摘要:
Digital frequency demodulation is accomplished by monitoring similar transitions in an FM radio signal to determine frequency. Time intervals between similar transitions in the FM signal are established by selecting anticipated transition times and accumulating error values relative to actual transition times. Accumulated error values provide a basis for further selecting anticipated transition times in such manner that a reported sequence of anticipated transition times provides a basis for inferring signal frequency. In one illustrated embodiment, the chosen transition times are positive transitions in the FM signal and the antipicated times of transition are taken from a set of two time periods, an early transition and a late transition relative to a valid transition window. In one embodiment of the invention, accumulated error is stored in an integrator device while in another embodiment accumulated error is stored in the phase of a bi-frequency oscillator. By reporting the selected anticipation times by associated values in a digital bit stream, frequency may be inferred by computing a ratio of given digital values in the bit stream relative to the total number of samples in the bit stream.
摘要:
Dans le cas du convertisseur analogique-numérique interpolatif pour signaux de passe-bande selon l'invention, la quantification d'amplitudes des valeurs de balayage est effectuée dans 2 étages placés en série, le premier étage comprenant l'interface analogique-numérique proprement dite, et le second étage étant purement numérqiue. La quantification d'amplitudes des valeurs de balayage ne se fait pas ici, comme dans le cas des autres procédés, en utilisant des éléments finement quantifiés sur l'interface analogique-numérique, mais elle se fait par surbalayage, formation spectrale du bruit de quantification et interpolation numérique. Ceci permet d'utiliser sur l'interface analogique-numérique proprement dite des éléments à très basse définition (dans le cas extrême seulement avec 2 étages de quantification).
摘要:
Methods, systems, and devices are described for an adaptive demodulator that supports multiple modes. An FM signal may be received at a demodulator and parameters corresponding to the FM signal may be identified. Connections between multiple modules within the demodulator may be configured, based at least in part on the parameters, to select one of multiple demodulation modes supported by the demodulator to demodulate the FM signal. The modes may include a phase differencing mode, a phase-locked loop (PLL) mode, a frequency-compressive feedback (FCF) mode, and/or a quadrature detector mode. The parameters may include one or both of a signal strength of the FM signal and a maximum frequency deviation of the FM signal. Based on the parameters, one or more signals may be generated to configure the connections within the demodulator. A switch from one mode to another may occur when one of the parameters breaches a threshold value.
摘要:
Zur Modulation eines Trägers mit einem digitalen Videosignal wird ein digitaler Doppel-Gegentakt-Modulator verwendet, dem eingangsseitig das durch Abtasten mit einer Abtastfrequenz f a digitalisierte Videosignal zugeführt wird und der mit der halben Abtastfrequenz f a /2 des Videosignals als Trägerfrequenz getaktet ist, so daß jeder zweite Abtastwert des Videosignals invertiert wird.
摘要:
Verfahren zur Demodulation von frequenzmodulierten Signalen, wobei das Empfangssignal abgetastet wird, mit einem Bandfilter, das komplexwertige Koeffizienten aufweist, gefiltert wird, anschließend differenziert wird und nach einer Betragsbildung das gewünschte Phaseninkrement gewonnen wird. Sehr aufwandsgünstiges Verfahren, das einen Einsatz insbesondere bei der Demodulation von UKW-FM-Signalen empfiehlt.
摘要:
A digital zero IF circuit having first and second signal paths 111, 110 to which a radio frequency signal is applied, each path including a sampling and digitising means 121, 12Q and a digital filter means 13l, 13Q, the circuit including a clock generator arranged to generate two clock pulse trains in quadrature phase relationship, each sampling means being operated in response to a respective one of the clock pulse trains.