SNF Chamber

The operating frequencies are 400MHz to 6GHz

Normal operations use 3 degree steps during the data transform. Other resolutions are possible such as 1 degree and 5 degree steps. Rotational increments as low as 0.5 degrees have been used.

25dBi is the ceiling for gain measurements. A pad can be installed in our system to protect the equipment from saturation.

The gain can be offset to account for amplification or attenuation. We can even use a frequency swept measurement to offset the gain data and derive the antenna gain.

Active devices can be measured in the Spherical Chamber. Your device must use a CW signal at a single frequency. The Spherical Chamber will not sync up to a pulsed signal. We will only be able to measure one frequency point at a time. The Active measurement set-up is complicated, and will be done during your measurement session. Normal set-up time is ½ hour.

Yes, the Spherical Chamber can accommodate a human test subject for accurate measurements of body interaction effects on body worn and handheld devices.

Test times depend on the number of frequency points taken. After the data is taken, a Near Field to Far Field calculation needs to be performed. This chart shows typical measurement times:

Frequency Points

1. 1 Point
2. 13 Points
3. 101 Points

Measurement

1. 0.5 minutes
2. 2.2 minutes
3. 9 minutes

Transform

1. 0.1 minutes
2. 0.3 minutes
3. 1 minute

The Spherical Chamber uses an array of probes to measure the spherical performance of antennas. Once a year, a Probe Calibration is performed by the chamber manufacturer to normalize the amplitude and phase of each probe in the array. Once a month, a gain calibration is performed using a broadband horn and a series of dipoles. A reference circuit in the range provides a gain offset to correct for temperature variations between monthly calibrations. 
The Spherical Chamber can be calibrated using either Gain or Efficiency standards.

From 1-6GHz, we use a broadband horn that was measured for gain at Georgia Tech using NIST traceable standards. From 400-999MHz, we use a series of dipoles that were measured for efficiency using the Wheeler Cap method.

Yes. Special calibrations can be performed. All that is required is a standard measurement in the range. The calibration procedure will be performed as part of your range time. The gain accuracy of any measurements will be referenced to your standard.

The range has a Styrofoam column with a flat foam table in the center of the ring. Antennas are positioned on top of the column. We have a laser sight to help center the antenna in the ring. Foam blocks and pieces are available to help position oddly shaped samples. Other fixtures can be used to mount equipment that will not work with a foam column.

What is the largest sample size allowed? 
We have had an aircraft door as large as 5’ x 6’ in the range.

If the sample can be safely lifted into position by two people, it can be measured in the range. We have numerousfixtures besides the foam column that allow for different sizes and shapes.

Customers can bring their own mounting fixtures. The hole pattern of the base pedestal is available. Mechanical drawings are available to assist customers in mounting and centering their devices. Download the pdf drawing and dxf artwork of the mounting pattern by clicking here.

The cable in the range uses an SMA connector. We have various adapters, but it usually better for each customer bring their own adapters and loads.

A cable runs up the center of the foam column. There is a cutout near the top to allow for a cable loop. The cable running through the column has a lossy coating to minimize reflections. A 12 inch cable at the top has ferrite beads to minimize currents on the outside jacket.

AC power is available inside the range. We have various absorber pieces that can be used to cover ancillary equipment during the test.

All of the data exported is in standard ASCII text format and can be read by Excel, MatLab, and other standard software packages.

It is your time to spend as you want. We cannot process data while a measurement is taking place. But in between measurements, you can look at graphs and data. All it costs is the time taken to process the data.

We collect all of the spherical data using the software that runs the Spherical Chamber. We will export ASCII data files according to your needs. Typical data packages are:

• Full spherical E-Phi and E-Theta values at each frequency. This data can be Linear and/or Circular.
• Maximum Gain. This is the maximum gain measured regardless of peak beam position.
• Efficiency in dB and/or %.
• Axial Ratio

Individual Phi or Theta cuts can be exported, but are extremely time consuming given multiple samples. Most customers process the E-Phi and E-theta data for specific pattern cuts later to save time for sample measurements.

Data can be burned to a CD or DVD. We can copy your data to a memory stick. We also have an FTP site that you can download your data from. You will be emailed a link for the download site. You are the only customer who will be able to access your data from the FTP site.

We will keep your data for at least 1 month unless you tell us to delete it.

We have run sight sensitive samples in the range. We have a camera in the range that can be disabled. Once we have run you through the antenna mounting procedure, you can mount your own samples. We do not need to see your antennas to measure them and process the information.

Whether or not we can measure and process the data from a classified antenna is defined by your particular program, and can only be determined by your Security Officer. The range is in a separate building and can be isolated. The measurement frequency band can be padded with extra frequencies to hide specific points. We have dealt with sight sensitive samples. 
Our system computer has removable drive bays, and can be unplugged from the JEM computer network. If you send us a blank hard drive ahead of your measurement session, we can format the drive and clone the operating system and measurement software required. We will boot up the system with your drive. At the end of the session you can take it with you.

Please visit jemengineering.com/quote and submit the online form. Alternately, you can send an email toinfo@jemengineering.com with the subject “Test Services RFQ”. A JEM representative will respond to you within 2 Business Days.

Once you receive quote for the testing services needed, you can email info@jemengineering.com or call 301-317-1070 x113 to set up a testing date. If you need to change or cancel the test date, JEM requires notice 24 hours in advance of the test date, otherwise a cancellation fee of $1,000 or the testing quote (whichever is less) will be charged.

Please request a quote for our current rates.

Invoicing is conducted once services are rendered. Terms are negotiated prior to the testing date. Credit cards may be charged directly upon completion of services. Invoices are sent via email for customers with Net Terms.