Radio Wave Propagation

Radio Wave Propagation: Consolidated Summary Technical Report of the Committee on Propagation of the National Defense Research Committee presents all the scientific information and report of experiments. This book discusses the problems encountered in the propagation of radio waves.

Organized into three volumes, this book begins with an overview of the technical developments in the study of tropospheric propagation. This text then outlines the general theory of standard and nonstandard propagation together with descriptions and results of transmission experiments designed to test the theory. Other chapters consider the more unusual problems concerning the radar behavior of targets. This book discusses as well the problems of radio wave propagation in the standard atmosphere at frequencies above 30 megacycles. The final chapter deals with the selection and utilization of local terrain features that affect propagation and the performance of equipment.

This book is a valuable resource for scientists and engineers in the field of radio wave propagation.

Volume I Technical Survey

Part I Summary

Chapter 1. Standard Propagation

Introduction

Power Transmission

Optical Properties of the Earth's Surface and Atmosphere

The Electromagnetic Field

Chapter 2. Elementary Theory Of Nonstandard Propagation

Historical

Refractive Index

Types of M Curves

Ray Tracing

General Characteristics of Ducts

Survey of Waveguide Theory

Reflection from Elevated Layers

Chapter 3. Meteorological Measurements

Introduction

Temperature and Humidity Elements

The Wired Sonde

Refractive Index Measurements

Other Meteorological Instruments

Representative Observed Μ Curves

Chapter 4. Transmission Experiments

British Experiments

Experiments at the Eastern Coast of the U. S.

