RCT-XXX-AS
Low-Cost SAW-stabilized surface mount OOK RF transmitter
© 2001,2002,2003 All Rights Reserved
Detailed Electrical Specifications
Parameter (General)
Symbol
Min
Typ.
Max
Units
Notes
Operating Voltage
Vcc
1.5
3.0
12
Volts DC
Operating Current
DATA=VCC
Icc
---
4.5
---
mA
@3V
Operating Current
DATA=GND
Icc
---
100
---
uA
@3V
Frequency Accuracy
TOLfc
-75
0
+75
Khz
@3V
Center Frequency
Fc
---
315.0
418.0
433.92
---
MHz
RCT-315-AS
RCT-418-AS
RCT-433-AS
Output Power
---
0
dBm
@3V
Baud Rate – NRZ
DC
---
4800
BPS
Theory of Operation
OOK Modulation
OOK modulation is a binary form of amplitude modulation. When a logical 0 (data line low) is
being sent, the transmitter is off, fully suppressing the carrier. In this state, the transmitter current
is very low, less than 1mA.
When a logical 1 is being sent, the carrier is fully on. In this state, the module current
consumption is at its highest, about 4.5mA with a 3V power supply.
OOK is the modulation method of choice for remote control applications where power
consumption and cost are the primary factors. Because OOK transmitters draw no power when
they transmit a 0, they exhibit significantly better power consumption than FSK transmitters.
OOK data rate is limited by the start-up time of the oscillator. High-Q oscillators which have very
stable center frequencies take longer to start-up than low-Q oscillators. The start-up time of the
oscillator determines the maximum data rate that the transmitter can send.
DESIGN HINT “Using the RCT-XXX-AS with a microcontroller UART”: Data should be
inverted when using the transmitter with a UART. The normal marking state of a UART is a logic
1, which will cause constant transmission. By inverting the data, the transmitter will be off in a
marking state and on in a spacing state (logical 0), ensuring that the transmitter is on only when
data is being sent. The output of the receiver would also need to be inverted to properly recover
data.
SAW stabilized oscillator
The transmitter is basically a negative resistance LC oscillator whose center frequency is tightly
controlled by a SAW resonator. SAW (Surface Acoustic Wave) resonators are fundamental
frequency devices that resonate at frequencies much higher than crystals.
- 3 -
8/21/2003
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