Futuristic radar system emitting terahertz waves, analyzing a precessing target.

Terahertz Radar: The Next Frontier in Precision Target Analysis?

Soraya Malik in Tech & Innovation September 2025 • 5 min read.

"Unlocking High-Accuracy Parameter Estimation for Precessing Targets with Wideband Technology"

In the realm of ballistic missile defense, the ability to accurately image, recognize, and classify targets has always been paramount. Among the various factors at play, precession—the wobbling motion of a midcourse target—introduces several key parameters that are critical for effective target assessment. These parameters include precession velocity, precession angle, and the location of the precession center. Traditional microwave radar systems often fall short in providing the necessary resolution for precise estimation of these parameters.

Recent years have seen a surge in research dedicated to parameter estimation and imaging of precessing targets. However, the inherent limitations of microwave radar systems, particularly their poor resolution, restrict the accuracy with which these parameters can be estimated. This limitation also impacts the clarity of radar imaging, making it difficult to discern intricate details about the target's movement and structure. This is where terahertz technology steps in to fill the gap.

Terahertz (THz) radar offers significant advantages in terms of sensitive Doppler recognition and high-resolution imaging. These benefits have led to increasing interest and applications in various radar fields. This article explores a groundbreaking approach to high-accuracy parameter estimation for precessing ballistic targets, leveraging the capabilities of wideband terahertz radar. Furthermore, the results of an experiment involving a precessing warhead model and a 0.32 THz wideband radar system are presented.

How Does Terahertz Radar Enhance Parameter Estimation?

Futuristic radar system emitting terahertz waves, analyzing a precessing target.

To understand how terahertz radar enhances parameter estimation, it's essential to delve into the methodology employed. Consider a simplified model of a precessing ballistic target observed by radar. The target is coning, circling around the O-Z axis with an angular velocity, and the precession angle is θ. The angle between the line of sight (LOS) and the precession axis is α. The distance between the cone-top and the center of mass is h.

According to the derivation in reference [4] from the original article, the radial distance r(t) between the radar and cone-top located at (0,0,h) in the target is given by:

A = 2h sin α sin θ (1)

In equation (1), the micro-motion amplitude of the cone-top can be obtained by the range profile sequence of the cone-top or its time-frequency distribution (TFD) through various means like the inverse Radon transform (IRT). h and θ is the key parameters we'd yet like to acquire. For wideband terahertz radar systems, we have studied several high resolution and high frame rate imaging methods, such as the slide-window range Doppler (RD) algorithm [5]. Therefore, a joint estimation method based on the geometric solution of the high resolution ISAR image sequence is proposed in this paper. We firstly choose a critical location point at the motion trajectory of the cone-top. The tangent line of the critical location point must be parallel to the LOS plane. For instance, the critical location points can be por q in Fig. 1 if the azimuth angle of the LOS is 90°. Then we choose two ISAR images before and after the critical location point as a group, and the time span between these two images is t₁. In other words, we choose the ISAR images τ₁/2 before and after the cone-top passing the critical location. The locations of the cone-top corresponding to these two images are p₁ and q₁ respectively. After that, we plot the diameter of the motion trajectory of the cone-top on the LOS plane, and project p₁ and q₁ on it, namely p3 and q3.

The high resolution and high frame rate imaging methods like the slide-window range Doppler (RD) algorithm, helps in determination of critical location points on motion trajectory of the cone-top. This approach leverages the geometric relationships within ISAR image sequences to enhance the precision of parameter estimation. By carefully selecting and processing ISAR images, researchers can extract valuable information about the target's precession motion, leading to more accurate assessments.

The Future of Terahertz Radar in Military Applications

The research outlined in this paper demonstrates the significant potential of terahertz radar systems for high-precision parameter estimation of precessing targets. The experimental results, which show estimation errors within 5%, underscore the feasibility and accuracy of the proposed method. As terahertz technology continues to advance, it is poised to play an increasingly crucial role in military applications, offering enhanced capabilities for target recognition, classification, and defense strategies. The ability to accurately estimate key parameters such as precession velocity and angle opens new avenues for developing more effective countermeasures and ensuring national security. Further research and development in this area will undoubtedly pave the way for innovative radar systems that can meet the evolving challenges of modern warfare.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1109/irmmw-thz.2018.8510474, Alternate LINK

Title: Parameter Estimation Of The Precessing Targets With A Wideband Terahertz Radar

Journal: 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

Publisher: IEEE

Authors: Qi Yang, Bin Deng, Hongqiang Wang, Yuliang Qin, Chenggao Luo

Published: 2018-09-01

Everything You Need To Know

How does terahertz radar improve parameter estimation compared to traditional microwave radar systems?

Terahertz radar significantly enhances parameter estimation by offering sensitive Doppler recognition and high-resolution imaging capabilities, which microwave radar systems lack. By using wideband terahertz radar, critical parameters related to a target's precession, such as precession velocity and angle, can be estimated with greater accuracy. The method involves analyzing the target's motion trajectory using techniques like the slide-window range Doppler (RD) algorithm to pinpoint critical location points. This ultimately leverages geometric relationships within ISAR image sequences to improve the precision of parameter estimation.

What role does the slide-window range Doppler (RD) algorithm play in high-accuracy parameter estimation?

The 'slide-window range Doppler (RD) algorithm' is used to achieve high-resolution and high frame rate imaging. This is important because it helps determine the critical location points on the motion trajectory of the cone-top. By processing ISAR images around these critical points, researchers can extract precise information about the target's precession motion, allowing for more accurate parameter estimation. The high frame rate ensures that even subtle changes in the target's motion are captured, leading to more robust and reliable results.

What are the key parameters needed to accurately assess a precessing target, and why are they important?

The key parameters for assessing a precessing target include precession velocity, precession angle (θ), and the location of the precession center, as well as the distance between the cone-top and the center of mass (h). Accurately estimating these parameters is essential for effective target recognition and classification, particularly in ballistic missile defense. These parameters provide insights into the target's movement and structure, enabling the development of more effective countermeasures.

How do researchers obtain the micro-motion amplitude of the cone-top, and what key parameters can be acquired from it?

The micro-motion amplitude of the cone-top can be obtained by examining the range profile sequence of the cone-top or its time-frequency distribution (TFD) through methods like the inverse Radon transform (IRT). By extracting the micro-motion amplitude, key parameters such as 'h' (the distance between the cone-top and the center of mass) and 'θ' (the precession angle) can be acquired. This process leverages the geometric relationships within ISAR image sequences to enhance the precision of parameter estimation, which is crucial for accurate target assessment.

What are the potential military applications of terahertz radar, and how might it shape future defense strategies?

The future of terahertz radar in military applications includes enhanced capabilities for target recognition, classification, and defense strategies. The accuracy of parameter estimation, as demonstrated by the research, allows for the development of more effective countermeasures. Further advancements in terahertz technology will lead to innovative radar systems capable of meeting the evolving challenges of modern warfare. This includes the potential for more precise tracking and interception of ballistic missiles, as well as improved situational awareness in complex combat scenarios.