Hi researchers! I am interesting in areas of signal processing and electronics. So to go forward in research it is very important to find new and actual fields of research.
There are many topics of research in signal processing such as: millimeter wave, Beamforming, Deep Convolutional Neural Networks and their applications, adaptive systems and applications...etc.
I guess in the last 5 years, research teams are looking forward to use machine learning and artificial inteligence in the Non Destructive testing and evaluations in different industries and R&D departements.
In addition to the helpful answers by @Ashraf A.M. KHALAF and @Nabil Khatib , there is a bit more to add.
A good overview of the mathematics of signal processing is given in
Charles L. Byrne
Mathematics of Signal Processing: A First Course
http://faculty.uml.edu/cbyrne/sp1text.pdf
For a more recent approach to the mathematics (e.g., fast fourier transforms, vector bundles (see the attached image), sparse factorization of matrices, lattices, Lie groups) of signal processing, see
Bastian Seifert
FFT and orthogonal discrete transform on weight lattices of semi-simple Lie groups