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1 / 32 Integrated photonic beamformer employing continuously tunable ring resonator-based delays in CMOS-compatible LPCVD waveguide technology C. G. H.

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Presentation on theme: "1 / 32 Integrated photonic beamformer employing continuously tunable ring resonator-based delays in CMOS-compatible LPCVD waveguide technology C. G. H."— Presentation transcript:

1 1 / 32 Integrated photonic beamformer employing continuously tunable ring resonator-based delays in CMOS-compatible LPCVD waveguide technology C. G. H. Roeloffzen* a, A. Meijerink a, L. Zhuang a, D. A. I. Marpaung a, R. G. Heideman b, A. Leinse b, M. Hoekman b, W. van Etten a. a University of Twente, Faculty of Electrical Engineering, Mathematics and Computer Science, Telecommunication Engineering Group, P.O. Box 217, 7500 AE Enschede, The Netherlands b LioniX B.V., P.O. Box 456, 7500 AH Enschede, The Netherlands

2 2 / 30MWP » MWP in PAAs » SMART » Conclusions » Questions Contents 1.Introduction; 2.System overview & requirements; 3.Optical beamformer - Ring resonator-based delays; - OBFN structure; - Chip fabrication; - OBFN control block; - E/O & O/E conversion; - System performance. 4.Conclusions

3 3 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Introduction: What is beamforming Smart Antenna systems: Switched beam: finite number of fixed predefined patterns Adaptive array: Infinite number of (real time) adjustable patterns

4 4 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Introduction: Smart antenna Smart Antenna systems: Using a variety of new signal-processing algorithms, the adaptive system takes advantage of its ability to effectively locate and track various types of signals to dynamically minimize interference and maximize intended signal reception. Beamforming: spatial filtering

5 5 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Beamforming: Uniform line array x0(t)x0(t) d x1(t)x1(t) x2(t)x2(t) xM(t)xM(t) s(t)s(t) (M-1)

6 6 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Beamforminh: Delay-sum Timed array + (t-[M-1]T) (t-[M-2]T) (t) w0w0 x w1w1 x w M-1 x When T=, the channels are all time aligned w m are beamformer weights Gain in direction is w m. Less in other directions due to incoherent addition.

7 7 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Beamforming: Similar to FIR filter br + w0w0 x w1w1 x w M-1 x Let T=0 (broadside) Represent signal delay across array as a delay line Sample: x[n]=x 0 (nT) Looks like an FIR filter! x[n]*w[n] Design w with FIR methods (t- ) y(t)y(t)

8 8 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Beamforming: Narrowband Narrowband assumption: Let s(t) be bandpass with BW << c / (M-1)d Hz. This means the phase difference between upper and lower band edges for propagation across the entire array is small, e.g. < /10 radian. Most communication signals fit this model. If signal is not narrowband, bandpass filter it and build a new beamformer for each subband. Sample the array x[n]=x(nT), We can now eliminate time delays and use complex weights, w= [w 0, …, w M-1 ], to both steer (phase align) and weight (control beam shape)

9 9 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Beamforming: Narrowband phased array + w0w0 x w1w1 x w M-1 x m = amplitude weight for sensor m, f 0 = bandpass center frequency, Hz, 0 = direction of max response x0[n]x0[n] x1[n]x1[n] x M-1 [n]

10 10 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Beamforming: FFT implementation Suppose you want to for many beams at once, in different directions. If beam k steered to k, has strongest signal, we assume sources is in that direction.

11 11 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Beamforming: FFT implementation many beams at once x0[n]x0[n] x1[n]x1[n] x M-1 [n] Amplitude Taper (multiply by ) FFT y 0 [n] y 1 [n] y (M-1) [n]

12 12 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Beamforming: Examples Beamforming: Electronic Digital Optical

13 13 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Examples: Electronic beamforming SiGe H. Hashemi, IEEE Communications magazine, Sept 2008

14 14 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Examples: Electronic beamforming CMOS

15 15 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Examples: Electronic beamforming MMIC (CMOS & SiGe) + very small chip + TTD & phase shifters - Switched delay + Large bandwidth + low power consumption - Large coupling between channels

16 16 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Examples: Digital beamforming Digital beamforming:

17 17 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Examples: Digital beamforming Frequency domain beamforming Narrowband decomposition

18 18 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Examples: Digital beamforming Digital beamforming: +Easy implementation of time delays - Multiple data converters required - Large sampling rate - Large number of bits (large dynamic range) - Large power consumption

19 19 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Examples: Optical beamforming Optical beamforming: +Easy

20 20 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Int: aose Smart

21 21 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Introduction: aim and purpose Aim: Development of a novel K u -band antenna for airborne reception of satellite signals Purpose: Live weather reports; High-speed Internet access; Live television through Digital Video Broadcasting via satellite (DVB-s), using a broadband conformal phased array

22 22 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 1. Introduction: specific targets Specific targets: Conformal phased array structure definition; Broadband stacked patch antenna elements; Broadband integrated optical beamformer based on optical ring resonators in CMOS-compatible waveguide technology; Experimental demonstrator.

