Definition of an active antenna. Scope of application

An active antenna is an antenna designed for reception or transmission purposes, in which an active element is directly integrated into the antenna itself. The active antenna operates in conjunction with a built-in amplifier, which compensates for signal attenuation due to the small size of the antenna. The amplifier requires electrical power to operate. Essentially, an active antenna is an independent unit of a radio engineering device and can be manufactured using printed circuit assembly techniques. Active antennas are widely used in phased array antennas of various radio engineering systems. Most commonly, active receiving antennas are used, although in recent years there have been descriptions of active transmitting antennas.

Active receiving antennas are most widely used as indoor and outdoor television antennas for household applications. Higher quality signal reception is achieved with the use of an additional electronic amplifier. The amplifier is usually mounted directly on the contacts of the active antenna element or integrated with a combiner in the case of a phased array. In such configurations, the active antenna is powered via the electrical network.

Example of an active antenna design

Another common application of active antennas is in automotive antennas for receiving broadcast radio stations. The antenna element in such designs is typically placed inside the vehicle cabin — in the form of a wire or a self-adhesive strip on the glass. To counteract interference both in urban areas and beyond, such antennas can operate in two modes: for urban environments and for rural roads. In the first case, they may operate without an amplifier or with reduced gain.

Main advantages of active antennas — compact dimensions and ease of installation. These types of antennas are installed inside a vehicle cabin or indoors, making them protected from atmospheric and mechanical impacts. Many active antennas allow adjustment of gain level and noise suppression.

Disadvantages of active antennas include their relatively high cost and technical complexity. Active antennas require a constant power source. If the input signal level does not match the gain factor of the active antenna, or if there is a strong nearby radio signal close to the active receiving antenna, the output signal may be distorted, contain interference, or be entirely absent. Due to the presence of electronic components, an active antenna is less reliable compared to a passive one, has a narrower operating temperature range, is more susceptible to atmospheric and industrial noise, and has a lower degree of lightning protection.