Experiments in Northwestern United States and Canada

Experiments in the Southwestern United States

Experiments at Antigua

Angle-of-Arrival Measurements

Chapter 5. General Meteorology And Forecasting

Introduction

Atmospheric Stratification

Conditions Over Land

Coastal and Maritime Conditions

Dynamic Effects

World Survey

Radar Forecasting

Chapter 6. Scattering And Absorption Of Microwaves

Absorption and Radar Cross Section

Aircraft Targets

Ship Targets

Absorption and Scattering by Clouds, Fog, Rain, Hail, and Snow

Part II Conference Reports On Standard Propagation

Chapter 7. A Graphical Method For The Determination Of Standard Coverage Charts

Chapter 8. Nomographic Solutions For The Standard Case

Chapter 9. Theoretical Analysis Of Errors In Radar Due To Atmospheric Refraction

Purpose

Procedure

Application to Ground Radar Equipments

Conclusions

Chapter 10. Diffraction Of Radio Waves Over Hills

Chapter 11. Siting And Coverage Of Ground Radars

Introduction

Radar Systems

Types of Ground Radar

Radar Systems — Tactical Aspects

Radar Siting — Technical Aspects

Topography of Siting

Introduction

Maps and Surveys

Profiles

Orientation

Visibility Problems

Diffraction of Radio Waves

Introduction

Wave Propagation

Fresnel Zones

Reflection from Rough Surfaces — Rayleigh's Criterion

Diffraction at Obstacles

Fresnel Integrals

The Cornu Spiral

Straight Edge Diffraction

Location of Maxima and Minima

The Rectangular Slit

Diffraction by a Narrow Obstacle

Multiple Slits and Obstacles

Limitations of Fresnel's Theory

Permanent Echoes

Introduction

Permanent Echo Diagrams

Use of Permanent Echoes in Testing

Shielding

Prediction of Permanent Echoes

Prediction by Profile Method

Microwave Permanent Echoes

The Calculation of Vertical Coverage

Introduction

The Vertical Coverage Diagram

Flat Earth Lobe Angle Calculations

Lobe Angles Corrected for Standard Earth Curvature

The General Lobe Angle Formula

The Calculation of Lobes

Low Site Lobes

Lobe Diagrams of Medium Height Sites

Shoreline Diffraction

Sea Reflection with Diffuse Land Reflection

General Formula for the Reflection Area

The Modified Antenna Pattern

Antenna Patterns

Local Terrain Effects

Earth Curvature Effect on Lobe Lengths

Coefficient of Reflection

Divergence

Lobe Lengths

The General Lobe Formula

Calibration and Testing

Equipment Tests

Signal Measurements

Conduct of Test Flights

Analysis of Test Data

Chapter 12. Variations In Radar Coverage

Bending

Guided Propagation

Meteorological Factors

Cloud Echoes in Radar

Summary of Basic Facts Concerning Propagation at Radar Frequencies

Part III Conference Reports On Nonstandard Propagation

Chapter 13. Tropospheric Propagation And Radio Meteorology

Fundamentals of Propagation

Significance of Propagation Problems

Factors Influencing Propagation

Reflection from the Ground

Refraction — Snell's Law

Refraction Over a Curved Earth

Equivalent Earth Radius — Flat Earth Diagram

The Horizon — Diffraction

Atmospheric Stratification and Refraction

Origin of Refractive Index Variations

The Measurement of Refractive Index

Types of Modified Index Curves

Rays in a Stratified Atmosphere

The Duct — Superrefraction

Wave Picture of Guided Propagation

Reflection from an Elevated Layer

Operational Applications

Radio Meteorology

Temperature and Moisture Gradients

Physical Causes of Stratification — Turbulence

Advective Ducts — Coastal Conditions

Ducts Over the Open Ocean

Nocturnal Cooling — Daily Variations

Fog

Subsidence — Dynamic Effects

Seasonal and Global Aspects of Superrefraction

Fluctuations in Signal Strength with Time

Scattering and Absorption by Water Drops

Snell's Law

Chapter 14. Theoretical Treatment Of Nonstandard Propagation In The Diffraction Zone

Chapter 15. Characteristic Values For The First Mode For The Bilinear M Curve

Chapter 16. Incipient Leakage In A Surface Duct

Calculations for the First Mode of the Bilinear Model

Calculations for the Second and Higher Modes of the Bilinear Model

Chapter 17. The Solution Of The Propagation Equation In Terms Of Hankel Functions

Chapter 18. Attenuation Diagrams For Surface Ducts

Chapter 19. Approximate Analysis Of Guided Propagation In A Nonhomogeneous Atmosphere

Chapter 20. Some Theoretical Results On Nonstandard Propagation

Propagation in the Oceanic Surface Duct

Characteristic Values for a Continuously Varying Modified Index

Chapter 21. Perturbation Theory For An Exponential M Curve In Nonstandard Propagation

Abstract

Introduction

Formal Solution of the Problem by the Perturbation Method

Evaluation of ßnm(λ) as an Indefinite Integral

Properties of ßnm (λ)

Iteration Method of Solving for the Characteristic Values Dk and the Coefficients Akm

