Low power rf control system
View Patent ↗A low power rf control system includes a controller that operates at a low clock speed when an associated rf receiver is deenergized and a high clock speed when the controller energizes the receiver. The receiver can be on for a short period, off for a short period when no preamble pulses from a remote control device are received, on for a short period, and then off for a longer period until the next cycle. The receiver remains on to process a command signal when a preamble signal is detected. A DC-DC down converter can be used as a power supply for the receiver, and a SAW resonant circuit can be used as an IF oscillator for the receiver. An LC filter can be associated with the receiver for filtering the IF signal.
1. A radio-frequency (rf) control system for operating a component at least in part in response to an rf signal from a remote control device manipulable by a user, comprising:
at least one rf receiver associated with the component and configured for processing an rf signal; and
at least one controller associated with the component and controlling the receiver, wherein the controller adaptively adjusts a noise threshold above which a carrier must be detected to indicate the presence of a control signal,
wherein a slow receiver signal strength indicator (RSSI) filter and a fast RSSI filter are connected between a RSSI output of the rf receiver and inputs of the controller, a time constant of the fast RSSI filter being less than a time constant of the slow RSSI filter,
wherein the output of the fast RSSI filter is used by the controller to determine whether a carrier signal has been detected,
wherein the output of the slow RSSI filter is connected to a comparator to provide a digital signal to the controller, and
wherein the controller raises the noise threshold when the controller determines that a false carrier has been detected.
2. The system of claim 1 , wherein the slow RSSI filter is used by the controller to detect a continued presence of a signal to reduce the effect of noise.
3. The system of claim 1 , wherein the modulation of the signal is of the amplitude shift keying type.
4. The system of claim 1 , wherein the frequency of the signal is 433 MHz.
5. The system of claim 1 , wherein the time constant of the slow RSSI filter is 200 microseconds.
6. The system of claim 1 , wherein the time constant of the fast RS SI filter is 10 microseconds.
7. The system of claim 1 , wherein the controller causes the receiver to be energized for first wake-up time periods according to a wake-up paradigm of wake-up events, energization being resumed when a carrier signal is present.
8. The system of claim 7 , wherein the first wake-up time period is 80 microseconds.
9. The system of claim 1 , wherein the controller operates at a high frequency when the receiver is energized and at a low frequency during a receiver sleep period, the high frequency being greater than the low frequency.
10. The system of claim 1 , wherein the controller operates at an intermediate frequency between low and high frequencies prior to energizing the receiver after a receiver sleep period.
11. The system of claim 1 , wherein the false carrier has been detected when attempting to process a signal without successfully decoding the signal.
12. The system of claim 1 , wherein the component is powered by at least one battery.
13. The system of claim 1 , wherein the component is selected from the group of components consisting of window coverings, awnings, skylight covers, and screens.
14. The system of claim 1 , wherein the rf signal includes a preamble including plural pulses, each having a duty cycle in excess of fifty percent (50%).
15. The system of claim 14 , wherein the preamble includes at least six pulses.
16. The system of claim 1 , comprising at least one bypass capacitor electrically connected between the receiver and ground, the bypass capacitor having a capacitance of below five hundred picoFarads (500 pF).
17. The system of claim 16 , comprising plural bypass capacitors, at least one having a capacitance not substantially more than one hundred picoFarads (100 pF).
18. The system of claim 1 , comprising at least one surface acoustic wave (SAW) resonator circuit to establish an intermediate frequency (IF) oscillator for the receiver.
19. The system of claim 18 , comprising an LC filter associated with the receiver for filtering an IF signal.
20. The system of claim 1 , wherein the component is powered by at least one battery, and the system further comprises a DC-DC down converter electrically interposed between the battery and receiver to provide a voltage to the receiver.