Pulse or digital communications – Repeaters – Testing
Patent
1992-02-11
1995-03-28
Chin, Stephen
Pulse or digital communications
Repeaters
Testing
329306, 375329, 375344, 375345, H04L 2706
Patent
active
054024498
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method of converting a digitally modulated reception signal from the radio-frequency range, in which the reception signal, which can be represented as a complex vector, is converted in-coherently into the baseband. The invention relates furthermore to a receiver for digitally modulated signals in a mobile communication system, the antenna of which is connected to at least one mixing stage for the reception signal which can be represented as a complex vector, the mixing stage being followed by two low-pass filters which are connected on the output side via an analog-digital converter in each case to a value converter.
A receiver operating by such a method is known from PCT International Publication WO 86/3356. The reception signal is converted by two mixers with a local oscillator in correct phase relation and phase-shifted by 90.degree.. Low-pass filters and analog-digital converters are followed by a digital filter. The decoding of the transmitted bits is performed with a ROM, operating as a value converter, which is followed by a multiplexer (FIG. 17).
A reception method and a receiver for cordless telephones is described in Telcom Report 10 (1987), issue 2, pages 130 to 137. The reception signal is mixed into the baseband via a radio-frequency stage and a plurality of intermediate-frequency stages. The demodulation is performed in phase-locked loop.
In general, digitally modulated signals are processed by synchronous or, more rarely, asynchronous heterodyne receivers. An image frequency suppression is performed at the radio-frequency stage, the main selection at one to two intermediate-frequency stages. Limiter amplifiers or gain controls provide the necessary compensation of the dynamic range of the input signal. Linear modulation methods divide into two-stage methods with binary amplitude modulation (BAM) and binary phase-shift keying (BPSK), four-stage methods with quadrature amplitude modulation (QAM) and quadrature phase-shift keying (QPSK), as well as multistage modifications. Customary non-linear modulation methods are FSK or frequency modulation-like methods, such as minimum-shift keying (MSK) and Gaussian minimum-shift keying (GMSK). The demodulation is performed for non-linear modulation methods by means of phase lock loop, Costa's loop or discriminators. For linear modulation methods, synchronous quadrature demodulators are used.
SUMMARY OF THE INVENTION
The invention is based on the object of permitting the processing of signals digitally modulated at two or more stages with a receiver.
According to the present invention, this is achieved by arranging that the reception signal is split into a real component and an imaginary component, continuous in time and amplitude, the phase difference per bit period due to the incoherent conversion being kept to less than half the phase shift caused by the modulation per bit, the signal components are subsequently amplified, filtered and sampled, the sampling time being determined within a preceding synchronization time, the sampled signals are subsequently digitized and the sampled values are value-converted as a pair of binary numbers for the magnitude and angle of the vector, the magnitude value serving for gain control and reception data being recovered from the difference between two successive angle values after classification.
Due to a homodyne mode of operation, the occurrence of an image frequency is avoided. The incoherent demodulation avoids complex carrier synchronization and allows DC voltage-free signal paths. The phase difference is kept small by frequency correction or oscillators with exact frequency stability. In spite of using only one mixing stage, with this method of reception virtually all two-stage and multistage, linear and non-linear modulation methods can be employed.
An efficient angle decoding beyond 360.degree. is achieved by an angle value being buffer-stored over a bit period, subtracted from the following value by two's complement and the reception data recovered f
REFERENCES:
patent: 4438524 (1984-03-01), Muilwijk
patent: 4608703 (1986-08-01), Kaga et al.
patent: 4737969 (1988-04-01), Steel et al.
patent: 4866395 (1989-12-01), Hostetter
patent: 4879728 (1989-11-01), Tarallo
patent: 4888793 (1989-12-01), Chanroo et al.
patent: 4958360 (1990-09-01), Sari
Telcom Report 10 (1987) issue 2, pp. 130-137.
"Bandwidth & Power Efficient Satellite TDMA Demodulator" by Hoeber et al, Proceedings ICDSC-7, 7th International Conference on Digital Satellite Communications, May 12, 1986, pp. 573-578.
Bonek Ernst
Scholtz Arpad-Ludwig
Schultes Gerhard
Chin Stephen
Siemens Aktiengesellschaft
Vo Don
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