What type of modulation employs frequency hopping across multiple carriers?

The type of modulation that employs frequency hopping across multiple carriers is known as spread spectrum modulation. This technique involves rapidly switching the carrier frequency among many different frequencies, as determined by a pseudorandom sequence. This frequency hopping makes it more difficult for unauthorized receivers to intercept the signal and enhances resistance to interference, thus improving communication reliability.

In spread spectrum systems, the spreading of the signal across a wider bandwidth allows for more robust data transmission, ensuring that even if a particular frequency is affected by noise or interference, the overall communication can still be successfully received. This method is commonly used in various modern communication technologies, including Bluetooth and some wireless networking standards, emphasizing its significance in secure and reliable communications.

Other modulation techniques mentioned, such as amplitude modulation, single sideband modulation, and continuous wave modulation, do not involve the frequency hopping characteristic. Amplitude modulation alters the amplitude of the carrier wave to convey information, while single sideband modulation is a refinement of amplitude modulation that reduces bandwidth by eliminating one sideband. Continuous wave modulation involves transmitting information in a constant wave form, typically using two distinct states, rather than hopping between multiple frequencies.