A frequency cancelling system is disclosed which improves reception of a communication signal which is transmitted at a communication frequency in the presence of an interference signal which occurs at the same communication frequency. The frequency cancelling system generates a reference signal at the communication frequency, and adjusts the reference signal to be opposite in phase and equal in amplitude to the interference signal. The reference signal and the communication signal are then combined to cancel the interference signal. In a preferred embodiment, the reference signal is generated from the same source as that from which the interference signal arises. Preferably, the interference signal is received during an interval in which the communication signal is not being transmitted, and the reference signal is adjusted to be opposite in phase and equal in amplitude to the interference signal during that interval.
Wireless remote control system for engine piston with in-piston circuit (50) and an external processing unit mounted on the exterior of the crank case (51). A carrier signal generated in the external processing unit is fed to a primary coil (P) located within the crank case and the secondary coil (S), loosely coupled to coil (P) and tuned for resonance therewith is located in the skirt of the piston. The secondary coil picks up a carrier signal from the primary coil and the carrier signal is rectified, smoothed and regulated to provide DC power to a micro controller in the piston circuit. The micro controller may use data from a number of sensors to modulate the signal in the secondary coil, which modulation is picked up by the primary coil and thus sensor data is transmitted to the external processing unit where it is filtered and decoded.
An active cancellation device receives a model of a first signal from a local wireless transmitter. The first signal causes a coupled signal that interferes in a second signal received by a local wireless receiver from a remote wireless transmitter. The active cancellation device generates a cancellation signal based on the model of the first signal, and provides the cancellation signal to the local wireless receiver. At the local wireless receiver, the cancellation signal combines with the coupled signal and the second signal. The cancellation signal reduces the interference in the second signal caused by the coupled signal.
A method and apparatus is provided for reducing or eliminating the transmitter signal leakage, i.e., transmitter noise, in the receiver path of an RF communications system operating in full duplex mode. In an embodiment of the present invention, a noise cancellation loop produces an estimated transmitter signal leakage and cancels it from the receiver path to produce a received signal with little or no transmitter noise. Some of the advantages are that there is significant improvement in the isolation between the transmitter/receiver circuits, the size of the RF communications circuitry may be reduced, and the RF transmit module along with the RF receive module may be incorporated into a single RF IC chip.
An active cancellation controller receives a signal strength indicator that indicates a power level of a coupled signal from a local wireless transmitter at a local wireless receiver. The active cancellation controller tunes an active cancellation circuit to reduce the signal strength indicator. The active cancellation circuit is to generate a cancellation signal to combine with the coupled signal at the local wireless receiver.
A detachable keyboard for a telephone set is provided in the form of a keyboard card clipped to the headset, which is completely detached from the body when unclipped. Wireless communication between the handset body and keyboard is used when the card is unclipped, while contacts are activated in the clipped position so that the wireless handset then functions as in the case of a non detachable keyboard.
