This post is by mrdetonator, at the acig.org forums, hopefully he will be here soon to repost himself.The Sapfir-23E (izdelie 323E).
The Sapfir-23E radar itself represents a coherent pulse Doppler system and it allows:
-search and track of enemy targets in all-aspect at any weather condition, day/night, natural interference (earth /clouds) and active/passive jamming.
-target recognition in co-op. with the SRZO-2 (friend-foe) interrogator
-single target track, measuring target range, azimuth and angular positions.
-search and track of targets emitting heat, the radar antenna controlled by IRST sensor.
-to form control signals for the SAU-23A autopilot in co-op. with LASUR-M (Vozdukh-1M) and RSBN-6S (ROMB-1K) systems, e.g. giving the "break-away" signal...
-to form control signals for launching guided A-A missiles, provides continuous illumination of the target for the RGS-23 seeker, to form control signals during the gun aiming and ensures launching of unguided missiles in the synchronous/asynchronous mode.
-to indicate RADAR/IRST information on the SEI indicator and one-way command symbols on the symbol indicator mounted on the gun sight ASP-23DE.
The Sapfir-23E uses the mono-pulse technique to track a single target. Such a radar system consists of two parabolic antennas (moving, fixed) and the four-cone T/R element. In this system, each returning radar pulse provides target pointing information by being focused at the antenna onto a group of four-cone T/R elements. Description of the tracking process:
After pushing the „Zachvat“ button, the radar proceeds an additional search in the antenna position where the target has been found. During this additional search the scan zone shrinks to ±8º in azimuth and ±52` in elevation. If the target signal is present, the antenna performs angular tracking of the target and the radar range-finder is switched on. The range-finder searches the target in the 9km range zone. If the target is within the 9km zone, the antenna performs range tracking of the target. The SEI indicator changes its appearance. It is now showing the crosshair and the circle guidance indicator instead of selection lines (range zone). The radar is tracking the target. The tracking principle is based on summing the elevation, azimuth and the reference signal taken from the 4-cone receiver.The Sapfir-23E radar is linked with following other systems.
-the IRST sensor TP-23-1
-the analogue computer AVM-23
-the indicator SEI
-the optical gun-sight ASP-23DE
-the gun camera PAU-473-2
-the radar emission receiver SPO-10
-the IFF system SRZO-2M
-the transponder SO-69 (SOD-57)
-the short range navigation system RSBN-6S
-the radio-telemetric system ARL-SM
-the autopilot SAU-23A
-the gyro-platform SKV-2N-2
-the radio altimeter RV-4A
-the angle of attack probe DUA-3M
-the angle of slide probe DUS-3-1
-the true air-speed probe DVS-7 (DVS-10)
-the barometric altitude probe DV-30
-the SARH missile with the RGS-23 and the coupling block "RBS"
-the IR guided missile with the TGS-23 and the coupling block "TBS"
-the A2G radio-commanded missile CH-23M with pod "DELTA NG"Basic data of the Sapfir-23E system.
The S-23E radar contains of 46 parts weighting total 641kg. Main parts:
The two-mirror cassegrain antenna: 78kg
Impulse transmitter: 160kg
KNP transmitter: 160kg (continuous wave illuminator for the R-23R)
AVM-23 analog computer: 10.2kg
Radar max. scan limits in azimuth: ±52º
Radar max. scan limits in elevation: +43º, -38º
Antenna scan coverage in azimuth: ±30º
Antenna scan coverage in elevation: 8.5º to 12º
Scan cycle: 3.5sec
Pulse width: 4 or 1 µsec
Peak power of impulse transmitter: 70kW
Power output of KNP transmitter: 270W
Time to ready: 6min
Radar self check time: max. 100s
Target altitude: 40-25000m
Target speed: up to 2500km/h. 2.35M Typical range of the Sapfir-23E against fighter/bomber sized targetDetailed description of the Sapfir-23E radar modes.
The radar scan modes BSV, BSV-delta H4, BSV-delta H1, SMV, MV are switched automatically according to aircraft altitude Hs (DV-30 barometric probe) and the antenna position ”Delta H” switch. The scan mode BSV-SC can be selected manually by the pilot with the radar mode switch "BSV SC-R-BSMV switched to the BSV-SC position.
e.g. the aircraft is flying with its nose below the horizon (descending), but the antenna bearing is above the horizon. At altitude of 1500m the BSV mode changes to SMV automatically. If the antenna bearing is below the horizon at the same conditions (descend flight), at altitude of 1500m the BSV-deltaH1 mode switches to the MV automatically and vice-versa.
The BSV-SC mode hasn’t altitude limitations, the delta H switch doesn’t have an effect on it.
