OPTICAL BEAMFORMING

1. ‫فاللهم‬
‫إنى‬
‫التدبير‬ ‫أحسن‬ ‫ال‬ ‫فأنا‬ ‫امرى‬ ‫لي‬ ‫ودبر‬ ‫وكيل‬ ‫خير‬ ‫فأنت‬ ‫أمرى‬ ‫وكلتك‬
” Optical Advanced Hybrid
phase shift approach for
RF beamforming and 5G
wideband radar
Presented By:
YOSRA Bouchoucha
PhD student
SysCom Laboratory, National Engineering School of Tunis (ENIT) University
of Tunis El Manar, Tunis, Tunisia

2. Outline
I. General objective
II. Objectives and Scopes
III.General Background
IV.Specification & requirements
V. Simulations
VI.Planning & Strategy
VII.Conclusion & perspectives
2
22/07/2023
The objectives of the study • The
background • The research
questions • Methods • Results •
Conclusions and
recommendations

3. I. GENEAL OBJECTIVE
Implementation of a complete Beamforming Network
BFN based on Hybrid Integrated Beamforming
approaches for Millimeter Wave Communication for
RF beamforming and wideband radar Applications
• Requirement of 5G?
High Throughput To The Users.
Better Efficiency In Resource Allocation And Power Consumption.
More extended use of the frequency spectrum
3
22/07/2023

4. II. Objectives and Scopes
 The main purpose of this comparative study paper is to discuss the state-of-the-art research on the most
advantageous types of Phased shifted antenna array techniques
• Phased-shifted antenna arrays are commonly used in radar and communication systems.
• Beam squint is a phenomenon where the direction of the beam shifts with varying frequencies, leading to
reduced performance and accuracy of the antenna array.
• Time delay techniques are used to introduce phase shifts between the elements of the antenna array, which can
mitigate beam squint.
• RF photonics is one technology that can be used to implement time delay techniques.
• A hybrid phase shift beamforming technique has been proposed, which combines True Time Delay (TTD) and
Phase Shift (PS) techniques to overcome the limitations of beam squint over wide bandwidths.
• The proposed hybrid phase shift beamforming technique is well-suited for high bit-rate 5G communications and
wideband radar applications.
• By mitigating beam squint, this technique can improve the accuracy and sensitivity of radar systems and increase
the system's bandwidth.
Overall, phased shifted antenna arrays and the hybrid phase shift beamforming technique offer a powerful approach
to improving the performance and accuracy of radar and communication systems.
22/07/2023 4

5. III.General Background
a. Concept of beamforming
Beamforming (BF) is a signal processing technique used in antenna arrays to steer the direction of
electromagnetic or acoustic waves.
The goal of BF is to focus the energy of the waves in a specific direction and minimize interference from
other directions.
BF adjusts the relative phase and amplitude of signals received or transmitted by each antenna element in
the array, allowing waves from each element to combine constructively in the desired direction while
canceling out waves from other directions.
There are two main types of BF: analog and digital.
Analog beamforming uses phase shifters and attenuators to adjust the signals in the analog domain.
Digital beamforming uses digital signal processing techniques to adjust the signals in the digital domain.
BF has applications in wireless communication, radar systems, sonar, and medical imaging.
BF allows for improved signal quality, increased range, and better interference rejection, making it an
essential technique for many modern technologies.
22/07/2023 5

6. b. Beamforming Techniques
• In general, beam-forming (BF) can be implemented following
two possible approaches: true-time delay (TTD) or phase
shift (PS).
• PS is suitable for small bandwidth but it has the main
limitation of beam squint.
If the number of array elements (NAE) is small , the effect of squint
can be tolerable.
• TTD techniques present the advantage of totally avoiding the beam
squint effect, since a real time delay is introduced between the signals
feeding the PAA elements.
22/07/2023 6

7. A. Equations OF Time-delay Beam steering
• Szolnok's paper is demonstrated that the array factor of a uniformly spaced linear array
is:
• Expression for the array Factor of an array steered with phase shifters.
• The resulting expression provides the amplitude and phase of the radiation pattern
and is dependent on the steering angle and element spacing.
7
• Expression for the array Factor of an array steered with True Time delay
• The resulting expression provides the amplitude and phase of the radiation pattern of
the array and is dependent on the steering angle, element spacing, and the true time
delays applied to each element.

