A cable antenna an end part of which is connected to an oscillator that supplies a high-frequency current is disclosed. The cable antenna includes: an inner conductor; an insulating layer covering the inner conductor; and an outer conductor covering the insulating layer, wherein only one exposed part is formed in a middle part of the cable antenna in a longitudinal direction, the exposed part formed by removing at least the outer conductor, a distance L between a tip end of the cable antenna and an end of the exposed part on a side closer to the tip end is an odd multiple of a quarter of a wavelength λ of the high-frequency current, the multiplier being three or greater, and a length G of the exposed part in the longitudinal direction satisfies the following formula (1):

$\lambda /20\le \text{G}\text{<}\lambda /4\mathrm{...}$

λ: wavelength (mm) of the high-frequency current.

Aspects of the subject disclosure may include a generator that facilitates generation of an electromagnetic wave, a core, and a waveguide that facilitates guiding the electromagnetic wave towards the core to induce a second electromagnetic wave that propagates along the core. The core and/or the waveguide can be configured to reduce radiation loss of the second electromagnetic wave, propagation loss of the second electromagnetic wave, or a combination thereof. Other embodiments are disclosed.

There is disclosed a fluid and/or material detection device (2) comprising an electromagnetic transmitter and/or receiver arrangement (4) comprising a cable (6) or transmission line that acts as an antenna (e.g., transmitter and/or receiver). The device (2) comprises a liquid level detection device and/or particulate (particulate containing fluid) detection device. At least a portion of the cable (6) is rigid/stiff, e.g., at least a portion of the cable (6) having a length of from 0.1 meters to 10 meters. The cable (6) advantageously comprises a coaxial cable or triaxial cable, a radiating cable (RC) or a leaky feeder (LF). The device (2) finds use in an enclosed structure (36), e.g., a cased borehole or well, which can be sealed or unsealed during use of the device (6). The enclosed structure (36) provides a space (34), e.g., an annulus between a production tubing and a wellbore casing or a bore of a production tubing. There is also disclosed a method of detecting and/or determination and/or measuring and/or monitoring a level and/or position of a fluid and/or material or fluid interface within the space (34), the method comprising: providing the device (2); transmitting and/or receiving an electromagnetic signal or signals from and/or at/by the device (2). The method beneficially comprises detecting, locating, establishing and/or measuring a fluid level or liquid level and/or interface of a fluid or liquid using a technique comprising: Frequency Domain Reflectometry (FDR).

Example proximity sensors are described. The proximity sensor can include a transceiver unit, and a leaky coaxial cable operably coupled to the transceiver unit. The proximity sensor described herein can be used with a steering wheel. For example, the leaky coaxial cable can be embedded in the steering wheel.

In a general aspect, a portable electronic device can include a digital display including a first electrically conductive plane. The first electrically conductive plane can be configured to neutralize electromagnetic radiation produced by the digital display. The portable electronic device can also include a data transmission device configured to transmit data by intracorporeal current. The data transmission device can include a first electrode that is configured to be capacitively coupled with a body of a user and a second electrode that includes the first electrically conductive plane. The first electrically conductive plane can be electrically coupled with an electrical ground of the data transmission device. The portable electronic device can further include a printed circuit including a second electrically conductive plane. The second electrically conductive plane can be included in the second electrode of the data transmission device.

Aspects of the subject disclosure may include, for example, a coupling device includes a circuit that receives a signal. At least one passive electrical circuit element generates an electromagnetic field in response to the signal. A portion of the electromagnetic field is guided by a surface of a transmission medium to propagate as a guided electromagnetic wave longitudinally along the transmission medium. Other embodiments are disclosed.

A wind turbine has an object position and/or speed detection device including: at least one leaky feeder, at least one electromagnetic transmitter connected to the least one leaky feeder for transmitting a first electromagnetic signal along the at least one leaky feeder towards a target object, whose position is to be detected, at least one electromagnetic receiver connected to the least one leaky feeder for receiving from the at least one leaky feeder a second electromagnetic signal, the second electromagnetic signal reflected from the target object when the first electromagnetic signal hits the target object, a processing unit connected to the electromagnetic transmitter and the electromagnetic receiver and configured to analyze the first electromagnetic signal and the second electromagnetic signal for determining the position and/or speed and/or direction and/or the size of the target object.

A communication system and method for vehicles, particularly trains, are described with the vehicle having antenna sets. Each antenna set includes a plurality of antennas mounted onto a convex-shaped vehicle roof in which an axis of one antenna set is approximately perpendicular to an axis of another antenna set and in which the antenna sets are mounted below roof level of the convex-shaped vehicle roof A switching device is operable to switch between a first antenna configuration and a second antenna configuration based on a difference in measured signal power received at the antenna sets. The first antenna configuration is associated with a first stationary communication system of the plurality of stationary communication systems and a second antenna configuration is associated with a second stationary communication system of the plurality of stationary communication systems.

Aspects of the subject disclosure may include, for example, a system for transmitting first electromagnetic waves that propagate on a surface of a component of a transit system, and receiving second electromagnetic waves that propagate on the surface of the component of the transit system. Other embodiments are disclosed.

Provided is an apparatus for detecting properties of a rotor blade of a wind turbine the apparatus including: at least one leaky feeder configured to be arranged around the tower, an electromagnetic transmitter connected to the at least one leaky feeder and configured for transmitting a first electromagnetic signal along the at least one leaky feeder, a reflector for diverting and/or focusing the first electromagnetic signal in a predetermined direction, thereby forming a reflected first electromagnetic signal, an electromagnetic receiver connected to the at least one leaky feeder and configured for receiving a second electromagnetic signal from the at least one leaky feeder, the second electromagnetic signal being reflected from the rotor blade, and a processing unit connected to the electromagnetic transmitter and the electromagnetic receiver and configured to determine the properties of the rotor blade by analysing the first electromagnetic signal and the second electromagnetic signal.