In this lecture, we are going to learn about the Pulse Doppler Radar, a block diagram of Pulse Doppler Radar, its application advantages, and in the end, we will learn the disadvantages of Pulse Doppler Radar. So let’s start with the basic knowledge of Pulse Doppler Radar.
Pulse Doppler Radar
- Pulse radar is a combination of pulse radar and CW radar. It works on the principle of Doppler shift as MTI radar follows.
- As per the Nyquist criterion, the sampling rate(i.e PRF) should be greater and equal to twice the doppler shift frequency but in MTI due to the use of low frequency, it became under-sampled.
- It will lead to ambiguous estimation of target speed and occurrence of blind speed, where the target appears stationary and unresolvable against background clutter.
- Pulse Doppler Radar being high PRF radar, can remove the doppler ambiguities.
- To extract the doppler shift information of the carrier, the pulse should be modified by introducing a coherent oscillator (COHO) for frequency stability in the transmitter and receiver chain. It employs a coherent radar system.
Pulse Doppler Radar Block Diagram
- The pulse doppler radar block diagram is shown in the figure below:
- Pulse doppler radar is classified as high PRF and medium PRF. In high PRF pulse radar, there is ambiguity in the range but ambiguities in the velocity. In the medium PRF pulse radar, there are ambiguities in range and velocity.
- A STALO (stable local oscillator) is used to allow the phase of the transmitter signal to be maintained by a locking mixer. The output og the locking mixer is given to lock the COHO phase and inurn it serves as a reference phase for the detector at the intermediate frequency.
- Now the phase detector measures the difference in phase between two RF signals. Due to the target motion the phase path of the echo signal changes from pulse to pulse and by the same amount, the phase difference will vary.
Advantages of Pulse Doppler Radar
Pulse Doppler radar is a type of radar that is commonly used in various applications, including weather forecasting, military surveillance, air traffic control, and more. Here are some of the advantages of pulse Doppler radar:
- Ability to distinguish between stationary and moving targets:
- Pulse-Doppler radar is capable of distinguishing between stationary and moving targets. This is achieved by using the Doppler effect, which is the change in frequency of a wave when the source or observer is moving relative to the other. The radar is able to detect and measure the frequency shift in the reflected signals from the target, allowing it to determine whether the target is moving or stationary.
- High accuracy:
- Pulse-Doppler radar has high accuracy in measuring the velocity of moving targets. This is because it can detect and measure even small changes in the frequency of the reflected signal, which allows for precise calculation of the target’s velocity.
- Resistance to interference:
- Pulse-Doppler radar is less susceptible to interference from clutter and other sources of noise. This is because it uses short pulses of radio waves that can penetrate through the clutter and other sources of noise, allowing for clearer detection of the target.
- Capability to detect small targets:
- Pulse-Doppler radar is capable of detecting small targets, such as missiles and drones. This is because it can distinguish between the tiny changes in frequency caused by the movement of these targets and the background clutter.
- Pulse-Doppler radar can be adapted to a wide range of applications and environments, making it a versatile and flexible tool. It can be used for weather forecasting, air traffic control, military surveillance, and other applications. It can also operate in various weather conditions and at different altitudes.
- A pulse doppler radar has got the ability to reject unwanted echoes by using doppler filters or by range gating.
- It can measure the range and velocity over predetermined limits, even in presence of multiple targets.
- Signal to noise ratio can be increased by using coherent integration.
Disadvantages of Pulse Doppler Radar
- While pulse Doppler radar has many advantages, there are also some disadvantages to this type of radar. Here are some of the main limitations:
- Cost: Pulse-Doppler radar systems can be expensive to develop, manufacture, and maintain. This can make them impractical for some applications, especially those with limited budgets.
- Complexity: Pulse-Doppler radar systems can be complex and require specialized training to operate and maintain. This can make them less accessible to small organizations or individuals who lack the necessary expertise and resources.
- Limited range: Pulse-Doppler radar systems have a limited range, which can make it difficult to detect targets that are far away. This is because the energy of the radar waves spreads out as it travels, reducing the strength of the signal at longer ranges.
- Limited resolution: Pulse-Doppler radar systems have a limited resolution, which can make it difficult to distinguish between targets that are close together or moving at similar speeds. This can lead to errors in velocity measurement or the detection of false targets.
- Vulnerability to jamming: Like any radar system, pulse Doppler radar is vulnerable to jamming and other forms of electronic countermeasures. This can make it difficult to operate in environments where there is a high likelihood of interference or jamming.
- Overall, pulse Doppler radar has many advantages, but also some limitations that must be taken into consideration when selecting a radar system for a particular application.
Applications of Pulse Doppler Radar
- Pulse Doppler radar is used in a wide range of applications, including:
- Military surveillance: Pulse-Doppler radar is used extensively by the military for surveillance and reconnaissance. It is used to detect and track aircraft, ships, ground vehicles, and other moving targets.
- Air traffic control: Pulse-Doppler radar is used by air traffic controllers to monitor and control air traffic. It is used to track the position and velocity of aircraft and provide real-time information to pilots and ground crew.
- Weather forecasting: Pulse-Doppler radar is used in weather forecasting to detect and track storms, hurricanes, and other weather patterns. It is used to measure the movement and intensity of precipitation, wind, and other weather variables.
- Search and rescue: Pulse-Doppler radar is used in search and rescue operations to locate missing persons, boats, and aircraft. It is used to detect and track the movement of targets over large areas.
- Automotive safety: Pulse-Doppler radar is used in the automotive industry for safety applications, such as collision avoidance and adaptive cruise control. It is used to detect and track other vehicles and objects on the road and provide warnings to the driver.
- Industrial process monitoring: Pulse-Doppler radar is used in industrial process monitoring to detect and measure the movement of materials and equipment. It is used to monitor the flow of materials in pipelines, the movement of conveyor belts, and other industrial processes.
- It is being used as weather warning radar at the target motion, locking of thunderstorms, and turbulence in the air.
- It is very useful in detecting and estimating the target motion, locking the particular target out of a group.
- To observe thunderstorms, rain, and hail, a double polarization doppler radar is being used.