2008 Radio and Wireless Symposium incorporating WAMICON 22 24 January 2008, Orlando, FL. Fiber-fed wireless systems based on remote up-conversion techniques Jae-Young Kim and Woo-Young Choi Dept. of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea Slide 1
Outline 1. Radio over Fiber for 60GHz WLAN 2. Remote up-conversion techniques 3. Optoelectronic mixer based on InP HBT 4. Optically injection-locked self-oscillating optoelectronic mixer (OIL-SOM) based on InP HBT 5. Summary Slide 2
60GHz for Wireless Networks Broadband Wireless Access High-speed Wireless LAN Wireless HD video transmission Wireless Personal Area Network (WPAN) Growing interest in 60GHz - 60GHz as unlicensed band - IEEE 802.15.3C explores 60GHz band for WPAN Slide 3
Fiber-Fed Fed wireless system for wireless networks Building Satellite communication Radio-over-Fiber (RoF) systems - Ultra-wide bandwidth - Low transmission loss - Effective linkage with optical networks Antenna base station Antenna base station Household Central Office Outdoor service Optical fiber Underground shopping mall Slide 4
Fiber-Fed Fed wireless system for wireless networks Optical fiber PCs PDA Notebook Antenna base station HDTV High transmission loss in air - Pico cell topology - Many antenna base stations Key issue - Simple antenna base stations Slide 5
Architectures for Fiber-Fed Fed Wireless Systems Baseband Central station Base station Complex base station Data E O O E MOD IF RF LO IF feeder (Remote up-conversion) Data MOD E O O E IF RF LO Optical MMW Data MOD IF RF E O O E Simple base station LO High-speed photo-detector Slide 6
IF feeder with optical LO distribution Data MOD E O O/E mixer LO Why InP HBT? - Optoelectronic mixing - High optical responsivity - High-speed operation - MMIC-compatibility SOA + EAM - J. S. Seo, etc, IEEE MTT, Feb 2006 InP HEMT O/E mixer - C. S. Choi, etc, IEEE MTT, Nov 2004 InP HBT O/E mixer HBT: Heterojunction Bipolar Transistor Slide 7
InP Heterojunction Bipolar Transistor Optical illumination InP emitter 50nm InGaAs base Absorption region 300nm InGaAs collector Semi-insulating InP substrate Phototransistor internal gain [db] 35 30 25 20 15 10 5 0 Tr-mode PD-mode G int Optical f T = 63GHz -5 -Optical BW 3dB = 1.7GHz -f T = 153GHz, f max = 94GHz 1E8 1E9 1E10 Optical modulation frequency [Hz] Fabricated in NTT Photonics Laboratories, Japan Slide 8
Operation Principles and Characteristics of HBT O/E mixers Slide 9
HBT Optoelectronic Mixer with optical LO λ IF ƒ IF = 500MHz Optical IF ƒ LO = 60GHz InP HBT RF ƒ LO ± ƒ IF 60GHz Amp. λ LO Optical LO Photo-detector + mixer O/E mixer - Optical LO distribution - Elimination of LO in many ABSs - But, low conversion efficiency Slide 10
HBT Self-oscillating optoelectronic Mixer λ IF ƒ IF = 400MHz Optical IF ƒ LO = 30GHz RF ƒ LO ± ƒ IF HBT Oscillator BPF @ 30GHz 60GHz Amp. f IF λ LO Optical LO - High power LO generation - Improved conversion efficiency - Integrated Oscillator also possible Optical injection-locking and Self-oscillating mixing (OIL-SOM) f LO Slide 11
HBT Self-oscillating optoelectronic Mixer λ IF λ LO ƒ IF = 400MHz Optical IF ƒ LO = 30GHz Optical LO - High power LO generation - Improved conversion efficiency - Integrated Oscillator also possible Detected signal [dbm] -10-20 -30-40 -50-60 -70-80 2ƒ LO - ƒ IF 2ƒ LO 60.30 60.35 60.40 60.45 60.50 60.55 Frequency [GHz] 2ƒ LO + ƒ IF (Used 2 nd harmonic for 60GHz applications) Slide 12
HBT MMIC self-oscillating mixer Optical LO 10GHz V C HBT HBT V B V cont1 V cont2 -Low Q value - Wide locking range 10GHz MMIC oscillator Fabricated in NTT Photonics Laboratories, Japan Slide 13
Phase noise reduction by optical injection-locking SSB Phase noise [dbc/hz] -50-60 -70-80 -90-100 -110-120 30GHz Free-running 30GHz Injection-locked 10GHz optical LO -130 10k 100k 1M 10M Presented in IMS 2007 Frequency offset [Hz] Slide 14
Thermal variation of oscillation frequency Central Station Antenna Base Station Free-running Oscillation frequency [GHz] 10.740 10.735 10.730 10.725 10.720 ~ 191 KHz/degree 18 MHz 94.2 10.715 280 300 320 340 360 380 400 Temperature [ K ] - The self-oscillating frequency varies with temperature IEEE MTT, Dec, 2007 Slide 15
