System for improving the quality of a received radio signal

Details System for improving the quality of a received radio signal System for improving the quality of a received radio signal

H - Electricity

04

B

H04B 7/04 (2006.01) H04B 7/06 (2006.01) H04B 7/08 (2006.01) H04L 1/06 (2006.01) H04L 1/08 (2006.01) H04B 1/12 (2006.01) H04B 1/713 (2006.01)

Patent

CA 2275283

A delay spread is created in a digital radio signal to reduce the coherence bandwidth and facilitate frequency hopping to reduce the effect of fading losses within an enclosed propagation environment. The delay spread is introduced into the signal in several ways. One technique disclosed employs a transmitter (21) with two separate antennas (26, 27) one of which transmits the digital signal and the other of which transmits the same signal after a phase delay (25) has been introduced into the signal. The carrier frequency of the signals is hopped between at least two frequencies and the receiver processes the resulting signals. In another embodiment, a single transmit antenna (42) is used but the signal is received by two different antennas (43, 44) with the output signal from one of those antennas being phase delayed (45) before combining (46) it with the other prior to processing by the receiver circuitry (47). Phase delay (115) is also introduced at baseband into the signals to be transmitted by rotating the I and Q components of the waveforms before modulation.

On crée un étalement du temps de propagation dans la transmission d'un signal radio numérique de manière à réduire la largeur de bande de cohérence et à faciliter les sauts de fréquence permettant la réduction des pertes d'affaiblissement au sein d'un environnement de propagation fermé. L'étalement du temps de propagation est introduit dans le signal de plusieurs manières. Un procédé de l'invention met en oeuvre un émetteur (21) pourvus de deux antennes distinctes (26, 27), l'une de ces antennes émettant le signal numérique et l'autre émettant le même signal après introduction d'un retard de phase dans le signal. La fréquence porteuse des signaux effectue des sauts entre au moins deux fréquences et le récepteur traite les signaux reçus. Selon une autre réalisation de l'invention, on utilise une antenne d'émission (42) unique mais le signal est reçu par deux antennes différentes (43, 44), le signal de sortie de l'une de ces antennes subissant un retard de phase (45) avant d'être combiné (46) avec l'autre, et avant d'être traité par les circuits récepteurs (47). On peut également introduire le retard de phase (115) au niveau de la bande de base dans les signaux à émettre en faisant tourner les composantes I et Q des ondes avant la modulation.

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