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• Bandpass, Highpass, Lowpass, • VSWR: 1.5:1 Typ
and Band Reject application • Bandwidth of 3% to 100%
• Frequency Range: 40 MHz to 19.0 GHz • Mil-Std-202 Cond.
• Selectivity > 60 dB, other options available • Low Insertion Loss
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ISO 9001:2008 re;ectometer: The ;rst used a hand-held device to measure the re;ection coef;cient of absorber materials
for EMI mitigation. In the second,
an integrated re;ectometer system
was mounted on an industrial robot
to scan ;berglass composites. With
appropriate data processing, a microwave re;ectometer can detect
defects and determine the thickness
of non-conductive materials. Both of
the examples demonstrate that RF
cable-less re;ectometer technology
is feasible, enabling in situ measurements in ;eld and factory.■
This work was supported in part
by a Cooperative Research and
Development Agreement (CRADA)
between the Air Force Research
Laboratory (AFRL/RX) and Compass
1. J. W. Schultz, “Focused Beam Methods,”
Measuring Microwave Materials in Free Space, ISBN
2. J. W. Schultz, R. Schultz, J. Maloney and K.
Maloney, “Correction of Transmission Line Induced Phase and Amplitude Errors in Re;ectivity Measurements,” U.S. Provisional Patent
20160103197, Issued February 16, 2017.
3. S. A. Zaostrovnykh, V. I. Ryzhov, A. V. Bakurov, I.
A. Ivashchenko and A. I. Goloschokin, “
Measurement Module of Virtual Vector Network Analyzer,”
U.S. Patent 9291657B2, Issued March 22, 2016.
4. J. Musil, F. Zacek, A. Burger and J. Karlovsky,
“New Microwave System to Determine the
Complex Permittivity of Small Dielectric and
Semiconducting Samples,” 4th European Microwave Conference, September 1974, pp. 66-70.
5. R. Diaz, J. Peebles, R. Lebaron, Z. Zhang and
L. Lozano-Plata, “Compact Broadband Admittance Tunnel Incorporating Gaussian Beam Antennas,” U.S. Patent 7889148, Issued February
6. J. W. Schultz, J. Maloney, K. Cummings-Ma-loney, R. Schultz, J. Calzada and B. Foos, “A
Comparison of Material Measurement Accuracy of RF Spot Probes to a Lens-Based Focused Beam System,” Proceedings of the 2014
AM TA, October 2014.
RF cables add errors due to thermal drift and ;exing. Eliminating the
RF cable, measurement reliability
and accuracy are signi;cantly improved. As RF cables wear out and
must be replaced periodically, especially if they are regularly moved or
;exed, eliminating the RF cable can
decrease measurement cost and reduce the need for maintenance.
This article discussed two appli-
cations using a compact microwave
microwave re;ectometer. Detection
of this 3 mil thick layer is somewhat
remarkable, considering the wave-
length of the interrogating microwave
energy: from 6 inches at 2 GHz to
0.66 inches at 18 GHz. This method
can be used to detect small thickness
changes in ;berglass composites and
other dielectric materials. Furthermore, since it is easily portable, testing can be done in any environment,
such as the factory or in the ;eld.
Fig. 8 Computed thickness of a
;berglass panel, showing detection of
4 2 0
Position From Bottom (in)
Fiberglass with Painters Tape in Back