What is Pulse Radar Tracking Mode: Laser Distance Measurement

Pulse radar is able to lock onto a target and maintain basic data such as distance, azimuth, and elevation. "Laser rangefinder module" and "LiDAR module" are often used interchangeably. But the laser rangefinder module provides an alternative method to measure distance with high accuracy.

What is Pulse Radar

Pulse radar tracking mode is a key function in radar systems that aims to continuously monitor and predict the target's position after the target is detected. By adopting this mode, the radar can lock onto the target and maintain basic data such as range, azimuth, and elevation. This enables precise tracking and enhances the radar's ability to predict target movement, ensuring greater accuracy in civilian and military applications.

Difference Between Pulse Radar and Pulse Doppler Radar

Pulse Radar and Pulse Doppler Radar Although they are both designed for detecting and tracking objects, their functions and applications are very different. Pulse radar is one of the earliest radar technologies and is mainly used to measure the distance to the target.

However, in more complex and cluttered environments, such as urban areas or battlefields, it becomes challenging to distinguish between moving targets and stationary objects. This is where pulse Doppler radar becomes important because of its ability to measure the speed of the target and effectively filter out background noise.

In addition to range, pulse Doppler radar provides precise information about the target's speed.

While both types of radar systems use pulsed signals to measure distance, pulse Doppler radar also uses frequency analysis to measure target speed, making its ability to track moving targets in cluttered environments more advanced.

How Pulse Radar Tracking Mode Works

After detecting a target, the radar will usually continue to "detect" the target within the radar's coverage area, using the detected information to obtain a more accurate target location and be able to predict the target location, all of which are called tracking. In pulse radar tracking mode, when the radar locks on to a target, it tracks and automatically maintains key data about the target: range, azimuth, and elevation.

5 Tracking Modes of Pulse Radar

Range Tracking

Range tracking is typically achieved through a technique known as the range gate. As the target’s distance increases or decreases, the range gate automatically adjusts to maintain continuous tracking of the target. The concept of the range gate is as follows:

Radar echoes usually contain noise and target signals. The range gate technique employs two critical gates: an "Early Gate" and a "Late Gate." The Early Gate is positioned near the leading edge of the target echo and detects energy from the initial part of the echo. In contrast, the Late Gate is located near the trailing edge of the target echo, capturing energy from the latter part. By comparing the signals detected by the Early and Late Gates, the system can adjust the tracking gate to remain aligned with the target echo, ensuring accurate and stable range tracking.

Angle Tracking

In radar tracking mode, the system continuously monitors the azimuth and elevation angles of the target. A commonly used method for this purpose is the monopulse tracking technique. Monopulse is the preferred approach for most modern radars due to its high accuracy and robustness against deception.

"Monopulse" means that the radar can determine the target position using a single pulse, rather than relying on a sequence of beams or a full conical scan. This results in a higher and more accurate tracking rate. Another advantage is that, by simultaneously receiving target echoes across all four channels, the system can disregard any temporal variations in the echo.

As illustrated in the diagram, the principle of monopulse tracking uses two to four simultaneous beams arranged side-by-side and stacked in elevation. By comparing the phase or amplitude differences between these beams, the radar can accurately determine the target's angle and perform real-time tracking.

Amplitude Comparison Monopulse

According to the IEEE standard, amplitude comparison monopulse radar determines the angular deviation of a target from the antenna axis by comparing the amplitudes of the signals received from the same target in two different beam patterns. These patterns can either be a pair of beams on opposite sides of the antenna axis or a difference beam that is odd-symmetric relative to the axis combined with a sum beam that is even-symmetric. The four channels depicted in the diagram form sum and difference patterns for both azimuth and elevation tracking.

In amplitude comparison monopulse radar, four overlapping beams are slightly offset from the antenna’s line of sight. By comparing the echoes from two beams in the same plane, the system calculates the angular error of the target. This error signal is then amplified to adjust the antenna's position, quickly reducing the error, often with just one pulse.

The radar generates this error signal by combining the beams' echoes into a "sum" and a "difference" signal. When the target is aligned with the antenna boresight, there is no angular error, and the difference signal is zero. If the target moves off-axis, the difference signal increases with the error angle, while the sum signal helps with target detection and serves as a phase reference.

Phase Comparison Monopulse

In phase comparison monopulse, two or four separate antennas are used to illuminate a distant target. Unlike amplitude comparison, where beams are angled, the beams in phase comparison are parallel.

When a target is on the central axis, echoes reach both antennas at the same time with identical phases. If the target is off-axis, there is a phase delay between the antennas. This method offers higher accuracy compared to amplitude comparison but usually has a lower signal-to-noise ratio. Because phase comparison requires multiple antennas (or an AESA system), it adds complexity and cost to the setup.

While highly accurate, phase comparison monopulse works best when tracking a single target. Its precision drops when multiple targets are present or when multipath reflections interfere.

Precision Laser Rangefinding Solutions 

Our website offers a comprehensive range of advanced laser-based rangefinding solutions, delivering exceptional precision and accuracy for distance measurement and target designation. Unlike traditional radar systems that rely on electromagnetic waves, our innovative Laser Rangefinder Modules use cutting-edge laser technology to provide highly accurate measurements, perfect for applications where precision is crucial.

From Handheld Eye-safe Laser Rangefinder Telescopes for field operations to Integrated Search and Aim Sights for fast target acquisition, our products are built to handle diverse needs. ERDI’s 1535nm microchip laser modules combine state-of-the-art laser technology with advanced optics, delivering precise distance measurements for laser rangefinders and LiDAR systems. This versatile technology ensures accurate aiming and navigation, maximizing performance while minimizing risk.

Laser Rangefinder Modules vs LiDAR Modules

While both modules rely on laser technology for distance measurement, laser rangefinder modules are suitable for applications that require accurate single-point measurements. In contrast, laser rangefinder modules (LiDAR) excel at creating 3D environmental models, which are essential for advanced navigation and mapping tasks.

Purpose and Functionality

Laser rangefinder modules are primarily used for accurate distance measurement. They emit laser pulses and calculate the distance to the target based on the time it takes for the light to return. They are commonly used in industrial applications, robotics, surveying, and handheld distance measurement tools.

LiDAR modules use similar principles but are more complex. They create detailed 3D maps of the surrounding environment by scanning multiple points, making them ideal for self-driving cars, environmental mapping, and advanced navigation systems.

Complexity and Output

Laser rangefinder modules provide simple and accurate distance readings to specific target points. The data is simple and usually only provides a distance measurement, which is suitable for applications that require a single-point distance assessment.

LiDAR modules are able to generate a comprehensive 3D point cloud of an area, and LiDAR systems are more complex and can map the entire environment. This sophistication allows for advanced applications such as obstacle detection, terrain modeling, and detailed object identification.

Applications

Laser ranging modules are often used in scenarios where single or fixed-point distance measurements are required, such as construction, manufacturing, and robotics, for tasks such as object detection and ranging.

LiDAR modules are essential for applications that require spatial perception and mapping, such as self-driving cars, aerial drones for terrain surveying, and smart city infrastructure projects.

Cost and System Requirements

Laser-ranging modules are typically more cost-effective and easier to integrate into a system, making them a popular choice for budget-sensitive projects or applications that do not require extensive environmental mapping.

LiDAR modules are typically more expensive due to the advanced technology involved. LiDAR systems also require more powerful processing power to handle the large amounts of data generated.