I. INTRODUCTION

II. CURRENT AND FUTURE AERIAL THREATS AND THEIR CHALLENGING FEATURES
A. Current and Future Aerial Threats
B. Challenges from Physical and Motion Characteristics of UAVs
C. Challenges from Multiple UAVs

III. ELECTROMAGNETIC WAVES INTERACTION WITH THE AERIAL VEHICLES AND SURROUNDINGS
A. Physical Characteristics
B. Motion Characteristics
C. Clutter
D. Terrain Effects
E. Atmospheric Effects

IV. RADAR TRANSMISSION AND RECEPTION
A. Transmit Power
B. Types of Sounding Signals
C. Pulse Width and Duty Cycle
D. Signal Processing Techniques
E. Motion Filtering
F. Antenna Type and Polarization
G. Frequency and Bandwidth
H. Range and Angular Resolution

V. DETECTION AND RANGING USING RADAR SYSTEMS
A. Detection Using Radar Systems
B. Search Radars for Aerial Vehicle Detection
C. Detection Using Mechanically, and Electronically Scanned Platforms
D. Ranging Using Radar Systems

VI. TRACKING AND CLASSIFICATION OF AERIAL THREATS USING RADAR SYSTEMS
A. Tracking of Aerial Vehicles Using Radar Systems
B. Trajectory Estimation of Aerial Vehicles Using Radar Systems
C. Classification of Aerial Vehicles Using Radar Systems
D. Classification Using Micro-Doppler Radar Signatures

VII. TYPES OF RADAR SYSTEMS
A. Conventional Radar Systems
B. Miscellaneous Types of Radar Systems
C. Airborne Radar Systems
D. Radars Using Popular Frequency Bands
E. A Network of Radar Systems

VIII. MISCELLANEOUS FACTORS AFFECTING RADAR PERFORMANCE
A. Limitations of Radar Systems
B. Countering Multiple Aerial Vehicles
C. Noise in Radar Systems
D. Probability of False Alarms
E. Scan Volume
F. Position of the Radar System
G. Interfacing of Radars with Other Systems
H. Electronic Countermeasures
I. Friend or Foe Identification

IX. COMMUNICATION SYSTEMS FOR THE DETECTION, TRACKING, AND CLASSIFICATION OF UAVS
A. Importance of Communication Systems for UAV Detection, Tracking, and Classification
C. Popular Communication Systems for the Detection, Tracking, and Classification of UAVs
D. Comparison of Communication Systems and Radar Systems

X. METHODS OTHER THAN RADAR SYSTEMS
A. Electro-Optical/Infrared
B. Acoustic Methods
C. Radio Frequency Analyzers
D. Laser based Technique
E. Distributed Sensors
F. Regulating the UAV Air Traffic
G. Space Assets
H. Combat UAVs
I. Popular Counter-UAV Systems
J. Anti-Stealth Methods

XI. CONCLUDING REMARKS