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High CMRR Instrumentation Amplifier (Schematic and Layout) design for biomedical applications

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Instrumentation amplifiers are intended to be used whenever acquisition of a useful signal is difficult. IA’s must have extremely high input impedances because source impedances may be high and/or unbalanced. bias and offset currents are low and relatively stable so that the source impedance need not be constant. Balanced differential inputs are provided so that the signal source may be referenced to any reasonable level independent of the IA output load reference. Common mode rejection, a measure of input balance, is very high so that noise pickup and ground drops, characteristic of remote sensor applications, are minimized.Care is taken to provide high, well characterized stability of critical parameters under varying conditions, such as changing temperatures and supply voltages. Finally, all components that are critical to the performance of the IA are internal to the device. The precision of an IA is provided at the expense of flexibility. By committing to the one specific task of
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Multipath in radio Communication

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Multipath
· Multipath is a term used to describe the multiple paths a radio wave may follow
between transmitter and receiver. Such propagation paths include the ground wave,
ionospheric refraction, reradiation by the ionospheric layers, reflection from the
Earth's surface or from more than one ionospheric layer, etc.
· If the two signals reach the receiver in-phase (both signals are at the same point in
the wave cycle when they reach the receiver), then the signal is amplified. This is
known as an “upfade.” If the two waves reach the receiver out-of-phase (the two
signals are at opposite points in the wave cycle when they reach the receiver), they
weaken the overall received signal. If the two waves are 180º apart when they reach
the receiver, they can completely cancel each other out so that a radio does not
receive a signal at all. A location where a signal is canceled out by multipath is called
a “null” or “downfade.”

· If the reflecting surfaces that cause the multipath situation do not move, the locations
of the maxima and minima will not move, hence the name ‘standing wave’.
· The depth of the null in a standing wave pattern is dependent upon the magnitude of
the reflection coefficient of any reflecting surface.

· The Effects of Multipath Propagation
o Multiple copies of a signal may arrive at different phases
o If phases add destructively, the signal level relative to noise declines, making
detection more difficult.
o Dealy Spread resulting in Intersymbol interference (ISI) - one or more delayed
copies of a pulse may arrive at the same time as the primary pulse for a
subsequent bit