Figure 2-5 OIP3 Test Setup

Use the following guidelines for two-tone OIP3 measurement:

1. Figure 2-5 shows the combination of two signal generator outputs using an in-phase power splitter and combiner. Use a 3dB to 6dB attenuator at the signal-generator outputs to prevent the generators from communicating, resulting in signal-generator IMD3 spurs.
2. Set both the signal generator outputs to a power level and frequency spacing so that the signal generator yields the desired output power, ${\mathrm{P}}_{\mathrm{O}\mathrm{U}\mathrm{T}}$, at the device.
3. Keep the output power level within the TRF1213 linear operating range. For example, if the total desired output power at the device is 8dBm, set the signal generators so that each of the fundamental output powers results in 2dBm per tone. As a general rule, keep the total output power level approximately 6dB to 8dB less than the 1dB compression point. See the device data sheet for the supported output power levels.
4. For the OIP3 test, the two tones can be spaced by the specified frequency.
5. Set the spectrum analyzer attenuation setting appropriately so that the spectrum analyzer nonlinearity does not affect the measurements.
6. Keep spectrum analyzer RBW and VBW settings identical for main tone and IM3 products.

For output IP3 calculation, take into account the combined losses at the desired frequency band between the TRF1213EVM output to the spectrum analyzer input. The combined power loss is due to the PCB output trace, RF coax cable, 180° passive balun, and any attenuator pad used for external matching. Equation 2 gives the calculated OIP3. The loss at the output of the device, ${\mathrm{P}}_{\mathrm{L}\mathrm{O}\mathrm{S}\mathrm{S}}$ , is found using the combination of the Figure 2-3 and any attenuation added after the EVM.

where

• ${\mathrm{P}}_{\mathrm{I}\mathrm{N}\_\mathrm{S}\mathrm{A}}$ = Input power per tone into the spectrum analyzer
• ${\mathrm{P}}_{\mathrm{L}\mathrm{O}\mathrm{S}\mathrm{S}}$ = Power loss from the device output to the spectrum analyzer input
• $\mathrm{I}\mathrm{M}\mathrm{D}3$ = Higher power of the two intermodulation distortion products recorded at either 2f1 – f2 or 2f2 – f1
• ${\mathrm{P}}_{\mathrm{I}\mathrm{N}\_\mathrm{S}\mathrm{A}}+{\mathrm{P}}_{\mathrm{L}\mathrm{O}\mathrm{S}\mathrm{S}}={\mathrm{P}}_{\mathrm{O}\mathrm{U}\mathrm{T}}$ is the amplifier output power per tone