BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
5) Control bus manager routine determining proper control configuration. 6) Problem control manager routine programming the internal data collection parameters of the R/T.
7) Data bus formatter routine processing and assembling the 64-bit control word of the serial word sent to the indicator.
The video circuits first convert the analog video signals into a digital format. The digital video data is sent to the video processor. It adjusts the signal level with sensitivity timing control (STC). This allows nearby echo signals to be displayed with the same intensity as distant ones. STC is effective to about 70 nm. In the MAP mode, STC is modified to optimize analysis of terrain features.The video processor also adjusts the overall threshold attenuation and penetration compensation. This compensates for weakened radar returns to intervening targets. Also, the video processor determines the intensity of the weather target and stores this in the video memory. The timing and control circuits sends antenna tilt and scan angle data, selected range data, and any detected fault data to the video memory. The contents of the video memory are formatted and sent to the EFIS symbol generators (Ref 34-22-00) for display. This video memory data is transmitted about every four seconds via ARINC 453 very high speed data buses.Receiver/Transmitter Antenna Stabilization Functions 1) The R/T receives IRS pitch and roll attitude data from the
IRS No. 1 and 2. The IRS source select switch selects which IRS source is to be used by the R/T microcomputer to develop the weather radar antenna stabilization signals.
2) With the IRS source select switch in the NORMAL position, attitude data from the left inertial reference unit (IRU) is used by the receiver/transmitter. When the IRS source select switch is placed in the BOTH ON R position, the left IRU is disconnected and the right IRU is connected within the receiver/transmitter to provide attitude data.
3) Antenna TILT control changes and antenna scan and elevation monitor signals effect the antenna stabilization circuit computation in the R/T microcomputer.
4) Stabilization signals from the microcomputer are sent through the I/O ports and elevation and scan line drivers from the R/T to the antenna.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
(6) BEJ 113-999; Receiver/Transmitter Functions (Fig. 4)
(a)
The R-T unit is a lightweight airborne unit consisting of transmitter, receiver, weather processor circuits , universal input/output (I/O) circuits, system monitoring circuits, low power supply and a BITE/keep alive power supply. The weather processor circuits consist of a sampler, digital signal processor circuits (DSP) and a central processing unit (CPU). The weather data processor circuits extract data from the detected I and Q returns and prepare it for transmission to the I/O circuits and ARINC 453 line drivers.
(b)
The receiver/transmitters have predictive windshear capabilities however these circuits are not discussed below because they are inoperative. The airplane have windshear wiring provisions installed such as wires from the air traffic control and digital air data computers to the weather radar R/T's as shown in Fig 4. Most of the wiring provisions have been installed with the pin connections capped and stowed at the R/T mount connector.
(c)
RF transmission starts in the frequency source circuits of the transmitter. The frequency source develops two frequecies that are applied to the drive circuits where these signals are amplified in power and mixed to produce a single 777.77 MHz signal. This signal is then applied to the power amplifier. The power level of the 777.77 MHz drive signal is again amplified before it is applied to the frequency multiplier circuits. The drive signal after multiplcation is 9333.24 MHz in frequency and 125 watts in power.
(d)
The duplexer couples the transmitter output signal to the waveguide. The duplexer has a power monitor that checks peak power output and a phase monitor that develops a loop error signal to correct for output frequency variation and noise. The output signal is transmitted by a waveguide to the antenna and then radiated out the antenna flat plate.
