0
The answer is simply that QAM is very sensitive to phase error, and a frequency mismatch between the TX and RX radios is equivalent to a constantly increasing phase error. (Remember freq = change phase over change time) An IQ constellation of a QAM signal which has no PLL for carrier recovery will likely look like concentric circles.
In the ideal world, carrier recovery would not be required because the exact frequency used to modulate a signal would be used to demodulate the signal and no phase error would exist. However, in real world communications there are many factors that introduce frequency mismatches. Some examples include doppler frequency shift (resulting from moving objects), Tx or Rx LO frequency offsets, or A/D sampling rate offsets.
Wiki User
∙ 12y ago
Add your answer:
Earn +20 pts
What is the modulation technique used in microwave pdh as nec equipment?
QAM... (16 QAM, 256 QAM) according to capacity
What are the difference between QAM and QPSK?
in qpsk we are using phases for representation of messages while in qam we hav amplitude levels. in qpsk 2 bits per symbol is used with four different phases. in qam depanding on type i.e 16 qam,64 qam,256 qam how many amplitude levels to be used accordingly i.e 16,64,256. sonender kumar
A QAM configuration uses four phases and one amplitude with a given bit rate of 1200 bps what is the minimum required bandwidth?
600
What is the advantage of qam over ask and psk?
PSK and QAM modulation have two advantages over ASK: *They are not as susceptible to noise. *Each signal change can represent more than one bit PSK Disadvantage more complex signal detection / recovery process, than in ASK and FSK QAM advantage: · data rate = 2 bits per bit-interval! · higher data rate than in PSK (2 bits per bit interval), while bandwidth occupancy remains the same • 4-PSK can easily be extended to 8-PSK, i.e. n-PSK • however, higher rate PSK schemes are limited by the ability of equipment to distinguish small differences in phase uses "two-dimensional" signaling • original information stream is split into two sequences that consist of odd and even symbols · 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. QAM is used extensively as a modulation scheme for digital telecommunication systems. 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. · Noise immunity of QAM is very high. · QAM is best suitable for high bit rates. · Low error probability. · Baud rate is half the bit rate therefore more effective utilization of the available bandwidth of the transmission channel.
What is take in the am abbreviated?
qam
How many frequencies does a full-duplex QAM-128 modem use?
You are asking this question because you are trying to cheat on your homework!
What does the medical abbreviation 2 cap QAM mean?
2 cap QAM means two capsules each morning
What does the term QAM refer to?
The term "QAM" refers to many different things. Some things "QAM" might refer to include "Quality Assurance Manual," "Quadrature Amplitude Modulation," "Queensland Air Museum" and "Quality Assurance Monitor."
Does u verse run on cable or analog?
Qam
What is the modulation technique used in microwave sdh?
Qam only
How is baud rate related to transmission bandwidth in QAM?
cvbcb
Lasix 60 mg po qam how many tablets should you give?
the order reads lasix 60 mg po qam. how many tablets should you give
