Question
An SDR receiver is overloaded when input signals exceed what level?
Answer Options
- A) One-half of the maximum sample rate
- B) One-half of the maximum sampling buffer size
- C) The maximum count value of the analog-to-digital converter
- D) The reference voltage of the analog-to-digital converter
Correct Answer: D
Explanation
In a Software Defined Radio (SDR), the front end converts the analog RF signal directly into a digital data stream using an Analog-to-Digital Converter (ADC). The ADC has a fixed input voltage range determined by its internal components. If the incoming analog signal voltage exceeds this limit, the ADC cannot accurately digitize the waveform.
An SDR receiver is overloaded when input signals exceed the reference voltage of the analog-to-digital converter. When this happens, the top and bottom of the signal’s waveform are ‘clipped’ or flattened, producing a severely distorted square wave rich in harmonics. This overload is digital clipping that creates false signals and ruins the ability of the digital signal processor (DSP) to correctly demodulate the desired signal.
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