Expansion of Dk into a Power Series in α

Applicability of Perturbation Method to a More General Class of Μ Anomalies

Computational Program for the Exponential Model

Symbols for Use in Theory of Nonstandard Propagation

Chapter 22. First Order Estimation Of Radar Ranges Over The Open Ocean

Chapter 23. Convergence Effects In Reflections From Tropospheric Layers

Convergence Factor

Roughness Effect

Conclusions

Volume II Radio Wave Propagation Experiments

Part I Meteorology

Chapter 1. Meteorology — Theory

Modification of Warm Air by a Cold Water Surface

Diffusion Equation

Discussion of Procedure

Previous Investigations

Conclusion

Difficulties of Low-Level Diffusion Problems

Preliminary Results of Meteorological Measurements in Massachusetts Bay

Modification of Air Flowing Over Water

The M Deficit

Neutral Equilibrium

Unstable Equilibrium

Stable Equilibrium

Meteorology of the San Diego Transmission Experiments

Methods of Observation

The San Diego High Inversion

Shape of the Inversion Surface

Tables for Computing the Modified Index of Refraction, Μ

Introduction

Use of Tables

Procedure Used in Setting Up Tables

Diurnal Variation of the Gradient of Modified Μ Index

Temperature Lapse Rates Over Land

Temperature Lapse Rates Over the Sea

Vertical Vapor Pressure Gradients

Vertical M Gradient

Determining Fluctuations in Refractive Index Near Land or Sea

Gravitational Waves and Temperature Inversions

Analysis of Ducts in the Trade Wind Regions

Elevated Ducts

Surface Ducts

Experimental Evidence

Conclusions

Chapter 2. Meteorological Equipment For Short Wave

Meteorological Equipment for Propagation Studies

Outline of Problem

Wet and Dry Bulb Methods

Temperature and Humidity Resistance Elements

Circuit Design for Resistor Elements

Anemometers

Semipermanent Installations

Measurements on Board Planes and Dirigibles

Captive Balloon Sondes and Kites

Automatic Recording of Meteorological Soundings

Chapter 3. Meteorology — Forecasting

Forecasting Temperature and Moisture Distribution Over Massachusetts Bay

Meteorological Observations

Forecast Program

Army Analysis and Forecasts

How the Forecast is Made

Radar Propagation Forecasting

Application of Forecasting Techniques and Climatology

Radio-Meteorology

Specific Relationships Between Meteorological Elements and Radar Performance

Computed Climatological Information on Surface Ducts

Direct Indications of Nonstandard Conditions in the Western Pacific

Appendix

Part II Miscellaneous Experiments

Chapter 4. Reflection Coefficients

Reflection Coefficient Measurements at the Radiation Laboratory

Earth Constants in the Microwave Range

Reflection Coefficients

Summary of Experimental Investigations on Reflection

Specular Reflection and Scattering

Measurements of the Reflection Coefficient of Land at Centimeter Wavelengths, Carried Out at National Physical Laboratory

Chapter 5. Dielectric Constant, Absorption And Scattering

Absorption and Scattering of Microwaves by the Atmosphere

Introduction

Scattering and Absorption of Radio Waves by Spherical Particles

The Scattering Amplitudes an2 and bn2

The Attenuation of Radio Waves by Spherical Raindrops

Typical Data on Clouds, Fogs, and Rains

Attenuation by Idealized Precipitation Forms

The Scattering of Microwaves by Spherical Raindrops

Back Scattering (Echoes)

