Which describes a linear array as in the answer?

Elements placed along a straight line, usually equally spaced, with uniform progressive phase shift

Elements placed around a circle with random phases

Elements placed on a plane with unequal amplitudes only

A single element fed through a reflector

What phase condition gives a broadside array?

alpha = 0, all elements in phase

alpha = 90° for every neighbour

For a long array of the same length L, which statement is correct?

End fire directivity (~4L/lambda) is about twice broadside (~2L/lambda)

Broadside directivity is about twice end fire

Both have the same directivity 2L/lambda

End fire directivity is about 10 times broadside

2073 Bhadra · 1+4 marks

Linear array; broadside vs end fire

Short answer

Linear array has elements placed along a straight line with uniform spacing and progressive phase shift. Broadside array: α=0, maximum radiation perpendicular to axis (θ=90°), bidirectional, typical spacing λ/2, directivity ≈2L/λ. End-fire array: α=-βd, maximum along axis (θ=0° or 180°), usually unidirectional, spacing λ/4, directivity ≈4L/λ.

What is a linear array? Differentiate between a broadside array and end fire array.

A linear array is an array whose elements are placed along a straight line (the array axis), usually equally spaced, equal in amplitude and with a uniform progressive phase shift α between neighbours. Its array factor is

AF = sin(nψ/2) / [n sin(ψ/2)],  ψ = βd cosθ + α

Broadside vs end fire array

Point	Broadside array	End fire array
Direction of max	Perpendicular to array axis (θ = 90°)	Along array axis (θ = 0° or 180°)
Phase condition	α = 0 (all in phase)	α = −βd (progressive phase)
Pattern	Bidirectional fan/disc around axis	Usually unidirectional pencil along axis
Null-to-null beamwidth	≈ 2λ/(nd)	≈ 2√(2λ/(nd))
Directivity (long array)	≈ 2L/λ	≈ 4L/λ
Typical spacing	λ/2	λ/4
Example	Collinear/curtain arrays for HF broadcast	Yagi-Uda, end-fire HF arrays

 Broadside:             End fire:
      ^  max                 
      |                 
  o o o o o  axis       o o o o o ===> max
      |                  along axis
      v  max

Broadside arrays give a beam at right angles to the line of elements, so they suit point-to-point links where the array can be mounted across the direction of transmission. End fire arrays give higher directivity for the same length and are used where the line of elements can point at the target.

✓ Answer checked by Claude Opus 5.5 (high effort)

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