:rolleyes:

If you want to be in fantasy land about basic radar and missile technologies please go right ahead.

No problem. Just digitize the sensitive parts.

Repeat after me: Steam propulsion is less reliable and efficient than gas turbines.

What about every ship and submarine that is nuclear powered? Nuclear power is actually a nuclear reactor powering up steam turbines.

Steam turbines are more noisy

They’re not as quiet as electric motors, but definitely quiet enough for some nuclear submarines out there.

Target acquisition radars are not exactly tightly knit into the system. Just about anything can be passed to the target tracking and missile guidance radar (Flap Lid), while the target acquisition radars in theory, can also pass initial tracks to non S-300 systems, so they can be utilized more in a general sense. The really tight knit part involves the target engagement radar (30N6E Flap Lid). That’s the one important identifying component. Having multiple target acquisition radars means the system is versatile enough to take its initial tracks from anything, including AEW aircraft.

Do note that both target acquisition and target engagement radars are capable of independent tracking on their own so I don’t want to use the phrase target tracking.

Nope. Never increased in size. Never decreased in size. Fighter radar modules are always the same size because each radiating element is matched to the spectrum length of X-band. Its the same size even with the various PESAs. Its the same size—length of wave guide slot—even in all the slotted arrays. Its when you have longer wavelengths (wider band) that requires larger modules. The radiating element of a C-band radar is bigger than an X’s. The S band radiating element is bigger than the C-band. Goes down the line. If you see those UHF AESA, each radiating element is practically a Yagi fishbone type. Correspondingly, a Ku or Ka band element would be much smaller than an X-band element.

This is not dictated by semiconductor advances. This is dictated by microwave physics. Semiconductor advances would affect the back end processing systems only.

I’m referring to the array elements BTW. That’s always fixed to the spectrum.

If you are referring to the black boxes on the back end, yes, certainly they have shrunk. They’re much cooler too. A fighter radar with the same capability or more as the early version APG-68 can now be packed into a much smaller package except for the antenna, although any loss of antenna gain from a smaller array can be compensated with better amplifiers. A fighter radar about the same size as the APG-68 today is now far more capable thanks the software algorithms, more software modes, increased processing and data bandwidths, better amplifiers and digital signal processors. An MSA with modern backend is much more capable than an MSA one or even two decades ago. Even the TWTs powering the emitters are capable of some surprising tricks on their own. After all, AESA, PESA, MSA, they’re all just antennas, ultimately its the brains in the back end that truly count.

Originally Posted by swerve View Post
Surely, you’re talking about minimum size. Have fighter radar modules reached the minimum size for their wavelengths?

The actual size of modules in fighter radars has decreased considerably in the last decade, while their energy efficiency has increased, reducing heat output, & thus making it possible to pack more into a given space, & reducing the amount of cooling needed.

Surely, you’re talking about minimum size. Have fighter radar modules reached the minimum size for their wavelengths?

The actual size of modules in fighter radars has decreased considerably in the last decade, while their energy efficiency has increased, reducing heat output, & thus making it possible to pack more into a given space, & reducing the amount of cooling needed.

Nope. Never increased in size. Never decreased in size. Fighter radar modules are always the same size because each radiating element is matched to the spectrum length of X-band. Its the same size even with the various PESAs. Its the same size—length of wave guide slot—even in all the slotted arrays. Its when you have longer wavelengths (wider band) that requires larger modules. The radiating element of a C-band radar is bigger than an X’s. The S band radiating element is bigger than the C-band. Goes down the line. If you see those UHF AESA, each radiating element is practically a Yagi fishbone type. Correspondingly, a Ku or Ka band element would be much smaller than an X-band element.

This is not dictated by semiconductor advances. This is dictated by microwave physics. Semiconductor advances would affect the back end processing systems only.

Why does electronic scanning create heat? And lots of it.

Electronic scanning is done by constructive and destructive interference. How is that interference created?

Radar waves are emitted by different elements. To create interference, the wave emitted by the element next to your first element has to be on a different phase (latency), and this goes on and on, with each phase from each element different from the other. (The other way is to have the wavelength of the next element to be slightly different from the first, and this is called frequency scanning).

If the waves are more or less aligned with each other, they start boost each other, creating constructive interference. If the waves are more or less offset from each other, they begin to cancel out each other, creating destructive interference. All of this can be carefully controlled through the phasing of each element. If one side is stronger and the other is weaker, then the beam shifts to the stronger direction.

What happens to the energy when two radar waves are canceling out with destructive interference? That’s right, laws of thermodynamics. Energy cannot be created nor destroyed. The canceled out radar energy doesn’t disappear from this universe, it is turned into something else. And that is heat. Thus heat generation is something intrinsic with all forms of electronic scanning. Its worst on AESAs because of the semiconductor substrates that form a second, but nonetheless, as equally dominant heat source. Not unless you have shifted to Gallium Nitride (still not very reliable these days) on Silicon Carbide substrates or just pure Silicon Carbide (good only up to S or C band—better for SAM and naval radars only), will you see a significant reduction in power usage and heat containment from the semiconductor substrate.

By this time you would also have figured out that as the beam scans at a wider angle, so does the interference needed becomes greater which also has a parasitic drain on the radar beam. Thus when the beam scans wide, its actually weaker than it is on center. The more it scans to the side, the more heat it produces. Note that semiconductors are less efficient in a hot environment (greater electrical resistance) than in the cold. Due to the heat, the efficiency of the array drops. Hence there is a greater requirement to keep it cool and maintained at a certain temperature.

Video cards is a horrible analogy because modern ones are made in micron sizes smaller by a magnitude over those ten years ago. An array element on the other is always fixed in size to the wavelength its using. You can reduce power consumption in the back end using electronic miniturization, but an array always has fixed power requirements because you want powerful not weak beams if you’re going to detect far. And physics don’t adjust to modernity.

That assumes that several hundred to over a thousand T/R modules, plus the structure to hold them, are lighter than a single mechanically steered antenna. Up to now, that has not been the case: the AESA array has been heavier. There have also been cooling issues, which I think in some cases may have required active cooling & the extra weight that implies.

With the reduction in the size & weight of T/R modules, the weight is swinging in favour of AESAs, but so far, all the figures I’ve seen so far have suggested they’re still heavier, & until someone comes up with some credible (i.e. supported by evidence, e.g. quotes from manufacturers) figures, I’m reluctant to accept it’s changed – yet.

Size of modules are dictated and directly proportional to the frequency wavelength. A module can’t be smaller than the radar’s physical wavelength. You can expect that the module for a K band would be much smaller than a module for an S band. They’re fixed by physics.