8. Plot for Beamforming using the Phase shift with different frequency
8
Practical time delay circuits do not have a perfectly linear phase-frequency characteristic. When these
delay circuits are applied in a phased-array system, this frequency dependency shows up as a
frequency-dependent beam direction (“beam squinting”).
22/07/2023

9. IV. Motivations
Beam Squint (Bs) in words, means that an antenna pattern points to
θ0+Δθ at frequency f0+Δf instead of θ0, which was the pointing
direction at frequency f0.
• Reduction of the gain
• Limitation of bandwidth in phased array antenna in wideband
systems…
22/07/2023 9

10. Beam Squint Effects
Phased-array antenna systems have wide range of applications for
instance in radar, imaging ,sensors, and communication systems.
• The design of phased array systems is challenging, particularly when
we require a wide band of operation .
• A significant phenomenon that can limit bandwidth in phased array
antenna systems is beam squinting (Bs), for example the altering of
the beam direction as a function of the operating frequency.
• However, It can limit the bandwidth in phased array antenna systems
and may affect uniform linear arrays (ULA) characteristics.
• In fact, as bandwidth increases, beam squint increases too .
22/07/2023 10

11. A. Why we need an hybrid beamforming?
The solution for beam-squint is using TTD instead of PAAs because the TTD is
working with frequency-dependent constant time delay.
Large antenna arrays need TTD circuits that have a large total delay amount.
we suggest hybrid beamforming (PAAs + TTDs) architecture that will cover wide
bandwidth and large array size.
The proposed hybrid structure provides not only high resolution (resolution of
PAAs + resolution of TTD) but also a large total delay (due to analog TTD).
11
22/07/2023

12. • B. Electronic versus-optical Phase shifter
• BF can be realized following two possible approaches, namely true-time delay (TTD) or
phase shift (PS).
• Beamforming (BF) can be realized through the true-time delay (TTD) or phase shift (PS).
• Photonics-assisted BF for microwave and mm-wave signals using PICs in SOI technology.
• TTD can be electronically implemented through switched delay lines or MMICs, but they
have limitations such as limited bandwidth and operation frequency range, low power
handling, and narrow scanning angles.
• Photonics offer advantages such as immunity to electromagnetic interferences, broadband
operation, high phase accuracy, and fast response time.
• PICs are the most promising approach for practical MWP-based PS implementation due to
increased stability, minimized size and weight, and low operating power.
• An optical beamformer is a promising solution for antenna pointing accuracy, low losses,
reduced power consumption, and small size, but research is needed to control delays.
• Photonics can provide promising solutions to meet the requirements and potentially reduce
the cost of BFN elements through photonic integration.
• .
22/07/2023 12

13. V. A Comparison Between RF And Photonic Phase Shifter
• TABLE I reports the comparison between the photonic integrated OPS and classical RF phase shifters,
available on the market from different companies.
• Fundamental parameters like number of elements, BW, PS range, PS resolution, PS error, gain, maximum
power consumption, OP1, IIP3, switching time are considered [1].
• As shown in Table I, the proposed OPS exhibits better performance than the average of the RF devices,
especially in terms of PS range, error, power consumption, and switching time. The power loss, calculated
as 28 dB RF-equivalent loss, but can be possibly reduced to 20 dB, by reducing the coupling loss [1].
22/07/2023 13
Kratos 7928A Analog Devices
HMC247
RF-Lambda
RFPSHT
MiteqDSP-0618-
360-5-5.6
Photonic PS
BW 6-18 5-18 6-18 6-18 10-16
36-42
62-68
………
PS range [°] 0-360 0-400 0-360 0-360 0-475
PS resolution [°] 1.4 Continuous 5.625 5.6 Continuous
PS error[°] ±15 n/a ±15 3 <2
Max Insertion Loss [dB]
Max Power Consumption[W]
12 12 12 12 28 dB
Switching Time [ns]
Analog/Digital
5OO 20 100 20 <1
Digital
(8bit)
Analog Digital
(6 bit)
Digital
(6 bit)
Analog

