imbalance Conventional bandwidth: 0.25 GHz (5o imbalance) Imbalance parameters Chapter 4

  19. Measured sig. Processed sig. Reference sig. Measured sig. Processed sig. Reference sig. V_I (Volts) V_I (Volts) V_I (Volts) Measured sig. Processed sig. Reference sig. Frequency: 4.0 GHz Amp. imbalance: 1.118 Phase imbalance: -13.25 degree Frequency: 1.8 GHz Amp. imbalance: 0.898 Phase imbalance: -75.74 degree Frequency: 5.6 GHz Amp. imbalance: 1.125 Phase imbalance: 44.50 degree V_Q (Volts) V_Q (Volts) V_Q (Volts) Lissajuos graph of the I and Q signal at 1.8 GHz Lissajuos graph of the I and Q signal at 4.0 GHz Lissajuos graph of the I and Q signal at 5.6 GHz RX - I/Q signals Chapter 4

  20. LO RF Power combiner Q I Mixer Phase shifter Up converter circuit Measurement setup TX - Design of Up-converter Chapter 4 • Analog front-end circuit is coupled with DSP algorithm to compensate the imbalance characteristics of analog circuit (as in down converter). • LO leaky is controlled by bias voltage on MIXER chips.

  21. Leaky signal suppression Chapter 4 Suppressed by controlling amplitude and phase coefficient Suppressed by controlling bias voltage on MIXER chips Spectrum of output signal before and after imbalance compensation

  22. I-Channel: 0.402VDC + 0.142Vac, phase = 0o Q-Channel: 0.308VDC + 0.150Vac, phase = 112.3o I-Channel: 0.239VDC + 0.120Vac, phase = 0o Q-Channel: 0.638VDC + 0.122Vac, phase = 73.9o Spectrum of output signal without I/Q imbalance compensation at 3.0 GHz Spectrum of output signal with I/Q imbalance compensation at 3.0 GHz Spectrum of output signal without I/Q imbalance compensation at 5.0 GHz Spectrum of output signal with I/Q imbalance compensation at 5.0 GHz Measurement results of output spectrum Chapter 4

  23. Conclusion and future study • Development of measurement software & system for MIMO antenna & channel measurement is divided into 3 steps with the good experiments results: • Improve single antenna measurement software: • Gain, 2D/3D pattern, polarization with noise reduction. • Apply the improved measurement software for MIMO antenna measurement: • Diversities, Correlation, Mutual Coupling. • Design 22 MIMO testbed for MIMO measurement. • Direct up/down converter, system design. • Future study: Develop algorithm for MIMO antenna and channel characterization.

  24. THANK YOU FOR YOUR ATTENTION!

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