Most Avtech high-speed pulse generators are optimized to operate near their maximum rated amplitude. Generally, operation below 20% of the maximum rated amplitude is not recommended.
To generate pulses below this level, the pulse generator should be operated near its maximum rated amplitude, and one or more coaxial attenuators should be connected to the output.
For input amplitudes of up to 50V, Avtech suggests the Mini-Circuits BW-SxxW2+ family of low-cost fixed 18 GHz, 2 Watt attenuators. For higher amplitudes, consider the BW-SxxW20+ family of fixed 18 GHz, 20 Watt attenuators. However, even with the higher average power rating, these attenuators may fail if the high-voltage input pulse width exceeds 200 ns, approximately.
It is also possible to purchase variable attenuators, but these are very expensive. They may cost more than the pulse generator itself! For instance, the Midwest Microwave STA-1044-12-SMA-79 rotary-switch attenuator is variable from 0 to 69 dB, in 1 dB steps, with 12.4 GHz bandwidth. It costs approximately $3000. (Please note that the average power rating is 2 Watts. The peak power rating, and hence maximum input amplitude, is not specified.) For lower-speed applications, Pasternack offers the PE7008-1 pushbutton attenuator, which is variable from 0 to 65 dB in 1 dB steps, with 750 MHz bandwidth. The average power rating is 1 Watt, and the peak power rating is 1000 Watts. This attenuators costs approximately $300.
For best results, the attenuators should be connected closest to the load, rather than the pulse generator. This will reduce the length of cabling cabling the low-amplitude signals, and thus reduce interference from other sources.