Definitions used in Radar

Mach Number: The ratio of the velocity of a body to the speed of sound in the medium that is being considered. In the atmosphere, the speed of sound varies with temperature and atmospheric pressure, hence, so does mach number.

Magnetron: A magnetron is a thermionic vacuum tube which is constructed with a permanent magnet forming a part of the tube and which generates microwave power. These devices are commonly used as the power output stage of radar transmitters operating in the frequency range above 1000 MHz and are used less commonly down to about 400 MHz. A magnetron has two concentric cylindrical electrodes. On a conventional magnetron, the inner one is the cathode and the outer one is the anode. The opposite is true for a coaxial magnetron.

Magnetron Oscillator: An Electron tube that provides a high power output. Theory of operation is based on interaction of electrons with the crossed electric and magnetic fields in a resonant cavity. A high-vacuum tube in which the interaction of an electronic space charge and a resonant system converts direct current power into ac power, usually at microwave frequencies. The magnetron has good efficiency, is capable of high power outputs, and is stable.

Marine Radar: An X-Band or S-Band radar used on ships, boats or other marine craft.

Master Oscillator: In a transmitter, the oscillator that establishes the carrier frequency of the output.

Matched Filter: This describes the bandwidth of an IF amplifier that maximizes the signal-to-noise ratio in the receiver output. This bandwidth is a function of the pulse-width of the signal.

Meaconing: A system receiving radio signals and re-broadcasting them (or just transmitting) on the same frequency to confuse navigation. The meaconing station attempts to cause aircraft to receive inaccurate range or bearing information.

Mechanical Scanning: The reflector, its feed source, or the entire antenna is moved in a desired pattern.

Medium Altitude Orbit: An orbit from 2,000 to 12,000 miles above the earth. The rotation rate of the earth and satellite are quite different, and the satellite moves quickly across the sky.

MEGA: A prefix meaning 10⁶ (times one million). For example megahertz (MHz)

Microvolt per Meter: A commonly used unit of field strength at a given point. The field strength is measured by locating a standard receiving antenna at that point, and the "microvolts per meter" value is then the ratio of the antenna voltage in microvolts to the effective antenna length in meters. Usually used below 100 MHz. Above 100 MHz, power density terminology is normally used.

Microwave Amplification by Stimulated Emission of Radiation: [MASER] A low-noise radio-frequency amplifier. The emission of energy stored in a molecular or atomic system by a microwave power supply is stimulated by the input signal.

Millimeter Band: A band of frequencies ranging from 30 to 300GHz, also called the EHF band.

Minimum Discernible Signal: [MDS] The weakest signal that produces a usable signal at the output of a receiver. The weaker the signal, the more sensitive the receiver. The receiver input power level that is just sufficient to produce a detectable/discernible signal in the receiver output.