Advantages of RF Power Amplifier | Disadvantages of RF Power Amplifier

This page covers advantages and disadvantages of RF Power Amplifier. It mentions benefits or advantages of RF Power Amplifier and drawbacks or disadvantages of RF Power Amplifier.

Introduction:
The electronic device which is used to increase magnitude of current or voltage or power of the input signal is called amplifier. Power amplifiers are used to drive various output types. Based on these there are three major types of power amplifiers viz. audio, RF and DC power amplifiers. Audio PA (Power amplifier) is used to increase magnitude of audio signal and used in speakers of mobile phones and televisions. DC power amplifier is used to increase power of Pulse Width Modulated (PWM) signal. DC power amplifier takes input from microcontroller and provide amplified output to DC motors (or actuators). Power amplifier operates in various classes viz. A, B, AB or C category. Power ampllifiers are used for wide applications in consumer electronics, industrial systems, wireless communications etc.

What is RF Power Amplifier ?

RF power amplifier is used to amplify modulated radio frequency (RF) signals so that they can be sent to long distances over the air using antenna. It is designed to handle complex modulated signals such as multi-level QAM, OFDM etc.

RF Power Amplifier in VSAT system

The figure depicts position of RF PA (Power Amplifier) in a VSAT system used for satellite communication systems. As shown it is used after up converter of RF transceiver and before RF antenna. The figure-2 depicts internal design components of 5 Watt RF power amplifier used in VSAT with gain of about 40 dB. RF power amplifiers are manufactured by various manufacturers such as Analog Devices, Empower RF Systems, Skyworks Solutions, ANADIGICS, Agile Microwave Technology etc.

RF Power Amplifier

Following are the specifications of RF Power Amplifier considered for selection.
• Frequency range
• Power gain
• Power output at P1dB and saturated power output
• Gain response over entire frequency range
• 1dB gain compression point
• Two tone intermoduation
• VSWR (at input and output) or return loss
• Group delay, AM/PM conversion, Noise figure
• Other parameters : Size, power requirements, connectors etc.

Benefits or advantages of RF Power Amplifier

Following are the benefits or advantages of RF Power Amplifier:
➨It increases power of RF input signal so that longer coverage can be achieved by overcoming path loss through the channel and other system components.
➨It increases sensitivity of the RF receiver.
➨It is used to improve SNR (Signal to Noise Ratio) of the the RF signal.
➨It offers high degree of linearity so that output does not have much distortion and output signal resembles that of the input signal after amplification.
➨Power amplifier with higher PAE (Power Added Efficiency ) helps to minimize power consumption and heat dissipation. PAE is expressed as follows.
• PAE (in %) = ( (RF_Out_power - RF_In_Power)/(DC power) ) x 100

Drawbacks or disadvantages of RF Power Amplifier

Following are the drawbacks or disadvantages of RF Power Amplifier:
➨RF Power amplifier with lower PAE will have more heat dissipation and higher power consumption.
➨Due to its nonlinear behavior, RF PA produces harmonic frequencies and IMD (Intermodulation) products. This causes interference with other signals. This has to be taken care during its design.
➨RF PAs have saturation region beyond which output power can not be increased any more.
➨RF PAs are usually large and bulky. Hence they are not suitable for portable and mobile devices.
➨RF PAs may not have higher efficiency. Hence they have more heat dissipation and consume more power.

➨Refer Power Amplifier linearity measurement methods >>.



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