1. Novel Method to Measure the Gain of UHF Directional Antennas
UNIVERSITY OF TWENTE.
Novel Method to Measure the Gain
of UHF Directional Antennas
using Distance Scan
B. A. Witvliet (Ben)
EuCAP, The Hague,
6-11 April 2014

2. Novel Method to Measure the Gain of UHF Directional Antennas
using Distance Scan
B. A. Witvliet (Ben)
University of Twente (part-time PhD student)
Radiocommunications Agency Netherlands
E. van Maanen
M. J. Bentum, C. H. Slump, R. Schiphorst
University of Twente
UNIVERSITY OF TWENTE. 2

3. Novel Method to Measure the Gain of UHF Directional Antennas
using Distance Scan
B. A. Witvliet (Ben)
Trans World Radio, Monte-Carlo, Monaco
KPN Telecom, The Netherlands
Radio Netherlands, Madagascar
Netherlands Broadcast Transmitter Company (NOZEMA)
Radiocommunications Agency Netherlands
Background in Telecommunications:
UNIVERSITY OF TWENTE. 3

4. Novel Method to Measure the Gain of UHF Directional Antennas
using Distance Scan
Introduction
Distance Scan Concept
Extension with Three Antenna Method
Proof of Performance
External Verification
Conclusions
UNIVERSITY OF TWENTE. 4

5. Propagation Measurements
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
1. Introduction
Propagation Measurements
UHF MHz, 8 frequencies, 500 days
[1]
Wieringen
Baldock
Hoek van
Holland
Lopik
Harwich
Goes
[1] B. A. Witvliet, et al., “Mixed-Path Trans-Horizon UHF Measurements for P.1546 Propagation Model Verification,” IEEE APWC, 2011. 5

6. 1. Introduction Antennas used: 12 elements
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
1. Introduction
Antennas used:
12 elements
Yagi-Uda parasitic end-fire array
3 versions:
MHz L=1.3 m λ
MHz L=1.2 m λ
MHz L=1.0 m λ
Manufacturer specifications:
14.15 dBi antenna gain
35º E-plane beam width (θE)
50º H-plane beam width (θH)
Regardless of frequency?
Regardless of boom length?
“ Reasonable Doubt “
UNIVERSITY OF TWENTE. 6

7.  and $$$  1. Introduction Antenna gain verification needed
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
1. Introduction
Antenna gain verification needed
Quick and dirty
External calibration later
 and $$$
Antenna range options:
Anechoic room
Near-field scanner
Reflection range
OATS (height scan) 
not good for ‘highly directional’ antennas
UNIVERSITY OF TWENTE. 8

8. ⇔ ⇒ 2. Distance Scan Concept In free space: GTX GRX R PTX PRX
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
2. Distance Scan Concept
In free space:
GTX
GRX R
PTX
PRX
Friis transmission formula [3] :
P RX P TX = A e RX A e TX R 2 λ 2
P RX P TX = λ 2 G RX 4π λ 2 G TX 4π R 2 λ 2
and Effective Aperture [4] :
A e = λ 2 G 4π
P RX P TX = λ 2 G RX G TX 16π 2 R 2 ⇔ ⇒
G RX G TX = 16π 2 λ 2 P RX P TX R 2
[3] H. T. Friis, “A Note on a simple Transmission Formula,” Proc.IRE, May 1946
[4] J. D. Kraus, “Electromagnetics,” 4th Ed., p. 727 9

9. 2. Distance Scan Concept In free space: PTX GTX GRX PRX R R
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
2. Distance Scan Concept
In free space:
PTX
GTX
GRX
PRX R R
P RX P TX R 2
UNIVERSITY OF TWENTE. 10

10. 2. Distance Scan Concept Above ground: direct PTX PRX reflected
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
2. Distance Scan Concept
Above ground:
direct
PTX
PRX
reflected
Increasing horizontal distance  Decreasing path length difference between direct and reflected wave
 Alternating in-phase and out-of- phase conditions
UNIVERSITY OF TWENTE. 11

11. 2. Distance Scan Concept Above ground: PTX GTX GRX PRX R R
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
2. Distance Scan Concept
Above ground:
PTX
GTX
GRX
PRX R
(1-r)
(1+r) R
(1)
P RX P TX R 2
Additive interference
Destructive interference
S dir + S ref =(1+r) S dir
S dir − S ref =(1−r) S dir +
S dir
UNIVERSITY OF TWENTE. 14

12. Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
2. Distance Scan Concept
Concept verification using simulations (free space):
Using distance between dipoles.
Corrected for phase center position.
Expected free space gain
NEC 4.1 simulation of a 13.9 dBi Yagi-Uda, length 2.0 λ, on 435 MHz. 15

13. Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
2. Distance Scan Concept
Concept verification using simulations (above ground):
Using distance between dipoles.
Corrected for phase center position.
Expected free space gain
Same simulation, antenna now 10 meters above clay soil (σ = 30 mS/m, εr = 20). NEC 4.1 with Sommerfeld ground model. 16

14. 3. Extension with Three Antenna method
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
3. Extension with Three Antenna method
Distance Scan yields antenna gain product:
G RX G TX = 16π 2 λ 2 P RX P TX R 2
Single antenna gain can be obtained:
Using a reference antenna with known gain
Using the Three Antenna Method
UNIVERSITY OF TWENTE. 19

15. 3. Extension with Three Antenna method
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
3. Extension with Three Antenna method
Three antennas with unknown antenna gain GA, GB and GC.
Let’s define A, B and C as:
A=10 log 10 G A
B=10 log 10 G B
C=10 log 10 G C
We’ll measure all combinations of these antennas:
X=10 log 10 G A G B =A+B
Y=10 log 10 G A G C =A+C
Z=10 log 10 G B G C =B+C
From these we can calculate A, B and C:
A=(X+Y−Z)/2
B=(X−Y+Z)/2
C=(−X+Y+Z)/2
G A = 10 𝐴 10
G B = 10 𝐵 10
G C = 10 𝐶 10
UNIVERSITY OF TWENTE. 20

16. Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Two wideband antennas are used to make pairs with the Yagi’s.
(14 elements Log-Period Dipole Array, MHz,
boom length 75 cm, gain approx. 6.5 dBi)
UNIVERSITY OF TWENTE. 21

17. 4. Proof of Performance Differential GPS
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Differential GPS
Measurement receiver and data logger Tx
Cable loss nulled before measurement run
Distance offset nulled before measurement run
UNIVERSITY OF TWENTE. 22

18. Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Improvised set-up using two monitoring vehicles with pneumatic masts.
UNIVERSITY OF TWENTE. 23

19. Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Example measurement: Yagi-Uda antenna ‘2’ and LPDA ‘A’ on 519 MHz:
UNIVERSITY OF TWENTE. 25

20. 4. Proof of Performance Antenna gain products for Yagi-Uda antenna 1:
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Antenna gain products for Yagi-Uda antenna 1:
UNIVERSITY OF TWENTE. 26

21. 4. Proof of Performance Antenna gain products for Yagi-Uda antenna 2:
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Antenna gain products for Yagi-Uda antenna 2:
UNIVERSITY OF TWENTE. 27

22. 4. Proof of Performance Antenna gain products for Yagi-Uda antenna 3:
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Antenna gain products for Yagi-Uda antenna 3:
UNIVERSITY OF TWENTE. 28

23. Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Antenna gain calculated using the Three Antenna Method:
Nota Bene: this is not dBi !
UNIVERSITY OF TWENTE. 29

24. Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
4. Proof of Performance
Antenna gain calculated using the Three Antenna Method:
UNIVERSITY OF TWENTE. 30

25. 5. External Verification
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
5. External Verification
Calibration performed by National Physical Laboratory, London, UK:
UNIVERSITY OF TWENTE. 31

26. 5. External Verification
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
5. External Verification
Expanded Measurement Uncertainty of NPL calibration: 0.5 dB (2σ)
Expanded Measurement Uncertainty of
Distance Scan measurement: 1.5 dB (2σ)
Comparison of NPL calibration with improvised Distance Scan:
LPDA ‘A’ LPDA ‘B’
Mean error dB dB
Standard deviation 0.4 dB 0.4 dB
UNIVERSITY OF TWENTE. 32

27. 6. Conclusion Cheap & simple antenna calibration method
Novel Method to Measure the Gain of UHF Directional Antennas using Distance Scan
6. Conclusion
Cheap & simple antenna calibration method
Minimal site preparation
Low cost
Fair accuracy
Possible improvements to enhance accuracy:
Higher measurement speed
Laser distance meter
Path guidance
Further automation
UNIVERSITY OF TWENTE. 34

28. Novel Method to Measure the Gain of UHF Directional Antennas
UNIVERSITY OF TWENTE.
Novel Method to Measure the Gain
of UHF Directional Antennas
using Distance Scan
B. A. Witvliet (Ben)
EuCAP, The Hague,
6-11 April 2014