Honeywell XK516D1 Maintenance Manual page 53

2 IF Processor, A12
All settings of the IF processor are made via the bidirectional EXTERNAL DATA
bus (16 bit, 3 addresses). The tristate modules, A12D15, D16, D17, and D18,
permit access to the bus; addressing is effected by MS2.
Module, A12D1, is initiatized after Power Up Reset. The basic setting and main
program are located in EPROM, A12D5. The pulse for the signal processor is
generated by a 25MHz crystal, A12B1, independent of the system clock.
While operating, the processor accesses external RAM, A12D2, D3, and D4.
The output signal is output to D/A converters, D7 and D8, via latches, A12D8,
D9, and D11.
The 2nd IF signal is digitized in A/D converter, D9. To do this, the converter re-
quires an input pulse (CLKIN) of 8MHz and a phase-locked 100kHz frame sig-
nal, corresponding to the scanning rate. D9 generates a serial data flow (SDA-
TA) and the associated output pulse (SCLK).
The necessary reference voltage of 4.5V is supplied by N2-B. After Pouer Up
Reset, D9 takes about 1.3s to perform internal calibrations.
3 Functional Description SSB Receive Mode
IF selection stage with 2 different bandwidths, depending upon whether the
VOICE or DATA mode is active. The IF filters are linear phase (FIR) filters with-
out delay distortion.
Automatic gain control (AGC) stage with a volume range of 90dB and negligible
residual control error. It is composed of a backwards-acting regulator with peak
rectifying. The up-, down-, and hold-times are adjusted to match the operating
mode concerned (voice/data). The high volume range of the IF stage is
achieved owing to the 16-bit A/D converter and the 24-bit fixed-point arithmetic
of the signal processor.
BFO, which converts the filtered and regulated IF signal to the correct LF posi-
tion. This synchronous demodulator can select the upper or lower sideband
(USB/LSB) as requi red.
On request, a squelch function can be connected. This is a combined control
voltage/syllable squelch, whereby the input level, from which the signal at the
audio output is to be penetrated, has a setting range of 16 steps. If the algorithm
recognizes syllable, and the set control voltage is exceeded, the squelch is ac-
tivated and retained for about 0.5s. This condition is also displayed on the RTR
line. The squelch function is not available with the data mode.
The audio output can also be disabled by an externally-supplied signal, RECM
(except to internal LF blocking). The level at this output can be adjusted from –
20dBm to +10dBm/600
4 Functional Description AM Receive Mode
An IF selection, composed of a center-symmetrical Linear phase (FIR) filter.
Automatic Gain Control (AGC) stage with a volume range of 90dB. For control
purposes, the carrier is filtered out from the incoming composite signal, its level
is determined, and the incoming signal is amplified according to this level value.
I.B.1516A
Honeywell
COMPONENT MAINTENANCE MANUAL
PART NUMBER 964-0452
Ω
by means of R181.
23-12-01
Page 41
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Mar 30/01