Basics of attenuators and amplifiers | Explaining the key points of signal control

As electronic devices and communication systems continue to evolve, the role of attenuators is becoming increasingly important in today's world, where precise signal control is required.

This article will explain in detail the basic definition of attenuators, their types, and the roles they play. It will also discuss the definition, role, and types of amplifiers that amplify signals, and their relationship to other measurement elements.

What is an attenuator?

An attenuator is a device that reduces the strength of an electrical signal without distortion. It is widely used in electronic and physical measurement fields.

There are multiple resistors built in, and when the input power passes through the resistors it is dissipated as heat, attenuating the signal. The amount of attenuation is determined by the ratio of the resistance values, so by changing the resistance values ​​according to the purpose, it is possible to attenuate the signal to an appropriate level while protecting the measuring instrument from excessive input.

It also helps to expand the dynamic range of the entire system, stabilizing measurements and communications while suppressing excessively high input signals. Since there is a risk of failure if the input range of the measuring instrument is exceeded, introducing an attenuator increases safety and reliability.

They are also valued as important elements in fields such as high-frequency circuits and optical communications, enabling accurate data acquisition while reducing noise and distortion.

The level of attenuation to be set depends on the system requirements, so it is necessary to check the frequency band and maximum input power indicated in the specifications and select the optimal product.

Attenuator types

There are several types of attenuators. Understanding the characteristics of each type will help you choose the right equipment.

The most common types are as follows.

• Fixed Attenuator
• Variable Attenuator
• Optical Attenuator

Fixed Attenuator

A fixed attenuator is a device that suppresses signals by a fixed amount of attenuation from the moment it is installed. It weakens the signal by a specific, pre-set value, such as "10dB" or "20dB."

A resistor network is built in, providing stable attenuation performance in a specific frequency band. Because of their simple structure, many of these products are small and economical, and also have excellent electrical stability.

They are often used permanently in a variety of environments, such as in communication equipment and measurement facilities, and are selected to be optimized for specific circuit designs. They are highly durable and can handle a wide range of frequencies, from low to high. The use of fixed types has the advantage of providing a constant amount of attenuation, making the measurement results highly reproducible.

However, if the attenuation needs to be changed, the device itself must be replaced.

Variable Attenuator

Variable attenuators are flexible devices that allow you to adjust the amount of attenuation stepwise or continuously. By turning a dial or switching the attenuation, you can easily change the amount of attenuation to 5dB, 10dB, 20dB, etc. as needed.

These characteristics make them particularly useful in research facilities and experimental environments where measurement conditions change frequently, and they are also widely used as part of a variety of test equipment.

The characteristic of the variable type is that the optimal attenuation can be set in real time according to the usage situation. There are two types of products: the step type, which can be adjusted in stages at a pre-defined value, and the continuous type, which can be smoothly adjusted to any value.

However, to achieve this adjustment function, the structure becomes more complex compared to fixed types, which increases manufacturing costs and tends to make the size larger. Design in the high frequency range in particular is technically difficult, and the higher the precision product that combines excellent attenuation characteristics and frequency characteristics, the higher the price.

Optical Attenuator

An optical attenuator is a dedicated device for controlling the strength of optical signals propagating through optical fibers in optical communication systems. Unlike electrical signal attenuation, it works by adjusting the transmittance of light itself. There are two main types of devices available: a fixed attenuation type that is connected to the end of the optical fiber, and a variable type that can adjust the transmittance as needed.

In long-distance optical communications, when an excessively strong optical signal reaches the receiver, the receiver becomes saturated, causing a decrease in measurement accuracy and degradation of communication quality. Optical attenuators play an important role in preventing such problems.

While basic optical attenuators use a specific optical filter to block a certain amount of light, variable products use more sophisticated technologies, such as a mechanism that adjusts the amount of attenuation by mechanically changing the light path, or an attenuation method that utilizes the polarization properties of light.

Optical attenuators are not only used for signal conditioning in optical communication networks, but are also an essential element in the calibration process of various optical measurement instruments. They are positioned as an important fundamental technology in any optical system that requires precise control of optical signals.

The role of the attenuator

Attenuators do more than just reduce the output level. They play a variety of roles, from protecting equipment to acquiring accurate data.

The main roles of the attenuator are:

• Adjusting the signal level
• Impedance Matching
• Overload protection

We will explain each one in detail.

Adjusting the signal level

An attenuator is a device that suppresses the strength of the input signal to an appropriate level so that the receiver operates under optimal conditions. Excessive input signals can cause saturation and waveform distortion inside the receiver, significantly impairing the accuracy of measurement results. By inserting an attenuator into the signal path, it is possible to attenuate the signal strength to a range that can be accurately processed by the receiver and various measuring devices.

For example, in frequency analysis using a spectrum analyzer, if the input signal is too strong, the displayed amplitude value will be inaccurate, making it difficult to perform correct measurement. By inserting an attenuator, you can prevent waveform distortion and check the accurate frequency characteristics.

In an experiment, adjustments are necessary when the output of the object being measured changes from day to day. Suppressing excess signals reduces the risk of damaging expensive equipment.

