What Is a Broad band Amplifier?
There are many cases in RF signal chains where it is necessary to increase the power level in a signal. For broadband or wideband systems that may cover up to several frequency octaves, a Broad band Amplifier is needed. This type of amplifier is designed to operate over a wide frequency range and introduce minimal noise and distortion to the signal while providing some gain. Typically, broad band RF amplifiers are used at key sections of a signal chain that require wide bandwidth but are not specifically areas where low-noise amplifiers or high gain amplifiers are used. The broad band amplifier differs from gain-block amplifiers mainly by their designation as having a wider bandwidth.
This nomenclature is somewhat cumbersome and confusing as there are also wideband or broad band low-noise amplifier and power amplifier variants that could be used in similar ways as broadband RF amplifiers. Many modern RF systems operate over wide bandwidths and are hence “broadband” which may add some confusion. There is no standard designation for what “broadband” or “wideband” mean in a general sense in terms of RF nomenclature. In cellular and home internet services, broadband is used to designate an approach that achieves better data transmission speeds for users as the signal bandwidths are larger than legacy services. One communications definition for wideband is a message bandwidth that exceeds the coherence bandwidth of a channel. The coherence bandwidth can be defined as the frequency range for which a channel has a flat amplitude response, or over which the amplitude fading is comparable. To what degree of “comparability” or “flatness” for these figures across a frequency range depends on the technological capability and is hence a moving target.
These amplifiers may be designed for a specific range of applications, such as a portion of the spectrum typically dedicated to a certain type of radio use case or as a generic equipment that covers an extremely wide frequency range. An example of this is a 2 GHz to 6 GHz Medium Power Broad band Amplifier, which is likely intended or used as an amplifier for cellular or WiFi applications to 6 GHz. Another example is the 2 to 18 GHz Medium Power Broadband Amplifier, which covers a much wider frequency range and could be used for cellular, WiFi, UWB, satellite, radar, or any other application within that frequency range.
Broadband RF amplifiers can be made to provide a significant amount of gain or can be made to exhibit a very low added noise figure. There are typically tradeoffs with amplifier designs among bandwidth, gain, gain flatness, added noise figure, nonlinearity, and power use. Hence, a broadband amplifier with a given design feature that is exaggerated may have less performance in other categories. More expensive amplifier designs and materials also exist that address some of these typical limitations by using more costly design techniques, materials, or fabrication methods.