On Complex Conjugate Pair Sums and Complex Conjugate Subspaces

• Published in: IEEE signal processing letters 2019-09, Vol.26 (9), p.1403-1407
• Main Authors: Shah, Shaik Basheeruddin, Chakka, Vijay Kumar, Reddy, Arikatla Satyanarayana
• Format: Article
• Language: English
• Subjects: ccps; ccs; Complex conjugate pair; Computation; Computational complexity; Conjugates; Convolution; derivative; Edge detection; Equivalence; Image detection; Image edge detection; Impulse response; Indexes; Linear systems; projections; Radar tracking; shift-invariant; Subspaces; Sums; Transforms
• ISSN: 1070-9908; 1558-2361
• DOI: 10.1109/LSP.2019.2932717

In this letter, we study a few properties of Complex Conjugate Pair Sums (CCPSs) and Complex Conjugate Subspaces (CCSs). Initially, we consider an LTI system whose impulse response is one period data of CCPS. For a given input x(n), we prove that the output of this system is equivalent to computing the first order derivative of x(n). Further, with some constraints on the impulse response, the system output is also equivalent to the second order derivative. With this, we show that a fine edge detection in an image can be achieved using CCPSs as impulse response over Ramanujan Sums (RSs). Later computation of projection for CCS is studied. Here the projection matrix has a circulant structure, which makes the computation of projections easier. Finally, we prove that CCS is shift-invariant and closed under the operation of circular cross-correlation.