Pulse or digital communications – Spread spectrum – Chirp
Reexamination Certificate
1999-04-26
2002-10-15
Phu, Phuong (Department: 2631)
Pulse or digital communications
Spread spectrum
Chirp
C359S199200
Reexamination Certificate
active
06466609
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method as in claim
1
, as well as to a transmitter and receiver arrangement for implementation of the method as in claim
12
.
In wireless information transfer methods, that are well known to the expert from standard reference works, the information signal to be transmitted is modulated upon a high frequency carrier signal in the transmitter and transferred over a transmission path to the receiver, which contains a corresponding demodulator for the recovery of the information signal. A well known modulation method in telecommunications is the angle modulation (as generic term for frequency and phase modulation).
If the information signal to be transmitted is present in digital form as a bit sequence, as is the case in modern mobile radio networks, then the modulation is carried out by variation of the frequency, or phase, or amplitude of the carrier signal, depending on the bit sequence to be transmitted. Various digital modulation methods are known, for example from COUCH, L. W.: Digital and Analog Communication Systems, 4
th
Edition, Macmillan Publishing Company (1993), among them amplitude-shift keying (ASK: Amplitude Shift Keying), two phase-shift keying (2-PSK: Phase Shift Keying) or two frequency-shift keying (2-FSK: Frequency Shift Keying). Here too a demodulation is carried out in the receiver according to the modulation method employed on the transmitter side, thus effecting a recovery of the digital information signal as a bit sequence in form of consecutive pulses.
The use of several different modulation methods for different messages, or message components, as part of a continuous transmission process is known to the expert, for example from analogue television engineering, where the vestigial side-band amplitude modulation is used for the luminance signal, the frequency modulation for the audio signal, and the IQ modulation for the chrominance signal. Here too, the variation of the carrier parameter s serves only in the imprinting of the information and has no effect on noise of the transmission path.
A method for expansion of emitted tracking pulses on the transmitter side and compression on the receiver side is known from radar technology (“Chirp”-technique); compare E. Philippow (Publisher.): Taschenbuch der Elektrotechnik, Vol. 4, Systeme der Informationstechnik, Berlin 1985, p. 340,341. Hereby an analogue frequency modulation or a digital phase modulation is applied in the compression, but no imprinting of information takes place. This method serves in the reduction of the expended transmission power, and thus a potential opponent's ability to detect the signals, while simultaneously maintaining range and accuracy of coverage.
A basic physical problem exists in all communication methods: the quality of the information signal that is recovered on the receiver side decreases with the amount of interference on the transmission path (always present in reality), and thus with the distance between transmitter and receiver. To obtain a desired working distance at a predetermined noise immunity in a communication over a noisy transmission path, a certain transmission power is necessary, which, for example for mobile communications, is in the range of Watts.
On one hand, the required transmitting power has the disadvantage that the energy consumption during the transmitting operation is correspondingly high, which in particular for battery or accumulator battery operated devices, such as mobile telephones, is a problem, due to the rapid depletion of the energy store. On the other hand, the rising, number of communication transmitters caused by the explosive distribution of mobile telephones, the increasing number of providers of radio broadcasts and television programs etc, increases the total impact of electromagnetic radiation on humans (so called “human exposure”). Harm to the human body can not be ruled out, in particular for mobile telephones at the presently customary transmitter power, due to the very low distance of the transmitter to the use's head.
SUMMARY OF THE INVENTION
This invention has the objective to develop a method of the type mentioned at the beginning, and an arrangement for the implementation thereof, which allows a reduction in transmission power and/or and increase in range while maintaining at least equal transmission quality.
This objective is met, starting with a method according to claim
1
, by this method's characterizing features, and—regarding the arrangement for implementing the method—by the features of claim
12
.
The invention includes the principal thought to use two independent modulation methods to imprint the information onto a carrier (information signal modulation) and to achieve extensive suppression of noise on the transmission path, in particular of the thermal or “white” noise (carrier signal modulation).
The pulses that have been modulated, or are to be modulated, with the information according to a well known method of telecommunications, in the transmitter are subjected to an angle modulation (which here is to be understood as generic term for phase and frequency modulation) with a special characteristic. The angle modulated pulses, showing a predetermined frequency spectrum, are time compressed in the receiver by introducing a frequency dependent delay. Thus an amplitude enhancement results at the receiver output, compared to the amplitude of the transmitted signal, and thus to the noise level. In particular, this pulse compression/amplitude enhancement can be carried out using a dispersive filter. The information signal is recovered from the carrier processed in this manner by demodulation, whereby the demodulation of the information signal occurs with a signal
oise ratio improved by the amplitude enhancement.
The improvement of the signal
oise ratio is dependent on the bandwidth-time-product of the bandwidth used in the angle modulation and the pulse duration, and is especially prominent in poor transmission conditions.
The actual information can be imprinted onto the carrier by pulse modulation techniques, or by carrying out the carrier compression so that it can be evaluated in different ways for different states of the information signal, so that the information is contained in this variation of the angle modulation. Hereby it is important that the modulation of the information has no, or only secondary, influence on the signal delay time.
After the demodulation the available signal is of a quality, which in the state of technology could only be achieved by increased transmitting power or by costly methods for the improvement of reception (such as diversity reception or redundant transmission). A further advantage of this invention's method lies in the essentially lower potential for interference compared to other transmission paths, because a predetermined signal
oise ratio can be achieved after the pulse compression in the receiver using lower transmitting power. In addition, the lower demands on the transmitting power lead to a reduced human exposure. The disadvantage of this method, a higher required bandwidth, and thus a reduced channel capacity or transfer rate (bit rate) can be accepted for many areas of application, and can be partially eliminated through the selection of a matching pulse modulation method for the modulation of the information (see below).
A special angle modulation time characteristic is used in the variable angle modulation, which corresponds to a “modulation characteristic curve”. Hereby, the modulation characteristic curve—here referred to as modulation characteristic—determines the time behavior of the frequency during the duration of each pulse. When a linearly falling modulation characteristic is used, the frequency of the transmitted signal decreases linearly, during the duration of each pulse, from a value above the carrier frequency to one lying below the carrier frequency. Analogously, a linearly rising characteristic can be used. The filter on the receiver side is matched to the (employed modulati
Ianelli Zbigniew
Koslar Manfred
Merchant & Gould P.C.
Nanotron Gesellschaft fur Mikrotechnik mbH
Phu Phuong
LandOfFree
Method for wireless information transfer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for wireless information transfer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for wireless information transfer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2925233