Patent ID: 11910322
Assignee: TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Field: Digital communication (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 0:
1. A method of operating a low-power wakeup receiver in a wireless device operative in a wireless communication network, comprising:
suspending operation of a primary receiver circuit to conserve power;
operating a limited-function, low-power wakeup receiver circuit;
receiving a wakeup signal transmitted by the network at a first frequency, the wakeup signal being transmitted using Frequency Shift Keying (FSK), wherein a state of an information bit is encoded as a positive or negative offset from the first frequency;
frequency down-converting the wake-up signal from the first frequency to a second frequency lower than the first frequency;
demodulating the received FSK wakeup signal at the second frequency using first and second matched filters in the discrete time domain, wherein the first filter is configured to detect odd numbered members of an ordered set of equidistant frequencies, and reject even numbered ones, a separation between two frequencies in the ordered set being equal to two times the offset frequency of the FSK signal, and wherein the second filter is configured to detect even numbered members of the ordered set and reject odd numbered ones, thereby recovering data modulated onto the FSK wakeup signal; and
if the demodulated data identifies the wireless device, resuming operation of the primary receiver circuit.