Design and assessment of a circularly polarized antenna array
(2025) EITM01 20251Department of Electrical and Information Technology
- Abstract
- Radar has come a long way since its invention in the 1930s. It is not only used to detect the distance and angular position of a target but can also measure velocity thanks to the Doppler frequency shift. In more advanced systems, the radar can perform tasks such as imaging and classification of the target. In some cases, full or partial polarimetry is used to gain additional information about the target, such as shape and material. This requires the system to be able to send and detect two orthogonal waveforms, such as right- and left-hand circular polarizations. Radar systems are also sensitive to noise and clutter, which can both be reduced using circularly polarized signals. However, such systems often use large and complex antenna... (More)
- Radar has come a long way since its invention in the 1930s. It is not only used to detect the distance and angular position of a target but can also measure velocity thanks to the Doppler frequency shift. In more advanced systems, the radar can perform tasks such as imaging and classification of the target. In some cases, full or partial polarimetry is used to gain additional information about the target, such as shape and material. This requires the system to be able to send and detect two orthogonal waveforms, such as right- and left-hand circular polarizations. Radar systems are also sensitive to noise and clutter, which can both be reduced using circularly polarized signals. However, such systems often use large and complex antenna arrays. In this thesis, an antenna for a fully polarimetric circularly polarized radar is designed. Six different antenna elements are evaluated based on several criteria. The chosen element is optimized and placed in an array where it is again evaluated, optimized and proven against an optimized, previously discarded design. Lastly, a complete antenna array layout is developed. The final design
meets the pre-established requirements on gain and bandwidth, but fails to fulfill the requirements on beamwidth. The final design is assessed based on radar performance, where it has an estimated range of 50 - 70 m before any signal processing enhancements and a range resolution of approximately 0.8 m. The radar antenna can be used either by transmitting with one circular polarization handedness at a time, performing full or partial polarimetry, or by sending both simultaneously gaining resolution in elevation without separating transmission in time. (Less) - Popular Abstract
- Imagine throwing a ball against a wall. If you know the speed of the ball and how long it takes between you throwing it and catching it again, you can calculate how far away the wall is. That is exactly how radar works. Now, radar uses radio waves instead of a ball, but the concept is the same. Radio waves are the same type of waves as light, but they are invisible. They travel through the air with the speed of light. If you "throw" one and then "catch" it again, you can calculate the distance to where it bounced.
Unlike a ball however, radio waves are not one particle travelling through space. Rather, they are like circular ripples on water, travelling outwards with the speed of light. The particles do not move forwards but up and down... (More) - Imagine throwing a ball against a wall. If you know the speed of the ball and how long it takes between you throwing it and catching it again, you can calculate how far away the wall is. That is exactly how radar works. Now, radar uses radio waves instead of a ball, but the concept is the same. Radio waves are the same type of waves as light, but they are invisible. They travel through the air with the speed of light. If you "throw" one and then "catch" it again, you can calculate the distance to where it bounced.
Unlike a ball however, radio waves are not one particle travelling through space. Rather, they are like circular ripples on water, travelling outwards with the speed of light. The particles do not move forwards but up and down repeatedly, until the wave has passed. This is how normal radar works. Waves that go up and down or side to side are sent out and received. But who says that that is the best way?
Some radars use another shape of wave, called circularly polarized waves. They do not just move up and down or side to side, but in a circular motion. To create radio waves you need something called an antenna, but to make the antenna transmit the waves exactly how you want them is tricky. That is what this thesis is about, designing an antenna for radar applications using circularly polarized radio waves.
Once again, imagine you are throwing that ball against the wall. If your ball bounces several times before it returns to you, for example hits the ground and the wall, your estimate of the distance to the wall will be off. These kinds of indirect paths are tricky for radars. However, if you knew that the ball had bounced twice you could just disregard the results. Circularly polarized waves carry information about the number of reflection they have made. That information can be used to build better radar systems.
As well as carry information about the number of bounces, circularly polarized waves can also convey information about what it bounced on. Another perk is the fact that it can see through rain more effectively than its conventional counterpart.
In this thesis work, an antenna is designed to transmit and receive circularly polarized radio waves in an efficient and precise way. The system can not only give information about the distance to the target (the "wall" in the parable) but also determine in what direction it is and at what speed it is moving. It can also provide some information about the target because of its circular polarization. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9201130
- author
- Andersson, Anna LU
- supervisor
- organization
- course
- EITM01 20251
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Radar, Antenna Array, Circular Polarization, Polarimetry, FMCW
- report number
- LU/LTH-EIT 2025-1073
- language
- English
- id
- 9201130
- date added to LUP
- 2025-06-18 13:06:21
- date last changed
- 2025-06-18 13:06:21
@misc{9201130,
abstract = {{Radar has come a long way since its invention in the 1930s. It is not only used to detect the distance and angular position of a target but can also measure velocity thanks to the Doppler frequency shift. In more advanced systems, the radar can perform tasks such as imaging and classification of the target. In some cases, full or partial polarimetry is used to gain additional information about the target, such as shape and material. This requires the system to be able to send and detect two orthogonal waveforms, such as right- and left-hand circular polarizations. Radar systems are also sensitive to noise and clutter, which can both be reduced using circularly polarized signals. However, such systems often use large and complex antenna arrays. In this thesis, an antenna for a fully polarimetric circularly polarized radar is designed. Six different antenna elements are evaluated based on several criteria. The chosen element is optimized and placed in an array where it is again evaluated, optimized and proven against an optimized, previously discarded design. Lastly, a complete antenna array layout is developed. The final design
meets the pre-established requirements on gain and bandwidth, but fails to fulfill the requirements on beamwidth. The final design is assessed based on radar performance, where it has an estimated range of 50 - 70 m before any signal processing enhancements and a range resolution of approximately 0.8 m. The radar antenna can be used either by transmitting with one circular polarization handedness at a time, performing full or partial polarimetry, or by sending both simultaneously gaining resolution in elevation without separating transmission in time.}},
author = {{Andersson, Anna}},
language = {{eng}},
note = {{Student Paper}},
title = {{Design and assessment of a circularly polarized antenna array}},
year = {{2025}},
}