Communication Principles

A filter located before the systems sampling circuit.

It limits the frequencies in the pre sampled signal to the folding frequency

2

Folding Frequency fH <= fS / 2To minimise aliasing the filter must have a sufficiently rapid roll-off and sufficient attenuation above the city off frequency.

2To minimise aliasing the filter must have a sufficiently rapid roll-off and sufficient attenuation above the city off frequency.

To minimise aliasing the filter must have a sufficiently rapid roll-off and sufficient attenuation above the city off frequency.

When the pdf of an analogue signal is not uniform, we should ensure that the most frequently used quantization levels introduce the least quantization noise.

Creates a uniform pdf and optimum SNqR isbthe signal pdf is known.

Creates a constant SNqR if the signal pdf is unknown.

Speech has an unpredictable mean amplitude so this is used to fix the SNqR.

Finds the bit by taking a measurement at the center of the bit and then compares this value to a reference value.

They perform a demodulation to decouple noise between sections.

-Presence or Absence of a DC level

-Power spectral density

-Spectral occupancy (BW size)

-Noise immunity

-Transparency

-Easy of clock recovery for symbol timing

-Inherent error detection properties

-Require only a single positive supply voltage

- The DC component is wasted power

-Requires AGC at its receiver to ensure correct threshold detection

-Cannot be used with AC coupled lines

- The signal is distorted due to forcing of spectral density to 0 at DC.

Sending a long chain of 1s results in charge developing on the capacitor. This results in signal droop.

It is a Pseudo-ternary format that denotes a binary 0 as zero volts and a binary 1 as +V and -V alternating.

It ensures a DC null in the signal spectrum thus allowing AC coupling

It prevents a long term DC build up due to many 1s, thus avoiding signal droop.

Reduces the signal bandwidth

Long strings of 0s may result in the loss of receiver clock synchronisation.

A form of Bipolar RZ signalling where a string of four 0s is substituted with a 0001 or 1001, where the last mark violates the AMI rules allowing the code word to be detected.

Where n binary symbols are mapped to m ternary symbols. This increases the length of transmitted symbols and decreases the bandwidth of the resulting ternary signal.

It uses a dipolar pulse for a digital 0 and a NRZ bipolar pulse for a digital 1.

Because rectangular pulses have a sinc spectrum which has a large bandwidth.

A signal which passes through zero at all but one sampling instant.

-Sinc goes to infinity on both ends

-Has no ISI

-We only need a small timing error before ISI occurs as sinc pulses have steep sides

-Unrealistic demands on symbol timing to do a good job.

Excess bandwidth is traded off for more rapidly decaying sidelobes in the received pulses.

We can take multiple samples of a single pulse, this will help solve the issue of noise.

An integration over one pulse period is performed. This gives an integration value to evaluate. The integrator can be made easily in analogue using a resistor and capacitor.

The value on the integrator is then dumped by shorting the switch/capacitor, thus resetting the value to zero.

This method makes the effect of noise miniscule.

The impulse response of the filter is a time reversed version of the pulse to which it is matched, it is then delayed by a time equal to the duration of the pulse.

Signal Power: Es ^2

Noise Power: ( N0 / 2 ) Es

S/N = 2Es / N0

Their output waveforms

Their sensitivity to timing errors, with timing errors we could easily go from positive to negative.

These are used to see if everything is working at the put it.

The eye diagram has many overlayed pulses / data symbols and the colour of said pulses determine their probability.

They can be used to determine:

-ISI

-The optimum sampling time

-Jitter

- The noise margin

It is a quantization that converts an analogue signal to a digital signal.