2019_RAM_Requirements.pdf

STATEMENT OF REQUIREMENTS (SOR)

FOR

MEDIUM POWER RADAR ABSORBING MATERIAL

(RAM) REPLACEMENT AND TESTING

AT

EDWARDS AFB, CA

MAY 21, 2019

Background

The 772d Test Squadron (TS), Edwards AFB, CA has a requirement to provide electromagnetic energy absorption in the MP handling range for use in the Benfield Anechoic Facility (BAF).

This capability requires increased power handling performance to accommodate higher power systems, without major degradation of performance across frequency. The overall use of RAM is to eliminate multi-path reflections back to the System Under Test (SUT). The RAM must be of open-cell foam with proportionally consistent pore sizes to help dissipate the heat generated by higher power energy.

Minimum Specifications:

Physical dimensions: 24 inch x 24 inch base with a max tolerance of +0.25 inch/-0.25 inch, with nine (9) 24 inch Pyramids.

Color: Maroon

Carbon Loading and Fire Retardant:

• The RF absorbing material (RAM) manufacturing processing must use a binder for both the loading ingredients and fire retardant ingredients.

• The RAM must not shed carbon particles during normal handling including dropping an upright piece of RAM from a height of three (3) feet onto a concrete surface (with the bottom RAM surface impacting the concrete).

Flammability Testing: The contractor shall test the flammability of the manufactured RAM to meet the fire retardant testing required by NRL Report 8093 (Tests 1, 2, and 3).

Reflectivity Requirement and Testing:

All RAM shall meet at a minimum the normal incidence reflectivity specification listed in Table 1 below.

NORMAL INCIDENCE REFLECTIVITY

Frequency 24-inch Medium Power

500 MHz to < 1 GHz -34 dB

1 GHz to < 3 GHz -40 dB

3 GHz to < 6 GHz -45 dB

6 GHz to 18 GHz -50 dB

Table 1

The contractor shall conduct measurements of RAM reflectivity across frequency with a one (1) MHz step size for 10% of RAM in each lot.

Randomization/Repeatability: Lot one (1) of RAM reflectivity testing is to be additionally tested for randomization and repeatability. All measurements shall meet the normal incidence reflectivity specification listed in Table 1.

As an example: Record the placement of RAM pieces location. Make the first reflectivity measurement. Next, the placement of the RAM pieces will be randomly shifted on the reflectivity table and the reflectivity data will be recollected for the second time. Record the RAM placement in the randomized location. Finally, the same pieces will be put back on the reflectivity table in their original recorded locations and a third reflectivity measurement will be taken.

Power Handling Requirements and Testing:

All RAM shall meet the power handling minimum requirement of two (2) watts per square inch for a minimum duration of one (1) hour. The contractor shall conduct measurements of RF power handling for the seven listed frequencies with a sample size of one (1) piece per lot. See Table 2.

Power Handling

Frequency Illumination Power Density

Temperature measured at 3”, 6” and 12” from the pyramid tip of the center pyramid.

500 MHz

2 Watts per square inch

1 GHz

3 GHz

6.5 GHz

9 GHz

12 GHz

18 GHz

Table 2

Power Handling Test Environment:

• Free space with minimal reflections.

• Ambient airflow condition with no forced air at the RAM.

• The illumination wave front where the peak energy shall be pointed at the center pyramid of the two (2) foot by two (2) foot test sample. In order to achieve peak energy illumination of the center pyramid an estimate of the amplitude taper of the test area shall be accomplished.

• The contractor shall determine and specify the maximum temperature threshold of the RAM and deliver the maximum temperature threshold value with the data.

• The data to be recorded is Temperature versus Time at a power of two (2) watts per square inch. The rise time to a steady state temperature, ten (10) minutes at the steady state temperature, and cool down time to ambient shall be recorded. If the RAM cannot achieve a steady state temperature within one hour of illumination at two (2) watts per square inch and the temperature has not exceeded the maximum temperature threshold of the RAM as determined and specified by the manufacturer, then the cool down to ambient phase can be initiated.

Acceptability Criteria:

Data Deliverables:

• Reflectivity Test data, dB/frequency, Excel file

• Power handling measurements, temperature/time, Excel file

• Specification of maximum operating temperature of manufactured RAM

• Manufacture warehousing specification sheet that shall include the temperature and humidity requirements for storage locations outside of the Anechoic Chamber

The Government shall review all items identified in the acceptability criteria to determine if RAM meets/exceeds all minimum specifications. Once RAM is determined acceptable the Government shall notify the contractor that they may ship the product.

Definitions –

Lot: A lot is defined as a manufacturing run for which there is no break in production, base materials are mixed from the same supplier’s batches, and a mixture operation is not stopped/restarted.