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RADIATION PATTERNS
The radiation pattern is a graphical depiction of the relative field strength transmitted from or received by
the antenna. Antenna radiation patterns are taken at one frequency, one polarization, and one plane cut. The patterns
are usually presented in polar or rectilinear form with a dB strength scale. Patterns are normalized to the maximum
graph value, 0 dB, and a directivity is given for the antenna. This means that if the side lobe level from the radiation
pattern were down 13 dB, and the directivity of the antenna was 4 dB, then the sidelobe gain would be 9 dB.
Figures
1 to 14 on the pages following depict various antenna types and their associated characteristics. The patterns depicted
are those which most closely match the purpose for which the given shape was intended. In other words, the radiation
pattern can change dramatically depending upon frequency, and the wavelength to antenna characteristic length ratio.
See section 34. Antennas are designed for a particular frequency. Usually the characteristic length is a multiple
of λ/2 minus 215% depending on specific antenna characteristics.
The gain is assumed to mean directional gain of the antenna compared to an isotropic radiator transmitting to
or receiving from all directions.
The halfpower (3 dB) beamwidth is a measure of the directivity of the antenna.
Polarization, which is the direction of the electric (not magnetic) field of an antenna is another important
antenna characteristic. This may be a consideration for optimizing reception or jamming.
The bandwidth is a measure of how much the frequency can be varied while still obtaining an acceptable VSWR (2:1
or less) and minimizing losses in unwanted directions. See Glossary, Section 10.
A 2:1 VSWR corresponds to a 9.5dB (or 10%) return loss  see Section 62.
Two methods for computing antenna bandwidth are used:
Narrowband by %,
where FC = Center frequency
Broadband by ratio,
An antenna is considered broadband if FU / FL > 2. The table at the right shows the equivalency of the two,
however the shaded values are not normally used because of the aforementioned difference in broadband/narrowband.
For an object that experiences a plane wave, the resonant mode is achieved when the dimension of the object
is λ/2, where n is an integer. Therefore, one can treat the apertures shown in the figure below as half wave length
dipole antennas for receiving and reflecting signals. More details are contained in section 84.The following
lists antenna types by page number. The referenced page shows frequency limits, polarizations, etc.
4 arm conical spiral 
33.6 
log periodic 
33.8 
alford loop 
33.4 
loop, circular 
33.4 
aperture synthesis 
33.8 
loop, alfred 
33.4 
array 
33.8 
loop, square 
33.4 
axial mode helix 
33.5 
luneberg lens 
33.9 
biconical w/polarizer 
33.6 
microstrip patch 
33.9 
biconical 
33.6 
monopole 
33.3 
cavity backed circuit fed slot 
33.9 
normal mode helix 
33.5 
cavity backed spiral 
33.5 
parabolic 
33.7 
circular loop 
33.4 
patch 
33.9 
conical spiral 
33.5 
reflector 
33.9 
corner reflector 
33.9 
rhombic 
33.3 
dipole array, linear 
33.8 
sinuous, dual polarized 
33.6 
dipole 
33.3 
slot, guide fed 
33.9 
discone 
33.4 
slot, cavity backed 
33.9 
dual polarized sinuous 
33.6 
spiral, 4 arm conical 
33.6 
guide fed slot 
33.9 
spiral, conical 
33.5 
helix, normal mode 
33.5 
spiral, cavity backed 
33.5 
helix, axial mode 
33.5 
square loop 
33.4 
horn 
33.7 
vee 
33.3 
linear dipole array 
33.8 
yagi 
33.8 


MONOPOLE Polarization: Linear Vertical as shown
Typical HalfPower Beamwidth 45 deg x 360 deg
Typical Gain: 26 dB at best
Bandwidth: 10% or 1.1:1
Frequency Limit Lower: None Upper: None
Remarks: Polarization changes to horizontal if rotated to horizontal



λ/2 DIPOLE Polarization: Linear Vertical as shown
Typical HalfPower Beamwidth 80 deg x 360 deg
Typical Gain: 2 dB
Bandwidth: 10% or 1.1:1
Frequency Limit Lower: None Upper: 8 GHz (practical limit)
Remarks: Pattern and lobing changes significantly with L/f. Used as a gain reference < 2 GHz.

Figure 1


VEE Polarization: Linear Vertical as shown
Typical HalfPower Beamwidth 60 deg x 60 deg
Typical Gain: 2 to 7 dB
Bandwidth: "Broadband"
Frequency Limit Lower: 3 MHz Upper: 500 MHz (practical limits)
Remarks: 24 kHz versions are known to exist. Terminations may be used to reduce backlobes.



RHOMBIC Polarization: Linear Vertical as shown
Typical HalfPower Beamwidth 60 deg x 60 deg
Typical Gain: 3 dB
Bandwidth: "Broadband"
Frequency Limit Lower: 3 MHz Upper: 500 MHz
Remarks: Termination resistance used to reduce backlobes.

