*Question G7C11:
Which of these functions is performed by software in a software-defined radio (SDR)?*  

*Correct Answer is  D: All these choices are correct*  

### AI Response: (may contain errors)  

In a software-defined radio (SDR), many functions traditionally performed by hardware are instead executed by software. This flexibility allows for a wide range of operations to be performed using the same hardware platform.

1. **Why the correct answer is correct:**
   - **All these choices are correct** because SDRs utilize software to perform various functions, including:
     - **Filtering**: Software can implement digital filters to remove unwanted signals or noise.
     - **Detection**: Signal detection algorithms can be executed in software to identify and decode signals.
     - **Modulation**: Different modulation schemes can be applied through software, allowing for easy switching between modes without changing hardware.

2. **Why the other choices are incorrect:**
   - Each of the individual choices (A, B, and C) is indeed a function performed by software in an SDR. Therefore, selecting any one of them alone would not fully capture the capabilities of an SDR. The correct answer encompasses all these functions, making it the most accurate choice.

3. **Useful concepts:**
   - **Digital Signal Processing (DSP)**: SDRs rely heavily on DSP techniques to manipulate signals in the digital domain.
   - **Flexibility**: SDRs can be reprogrammed to adapt to new standards or protocols, which is a significant advantage over traditional hardware radios.

In summary, the correct answer is "All these choices are correct" because SDRs can perform filtering, detection, and modulation through software, showcasing their versatility and adaptability in radio communications.