BICON / HYBRID COMPARISON

Performed by members of the TCB Council

ANSI C63

SC 1

April 18, 2012

Description of the Study• The purpose of the study is to have members of the TCBC provide more data to further the

discussions in SC1 regarding the suitability of hybrid (aka bilog or biconolog) antennas for final compliance measurements.

• The participants in the study agreed to the following:

• Perform the measurements as outlined by Zhong in his email to C63 of Oct 10, 2011 • 1. 6 dB attenuators will be used on both bicon and hybrid antennas• 2. Every effort will be made to minimize variables. For any configuration (3 or 10m,

horizontal or vertical) we only want to know the delta in field strength using a bicon vs. a hybrid antenna. The same test site, attenuator, cable, preamp, connectors, test operator, etc. should be used.

• 3. Only antennas calibrated to ANSI C63.5:2006 will be used. Those antenna factors are applied to each measurement for the antenna that is being used to determine field strength.

• 4. Include a brief description the test site e.g. OATS vs Chamber, dimensions of the ground screen or of the chamber (LxWxH), and confirmation that it meets site attenuation requirements.

• Note that no LPA measurements were discussed. No concerns were expressed about using hybrids above 200 MHz.

Zhong Chen - Procedure• We have heard a lot of discussions on whether to allow/disallow hybrid antennas for emissions measurements.

Data from different people seems to show conflicting results, and we seem to be at an impasse. I would like to propose a method to “quantify” how much a hybrid antenna does/or doesn’t affect the measurement. I know that is what everyone was trying to do with a reference source (Comb generator or a broadband noise source). But there are a lot of questions with regard to noise floor, and pre-selection etc. I want to propose an alternative method. This requires a couple of NSA-like measurements.

• 1. First, measure inside the chamber for product testing with a pair of bicons. Set up is h1=1m, h2=1-4m scan, horizontal polarization (d=3 or 10 m depending on your intended use). The result is the s21 of the two bicons. I will call it S21bb.

• 2. Keep the transmit bicon antenna intact, and replace the receive antenna with the hybrid antenna you intend to use for the product testing. Repeat the NSA test. The result is between a bicon and a hybrid, referred as S21bh.

• 3. Compare results from 2 and 1. From step 1, Ebb=S21bb+FSAF_bicon. And From step 2, Ebh=S21bh+FSAF_hybrid.

• Delta E = Ebh – Ebb (all in dB).

• 4. Repeat the test for a vertical polarization, e.g. with h1=1 m in vertical pol.

• The results are the differences a bicon or a hybrid will measure from the same emission source (a bicon in this case). You can use pads on the antennas, but the same must be done in the product testing.

Laboratory Information• Lab 1 – 10 meter Chamber• Lab 2 – 10 meter Chamber• Lab 3 – 10 meter Chamber• Lab 4 – 10 meter Chamber• Lab 5 – 5 meter Chamber (3 meter test distance)• Lab 6 – 3 meter Chamber• Lab 7 – 3 meter Chamber• Lab 8 – 5 meter Chamber (3 meter test distance)• Lab 8 – 10 meter Chamber

3-meter Horizontal

10 100 1000-5.00

-4.00

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

Lab Comparison - 3m Horizontal

Lab 1 Lab 5 Lab 6 Lab 7 Lab 8

Frequency (MHz)

Del

ta (

dB

)

3-meter Vertical

10 100 1000-5.00

-4.00

-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

Lab Comparison - 3m Vertical

Lab 1 Lab 5 Lab 6 Lab 7 Lab 8

Frequency (MHz)

Del

ta (

dB

)

10-meter Horizontal

10 100 1000-6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

Lab Comparison - 10m Horizontal

Lab 2 Lab 3 Lab 4 Lab 8

Frequency (MHz)

Del

ta (

dB

)

10-meter Vertical

10 100 1000-6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

Lab Comparison - 10m Vertical

Lab 2 Lab 3 Lab 4 Lab 8

Frequency (MHz)

Del

ta (

dB

)

Hybrid Antenna SWR – No Input Attenuation

10.0000 100.0000 1000.0000

1.00

5.00

9.00

13.00

17.00

21.00

25.00

29.00

33.00

Freq (MHz)

SW

R=

1:

Hybrid Antenna SWR – Attenuation Comparison

10.0000 100.0000 1000.0000

1.00

1.50

2.00

2.50

3.00

3 dB6 dB10 dB

Freq (MHz)

SW

R=

1: