NASA Contractor Report 3372 i 

-4 

High Accuracy Radiation Effici 

Measurement Techniques 

D. J. Kozakoff and J. M. Schuchardt 

CONTRACT NASS-33605 

JANUARY 1981 

MSA 
NASA Contractor Report 3372 

High Accuracy Radiation Efficiei 

Measurement Techniques 

D. J. Kozakoff and J. M. Schuchardt 

Georgia Institute of Techology 

Atlauta, Georgia 

Prepared for 

Marshall Space Flight Center 

under Contract NASS-33605 

National Aeronautics 

and Space Administration 

Scientific and Technical 

Information Branch 

1981 
FOREWORD 

This technical report was prepared by the Electromagnetics Laboratory 

of the Engineering Experiment Station, Georgia Institute of Technology, for 

the NASA Marshall Space Flight Center, Huntsville, Alabama. This represents 

a final technical report of a study of high accuracy antenna measurement 

methods applicable to the Solar Power Satellite (SPS) Subarrays. Contract 

technical monitor was R. A. Inmann, S & E, Electronics and Control Laboratory.' Report authors are D. J. Kozakoff and J. M. Schuchardt. 

The following individuals are recognized for their valuable contributions: Dr. E. B. Joy and C.E. Ryan of Georgia Tech in the area of nearfield measurement techniques; J. L. Detwiler and S. D. Davis of Scientific 

Atlanta in the area of antenna positioners and electronics; P. F. Wacker* 

of NBS; and B. L. Ulich of the University of Arizona for antenna gain 

calibration techniques; and W. Finnel of NASA MSFC in the area of SPS system 

philosophy. 

The views and conclusions contained in this document are those of the 

authors and should not be interpreted as necessarily representing the 

official policies, either expressed or implied, of the NASA Marshall Space 

Flight Center. 

* 

Recently retired 

ii 
TABLE OF CONTENTS 

Section Page 

FOREWORD ...................... 

ABSTRACT ...................... 

1.0 INTRODUCTION .................... 

2.0 MEASUREMENTS ERROR BUDGET .............. 

3.0 FAR-FIELD TECHNIQUES ................ 

3.1 Far-Field Error Budget Considerations ..... 

4.0 

5.0 

6.0 

7.0 

8.0 

9.0 

3.2 Ground Reflection Range . . . . . . . . . . . . 

3.3 Elevated Range . . . . . . . . . . . . . . . . . 

3.4 Power Density Considerations . . . . . . . . . . 

POSITIONER CONSIDERATIONS . . . . . . . . . . . . . . 

MEASUREMENT ELECTRONICS . . . . . . . . . . . . . . . 

5.1 Error Budget for Electronics . . . . . . . . . . 

5.2 System Configuration . . . . . . . . . . . . . . 

NEAR FIELD TECHNIQUES . . . . . . . . . . . . . . . . 

6.1 General Considerations . . . . . . . . . . . . . 

6.2 Scanner Considerations . . . . . . . . . . . . . 

COSTTRADEOFFS . . . . . . . . . . . . . . . . . . . 

7.1 Far-Field Facility Concept and Cost Estimate . . 

7.2 Near-Field Facility Concept and Cost Estimate . 

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . 

REFERENCES . . . . . . . . . . . . . . . . . . . . . 

Appendix A. Computed Fresnel Reflection Coefficient 

for Ground Reflection Range . . . . . . 

Appendix B. Ground Reflection Range Vertical'Field 

Intensity Distribution at Receive Site . 

Appendix C. Facility Cost Estimate Detail Breakdown 

Appendix D. Subarray Weight Estimates . . . . . . . 

Appendix E. Vertical Field Intensity at Receive Site 

for Mountain Top to Mountain Top Range . 

. . . . 1v 

. . . . v 

. . . . 1 

. . . . 4 

. . . . 6 

. . . . 6 

. . . . 6 

. . . . 12 

. . . . 12 

. . . . 19 

. . . . 29 

. . . . 29 

. . . . 29 

. . . . 32 

. . . . 32 

. . . . 34 

. . . . 39 

. . . . 39 

. . . . 39 

. . . . 47 

. . . . 48 

. . . . 50 

. . . . 54 

. . . . 67 

. . . . 72 

. . . . 76 

. . . 111 
LIST OF ILLUSTRATIONS 

Figure Page 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

15. 

16. 

17. 

18. 

19. 

20. 

21. 

22. 

23. 

24. 

Reference Antenna Subarray Configuration ............. 2 

Definition of Radiation Efficienty ................ 3 

Measurement Gain Loss Due to Quadratic Phase Error ........ 8 

Ground Reflection Range Concept ................. 10 

Ground Reflection Range Geometry Relations ............ 11 

Elevated Antenna Range Concept .................. 13 

Radiation Power Pattern Footprint for R = 500 m (0.31 miles) ... 15 

Radiation Power Pattern Footprint for R = 1,035 m (0.64 miles) . . 16 

Radiation Power Pattern Footprint for R = 2,100 m (1.3 miles) . . 17 

Radiation Power Pattern Footprint for R = 5,000 m (3.1 miles) . . 18 

Definition of Fractional Beam Power ............... 20 

Subarray Fractional Beam Power (0 - 1.5 degrees) ......... 21 

Subarray Fractional Beam Power (0 - 20 degrees) ......... 22 

Quantification of RDP Sample Accuracy Required .......... 23 

Antenna Positioner Mechanism for Far-Field SPS Antenna 

Pattern Measurements ....................... 28 

Measurement Equipment Block Diagram ............... 31 

Near-Field Measurements Equipment Block Diagram ......... 33 

Planar Scanner Mechanism Concept for Subarray Near-Field 

Measurements ........................... 35 

Cylindrical Scanner Concept for Subarray Near-Field 

Measurements ........................... 36 

Planar Scanner Mechanism Concept for Mechanical Module 

Near-Field Measurements ..................... 38 

Mountain Top to Mountain Top Far-Field Facility Concept 

(600 ft. height, 6-9 mile range) ................. 40 

Receive Site Detail for Far-Field Facility Concept ........ 41 

Transmit Site Detail for Far-Field Facility Concept ....... 42 

Planar Near-Field Measurement Facility Concept .......... 44 

iv 
LIST OF TABLES 

Table 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

Page 

Measurements Error Budget .................... 5 

Antenna Range Measurements Error Sub-budget ........... 7 

Summary of Antenna Gain Calibration Methods ........... 9 

Elevated Antenna Range Relations for Equal Transmit 

and Receive Antenna Heights ................... 14 

Subarray Pattern Measurement Criteria .............. 24 

Summary of Antenna Positioner Requirements ........... 25 

Summary of State-of-the-Art in Positioner Performance ...... 26 

Error Sub-budget for Receiver Electronics ............ 30 

Cost Summary for Far-Field Facility ............... 43 

Cost Summary for Near-Field Facility .............. 46 

V 
1.0 INTRODUCTION 

The SPS transmit antenna array described in the Reference System Report 

[l] is approximately l-kilometer in diameter and composed of 7,220 uniformly 

illuminated square subarrays lo- by lo-meters in size as illustrated in 

Figure 1. The lo- by lo-meter subarray is the lowest level of phase control 

for phase steering of the array. Antenna illumination aperture weighting 

is achieved by utilizing subarrays with a different number of 1 kilowatt 

klystrons. For instance, at the central portion of the array, subarrays 

with 32 klystrons are used while at the outer edges of the array, subarrays 

with 4 klystrons are employed. These relatively large subarray apertures, 

small half-power beamwidths, and the desire to accurately quantify antenna 

performance dictate the requirement for specialized measurements techniques. 

The emphasis of the high accuracy antenna measurements task reported 

herein was to study techniques to measure subarray radiation efficiency. 

Since klystrons, or solid state power modules in alternate designs, are an 

integral part of the subarray, the radiation efficiency definition shown in 

Figure 2 was adopted. That is, radiation efficiency is defined as the ratio 

of RF beam power to dc power to the klystrons. By use of power output 

monitors at each klystron, quantification of klystron and antenna structure 

radiation efficiency may be obtained. 

Specific objectives of this study include the following: 

1) For lo-meter square subarray panels, quantify considerations 

for measuring power in the transmit beam* and radiation efficiency to + 1% (+ 0.04 dB) accuracy. 

2) Evaluate measurement performance potential of far-field elevated 

and ground reflection ranges and near-field techniques. 

3) Identify the state-of-the-art of critical components and/or 

unique facilities required. 

4) Perform relative cost tradeoffs between candidate far-field and 

near-field facility concepts. 

Total klystron transmit power is 32 kW per subarray. 

1 
Step 

Number 

Subarrays 

Number 

K lystronsl 

Subarrays 

1 276 36 

2 632 30 

3 644 24 

4 628 20 

5 784 18 

6 900 12 

7 664 9 

8 612 8 

9 1,052 6 

10 1,028 4 

Totals 7,220 

Figure 1. Reference Antenna Subarrsy Configuration (only one quadrant 

shown) 

2 
P rad 

q= *. 