14. II. Problems with current systems & The
Proposed Architecture
• For beam-forming, conventionally phase delays are implemented in the electrical domain using
digital /analong schemes.
• Electronics based beamforming have following limitations:
Time delay inaccuracy
Limited Signal bandwidth
 High insertion loss
 Physical size and weight, electromagnetic interference
High power consumption (DC)
High cost
Limited or no Frequency Agility
Proposed architecture
the implementation of high-performance beamforming networks in the optical domain based on
microwave photonics technology have been proposed as a powerful alternative
14
22/07/2023

15. III. Specification &Requirements
Frequency range for 5G range for EU: 24,5-27,5 GHz
The freq operation range for the antenna arrays:27 GHz
the characteristics of the antenna arrays:
Number of radiators 10*10=100 Array Element
Spacing (also imposed by freq. range)= lambda/2
Size :
The size Antenna should be minimum =lambda/4
Size of 10 Array Antenna=(10*(lambda/4)+(9*lambda/2))
Applications:
This kind of array can only work in indoor applications
Application can be user specific beam steering machine to machine,MIMO communication ,
applications for beam steering in 5G,Radar applications
22/07/2023 15

16. a. Proposed Methodology
• Block chain of Advanced Beamforming
16
Laser
Source
MZM
Splitter
𝑇𝑇𝐷 1
𝑇𝑇𝐷 2
𝑇𝑇𝐷 3
𝑇𝑇𝐷 35
PS
RF
DC
…
…
……
…
…
…
…
MIMO
Arrayed
PD
22/07/2023
1.MZM to modulate
a laser with an RF
signal
2.An hybrid beam
former is applied to
give the PS.
3.And then ,give to
antenna
4. For each antenna
we need an hybrid
beam former
Optical HBF

17. a. Proposed Methodology
• The Main idea
• The proposed system consists of a TTD and PS based phase shift.
• The TTD section provides discrete phase shift with a step size of 10⁰,
• while the one PS section can provide a phase shift of 0-10⁰.
• The TTD section contains 35 paths each with an increment of 10⁰ thus providing the maximum
phase shift of 350⁰.
• there by the complete hybrid system can provide 2pi PS.
• The TTD section and PS sections are connected in series.
22/07/2023 17

18. PROPOSED SOLUTION
• The schematic structure and the operation principle of the proposed MWP-PS are illustrated in
the block chain.
• The core element of the architecture, highlighted in the figure, comprises an optical Hybrid phase
shifter (OHPS), a Laser source (LS), Modulator(MZM), and a photodiode (PD).
• At the input of the circuit, the microwave signal to be phase-shifted, which is considered to show
a given power spectral density around the carrier frequency fRF, drives a single-sideband electro-
optic modulator (SSB-EOM) to generate a sideband centered at the optical frequency νsb, spaced
by fRF from the optical carrier at frequency νc provided by a laser source (LS).
• The hybrid approach benefits from the best of both worlds i.e. TTD and PS-based systems.
• The operation of the scheme of the MWP-HPS relies on an optical domain.
22/07/2023 18

19. Expected Results
• As mentioned earlier, the TTD and PS based beamforming systems have their limitations namely large size, higher cost,
beam squint and limited bandwidth tunability. For the mmWave communication, a hybrid approach is proposed here.
• As we know from previous section, TTD approach provides a frequency dependent phase shift with no beam squint. On the
other hand, the minimum resolution of phase shift is dependent linearly on number of paths/waveguides. For obtaining a
phase resolution of 1⁰, 360 paths are required.
• This approach is costly as it requires a larger area on the Photonic Integrated Circuit (PIC).
• Phase shift based approach implemented using ring resonators and PN junctions, can provide a higher degree of phase
resolution but as the phase shift is independent of wavelength, it creates beam squint for large bandwidth signals (as required
by 5G).
• Thus, we propose a hybrid approach which benefits from TTD as well as PS.
• The proposed system consists of a TTD and PS based phase shift. The TTD section provides discrete phase shift with a step
size of 10⁰, while the one PS section can provide a phase shift of 0-10⁰.
• The TTD section contains 35 paths each with an increment of 10⁰ thus providing the maximum phase shift of 350⁰.
• The PS section will provide the maximum phase shift of 10⁰ and there by the complete hybrid system can provide 2pi phase
shift.
• The TTD section and PS sections are connected in series. The required phase shift is divided into two parts i.e. 1) Decimal
part and 2) Integer part. The decimal part is the value of phase shift which is divisible by 10.
22/07/2023 19