Figure 2


CIRCULAR LOOP (small) Polarization: Linear Horizontal as shown
Typical HalfPower Beamwidth: 80 deg x 360 deg
Typical Gain: 2 to 2 dB
Bandwidth: 10% or 1.1:1
Frequency Limit: Lower: 50 MHz Upper: 1 GHz



SQUARE LOOP
Polarization: Linear Horizontal as shown
Typical HalfPower Beamwidth: 100 deg x 360 deg
Typical Gain: 13 dB
Bandwidth: 10% or 1.1:1
Frequency Limit: Lower: 50 MHz Upper: 1 GHz

Figure 3


DISCONE Polarization: Linear Vertical as shown
Typical HalfPower Beamwidth: 2080 deg x 360 deg
Typical Gain: 04 dB
Bandwidth: 100% or 3:1
Frequency Limit: Lower: 30 MHz Upper: 3 GHz



ALFORD LOOP Polarization: Linear Horizontal as shown
Typical HalfPower Beamwidth: 80 deg x 360 deg
Typical Gain: 1 dB
Bandwidth: 67% or 2:1
Frequency Limit: Lower: 100 MHz Upper: 12 GHz

Figure 4


AXIAL MODE HELIX Polarization: Circular Left hand as shown
Typical HalfPower Beamwidth: 50 deg x 50 deg
Typical Gain: 10 dB
Bandwidth: 52% or 1.7:1
Frequency Limit Lower: 100 MHz Upper: 3 GHz
Remarks: Number of loops >3



NORMAL MODE HELIX Polarization: Circular  with an ideal pitch to diameter ratio.
Typical HalfPower Beamwidth: 60 deg x 360 deg
Typical Gain: 0 dB
Bandwidth: 5% or 1.05:1
Frequency Limit Lower: 100 MHz Upper: 3 GHz

Figure 5


CAVITY BACKED SPIRAL (Flat Helix)Polarization: Circular Left hand as shown
Typical HalfPower Beamwidth: 60 deg x 90 deg
Typical Gain: 24 dB
Bandwidth: 160% or 9:1
Frequency Limit: Lower: 500 MHz Upper: 18 GHz



CONICAL SPIRAL Polarization: Circular Left hand as shown
Typical HalfPower Beamwidth: 60 deg x 60 deg
Typical Gain: 58 dB
Bandwidth: 120% or 4:1
Frequency Limit: Lower: 50 MHz Upper: 18 GHz

Figure 6


4 ARM CONICAL SPIRAL Polarization: Circular Left hand as shown
Typical HalfPower Beamwidth: 50 deg x 360 deg
Typical Gain: 0 dB
Bandwidth: 120% or 4:1
Frequency Limit: Lower: 500 MHz Upper: 18 GHz



DUAL POLARIZED SINUOUS Polarization: Dual vertical or horizontal or dual Circular right
hand or left hand with hybrid
Typical HalfPower Beamwidth: 75 deg x 75 deg
Typical Gain: 2 dB
Bandwidth: 163% or 10:1
Frequency Limit: Lower: 500 MHz Upper: 18 GHz

Figure 7


BICONICAL Polarization: Linear, Vertical as shown
Typical HalfPower Beamwidth: 20100 deg x 360 deg
Typical Gain: 04 dB
Bandwidth: 120% or 4:1
Frequency Limit: Lower: 500 MHz Upper: 40 GHz



BICONICAL W/POLARIZER Polarization: Circular, Direction depends on polarization
Typical HalfPower Beamwidth: 20100 deg x 360 deg
Typical Gain: 3 to 1 dB
Bandwidth: 100% or 3:1
Frequency Limit: Lower: 2 GHz Upper: 18 GHz

Figure 8


HORN Polarization: Linear
Typical HalfPower Beamwidth: 40 deg x 40 deg
Typical Gain: 5 to 20 dB
Bandwidth: If ridged: 120% or 4:1 If not ridged: 67% or 2:1
Frequency Limit: Lower: 50 MHz Upper: 40 GHz



HORN W/POLARIZER Polarization: Circular, Depends on polarizer
Typical HalfPower Beamwidth: 40 deg x 40 deg
Typical Gain: 5 to 10 dB
Bandwidth: 60% or 2:1
Frequency Limit: Lower: 2 GHz Upper: 18 GHz

Figure 9


PARABOLIC (Prime) Polarization: Takes polarization of feed
Typical HalfPower Beamwidth: 1 to 10 deg
Typical Gain: 20 to 30 dB
Bandwidth: 33% or 1.4:1 limited mostly by feed
Frequency Limit: Lower: 400 MHz Upper: 13+ GHz



