Hawkeye Hardware Design and Localization Tool

Welcome to Hawkeye hardware design and localization tool. This is the artifact for MobiSys '23, Hawkeye: Hectometer-range Subcentimeter Localization for Large-scale mmWave Backscatter [1]

Cite this tool

Plain Text

Kang Min Bae, Hankyeol Moon, Sung-Min Sohn, and Song Min Kim. 2023. Hawkeye: Hectometer-range Subcentimeter Localization for Large-scale mmWave Backscatter. In Proceedings of the 21st Annual International Conference on Mobile Systems, Applications and Services (MobiSys '23). Association for Computing Machinery, New York, NY, USA, 303–316. https://doi.org/10.1145/3581791.3596869

BibTex

@inproceedings{bae2023hawkeye,
　title={Hawkeye: Hectometer-range Subcentimeter Localization for Large-scale mmWave Backscatter},
　author={Bae, Kang Min and Moon, Hankyeol and Sohn, Sung-Min and Kim, Song Min},
　booktitle={Proceedings of the 21st Annual International Conference on Mobile Systems, Applications and Services},
　pages={303--316},
　year={2023}
}  

The repository consists of two folders. The Hardware folder contains the Hawkeye tag design file, which can be opened using HFSS software. The Software folder contains the Hawkeye super-resolution algorithm file in matlab, with example inputs. The inputs are generated with EVAL-TINYRAD from Analog Devices.

We note that we do not upload the codes provided by Analog Devices, due to possible copyright issues.

Hawkeye Hardware Design

Design Overview

Hawkeye backscatter tag is a planar Van Atta Array (VAA) combined with a power-efficient low-loss FSK modulator using a hybrid coupler. The tag retro-reflects in both azimuth (90° FoV) and elevation (140° FoV). Hawkeye tag is tuned to demonstrate S11 of -10 dB throughout the entire 250 MHz bandwidth, where FSK modulation is performed by the combination of reflective network and low-loss 90° hybrid coupler co-optimized for efficient VAA reflection. The use of the VAA, along with the severe signal attenuation of the mmWave, naturally suppresses the multipath interference. To the best of our knowledge, Hawkeye tag is the first planar VAA mmWave backscatter design with modulation capability.

High-level Operation

The tag retro-reflects the incident signal with FSK modulation, by periodically toggling between two signal paths (with different lengths) on each centrosymmetric antenna pair. The modulator is a combination of hybrid coupler and reflective network that yields a $180^\circ$ phase flip with path switching. Both paths are impedance-matched for low-loss modulation, where this feature applies across all antenna pairs for retro-reflectivity under FSK. In the following, we present details on the tag structure and specifics on our design choices.

Hardware Design Details

(1) Antenna Design
The antenna parameters are optimized to achieves S11 of -10 dB throughout the entire 250 MHz bandwidth (24GHz-24.125GHz). Specifically, patch dimension and edge notch depth (antenna feeding point) is optimized to 50 Ω (TL's impedance).

(2) Modulator Design
Hawkeye modulator uses PIN diode (MADP-000907-14020) whose equivalent circuit is represented in R, L, and C components. The effect of diode is simulated via lumped RLC boundary in HFSS.

(3) VAA Design
To keep the VAA retro-reflectivity, all TLs should induce the same phase shift. To do this, we follows below process. (1) we checked the S21 of TLs first and optimized each TL length as they have equally induced phases. (2) Later, we attached the modulator and optimized the TL lengths and gaps between TLs to compensate for the coupling effect between the modulator and the TLs. (3) Lastly, we combined the antenna with modulator & TL, and checked the retro-reflectivity performance via the Monostatic RCS plot of HFSS, with Incident wave excitation.

Hawkeye Localization Tool

The Hawkeye localization tool consists of two matlab codes: (i) HawkeyeSuperResolution.m is the main file, which takes raw data from EVAL-TINYRAD as input, and outputs the Hawkeye localization result. The code first applies HD-FMCW [2] to the input data, to isolate tag signal from clutter noise. Afterwards, the clutter noise is rejected, followed by Hawkeye super-resolution algorithm. (ii) sincMakePhase.m file provides a function for HawkeyeSuperResolution.m, which is optinally called when applyAdvancedSR is turned on (recommended when tag range < 3 meters).

If you apply our tool in your research, please cite our paper [1]. For troubleshooting, please contact the SMILE LAB (smilelabkaist@gmail.com).

License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Reference

[1] Kang Min Bae, Hankyeol Moon, Sung-Min Sohn, and Song Min Kim. "Hawkeye: Hectometer-range Subcentimeter Localization for Large-scale mmWave Backscatter", MobiSys '23.

[2] Kang Min Bae, Namjo Ahn, Yoon Chae, Parth Pathak, Sung-Min Sohn, and Song Min Kim. "OmniScatter: Extreme Sensitivity mmWave Backscattering using Commodity FMCW Radar", MobiSys '22.