20. VII. Conclusion &Perspectives
• In order to get a system with Maximum of resolution(360°) minimal
beam squint , larger bandwidth and smaller foot print as compared to
TTD .
• we proposed an Integrated hybrid beamforming system to profit from
the advantages of two worlds :
1. TTD based on Optical Ring Resonator ORR for large steps.
2. Ps based on PN junction for small steps .
20
22/07/2023

21. •THANK YOU FOR YOUR
ATTENTION
21
22/07/2023

22. REFERENCES
[1] J. Capmany and D. Novak, “Microwave photonics combines two worlds,” Nature Photonics, vol. 1, pp. 319–330, 2007.
[2] R. Esman, M. Monsma, J. Dexter, and D. Cooper, “Microwave true timedelay modulator using fibre-optic dispersion,” Electronics Letters, vol. 28, pp. 1905 –1908, sept. 1992.
[3] N. A. Riza and S. Sumriddetchkajorn, “Micromechanics-based wavelength-sensitive photonic beam control architectures and applications,” Appl. Opt., vol. 39, pp. 919–932, Feb 2000.
[4] Q. Chang, Q. Li, Z. Zhang, M. Qiu, T. Ye, and Y. Su, “A tunable broadband photonic RF phase shifter based on a silicon microring resonator,” IEEE Photonics Technology Letters, vol. 21, no. 1, pp. 60–
62,
[5] M. A. Foster, J. S. Levy, O. Kuzucu, K. Saha, M. Lipson, and A. L. Gaeta, “Silicon-based monolithic optical frequency comb source,” Opt. Express, vol. 19, pp. 14233–14239, Jul 2011.
[6] A. Osseiran, J.F. Monserrat, and P. Marsch, “5G Mobile and Wireless Communications Technology”, Cambridge University Press, June 2016, ISBN: 9781107130098.
[7] L. Zhuang, C.G.H. Roeloffzen, A. Mei
jerink, M. Burla, D.A.I. Marpaung, A. Leinse, M. Hoekman, R.G. Heideman, and W. van Etten, “Novel ring resonator-based integrated photonic beamformer for broadband phased array receive antennas-Part
II: Experimental prototype”, J. Lightwave Technol., 28 (1), 2010, pp. 19-31.
[8] D.B. Adams, and C.K. Madsen, “A Novel Broadband Photonic RF Phase Shifter”, J. Lightwave Technol., 26 (15), 2008, pp. 2712-2717.
[9] M. Longbrake, “True time-delay beamsteering for radar”, NAECON 2012, 25-27 July 2012.
B. Vidal, M.A. Piqueras, and J. Martí, “Multibeam photonic beam-former based on optical filters”, Electron. Lett., vol. 42, no. 17, pp. 980-981, Aug. 2006
[10] L. Yaron, R. Rotman, Sh. Zach, and M. Tur, “Photonic beamformer receiver with multiple beam capabilities”, IEEE Photonics Technology Letters 22 (23), 2010, pp. 1723-1725.
[11] P. Ghelfi, F. Laghezza, F. Scotti, G. Serafino, S. Pinna, and A. Bogoni, “Photonic generation and independent steering of multiple RF signals for software defined radars”, Opt. Expr., 21 (19), 2013, pp.
22905-22910.
[12] F. Falconi, C. Porzi, S. Pinna, V. Sorianello, G. Serafino, M. Puleri, A. D’Errico, M. Romagnoli, A. Bogoni, and P. Ghelfi, "Fast and Linear Photonic Integrated Microwave Phase-Shifter for 5G Beam-
Steering Applications," in Optical Fiber Communication Conference, OSA Technical Digest (online) (Optical Society of America, 2018), paper M2G.4.
[13] G. Serafino, C. Porzi, M. Sans, F. Falconi, S. Pinna, V. Sorianello, J. Mitchell, M. Romagnoli, A. Bogoni, and P. Ghelfi, "Fast and Broadband SOI Photonic Integrated Microwave Phase Shifter," in
Conference on Lasers and Electro-Optics, OSA Technical Digest (online) (Optical Society of America, 2018), paper JTh3D.3.
22