Wide optical injection-locking range Central Station 1k For 10GHz fundamental LO Antenna Base Station Free-running Locking Range [MHz] 100 10 1 ~ 1.5GHz Locking range at 6dBm optical LO -8-6 -4-2 0 2 4 6 Optical LO power [dbm] - Wide locking range for maintaining injection-locking in ABS Slide 16
Link demonstrations using O/E mixers Central station Base station Optical IF 60GHz Optical LO HBT O/E mixer 60GHz Bi-directional link Optical IF 30GHz Optical LO 30GHz Hybrid Self-oscillating mixer (2 nd harmonic operation) 60GHz Downlink Optical IF 10GHz Optical LO 10GHz MMIC Self-oscillating mixer (3 rd harmonic operation) 30GHz Bi-directional link Slide 17
60GHz Bi-directional link using HBT O/E Mixer Central station Base station Optical IF 60GHz Optical LO HBT O/E mixer 60GHz Bi-directional link Slide 18
60GHz bi-directional links based on HBT Central Station Antenna Base Station PD Uplink DFB LD 2GHz Optical IF/Data ƒ IF =1.25GHz IF Amp. 63.25GHz λ IF Diplexer PA 62GHz Optical LO λ LO Downlink LNA InP HBT O/E up/down mixer 60GHz IEEE PTL, Dec, 2005 Slide 19
Downlink transmission (Up-conversion) Central Station Antenna Base Station Optical IF/Data (16QAM 20Mbps) ƒ IF =1.25GHz λ IF BPF @ 63.5GHz PA 63.25GHz 62GHz Optical LO λ LO Downlink InP HBT O/E mixer Slide 20
Downlink transmission results Frequency up-converted spectrum Eye-diagram and constellation 16QAM constellation Eye diagram Frequency down-conversion LPF Vector Signal Analyzer EVM =4.53% Slide 21
Uplink transmission (Down-conversion) Central Station Antenna Base Station 2GHz IF Amp. Diplexer Optical LO 62GHz λ LO Downlink LNA InP HBT O/E up/down mixer 60GHz (16QAM 20Mbps) Slide 22
Uplink transmission results Frequency down-converted spectrum Eye-diagram and constellation 16QAM constellation Eye diagram LPF Vector Signal Analyzer EVM =4.67% Slide 23
Resulting EVM VS optical LO power Downlink Uplink Error Vector Magnitude (EVM), [%] 12 11 10 9 8 7 6 5 4 3 EVM Optical IF power = -2dBm -3-2 -1 0 1 2 Error Vector Magnitude (EVM), [%] 12 11 10 9 8 7 6 5 EVM 4-3 -2-1 0 1 2 3 Optical LO power [dbm] Optical LO power [dbm] Slide 24
60GHz Downlink using HBT Self-oscillating Mixer Central station Base station Optical IF 30GHz Optical LO 30GHz Hybrid Self-oscillating mixer (2 nd harmonic operation) 60GHz Downlink Slide 25
Hybrid OIL-SOM for 60GHz downlink Central Station Antenna Base Station Optical IF/Data ƒ IF =0.42GHz BPF @ 60GHz 60GHz (16QAM 20Mbps) Optical LO λ IF 30.21GHz λ LO Downlink 10dB coupler 30.21GHz OIL-SOM BPF @ 30GHz (2 nd harmonic for 60GHz applications) Presented in OFC 2006 Slide 26
Frequency up-converted spectrum Downlink transmission results Frequency down-conversion LPF Slide 27
Resulting constellation and EVMs 16QAM constellation Eye diagram EVM =4.74% Optical LO power = -3dBm Error Vector Magnitude (EVM) [%] 10 9 8 7 6 5 4 10dB -12-10 -8-6 -4-2 0 Optical LO power [dbm] - Insensitive link performance on optical LO power Slide 28
30GHz Bi-directional link using HBT Self-oscillating Mixer Central station Base station Optical IF 10GHz Optical LO 10GHz MMIC Self-oscillating mixer (3 rd harmonic operation) 30GHz Bi-directional link Slide 29
MMIC OIL-SOM for 30GHz bi-directional link Central Station Antenna Base Station PD Uplink DFB LD 2.2GHz Optical IF/Data ƒ IF =1.4GHz Bias-T IF Amp. 31GHz Diplexer PA λ IF HBT 10.8GHz Optical LO Downlink HBT V cont1 V cont2 30.2GHz λ LO 10GHz MMIC oscillator Slide 30
Resulting constellation and eye-diagram Downlink Uplink 32QAM constellation 32QAM constellation Eye diagram Eye diagram EVM =4.34% Optical LO power = 0dBm Optical IF power = 0dBm EVM =5.47% Optical LO power = 0dBm Slide 31
Resulting EVM VS optical LO power Downlink Uplink Error Vector Magnitude (EVM), [%] 12 10 8 6 4 2 Optical IF power = 0dBm 0-6 -4-2 0 2 4 6 Optical LO power [dbm] Error Vector Magnitude (EVM), [%] 12 10 8 6 4 2 0 Uplink RF power = -10dBm -2-1 0 1 2 3 4 Optical LO power [dbm] Slide 32
Summary InP HBT/oscillator-based optoelectronic mixers - For effective fiber-fed wireless systems - Support simple base station architecture - Possibility of integrated antenna base station with RF circuits - Effective frequency conversion with low power optical LO Acknowledgement - Dr. Kamitsuna at NTT Photonics Laboratory, Japan - Dr. Chang-Soon Choi (Presently at IHP, Germany) Q & A Slide 33