Radio frequency attenuators are devices that are used in telecommunications networks to reduce the amplitude of an input signal by a certain amount (gain) with very little distortion of the signal waveform. The devices are made to reduce the output signal with respect to the input signal and to measure the power reduction in decibels (dB). Attenuators are generally passive devices and the degree of attenuation may be fixed, continuously adjustable, or incrementally adjustable. The impedance of the output and input signals are matched.
The two types of basic RF attenuators are fixed and variable. In fixed RF attenuators, the amount by which the amplitude is reduced is fixed. Variable RF attenuators' amplitude can be reduced in preset steps.
There are various other types of variable attenuators you can choose including:
- continuously variable where the attenuation can be varied continuously
- step type where the variation can be done in fixed steps
- programmable where the variation can be programmed
- direct reading where an external device is used to set the attenuation
- digital types use digital control signals and since digital signals are discrete, they can have a large number of finite states of attenuation.
While selecting a RF attenuator you need to consider: the frequency ranges that are to be covered, the maximum attenuation, the insertion loss; which is the signal power at the output to the signal power at the input and voltage standing wave ratio; which is the amount of reflected energy at the input.
RF attenuators are available with several mounting styles. Surface mount technology (SMT) places components on a printed circuit board (PCB) by soldering component leads or terminals to the top section of the board. Through hole technology (THT) mounts components by inserting component leads through holes in the board and soldering the leads on the opposite side of the board. Flat pack (FPAK) units come with flat leads and in assorted body sizes and pin counts. Connectorized devices are made to attach with coaxial or other types of connectors. Waveguide assemblies have a hollow metallic conductor with a rectangular or elliptical cross-section. Some conductors have solid or gaseous dielectric materials.
RF attenuators can also use several styles of connectors. These include Bayonet Neil-Concelman (BNC), Threaded Neil-Concelman (TNC), miniature coaxial (MCX), ultra high frequency (UHF), subminiature-A (SMA), subminiature-B (SMB), subminiature-P (SMP), MMCX, mini-UHF, type F, type N, 1.6/5.6, and 7-16 connectors.