RCR-433-RP Radiotronix, RCR-433-RP Datasheet - Page 4

• Manufacturer Part Number: RCR-433-RP
• Description: RF Modules & Development Tools 433MHz Receiver Module 4800 Baud
• Manufacturer: Radiotronix

Specifications of RCR-433-RP

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RCR-XXX-RP Super-Regen ASK/OOK Receiver
Pin Description
Pin
1
2
3
4,5
6
7
8
Theory of Operation
Super-Regenerative AM Detection
The RCR-XXX-RP uses a super-regenerative AM detector to demodulate the incoming AM
carrier.
A super-regenerative detector is a gain stage with positive feedback greater than unity so that it
oscillates. An RC-time constant is included in the gain stage so that when the gain stage
oscillates, the gain will be lowered over time proportional to the RC time constant until the
oscillation eventually dies.
When the oscillation dies, the current draw of the gain stage decreases, charging the RC circuit,
increasing the gain, and ultimately the oscillation starts again. In this way, the oscillation of the
gain stage is turned on and off at a rate set by the RC time constant.
This rate is chosen to be super-audible but much lower than the main oscillation rate. Detection is
accomplished by measuring the emitter current of the gain stage. Any RF input signal at the
frequency of the main oscillation will aid the main oscillation in restarting. If the amplitude of the
RF input increases, the main oscillation will stay on for a longer period of time, and the emitter
current will be higher. Therefore, we can detect the original baseband signal by simply low-pass
filtering the emitter current.
The average emitter current is not very linear as a function of the RF input level. It exhibits a 1/ln
response because of the exponentially rising nature of oscillator start-up. The steep slope of a
logarithm near zero results in high sensitivity to small input signals.
Data Slicer
The data slicer converts the baseband analog signal from the super-regenerative detector to a
CMOS/TTL compatible output. Because the data slicer is AC coupled to the audio output, there is
a minimum data rate. AC coupling also limits the minimum and maximum pulse width.
Typically, data is encoded on the transmit side using pulse-width modulation (PWM) or non-
return-to-zero (NRZ).
The most common source for NRZ data is from a UART embedded in a micro-controller.
Applications that use NRZ data encoding typically involve microcontrollers. The most common
source for PWM data is from a remote control IC such as the HC-12E from Holtek.
Data is sent as a constant rate square-wave. The duty cycle of that square wave will generally be
either 33% (a zero) or 66% (a one). The data slicer on the RCR-XXX-RP is optimized for
use with PWM encoded data, though it will work with NRZ data if certain encoding rules are
followed.
Name
ANT
GND
GND
V
ANALOG
DATA
GND
cc
(5v)
Description
50 Ω antenna input.
Receiver Ground. Connect to ground plane.
Receiver Ground. Connect to ground plane.
Pins 4 and 5 are electrically connected and provide operating voltage for the
receiver. VCC can be applied to either or both. VCC should be bypassed with a
.01µF ceramic capacitor and filtered with a 4.7µF tantalum capacitor. Noise on
the power supply will degrade receiver sensitivity.
Analog receiver output. This is the audio signal prior to the data slicer.
Digital data output. This output is capable of driving one TTL or CMOS load. It is
a CMOS compatible output.
Receiver Ground. Connect to ground plane
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Data Sheet
2/13/2004