Qam in a sentence

Since QAM is usually square, some of these are rare—the most common forms are 16-QAM, 64-QAM and 256-QAM.

Also, the error-rate performance of 8-QAM is close to that of 16-QAM (only about 0.5 dB better), but its data rate is only three-quarters that of 16-QAM.

Quantized QAM Digital 16-QAM with example constellation points As in many digital modulation schemes, the constellation diagram is useful for QAM.

Analog QAM Analog QAM: measured PAL colour bar signal on a vector analyser screen.

In QAM, the constellation points are usually arranged in a square grid with equal vertical and horizontal spacing, although other configurations are possible (e.g. Cross-QAM).

In the UK, 64-QAM is used for digital terrestrial television ( Freeview ) whilst 256-QAM is used for Freeview-HD.

PSK modulators are often designed using the QAM principle, but are not considered as QAM since the amplitude of the modulated carrier signal is constant.

The 16-QAM constellation is suboptimal although the optimal one may be constructed along the same lines as the 8-QAM constellation.

The circular 8-QAM constellation is known to be the optimal 8-QAM constellation in the sense of requiring the least mean power for a given minimum Euclidean distance.

The first rectangular QAM constellation usually encountered is 16-QAM, the constellation diagram for which is shown here.

Analog QAM suffers from the same problem as Single-sideband modulation : the exact phase of the carrier is required for correct demodulation at the receiver.

Arbitrarily high spectral efficiencies can be achieved with QAM by setting a suitable constellation size, limited only by the noise level and linearity of the communications channel.

Both of these terms became outmoded in the late 20th century except in specialist usage, as most fax machines now use the digital ITU-T fax standards, which encode the image digitally over a QAM-modulated signal.

Consider a (L×M)-QAM system with 2 · log2 L levels and 2 · log2M levels in the I-channel and Q-channel, respectively and a two-dimensional grey code mapping employed.

Expressions for the symbol-error rate of rectangular QAM are not hard to derive but yield rather unpleasant expressions.

If data-rates beyond those offered by 8- PSK are required, it is more usual to move to QAM since it achieves a greater distance between adjacent points in the I-Q plane by distributing the points more evenly.

In particular, all telephone modems faster than 300 bit/s use quadrature amplitude modulation (QAM).

In QAM, an inphase signal (or I, with one example being a cosine waveform) and a quadrature phase signal (or Q, with an example being a sine wave) are amplitude modulated with a finite number of amplitudes, and then summed.

In the case of QAM, the amplitude of two waves of the same frequency, 90° out-of-phase with each other (in quadrature) are changed (modulated or keyed) to represent the data signal.

In the digital QAM case, a finite number of at least two phases and at least two amplitudes are used.