Impedance Matching

Attenuators also play a role in matching the characteristic impedance of the transmitting and receiving circuits. With high frequency signals, if the impedance does not match, reflections occur, causing the return of valuable power.

The characteristic of an attenuator is that it has the function of appropriately adjusting the characteristic impedance of the signal path using resistors and other circuit elements.

In the high frequency range, even a slight impedance mismatch can cause significant signal reflection at a specific frequency, which can have a serious adverse effect on communication quality and measurement accuracy. Attenuators have the effect of mitigating these minute mismatches by attenuating the signal.

In complex systems where multiple devices are connected in cascade, proper placement of attenuators can optimize impedance matching of the entire system while minimizing signal energy loss.

Overload protection

Too much power can cause serious damage to signal sources and receivers, and expensive sensors and circuitry can be destroyed if the input is pushed beyond its limits.

Attenuators act as protective devices in these situations by appropriately attenuating excess energy, reducing excessively strong signals to safe levels to protect critical measurement and communications equipment.

The power tolerance of measuring instruments and receivers must be carefully considered, especially in environments where high-power radio transmitters and high-energy laser systems are used. By incorporating an attenuator into the system, safety can be ensured even when handling high-power devices.

It can be said that attenuators are indispensable for ensuring stable operation of the entire system.

Use in optical communications

In optical communications, large volumes of data are transmitted by passing laser light through a fiber. If the optical signal is too strong, it will saturate the receiver and erroneous data will be detected. Therefore, it is necessary to introduce an optical attenuator and devise a way to adjust the optical intensity to the optimum level.

In long-distance communications, the output power of the light source must be high to take signal attenuation into account; however, in short-distance communications, the intensity may be excessive and place a strain on the receiver.

By using a variable optical attenuator, the amount of attenuation can be flexibly adjusted according to the transmission distance and the characteristics of the connected device, making it possible to always maintain an optimal signal level.

In many optical networks, optical attenuators are installed in modules and are managed in detail. Proper use of optical attenuators is essential for improving the reliability and optimizing the performance of optical communication systems, and they have become a key technology supporting modern communication infrastructure to handle the rapidly increasing data traffic.

Definition and Role of Amplifiers

While an attenuator is a device that intentionally weakens a signal, an amplifier is a device that adds energy to the input signal to increase its voltage or power. Amplifiers add energy to the input signal to increase its voltage or power. They are needed in a wide range of fields, from audio equipment to communication equipment.

When dealing with weak sensor signals, it is often the case that the voltage picked up is so small that it cannot be measured without an amplifier. For example, biomeasurements and weather observations deal with very small signals that are almost at the same level as the noise level. By using an amplifier to raise the signal to an appropriate range, it becomes possible to visualize and process it.

Amplifiers also play an important role in the field of communications technology. Especially in long-distance transmission, signals naturally attenuate within the transmission medium, so they must be amplified at regular intervals. The development of optical amplifiers in optical communications systems has become an innovative technology that has significantly extended the distance between repeaters, enabling ultra-long-distance optical fiber communications connecting continents.

Amplifier Types

There are various types of amplifiers depending on the frequency they handle, their operating principle, and their purpose. One example is the op-amp (operational amplifier), a versatile electronic component that amplifies weak signals and performs analog calculations.

Power amplifiers are used in situations where large output is required, such as audio power amplifiers that drive speakers.

Radio frequency amplifiers (RF amplifiers) are used in situations where high frequencies are used. They play an important role in wireless communication devices and radars, and must be designed to match the frequency band. On the other hand, low noise amplifiers (LNAs) are introduced to minimize noise, especially when receiving weak signals.

When selecting an amplifier, many factors must be carefully considered, including gain, frequency response, noise performance, linearity, power efficiency, etc. Choosing the wrong amplifier increases the risk of signal distortion and noise amplification, so care must be taken.

Other measuring elements

Attenuators and amplifiers are not the only elements used in measurement and communication. There are a variety of measurement elements, each of which supports the accuracy and stability of the entire system.

• Coupler (Directional Coupler）
  This is a device for splitting some of the signals.
  It is used to monitor the transmitted waveform and measure the reflected wave.
• filter
  It allows only the desired frequencies to pass and blocks out the unwanted frequencies.
  There are low-pass filters that only let low-frequency components through, and high-pass filters that only let high-frequency components through.
• Circulator
  This is a high-frequency component that allows current to flow in only one direction and does not allow current to flow in the opposite direction.
  This is useful when using the antenna for both transmission and reception.
• 3D rendering
  Accurately measure signal power to understand how your system is performing.
  When combined with an attenuator, it can also cover high output measurement ranges.

By combining these appropriately, it is possible to achieve high-quality communications while minimizing measurement errors.

Summary

There are many different types of these devices, and it is important to choose the one that best suits your specific application and requirements.

Understanding the characteristics and applications of the different types will help you select the equipment best suited to your environment and requirements.

In practical system designs, it is common to use a combination of attenuators and amplifiers, and a proper balance between them can optimize signal levels, improve impedance matching, and enhance overall system performance.

By using other measuring elements and auxiliary devices, more precise measurements and stable communication become possible. By correctly understanding the mechanisms of attenuators and amplifiers and incorporating them in the right places, many applications can be expanded.