Cascading Channel 0 and Channel 1

Additional gain (or attenuation) may be achieved by cascading CH 0 and CH 1, but each channel is calibrated individually. Therefore, if you cascade CH 0 and CH 1, the impedance mismatch of the connection between CH 0 and CH 1 results in an additional mismatch error through the combined path. The ni5690 Get Actual Gain VI or the ni5690_getActualGain function does not report this additional mismatch error. This combined loss is frequency dependent. You can measure or approximate the combined loss using the CH 0 and CH 1 Voltage Standing Wave Ratio (VSWR) curves provided in the appropriate specifications document for your device. The maximum mismatch error is given by the following equation:

where   ρ_S is the source reflection coefficient

ρ_L is the load reflection coefficient

For example, if the output VSWR of CH 0 = S22 = 1.5 and the input VSWR of CH 1 = S11 = 1.5, then the maximum mismatch error is given by the following equations:

Caution  Observe maximum input power ratings to avoid damaging the NI RF amplifier or attenuator.

Refer to the appropriate specifications document for your device, printed and included in your kit, for detailed specifications of both channels, including available gain ranges, gain variation by temperature, and power ratings.