PARABOLIC Polarization: Takes polarization of feed
Typical HalfPower Beamwidth: 1 to 10 deg
Typical Gain: 20 to 30 dB
Bandwidth: 33% or 1.4:1
Frequency Limit: Lower: 400 MHz Upper: 13+ GHz

Figure 10


YAGI Polarization: Linear Horizontal as shown
Typical HalfPower Beamwidth 50 deg X 50 deg
Typical Gain: 5 to 15 dB
Bandwidth: 5% or 1.05:1
Frequency Limit: Lower: 50 MHz Upper: 2 GHz



LOG PERIODIC Polarization: Linear
Typical HalfPower Beamwidth: 60 deg x 80 deg
Typical Gain: 6 to 8 dB
Bandwidth: 163% or 10:1
Frequency Limit: Lower: 3 MHz Upper: 18 GHz
Remarks: This array may be formed with many shapes including dipoles or toothed arrays.

Figure 11


LINEAR DIPOLE ARRAY (Corporate Feed)Polarization: Element dependent Vertical as shown
Typical HalfPower Beamwidth: Related to gain
Typical Gain: Dependent on number of elements
Bandwidth: Narrow
Frequency Limit: Lower: 10 MHz Upper: 10 GHz



APERATURE SYNTHESIS All characteristics dependent on elements
Remarks: Excellent sidelooking, ground mapping where the aircraft is a moving linear element.

Figure 12


CAVITY BACKED CIRCUIT FEED SLOT (and microstrip patch)Polarization: Linear, vertical as shown
Typical HalfPower Beamwidth: 80 deg x 80 deg
Typical Gain: 6 dB
Bandwidth: Narrow
Frequency Limit: Lower: 50 MHz Upper: 18 GHz
Remarks: The feed line is sometimes separated from the radiator by a dielectric & uses capacitive coupling.
Large conformal phased arrays can be made this way.



GUIDE FED SLOT Polarization: Linear,
Typical HalfPower Beamwidth Elevation: 4550E Azimuth: 80E
Typical Gain: 0 dB
Bandwidth: Narrow
Frequency Limit: Lower: 2 GHz Upper: 40 GHz
Remarks: Open RF Waveguide

Figure 13


CORNER REFLECTOR Polarization: Feed dependent
Typical HalfPower Beamwidth 40 deg x variable
Typical Gain: 10 dB above feed
Bandwidth: Narrow
Frequency Limit Lower: 1 GHz Upper: 40 GHz
Remarks: Typically fed with a dipole or collinear array.



LUNEBURG LENS (also LUNEBERG)Polarization: Feed dependent
Typical HalfPower Beamwidth: System dependent
Typical Gain: System dependent
Bandwidth: Narrow
Frequency Limit Lower: 1 GHz Upper: 40 GHz
Remarks: Variable index dielectric sphere.

Figure 14
Table of Contents
for Electronics Warfare and Radar Engineering Handbook
Introduction 
Abbreviations  Decibel  Duty
Cycle  Doppler Shift  Radar Horizon / Line
of Sight  Propagation Time / Resolution  Modulation
 Transforms / Wavelets  Antenna Introduction
/ Basics  Polarization  Radiation Patterns 
Frequency / Phase Effects of Antennas 
Antenna Near Field  Radiation Hazards 
Power Density  OneWay Radar Equation / RF Propagation
 TwoWay Radar Equation (Monostatic) 
Alternate TwoWay Radar Equation 
TwoWay Radar Equation (Bistatic) 
Jamming to Signal (J/S) Ratio  Constant Power [Saturated] Jamming
 Support Jamming  Radar Cross Section (RCS) 
Emission Control (EMCON)  RF Atmospheric
Absorption / Ducting  Receiver Sensitivity / Noise 
Receiver Types and Characteristics 
General Radar Display Types 
IFF  Identification  Friend or Foe  Receiver
Tests  Signal Sorting Methods and Direction Finding 
Voltage Standing Wave Ratio (VSWR) / Reflection Coefficient / Return
Loss / Mismatch Loss  Microwave Coaxial Connectors 
Power Dividers/Combiner and Directional Couplers 
Attenuators / Filters / DC Blocks 
Terminations / Dummy Loads  Circulators
and Diplexers  Mixers and Frequency Discriminators 
Detectors  Microwave Measurements 
Microwave Waveguides and Coaxial Cable 
ElectroOptics  Laser Safety 
Mach Number and Airspeed vs. Altitude Mach Number 
EMP/ Aircraft Dimensions  Data Busses  RS232 Interface
 RS422 Balanced Voltage Interface  RS485 Interface 
IEEE488 Interface Bus (HPIB/GPIB)  MILSTD1553 &
1773 Data Bus  This HTML version may be printed but not reproduced on websites.
