*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 of the functions traditionally performed by hardware are instead implemented in software. This flexibility allows SDRs to adapt to different communication standards and protocols by simply updating the software.

1. **Why the correct answer is correct:**

   - **Filtering**: In SDRs, filtering is often done digitally. This means that the software can apply various digital filter algorithms to process the incoming or outgoing signals, allowing for precise control over bandwidth and selectivity.
   
   - **Detection**: Detection, or demodulation, is the process of extracting the information from a modulated carrier wave. In SDRs, this is typically handled by software algorithms that can be adjusted or changed to accommodate different modulation schemes.
   
   - **Modulation**: Modulation is the process of varying a carrier signal in order to transmit data. In SDRs, modulation is performed by software, which can easily switch between different modulation types (e.g., AM, FM, PSK) as needed.

2. **Why the other choices are incorrect:**

   - Each of the individual choices (A: Filtering, B: Detection, C: Modulation) is a function that can be performed by software in an SDR. Therefore, none of these choices are incorrect on their own. However, the question asks which functions are performed by software, and since all these functions can be performed by software, the correct answer is D: All these choices are correct.

3. **Useful concepts:**

   - **Digital Signal Processing (DSP)**: SDRs rely heavily on DSP techniques to perform tasks like filtering, detection, and modulation. DSP allows for the manipulation of signals in the digital domain, providing flexibility and precision.
   
   - **Flexibility of SDRs**: The primary advantage of SDRs is their ability to be reconfigured for different tasks by updating the software, rather than changing hardware components. This makes them highly versatile in various communication applications.

In summary, SDRs perform filtering, detection, and modulation through software, making all the choices correct. This software-based approach provides significant flexibility and adaptability in radio communications.