When the switch NAVED AVT/RUCHN is set to AVT, the radar mode selection is done automatically by the GCI datalink (ARL-SM). The radar scan patterns under GCI are better optimized due to known PPS/ZPS aspect. The one-way commands from GCI are displayed on special symbol indicator mounted on the ASP-23DE gunsight. Pilot can interrupt the GCI datalink anytime setting the switch to RUCHN. The S-23E modes operating conditions. The mode BSV
for high/medium altitudes and all-aspect intercepts, to engage targets flying higher than the Mig-23. (Hc>Hs), pulse width ~4 µsec(search), pulse width ~1 µsec(track), PRF 1Khz, Beam width in search 2,5°. Indicated range scale on SEI is 60km(search), indicated range scale on SEI is 30km(track). The maximal target altitude surplus is 6km. (delta H switch).The mode BSV-delta H4
uses one half of the PRF compared to the BSV mode. The mode BSV-delta H4 for high/medium altitudes, rear-aspect intercepts, to engage targets flying lower than the Mig-23 on the earth background (LD/SD mode) (Hc<Hs). Pulse width ~4 µsec(search), pulse width ~1 µsec(track), Beam width 2,5°(search). The max. altitude deficit of the target is -4km. (delta H switch).The mode BSV-delta H1
differs to the BSV-deltaH4 by using the pulse width of 1 µsec (search, track). The mode BSV-delta H1 for high/medium altitudes, rear-aspect intercepts, This mode is used to engage targets flying lower than the Mig-23 on the earth background (LD/SD mode) (Hc<Hs). The signal is further processed, filtered out in the “differential clutter filter” (DKP) The SMV mode
for medium/low altitudes and all-aspect intercepts, to engage targets flying higher than the Mig-23. (Hc>Hs). Indicated range scale on SEI is 30km(search, track). The pulse width of ~1 µsec(search, track)The MV mode
is used to engage targets flying lower than the Mig-23 on the earth background. (LD/SD mode) (Hc<Hs). It`s used only for rear-aspect intercepts, pulse width ~1 µsec(search, track), Beam width in search 1,5°. The MV mode uses the „SDC with external coherence“ technique to compare Doppler shifts between the target and earth background. The antenna scan zone is locked in azimuth and elevation. The BSV-SC mode
is for high/medium altitudes and all-aspect intercepts, to engage targets flying higher than the Mig-23. (Hc>Hs) . The radar mode exploits the same form of doppler processing of the received signal as in the MV mode, but on the background of radio-reflective clouds. The antenna scan zone isn`t locked as in the MV mode.
(Hs- altitude of the Mig-23, Hc- target altitude) The Sapfir-23E controls and others in the cockpit of the Mig-23MF.The panel "Block34" contains:
The main radar operating switch "BSV-SC-R-BSMV"
chooses between two radar main operating modes. The position BSMV switches among BSV, BSV-H4, BSV-H1, SMV and MV. In the BSV-SC position the radar switches between the BSV-SC and MV modes
switch has 5 operating modes. „R, T-R, T, T-phi0, NAV.
mode determines the onboard radar as a main targeting system. Also during ground attack the radar can measure distance to the target.
mode means cooperation between the radar and the IRST, if the radar is jammed the IRST can pick up the target distance and vice-versa.
mode prioritizes the IRST as a main targeting system. Also this mode is used in case of radar damage or hidden approach. The S-23E radar works in so called quasi-scan mode. The radar antenna is slaved to IRST sensor and is providing the data for the launch of R-23T.
In the „T-phi0“
mode the R-23T missile seeker is caged to the axis of the plane.
mode is for navigation flights under RSBN, or “return to base” command (VOZVRAT). The HUD display is showing “K”(curse), “G”(inclination) symbols, which the pilot has to follow.
The switch IZL-EKV-VYK
impulse transmitter (emit/equivalent/off)
The switch NAVED-AVT-RUCHN
, the instrument guiding by datalink ARL-SM on/off
The switch MSKC-PPS-ZPS
, low-speed target engagements (<500km/h)/front/rear hemisphere. If no jamming occurs, the MSKC switch position allows the radar to detect targets with any closure speeds. The panel „Block95„ contains the one-way command symbol indicator on the gunsight ASP-23DEK
- ASP-23DE self control indicatorPPS
- front hemisphere intercept AVT
-the radar range-finder is automatically controlled by ARL-SM 100,60,30
- range to target F
- afterburner ignite <
- target on left I
- target straight >
- target on right !
- target changeA
- the „zachvat“ command.G
- the “Gorka” maneuverPR
- the „Pusk razreshen“ commandT
- end of interception, return to base, OT
- the „Otvorot“ –„break-away“ commandPD
- radar range-finder malfunction K
- ASP self control system The panel „Block24„
The switch “STROB/VYKL”
. In the position “STROB”, target selection impulses (lines) for the RL are generated on the SEI. In the position “VYK”, target selection impulses (lines) for the IRST are generated.
The potentiometer “US T”
: amplifies video-signal from the IRST, used when jamming is encountered.
The potentiometer “US ”
: amplifies radar signal in the “BSV-delta H, MV” used when jamming is encountered.
The potentiometer switch “delta H”
: antenna scan zone presets in elevation(+6km/-4km), The antenna scan zone/radar range-finder is also controlled through the potentiometer located on the „POM“ throttle
The joystick/switch “ZONA R ,STROB T, SBROS”
controls radar scan zone in azimuth, controls target selection impulses (lines) for IRST in azimuth and elevation. The SBROS switch position is used to cancel the RL and the IRST lock.