, where P rad = RF Power in Main Beam 

Figure 2. Definition of Radiation Efficiency 
2.0 MEASUREMENTS ERROR BUDGET 

In general, the RF and physical environment and the electronic instrumentation all contribute to the overall measurement error. Ideally, the RF 

source is stable in amplitude and frequency, the transmitted wave arrives at 

the receiver as a true plane wave free of objectionable reflections, and the 

atmospheric effects are negligible. The receiver must be ideal and error 

free, and the gain antenna reference is accurately known. In the real world, 

one must deal with the errors which occur as the instrumentation departs 

from the ideal performance listed above. 

For SPS subarray antenna pattern measurements, the critical error 

sources have been quantified into four categories shown in Table 1. The 

objective of this investigation is controlling these error sources to yield 

an overall gain uncertainty of f. 0.04 dB. Because of the large size of an 

SPS subarray (81.67-wavelengths at 2.45 GHz), antenna range effects are 

given the largest allowance in the error budget. The errors allocated to 

transmitter/receiver sources require advances in state-of-the-art of associated microwave electronics. However, even with currently available 

equipment, because of single frequency operation, and the fact that receiver 

and transmitter are phase-locked and thermally stabilized, errors can be 

accurately controlled. Use of a microcomputer will permit error compensation 

of such factors as the nonlinearity of receiver and detector. 

Controlling the antenna structure for measurement will require developing a cradle assembly that will hold the antenna rigid. Preliminary weight 

estimates indicate approximately 2.5 tons for a prototype subarray assembly. 

Ambient temperature, solar energy and wind effects can be controlled somewhat by selecting the measurement time period. However, unique test facilities are anticipated. For instance, shielding from the adverse external 

parameters listed above can be achieved through use of a large dome radome. 

Antenna measurements can be made with the test antenna either receiving 

or transmitting because of the reciprocity theorem. However, since in this 

case the SPS subarray is transmitting and the goal is to determine power in 

the transmit beam via beam integration, unique problems arise. The technical 

issues will be addressed in the following subsections. 

4 
Table 1. Measurements Error Budget 

ERROR SOURCE COMPONENTS ALLOWABLF VAIUF 1. COMMENTS 

ANTENNA RANGE FIELD UNIFORMITY 

QUADRATIC PHASE ERROR 

EXTRANEOUS REFLECTIONS 

! STANDARD GAIN ANTENNA 0.036 DB AN ADEQUATE GAIN STANDARD 

UNCERTAINTY HAS NOT YET BEEN IDENTIFIED I 

ATMOSPHERIC EFFECTS I REFERENCE RECEIVER MUST BE 

I NORMALIZE EFFECTS OF 

ATMOSPHERE 

AXIAL RATIO 

STRUCTURAL/ SPS ANTENNA RIGIDITY/ 

ENVIRONMENTAL STABILITY 

POSITIONER ERROR 0.01 DB 

WIND LOADING/THERMAL WIND LOADING/THERMAL CAN BE 

CONTROLLED BY.RADOME OVER 

TEST ANTENNA 

TRANSMITTER AMPLITUDE STABILITY PHASE LOCKED TECHNIQUES AND 

TEMPERATURE STABILIZATION 

0.01 DB MUST YIELD AMPLITUDE 

STABILITY OF O-007 DB 

FREQUENCY STABILITY 

RECEIVER PRECISION ATTENUATOR 

UNCERTAINTY 

~T~;~IJ;~oR CALIBRATED To 

. 

REFERENCE INPUT PHASE/ 

AMPLITUDE ERRORS 0.01 DB 

SIGNAL To NOISE RATIO S/N RATIO MUST EXCEED 40 DB 

FREQUENCY STABILITY 

DYNAMIC RANGE 

DETECTOR LINEARITY DETECTOR CALIBRATION 

CAN EXCEED 0.005 DB 

VSWR VSWR KEPT BELOW l-05 DB 

TOTAL RSS - 0.04 DB 
3.0 FAR-FIELD TECHNIQUES 

3.1 Far-field Error Budget Considerations 

The predominant error contributors for far-field measurements are 

1) field nonuniformity due to ground reflection, 2) gain loss due to quadratic 

phase error (near-field effects), and extraneous reflections. The National 

Bureau of Standards has investigated error budgets associated with far-field 

measurements [3]. For SPS, an adopted far-field antenna range error subbudget is shown in Table 2. Figure 3 plots the measurement gain loss due to 

quadratic phase error for a lo- by lo-meter SPS subarray panel. The large 

size of the subarray dictates a far-field criteria of greater than 6 DL/X to 

maintain quadratic phase error loss below 0.01 dB. 

A constraint on the absolute measurement accuracy of a far-field facility 

is calibration accuracy of a gain standard antenna. Commonly used methods 

of obtaining an antenna gain standard appear in references [3].through [7]; a 

summary of approximate measurement accuracy of the various techniques appears 

in Table 3. Here, the calibration accuracy of even the best methods are 

almost an order of magnitude larger than desired for SPS antenna measurements. 

With the availability of a high stability microwave receiver to be discussed 

later in this report, it is anticipated that gain calibration to + 0.02 dB - 

can be accomplished. 

3.2 Ground Reflection Range 

Consideration was given to use of a ground reflection range facility as illustrated in Figure 4. Here, transmit and receive tower heights are 

selected so that the reflection from the ground adds in phase to the direct 

ray path. Calculation of ground reflection coefficients in Appendix A show 

values very near unity for typical range .geometry. A negative feature is 

that a relatively large range is required to obtain a sufficiently flat 

amplitude wavefront in the vicinity of the receive antenna. 

Figure 5 relates the transmit and receive tower heights as a function of 

range. Under the constraint of a minimum and maximum tower height of 20 and 

100 feet, respectively, the minimum range of 3 miles based on near-field 

criteria; the shaded area indicates regions where satisfactory operation may 

be obtained. The criteria for a sufficiently flat amplitude wavefront over 

6 
Table 2. Antenna Range Measurements Error Sub-budget 

ERROR COMPONENT ALLOWABLE VALUE COMMENTS 

Field Uniformity 

Quadratic Phase Error 

Standard Gain Antenna 

Uncertainty 

Atmospheric Effects 

VSWR 

Extraneous Reflections 

RSS Subtotal 0.037 dB 

0.015 dB Maximum amplitude taper at 

edge of SPS subarray 

approx. 0.04 dB 

0.010 dB 

0.020 dB 

0.005 dB 

Requires range greater than 

6 D2/X 

Gain standard needs to be 

developed 

Atmospheric effects 

cancelled by reference 

0.005 dB VSWR loss calibrated out 

0.025 dB Extraneous reflections 

-57 dB down 
Gain Loos 

dB 

10 Meter Square 

SPS Subarray 

at 2.45 GHz 

1.0 

0.1 

OJOl 

0.001 

10K 

-., llangc Length (ft) 

I I kdtiplcs of D2/x 

3.5 1 2 4 8 16 

Figure 3. Measurement Gain Loss due to Quadratic Phase Error 
Table 3. Summary of Antenna Gain Calibration Methods 

METHOD FACILITY REQUIRED 

COMPUTATION NONE + 005 DB 

TWO-ANTENNA ELEVATED RANGE 2 0,2 DB 

METHOD 

THREE-ANTENNA ELEVATED RANGE 2 002 DB 

METHOD 

EXTRAPOLATION ELEVATED RANGE + 0,1 DB 

METHOD 

TWO-ANTENNA GROUND REFLECTION 2 0,3 DB 

METHOD RANGE 

TH;;;;&TENNA GROUND REFLECTION + 0,3 DB 

RANGE 

RA;;;II;;R I c ANECHOIC CHAMBER + O,l DB 

NEAR-FIELD ANECHOIC CHAMBER + 0,15 DB 

MEASUREMENT 

COMMENTS 

UNACCEPTABLE ACCURACY 

NEA;~;:;E~CORRECTION 
Figure 4. Ground Reflection Range Concept 
hr 

120 

80 

60 

20 

0 

(ft> ht = 20 

Range (Miles) 

2 4 6 8 

hr = Receive Antenna Height 

'^ = Transmir Aneenna Hei,aht 

ht = 45 

ht = 60 

ht = 100 

NOTE: Darkened 

area is allowable 

operating region 

for SPS subarray 

pattern measurements. 
the test zone may be deduced from the relationship shown in Figure 6. Here, 

it is seen that a maximum field nonuniformity error of 0.015 dB as allocated 

in the antenna range error sub-budget corresponds to a maximum illumination 

falloff at the receive antenna of 0.04 dB. Initial calculations indicate 

the performance of a 4-mile ground reflection range with receive and transmit 

tower heights of 30 and 70 feet, respectively, provided a wavefront within 

0.1 dB over a lo-meter zone, but only with use of high efficiency absorber 

barricades at the midrange point. A summary of calculation data appear in 

Appendix B. 

