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The contrast between the design criteria for electrically small transmit and receive antennas is studied in this work. On the transmit side, radiation efficiency (ohmic loss plus return loss) and data throughput are critical. However, a higher impedance mismatch on the receiving front end may reduce ohmic loss and expand the frequency bandwidth. So, a calculated mismatch can be added to improve the performance of the receiving ESA by lowering the overall noise figure and widening the frequency bandwidth. These contradictory design criteria suggest utilizing separate transmit and receive antennas to improve the transmitter and receiver performances.

In this work, a parametric up-converter amplifier is introduced as a wideband impedance-matching network. Chu’s limit restricts the minimum Q-factor of unloaded small antennas. However, the practical bandwidth (BW) of small antennas is defined by their loaded Q-factor. By connecting a small antenna to an amplifier with a real input impedance that is several times greater than the radiation resistance of the antenna, we propose increasing the return loss, which leads to a reduction in the loaded Q-factor and an increase in the BW. In addition, a parametric amplifier is used because, in comparison with transistor amplifiers, it offers low-noise characteristics. The gain of the low-noise parametric amplifier compensates for the loss due to the imposed mismatch. Our simulation result shows BW improvements up to 32 times can be accomplished by trading 2 dB of noise figure (NF), compared to the 15 dB suggested by Chu’s limit for a lossy antenna.

This paper presents a new method for generating low-frequency electromagnetic waves for navigation and communication in challenging environments, such as underwater and underground. The main idea is to store magnetic energy in two different spaces using the interaction between a permanent magnet and a magnetic material. The magnetic reluctance of the medium around the permanent magnet is modulated to change the magnetic flux path. The nonlinear properties of magnetic material as a critical phenomenon are used for effective modulation. As a result, a time-variant field is generated by the modulation of the permanent magnet flux. This non-resonant time-variant characterization means that the transmitter is not bound to the fundamental limits of the antennas and can transmit higher data rates. A prototype transmitter as a prove-of-concept is designed and tested based on the proposed idea. Compared to the rotating magnet, the prototyped transmitter can modulate $50\%$ of the stored energy of the permanent magnet with much lower power consumption.

One aspect is a circuit for tuning a resonance frequency of an electrically small antenna and directly exciting the electrically small antenna. The circuit includes a first source configured for providing a constant voltage. The circuit also includes an antenna and a switched capacitor configured for being alternatively alternately coupled to the first source to be charged thereby and to the antenna for exciting the antenna. Another aspect is a transmitter for transmitting a wireless signal using an antenna without using a variable voltage source to excite the antenna. The transmitter includes a first source configured for providing a constant voltage. The transmitter further includes an antenna and a switched capacitor configured for being alternately coupled to the first source to be charged thereby and to the antenna for exciting the antenna and for tuning a resonance frequency of the antenna.

The present invention provides methods and devices to radiate wideband signals. The devices may include a tunable high Q narrowband antenna having a plurality of ports including a feed port and a tuning port as well as a tuning element coupled to the tuning port of the antenna. One or more voltage sources supply energy for radiating a radio frequency signal. A modulating signal generator may also be provided for generating a high data rate signal coupled at the tuning element for modulating the tuning element.

A circuit for tuning a resonance frequency of an electrically small antenna. The circuit includes a first source configured for providing a modulation signal, a second source configured for providing a periodic electrical signal, an antenna, and a tuning circuit configured for modulating a resonance frequency of the antenna in response to the modulation signal. The tuning circuit includes first and second capacitors that are alternately coupled to the antenna to change the resonance frequency of the antenna. The capacitor currently coupled to the antenna is decoupled from the antenna and the other capacitor is coupled to the antenna when the voltage across the capacitor currently coupled to the antenna is momentarily zero. In an exemplary embodiment, the tuning circuit comprises first and second inductors rather than capacitors. The inductors are switched into and out of the circuit when the current through the currently coupled inductor is momentarily zero.

A circuit for tuning a resonance frequency of an electrically small antenna. The circuit includes a first source configured for providing a modulation signal, a second source configured for providing a periodic electrical signal, an antenna, and a tuning circuit configured for modulating a resonance frequency of the antenna in response to the modulation signal. The tuning circuit includes first and second capacitors that are alternately coupled to the antenna to change the resonance frequency of the antenna. The capacitor currently coupled to the antenna is decoupled from the antenna and the other capacitor is coupled to the antenna when the voltage across the capacitor currently coupled to the antenna is momentarily zero. In an exemplary embodiment, the tuning circuit comprises first and second inductors rather than capacitors. The inductors are switched into and out of the circuit when the current through the currently coupled inductor is momentarily zero.

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.

The present invention provides methods and devices to radiate wideband signals. The devices may include a tunable high Q narrowband antenna having a plurality of ports including a feed port and a tuning port as well as a tuning element coupled to the tuning port of the antenna. One or more voltage sources supply energy for radiating a radio frequency signal. A modulating signal generator may also be provided for generating a high data rate signal coupled at the tuning element for modulating the tuning element.

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.

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.

A plug-and-play antenna may be used with many different types of wireless communication devices. An antenna may be coupled to an impedance tuning component and a waveform generator. A calibration control module receives radio status information, controls the waveform generator to vary a response of the antenna, and tunes the impedance tuning component to match impedances between a radio and the antenna.

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.

A plug-and-play antenna may be used with many different types of wireless communication devices. An antenna may be coupled to an impedance tuning component and a waveform generator. A calibration control module receives radio status information, controls the waveform generator to vary a response of the antenna, and tunes the impedance tuning component to match impedances between a radio and the antenna.

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.

The problem addressed in this study is how to design and test compact antenna arrays for portable Multiple-Input Multiple-Output (MIMO) transceivers.