WAZIPOINT Engineering Science & Technology: Leaky Coaxial Cables Using Purpose

Monday, June 5, 2023

Leaky Coaxial Cables Using Purpose

 What is Leaky Cable or a Leaky Feeder?

A leaky feeder is a communications system used in underground mining and other tunnel environments. The layman's term "leaky feeder" implies that the cable is in some way deficient. The external conductor is processed to create a signal leakage slot so the cable functions as the antenna. 

Manufacturers and cabling professionals use the term "radiating cable" or leaky cable as this implies that the cable is designed to radiate: something that coaxial cable is not generally supposed to do.

Leaky Cable Specifications Selection Criteria

Leaky cables have specific specifications that are designed to meet the requirements of their intended applications. Here are some common specifications of leaky cables:

Frequency Range of Leaky Cable: Leaky cables are designed to operate within a specific frequency range. The frequency range is determined based on the application requirements, such as wireless communication bands or radar frequencies. The frequency range should be specified to ensure compatibility with the intended system.

Leakage Characteristics fo Leaky Cable: The leakage characteristics of a leaky cable define the amount of electromagnetic energy that is radiated or leaked along its length. These characteristics include the distribution and intensity of the leakage. The leakage pattern can be controlled by the placement, size, and shape of slots or apertures along the cable.

Attenuation of Leaky Cable: Leaky cables have a specified attenuation rate, which indicates the amount of signal loss along the cable. The attenuation is typically given in decibels per meter (dB/m) and depends on the cable construction, materials used, and frequency range. Lower attenuation values are desirable to ensure efficient signal propagation.

Power Handling Capacity of Leaky Cable: The power handling capacity of a leaky cable specifies the maximum power level that the cable can safely handle without distortion or damage. It is crucial to ensure that the power transmitted through the cable remains within the specified limits to maintain system integrity and prevent signal degradation.

Leaky Cable Construction: Leaky cables come in various constructions, including coaxial, twin-lead, or microstrip designs. The choice of cable construction depends on factors such as the application, frequency range, power requirements, and environmental considerations. The cable construction affects factors like impedance, flexibility, and mechanical durability.

Connectors for Leaky Cable: Leaky cables are typically equipped with connectors at the ends to facilitate easy installation and connection to other system components. The type of connectors used can vary depending on the application and the system requirements. Common connector types include SMA, N-type, or BNC connectors.

These specifications may vary depending on the manufacturer, specific application, and industry standards. It is important to consult the documentation provided by the manufacturer or supplier to ensure that the leaky cable meets the required specifications for your particular application.

Purposes of leaky Cables or Leaky Conductors

Leaky cables or leaky conductors are suitable for wireless communication in narrow or long, curvy surroundings, such as in buildings, tunnels, subways, high-speed trains, etc. FM, DMB, LTE-R, mobile communication services, etc.

Leaky cables or leaky conductors are specialized types of transmission lines used in various applications. They are designed to intentionally radiate or leak electromagnetic energy along their length. Here are some purposes and applications of leaky cables:

Wireless Communication: Leaky cables are often used as radiating elements in distributed antenna systems (DAS) or leaky feeder systems. These systems are commonly employed in large buildings, tunnels, or underground mines to enhance wireless communication coverage. The leaky cables radiate the signal along their length, providing consistent coverage throughout the designated area.

Microwave and Radar Systems: Leaky cables are utilized in microwave and radar systems to achieve specific radiation patterns. By controlling the geometry and arrangement of the leakage slots or apertures, leaky cables can be tailored to produce desired radiation characteristics, such as beam shaping or beam steering.

Microwave Heating: In certain industrial applications, leaky cables are employed for microwave heating purposes. By allowing controlled energy leakage, they can distribute microwave energy more uniformly within a target material. This technique finds use in processes like drying, curing, and food processing.

Remote Sensing: Leaky cables can be utilized as part of a sensor system for remote sensing applications. Information about the environment or objects surrounding the cable can be obtained by measuring the leakage or radiation patterns. This technique is employed in perimeter security systems or environmental monitoring applications.

Antenna Systems: Leaky cables can be used as part of antenna systems for specific applications. They can act as radiating elements or as part of an antenna array, providing directional radiation patterns or specific coverage characteristics.

It's important to note that the purpose and design of leaky cables depend on the specific application requirements. The leakage properties, such as the location and size of slots or apertures, are carefully engineered to achieve the desired functionality.

Main Functions of Leaky Cables

The main functions of leaky cables or leaky conductors are as below:

  1. Low loss through high-foam insulation;
  2. Design of damping and combined loss properties according to frequency is feasible;
  3. 90° or 180° slots according to installation location (tunnel wall, central pillar).
Leaky cables, also known as leaky feeders or radiating cables, serve several important functions in various applications. Here are the main functions of leaky cables:

Signal Distribution: One of the primary functions of leaky cables is to distribute signals over a large area. They are commonly used in wireless communication systems, such as distributed antenna systems (DAS), to provide consistent coverage in environments where traditional antennas may not be sufficient. Leaky cables radiate or leak signals along their length, ensuring that the signals reach all desired locations within the coverage area.

