Carrier-to-noise ratio

About: Carrier-to-noise ratio is a research topic. Over the lifetime, 408 publications have been published within this topic receiving 3985 citations.

Chromatic dispersion in fiber-optic microwave and millimeter-wave links

Abstract: The influence of chromatic fiber-dispersion on the transmission distance of fiber-optic microwave and millimeter-wave links is analyzed and discussed in this paper. It is shown that dispersion significantly limits the transmission distance in intensity modulated direct detection links operating in the above 20 GHz frequency region by inducing a carrier to noise penalty on the transmitted signal. At 60 GHz, a 1 dB penalty is induced after less than 500 m transmission over standard single-mode fiber with a dispersion of 17 ps/km/spl middot/nm and the signal is completely extinct after 1 km. In remote heterodyne detection links, the dispersion induces both a carrier to noise penalty and a phase noise increase on the transmitted signal. It is shown, however, that the induced carrier to noise penalty is insignificant. At 60 GHz, the induced penalty is less than 0.3 dB after 100 km transmission. The phase noise increase proves more dominant. At 60 GHz, a 150 Mbit/s QPSK signal is limited to around 10 km of transmission.

Apparatus comprising a broadcast receiver circuit and provided with an antenna

Abstract: The invention relates to an apparatus 1 comprising a broadcast receiver circuit, an embedded antenna for receiving broadcast signals and a tuning circuit coupled between the antenna and the receiver circuit, which tuning circuit comprises a filter circuit coupled to ground, wherein the tuning circuit is designed to have a first resonance at a first frequency below a broadcast band of interest, and a second resonance at a second frequency above the broadcast band and wherein the tuning circuit comprises an amplifier with an output to the receiver circuit and with an input to the filter circuit, and wherein the tuning circuit is provided with a carrier to noise ratio (CNR) which is substantially flat across the broadcast band.

Automatic modulation classification using zero crossing

Abstract: A modulation recogniser that automatically reports modulation types of constant-envelope modulated signals is developed using zero-crossing techniques The zero-crossing sampler, as a signal conditioner, has the advantage of providing accurate phase transition information over a wide dynamic frequency range Signal parameters such as zero-crossing variance, carrier-to-noise ratio (CNR) and carrier frequency are estimated Phase difference and zero-crossing interval histograms play the role of features for modulation recognition The classifier performance is given in the form of a confusion matrix The simulation results obtained demonstrate that a reasonable average probability of correct classification is achievable for CNR ≥ 15 dB

Carrier recovery system using acquisition and tracking modes and automatic carrier-to-noise estimation

Abstract: A carrier recovery system for use in illustratively a passband QAM (quadrature amplitude modulation) demodulator (10) and specifically such a system, including apparatus and accompanying methods, that employs separate acquisition and tracking modes and automatic carrier-to-noise estimation. In particular, a carrier recovery system (200) is operated in two modes: an acquisition mode to first attain an initial carrier lock, during which simplified reduced constellation slicing is used to determine a quadrant of each incoming symbol; and a tracking (or lock) mode, during which full slicing is used, to accurately track variations in frequency and phase that may occur to a carrier while the system remains locked. The mode changes based upon whether, e.g., the average error energy associated with fully sliced symbols is greater than or less than a pre-defined switching threshold value. The value of the switching threshold changes in a pre-determined manner with changes in noise content, particularly a carrier-to-noise ratio (CNR), of the received symbols. Two appropriately spaced switching threshold values, one for use in each mode, can be used to provide enhanced operational stability. An implementation of a QAM CNR estimator circuit (800) is also provided.

BER computation of 4/M-QAM hierarchical constellations

Abstract: Hierarchical constellations offer a different degree of protection to the transmitted messages according to their relative importance. As such they found interesting application in digital video broadcasting systems as well as wireless multimedia services. Although a great deal of attention has been devoted in the literature to the study of the bit error rate (BER) performance of uniform quadrature amplitude modulation (QAM) constellations, very few results were published on the BER performance of hierarchical QAM constellations. Indeed the only available expressions "leading-term" approximate BER expressions for 4/16-QAM and 4/64-QAM. We obtain exact and generic expressions in M for the BER of the 4/M-QAM (square and rectangular) constellations over additive white Gaussian noise (AWGN) and fading channels. For the AWGN case, these expressions are in the form of a weighted sum of complementary error functions and are solely dependent on the constellation size M, the carrier-to-noise ratio, and a constellation parameter which controls the relative message importance. Because of their generic nature, these new expressions readily allow numerical evaluation for various cases of practical interest. In particular numerical results show that the leading-term approximation gives significantly optimistic BER values at low carrier-to-noise ratio (CNR) in particular over Rayleigh fading channels but is quite accurate in the high CNR region.