Modulators – Frequency modulator – Plural modulation
Patent
1996-06-12
1997-12-02
Mis, David
Modulators
Frequency modulator
Plural modulation
332117, 332144, 332149, 331 78, H03B 2900, H03C 500
Patent
active
056940947
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase of PCT/DE 94/01479 filed 13 Dec. 1994 and based, in turn, upon German national application P 43 42 520.8 of 14 Dec. 1993 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a generator for high frequency (HF) oscillations as well as to a process for arbitrary HF modulation. It does not however relate to pure oscillations. Rather variations in time (modulation) of the three HF parameters, frequency, phase and/or amplitude can be used to communicate information.
BACKGROUND OF THE INVENTION
High frequency modulation functions can be selectively (arbitrarily) chosen as long as the character content of the HF oscillation is not entirely lost (narrow band character). In the generation of noise, certain random conditions underlie the modulation functions.
In measurement technology, increasingly frequency modulation sources and amplitude modulation sources and especially noise sources are used which must cover a characteristic frequency range. These methods enable simultaneous determination of relevant, possibly correspondingly weighted, frequency components. For audio purposes this is almost always customary since in speech transmission the respective determinations of a single frequency component does not allow any logic conclusions.
Such techniques are also of interest in the high frequency sector because of the modulation requirements of present day multichannel transmission. HF modulated signals arise in communication transmission. For test measurements of transmission lines with coded signals, noise signals are desirable or required. Modulation signals and noise signals in the high frequency sector, i.e. for frequencies of greater than several megahertz could heretofore only be realized by analog frequency conversion processes.
In one such conversion process, the modulation component or noise component low-frequency analog or digital is generated by means of a signal source and subsequent filters and thereafter is shifted in frequency in an analog sense.
This shift by a predetermined carrier frequency is brought about by a frequency mixer. The variation of the carrier and modulation characteristic or noise characteristic are effected separately for the measurement technology, the latter by variation in the filter parameters. This sequential process gives rise to errors in the resulting signals. Using this process a modulation or noise signal is obtained with a shifted frequency (carrier) which is the same to both sides, i.e. is symmetric.
A mathematically precise synthesis and affect upon the signal is not possible by this earlier process. To characterize a measured object a time-shifted evaluation of the measurement signals applied to the measured object and the measured signals after they have traversed the measured object is required.
Where only one measurement channel is available there are enhanced requirements as to the invariance with time (reproducibility) while in the case of the channels there is an enhanced requirement for synchronism of both channels. As a consequence in addition to the test measurement on the measured object, continuous calibration and comparison measurements are required.
A purely digital directly synthesized signal can by contrast in principle be precalculated. Systematic deviations can be compensated by anticipatory compensation. Directly synthesized noise signals are generated today in the audio range by arbitrary word generators whereby for frequencies up to the kilohertz range a continuous computation in real time is possible.
In the high frequency range, this process cannot be used any longer since the output speeds of such word generators cannot approach the rapid change in time of the signals and/or a sufficient storage time is not available. A calculation in real time is excluded on technical grounds. A limited storage depth can indeed be made competitive by a periodic output of a word sequence but this however is not suitable for noise generation of high
REFERENCES:
patent: 5329260 (1994-07-01), Poplin
patent: 5570307 (1996-10-01), Takahashi
Heinrichs Gunter
Meuth Hermann
Schnase Alexander
Stockhorst Hans
Dubno Herbert
Forschungszentrum Julich GmbH
Mis David
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