[Go to TOC] 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.