Use of a smaller receive antenna makes the utilization of a ground 

reflection range credible. However, the concept was precluded for further 

study because of the relatively high tower heights required in the far-field. 

3.3 Elevated Range 

Field nonuniformity can be controlled via an elevated range concept 

where the receive antenna null is placed at the midpoint reflection point as 

depicted in Figure 6. Tradeoff calculations indicate the required tower 

heights for elecated range distances greater than 6 D2/h are not practical, 

however, consideration for a mountain top to mountain top range with an 

elevation of 600 feet and a measurement range of 7 miles appears very attractive. A summary of the elevated range tradeoff calculations appear in Table 

4. 

3.4 Power Density Considerations 

Assuming the maximum klystron transmit RF power of 32 kW per subarray, a consideration was the power densities in local terrain between transmit and receive site to assess the hazard to personnel. At a range in the 

order of 0.31-miles the antenna footprint illustrated in Figure 7 has a peak 

power density of 179 mW/cm2. (The considered safety limit in the United 

States is 10 mW/cm2). Figures 8 and 9 plot the radiation power pattern 

footprint for R = 0.64 and 1.3 miles, respectively. Power densities approach 

the safe limit at about l-mile. Finally, Figure 10 illustrates power density 

at 3.1 miles where the peak level (1.86 mW/cm2) is well within the safe limit. 

12 
SPS 

Antenna 

Figure 6. Elevated Antenna Range Geometry 
Table 4. Elevated Antenna Range Relations for Equal Transmit and Receive Antenna Heights 

Half Power 

Antenna Height Antenna Diameter Beamwidth 

h (feet) (feet) (degrees) 

4 7.0 

100 8 3.5 

12 2.3 

15 1.85 

4 7.0 

600 8 3.5 

12 2.3 

15 1.85 

1st ~~11 Required 

Position Range 

degrees) R (miles) Comments 

9.3 0.23 "h" is Highest Practical 

4.7 

. 

0.46 Tower Height 

3.1 0.70 

2.5 0.87 

9.3 1.39 Mountain Top to Mountain 

4.7 2.76 Top Range 

3.1 / 4.20 

2.5 7.04 
, 179.03 

-142,21 

89,51 

44,76 

22838 

11819 

MW CM2 

= IA1 IllSTANCE 

480 490 500 510 529 530 METERS 

Figure 7. Radiation Power Pattern Footprint for R = 500 m (0.31 miles) 
/-46,15 M%jCM2 

R 

II ’ 

= RADIAL DISTANCE 

965 1025 1085 1145 METERS 

ii0 ii5 '20 MILES 

Figure 8. Radiation Power Pattern Footprint for R = 1,035 m (O.-64 mi-les) 
- 1 

4080 

3080 

g 2000 

g 1080 

m 

T 060 

s 

e 

4 -lJ,C 

-20,c 

-30,t 

-4O,( 

R = RADIAL DISTANCE I I 

1700 1900 2100 2530 2530 '2703 METERS 

1 I 1,UG 1,18 la30 1,43 1,55 1868 MILES 

Figure 9. Radiation Power Pattern Footprint for R = 2,100 m (1.3 miles) 
100,o 

80,O 

E 60,O 

8 40,o 

2 20,o 

m 

ii 0,o 

-$ -20,o 

E -40,o 

S -60,O 

-80,O 

-100,o 

86 MM/CM2 

48 

93 

46 

23 

12 

R = RADIAL DISTANCE F 

3,000 5,000 7;ooo 9,000 11,000 13,000 METERS 

280 LO 4,o !!A0 6,O 710 MILES 

Figure 10. Radiat,i,op Power Pattern Footprint for R = 5,000 m (3.1 miles) 
4.0 POSITIONER CONSIDERATIONS 

The antenna positioner considerations must include weight handling 

capability, positioning accuracy, and scan limit requirements. In Appendix 

D, an estimate of SPS subarray weight of 2.5 tons was arrived at on the 

basis of an array constructed of standard WR340 aluminum waveguide. An 

advanced technology array consisting of light weight Raytheon waveguide plus 

Varian 4k3SK klystrons was found to have approximately the same weight. 

The required positioner scan limits were evaluated on the basis of 

fractional beam power as defined in Figure 11. The fractional power in the 

beam based on a uniformly illuminated lo-meter square aperture is plotted 

through 1.5 and 20 degrees in Figures 12 and 13, respectively. Here, it is 

seen that the main beam (2 0.312 degrees) encompasses approximately 79 percent of the transmitted energy. Based on these results, a comcept was 

devised where a small angle positioner (SMAP) provides very accurate scan 

capability over a + 1.5 degree sector for the purpose of beam integration. 

A larger gimbal arrangement provides coarse positioning over the complete 

+ 20 degree sector. - Positioner hardware providing greater angular scan does 

not currently exist. From the plots of fractional beam power, approximately 

89% of the total rad-ated power is accounted for within + 1.5" scan; over 

99% of the power is radiated in the + 20 degree sector. 

Quantification of required positioner accuracy was achieved by studying 

the sample accuracy requirement for + 0.04 dB beam power measurement accuracy - 

illustrated in Figure 14. In Table 5, these results are applied to varied 

subarray sizes. For a lo-meter square subarray, it.is seen that a 19-bit 

encoder is required for resolution to about 0.001 degrees. 

Table 6 is a summary of the antenna positioner requirements. The large 

weight handling requirement and small angular accuracy requirements indicate 

that the positioner is a potential problem area based on units currently 

available. A survey was made of available antenna positioners, and is 

summarized in Table 7. The positional accuracy of off-the-shelf positioners 

is on the order of 0.005 degrees. Available positioner data indicate 

positioning of anything larger than the lo-meter subarray will not be 

19 
Antenna Voltage 

Pattern 

lane 

po f 2 E ('3,$) sine d$dB 

Fractional Beam Power - 0 

;2 2n x 100 

I I E2 (8.0) sine d+dB 

0 0 

Figure 11. Definition of Antenna Beam Parameters 

20 
‘I 

Figure 12. Subarray Fractional Beam Power (0 - 1.5 degrees) 
100’ 

90. 

80' 

20' 

10' 

0' 

0 

6 

5 10 15 20 

Angle from Peak of Beam (degrees) 

Figure 13. Subarray Fractional Beam Power (0 - 20 degrees) 
Elevation Angle 

Respect to Peak 

Azimuth Angle 

Respect to Peak 

Croas Sec;ion Through 

Main Beam 

Aseumlng power in the main beam is proportional to beam area, the 6 corresponding to 

1% power change is: 

or 

a( y?! + S)Z - 1.01i$y2 

6 - 0.005 (F, 

Figure 14. Quantification of RDP Sample Accuracy Required 

23 
Table 5. Subarray Pattern Measurement Criteria 

Data Array 

Size for 

Subarray Subarray Pattern 6 ENCODER f 1.5 Degrees Total Data 

Size Size Subarray for 1% Power Requirement 

(m) (wavelengths) BPBW* (deg) Change (deg) 

Square 

(Bits)** Raster**" k(g:d:f=e Comments 

1 8.167 6.24 0.016 16 188x188 35.344K 

3 24.502 2.081 0.0052 18 577x577 332.929K 

7 57.172 0.892 0.0022 19 1,364x1,364 1.86K 

10 81.67 0.624 0.0016 19 1,875x1,875 3.516M Encoder Quantification 

to 0.00097 degrees 

30 245.02 0.208 0.00052 21 5,770x5,770 33.293M Encoder not Available 

70 571.72 0.0892 0.00022 22 13,637x13,637 185.968M Encoder not Available 

100 816.7 0.0624 0.00016 23 18,750x18,750 351.562M Encoder not Avallable 

L * Uniform illumination 

**Quantification to approximately 6/Z 

*a* 

Sampled at 612 
Table 6. Summary of Antenna Positioner Requirements 

WEIGHT 

FOR SUBARRAY CONSTRUCTED OF STANDARD 

WR-340 ALUMINUM WAVEGUIDE (On98 LBS/FT), 

NO KLYSTRONS 

FOR LIGHT W IGHT PROTOTYPE WAVEGUIDE 

(11,8 LBSh 5 ), PLUS 50 VARIAN 4K3SK 

KLYSTRONS AT85 LBS EACH 

ENCODER 

TO PROVIDE 0,0018 -DEG, RESOLUTION 

REQUIRED FOR 1% POWER MEASUREMENT ACCURACY 

SCAN LIMITS 

COMPATIBLE WITH MAIN LOBE BEAM POWER 

PATTERN INTEGRATION 

2m5 TONS 

2,7 TONS 

19 BITS 

+1,5 - DEGREES 

(AZIMUTHS AND 

ELEVATION) 
Table 7. Summary of State-of-the-art in Positioner Performance 

I 85 

I 45 75 

Estimated 

Moment 

Arm* (ft) 

9.5 

7.5 

Maximum Subarray Wt. Cost*A* 

klbs 1 Tons Elev./Az. 1 SMAF' Total 

* Elevation over azimuth plus SMAP configuration. 

