Question
What occurs when the input signal levels to a mixer are too high?
Answer Options
- A) Spurious mixer products are generated
- B) Mixer blanking occurs
- C) Automatic limiting occurs
- D) Excessive AGC voltage levels are generated
Correct Answer: A
Explanation
A mixer is a deliberately non-linear circuit, as that non-linearity is required to perform the multiplication of the two input frequencies (F_S and F_{LO}). However, if the input signals are too strong, the non-linearity becomes excessive, driving the mixer well beyond its specified operating range.
When the input signal levels to a mixer are too high, spurious mixer products are generated. These unwanted signals are high-order intermodulation products (IMD) that can fall on top of the desired Intermediate Frequency (\text{IF}) signal, interfering with the desired communication. This problem is mitigated by using a mixer with a high Third-Order Intercept Point (\text{IP3}) and by ensuring that the input signals are adequately attenuated.
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