An antenna structure includes a main antenna, a parasitic antenna, a matching circuit and a switching circuit. The main antenna includes a feeding strip and a first radiating strip coupled to the feeding strip. The parasitic antenna includes a grounding strip and a second radiating strip coupled to the grounding strip. The second radiating strip is positioned adjacent to and apart from the first radiating strip, and further configured to electromagnetically couple to and be parasitically fed by the first radiating strip. The parasitic antenna and main antenna cooperatively generate at least one high-frequency resonate mode and a low-frequency resonate mode. The matching circuit is electronically coupled to the feeding strip. The switching circuit is electronically coupled to the matching circuit, and configured to regulate an inductance value of the matching circuit output to the feeding strip, thereby regulating a central frequency of the low-frequency resonate mode.

A radio frequency device with mechanisms for adjustment of the impedances and frequencies of its antennas comprises a first circuit board, a radio frequency module and a second circuit board. The radio frequency module is disposed on the first circuit board that is disposed on the second circuit board. The radio frequency module comprises an antenna unit, a first frequency tuning element and a radio frequency circuitry. The antenna unit is disposed within a clearance area of the first circuit board, and connected to the radio frequency circuitry via a feeding circuit. The second circuit board comprises a second frequency tuning element that is electrically connected to the antenna unit via a ground circuit and the first frequency tuning element on the first circuit board. Thus, the resonance frequency of the antenna unit can be adjusted according to the first and the second frequency tuning element.

A radio frequency device with mechanisms for adjustment of the impedances and frequencies of its antennas comprises a first circuit board, a radio frequency module and a second circuit board. The radio frequency module is disposed on the first circuit board that is disposed on the second circuit board. The radio frequency module comprises an antenna unit, a first frequency tuning element and a radio frequency circuitry. The antenna unit is disposed within a clearance area of the first circuit board, and connected to the radio frequency circuitry via a feeding circuit. The second circuit board comprises a second frequency tuning element that is electrically connected to the antenna unit via a ground circuit and the first frequency tuning element on the first circuit board. Thus, the resonance frequency of the antenna unit can be adjusted according to the first and the second frequency tuning element.

Generally discussed herein are techniques, software, apparatuses, and systems configured for tuning an antenna. In one or more embodiments, a system can include a monopole or dipole antenna, a hardware processor electrically coupled to the monopole or dipole antenna, an amplitude or power detector electrically coupled between the monopole or dipole antenna and the processor to receive signals reflected from the monopole or dipole antenna and determine an amplitude or power of the reflected signals, and a first impedance matching network electrically connected between a feed point of the monopole or dipole antenna and the detector, the first impedance matching network including a variable capacitor, the variable capacitor having a variable capacitance that is set by the hardware processor based on the amplitude or power of the reflected determined by the amplitude or power detector.

There is disclosed a multiband antenna device comprising a conductive elongated antenna element configured for electrical connection to a conductive groundplane at a grounding point, and for electrical connection to a radio transmitter/receiver at a feeding point. The antenna element comprises a first portion and a second portion. The first portion is configured to extend in a first direction along a first outside edge of the groundplane, and then in a second direction along a second outside edge of the groundplane. The second portion of the antenna element is configured to double back next to the first portion in a third, substantially counter-parallel direction back along the second outside edge of the groundplane, and then in a fourth direction along the first outside edge of the groundplane. The second portion of the antenna element terminates with a high impedance portion, and the high impedance portion of the antenna element is positioned between the first edge of the ground plane and the first portion of the antenna element so as to form a narrow gap that electromagnetically couples the first and second portions of the antenna element.

There is disclosed a multiband antenna device comprising a conductive elongated antenna element configured for electrical connection to a conductive groundplane at a grounding point, and for electrical connection to a radio transmitter/receiver at a feeding point. The antenna element comprises a first portion and a second portion. The first portion is configured to extend in a first direction along a first outside edge of the groundplane, and then in a second direction along a second outside edge of the groundplane. The second portion of the antenna element is configured to double back next to the first portion in a third, substantially counter-parallel direction back along the second outside edge of the groundplane, and then in a fourth direction along the first outside edge of the groundplane. The second portion of the antenna element terminates with a high impedance portion, and the high impedance portion of the antenna element is positioned between the first edge of the ground plane and the first portion of the antenna element so as to form a narrow gap that electromagnetically couples the first and second portions of the antenna element.

A passive radio frequency identification (RFID) sensor is provided. This passive RFID sensor includes at least one antenna, at least one processing module, and a wireless communication module. The at least one antenna has an impedance that may vary with an environment in which the sensor is placed. Additionally, the antenna impedance might be permanently changed in response to an environmental variation or an event. The at least one processing module couples to the antenna and has a tuning module that may vary a reactive component impedance coupled to the antenna in order to change a system impedance. The system impedance includes both the antenna impedance and the reactive component impedance. The tuning module then produces an impedance value representative of the reactive component impedance. A memory module may store the impedance value which may then later be communicated to an RFID reader via the wireless communication module. The RFID reader may then exchange the impedance value representative of the reactive components of impedance with the RFID reader such that the RFID reader or another external processing unit may process the impedance value in order to determine environmental conditions at the inductive loop. These environmental conditions may include but are not limited to temperature, humidity, wetness, or proximity of the RFID reader to the passive RFID sensor.

Embodiments of the present disclosure describe methods, apparatuses, and systems related to a wireless communication device using time-variant antenna. Other embodiments may be described and/or claimed.

Embodiments of the present disclosure describe methods, apparatuses, and systems related to a wireless communication device using time-variant antenna. Other embodiments may be described and/or claimed.

An antenna device includes an antenna element, which is able to transmit and receive high-frequency signals of a plurality of frequency bands, and an antenna matching circuit. The antenna matching circuit includes an impedance converting circuit, which is connected to the antenna element side of the circuit, and a variable reactance circuit, which is connected to a feeder circuit side of the circuit. The impedance converting circuit includes a first inductance element and a second inductance element, which are transformer coupled with each other. The variable reactance circuit includes a reactance element, which is connected in parallel or series with the transmission/reception signal transmission path, and a switch that switches the connection state of the reactance element.