** NOTE: the series 85 has a maximum vertical load limit of 25 tons. 

*** 

November 1979 estimates. 
I- -- 

 

possible, based on the weight projections. 

A proposed state-of-the-art antenna positioner mechanism for far-field 

antenna measurements providing the required positioning accuracy is illustrated in Figure 15. 

27 
SPS Antenna 

Subarray 

EL 

19 

in 

\ 

; 

Small Angle EL/AZ 

Positioner (+1.5O> : \ 

/AZ Positioner \\ 

Bit Encoders 

EL andAzb6- 

/ : / 7 / : II :/ 

\ ‘a 

\\ ‘1 : 

2Q0 

‘-:: i 

ilm 

Figure 15. Antenna Positioner Mechanism for Far-Field SPS Antenna 

Pattern Measurements 

28 
5.0 MEASUREMENT ELECTRONICS 

5.1 Error Budget for Electronics 

An error sub-budget for receiver electronics is shown in Table 8. 

The state-of-the-art performance was based on available data for the Scientific Atlanta models 1711 and 1770 microwave receivers. The errors allocated 

to receZver sources in the SPS error budget are typically an*order of magnitude smaller then the state-of-the-art,performance and require advances in 

associated microwave electronics. However, even with currently available 

equipment, because of single frequency operation and the fact that receiver 

and transmitter are phase-locked and thermally stabilized, errors can be 

accurately controlled. 

5.2 System Configuration 

For SPS subarray antenna measurements, a proposed electronics 

measurements equipment block diagram is shown in Figure 16. Here, use of a 

microcomputer will permit error compensation of such factors such as nonlinearity of receiver and detector. Use of a high precision amplitude 

reference permits absolute received power measurements. The system is phase 

locked and the atmospheric effects are normalized out. Key development areas 

for this concept are a precision calibrated microwave variable attenuator, 

The precision absolute amplitude reference source, and a precision calibrated 

standard gain antenna. 

The availability of a computer compensated precision microwave receiver 

will permit advances in the state-of-the-art capability of calibrating 

standard gain reference antennas. The basic receiver system is applicable 

both to far-field and near-field measurements facilities. 

.-. .__-. __ _-- _ ..-_ -,- --- ~-..~---.- -.. 
ERROR 

SOURCE 

Table 8. Error Sub-budget for Receiver Electronics 

STATE-OF-THE-ART 

PERFORMANCE (1) 

S;;DKEEfOR 

COMMENTS 

LINEARITY 0.05 DB/~O DB 

IF AMPLIFIER 0.05 DB/"C 

DRIFT 

CABLE LOSSES 0*2%/°C 

CROSSTALK 0.1 DB FOR 

40 DB DIFFERENCE 

BETWEEN CHANNELS 

AMPLITUDE 0.1 DB OVER 

RESOLUTION 80 DB DYNAMIC 

RANGE (2) 

S/N RATIO 

LINE VOLTAGE 0.02 DB FOR 1% 

VARIATION ~;;Y;~~IN LINE 

PRECISION IF/ + 0.2 DB FOR 

RF ATTENUATORS. TO DB STEPS 

VSWR 0*15 DB FOR 

VSWR OF l-3:1 

RSS TOTAL 

NOTES: (1) DATA BASED ON 

S/A 1711 AND 1770 

RECEIVERS 

(2) DATA BASED ON 

S/A 1832A 

AMPLITUDE DISPLAY 

UNIT 

0.005 DB MICROCOMPUTER CALIBRATION REQUIRED 

0.002 DB TEMP. STABILIZATION AND MICROCOMPUTER 

0.002 DB 

0.003 DB 

CALIBRATION REQUIRED 

PRECISION AMPLITUDE REFERENCE WILL NORMALIZE 

CABLE LOSS VARIATIONS 

MICROCOMPUTER COMPENSATION REQUIRED 

0.001 DB 17 BIT PARALLEL BCD RECEIVER OUTPUTS REQUIRED 

FOR 0.001 DB RESOLUTION 

0.005 DB NARROW IF BW REQUIRED TO EXTEND DYNAMIC RANGE 

0.001 DB VOLTAGE REGULATION AND MICROCOMPUTER COMPENSATION REQUIRED 

0.005 DB MICROCOMPUTER COMPENSATION MAY BE REQUIRED 

0.002 DB ALL VSWR's MAINTAINED BELOW 1.05 AND/OR 

CALIBRATED OUT 

0.01 DB 
1 . 

Precision 

Calibrated 

Attenuator Temperature Stabilized 

,^^^-I l-Em 

Calibrated r-7-'- ---- - ------------ 7 

2.45 GHz m Temperature! 

AC Voltage 

I 

1 Attenuator 1' I- 1 

ference 1 hhase l I 

Swztch rj-B 

I 

(rr) ’ 

I ‘L L----m - 

Microwavdi 

Receiver $ 

Transmit Reference Module 

eh 2.7 GHz ~ $-&;;;T-@--;i;;-j 

-.,,-,,------1 0.25 GHz Reference L---------.---w --------w-1 

Digital Control Signals 

Figure 16. Measurement Equipment Block Diagram 

_. .--..- _ -.- --. _ ._ ______- . .._..- 
-. _--.. .- ._ ,.-‘- --- I _ .‘A _^ ._ _. _.- . - _ _ . - 

6.0 NEAR-FIELD TECHNIQUES 

6.1 General Considerations 

Near-field techniques utilize a calibrated probe antenna to measure 

the amplitude and phase of the field close to the antenna aperture. Two 

orthogonally-polarized probes, or a single linear-polarized probe oriented in 

the vertical and horizontal directions are used, together with a probe compensation technique [8,9] to obtain the complete radiation characteristics 

of the antenna under test (ATJT). This measurement procedure requires an 

automated facility capable of reading the measured data in digital form for 

the required computer processing. 

The basic elements of a near-field measurements facility consist of a 

precision scanner mechanism, calibrated field probe, microwave receiver and 

digital computer. An equipment block diagram is shown in Figure 17. The 

planar near-field measurement technique is particularly attractive for SPS 

since the SPS subarray does not have to be moved during the measurement, 

. I.e., only the probe antenna is moved. The approach can be implemented at 

high power levels and in an indoor facility permitting all weather operation. 

Recent work at Georgia Tech has demonstrated that accurate antenna 

patterns can be obtained via near-field techniques [4,5]. The National 

Bureau of Standards has shown that for planar near-field scanning, the nearfield derived patterns are more accurate than far-field measured patterns 

when considering all error sources involved [6]. 

Martin Marietta [12] has implemented an indoor planar near-field 

measurements facility capable of measurement of antennas up to 50-foot in 

diameter. The benefits of this facility include all weather operation, a 

thermally controlled environment (maintained within 2“F), and an RF anechoic 

environment. RCA has also implemented an indoor planar near-field facility 

for acceptance testing of the AN/SPY-l phased array antenna for the AEGIS 

system [13]. 

In order to obtain accurate polarization information on the antenna 

pattern, the polarization characteristics of the measurement probe must be 

carefully characterized over the maximum possible dynamic range. Work at 

32 

__- .- --_-- -.-i-c-- ---- -- --- 

c. 
a600 lAUD 

SYNca4RoNWS ; 

YICROROV4 C SCANNER 

WITH DISK 

cwMuNIcATlffl9 

POSITION 

OPEAAtlHO SYSTEM - CONTROLLER a 

. 

0 0 

. I I 

- YICROWAVE A/D 

RECEIVER - CONVERTER 

REFERENCE 

SIGNAL 

PLANAR 

SCANNER w 

ASSEMBLY 

I 

I TRANSMITTED SIGNAL 

Figure 17. Near-Field Measurements Equipment Block Diagram 

33 
RCA [14] has also indicated that careful probe polarization design is necessary too if a very accurate gain determination is required. For instance, 

assuming an SPS antenna polarization ratio of 30 dB, a probe polarization 

ratio of 20 dB will result in a gain measurements error of approximately 0.25 

dB. Thus, a very stringent requirement is placed on probe polarization 

ratio; a requirement of 30 dB, or better, is anticipated. 

6.2 Scanner Considerations 

In order to obtain a complete representation of the antenna pattern 

from a planar or cylindrical near-field scan, the field is normally sampled 

at l/2 wavelength intervals along the linear scan dimension. If the antenna 

under test is electrically large, the required Fourier transform processing 

can become burdensome. However, it has been shown that the sample spacing 

can be increased by almost an order of magnitude if only the main-beam and 

first sidelobes are to be defined [10,15]. 

A planar scanner concept applicable to SPS subarray antenna measurements 

is shown in Figure 18. An investigation of error contributors to near-field 

measurements [16] has indicated that the required probe X-, Y- and Zpositioning accuracy is X/200 for pattern accuracy compatible with SPS 

measurement objectives. 

