1. Light 24 GHz Multi-Channel RADAR System Aiding Unmanned Aerial Vehicle Navigation
Soumyaroop Nandi

2. OUTLINE Motivation and Goals Background Basic Concepts Analysis
Applications
Conclusions and Future Work

3. MOTIVATION AND GOALS
Autonomous navigation currently rely on IMU and GPS sensors with Kalman Filtering for tracking.
GPS-denied navigation is based on Visual Odometry/Optical sensors, dependent on illumination condition.
Radar is the alternative; Resolution is independent of the Range distance.
Range, velocity and angle of Non-co-operative targets can be easily computed.
Robust against all weather and light conditions.
SAR images have enhanced resolution in azimuth direction.
Ultralight SENTIRE Radar (58g to 186g, 133.7mmx84.5mmx35.6mm),
mounted on a Micro Aerial Vehicle (MAV), helping its auto navigation.
Fig 1: 24 GHz 2 channel Array Antenna SENTIRE Radar by MST[2]

4. Radar Aided Navigation
BACKGROUND
PROs
Cons
Challenges
Radar Aided Navigation
All time, all weather
Resolution independent of range
Direct measurement of range and velocity
Difficult to interpret with multiple scatterers
Measurements affected by wavelength and relative attitude
Data Association
Sense and Avoid
Direct range, angle and velocity measurements
Trade of between detection range/angular coverage/ resolution/ scan rate/ small RCS/ multiple antennas/ scanning systems
Data Fusion to assist visual based sensors
Imaging
Not affected by obscurants
Image distortions
No intuitive interpretation of images
Motion compensation to perform SAR processing (low performance navigation sensors)

5. BASIC CONCEPTS
Angle of target measured by the use of multi-channel and range is
measured directly.
Real-time 2D scan of vicinity possible.
FMCW radar transmits continuously a frequency modulated
complex signal.
Received echo is mixed with transmitted signal and the output signal
is Beat signal.
Beat signal have Fourier component included in a low-frequency and
relatively short bandwidth.
Each component of Beat signal is directly proportional to the target
range (ratio between propagation velocity & Fig 2: 2D Angular view of the radar showing targets [1]
transmitted signal bandwidth)
Beat signal is the sum of several sine and cosine waves. Number of such waves determine the number of targets, centered at different frequencies.

6. BASIC CONCEPTS
Difficult to analyze FMCW radar data in time domain. Range compression having both magnitude and phase components are arranged in a matrix, range-compressed matrix.
Strongest components of the range compressed beat signals points to the
target.
In FMCW radar, bandwidth of Beat signal is much smaller than the
bandwidth of transmitted signal. So, GHz bandwidth can be easily handled
by MHz sampling frequency.
Simple and cheap hardware requirement.
Patch antenna developed by IMST [1], with one Tx antenna and two Rx antenna separated in azimuth direction along with SENTIRE Radar used.

7. BASIC CONCEPTS
Targets’ Bearing Angle (theta) is calculated [2] using the following
formula:
theta = sin^(-1) ( lambda*phi/(2*pi*L) )
Where, phi is the phase difference between the two receiving
channels, L is the distance between two receiver channels and lambda
is the wavelength.
Phase for each channel is related to measured range.
Bearing estimation is possible in the azimuth direction Fig 3: Geometry for Bearing Angle Estimation[2]
(direction of separation between channels).
Elevation angle can be measured by rotating the radar by 90 deg or installing additional antennas.

8. ANALYSIS Tx Antenna Beam Pattern in Azimuth 58 deg
Tx Antenna Beam Pattern in Elevation
24 deg
Rx Antenna Beam Pattern in Azimuth
70 deg
Rx Antenna Beam Pattern in Elevation
Transmitted Bandwidth
1 GHz
Wavelength
1.25 cm
Frequency Modulation
Linear – Up Sweep
Ramp Duration
5 ms
Sampling Frequency
208.3 KHz
Table 1: Main Parameters of Antenna Pattern
Table 2: Radar Parameters

9. ANALYSIS Project Calculations:
Calculate Range and Velocity of objects with varying RCS
Magnitude and Bearing Angle as a function of time
Calculate Doppler Frequency
Velocity Resolution and Angular Resolution

10. APPLICATION In-flight supervision of radar raw data
Fig 4: Person Detection for security purposes
Fig 5: Collision protection for UAVs and other vehicles
In-flight supervision of radar raw data

11. CONCLUSION AND FUTURE WORK
High resolution imaging with SAR is still difficult to achieve.
Multi-target tracking is possible with offline target identification and tracking.
Triangular frequency modulation and Doppler processing to achieve better radial velocity.
Fig 6: Sensor Fusion with INS, EKF and other sensors [3]
AGL – Height above ground level

12. REFERENCE
W. Simon, T. Klein, and O. Litschke, "Small and light 24 GHz multichannel radar," in Antennas and Propagation Society International Symposium (APSURSI), 2014 IEEE, pp , 6-11 July 2014.
A. F. Scannapieco, A. Renga, G. Fasano and A. Moccia, "Ultralight radar sensor for autonomous operations by micro-UAS," 2016 International Conference on Unmanned Aircraft Systems (ICUAS), Arlington, VA, 2016, pp doi: /ICUAS
Scannapieco, Antonio Fulvio & Renga, Alfredo & Fasano, Giancarmine & Moccia, A. (2017). ULTRALIGHT RADAR FOR SMALL AND MICRO-UAV NAVIGATION. ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. XLII-2/W /isprs-archives-XLII-2-W
EECS 725 notes, Dr. Christopher Allen, University of Kansas

13. Questions