synchronously with a recovered clock. The receiver
is designed to meet the MIL-STD-1397 Type D
requirements.
Transmission
The CT1815 accepts synchronous NRZ Data in
conjunction with two clocks signals. The NRZ data
stream is then converted to Manchester code which
is transformer coupled to a 75 ohm Tri-axial cable for
transmission up to 1000 ft.
Electrical Requirements
The specification detailed herein encompasses a
hybrid Transceiver/Encoder-Decoder designed to
meet the requirements of the MIL-STD-1397 Type D.
The transmitter may be placed into standby
condition. This reduces power consumption by
approximately 600mW. Power management is made
available via two standard TTL input pins. The
Receiver is always active and is not affected by the
power management circuitry.
The transceiver is transformer coupled to the
specified triaxial cable and is screened to the
individual test methods of MIL-STD-883
See Figure 1 for Block Diagram. Inputs and
Outputs are all Synchronous NRZ DATA STREAMS
The transceiver is matched for 75 ohm operation
over a wide band of frequencies. This condition is
maintained with power on and off.
Transformer Isolation
The CT1815 is connected with pin 3 and pin 32 to
the ACT15-1031 transformer secondary winding.
The center tap of the secondary winding is
connected to +5 volts. For matching 75Ω load
operation, a 78Ω resistor must be placed across the
primary winding of the transformer.
Reception
The CT1815 receiver section accepts a bipolar
signal which is level detected and passed to the
serial decoder. The decoder section reconstructs
the data and strips the clock from the serial stream.
An NRZ decoded data stream is then produced
Encoder Timing / Transmitter Specification
Symbol
Parameter / Condition
Encode Timing
Min
Typ
Max
Unit
t1
Input data set-up time
10
10
10
10
150
50
20
45
40
40
40
35
ns
ns
ns
ns
ns
ns
ns
ns
t2
Encode clock set-up time
Encode envelope set-up time
Encode envelope turn-off time
Transmitter activation set-up time
Transmitter deactivation hold-time
20 MHz gated CK pulse width high
Encoder shift CK pulse width high
Output Signals
t3
t4
t5
t6
tw1
tw2
30
55
Va
T
Output amplitude (see Figure 2)
Pulse period
2.75 3.25 3.75
V
ns
97
45
47
47
100
103
65
Ts
Te
Width of 1st positive half bit
Width of last half bit
ns
65
ns
T/2
Tr
Half pulse period
50
53
ns
Pulse rise time
2.0
2.0
350
150
V/ns
V/ns
mV
mV
Tf
Pulse fall time
Vs
Tos
Tdtx
Voltage overshoot
Offset Voltage 2T after last zero crossing
Delay from 20 MHz clock input to data output on
transformer secondary
20
75
55
80
ns
Zo
Output Impedance
70
Ω
2
Aeroflex Circuit Technology
SCDCT1815 REV A 6/12/98 Plainview NY (516) 694-6700
AEROFLEX [ AEROFLEX CIRCUIT TECHNOLOGY ]
