Zaslon phased array radar

[Pavel]

Guys, maybe it's stupid question, but still... MiG-31 was equipped with full-axis phased array radar Zaslon SBI-16 in 1976-1978, first real in-flight tests.

While for Su-27 in 1982 it was taken decision to stop all the works on phased (in one dimension) array Mech (Sword) and to switch to mechanical old Rubin radar.

Yes, I know, it's in the mass and power etc and it's complete redisign of radar for new plane, but still... if there is technology already, was it really so hard to implement it for Su-27?

[zb10948]

Simple. The array design failed, and time was running out. So they reverted back to mechanical type.
I'll give you details when i get back home, i have the full story somewhere...

[Pavel]

So happy to see you here, zb!

I knew I may count on you in this queston

Yes, I know that Mech design failed, my question is - why, when they had working and already not a prototype on MiG-31...

[staywhite]

Originally Posted by Pavel

Guys, maybe it's stupid question, but still... MiG-31 was equipped with full-axis phased array radar Zaslon SBI-16 in 1976-1978, first real in-flight tests.

While for Su-27 in 1982 it was taken decision to stop all the works on phased (in one dimension) array Mech (Sword) and to switch to mechanical old Rubin radar.

Yes, I know, it's in the mass and power etc and it's complete redisign of radar for new plane, but still... if there is technology already, was it really so hard to implement it for Su-27?

I am not Guy, but i want to write what
I cannot answer your question exactly, but i know physical bases which are used in radar technology. I have found no Topic of radars, therefore, i write here. If such Topic exists, you give me link and will write there more, also anti-radar masking.

I write also a little bit about Doppler effect, because The Zaslon is a Pulse-Doppler radar with a passive electronically scanned array (PESA) antenna and digitally signal processing.

Passive radars are used only for signal receipt, purpose searches, accompanies the purpose, identification and cartographical representation by results. the frequency is in the micro- and infrared area. Such radars are fastened to rockets, on account of preserved information this rocket in the concrete purpose is directed to destroy this. Passive radars have only receiver, differently from active radars which have receiver and also transmitter, as for example tornado Nose radar, RRP-117, APAR.

In Phased Radren the methods are used by Phase change and the analogous signals are also converted in digital ones. If somebody that interests, I can soon describe.

Here briefly from passive array and Doppler effect:

A phased array antenna is composed of lots of radiating elements each with a phase shifter. Beams are formed by shifting the phase of the signal emitted from each radiating element, to provide constructive/destructive interference* (*Whenever waves originating from two or more sources interact with each other, there will be phasing effects leading to an increase or decrease in wave energy at the point of combination.) so as to steer the beams in the desired direction.
In adar technology the Doppler Effect is using for two tasks: Speed measuring and MTI - Moving Target Indication
The Doppler- Effect is the apparent change in frequency or pitch when a sound source moves either toward or away from the listener, or when the listener moves either toward or away from the sound source.

The apparent change in frequency between the source of a wave and the receiver of the wave is because of relative motion between the source and the receiver. To understand the Doppler effect, first assume that the frequency of a sound from a source is held constant. The wavelength of the sound will also remain constant. If both the source and the receiver of the sound remain stationary, the receiver will hear the same frequency sound produced by the source. This is because the receiver is receiving the same number of waves per second that the source is producing.

Now, if either the source or the receiver or both move toward the other, the receiver will perceive a higher frequency sound. This is because the receiver will receive a greater number of sound waves per second and interpret the greater number of waves as a higher frequency sound. Conversely, if the source and the receiver are moving apart, the receiver will receive a smaller number of sound waves per second and will perceive a lower frequency sound. In both cases, the frequency of the sound produced by the source will have remained constant.
The frequency shift is a measure of the purpose speed and becomes Doppler - frequency fD called:



fD=Doppler Frequency
λ = wavelength
v = speed of the wave-source

This formula is valid, if the speed if the source of a wave is like the radial speed. But the airplane usually flies in another direction than the direction towards to the radar. Only the radial speed is then also measured. However, this is different from the aim speed so that the following formula is valid:



fD=Doppler Frequency
λ = wavelength
v = speed of the aircraft
α = angle between the direction of the transmitted/reflected signal and the direction of flight of the target

Doppler-frequency formula




where:
ftx is the transmitters frequency
c0 is the speed of the light
vr is the radial speed of the aim (Vr= d(r)/dt )

p.s. Thus, for more description one needs separate topic. Excuse for my English.

[Carlo]

Nice to see you here, zb! Come on, appear more often.
And now there is another person who knows a lot on radars and avionics, also, staywhite. Welcome to the forum!

[Pavel]

Looks like we have kinda new star here? And it's girl!

Will take time to get into your post, staywhite

[zb10948]

Nice text staywhite!

Carlo, i'll try to be here more often. There's no real reason why i haven't visited a lot in a past year...but things change in life, you drift into some other direction and forget some of the old habits.

Pavel, i still haven't found that bit about early Su-27 development radar. However, from what i remember, after few flights of original T-10 chief of project decided whole re-engineering. Partly due to unsatisfactory aerodynamic results of initial platform, partly due to overweight avionics.

Perhaps they haven't found a way to minimize the radar (size of the array does matter in terms of weight, but the backplane and computer hardware also weight a lot, and that's quite fixed), were late on the schedule, and decided to go for Slot Back.

[staywhite]

Danke, Gentlemen I read here very interesting Topics, thanks to you.
p.s.Excuse me for oFF.

[Stealthflanker]

well i think it's mainly because the weight considerations ... Mech doesn't get into Su-27.. this mainly associated with Processing system ,
i heard the entire system of Zaslon weigh as heavy as 1 tonne and it's bulky.. Maybe the Flankers have no adequate space to accommodate the processing unit

[Pavel]

Yes, if it's weight, it makes sense, Su-27 had huuuge problems with extra weight.