S-parameters were introduced in 1920 by E.W. Matthews Jr. They quantify RF energy propagation through multi-port networks. S-parameters are complex numbers representing input-output paths. Network parameters like Y- and Z-parameters were primary before 1950s
Radar uses short-wavelength microwaves to detect objects and measure their direction and distance. Radar works like sound waves, reflecting off objects to calculate distance. Distance calculation uses formula: D = 1/2 × cT, where c is speed of light
Microwave region spans 1,000-300,000 MHz, used for high-speed satellite communications. Parabolic dish antennas produce beams that can be directed like searchlights. Microwave radar measures distances and speeds using reflected wave pulses. Microwaves penetrate smoke but scatter water droplets in weather forecasting. Microwaves can heat food but destroy tissue above 43°C
Stub is a transmission line connected at one end only. Input impedance is purely reactive, either capacitive or inductive. Behavior depends on stub length relative to radio wave wavelength. Can be constructed with various transmission lines including coaxial and waveguides
Heinrich Hertz proved radio waves were reflected by metallic objects in 1886-1888. Christian Hülsmeyer developed first ship detection device in 1904. Rudolf Kühnhold pioneered pulsed radar development in Germany in 1930s
Horn antenna consists of flaring metal waveguide shaped like a horn. Operates at frequencies above 300 MHz as feed or calibration antenna. Provides gradual impedance matching to radiate waves efficiently. Typical gain ranges up to 25 dBi, with 10-20 dBi being typical