Summary

K-Band Absorption — Experimental

Absorption of K-Band Radiation by Water Vapor

K-Band Attenuation Due to Rainfall

Introduction

Rainfall Intensity

Radio Equipment

Analysis

Absorption of Microwaves by the Atmosphere, British Work

Dielectric Constant and Loss Factor of Liquid Water and the Atmosphere

Experimental Methods

Laboratory Measurements of Dielectric Properties

Chapter 6. Storm Detection

Storm Detection by Radar

Procedure

Weather Information

Correlations

Correlations with Echo

Correlations with Weather Stations

Résumé of Correlations

Fraction Detected by Radar of Total Quantity of Rainfall

Comparison with Ryde's Theory

The Best Frequency for Storm Detection

Ultimate Range — Greater Range of a Production Set

S-Band Radar Echoes from Snow

Chapter 7. Echoes And Targets

Fluctuations of Radar Echoes

Interference Concept

Assemblies of Random Scatterers

Ground Clutter

Targets Viewed Over Water

The Frequency Dependence of Sea Echo

The Dependence of Signal Threshold Power on Receiver Parameters

Radar Scattering Over Cross-Section Area

Chapter 8. Angle-Of-Arrival Measurements

Angle-of-Arrival Measurements in the X Band

Meteorological Analysis of Angle-of-Arrival Measurements

Purpose

Theory

Analysis of the BTL New York-to-Beer's Hill Circuit

The Angle of Arrival Deduced from Type Cases of Atmospheric Stratification

Comparison of Computed to Measured Angle of Arrival

Conclusions

Volume III The Propagation Of Radio Waves Through The Standard Atmosphere

Chapter 1. Propagation Of Radio Waves: Introduction And Objectives

Factors Influencing Propagation

Fundamental Problems and Limitations

Meaning of Propagation

Atmosphere Layers

Standard Atmosphere

Propagation in the Moist Standard Atmosphere

Propagation in Nonstandard Atmospheres

Radio Gain

Radio Gain of Doublet Antennas in Free Space

Survey of Propagation

Outline

Factors Modifying Transmission

General Nature of the Radiation Field

Typical Radio Gain Curves

Units and Frequency Ranges

Units

Symbols for Frequency Ranges

Chapter 2. Fundamental Relations

The Electric Doublet in Free Space

Radiation of an Electric Doublet

Reception by an Electric Doublet

Transmission Between Doublets in Free Space

Power Transmission Reciprocity

Radio Gain

Antenna Gain Polarization

The Reciprocity Principle

Receiver Sensitivity

Thermal Noise

Noise Figure

Receiver Sensitivity

Measurement of the Noise Figure

Sensitivity of Radar Receivers

Radar Cross Section and Gain

Radar Cross Section

Radar Gain

Chapter 3. Antennas

Fundamentals

Function of Antennas

Directive Antennas

Antenna Pattern Factors in Ground Reflection

Standing-Wave Antennas

Resonant Antennas

Traveling-Wave Antennas

Radiation Resistance

Influence of Near-by Conducting Bodies

Standing-Wave Antennas

Linear Antennas

Half-Wave Antennas

Half-Wave Dipole

Modifications of the Half-Wave Dipole

Multiple Half-Wave Long Antennas

Cophased Half-Wave Dipoles

Effects of Finite Diameter on Center-Fed Linear Antennas

Standing-Wave V Antennas

Traveling-Wave Antennas

Field and Pattern

Traveling-Wave V Antennas

Rhombic Antennas

Antenna Arrays

Principle of Arrays

Basic Types of Dipole Arrays

Two-Dipole Side-by-Side Array

Two-Dipole Colinear Array

One-Dimensional Array

Unidirectional Broadside and Colinear Arrays

Multidimensional Arrays

Binomial Arrays

Ring Arrays

Parasitic Reflectors and Directors

Parasitic Antennas

Half-Wave Dipole and Parasite

Multiple Parasites. Yagi Antennas

Reflecting Screens

Corner-Reflector Antenna

Parabolic Elements

Parabolic Reflectors

Horns

Types of Horns

Sectoral Horn with TE1,0 Wave

Chapter 4. Factors Influencing Transmission

Refraction

Survey

Snell's Law

Modified Refractive Index

Graphical Representation

Curvature Relationships

Alternate Method

Computation of Refractive Index

Atmospheric Stratification

Direct Determination of k

Ground Reflection

Ground Reflection and Coverage

Complexity of Reflection Problem

Plane Reflecting Surface

Fresnel's Formulas

The Complex Dielectric Constant of Water

Overland Transmission

Conductivity of Soil

Dielectric Constant of Soil

The Divergence Factor

Irregularity of Ground

Diffraction (General Survey)

Definition

Diffraction by Earth's Curvature

Diffraction by Terrain

Diffraction by Targets

Chapter 5. Calculation Of Radio Gain

Introduction

Objectives

Definitions Relative to Radio Gain

Factors Affecting Attenuation and Gain

Simplifying Assumptions

Curved-Earth Geometrical Relationships

Optical and Diffraction Regions

Nature of the Radiation Field in the Standard Atmosphere

Propagation Factors in the Interference Region

Propagation Factors

Spreading Effect

Interference

Imperfect Reflection

Divergence

Antenna Gain and Directivity

General Solution

Generalized Reflection Coefficient

Plane Earth

Use of Plane Earth Formula

Path Difference

Field Strength Equations

Spherical Earth

Measurement of Distance

Equivalent Heights

Angles

Determination of Reflection Point (d1)

