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

SRANT Lab., Korea Maritime University 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

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

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

SRANT Lab., Korea Maritime University 5 Single antenna measurement system Chapter 2

SRANT Lab., Korea Maritime University 6 Previous Software vs. New Software 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 Chapter 2 Ref.: Young-Hwan Park, “A study on construction of antenna measurement environment,” Master Thesis, Korea Maritime University, Feb The program can be modified easily when equipment is changed. 4 measurement functions: gain, 2D and 3D pattern, polarization. New algorithm for noise reduction

SRANT Lab., Korea Maritime University 7 Software algorithm Chapter 2 Software structure Software flowchart

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

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

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

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

SRANT Lab., Korea Maritime University 12 Pattern (gain) diversity Chapter 3 Gain of antenna elements on x-y plane Gain of antenna elements on x-z plane Gain of antenna elements on y-z plane x y z x z y #4 is the best choice #3 is the best choice#1 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.

SRANT Lab., Korea Maritime University 13 Polarization diversity Chapter 3  Element #1 and #4: linear horizontal polarization.  Element #2 and #3: linear vertical polarization.  Conclusion: Good the polarization diversity. Element #1, x-z plane XPD = 178 o Element #4, x-z plane XPD = 183 o Element #2, x-y plane XPD = 89 o Element #3, x-y plane XPD = 268 o E co and E cross are co-polarization and cross-polarization components of E- field, respectively. x y z x x y z x

SRANT Lab., Korea Maritime University 14 Pattern Correlation Elements x-y planex-z planey-z planex-y planex-z planey-z plane #1 and # #1 and # #1 and # #2 and # #2 and # #3 and # Chapter 3 x y x y Element #2, x-y plane Element #3, x-y plane

SRANT Lab., Korea Maritime University 15 Mutual Coupling Measurement Chapter 3 MW Receiver & Freq. converter EUT

SRANT Lab., Korea Maritime University 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

SRANT Lab., Korea Maritime University 17 RX - Design of Down-converter 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 Analog front-end Baseband DSP Bandwidth is Wider Analog front end circuit is simpler LO RF Q Phase shifter Mixer Baseband Amp. Power div. I Chapter 4

SRANT Lab., Korea Maritime University 18 5% amplitude imbalance Imbalance parameters Conventional bandwidth: 0.25 GHz (5 o imbalance) Chapter 4

SRANT Lab., Korea Maritime University 19 RX - I/Q signals Chapter 4 Lissajuos graph of the I and Q signal at 1.8 GHz V_Q (Volts) Measured sig. Processed sig. Reference sig. V_I (Volts) Frequency: 1.8 GHz Amp. imbalance: Phase imbalance: degree Lissajuos graph of the I and Q signal at 4.0 GHz V_Q (Volts) Measured sig. Processed sig. Reference sig. V_I (Volts) Frequency: 4.0 GHz Amp. imbalance: Phase imbalance: degree Lissajuos graph of the I and Q signal at 5.6 GHz V_Q (Volts) Measured sig. Processed sig. Reference sig. V_I (Volts) Frequency: 5.6 GHz Amp. imbalance: Phase imbalance: degree

SRANT Lab., Korea Maritime University 20 TX - Design of Up-converter 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. Measurement setup Up converter circuit LO RF Q Phase shifterMixer Power combiner I Chapter 4

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

SRANT Lab., Korea Maritime University 22 Measurement results of output spectrum 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 I-Channel: 0.402VDC Vac, phase = 0 o Q-Channel: 0.308VDC Vac, phase = o 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 I-Channel: 0.239VDC Vac, phase = 0 o Q-Channel: 0.638VDC Vac, phase = 73.9 o Chapter 4

SRANT Lab., Korea Maritime University 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.

SRANT Lab., Korea Maritime University 24 THANK YOU FOR YOUR ATTENTION!