Near-field measurements can also be implemented by employing cylindrical 

or spherical probe scanning. A previous study performed by Georgia Tech for 

NASA indicated that the cylindrical near-field technique is attractive for 

the measurement of electrically and physically large ground station antennas 

[161. A cylindrical near-field scanner concept for subarray near-field 

measurements.is shown in Figure 19. However, in the spherical technique, it 

is necessary to move the AUT while holding the probe fixed. In the case of 

SPS, spherical near-field scanning cannot be used because of the difficulty 

of gimbaling the heavy subarray in order to scan over a full sphere. However, planar and cylindrical scanning concepts are applicable. Either system 

has potential to be implemented outdoors, however, the effects of thermal 

changes on scanning mechanism and instrumentation and the fact that an outdoor facility is subject to environmental conditions, makes an indoor nearfield facility far more attractive and practical. 

34 
’ 

. . 

. . 

. .’ 

. . ..- 

, _. ;..: :. (8 

. .:; . ...-..! 

. . .J -:.: 

: 

r.:... 

: :‘. A;:;...: ,,. 

* ‘. L., *.: 

.,J 

--. .. . 

Figure 18. Planar Scanner Mechanism Concept for Subarray Near-Field 

Measurements 

35 
.‘..’ 

--..; 1 

Figure 19. Cylindrical Scanner Concept for Subarray Near-Field 

Measurements 

36 
r- - 

Tradeoff studies at Georgia Tech have suggested that the planar nearfield concept has potential for array measurements of an SPS mechanical 

module (30 square meters). A large scanner concept applicable to mechanical 

module testing is shown in Figure 20. Problem areas to be resolved include 

computer requirements and the complexity of scanning over a much larger surface with acceptable precision. It may be possible to scan over a smaller 

area of the array - such as a quadrant with one positioner and then move 

either the scanner or the array. 

37 
Figure 20. Planar Scanner Mechanism Concept for Mechanical 

Module Near-Field Measurements 

38 
7.0 COST TRADEOFFS 

7.1 Far-Field Facility Concept and Cost Estimate 

To assess the relative cost between far-field and near-field facility concepts, the far-field mountain top to mountain top facility illustrated in Figure 21 was studied. A detail cost breakdown appears in 

Appendix C. The receive and transmit site facilities are shown in Figures 

22 and 23, respectively. The mechanical design of the SPS subarray support 

tower was based on handling maximum windloading in the order of 80 mph. 

Utilizing the microwave electronics system depicted prior in Figure 16, 

the total cost estimate for the far-field facility is summarized in Table 9. 

7.2 Near-Field Facility Concept and Cost Estimate 

Previous studies at Georgia Tech have considered the cost tradeoffs of far-field measurements versus a near-field measurement [8,11]. The 

results of these investigations for both large phased array and large 

reflector antennas demonstrate that costs are less for the near-field facility, and that the projected measurement accuracy is superior to that which 

could be obtained on a high quality far-field antenna measurement range. 

However, the capital investment and operating costs of the near-field 

facility are functions of the required measurement accuracy. For example, 

if the on-axis antenna gain is to be determined to within 0.01 dB, the 

measurement probe axial position accuracy must be within 0.01 wavelength, 

i.e., 0.048 inches for the SPS. Also, the scan width-to-diameter ratio 

must be at least 1.5. Thus, this requirement has a direct effect on the 

mechanical design of the near-field measurement system. 

Based on the linear planar scanner mechanism shown prior in Figure 18, 

The near-field measurements facility depicted in Figure 24 was conceived. 

This system presumes ceiling of measurement chamber covered with microwave 

absorber 'material, side walls are partially covered. The purpose of the 

antenna handling mechanism is for array set-up and handling. The system 

further presumes full high power testing will be employed. 

39 
SPS 

SUBARRAY 

Figure 21. Mountain Top to Mountain Top Far-Field Facility Concept 

(600 ft. height, 6-9 mile range) 

40 
Figure 22. Receive Site Detail for Far-Field Facility Concept 

41 
Figure 23. Transmit Site Detail for Far-Field Facility Concept 

42 
Table 9. Cost Summary for Far-Field Facility 

RECEIVE/INSTRUMENTATION ELECTRONICS,,,,,,,,.359,8K 

TRANSMIT SITE BUILDING.,,.,.,,.,,,,,,.,,,,,, 24,OK 

TOWER FOR SPS S~~~~~~~,~~,~,~~,~~~1(1111(.1112010K 

RECEIVE SITE BuILDING,~,,,,,,~,,~,,,,,,,,,,,~~~,~K 

PRECISION ANTENNA PosITIoNER,,,,,,,,,,,,,,,,~~~,~K 

TOTAL $1,095,6K 

43 
HANDLING MECHANISM 

Figure 24. Planar Near-Field Measurement Facility Concept 

44 
Utilizing key elements of the microwave electronics de<icted prior in 

Figure 16, .an appropriate microcomputer, and based on the facility concept 

depicted in Figure 24, a cost estimate of the near-field concept is shown in 

Table 10. This data indicates projected costs for a near-field facility to 

be only 5-percent greater than the far-field measurements facility concept. 

45 
Table 10. Cost Summary for Near-Field Facility 

RECEIVE/INSTRUMENTATION ~LEcTR~NIC~,,,,,,,,,.,,,,,~~~.~~ 

STEEL BUILDING 1,11111,,11,,1,111111111,11,,,llllll 378,OK 

MICROWAVE ABSORBER MATERIAL,,,~,~~,,,,,,,,,,,,,,,.~~~,~~ 

ANTENNA HANDLING MECHANISM,,,,,,.,,,,,,,,,.,,,,,,, 92,OK 

LINEAR X-Y SCANNER 1111II,,,I,IIII,I,I,II,I11111111 260,0K 

TOTAL $1,140,2K 

46 
8.0 CONCLUSIONS 

To measure SPS antenna subarray beam power to within l%, it was found 

that elevated ranges can meet all known requirements. Many potential sites 

having ranges greater than the required 3-mile minimum are available. 

Because of the large electrical size of the SPS subarray panels and the 

requirement for high accuracy measurements, specialized facilities are required. Most critical measurement error sources have been identified for 

both conventional far-field and near-field techniques. Although the adopted 

error budget requires advances in state-of-the-art of microwave instrumentation, the requirements appear feasible based on extrapolation from today's 

technology. 

Key development items identified include an adequate reference antenna 

gain standard, a stable precision amplitude (oscillator) standard, and a 

computer compensated and calibrated phase locked microwave receiver. 

The possibility of utilizing near-field measurement techniques was 

studied. With adequate probe calibration and precision mechanical scanning, 

full 30 by 30 meter mechanical module antenna measurements may be performed. 

The performance and relative cost considerations between planar near-field 

and conventional far-field methods indicated the overall cost to be roughly 

the same. 

47 
9.0 REFERENCES 

[II "Satellite Power System Concept Development and Evaluation Program 

Reference System Report," U.S. Department of Energy Report DOE/ER-0023, 

Washington, D.C. 20545, October 1978. 

[21, "Ground Plane Angenna Range Performance Measured and Calculated," 

J.H. Zickgraf, 1974 IEEE/AP-S Symposium, Georgia Tech, June 1974. 

[31 "Accuracy Considerations in the Measurement of the Power Gain of a 

Large Microwave Antenna," M. Kanda, 1974 IEEE/AP-S Symposium, Georgia 

Tech, Atlanta, June 1974. 

[41 "Accurate Measurement of Antenna Gain and Polarization at Reduced 

Distances by an Extrapolation Technique," A.C. Newell, R.C. Baird and 

P.F. Wacker, IEEE Transactions on Antennas and Propagation, July 1973. 

[51 "Gain Calibration of a Horn Antenna Using Pattern Integration," 

A. Ludwig, J. Hardy and R. Norman, Technical Report 32-1572, Jet 

Propulsion Laboratory, Pasedena, California, October 1972. 

[61 "A Radiometric Antenna Gain Calibration Method," B.L. Ulich, IEEE 

Transactions on Antenna and Propagation, March 1977. 

[71 "Upper-Bound Errors in Far-Field Antenna Parameters Determined from 

Planar Near-Field Measurements: Part 1 - Analysis," A.D. Kaghijian, 

NBS Technical Note 667, October 1975. 

[81 "Correction of Near-Field Antenna Measurements Made with an Arbitrary 

But Known Measuring Antenna," D.M. Kerns, Electronics Letters, Vol. 6, 

May 1970. 

[91 "Plane Wave Scattering Matrix Theory of Antenna and Antenna-Antenna 

Interaction: Formulation and Application," D.M. Kerns, Journal of 

Research of the Nation Bureau of Standards, Vol. 80B, No. 1, January 

1976. 

[lOI "Probe Compensated Near-Field Measurements Basic Theory, Numerical 

Techniques, Accuracy," W.M. Leach, Jr., E.B. Joy and D.T. Paris, 

IEEE/AP-S Symposium, Georgia Tech, June 1974. 

[Ill "Automated Near-Field Measurements to Obtain Far-Field Patterns of 

Aperture Antennas and Phased Attays," H.A. Ecker, et al, IEEE/AP-S 

Symposium, Georgia Tech, June 1974. 

