Pulse or digital communications – Spread spectrum – Frequency hopping
Reexamination Certificate
1999-12-30
2003-11-25
Ghebretinsae, Temesghen (Department: 2631)
Pulse or digital communications
Spread spectrum
Frequency hopping
C455S265000
Reexamination Certificate
active
06654406
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C §119 from an application entitled Frequency Hopping Receiver Capable Of Real-time demodulation And Method Thereof earlier filed in the Korean Industrial Property Office on Dec. 30 1998, and there duly assigned Serial No. 98-60738 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a frequency hopping system, and more particularly, to a frequency hopping receiver in which a received signal is processed in real time, and a method thereof.
2. Description of the Related Art
In communication systems, generally, the receiving side demodulates a modulated signal transmitted from the transmitting side to detect the original signal, whereby communications between the transmitting and receiving sides are performed. A frequency hopping system is used to secure these transmitted and received signals.
In the frequency hopping system, the transmitting side widens the bandwidth of a signal by irregularly changing the carrier frequency of a signal to be transmitted, in accordance with a hopping pattern with respect to time, thus transmitting a resultant signal. The receiving side receives a carrier frequency used upon modulation performed at the transmitting side, and demodulates a received signal in accordance with a hopping pattern which synchronizes with the received carrier frequency.
However, during the demodulation of a received signal at the receiving side, when the frequency of a received carrier wave is changed in accordance with a hopping pattern, some time, that is, a frequency transition time during which frequency is not stable, is required. If the receiving side demodulates a received signal during the frequency transition time, an error may be generated.
In order to solve this problem, the receiving side in a conventional frequency hopping system stores a signal received during the frequency transition time, in a storage module included therein. After the frequency transition time has passed, that is, after a changed frequency becomes stable, the receiving side demodulates the received signal using the stabilized carrier frequency.
However, in this case, signal demodulation is delayed for the frequency transition time for carrier generation, which prevents the receiving side from performing real time demodulation on a received signal.
SUMMARY OF THE INVENTION
To solve the above problem, it is an objective of the present invention to provide a frequency hopping receiver capable of demodulating a received signal in real time, and a method thereof.
Accordingly, to achieve the above objective, the present intention provides a frequency hopping receiver capable of real-time demodulation, the receiver including first and second frequency generators, a switch, a controller and a demodulator. The first frequency generator receives a first frequency control signal according to a predetermined control and generates a predetermined frequency first carrier wave used to generate a synthesized carrier wave for demodulating the received signal. The second frequency generator receives a second frequency control signal according to a predetermined control and generates a predetermined frequency second carrier wave used to generate the synthesized carrier wave for demodulating the received signal. The switch switches between the first and second carrier waves in response to a signal for selecting a carrier wave, to generate a continuous synthesized carrier wave. The controller generates the first and second frequency control signals for carrier generation and transmits the first and second frequency control signals to the first and second frequency generators, respectively, when the transmitted signal is received, generates a carrier selection signal for selecting either the first carrier wave generated by the first frequency generator or the second carrier wave generated by the second frequency generator, and generates a demodulation control signal for initiating demodulation when the synthesized carrier wave is generated by the switch. The demodulator receives the synthesized carrier wave from the switch and the demodulation control signal from the controller, and demodulates the received signal.
It is preferable that the frequency of the first carrier wave generated by the first frequency generator is different from the frequency of the second carrier wave generated by the second frequency generator.
To achieve the above objective, the present intention provides a frequency hopping receiving method capable of real-time demodulation, the method including the steps of: (a) generating first and second frequency control signals for carrier generation having predetermined frequencies, when the transmitted signal is received; (b) receiving the first and second frequency control signals and generating a first carrier wave having a first frequency and a second carrier wave having a second frequency, wherein the two first and second carrier waves are used to generate a synthesized carrier for demodulation of the received signal; (c) switching between the first and second carrier waves according to a predetermined method to generate a continuous synthesized carrier wave; and (d) demodulating the received signal using the synthesized carrier wave after the synthesized carrier is produced.
REFERENCES:
patent: 4479226 (1984-10-01), Prabhu et al.
patent: 5734707 (1998-03-01), El-Wailly
patent: 6047015 (2000-04-01), Watanabe et al.
patent: 9930018.8 (2000-07-01), None
patent: WO 83/03505 (1993-10-01), None
“Search Report” dated on Jan. 31, 2000 issued by U.K. Patent Office.
Hong Byung-Il
Kim Jae-Hwan
Burd Kevin M
Busnell, Esq. Robert E.
Ghebretinsae Temesghen
Samsung Thomson-CFS Co., Ltd.
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