Frequently asked questions
MmWave Test chambers and positioners
Positioner selection - what payload can the positioners/gimbals handle?
We have a full overview on the positioner pages here, but in summary:
- The DUO5 with standard arms is rated at 14 kg, even higher with short arms.
- The DUO4 with standard arms is rated at 4 kg, even higher with short arms.
What is the far-field distance of your systems?
We have mapped the various combinations of chambers and positioners to cover this. An overview is given in the images below, or you can download the complete overview here.
HOWEVER: Far-field distance is only a part of the picture when choosing the anechoic chamber size. An anechoic chamber with the wrong depth-to-width ratio can make your measurements worse than expected due to wavelength vs. absorber size vs. incident angles. They all play a dominant role when selecting the appropriate chamber size.
If you are unfamiliar with this, contact us to discuss your specific application. We have spent time investigating these phenomenons and can guide you to the right solution.
Do you use metal in your chambers?
No, we don’t. All threaded inserts are on the the outside of the absorbers. It is safe from a measurement perspective since they will not cause stray reflections to disturb measurements. The reason is that the absorbers are shielding twice: If you have a signal strong enough to penetrate a ~50dB attenuating mmWave absorber, the reflected signal would then need to re-enter through the same ~50dB absorber to disturb the measurement, but the signal attenuation would now be ~100dB.
What should we expect from your positioner control system? Can we use our own system instead?
We deliver reference code written in Python and MatLab. Both versions are similar in structure and take care of driving the measurement loops. The code is easy to modify since much of the complexity is in the underlying intelligent motor controller. The controller provides signals for AZ, EL, ROLL and will handle acceleration, resolution, homing sequence, and so forth. Furthermore, the controller works in absolute coordinates, so an “AZ5.5 EL4.5 ROLL90” instruction will take you to that location, no matter the positioner’s current position. The controller keeps track of it all, so you don’t have to count pulses in software. It’s all embedded in the controller.
It gets better: The motor system has the electronics built onto the stepper motor, so the motor itself only needs 24V, a direction signal (DIR), and step pulses (STEP). You can use any inexpensive GPIO module from your PLC provider of choice, whether it is National Instruments, Allen-Bradley, or Beckoff. Finally, all three motors have a closed-loop feedback encoder system built-in in the motor. It runs autonomously, so you don’t need to deal with pulse-counting or closed-loop control in your PLC.
Your blue-painted absorbers, are they any good?
We have selected the very best in the market, and they are more effective and rated to higher frequencies than any other.
The absorber specs are met at the Factory Acceptance Test in the blue-painted appearance. You will find our absorber specifications here.
You highlight that you CNC-machine your positioners. Is this important?
Yes, it is key to a structurally strong design.
First of all, we make positioners in large sizes, so it is vital to have a strong design, even under heavy payloads. Our investments in in-house production on our own CNC equipment give us that benefit. Further advantages are that we can design and produce any size positioner or custom chamber, large aluminum structures, large NRL arcs for reflectivity measurements, and so forth.
Second, apart from the strength, you need a precise manufacturing process to deliver high precision. CNC machining is accurate and provides very low and repeatable tolerances in plastic and even lower in aluminum. Combined with high-end rotational platforms, we can deliver high-quality products.
We are not shying away from 3D printing and use it where applicable as a vital tool in our manufacturing toolbox. For example, we use 3D-printed PET and ABS for the AC1120 and AC888 chamber hinges and clamps, cable holders, and general beautification parts for the DUO positioners.
Some suppliers quote stepper resolution, some quote system precision. Why?
Stepper resolution tells you how fine resolution you can rotate the stepper but gives you no information of the positioner’s precision.
There could be many reasons that suppliers do it this way: Either they work in an application field where it’s not important because customers don’t care about it. Or, maybe they haven’t spent time mapping out the precision. Or, perhaps they did spend time mapping out the precision but didn’t like what they realized.
You can always ask the supplier about repeatable precision if you don’t find it on their website.
What about cabling when using the DUO positioners?
We have large ( > 1”) through-holes in the elevation axis for cabling, and the DUO5 axle is scaled to host a waveguide rotary joint if required. The azimuth platform is similarly well-proportioned for cabling.
If you need a slipring because your application requires continuous rotations, the DUO5 comes standard with a 12-channel slipring, where you will have 6 channels available. You can use this for power and signaling with your DUT or use them for a 3rd axis ROLL system mounted on the DUT plate.
Email us if you need more information on slip rings or the ROLL system for the DUO5.
Frequently asked questions
SAF Spectrum Analyzers
Spectrum Analyzer measurement functions - what can I do ?
The Spectrum Compact delivers a wide range of functionality:
- SWEEP CONTINUOUS – sets the Spectrum Analyzer in continuous measurement of a frequency spectrum
- FREQ – set start, stop and center frequencies
- SPAN – start center frequency, and bandwidth
- FULL SPAN – sets span to the maximum (17GHz)
- MARKER – measuring out power levels at a marked location either manually, or PEAK – automatically searching for the highest output level across the desired band
- POWER IN BAND – in-band measurement, input power in the specified bandwidth
- TRACE MODE – NORMAL (real-time), MAXHOLD stores the max value of all traces as a reference point
- CUMULATIVE show how energy distributes within the spectrum
- AVERAGE 2/4/8/16 show the average value over the last 2-16 sweeps, LEVEL sets min/max level value and allows compensation for an attenuator
NOTE: for a comprehensive overview of Compact Spectrum, check the video review further down on this page.
If you need more information or a product sheet, please contact us.
They are portable and battery driven - Are they for outdoor use ?
Yes! They were designed for field network installers in the first place, so absolutely optimized for outdoor use: The Spectrum Compact series is weatherproof ( IP54 ), they use a resistive touch screen so they can be operated with gloves on, they run for 3-4 hours on battery and records data in internal memory to eliminate the need for a connected PC.
Accessories - what's in the package
The V-band and E-band Spectrum Analyzers are delivered with V-band or E-band antenna; Universal power supply 5.9 VDC; Micro USB to 3.5mm cable for audio; Micro USB cable for data; Water and shockproof case; Lanyard and PC software.
The Spectrum Compact 24-40 GHz ships with RF 2.92mm cable, AC/DC USB-C charger, Leather bag, USB-C – USB-C Cable, USB-A – USB-C adapter, Lanyard, Waveguide adapters 24-33 GHz and 26-40 GHz, and PC software.
Video reviews of the Spectrum Compact mmWave series?
We came across this video review quite recently: Shahriar from “The Signal Path” is an expert within his field and knows what he is looking for, and he is smitten with the performance and quality delivered by the Spectrum Compact Series from SAF Tehnika.
The overview of the instruments start at 03 min 15 sec:
SAF mm-Wave Spectrum Compact 56 – 67GHz Portable Analyzer Review, Teardown & Experiments
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Download user interface demo from Apple's AppStore
Did you there is a Spectrum Compact app for Apple iPhone to give you a feel for the touch-based User Interface? Try out the functionality with this new emulator, download it directly from the Apple App Store: http://bit.ly/_SAFAppStore