23 23 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 2. System overview & requirements beamformer Antenna array RF front-end to receiver(s) Frequency range:10.7 – GHz (K u band) Polarization:2 linear (H/V) Scan angle: -60 to +60 degrees Gain:> 32 dB Selectivity:<< 2 degrees No. elements:~1600 Element spacing:~ /2 (~1.5 cm, or ~50 ps) Maximum delay:~2 ns Delay compensation by phase shifters? beam squint at outer frequencies! (Broadband) time delay compensation required ! 40x40 Continuous delay tuning required ! gain beam width scan angle optical with amplitude tapering 8x8 1 8x1

24 24 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: overview OBFN chip Antenna elements RF front-end to receiver(s) E/OO/E ?? tunable broadband delays & amplitude weights. ? control block antenna viewing angle plane position & angle feedback loop

25 25 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: ORR-based delays f Group delay Phase Single ring resonator: T : Round trip time; : Power coupling coefficient; : Additional phase. Periodic transfer function; Flat magnitude response. Phase transition around resonance frequency; Bell-shaped group delay response; Trade-off: delay vs. bandwidth f

26 26 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: ORR-based delays Cascaded ring resonators: Rippled group delay response; Enhanced bandwidth; Trade-off: delay vs. bandwidth vs. delay ripple vs. no. rings; ripple bandwidth f Group delay Or in other words: for given delay ripple requirements: Required no. rings is roughly proportional to product of required optical bandwidth and maximum delay

27 27 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: 8x1 OBFN 8x1 Optical beam forming network (OBFN) 8 inputs with tunable delays 1 output combining network with tunable combiners (for amplitude tapering) 12 rings 7 combiners 31 tuning elements

28 28 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: chip fabrication Fabrication process of TriPleX Technology

29 29 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: chip fabrication TriPleX TM results Group birefringence (B g ) Channel attenuation (dB/cm) Polarization dependent loss (PDL, in dB) Insertion loss (IL) without spot size converter (dB) 1× × ,3 1 : chip length 3 cm 2 : here, small core fibers were used (MFD of 3.5 µm) 3 : minimal bend radius ~400 µm

30 30 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: 8x1 OBFN chip 4.85 cm x 0.95 cm 1 cm Heater bondpad TriPleX Technology Single-chip 8x1 OBFN realized in CMOS-compatible optical waveguide technology

31 31 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: OBFN control block beam angle delays + amplitudes chip parameters ( i s and i s) heater voltages DA conversion & amplification ARM7 microprocessor

32 32 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: OBFN measurements OBFN Measurement results 1 ns ~ 30 cm delay distance in vacuum L. Zhuang et al., IEEE Photonics Technology Letters, vol. 19, no. 15, Aug. 2007

33 33 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion OBFN electrical » opticaloptical » electrical RF front-end LNA TIA DM laser chirp! E/O and O/E conversions? low optical bandwidth; high linearity; low noise photo- diode

34 34 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion OBFN electrical » opticaloptical » electrical RF front-end LNA TIA CW laser beat noise! mod. E/O and O/E conversions? low optical bandwidth; high linearity; low noise photo- diode

35 35 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion OBFN electrical » opticaloptical » electrical RF front-end LNA TIA mod. CW laser E/O and O/E conversions? low optical bandwidth; high linearity; low noise photo- diode

36 36 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion mod. OBFN RF front-end LNA spectrum frequency TIA electrical » opticaloptical » electrical CW laser 10.7 GHz GHz2 x = 25.5 GHz photo- diode

37 37 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion mod. OBFN RF front-end LNALNB spectrum frequency TIA electrical » opticaloptical » electrical CW laser 2 x 2.15 = 4.3 GHz 950 MHz 2150 MHz photo- diode

38 38 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion mod. OBFN RF front-end filter LNB spectrum frequency TIA single-sideband modulation with suppressed carrier (SSB-SC) electrical » opticaloptical » electrical CW laser 1.2 GHz SSB-SC Balanced optical detection: cancels individual intensity terms; mixing term remains; reduces laser intensity noise; enhances dynamic range. Implementation of optical SSB modulation? 1.Optical heterodyning; 2.Phase shift method; 3.Filter-based method. photo- diode

39 39 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion mod. OBFN RF front-end filter LNB spectrum frequency TIA single-sideband modulation with suppressed carrier (SSB-SC) electrical » opticaloptical » electrical CW laser 1.2 GHz Filter requirements: Broad pass band and stop band (1.2 GHz); 1.9 GHz guard band; High stop band suppression; Low pass band ripple and dispersion; Low loss; Compact; Same technology as OBFN. 1 chip !

40 40 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion MZI + Ring 5 mm Optical sideband filter chip in the same technology as the OBFN

41 41 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion Measured filter response 20 GHz14 GHz 3 GHz BandwidthSuppression Tradeoff 25 dB FSR 40 GHz

42 42 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion Spectrum measurement of modulated optical signal Optical heterodyning technique: f f f f f1f1 f f1f1 f2f2 MZMOSBFSA fiber coupler RF f f 1 – f 2 f f2f2

43 43 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion Spectrum measurement of modulated optical signal Measured filter response, and measured spectrum of modulated optical signal, with and without sideband-filtering

44 44 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion RF phase response measurements RF input 1-2 GHz RF output Measured RF phase response of one beamformer channel, for different delay values.

45 45 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: E/O and O/E conversion Signal combination measurements CH 1 CH 2 CH 3 CH 4 Output RF input 0-1 GHz Measured output RF power of beamformer with intensity modulation and direct detection, for - 1 channel, - 2 combined channels, - 4 combined channels

46 46 / 46MWP » MWP in PAAs » SMART » Conclusions » Questions » 3. Optical beamformer: Conclusions Conclusions A novel squint-free, continuously tunable beamformer mechanism for a phased array antenna system has been described and partly demonstrated. It is based on filter-based optical SSB-SC modulation, and ORR-based OBFN, and balanced coherent detection. This scheme minimizes the bandwidth requirements on OBFN and enhances the dynamic range. Different measurements on optical beamformer chip successfully verify the feasibility of the proposed system.


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