Pulse or digital communications – Systems using alternating or pulsating current – Angle modulation
Reexamination Certificate
1999-04-26
2003-09-02
Chin, Stephen (Department: 2634)
Pulse or digital communications
Systems using alternating or pulsating current
Angle modulation
C375S139000
Reexamination Certificate
active
06614853
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a transmission method in accordance with the precharacterizing clause of claim
1
, as well as a transmitter-receiver arrangement for execution of the method in accordance with the precharacterizing clause of claim
7
.
BACKGROUND OF THE INVENTION
In the case of known transmission methods, the communication to be transmitted is modulated in the transmitter onto a high frequency carrier signal and forwarded over the transmission distance to the receiver, which, for recovery of the communication displays an appropriate demodulator. There exists comprehensive literature concerning modulation of analog signals. Modern communication methods use digital or digitized data, since these types of signals can be processed rapidly and in cost-effective fashion by means of signal path processor technology, with the means available today, even in the case of a large amount of information.
If the communication signal to be transmitted is present in digitized form as a bit sequence—as is the case in modern mobile radio networks—then modulation is accomplished by changing the frequency, the phase or the amplitude of the carrier signal as a function of the particular value of the information of the bit series to be transmitted. As concerns digital modulation of carrier signals, known from COUCH, L. W.: Digital and Analog Communication Systems, 4th Edition, Macmillan Publishing Company (1993) are various digital modulation methods, for example Amplitude Shift Keying (ASK), Two-Phase Shift Keying (2-PSK), Two-Frequency Shift Keying (2-FSK), or more recent methods such as the spread spectrum modulation method. In each case, demodulation takes place in the receiver corresponding to the modulation method used at the transmitter, and therewith recovery of the digital communication signal as bit sequence in the form of pulses following one after the other. A known modulation method of communication technology, as mentioned, provides angle modulation as the generic term for frequency or phase modulation. In the case of the known methods, this type of modulation, however, serves exclusively for the purpose of superimposing the communication onto a carrier.
With all the methods of this type, there exists the disadvantage that the quality of the communication signal recovered at the receiver decreases strongly with the distance between receiver and transmitter, with disturbance elements over the transmission distance.
In order to achieve a prescribed protection against disturbances over a desired range in the case of transmission of a communication over a disturbance-encumbered transmission distance, transmitter power may not drop below a predetermined value.
First, the therewith required high transmitting power has the disadvantage that the radiated power during transmitting operation is correspondingly high, which, in particular in the case of battery-operated devices, as with mobile telephones, is disturbing because of rapid battery depletion. Secondly, there exist fears that the electromagnetic radiation emanating from the transmitter can lead to damage to the human body. This is to be taken into consideration in particular in the case of mobile telephones because of the comparatively short distance to the user.
SUMMARY OF THE INVENTION
The task underlying the invention is to obtain a transmission method of the initially mentioned type, or to be precise, a receiver-transmitter arrangement for execution of the method, which, with in general at least transmission quality remaining the same, enables a reduction in transmitting power or an increase in range.
This task, starting out from a method in accordance with the precharacterizing clause of claim
1
, is resolved by its characterizing features, or relative to the arrangement for execution of the method, by the features of claim
7
.
The invention includes the technical teaching to transmit “folded (doubled) pulses” between transmitter and receiver, which are specially designed pulses that are defined in more detail later. These folded pulses, because of their particular characteristics, can be used not only for raising the amplitude by appropriate compression methods with correspondingly suited dispersion filters, but also because of their particular, highly correlative properties can be used for additional correlative and auto-correlative suppression of noise compared to the signal. The particular modulation and the special composition of these transmitting elements, called here “folded pulses”, permit raising the signal-to-noise ratio in the analog signal processing at the receiver. In this way there can be achieved through an improvement of the signal-to-noise ratio in the receiver a reduction of transmitting power or an increase in range or alternatively a reduction of the error rate.
To be understood here under the concept “folded pulse”, and in what follows, is the superposition of at least two opposed, angle-modulated pulses (components) having essentially the same duration—in their basic form also designated as “chirp signals”, whereby the angle modulation of the two pulses results from the fact that the frequency of the one component changes, in the mathematical sense increasing monotonically during the duration of the pulse—and in the second pulse component decreasing monotonically. The folded pulse is, therefore, to be defined as that it simultaneously consists of at least two angle modulated pulses (chirp signals) at a frequency varying counter to each other, with the relative phase position of the components to each other also capable of further being used for differentiating these types of signals.
For a better understanding of chirp signals, the components of the “folded pulses”, let first their basic properties and next the special, advantageous properties of the folded pulses be dealt with.
An angle modulated pulse of a certain time duration &Dgr;t having a certain frequency deviation &Dgr;f is, among other things, capable of being characterized by its time-bandwidth product &PSgr;=&Dgr;t·&Dgr;f. Through special, so-called “dispersion filters” that are four-polar with a defined differential delay time behavior, it is possible to push together, that is to say, compress such angle-modulated pulses along the time axis, in the receiver. The energy of the original pulse of duration &Dgr;t [s] having the amplitude U
0
[V] across the resistance R
1
[&OHgr;], which is given by the expression (U
0
2
·&Dgr;t)/R
1
, is retained in compression, in the first instance, as assumed loss-free dispersion. Accordingly, for the shorter compressed pulse of duration &dgr; one can estimate the energy with (Û
2
·&dgr;)R
1
, where Û[V] represents the increased pulse amplitude resulting from compression.
Hence one obtains
(
U
0
2
·&Dgr;t)/
R
1
=(Û
2
·&dgr;)/
R
1
Accordingly, the ratio of the squares of the voltages is equal to the inverse ratio of the times between the originally transmitted pulse of duration &Dgr;t and the average duration &dgr; of the compressed pulse, applicable, therefore
Û
2
=U
0
2
·&Dgr;t/&dgr;=U
0
2
·&Dgr;t·&Dgr;f=U
0
2
·&PSgr;,
where &dgr;=1/&Dgr;f. Accordingly, the voltage in the receiver is raised by compression by a factor that corresponds directly to the root of the time/bandwidth product.
Hence, the chirp pulse, when it is compressed through dispersion filters, produces a first improvement of the signal-to-noise ratio. Because the signal-to-noise ratio &rgr;[dB] is defined by 20times the logarithm of the ratio of the signal voltage Û[V] to the noise voltage Ur[V], With the above equations on obtains:
&rgr;=20log(
Û/Ur=
10log((
U
0
2
/Ur
2
)&psgr;)=10log(
U
0
2
/Ur
2
)+10log&psgr;
whereby can be seen that the S/N ratio &rgr; is improved by the portion +10log&psgr;.
These relationships are known and at the present time are used, for other reasons, only in radar technology and for transmission of signals in optical lines, however not for general
Ianelli Zbigniew
Koslar Manfred
Altera Law Group LLC
Chin Stephen
Kim Kevin
Nanotron Gesellschaft fur Mikrotechnik mbH
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