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ing of the system. As an example, a bus error excess delay the arrival times of a compo- nent of the impulse response of a wideband excess loss the ratio of the actual propa- gation loss between two antennas to the free Usually ex- pressed in decibels. excess noise (1) thermal noise in excess or exceeding thermal noise at 290 ◦ K. The ex- cess noise ratio (ENR) is the ratio of the ex- ◦ K, expressed in decibels. (2) Noise in excess of the thermal noise ( n e ), which is a function of the device, fre- quency and bias current, also known as 1 /f , 1 /f a , flicker or popcorn noise. This noise rapidly dies off such that above a few mega- ENR = 10 log 10 T − 290 ◦ K 290 ◦ K n e = f device, 1/f a , I bias excess noise ratio (ENR) a noise source used in noise figure measurements. ENR is excess-N representation method of rep- resenting floating point numbers, in which a −40 would be stored as the value 88. exchangeable disk See excimer a molecule formed by the excited state of one atom and one or more other atoms excimer laser laser using a gas or gases to create an excited dimer (e.g., KrF), usually excitation population of excited states of a laser medium at the expense of some energy excitation system the DC voltage source and its accompanying control and protection exciter a DC source that supplies the field current to produce a magnetic flux in an elec- exciting current the current drawn by a transformer primary with its secondary open I c and the magnetizing branch cur- rent I m . The exciting current I e is also the current measured in the open circuit test on exciton laser laser (or laser-like system) in which the amplified field consists of ex- exclusive OR Boolean binary operator typically used for comparing the status of ⊕ ≡ X XOR Y c 2000 by CRC Press LLC |