Active Beamforming Vs Passive Beamforming | Difference between Active Beamforming and Passive Beamforming

This page compares Active Beamforming Vs Passive Beamforming and mentions difference between Active Beamforming and Passive Beamforming with respect to their advantages (i.e. benefits) and disadvantages (i.e. drawbacks).

Introduction: The beamforming is used for directional signal transmission and reception using electrically steered antennas. Unlike mechanically steered dish antennas, these antennas have provision to change both amplitude and phase of the individual beams electronically. The antenna arrays with separate provision for amplitude/phase variation is used in beamforming for both the transmission as well as reception.

The beamforming is mainly categorized as analog and digital. In analog beamforming, amplitude and phase variation is applied on analog signal to be transmitted over the air. In digital beamforming, amplitude and phase variation is applied on digital signal befor DAC (Digital to Analog Conversion) at transmitter side. Beamforming can also be divided into two types viz. active and passive beamforming based on positions of RF power amplifiers, RF LNAs and radio transceivers.

Active Beamforming

Beamforming architecture in which RF amplifiers are used as internal elements of an antenna array is known as active beamforming array.

active beamforming

The figure-1 depicts active beamforming architecture. This beamforming type is further categorized into following types. They are manufactured by many companies such as Ball, SatixFy and SpaceX.
• Active analog beamforming : It consists of single RF chain which connects antenna element with amplifiers, phase shifters, splitters/combiners.
• Active digital beamforming : It uses dedicated RF to digital path from each antenna element instead of common RF chain used in analog beamforming. RF to baseband conversion is carried out using RF mixers, ADCs and DACs. Phases and amplitudes are controlled digitally.
• Active hybrid beamforming : It is combination of analog and digital beamforming architectures.

Refer difference between analog beamforming and digital beamforming >> and basics and types of hybrid beamforming >>.

Passive Beamforming

Beamforming architecture in which amplifiers or radios are used as external elements of an antenna array is known as passive beamforming array.

passive beamforming IC

The figure-2 depicts passive beamforming IC ADAR1000 from Analog Devices Inc. It is a four channel X/Ku band Beamformer IC functions as vector modulator. This IC uses on-chip DACs for LNAs and PAs (Power Amplifiers) bias. It operates from 8 GHz to 16 GHz. Four numbers of external radio transceivers can be interfaced with this beamformer IC. Design of beamformer IC allows individual adjustment of amplitude and phase of all the four channels. One ADAR1000 can interface maximum of four numbers of ADTR1107 (front end IC). This front end IC consists of PA (power amplifier), LNA ( Low Noise Amplifier ) and SPDT switch. The passive analog beamforming arrays are manufactured by Alcan Systems and other companies.

Following are the benefits or advantages of passive beamforming.
• It consumes low DC power compare to active beamforming as electronic amplifiers are not used.
• The antenna array architecture is simple and straightforward.

Following are the drawbacks or disadvantages of passive beamforming,
• The antenna panel is larger in size due to intrinsic losses of LC elements and PCB materials used.
• It provides slower beam switching due to higher time response of LC molecules. This leads to temporary interruption of user terminal to satellite radio link during handover process.
• Molecular response time depends on operating temperature. Hence this beamforming array requires extra heater to maintain operating temperature and system performance under extreme environment.

Difference between active beamforming and passive beamforming

Following table mentions difference between active beamforming and passive beamforming.

Parameters Active Beamforming array Passive Beamforming array
Antenna size Medium Large
Weight Light Medium
Power consumption High Low
Cost Medium (active analog) to high (active digital and active hybrid) High

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