With the continuous advancement in wireless communication technology, the global demand for wireless spectrum within the communication industry is rapidly increasing.

Radar technology, as a vital aspect widely utilized in civil and scientific research domains, has consistently garnered significant attention.

In today’s modern society, radar has become an indispensable tool, utilized in a variety of fields such as meteorological forecasting, aviation navigation, and traffic management. To fully appreciate the significance of radar, it is important to understand its fundamental principles, which lie at the intersection of science and engineering.

The origins of radar technology can be traced back to the early 20th century, with pioneering work by physicist Nikola Tesla and other scientists studying the properties of radio waves. Over the years, radar has evolved through various stages, starting with the early “Chain Home” radar system, followed by advancements in pulse radar and continuous wave radar technologies.

More recently, the concept of Dual Functional Radar and Communication (DFRC) emerged from the broader field of Radar and Communication Spectrum Sharing (RCSS). Within RCSS, two primary research directions have developed: DFRC and Radar Communication Coexistence (RCC). The latter is closely related to Cognitive Radio (CR) technology, which focuses on managing interference between radar and communication systems at the physical communication layer.

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This involves optimizing radar detection performance while ensuring compliance with communication Signal-to-Interference-plus-Noise Ratio (SINR) constraints, or vice versa. In contrast, Dual Functional Radar and Communication (DFRC) is more ambitious and challenging to implement. It seeks to integrate communication and radar functions through innovative design approaches, such as hardware platform development, resource allocation, and advanced signal processing techniques.

The fundamental principles of radar are based on the emission, propagation, reflection, and reception of radio waves. The key components and principles of radar systems are outlined as follows:

Radio Transmitter:

At the heart of any radar system is the radio transmitter, which generates and sends out radio waves into the surrounding space. Depending on the radar system’s design, these radio waves may be emitted as either pulse waves or continuous waves.

Antenna:

Antennas play a dual role in radar systems: they transmit radio waves and receive signals that are reflected by target objects. The performance and resolution of a radar system are closely linked to the design of the antenna. Various types of antennas, including open-ended antennas, horn antennas, and phased array antennas, are employed to suit different radar applications.

Propagation of Radio Waves:

Once emitted from the antenna, radio waves propagate through space at a specific velocity. These waves are subject to phenomena such as reflection, refraction, and scattering as they travel through free space or the atmosphere.

Target Reflection:

When radio waves encounter a target, some of their energy is absorbed by the object, while the remaining energy is reflected back toward the radar system. The intensity and characteristics of the reflected signal depend on the shape, size, and electromagnetic properties of the target.

Receiver:

The receiver in a radar system captures the reflected signals from target objects. It is responsible for amplifying, filtering, and processing these signals to extract valuable information, such as the distance, speed, and direction of the targets.

Signal Processing:

Signal processing is a critical element of radar technology, involving techniques for analyzing and interpreting the received signals. This process includes filtering out noise, detecting targets, measuring their properties (such as range, velocity, and angle), and tracking their movement over time.

Display and Interpretation:

The final stage in radar operation involves presenting the processed data to the user in a clear and understandable format. This may include displaying targets on a screen, generating alerts, or providing detailed analytical reports to assist in decision-making.