Transmission Process

1. Baseband Signal Processing

Digital Signal Generation: Data (such as voice, images, or text) is converted into digital signals in the baseband processor.

Modulation: The digital signal is modulated by a modulator and loaded onto a high-frequency carrier. Common modulation methods include amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM).

2. Radio Frequency Signal Conversion

Up-conversion: The modulated signal is mixed with a high-frequency signal generated by a local oscillator through a mixer, raising the signal frequency to the radio frequency band.

Filtering: The up-converted signal passes through a filter to remove unwanted spurious frequency components, retaining the desired radio frequency signal.

3. Signal Amplification

Power Amplification: The radio frequency signal is amplified by a power amplifier (PA) to increase signal strength, ensuring long-distance transmission.

Filtering: A second filtering step removes noise and distortion generated during amplification.

4. Signal Transmission

Antenna Radiation: The amplified radio frequency signal is converted into electromagnetic waves by an antenna and radiated into space.

Reception Process

1. Signal Reception

Antenna Reception: The antenna receives electromagnetic waves in space and converts them into a weak radio frequency (RF) signal.

2. Signal Amplification and Filtering

Low-Noise Amplification: The signal first passes through a low-noise amplifier (LNA) to amplify the weak signal while minimizing the introduction of noise.

Filtering: Filters remove out-of-band noise and interference signals, retaining the signal in the desired frequency band.

3. RF Signal Conversion

Down-Conversion: The signal is mixed with the signal generated by the local oscillator through a mixer, reducing the RF signal frequency to the intermediate frequency (IF) or baseband frequency.

Filtering: Further filtering removes spurious signals generated during the mixing process.

4. Demodulation and Baseband Processing

Demodulation: The IF signal passes through a demodulator to recover the original baseband signal.

Baseband Processing: The demodulated signal undergoes digital signal processing in the baseband processor, including decoding and error correction, ultimately restoring the original data.

In summary, the radio frequency (RF) module achieves the transmission and reception of wireless signals through a series of processes including modulation, up-conversion, amplification, transmission, reception, down-conversion, and demodulation. This process involves analog and digital signal processing technologies and is the foundation of wireless communication systems.