Attenuator is an electronic component that provides attenuation. It is widely used in electronic equipment. Its main purpose is: (1) Adjust the size of the signal in the circuit; (2) In the comparative measurement circuit, it can be used for direct reading The attenuation value of the tested network; (3) Improve impedance matching. If some circuits require a relatively stable load impedance, you can insert an attenuator between this circuit and the actual load impedance to buffer the impedance change.

Principle
An attenuator is a circuit used to introduce a predetermined attenuation within a specified frequency range. It is generally indicated by the number of decibels of the attenuation introduced and the ohms of its characteristic impedance. Attenuators are widely used in cable television systems to meet the level requirements of multiple ports. Such as amplifier input, output level control, branch attenuation control. There are two types of attenuators: passive attenuators and active attenuators. The active attenuator cooperates with other thermal components to form a variable attenuator, which is used in the automatic gain or slope control circuit in the amplifier. Passive attenuators have fixed attenuators and adjustable attenuators.

Technical index
Working frequency band
The working frequency band of the attenuator refers to the use of the attenuator in a given frequency range, the attenuator can reach the index value. Because the radio frequency/microwave structure is related to frequency, components in different frequency bands have different structures and cannot be used universally. The working frequency band of modern coaxial structure attenuators is quite wide, so care should be taken in the design or use.

Attenuation
Regardless of the mechanism and specific structure of the power attenuation, the two-port network shown in the figure below can always be used to describe the attenuator.
In the figure, the power at the input end of the signal is P1, the power at the output end is P2, and the power attenuation of the attenuator is A (dB). If P1 and P2 are expressed in decibel milliwatts (dBm), the relationship between the power at both ends is
P2 (dBm) = P1 (dBm)-A (dB)
It can be seen that the attenuation describes the degree of power reduction after the power passes through the attenuator. The amount of attenuation is determined by the material and structure of the attenuator. The decibel is used as the unit of attenuation, which is convenient for the calculation of the whole machine index.
Power Capacity
The attenuator is a kind of energy consuming element, which turns into heat after power consumption. It can be imagined that after the material structure is determined, the power capacity of the attenuator is determined. If the power of the attenuator exceeds this limit, the attenuator will be burned. When designing and using, the power capacity must be clarified.

Return loss
Return loss is the standing wave ratio of the attenuator, and it is required that the input and output standing wave ratios at both ends of the attenuator should be as small as possible. The attenuator we want is a power consuming component, which cannot affect the circuits at both ends, that is, it matches the circuits at both ends. Consider this factor when designing attenuators.
Power factor
When the input power changes from 10mW to the rated power, the attenuation coefficient of change is expressed as dB/(dB*W). The specific algorithm of the change value of the attenuation is to multiply the coefficient by the total attenuation power (W). For example: an attenuator with a power capacity of 50W and a nominal attenuation of 40dB has a power coefficient of 0.001dB/(dB*W), which means that when the input power is increased from 10mW to 50W, its attenuation will change by 0.001*40*50 = 2dB as much!

Basic composition
The basic material that constitutes the RF/microwave power attenuator is resistive material. The usual resistance is a basic form of attenuator, and the resistance attenuator network formed from it is a lumped parameter attenuator. Through a certain process, the resistive material is placed in the radio frequency/microwave circuit structure of different bands to form the attenuator of the corresponding frequency. If it is a high-power attenuator, the volume must be increased, and the key is heat dissipation design. With the development of modern electronic technology, fast adjusting attenuators are needed in many occasions. This type of attenuator usually has two implementation methods. One is a semiconductor low-power fast-adjusting attenuator, such as a PIN tube or FET monolithic integrated attenuator; the other is a resistance attenuation network controlled by a switch. The switch can be an electronic switch or Radio frequency relay.

Summarized by Easybom.