Complementary Codes Approach to Sparse Frequency Waveform Design

Sparse frequency waveform (SFW) is able to utilize spectrums from disjoint channels in a single waveform so as to improve the overall bandwidth that is desirable in both radar and communications. One challenge faced with sparse frequency waveform design is the relatively high range sidelobe level due to spectrum discontinuity. In this paper, a new approach to sparse frequency waveform design with sidelobe suppression is proposed that exploits the sidelobe cancellation property of complementary codes (CC). Different design criterions are proposed to facilitate the requirements from different applications. Numerical simulations have been conducted to illustrate the effectiveness of the proposed approach.

I. Introduction

Spectrum congestion is an ever-increasing problem due to the fact that spectrum resource is fixed while the demand for it is ever growing. In a congested spectrum band, many channels of narrow bandwidth are assigned to different applications. In this case, it is very difficult to allocate a wider bandwidth to some applications such as high resolution radar that is more bandwidth-demanding. Sparse frequency waveform is one attractive approach to at least alleviate the problem of spectrum congestion. By using sparse frequency waveform, a few disjoint channels of smaller bandwidth can be constituted in a single waveform in order to form a larger bandwidth. Sparse frequency waveform with a number of narrower stopbands arbitrarily distributed over a wider frequency band is currently attracting many interests from both academic and industry because it provides good alternatives for waveforms operating in the highly congested spectrum environment. With a proper sparse frequency waveform, one can avoid interference from/to other users operating in the same band. Sparse frequency waveform can be used in HF radar, software defined radio, and even communications.