Dear Alireza,

welcome,

The first order low pass filter is the lowest selectivity among the order of the filters. A low pass filter order n is the highest exponent value of denominator polynomial of the transfer function. As the order n increases the steepness of the transfer characteristics from the passband to the topband increases making the filter more selective.

This is the greatest difference between the first order and the higher order.

There is applications where the first order has no sufficient selectivity to reject the out of band signals.

For the low pass filter characteristics you can refer to the book: https://www.semanticscholar.org/paper/Practical-analog-and-digital-filter-design-Thede/67bdcc0d83257db1168473fac9f1e527f1168ba2

Best wishes

Dear Alireza,

welcome,

The first order low pass filter is the lowest selectivity among the order of the filters. A low pass filter order n is the highest exponent value of denominator polynomial of the transfer function. As the order n increases the steepness of the transfer characteristics from the passband to the topband increases making the filter more selective.

This is the greatest difference between the first order and the higher order.

There is applications where the first order has no sufficient selectivity to reject the out of band signals.

For the low pass filter characteristics you can refer to the book: https://www.semanticscholar.org/paper/Practical-analog-and-digital-filter-design-Thede/67bdcc0d83257db1168473fac9f1e527f1168ba2

Best wishes

Higher order filters provided greater roll off rates between pass band and stop band. They are also necessary to achieve required levels of attenuation or sharpness of cutoff. There is a good tutorial on low pass filter https://www.electronics-tutorials.ws/filter/filter_2.html that may be better to answer your query in detail.

What are the advantages of airplane relative to bicycle?

This qustion is no sense without accounting the aim and calulation cost.

Do You use airplane to go to the nearest store?

Do You use bicycle to move from Europe to Australia?

Thanks for your helpful answers and recommended references. Abdelhalim abdelnaby Zekry Aparna Sathya Murthy Muhammad Ali

Vladimir Kubov of course, you're right. we don't take a plane to the store. but, the issue i'm really involved in is that, i tried to modify a simple notch filter by introducing a low-pass (LP) branch to remove DC components. but when i increase the order of LP branch, i get some beneficial advantages and i just need to find out a justification for these improvements.

You needs to apply Your's filter to any real example. For example: removing DC componet from PPG-(Photo Pletismo Graphy) signal in Fitness Tracker. The AC is 1000 times weaker DC. Or any another REAL example.

Dear Alireza Hosseinnajad

You'd also indicate the type of filter you're working on passive or active. Anyway, filter design tools exist everywhere and a couple of clicks give you the filter characteristics and how they impact your target function. You may refer to my book if you just wanna understand everything about filter design and synthesis:

Book Fundamentals of Analog & Digital Signal Processing

Please read my book

The American University Laboratories For Electrical Engineering Part 1

You will find

some good examples.

Dear Alireza Hosseinnajad

• High order (--): More delay (loss of samples in the begging of the signal), induce instability of the filter due to addition, phase (~-n*pi/2), more coefficients to implement
• High order (++): More accurate
• Matlab Exemples: https://fr.mathworks.com/help/signal/ref/butter.html

Muhammad Hamza El-Saba Ziad Sobih thanks for your recommendations. I will take notice of your works and i consider them.