What year does angle modulation first introduced?

Angle modulation was first introduced in the early 20th century. The concept of frequency modulation (FM) was first proposed by Edwin Armstrong in 1922, and he later developed the first practical FM radio transmitter and receiver in the mid-1930s. Armstrong's FM radio technology was eventually adopted as the standard for high-fidelity broadcasting, and it remains in use today for many radio and television broadcasting applications.

Phase modulation (PM) was also introduced in the early 20th century, but it did not become widely used until much later. PM was first used in military communication systems in the 1950s, and it was later adopted for commercial use in digital communication systems. Today, PM is widely used in many different types of digital communication systems, including cellular phone networks, satellite communication, and wireless data transmission.