Angle Estimation in Non-Doppler Radar Imaging: Exploring the Role of Phase

[Wapochief]

Hey all,

I am brand new to the world of signal processing and radar, but I am trying to simulate a non-doppler imaging radar using pulses. I understand most of the concepts, including steering vectors and measuring distance by the time delay of a radar pulse. I am using a stationary antenna. I don't understand how to get the angle of the target from a 2d signal! I realize it probably has to do with phase, but I am unable to find anything on the subject.

Anyone have some sources or insight?

Thanks,
Wapochief

 

[Bobbywhy]

Wapochief, If you already understand beam steering vectors for transmitting a radar pulse with a fixed antenna, then determining the angle of the target is basically just the reverse. Have you done a Google search using the terms "phased array radar"? I am fairly certain the answer to your question will be found there. If not, do come right back here and post your specific question.

 

[Wapochief]

Hi Bobbywhy,

So suppose I only have one TX and one RX antenna - both stationary, near each other and pointed in the same direction. From my understanding, the steering vectors are just 1 for each. But how do I get the angle of the target? I am trying to create an Angle/Range map.

Thanks

 

[berkeman]

Hi Bobbywhy,

So suppose I only have one TX and one RX antenna - both stationary, near each other and pointed in the same direction. From my understanding, the steering vectors are just 1 for each. But how do I get the angle of the target? I am trying to create an Angle/Range map.

Thanks

If you only have one set of TX/RX antennas, you steer them mechanically. To steer electrically with phasing, you need a 2-d array of antennas.

 

[Bobbywhy]

Hi Bobbywhy,

So suppose I only have one TX and one RX antenna - both stationary, near each other and pointed in the same direction. From my understanding, the steering vectors are just 1 for each. But how do I get the angle of the target? I am trying to create an Angle/Range map.

Thanks

Using the Google search terms “radar phased array beamformer time domain” this appeared and, hopefully, it will provide the answer(s) you want:

“In order to search across the area of interest, the (radar parabolic) antenna must mechanically be aimed or rotated to steer its beam in the desired direction.

In many military applications, this function is often performed electronically, using active electronically scanned array (AESA), which is an electronically steerable antenna. This allows very rapid steering of the radar beam, which is particularly useful for military airborne radars. This technique is known as “beamforming”, which references the electronic steering of the main antenna lobe or beam.

An AESA is built from many small antennas or individual elements. Each antenna element has a transmit and a receive module. Therefore, each element can individually vary the phase and amplitude of both receive and transmit signals. These changes, particularly in phase, provide for steerable directivity of the antenna beam over both azimuth and elevation. Only when the receive signal arrives in-phase across all the antenna elements will the maximum signal be received. This provides the ability to “aim” the main lobe of the antenna in a desired direction. The process is reciprocal, meaning that the same antenna lobe pattern will exist on both receive and transmit (assuming common frequency for receive and transmit)."

http://www.eetimes.com/design/progr...t-3--Beamforming-and-radar-digital-processing

Further information can be found here:

http://www.radartutorial.eu/06.antennas/an14.en.html
http://www.radartutorial.eu/06.antennas/an15.en.html
http://en.wikipedia.org/wiki/Phased_array

 

[Wapochief]

Thanks,

I spent the day reading and studying this and I am closer to understanding. I'll post back if I have any more questions.