Path Difference

Divergence Factor

Parameters p and q

Generalized Coordinates

Illustrative Calculations for the Optical Interference Region

Introduction

Problem of Type I. Radio Gain for Fixed Heights and Distance

Type II. Radio Gain Versus Receiver Height for Given Distance

Type III. Radio Gain Versus Distance for Given Antenna Heights

Type IV. Determination of Contours Along Which Gain Factor A Has a Given Value, the Transmitter Height and Wavelength Being Given

Maximum Range Versus Receiver (or Target) Height

Below the Interference Region

Analysis of the First Mode

Effect of Changing the Value of k

Graphs for the Case of the Dielectric Earth (δ≫1)

Sea Water, VHF, Vertical Polarization

Radio Gain Near the Line of Sight

General Solution for Vertical (or Horizontal) Dipole Over a Smooth Sphere

Sample Calculation for Very Dry Soil

Chapter 6. Coverage Diagrams

Definitions

Plane Earth

Field Strength

Angles of Lobe Maxima (Horizontal Polarization)

Angles of Lobe Maxima (Vertical Polarization)

Lobe Equation

Spherical Earth

Lobe Characteristics

The p-q Method (Horizontal Polarization)

Outline of Method

Construction of Range Loci

Construction of Path-Difference Loci

The u-v Method

Outline of Method

Construction of Lobes (Horizontal Polarization)

Construction of Lobes (Vertical Polarization)

Lobe-Angle Method (Horizontal Polarization)

Outline of Method

Basic Relations

Reflection-Point Curves

Lobe Angles with Horizontal

Use of Modified Divergence Factor

Construction of Lobes

Correction for Low Angles

Lobe-Angle Method (Vertical Polarization)

Angles of Lobe Maxima

Construction of Lobes

Generalized Coverage Diagrams (Horizontal Polarization)

Basic Parameters

Determination of d0

Determination of r

Use of Charts

Chapter 7. Propagation Aspects Of Equipment Operation

General Problem

Introduction

The Performance Figure and Efficiency

Effect of Reflection

Signal-to-Noise Ratio

Calibration of an A Scope

Free Space — High-Angle Coverage

Maximum Range Formulas

Deviation from Maximum of Beam

Performance Figure

Radar Cross Section

Low-Angle and Surface Coverage

Maximum Range

Ducts and Set Performance

Low Heights and Plane Earth Range

Maximum Range Versus Height Curves

Estimating Ship Size

Performance Check

Data on Equipment

Chapter 8. Diffraction By Terrain

Outline of Theory

Introduction

The Fresnel Diffraction Theory

Mechanism of Diffraction

The Straight Edge Formula

The Fresnel Integrals

Application to Straight Edge Polarization. Large Angles

Digression on Fresnel's Theory

Fresnel Zones

Diffraction by a Slot

Diffraction by Hills

Introduction

Criterion for Roughness

Diffraction by a Straight Ridge

Field Near the Line of Sight

Diffraction with Reflecting Ground

Diffraction by Coasts

Introduction

Level Site Near Coast

Equation for Field Strength

Example

Cliff Site

Chapter 9. Targets

Scattering Parameters

Radar Cross Section

Target Gain

Echo Constant

Equivalent Plate Area

Scattering Coefficient of Characteristic Length

Radar Cross Section of Simple Forms

Spheres

Cylinders

Plates

Corner Reflectors

Aircraft

Variation with Aspect

Measurement of σ

Chapter 10. Siting

General

Siting Requirements

Topography of Siting

Profiles

Geometrical Limits of Visibility

Horizon Formulas

Height of Obstacle

Extended Obstacle

Degree of Shielding

Permanent Echoes

Permanent Echo Diagrams

Shielding

Prediction of Permanent Echoes

Prediction by the Profile Method

Effect of Trees, Jungle, etc.

The Effect of Trees

The Effect of Jungles

Effect on Microwaves

Appendix. Transmission Experiments

Massachusetts Bay

Near San Diego

Arizona

Antigua, West Indies

England

Glossary

Bibliography

Appendix Bibliography

Bibliography — Volume I

Bibliography — Volume II

General Bibliography