Therefore, the spacing of adjacent element in conventional uniform linear array
has to be no more than half wavelength for avoiding ambiguity in DOA estimation.
An 8-element uniform linear array
with 1m interelement spacing, which is half-wavelength of the received narrowband signal with center frequency 750Hz, is considered here.
Caption: Figure 1: Uniform linear array
Note that, for simultaneous estimation of the azimuth and the elevation, the uniform linear array
(ULA) cannot be adopted since ULA-based algorithm cannot uniquely estimate the azimuth and the elevation due to the ambiguity pertinent to the ULA structure.
Compared to the uniform linear array
(ULA), we can obtain more accurate angle estimation.
Uniform linear array
shows the respective SLL values as -12.97 dB, -13.11 dB, and -13.20 dB.
Svantesson, "Modeling and estimation of mutual coupling in a uniform linear array
of dipoles," in 1999 IEEE International Conference on Acoustics, Speech, and Signal Processing.
Woerner, "BER performance of a uniform circular array versus a uniform linear array
in a mobile radio environment," IEEE Trans.
From Figures 3 and 4, it is clear that the uniform linear array
(ULA) geometry of subarrays produces many ripples with no considerable main beams, as in the case of rectangular geometry, which produces multiple beams with reasonable gain.
According to the equivalent phase center theorem, the sparse linear array with multiple transmitting array elements and multiple receiving array elements on the basis of time division can be equivalent to a uniform linear array
that every equivalent array element transmits and receives signal by itself .
The work  developed a low-complexity noncircular rational invariance propagator method (NC-RI-PM) for angle estimation, which is used for uniform linear array
 put forward several kinds of uniform linear array
low side lobe pattern synthesis algorithms.