[12] Near-Field Pattern Measurement Facility," C.E. Kirchoff, 1979 Antenna 

Applications Symposium, U. of Illinois, September 1979. 

1131 "Implementing a Near-Field Antenna Test Facility," W.A. Harmening, 

Microwave Journal, Vol. 22, No. 9, September 1979. 

48 
[I41 "Automated Near-Field Test Set for Phased Array Production," 

D. Staiman, 1979 Antenna Applications Symposium, U. of Illinois, 

September 1979. 

[I51 "A Study of the Application of Near-Field Measurements for NASA 

Requirements," B.J. Gown, C.E. Ryan, Jr., A.L. Bridges and J.D. Adams, 

Final Engineering Report, Contract NAS5-2234, Georgia Institute of 

Technology, March 1976. 

[I61 "An Investigation of the Accuracy of Far-Field Radiation Patterns 

Determined from Near-Field Measurements," G.P. Rodrigue, E.B. Joy and 

C.P. Burns, Final Report on Georgia Tech Project E-21-621, for U.S. 

Army Missile Command, Redstone Arsenal, Alabama, August 1973. 

r171 "Considerations for High Accuracy Radiation Efficiency Measurements 

for the Solar Power Satellite Subarrays," D.J. Kozakoff, J.M. 

Schuchardt and C.E. Ryan, Proceedings of the Solar Power Satellite 

Workshop on Microwave Power Transmission and Reception, N.A.S.A. 

Johnson Space Center, Houston, Texas 77058, January 1980. 

49 
Appendix A. Computed Fresnel Reflection Coefficient for Ground Reflection 

Range 

50 
Appendix A. Computed Fresnel Reflection Coefficient for Ground Reflection 

Range 

Using the nominal permittivity and conductivity values for moist soil, 

and the formulas for Fresnel Reflection Coefficients appearing in Zickgraf ' 

[2], the following results are obtained 

E 

0 

= 9.954 x lo-l2 f/m 

E = 44.27 x 10 -It2 f/m 

u = 0.1 mhos/m 

The total ground permittivity may be expressed in the form 

E 

I 

= E r r - jcz 

where E' = 44.27 x lo-l2 = 5 o 

r 8.854 x lo--l2 

. 

At the SPS operating frequency: 

E” = a 

w = 6.496 x lo-l2 f/m 

II 

E = 6.496 x lo-l2 = o 734 

r 8.854 x 10 -12 ' 

or, E r 

= 5.0 - j 0.734. 

Using this value for complex permittivity of moist soil, the Fresnel Reflection coefficients were computed values are shown in Table A-l and are plotted 

in Figure A-l. 

51 
Table A-l 

Grazing Angle Fresnel Reflection 

(degrees) (Vertical Polarization) 

0 1.00 1.00 

1 0.94 0.99 

2 0.88 0.98 

5 0.73 0.95 

10 0.54 0.90 

15 0.41 IO.85 

20 0.35 0.81 

Surface Reflection Value 

Coefficient 

(Horizontal 

Polarization) 

52 
1.00 

0.90 

0.80 

0.70 

0.60 

0.50 

0.40 

0.30 

0.20 

0.10 

rc 

i = 2.45 GHz 

1 I L I I I I 1 

0 2 4 6 8 10 12 14 

Grazing Angle (Degrees) 

Figure A-l. Fresnel Reflection Coefficients for Moist Soil (cr = 5, u =-0.1 mhos/meter) 
Appendix B. Ground Reflection Range Vertical Field Intensity 

Distribution at Receive Site 

Some general trends in field non-uniformity were studied by an analysis 

of vertical field intensity at the receive site of a ground reflection 

range. Figures B-l through B-3 investigate the effect of absorber barricades 

at the midpoint of a 0.5-mile ground reflection range; the transmit antenna 

HPBW was taken as 3.5-degrees. A -30 dB absorber barricade is pushing the 

state-of-the-art. 

The effect of transmit antenna HPBW was studied in the data of Figures 

B-4 through B-6 for the half-mile range. Figures B-7 and B-8 plot the 

vertical field intensity for a 0.5-mile range for transmit antenna heights 

of 45 and go-feet, respectively; transmit antenna HPBW is 2.3-degrees. 

Figure B-9 is similar data but for a transmit antenna HPBW of 3.5 degrees. 

For a transmit antenna HPBW of 3.5-degrees, Figures B-10 and B-11 plot 

the vertical field intensity at ranges of 1 and 2 miles, respectively. 

Figure B-12 examines a 4-mile range where an absorber barricade of -30 

dB is employed. This particular case may be credible for SPS subarray 

measurements. 

54 
Relative 

60 

Figure B-l 

90 hr (feet) 

Vertical Field Intensity for 0.5-mile Range for ht = 8.83-feet, HPBW = 3.5-degrees; 

No Absorber Barricade 
Relative 

Voltage 

1.0 

0.8 

0.6 

0.4 

0.2 

0.0 

- _. .._- 

,__._.._ -.._- __ . _ _ 

30 6b 90 hr (feet) 

Figure B-2 

Vertical Field Intensity for 0.5-mile Range for ht = 8.83 feet, HPBW = 3.5-degrees; 

-20 dB Absorber Barricade 
Relative 

Voltage 

1.0 . . . _. _. . . . i:: .__... _. . . . _. . . . . . . . . . . . . . . . _. . _. _. _. . . . . . . . ., . _. -. . . . _. _. . _. . . -. . . . . . . . . _. . . . . ., . . .._. . _. _. _. . _. -. . . . . _. _. _...." . . . . . . . . . . . . . . _. . -. . -. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

+------/ 

0.8 ; ..- -.. -. - 

0.6 i-----.---.-mm.. __....._ -._ .- _._ __ _ 

0.4 ;...-...-.---.. .~ -.___.-.. _._ .- __ 

0.2 ~+---~-- - __.. ._ . __ _ 

0 I 

O.O!$. . _........................._._.___. _ .,I'.I-.'~-:~'I _... +. _....._.- .._. . . . . -: . . . . . . . . . . . . . . . . .._.._.-... f-.: ._... ~ . . . . . . . . . - . . . . . . . . . . . t - . . . . . . . . . . . y . . . . - . . . . . \ . . . -'-'-'- . . . . . . . . . . . . . . . . . . . . . . . . . . ...'.. 

I 

0 30 60 90 hr (feet) 

Figure B-3 

Vertical Field Intensity for 0.5-mile Range for ht = 8.83 feet, HPBW = 3.5-degrees; 

-30 dB Absorber Barricade 
Relative 

Voltage 

1. 0 5" _.,_ _ -..w.......L..... . ..-.I-...-. -..-.. -..... w . . . . . . ..-..*-.. -.... . . . ..,_. -.-.--..e. -..I..........- 

JbI 

0.0 ‘f J-s...d-........---- t --S......,.....,~.....A 

i 

..-.; ..--. (..I L.l.._.. .j . . ..-. .i I.... ,* ..-‘rn.... F 

0 30 60 90 120 

hr (feet) 

Figure B-4 

Vertical Field Intensity for 0.5-mile Range for h, = 25-feet, NPBW = 2.3 degrees 
Relative Voltage 

1.0 -c w...--... s....Lm..-..e. -..._._.-.......--.~..~~_..-...-I.--.-... --.-.I.....-- 1.w.B..-.....*-m-w..... 

I I 

41 * 

0.0 l.p..w~ ..-.....- *..--+,, ---. ‘..? ----.. + -..--..I.: ..I.__ --.p _____C.. A ---I-- f 

0 30 60 90 120 

hr (feet) 

Figure B-5 

Vertical Field Intensity for 0.5-mile Range for h, = 25 feet, HPBW - 3.5-degrees 
Relative Voltage 

0.0 

+-~,,A.. rnw-.... I,_.. &* _..I._... i...... ,: . . . . . . . . . ..-rn -..-I. - I........ b .3L-.L.... -i&-j! 

0 30 60 90 120 

hr (feet) 

Figure B-6 

Vertical Field Intensity for 0.5-mile Range for ht = 25 feet, HPBW = T.°rees 
Relative 

Voltage 

1.0 -7 . ..-........*.*...*................... * I.......... I . . ..I. ..I... -.- . ..-.... .m.....w....... w,m.....m... c ,...,..~.....~.....~..,...........,..l....... '""L'.. . . . . . . . . . * . . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . 

. 

i 

I 

0.5” 

0.0 -1 

i I\ 

. 

