Question
What does a third-order intercept level of 40 dBm mean with respect to receiver performance?
Answer Options
- A) Signals less than 40 dBm will not generate audible third-order intermodulation products
- B) The receiver can tolerate signals up to 40 dB above the noise floor without producing third-order intermodulation products
- C) A pair of 40 dBm input signals will theoretically generate a third-order intermodulation product that has the same output amplitude as either of the input signals
- D) A pair of 1 mW input signals will produce a third-order intermodulation product that is 40 dB stronger than the input signal
Correct Answer: C
Explanation
The Third-Order Intercept Point (IP3 or TOI) is a theoretical, mathematical point used to quantify a device’s linearity and its tolerance to intermodulation distortion (IMD). The IP3 figure is the point at which the power of the third-order IMD products would theoretically equal the power of the original input signals, if the device could operate that high without saturating.
Therefore, a third-order intercept level of 40 dBm means that a pair of 40 dBm input signals will theoretically generate a third-order intermodulation product that has the same output amplitude as either of the input signals. In reality, a device saturates far below this point, but the IP3 serves as a valuable figure of merit: a higher IP3 implies better linearity and dynamic range, thus better resistance to IMD.
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