What is the difference between passive antenna and passive antenna?

Passive antennas are radiating elements composed entirely of passive components. Normally, this means that a passive antenna system includes at least a passive radiator (antenna element), passive impedance matching, passive balun, passive tuning (capacitance or inductance) and passive interconnection (usually 50 Ohm or 75 Ohm impedance) system. A circulator or isolator can also be considered part of a passive antenna, depending on whether the antenna system is packaged as a unit or as a separate part. In some cases, the term antenna can be used to describe antenna elements or structures and antenna systems.

Active antenna systems use some kind of active electrical enhancement or control method to provide improved antenna performance for a given application. Active antenna components may include amplifiers, such as low noise amplifiers (LNA) or power amplifiers (PA), active filters (tunable filters or switched filter banks), and switched antenna radiators. Active antennas can achieve control and performance enhancement, can be manually activated/configured, or automatically activated by software or analog/digital control systems. Active antennas are essential for many applications that require more degrees of freedom, tunability, and signal strength to/from antenna radiators or configurable antennas. Active antennas can better suppress unwanted signals, use a low-noise amplifier (LNA) close to the antenna can reduce the signal-to-noise ratio (SNR), have a higher transmission power, can better match the impedance of the antenna, and other The performance advantage depends on the active antenna technology used.

A more advanced version of the active antenna is the Active Antenna System (AAS), which can use complete transmit/receive (TRX) components and phase and amplitude adjustments to achieve beamforming. Other forms of active antenna systems (AAS) include multiple input multiple output (MIMO) functions, which include support for digital processing of multiple spatial streams from a multi-element antenna array. The antenna array can use analog beamforming, digital beamforming, or hybrid beamforming, depending on the technology used to drive the active antenna system (AAS) beamforming antenna array. A more advanced active antenna system (AAS) may include all antenna arrays, transceiver units (TRX), modulation/demodulation, digital-to-analog converter (DAC), analog-to-digital converter (ADC), digital processing, beamforming , Multiple Input Multiple Output (MIMO), Carrier Aggregation (CA), and network communication hardware in a single module, just like the latest 4G LTE Active Antenna System (AAS) module, are planned to be used in the 5G infrastructure.

Active antennas may also be part of smart antennas or cognitive radios, and include some knowledge of the electromagnetic (EM) spectrum in their environment, or include the ability to provide intelligence from the outside. In this way, the smart antenna can reconfigure itself to obtain the best performance in the current environment. Cognitive radio systems can even understand its environment and the dynamics of wireless communication in its environment, and develop strategies to utilize active antenna technology or other radio technologies to enhance its services.

Under normal circumstances, active antennas are more expensive and more complex than passive antennas, so active antenna suppliers have fewer choices. In addition, although active antennas and active antenna systems (AAS) may also include built-in self-test (BIST) and built-in diagnostics (BID) technologies that can help with the troubleshooting process, active antennas may be more difficult to perform than passive antennas Troubleshooting and maintenance. In many cases, active antennas or active antenna systems (AAS) are part of a larger communication infrastructure and must be operated in a specific way so that the active antenna or active antenna system (AAS) is only for a given Application is useful. For passive antennas, usually various antennas can be used according to needs or requirements.