Pierre Prat (remote), Yuhang and Michael

We received the Minicircuits M3SWA-2-50DRB+ absorptive RF switch evaluation board. Nominally, it has a fall time of 4.6 ns, well within bounds of what we want (400 ns). In this case, the rise and fall times have been specified by the manufacturer as the time it takes to go from 10% to 90% of the peak voltage and vice versa. The circuit can accept high input power > 24 dBm at 100 MHz. It is powered by -5/+5 V supply. The switch is activated/deactiveated by a TTL (transistor-transistor logic) control signal. In short, voltages in a certain low threshold (0-0.8 V) are considered "OFF" and in a certain high threshold (2.1-5 V) are considered "ON". In this case, we can just use a square wave oscillating between 0 and 5 V, and then trigger the oscilloscope to follow the rise/fall of the RF signal.

Chip manual: https://www.minicircuits.com/pdfs/M3SWA-2-50DRB+.pdf
Evaluation board diagram: https://www.minicircuits.com/pcb/WTB-M3SWA250DRB+_P02.pdf
 

-- Test --

The RF switch was tested in the filter cavity clean room using the already present oscilloscope, function generator and RF amplifier(s). We brought a DC power supply to send -5V/+5V to power the RF switch, as well as a Tektronix AFG320 function generator to provide the control signal to the RF switch (0 to 5V square wave, checked at 1 Hz and 12 kHz). Both of these were tested first to make sure they give the required voltage and square wave signal.

A 500 MHz RF signal was sent from the filter cavity function generator to the switch -> RF amplifier -> oscilloscope. A 20 dB attenuator with 50 Ohm impedance was connected to the oscilloscope to prevent back reflection. Unfortunately, the first RF amplifier (Minicircuits ZHL2) we were using stopped outputting. We did take care to say the order in which you should make connections with the RF amplifier. I hope it is not permanently broken... 

-- Data --

The figure shows the fall time when a 1 Hz square wave is sent to the TTL port of the switch (rise time figure pending). The data is a bit low resolution. The lower half of the figure shows a zoom in of the timescale and indicates 10% of Vpk. This measurement doesn't seem very accurate, but regardless, the fall time is well below the target of 400 ns.

With these results, we moved the RF switch and the necessary electronics to the ATC cleanroom.