a Matlab package for phased array beam shape inspection

35
s(t, r; û) E p
û û 0
0 R m
∑
{
s m (t, û)∝ s(t, R m ; û)
T m (û 0 )
1 2 m M Ψm (û 0 , ¯ω)
{
a m
a m s m (t − T, û)
TS
PS
a m s m (t, û) e −iΨm
z(t, û, û 0 ) TS
{ z(t, û, û 0 , ¯ω) PS
Figure 1: Beam steering, reception view in the continuous-time domain. A far-away
point source in direction û produces time- and space varying incoming electric
field s(t, r, û)E p near the antenna array of M elements. The vector E p is taken
to be complex-valued to represent polarization; it may depend on the direction
û, but not on the position r or the time t. The elements sniff the incoming
field at points R m so that a (complex-valued, to represent the polarization)
voltage s m (t) is generated across the terminals of element m. This voltage
is amplified by a real factor a m and fed to the beam-former system, which
may be either a time-steering system (TS) or a phase-steering system (PS).
In the TS system, the signal a m s m at element m is delayed by an amount
T m which depends on the element position and the desired steering direction
û 0 , before being fed to an adder which produces the final beam-formed signal
z(t). In the PS version of the beam-former, there is no explicit delaying, but
instead the phase of a m s m (t) is adjusted by an angle Ψ m , computed from the
element position, the desired beam direction, and the average frequency ¯ω of
the incoming pulse. The figure represents the array elements by semi-spheres
to suggest an isotropic element gain in the upper half-sphere. When desired, a
non-isotropic √ element power gain g E can be explicitly incorporated by replacing
a m by a m gE (û).