Lecture on BMW (Beam Width)

Introduction

• Beam Width: Crucial parameter in antenna and wave propagation.
• Defined as the pressure angle from which most power is radiated.
• Related to antenna's direction of maximum directivity.
• Two types: HPBW (Half Power Beam Width) and FNBW (First Null Beam Width).

Types of Beam Width

1. HPBW (Half Power Beam Width)

• Definition: Angular separation where the magnitude of the radiation pattern is -3 dB from the main beam peak.
• Formula: HPBW = ( \frac{70 \lambda}{D} )
  • ( \lambda ) = wavelength
  • ( D ) = diameter

2. FNBW (First Null Beam Width)

• Definition: Angular separation between the first nulls of the radiation pattern.
• Formula: FNBW = 2 * HPBW
  • HPBW = ( \frac{70 \lambda}{D} )
  • Therefore, FNBW = ( \frac{140 \lambda}{D} )*

Radiation Patterns

• Major Lobe: The main lobe of radiation.
• Side Lobes: The smaller lobes around the major lobe.
• Back Lobe: The lobe opposite the main lobe.

Radiation Pattern Diagrams

HPBW

• Peak at 0 dB
• Defined at -3 dB points from the peak
• Represents angular separation where magnitude is reduced to half.

FNBW

• First nulls located on either side of the major lobe
• Defined as the angular separation between these first nulls.

Conclusion

• HPBW and FNBW are critical in understanding antenna radiation patterns.
• Knowing these helps in designing and optimizing antenna systems.

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