This was for approximately a 45-50 minute technical phone interview.

Math:

• Singular matrix?
• Rank of a matrix and its importance?
• Null space?
• Inverse of a 2x2 square matrix (for given values)?
• Given two vectors, what is the angle between them?
• What is an eigenvector? Importance of eigenvalues and eigenvectors.
• Given the acceleration of a body, what is the velocity for a given t value?

Programming Concepts:

• Local and global scope?
• Recursive functions?
• Call by value and call by reference?
• Multicore processors?
• Difference between break and continue?

Signal Processing:

• Nyquist sampling theorem?
• Aliasing?
• Convolution?
• Difference between FIR and IIR filters?
• BIBO?
• Given y(n) = x(n) + C, comment on its linearity, time invariance, and causality.
• Stability/instability region in discrete time domain?
• What is PSD and what is it for white noise?
• Autocorrelation?

MATLAB:

• Difference between * and .*?
• How to plot in MATLAB?
• How to open a file from the command window?
• Differences between a script file and a function?
• How to display a variable or variables in the command window? (whos)
• How to compute the numerical length of an array? (numel)

C Programming:

• What is #include?
• Differences between <> and "" in #include?
• typedef?
• malloc?
• Null pointer?