This paper presents a high resolution Direction-Of-Arrival (DOA) estimation method using unwrapped phase information of MUSIC-based noise subspace. Superresolution DOA estimation methods such as MUSIC, Root-MUSIC and ESPRIT methods are paid great attention because of their brilliant properties in estimating DOAs of incident signals. Those methods achieve high accuracy in estimating DOAs in a good propagation environment, but would fail to estimate DOAs in severe environments like low Signal-to-Noise Ratio (SNR), small number of snapshots, or when incident waves are coming from close angles. In MUSIC method, its spectrum is calculated based on the absolute value of the inner product between array response and noise eigenvectors, means that MUSIC employs only the amplitude characteristics and does not use any phase characteristics. Recalling that phase characteristics plays an important role in signal and image processing, we expect that DOA estimation accuracy could be further improved using phase information in addition to MUSIC spectrum. This paper develops a procedure to obtain an accurate spectrum for DOA estimation using unwrapped and differentiated phase information of MUSIC-based noise subspace. Performance of the proposed method is evaluated through computer simulation in comparison with some conventional estimation methods.

The problem of electromagnetic scattering caused by inductive discontinuities locate in parallel-plate waveguides, in particular when dealing with discontinuous conductors of finite thickness, is analyzed using the modified residue-calculus method, the equations suitable for a numerical calculation are derived. The incident wave is taken to be the dominant mode, and the reflection and transmission properties of a symmetrical inductive iris are discussed.

The precise phase characteristics of the reflected and transmitted waves are obtained for electromagnetic scattering by inductive discontinuities of finite thickness located in rectangular waveguides. The incident wave is assumed to be the dominant mode, and the modified residue-calculus method is used for numerical analysis. The phase characteristics when the thickness and width of the iris are varied, and characteristics of the reflected and transmitted waves when resonance appears, are discussed. In addition, an X-band experiment is performed and the calculations for both the reflected and transmitted waves are shown to agree well with the experimental values.