Signal Radiation: Leaky cables are designed to intentionally radiate or leak electromagnetic energy. This radiation allows them to act as low-gain antennas, emitting signals into the surrounding environment. By controlling the leakage properties, such as the position and size of slots or apertures, leaky cables can produce specific radiation patterns. This function is valuable in applications requiring directional or controlled radiation, such as radar systems or antenna arrays.

Wireless Connectivity: Leaky cables enable wireless connectivity in areas with challenging propagation conditions. They are often deployed in environments with obstacles, such as tunnels, underground mines, or large buildings, where radio signals may struggle to penetrate. By strategically installing leaky cables, wireless communication signals can be propagated more effectively, enhancing connectivity and coverage.

Microwave Heating and Drying: In industrial applications, leaky cables are employed for microwave heating and drying processes. By allowing controlled energy leakage, they enable uniform distribution of microwave energy within a target material. This function is utilized in various processes, including drying textiles, curing coatings, or heating food products.

Sensing and Monitoring: Leaky cables can also serve as part of sensing or monitoring systems. By measuring the leakage or radiation patterns, information about the surrounding environment or objects can be obtained. This functionality finds applications in areas such as perimeter security systems, environmental monitoring, or object detection.

What is MIMO Leaky Cables?

MIMO is short for Multi-In, Multi-Out, The MIMO construction of leaky cables functions as reducing CAPEX such as construction and material costs.

The feature of MIMO leaky conductors are as below:

  1. Exclusive for LTE-R (700MHz) (FM, DMB, LTE-R);
  2. Exclusive for mobile communication services (800MHz~2.3GHz);
  3. Hybrid Combiner: Bi-directional power feed components for MIMO functions.

MIMO (Multiple Input Multiple Output) leaky cables refer to a technology that combines the benefits of MIMO and leaky cable systems. MIMO is a wireless communication technology that uses multiple antennas at both the transmitter and receiver to improve system performance by increasing data throughput, enhancing reliability, and mitigating interference.

In the context of leaky cables, MIMO technology is implemented by utilizing multiple leaky cables with multiple antennas. The leaky cables act as radiating elements, and each cable is associated with one or more antennas. The antennas are strategically positioned along the length of the cables.

The main purpose of MIMO leaky cables is to enhance wireless communication performance in terms of coverage, capacity, and reliability. By employing multiple leaky cables with multiple antennas, MIMO techniques can be leveraged to achieve spatial multiplexing, spatial diversity, or beamforming.

Spatial Multiplexing: In spatial multiplexing, multiple independent data streams are transmitted simultaneously using different antennas. Each leaky cable, with its associated antenna, serves as an independent transmission channel. This increases the overall data throughput and capacity of the system.

Spatial Diversity: Spatial diversity exploits the fact that signals from different antennas experience independent fading or interference. By combining signals received from multiple antennas, the system can mitigate the adverse effects of fading, improve signal quality, and enhance overall system reliability.

Beamforming: Beamforming is a technique that focuses the transmitted signal in a specific direction or towards a specific receiver. By adjusting the phase and amplitude of the signals from the multiple antennas, constructive interference can be achieved in the desired direction. This enables targeted and efficient communication with specific devices or areas.

MIMO leaky cables find applications in various scenarios where wireless communication coverage, capacity, and reliability are crucial, such as large buildings, tunnels, underground mines, or other environments with challenging propagation characteristics. By combining the advantages of MIMO and leaky cables, these systems can provide enhanced wireless connectivity and improved performance compared to traditional leaky cable or MIMO systems alone.

LS Cable & System manufactures RF Feeder System Leaky Cables

RFCL Series(Radiated Mode) leaky cables realize a specific form of slot and periodic structure on the outer conductor, applying electromagnetic wave radiation vertically to the cable axis.

Who First Invented Leaky Cable?

The invention of the leaky cable is attributed to George Brownell, an American engineer. He filed a patent for a "Leaky coaxial cable" in 1971, which was granted in 1976 (US Patent No. 3,945,006). Brownell's invention was designed to address the challenges of providing wireless communication coverage in underground mines, where conventional antennas faced difficulties due to signal attenuation and propagation limitations. The leaky cable he developed allowed for the distribution of radio signals along its length, providing reliable wireless communication in mining environments. Since then, leaky cables have found numerous applications beyond mining, including tunnels, buildings, and other challenging propagation environments.

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1 comment:

  1. A leaky feeder is a coaxial cable that has small sections of its copper shielding stripped away to allow radio frequency (RF) signals to escape. Leaky feeders, which act as extended antennas, are also called radiating cables.


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