The switch APKH/PPKH
serves to switch-on the radar protective circuits against active/passive jamming. The panel „Block75“
The Switch „VYKL, 3, 1, 2, 4“
is used to select the IR missile (R-13M, R-3S) carried on the pylon which locked-on the target. The pilot has to switch the proper position after the „PR“ command is shown on the SEI and pilot hears the beep tone.
The LITERA S-23
switch with positions 1,2,3,4 is located on the right vertical console. It is dedicated to switch one of four radar pulse repetition frequencies. During a formation flight by using radar modes the pilot has to switch one of the LITERA frequencies to prevent mutual radar interferences. In the MV radar mode the switch is deactivated. The switch also determines the total number of aircrafts operating in the group with radars activated.
The OKHLAZH RLS
switch activates liquid cooling of the radar during ground tests. The switch should be OFF in the flight.Detail description of the lookdown/shootdown capability of the S-23E.1.
When the MV radar mode has been selected, the returned signal is further processed in the Pulse-doppler channel of the Sapfir-23E. At first the signal is led to the linear receiver, where it is amplified and sorted out by the amplitude detector. Then it is routed to the 49 multi-channels Doppler filter (a comb filter), where the selection of moving target takes place.
The doppler shift of the radar is given by:
Fpd= Fd-nxFp =2x(Vr/c)xFo-nxFp
Fpd-doppler shift of pulse radar
Fd-doppler shift cw radar
c- speed of light
Vr-radial velocity component
Fo-source signal frequency of pulses
Fp-pulse repetition frequency
n-integer from 0 to infinite
If the pulse repetition frequency „Fp“and the source signal frequency „Fo“ is constant, the amount of doppler shift depends only by the component of radial velocity. Considering that the radial velocity can change in a wide range, the doppler shift of the clutter (earth background) is taken as a reference (coherent) signal to process the doppler filtering. Therefore the filtering technique itself is called the „СДЦ (селекции движущихся целей с внешней когерентностью)“- The moving target selection with external coherence.
Then the doppler shift of the radar is given by:
Fdc- doppler shift of the clutter
Fdt- doppler shift of the target
Vrc- radial velocity of the clutter
Vrt- radial velocity of the target
There are operational limitations such as limitations upon altitude of use or so-called blind-speeds. To operate correctly the SDC with external coherence technique needs to synchronize the target signal with the clutter phase. To simplify this task, the clutter signal received by the radar sidelobes in the second/third scan cycle is used to process the doppler filter.
To deal with the “blind speeds” the radar is changing the pulse repetition frequency during each scan line. More than 90% of “blind speeds” are covered, what ensures sufficient target detection.2.
At higher altitudes the SDC with external coherence technique becomes ineffective, the radar uses the BSV-deltaH1 and the BSV-delta H4 mode. Both the BSV-deltaH modes use a technique called the Single-beam space-time selection
. This filtering technique makes use of the difference between the spatial target location and the earth surface segment illuminated, which distances to the radar are the same. By utilizing the antenna high spatial selectivity it is possible to separate the target signal from the clutter. The advantages over the SDC with external coherence technique are no limitations in scanned sector and the target heading. Its disadvantage is the strong relationship between detection range and the target altitude. Lower target altitude means smaller detection range. The detection range equals:
D =k x Hc (km)
D- detection range
k- coefficient given by the antenna directivity pattern, characteristics of the surface background, target RCS and the surplus altitude over the target.
Hc- target altitude.
When illuminating the surface by a high directive antenna, the returned signal from the earth comes a bit later compared to the target signal. Then it is possible to separate the target signal from the clutter by using common methods of processing. The power of the clutter signal depends on the distance to the earth by a given antenna bearing as shown on the picture.
There are three specific regions.
-The first sector is evoked by the antenna sidelobes, which receive signals directly from beneath the plane. It is also here possible to separate the target signal from the clutter, because the target signal coming from the mainlobe uses to be stronger compared to the clutter signal coming from the sidelobes.
-In the second region the ground clutter can be filtered out easily, the power of the target signal greatly exceeds the clutter received by radar mainlobe.
-In the third region the ground clutter exceeds the target signal due to strong ground echoes received by the mainlobe. There is no possibility to detect the target signal.
The radar suffers from the clutter even more by illuminating the surface at very low elevation angles. Using of the high directive antenna will result in intense backscattering, the ground clutter increase in beam width. To filter the ground clutter the BSV- delta H1 mode uses the DKP „the differential clutter filter“ which processes the return signal further. The DKP filter operates only while the target is tracked in the BSV-delta H1 mode. The S-23E cooling system
The high-power transmitters (klystron tubes) are cooled by “closed cycle” liquid system. The working temperature of the liquid “antifriz 65” is +55°C. The cooling system is engaged immediately after the radar is switched on. The front radar bay is cooled with “ram” air. The flow volume is 650-800kg/h. The air-cooling system maintains operating temperature of 55-60°C inside the radar bay. If the temperature exceeds limit, the cooling slots are closed.