I I... B...e...m...w...s... -I I. . . . . -.s.LI.,..- . . . . . . s. -t .-llll....lllll.. +w...w.- . . ..s... - . . . . ..a. c .-.-M”--..-m.l--L &-.-~--e-..-.- -m...w...-Wm.-... d 

120 

hr (feet) 

Figure B-7 

Vertical Field Intensity for 0.5-mile Range for ht = 45 feet, HPBW = 2.3-degrees. 
Relative Voltage 

0 30 60 90 120 150 180 

hr (feet) 

Figure B-8 

Vertical Field Intensity for 0.5-mile Range for ht = 95 feet, JJPBW = 2.3-degrees 
Relative 

Voltage 

I 

, 

I 

I 

hr (feet) 

Figure B-9 

Vertical Field Intensity for 0.5-mile Range for ht = 95 feet, HPBW = 3.5-degrees 
Relative Voltage 

1.0 

0.5 

0.0 

0 30 60 90 120 

hr (feet) 

Figure B-10 

Vertical Field Intensity for l-mile Range for h, = 17.7 feet, HPBW = 3.5-degrees 
65 

..------ _ :- 

I y--‘-;-~--.” 

.--. .-_- 

---.. . .- -.- 

. . . . 
- u 

., , - ), ‘ -. 

--- - -- , -~-. 

.c: 

:_ .’ i. 

z . 
Appendix C. Facility Cost Estimate Breakdown Detail 

The purpose of this appendix is to provide greater detail in the cost 

tradeoffs between the candidate antenna measurements facilities. Figure C-l 

is a summary of hardware and cost requirements for the far-field facility 

concept. Figure C-2 is similar data for the proposed near-field facility. 
Figure C-l 

SUMMARY OF HARDWARE AND COST REQUIREMENTS 

FOR FAR-FIELD FACILITY CONCEPT 

RECEIVE/TRANSMIT ELECTRONICS . . . . . . . . . . . . . . . . . . . .$359.8K 

S/A 1774 3-channel receiver 

special receiver mods 

S/A 1871A digital freq. display 

S/A 1832 digital amp. display 

(two @ 4.2K ea.> 

Andrew 12 ft. dish antennas 

(two @ 5.3K ea.> 

Stable RF amplitude ref. unit 

Receive ref. module 

Ultra-precision RF atten. 

Connectors, waveguide, coax. 

Equip. rack, hardware 

Transmit ref. module 

J.-U? 1000/45 computer 

HP 9862 plotter 

BP 9881A line printer 

UHF ref..system: 

140 tel. poles @ $100 

Coax line (7-miles) 

CATV line amps 

4 mm labor for installation 

@ 3K/mm) 

$42K 

1OK 

ll.lK 

8.4K 

10.6K 

50K 

28K 

50K 

5K 

5K 

27.5K 

46.5K 

3.2K 

8K 

14K 

18.5K 

10K 

12K 

TRANSMIT SITE EQUIPMENT BUILDING . . . . . . . . . . . . . . . . . .$24.OK 

400 sq. ft. @ $6O/sq. ft. (on 4-inch slab, 

insulated, heat and air cond., AC pwr., etc.) 

TOWER FOR SPS ANTENNA . . . . . . . . . . . . . . . . . . . . . . .$120.OK 

Structural materials (20 ft. 

high, 36.2 klb structure) 

Deck, rail, stairs 

Concrete foundation 

Labor: 

Engineer (1 mm @ $5K) 

Draftsman (3 mm @ 3K) 

Riveter/welder/machinist 

(16 mm @ 4K) 

$17K 

3K 

22K 

5K 

9K 

64K 

68 
RECEIVE SITE BUILDING . . . . . . . . . . . . . . . . . . . . . . .$107,8K 

Foundation & 10 ft. tall base 

to raise bldg. to 20 ft. $4OK 

1000 sq. ft. bldg. at $6O/sq. ft. 

(insulated, heated, air cond., 

AC power, plumbing, etc.) 6OK 

Two antenna mounts 

(700 lb. steel) 1.3K 

Labor: 

Engineer (0.5 mm @ 5K) 2.5K 

Machinist (1 mm @ 4K) 4.OK 

SPS PRECISION ANTENNA POSITIONER SYSTEM . . . . . . . . . . . . . .$484K 

S/A model with SMAP $440K 

(19 bit encoder readouts) 

S/A 1843 digital dual synchro 

displays (two @ 7.4K) BCD out 14.8K 

S/A 4116A remote control unit 2.4K 

S/A 4168A position control unit 

(two @ 13.4K) 26.8K 

TOTAL $1,095.6K 

69 
Figure C-2 

SUMMARY OF HARDWARE AND COST REQUIREMENTS 

FOR PLANAR NEAR-FIELD FACILITY CONCEPT 

RECEIVE/TRANSMIT ELECTRONICS . . . . . . . . . . . . . . . . . . . .$254.2K 

S/A 1774 3-channel receiver 

special receiver mods 

S/A 187l.A digital freq. display 

S/A 1832 digital ampl. display 

(two @ 5.3K ea.) 

Stable RF amplitude ref. unit 

ultra-precision RF atten. 

Connectors, waveguide, coax 

Equipment rack, hardware 

Signal generator 

Oscillator synchronizer 

HP 1000/45 Computer 

HP 9862 Plotter 

HP 988lA line printer 

Direc. compler & misc. parts 

Horn probe antenna 

Absorber to mask scanner 

$42K 

10K 

ll.lK 

10.6K 

50K 

50K 

3K 

4K 

4.5K 

3K 

46.5K 

3.2K 

8K 

2K 

0.5K 

8K 

STEEL BUILDING . . . . . . . . . . . . . . . . . . . . . . . . . . . $378~ 

Anechoic chamber portion on 

6-inch slab, insulated, heat 

& air cond., AC power, etc. 

(3600 sq. ft. @ $90) 

Work area portion 

(900 sq. ft. @ $60/ft.) 

$324K 

54K 

MICROWAVE ABSORBER MATEIRAL . . . . . . . . . . . . . . . . . . . .$156K 

Basic absorber, including installation, -50 dB quiet zone at 

2.45 GHz $150K 

Shipping from Emerson Curmning 

to MSFC 6K 

ANTENNA HANDLING MECHANISM . . . . . c . . . . . . . . . ..- . . . .$92K 

Concrete pad exterior to bldg. 

Steel tracks (240 ft.) 

Drive chassis 

Servo motors, controlls, 

encoders, drive chain 

Labor: 

$=K 

2K 

8K 

16K 

Engineer (2 mm @ 5K) 10K 

70 
Draftsman (3 mm @ 3K) 

Machinist (9 mm @ 4K) 

9K 

36K 

LINEAR X-Y SCANNER MECHANISM . . . . . . . . . . . . . . . . . . . .$260K 

(mechanical accuracy 2 0.025 inches in transverse and 

longitudinal planes; scan region 45 ft. x 45 ft.) 

Beam steel members 

Support frame 

Drive rollers 

Servo motors & gear drive 

Controller, encoders, A/D conv., 

readout devices 

Hardware & misc. 

Rails and bearings 

Labor: 

$lOK 

13K 

5K 

24K 

35K 

6K 

9K 

Engineer (12 mm @ 5K) 60K 

Draftsman (6 mm @ 3K) 18K 

Machinist (20 mm @ 4K) 80K 

TOTAL $1,140.2K 

71 
Appendix D. Subarray Weight Estimate 

72 
Appendix D. Subarray Weight Estimate 

SPS subarray weight was initially estimated based on standard WR 340 

waveguide. Based on published wall thickness data, the data shown in Figure 

D-l indicates 0.9795 pounds per linear foot of waveguide. 

In Table D-l, an estimate of total weight is arrived at assuming the 

lo-meter square subarray is fabricated from approximately 110 lengths of 

the WR 340 waveguide. Added to the basic waveguide weight was an additional 

40% to allow for structural support structure. The total weight estimate 

for the aluminum version was 2.5 tons. 

From the data of Table D-l, it is noted that the projected weight of a 

mechanical module is 22.5 tons. 

73 
WR 340 (RG 112/u) 

2.2 - 3.3 GHz 

Material 

Density Waveguide 

lbs/in3 in3 per ft 

Waveguide 

lbs per ft 

kver 0.3180 10.915 3.1818 

Aluminum 0.0979 10.915 0.9795 

Figure D-l. Waveguide Weight Estimate 
Table D-l. Estimates of Minimum Subarray Weight 

Total 

Subarray Subarray No. of Length Total Aluminum 

Size Size WR340 of WR340 Waveguide Wt. Waveguide Wt. 

(Ml Ut) Waveguides" (ft) (tons) 

1 ~ 3.281 11.059 36.273 0.02 0.025 0.058 0.08 

3 9.843 33.177 326.546 0.16 0.225 0.520 0.73 

7 22.966 77.413 1,777.859 0.87 1.225 2.828 3.98 

10 32.808 110.590 3,628.284 1.78 2.5 5.772 8.0 

30 98.425 331.770 32.654.560 15.99 22.5 51.95 73.09 

70 229.659 774.131 177,785.936 87.07 122.5 282.84 397.92 

100 328.084 1,105.901 362,828.441 177.69 250 577.22 812.08 

* Outer width = 3.56 inches = 0.2967 ft. 
Appendix E. Vertical Field Intensity at Receive Site for Mountain' 

Top to Mountain Top Range 

A 7-mile mountain top to mountain top elevated range was considered 

tihere the transmit antenna was 600-feet above local terrain. For these 

calculations, a parameter "B" is defined as the total reflected ray attenuation relative to the 0 dB peak value. Note that "B" includes ground reflectivity and the antenna pattern characteristics of the transmit antenna. 

