26-02-2013, 02:58 PM
433 MHz RF Receiver STR-433
[attachment=51925]
INTRODUCTION
The STR-433 is ideal for short-range remote control applications where cost is a primary concern. The receiver module requires no external RF components except for the antenna. It generates virtually no emissions, making FCC and ETSI approvals easy. The super-generative design exhibits exceptional sensitivity at a very low cost. The manufacturing-friendly SIP style package and low cost make the STR-433 suitable for high volume applications.
Features –
• Low cost.
• 5v operation.
• 3.5 mA current gain.
• No external parts are required.
• Receiver frequency- 433.92 MHz.
• Typical Sensitivity -1.5 dBm.
• IF Frequency -1 MHz.
Applications –
• Car Security System.
• Sensor Reporting.
• Automation System.
• Remote Keyless Entry.
• Remote Lighting Controls.
• Onsite Paging.
• Asset Tracking.
• Wireless Alarms and Security Systems.
• Long Range.
• Automated Resource Management.
Operation –
The STR-433 uses a super-regenerative AM detector to modulate the incoming AM carrier. A super generative 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 eventually 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 base-band signal by simply low pass filtering the emitter current.
The average emitter current is not very linear as a function of RF input level. It exhibits the 1/ln response because of the exponentially rising nature of oscillator start up. The steep slop of the logarithm near zero results in high sensitivity to small input signals.
[attachment=51925]
INTRODUCTION
The STR-433 is ideal for short-range remote control applications where cost is a primary concern. The receiver module requires no external RF components except for the antenna. It generates virtually no emissions, making FCC and ETSI approvals easy. The super-generative design exhibits exceptional sensitivity at a very low cost. The manufacturing-friendly SIP style package and low cost make the STR-433 suitable for high volume applications.
Features –
• Low cost.
• 5v operation.
• 3.5 mA current gain.
• No external parts are required.
• Receiver frequency- 433.92 MHz.
• Typical Sensitivity -1.5 dBm.
• IF Frequency -1 MHz.
Applications –
• Car Security System.
• Sensor Reporting.
• Automation System.
• Remote Keyless Entry.
• Remote Lighting Controls.
• Onsite Paging.
• Asset Tracking.
• Wireless Alarms and Security Systems.
• Long Range.
• Automated Resource Management.
Operation –
The STR-433 uses a super-regenerative AM detector to modulate the incoming AM carrier. A super generative 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 eventually 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 base-band signal by simply low pass filtering the emitter current.
The average emitter current is not very linear as a function of RF input level. It exhibits the 1/ln response because of the exponentially rising nature of oscillator start up. The steep slop of the logarithm near zero results in high sensitivity to small input signals.