RF door activation system
The present invention provides a radio frequency (“RF”) activation system with improved operating capability and ease of installation. Improved responsiveness is provided by the receiver which determines the frame timing of incoming signals and calculates the estimated time of arrival for ensuing frames thus minimizing loss of frame synchronization problems. In one embodiment, this is accomplished by determining the time span of the frame start sequence and using this to determine the frame timing of an incoming RF signal. The receiver also makes corrections for timing errors between the receiver and transmitter by re-synchronizing the receiver with the incoming RF signal.
1. A receiver for a door activation system, the receiver having frame timing, the receiver comprising:
means for receiving an incoming RF signal;
means for determining frame timing of the incoming signal; and
means for adjusting the frame timing of the receiver to be closer to the frame timing of the incoming signal, wherein the incoming signal comprises at least a first and a second frame and wherein the means for determining frame timing of the incoming further comprises:
means for determining the time difference between the receipt of the first frame and the second frame of the incoming signal;
means for determining frame timing of the incoming signal based on the time difference;
means for determining if the time difference is valid for use in determining frame timing; and
means for rejecting non-valid time differences, such that receiver frame timing is not adjusted based on invalid time differences, and wherein the first frame and the second frame comprise a first frame start bit and a second frame start bit respectively, the first and second frame start bits each having a falling edge, and wherein the means for determining time difference between the receipt of the first frame and the second frame comprises:
means for detecting the falling edges of the first and second frame start bits, such that the time difference is determined by the time difference between detection of the falling edge of the first frame and detection of the falling edge of the second frame.
2. A receiver for a door activation system, the receiver having frame timing, the receiver comprising:
means for receiving an incoming RF signal;
means for determining frame timing of the incoming signal; and means for adjusting the frame
timing of the receiver to be closer to the frame timing of the incoming signal, wherein the incoming signal comprises a frame start bit sequence of at least two bits, the frame start bit sequence having a rising edge of a bit and a falling edge of a bit, and wherein the means for determining frame timing comprises:
means for detecting the rising edge of the frame start bit sequence;
means for detecting the falling edge of the frame start bit sequence; and
means for determining the time difference between the rising edge and the falling edge, such that the frame timing of the receiver is adjusted based on the determined time difference.
3. The receiver of claim 2 , further comprising:
means for determining if the time difference is valid for use in determining frame timing; and
means for rejecting non-valid time differences, such that receiver frame timing is not adjusted based on invalid time differences.
4. A method of frame timing calibration in a door activation system comprising the steps of:
providing an RF receiver, the receiver having frame timing;
receiving an incoming RF signal with the receiver;
determining the frame timing of the incoming signal; and
adjusting the receiver frame timing based on the frame timing of the incoming signal, wherein the incoming signal comprises a frame start sequence of at least one bit having a first rising edge, and a last falling edge and wherein the step of determining the frame timing of the incoming signal comprises the steps of:
detecting the first rising edge;
detecting the last falling edge; and
determining the time difference between the first rising edge and the last falling edge.
5. The method of claim 4 , further comprising, after the step of determining the time difference, the steps of:
determining if the time difference is valid for use in determining frame timing; and
rejecting non-valid time differences, such that receiver frame timing is not adjusted based on invalid time differences.