Phase Array Radar, theory and operation

Some of topics relate to the ships and awacs talk quite a bit about phase array radar but it also present quite confusing elements relate to it. Here, a dedicate thread to clarify some of the points relate to this important technology.

A)looking at 052C there are only two sided phase array radar on the left and right sides. Does that make it vulnerable frontside and backside since there aren't array radar facing those directions.

B)Many people have the wrong belief that phase array radar continously sampling the targets. That would be wrong cause continously update would have huge database and make it diffcult to process. What's the sampling rate?

C)For active phase array, it would consists thousands little of Transmitter/Receiver units. Does each T/R unit keep track of each of target therefore thousands of units can track thousands of targets? What does it mean by steering the T/R? They can't rotate certain degrees can they?

D)Since each T/R unit function independently, can each unit transmit different frequency and signals? so you have some unit transmit low frequency wave, some unit transmit medium frequency and others transmit high frequency?

E)CMOS technology have been in the MMIC field, can they use to build the AESA T/R unit? or they can't the power the system require?

world first operational AESA, was mounted on top of the japanese destroyer in 1989 (forget the designation),it use hybrid technology rather than smaller,less power consumption monolith circuit.
there's a belief and speculation than Sea tiger AESA carry by 052C was hybrid type ,this due to her large size.

lilzz said:

Some of topics relate to the ships and awacs talk quite a bit about phase array radar but it also present quite confusing elements relate to it. Here, a dedicate thread to clarify some of the points relate to this important technology.

A)looking at 052C there are only two sided phase array radar on the left and right sides. Does that make it vulnerable frontside and backside since there aren't array radar facing those directions.

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No, its actually four faced, two in the front and two in the rear, all set in the four corners of the superstructure, so they are in the same time, left and right.

B)Many people have the wrong belief that phase array radar continously sampling the targets. That would be wrong cause continously update would have huge database and make it diffcult to process. What's the sampling rate?

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Dunno.

C)For active phase array, it would consists thousands little of Transmitter/Receiver units. Does each T/R unit keep track of each of target therefore thousands of units can track thousands of targets? What does it mean by steering the T/R? They can't rotate certain degrees can they?

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No. They all either track one target or many targets all at the same time. Not independently but as one big set.

D)Since each T/R unit function independently, can each unit transmit different frequency and signals? so you have some unit transmit low frequency wave, some unit transmit medium frequency and others transmit high frequency?

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No. That would be interfering with each other.

E)CMOS technology have been in the MMIC field, can they use to build the AESA T/R unit? or they can't the power the system require?

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There are many different materials, some better on longer others on shorter frequency. So each material has a general band. The one used on a ship might be using longer bands than those used in a plane which is X-band. Different materials have different heat characteristics as well. Here is a primer.

crobato said:

No. They all either track one target or many targets all at the same time. Not independently but as one big set.

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Not sure if I perhaps didn't get your point. But I was under the impression that AESAs can form multiple agile beams. Meaning of the thousand modules, let's say hundred shape a beam that tracks target A in one direction, while another hundred shape a different beam that tracks target B in a different direction.
Or that one set of modules searches the ground for vehicles, while another set searches the airspace ahead for aircraft. (And in the meantime a third set broadcasts a comm message?)

Scratch said:

Not sure if I perhaps didn't get your point. But I was under the impression that AESAs can form multiple agile beams. Meaning of the thousand modules, let's say hundred shape a beam that tracks target A in one direction, while another hundred shape a different beam that tracks target B in a different direction.
Or that one set of modules searches the ground for vehicles, while another set searches the airspace ahead for aircraft. (And in the meantime a third set broadcasts a comm message?)

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They don't. That's an internet myth. Having two different beams and waveforms on the same face means that the beams would interfere and cancel out each other, even with different frequencies. Even two separate radars just a distance from each other can have mutual interference. And also, even though each module has a separate transmitter, all of them have to be synchronized by a single clock generator.

What happens instead is that the array does one thing and after doing that, switches to do another thing quickly. Kind of trying to juggling between tasks.

an excellent tutorial on phase array and digital beam forming.

crobato said:

There are many different materials, some better on longer others on shorter frequency. So each material has a general band. The one used on a ship might be using longer bands than those used in a plane which is X-band. Different materials have different heat characteristics as well. Here is a primer.

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The old radar systm consists of a device call magnetron, a electromagnetic device that used tens of thousands of volts to generate the wave to the huge antenna.

Now the T/R module /w semiconductor tech only uses from few volts to no more than 20 volts.

The distance the radar wave travels depend on the power of the system. On the surface, it seems odd how a modern /w much lower volatge radar can search far distance 400KM /w 3 to 4cm wavelength compare to the magnetron. Afterall, the magetron has much more power?

Doesn't this violate the math equation distance proportional to the power being deliver to the system?

Distance a radar wave travels depends also on attenuation. The higher the frequency, the much greater is the attenuation or energy loss traveling through a medium.

Magnetron are not necessarily large and clumsy massive energy eating devices. You can them inside a microwave oven. In addition there are a number of different types of magnetrons. The klystron delivers higher frequencies and the TWT or traveling wave tube is even higher. Modern radars use TWTs.

crobato said:

the TWT or traveling wave tube is even higher. Modern radars use TWTs.

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What voltage does TWT uses? I suspect it's still pretty high.

I still confuse how a modern AESA radar /w it T/R module with few volatge on semiconductor device can generate wave that can reach few hundred kms.

Sounds like I can construct one of those AESA T/R module myself (just like a commercial semiconductor device) at my home and turn it on and it can reach long distance.

Does not matter what the source is, its the kind of wave generated that matters. Long wave = long range, short wave = short range.