In the data of Table E-l, it is seen when "B" is -40 dB or lower, the 

total field nonuniformity at the receive site is a maximum of 0.17 dB over 

a 12-foot region. Since SPS subarrays have beamwidths in the order of 

O-624-degrees, the realizable value of B for this facility should be significantly lower than -40 dB, thereby providing uniformity for high accuracy 

measurements. 

76 
hr (ft) B = -10 dB 

570. -14.70927072326 

571. -7.428454029902 

572. -3.886621613291 

573. -1.805078190023 

574. -.598472884387 

575. -.0463295456109- 

576. -.06787037464989 

577. -.6660424599133 

570. -1.929334068248 

579. -4.094306065148 

580. -7.797774650291 

581. -15.66507314677 

582. -21.05159924348 

503. -9.467061513061 

584. -5.OOOOS~152862 

sm. -2.470901630549 

586. -.9705253960216 

587. -.1056029676181 

sm. .006305033970435- 

589. -.3683104204136 

590. -1.362345021063 

591. -3.14251959835 

592. -6.13605692236 

593. -11.74197564648 

594. -42.44002615244 

595. -12.24702938135 

596. -6.371557707551 

597. -3.27996250932 

598. -1.443688774927 

599. -.4091105994103 

600. 0. 

601. -.1582457558496 

602. -,9056298923289 

603. -2.357381236972 

604. -4.609725471297 

605. -9.107204773002 

606. -19.68648780457 

607. -16.49257287315 

608. -8.099231111111 

609. -4.262069125127 

610. -2.029822964387 

611. -.7214522467641 

612. -.08702326851387 

613. -.03180696981288 - 

614. -.5402372096123 

615. -1.711244779824 

616. -3.72943646849 

617. -7.151395310516 

618. -14.02772874841 

619. -25.36416173641 

620. -10.36295315128 

621. -5.461899665911 

622. -2.745533166243 

623. -1.129425024176 

624. -.2565315240383 

625. .01329597493542 - 

626. -.2024022492655 

627. -1.164893399363 

628. .-2.840566688716 

629. -5.622461591295 

630. -10.68303592552 

B = -20 dB 

-1.666868821660 

-1.368290177242 

-.9425111367539 

-.516799335368 

-.1884638427282 

-.0152292l3026685 

-.02227300612122 

-.208636306105 

-.5469413182558 

-.9766090964453 

-1.397322200353 

-1.680938745975 

-1.721015307004 

-1.503334403829 

-1.110199655086 

-.6708702128167 

-.2960354048595 

-.06035686587956 

.002081005275045 

-.lleo84803179 

-.4039861932889 

-.8086599019672 

-1.246980437843 

-1.597715602748 

-1.738443538836 

-1.612957533444 

-1.271582247166 

-.8348154599628 

-.4253592138931 

-.130749903230 

0. 

-.05156965839547 

-.2704044823005 

-.6458734905413 

-1.084069243803 

-1.483598303822 

-1.715645129264 

-1.690881524248 

-1.419305523504 

-1.003171504a14 

-.5708432558125 

-.2250147070304 

-.02851615954245 

-.01046720400065 

-.173323276686 

-.4936016929056 

-.9157859356021 

-1.344972240863 

-1.65480329816 

-1.7323526OOESE 

-1.546226305935 

-1.169623669887 

-.7292656680622 

-.3411371507083 

-.08296471919539 

.004390764197041 

-.09114028648367 

-.3563279289048 

-.7488026765344 

-1.109021611862 

-1.559614670522 

B = -30 dB 

-.52@2305072888 

-.4436186672515 

-.3156147356191 

-.1786904359001 

-.06677790243671 

-.005465760070493 

-.007989586633897 

-.07381499309545 

-.1886861453726 

-.3261907710001 

-.4520295012469 

y532115391535Fi 

-.5433503286712 

-.4824043308431 

-.3670766602808 

-,2292980719927 

-*1043335355511 

-.02158989896674 

.0007478234404346 

-.04205945623693 

-.1408663600673 

-.2735424207034 

-.4080402014416 

-.5090036478917 

-.5470986910129 

-.5132604059234 

-.4153124096503 

-.2818336484650 

-.1480825124597 

-.0465260637559 

0. 

-.01845865953342 

-.0979095709539a 

-.2211692205834 

-.3591479261583 

-.4767895350134 

-.5416593645221 

-.5348552276751 

-.4S83947651092 

-.3343898919862 

-.1965795957723 

-.07951209276764 

-.01022436526313 

-.00375790073452 

-.06148210038038 

-.1709660083432 

-.3072853880637 

-.4368343000152 

-.!524091802356 

-.5462340095484 

-.4945439633286 

-.384984210506 

-.248165277598 

-.1195101636044 

-.02962726531581 

.001578119807 

-.03252997870351 

-.124690718004 

-.2544392764355 

-.390792014938 

-.4903156694942 

B 

-.1672269792257 

= -40 dB 

-.1413706427213 

-.1015859624166 

-.osai2899715107 

-.02191217595339 

-.0010020202!52939 

-.002633593655474 

-.02420812243616 

-.06133312750092 

-.1049037563173 

-.1439565638627 

-.1684057643337 

-.1718106340018 

-.1532664917155 

-.11767792981 

-.07429903325471 

-.03413623244012 

-.007109174501039 

.000246670000223 

-.01302756711092 

-.04595906037366 

-.08833253409757 

-.1303935890961 

-.1613821796346 

-.17318731945 

-.1626777499111 

-.1326423470825 

-.09095136001829 

-.04828641612536 

-.01529100536266 

0. 

-.006079581690486 

-.03207632616855 

-.07171103252338 

-.1152071779143 

-.lS1!5409500674 

-.1712985613529 

-.I692366674524 

-.1459112670750 

-.1074720773613 

-.06365983017478 

-.02606530374806 

-.003369650670281 

-.001239141269707 

-.02018272141609 

-.OSS649493999 

-,0989690692!5905 

-.1392022528099 

-11662133335997 

-.1726835992307 

-.1569746862049 

-.1232460610267 

-.08029576532164 

-.03905589269172 

-.00974960626312 

.OOOS2OS771172143 

-.01070250600730 

-,04073256365129 

-.00228568405293 

-.1250498373217 

-.1581253332211 

Table E-l. Relative Field Intensity (in dB) for 4-mile Mountain Top to Mountain Top 
NASA CR-3372 I 

4. TITLE AND SUBTITLE 5. REPORT DATE 

January 198 1 

High Accuracy Radiation Efficiency Measurement Techniques 6. PERFORMING ORGANIZATION CODE 

7. AUTHOR(S) 6. PERFORMING ORGANIZATION REPDR r ? 

D. J. Kozakoff and J. M. Schuchardt Proiect A-2471 

1. REPORT NO. 12. GOVERNMENT ACCESSION NO. 13. RECIPIENT’S CATALOG NO. - 

3. PERFORMING ORGANIZATION NAME AND ADDRESS 

Engineering Experiment Station 

Georgia Institute of Technology 

Atlanta, Georgia 30332 

12. SPONSORING AGENCY NAME AND ADDRESS 

10. WORK UNIT. ND. 

M-319 

11. CONTRACT OR GRANT NO. 

NAS8-33605 

13. TYPE OF REPORT & PERIOD COVERE 

Contractor Report 1 

National Aeronautics and Space Administration 

Washington, DC 20546 1.1. SPONSORING AGENCY CODE 

IS. SUPPLEMENTARY NOTES 

Marshall Technical Monitor: R. A. Inmann 

Final Report 

1 Id. ABSTRACT 

The relatively large antenna subarrays (tens of meters) to be used in the Solar Power 

Satellite (SPS) , and the desire to accurately quantify antenna performance, dictate the 

requirement for specialized measurement techniques. An investigation conducted at the 

Georgia Institute of Technology and reported herein has quantified the error contributors 

associated with both far-field and near-field antenna measurement concepts. As a result, 

instrumentation configurations with measurement accuracy potential were identified. In 

every case, advances in the state-of-the-art of associated electronics were found to be 

required. Relative cost trade-offs between a candidate far-field elevated antenna range and 

near-field facility were also performed. 

1 7. KEY WORDS 18. DISTRIBUTION STATEMENT 

Solar Power Satellite Unclassified - Unlimited 

Antenna Measurements 

Radiation Efficiency 

Subject Category 44 

9. SECURITY CLASSIF. (Of thh r*pmt) 20. SECURITY CLASSIF. (of thh PQe) 21. NO. OF PAGES 22. PRICE 

Unclassified Unclassified 82 A05 

For sale by National Technical Information Service. Springfield. Virgfia 22 16 1 

NASA-Langley, 1981