USING THE THIRD ORDER INTERCEPT POINT TO CALCULATE IMD PRODUCT FOR THE AD9622 OP AMP OUTPUT +20 POWER RD ORDER IMD e.Odam NPUT POWER (PER TONE), dB Figure 8.7 HIGH FREQUENCY TWO-TONE GENERATION Generating test signals with the spectral purity required to make low distortion high frequency measurements is a challenging task. a test setup for generating a single tone is shown in Figure8.8. The sinewave oscillator should have low phase noise output. The distortion should be GdB lower than the desired accuracy ottho cillata (e. g, Marconi 2382), especially if the device under test is an ADC, where phase nois increases the ADC noise floor. The output of the oscillator is passed through a bandpass(or lowpass) filter which removes any harmonics present in the os measurement. The 6dB attenuator isolates the dut from the output of the filter. The impedance at each interface should be maintained at 50ohms for best performance(75ohm components can be used, but 50ohm attenuators and filters are generally more readily available). The termination resistor, RT, is selected so that the parallel combination of rr and the input impedance of the dut is 50ohms LOW DISTORTION SINGLE-TONE GENERATOR NALYZER INPUT OSCILLATO ATTEN Figure 8.89 USING THE THIRD ORDER INTERCEPT POINT TO CALCULATE IMD PRODUCT FOR THE AD9622 OP AMP Figure 8.7 HIGH FREQUENCY TWO-TONE GENERATION Generating test signals with the spectral purity required to make low distortion high frequency measurements is a challenging task. A test setup for generating a single tone is shown in Figure 8.8. The sinewave oscillator should have low phase noise (e.g., Marconi 2382), especially if the device under test is an ADC, where phase noise increases the ADC noise floor. The output of the oscillator is passed through a bandpass (or lowpass) filter which removes any harmonics present in the oscillator output. The distortion should be 6dB lower than the desired accuracy of the measurement. The 6dB attenuator isolates the DUT from the output of the filter. The impedance at each interface should be maintained at 50ohms for best performance (75ohm components can be used, but 50ohm attenuators and filters are generally more readily available). The termination resistor, RT, is selected so that the parallel combination of RT and the input impedance of the DUT is 50ohms. LOW DISTORTION SINGLE-TONE GENERATOR Figure 8.8