Helical antenna usually have fixed spacing between the coils. What is the advantage of varying the spacing between the helical antennas? Varying the pitch angle.
Thank you for your guidance in advance.
In Helical Antenna:
The spacing and pitch Angle both very very important design parameters which decides the Directive Gain, HPBW and BWFN.
Advantages of varying Spacing (S):
1. The Directivity Gain of the helix is directly proportional to spacing (S) between the helical turns.
Hence, Higher directivity can be achieved by increasing the spacing (S) between the helical turns results.
2. HPBW and BWFN are inversely proportional to square root of spacing (S) between the helical turns.
Hence, sharp major lobe (either in broadside plane or Along the axis of helix) results for higher values of turn-spacing (S).
Advantages of Pitch Angle (Alpha):
Pitch Angle (alpha) and spacing (S) between the helical turns are directly proportional:
Spacing: S= C tan (alpha);
Where C is Circumference of Helix and
alpha= Pitch Angle.
tan (alpha) value increases with increase in alpha value.
Hence, increase in pitch angle (alpha), results in increase in spacing (S) between the helical turns and it will results in following advantages.
1. Higher directive gain
2. Sharp major lobe having less value of HPBW and BWFN.
In Helical Antenna:
The spacing and pitch Angle both very very important design parameters which decides the Directive Gain, HPBW and BWFN.
Advantages of varying Spacing (S):
1. The Directivity Gain of the helix is directly proportional to spacing (S) between the helical turns.
Hence, Higher directivity can be achieved by increasing the spacing (S) between the helical turns results.
2. HPBW and BWFN are inversely proportional to square root of spacing (S) between the helical turns.
Hence, sharp major lobe (either in broadside plane or Along the axis of helix) results for higher values of turn-spacing (S).
Advantages of Pitch Angle (Alpha):
Pitch Angle (alpha) and spacing (S) between the helical turns are directly proportional:
Spacing: S= C tan (alpha);
Where C is Circumference of Helix and
alpha= Pitch Angle.
tan (alpha) value increases with increase in alpha value.
Hence, increase in pitch angle (alpha), results in increase in spacing (S) between the helical turns and it will results in following advantages.
1. Higher directive gain
2. Sharp major lobe having less value of HPBW and BWFN.
It can "smear out" (a bit like "Landau damping" in particle accelerators) the response i.e bandwidth etc..also known when this kind of devics are used as electromagnetic pickup or kickers for charged particle beams e.g. certain travelling wave tubes.
I f your referring to helical coil inductors, spacing & placing them at 90 deg angles reduces induced magnetic coupling which alters component properties
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