How To Minimize The Distortion In Pulse Modulation Signals?

Have you ever encountered such a situation: video calls suddenly lag, data transmission frequently malfunctions, and the device occasionally “goes on strike”? Don’t think this is just a minor problem. It’s very likely that the pulse modulation signal distortion is causing trouble! Distortion is like a “roadblock” on the signal transmission path, not only slowing down work efficiency but also potentially causing considerable economic losses. Today let’s talk together about how to solve this problem.

Signal Distortion: Why is Your Device Malfunctioning?

1. Troubles caused by distortion

Imagine that the message you sent was delivered to the other party by the signal “Courier”, but it turned out to be completely different content. Isn’t that frustrating? In practical work, signal distortion can lead to a soaring communication bit error rate and continuous data transmission errors. In the industrial field, distortion may throw automated equipment into disarray and even cause safety accidents. These problems not only waste time but may also cause additional costs such as equipment maintenance and data loss.

2. The “ideal state” of the signal you want

We all hope that pulse modulation signals can be as stable as Mount Tai: when communicating, the sound is clear and the picture is smooth. When the equipment is in operation, it accurately executes instructions without any errors. Only by solving the distortion problem can the maintenance cost be reduced, the risk of failure be decreased, and work and life be more worry-free.

Where Does Distortion Come From?

Distortion is not unintentional. It is of two types mainly: linear distortion and nonlinear distortion. Let us observe how they “trouble making”.

Linear Distortion

A channel is a “highway” for transmitting signals, but the “road” is not always smooth. Channel “eccentricity” is one of the most frequent causes of linear distortion. It models signals of different frequencies differently. Some frequency signals travel fast and some slow, eventually leading to the “deformation and distortion” of the signal waveform, like cars traveling at different speeds on a bumpy road, their formation disrupted. The “time difference” of group delay is like members of a signal team running at different paces, some quickly and some slowly. Slowly, the entire signal “team” gets into disarray, and of course, the signal gets distorted.

Nonlinear Distortion

Each of the individual parts of the equipment has its own “little idiosyncracies” as well. Take the “runaway” power amplifier, for example. It is like the motor of a car. When it is in the normal operating range, it has enormous power, but when pushed too hard, it will produce abnormal “noise” – nonlinear distortion. This kind of distortion will create harmonics as well as intermodulation distortion, interfering with regular signals. Apart from power amplifiers, other gear can also interfere with signals due to their own natures or unstable operating conditions, causing nonlinear distortion.

How To Solve Distortion In Pulse Modulation Signals?

Having identified the culprit of the problem, let us now see how to “treat it with a quick fix”.

Linear Distortion

To rectify the disease of linear distortion, repair of the “path” of transmission of the signal is essential. Channel “pavement leveling” can use time-domain and frequency-domain equalization techniques. Time-domain equalization is like using a “magic broom” to re-arrange the distorted signal waveform in an orderly manner. Frequency-domain equalization is achieved by using a transverse filter to particularly “cure” the “eccentricity” problem of the channel for signals of different frequencies. Using the least mean square error algorithm, the path of the signal transmission is flattened and smoothed. In actual application, after many communication systems started using this process, the signal quality was significantly improved.

Regarding the “time difference” problem of group delay, in order to “adjust the time difference” of group delay, a group delay compensation network needs to be built. It is like an extremely precise “clock regulator”, which compensates the “pace” of different frequency components of the signal so that they will be equal again, thus enabling the signal to be transmitted in the right manner. In the process of adaptation, we may test the compensation effect by straightforward tests and refine repeatedly until the signal returns to normal.

Nonlinear Distortion

Against nonlinear distortion, the way to solve it is to tame the devices. For power amplifiers prone to “get out of control”, a “coolant” for power amplifiers is inevitable. Predistortion technology is like giving a “preventive injection” to a power amplifier in advance. Before it actually enters the amplifier, it first pre-processes the signal to eliminate the possible nonlinear distortion introduced by the amplifier. Post-distortion technology is to linearize the signal after distortion from the amplifier. Feedforward technology is essentially similar to finding an amplifier’s “assistant,” listening and distorting-correcting in real time. These different technologies each have their own strengths and weaknesses. For instance, predistortion is not costly but of limited accuracy, and feedforward technology works well but its configuration is complex. We can make elastic decisions based on the actual condition.

Other than power amplifiers, “selection and optimization” of devices also play an important role. When choosing devices, try to choose the devices with low nonlinearity and stability, similar to choosing reliable ones when we recruit employees. While that, reasonable device layout and circuit design to avoid their “mutual interference” can also help significantly reduce the generation of nonlinear distortion.

Let’s See How The Effect Is

After the problem of distortion is solved, how does one decide whether the effect is good or bad? We can use some measuring indicators, such as the amplitude of the error vector. It is a type of “accurate scale” for the measurement of difference between the actual value and ideal value of the signal. The power ratio between consecutive channels can reflect the degree of interference of the signal into adjacent channels. Through the employment of simple test equipment and methods, these data can be obtained. Then, based on the outcomes of data, verify if there is the necessity for additional optimizations to make the signal quality even better up to a higher level.

Summary

With the development of technology at a breakneck speed, there have been novel “weapons” to counter signal distortion. Artificial intelligence technology is gaining prominence. It can store and learn huge amounts of signal data, intelligently identify patterns of distortion, and correct parameters for compensation automatically, similar to having a “super smart assistant” at your fingertips. In the future, these new technologies can facilitate easier and more efficient suppression of signal distortion.

If you have some specific needs in solving the distortion problem of pulse modulation signals or receive any difficult problems, feel free to leave a message anytime! We can discuss with each other and make a customized solution for you to ensure smooth signal transmission!