A battery-less Internet of things (IoT) tag integrated with a proximity sensor is disclosed. The battery-less IoT tag includes: a transmit antenna designed to have an inductive element; an integrated circuit having a capacitive element; and an energy harvester coupled to a capacitor, wherein the capacitor is an on-die capacitor and the energy harvester is configured to harvest energy from ambient signals, wherein the inductive element and the capacitive element form the proximity sensor oscillating at a local oscillator (LO) frequency, and wherein a frequency offset from the LO frequency is indicative of a detection of a nearby object.

A battery-less Interest of things (IoT) tag integrated with a proximity sensor is disclosed. The battery-less IoT tag includes: a transmit antenna designed to have an inductive element; an integrated circuit having a capacitive element; and an energy harvester coupled to a capacitor, wherein the capacitor is an on-die capacitor and the harvester is configured to harvest energy from ambient signals, wherein the inductive element and the capacitive element form the proximity sensor oscillating at a local oscillator (LO) frequency, and wherein a frequency offset from the LO frequency is indicative of a detection of a nearby object.

A local oscillator frequency-based proximity sensor is disclosed. The proximity sensor includes: an integrated circuit having at least a capacitive element; and an antenna designed with an inductive element; wherein the capacitive element and the inductive element form a proximity sensor oscillating at a local oscillator (LO) frequency, wherein the integrated circuit is configured to measure a frequency offset from the LO frequency, wherein the frequency offset is indicative of a detection of a nearby object.

Aspects of the present disclosure provide a low power differential frequency multiplier. An example frequency multiplier circuit generally includes a first set of transistors, a second set of transistors, and a resonant circuit. The first set of transistors comprises a first transistor and a second transistor, wherein each of the transistors in the first set is a first type of transistor. The second set of transistors comprises a third transistor and a fourth transistor, wherein each of the transistors in the second set is a second type of transistor. The resonant circuit has a first terminal coupled to the first set of transistors and a second terminal coupled to the second set of transistors, wherein the resonant circuit comprises an inductive element and a capacitive element coupled in parallel with the inductive element.

A local oscillator frequency-based proximity sensor is disclosed. The proximity sensor includes: an integrated circuit having at least a capacitive element; and an antenna designed with an inductive element; wherein the capacitive element and the inductive element form a proximity sensor oscillating at a local oscillator (LO) frequency, wherein the integrated circuit is configured to measure a frequency offset from the LO frequency, wherein the frequency offset is indicative of a detection of a nearby object.