Pulse or digital communications – Systems using alternating or pulsating current – Amplitude modulation
Reexamination Certificate
1999-05-03
2001-10-16
Tse, Young T. (Department: 2634)
Pulse or digital communications
Systems using alternating or pulsating current
Amplitude modulation
C455S017000, C235S492000
Reexamination Certificate
active
06304613
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a data carrier comprising the means specified hereinafter, namely receiving means adapted to receive and to supply an amplitude-modulated carrier signal which has been amplitude-modulated in dependence on data to be transmitted, and rectifier means to which the received amplitude-modulated carrier signal can be applied in order to be rectified and which are adapted to generate a d.c. supply voltage corresponding to the received amplitude-modulated carrier signal, and voltage limiting means adapted to limit the d.c. supply voltage generated with the aid of the rectifier means to a first limit value, and amplitude demodulation means to which the received amplitude-modulated carrier signal can be applied in order to be demodulated and which are adapted to supply a data signal representative of the data to be transmitted, and data processing means adapted to process the data signal supplied by the amplitude demodulation means, the data processing means having a power supply input, which power supply input is arranged to receive the d.c. supply voltage.
The invention further relates to a circuit comprising the means specified hereinafter, namely rectifier means to which a received amplitude-modulated carrier signal which has been amplitude-modulated in dependence on data to be transmitted can be applied in order to rectify the carrier signal and which are adapted to generate a d.c. supply voltage corresponding to the received amplitude-modulated carrier signal, and voltage limiting means adapted to limit the d.c. supply voltage generated with the aid of the rectifier means to a first limit value, and amplitude demodulation means to which the received amplitude-modulated carrier signal can be applied in order to be demodulated and which are adapted to supply a data signal representative of the data to be transmitted, and data processing means adapted to process the data signal supplied by the amplitude demodulation means, the data processing means having a power supply input, which power supply input is arranged to receive the d.c. supply voltage.
Such a data carrier of the type defined in the first paragraph and such a circuit of the type defined in the second paragraph are known, for example from the document WO 96/38814 A2. Such a data carrier serves for the contactless communication with a transmitting/receiving station. In order to transmit data from the transmitting/receiving station to such a data carrier (transponder) a carrier signal is amplitude-modulated in the transmitting/receiving station, which amplitude modulation is effected in dependence on the data to be transmitted.
In such data carrier systems comprising at least one transmitting/receiving station and at least one data carrier it is known to carry out an amplitude modulation of the carrier signal with a modulation percentage of 100%. The advantage of such an amplitude modulation essentially resides in the fact that the amplitude modulation means required for this can simply be implemented as an integrated circuit. A disadvantage of such an amplitude modulation with a modulation percentage of 100% is that the sideband signals which occur when this amplitude modulation is used have a comparatively high level, which often gives rise to problems in complying with national regulations as regards spurious emission.
In order to avoid the afore-mentioned problems as a result of sideband signals of comparatively high levels it is also known to use an amplitude modulation with a comparatively low modulation percentage, for example a modulation percentage of approximately 10%.
When such an amplitude modulation with a low modulation percentage is used a data carrier of the type defined in the first paragraph unfortunately has the problem that the voltage limiting means, which are connected to the rectifier means and which serve for limiting the d.c. supply voltage, derived from the received amplitude-modulated carrier signal with the aid of the rectifier means, to a first limit value, counteract the amplitude modulation in the amplitude-modulated carrier signal received by the receiving means and supplied by the receiving means, which results in the amplitude modulation being evened out. Unfortunately, during the demodulation of the received amplitude-modulated carrier signal by means the amplitude demodulation means this evening-out of the amplitude modulation, which is equivalent to a reduction of the modulation percentage, may lead to problems, as a result of which errors may occur in the data signal representing the data to be transmitted and supplied by the amplitude demodulation means, which is obviously undesirable.
SUMMARY OF THE INVENTION
It is an object of the invention to preclude the afore-mentioned problems with a data carrier of the type defined in the first paragraph and with a circuit of the type defined in the second paragraph, in which a received amplitude-modulated carrier signal is amplitude-modulated with a comparatively low modulation percentage, and to provide an improved data carrier and an improved circuit.
In order to achieve this object in a data carrier of the type defined in the first paragraph, the invention provides that as regards their limiting action for limiting the d.c. supply voltage to its first limit value the voltage limiting means are adapted to be controllable by means of a control signal and furthermore respond with a delay to amplitude variations in the received amplitude-modulated carrier signal and that, in addition, the voltage limiting means are adapted to limit the d.c. supply voltage generated with the aid of the rectifier means to a second limit value and their limiting action for limiting the d.c. supply voltage to its second limit value is such that they respond without delay to amplitude variations in the received amplitude-modulated carrier signal, and in that the second limit value attainable by the voltage limiting means is higher than the first limit value attainable by the voltage limiting means.
In order to achieve this object in a circuit of the type defined in the second paragraph, the invention provides that as regards their limiting action for limiting the d.c. supply voltage to its first limit value the voltage limiting means are adapted to be controllable by means of a control signal and furthermore respond with a delay to amplitude variations in the received amplitude-modulated carrier signal and that, in addition, the voltage limiting means are adapted to limit the d.c. supply voltage generated with the aid of the rectifier means to a second limit value and their limiting action for limiting the d.c. supply voltage to its second limit value is such that they respond without delay to amplitude variations in the received amplitude-modulated carrier signal, and that the second limit value attainable by the voltage limiting means is higher than the first limit value attainable by the voltage limiting means.
By taking the measures in accordance with the invention it is achieved by means which can be realized very simple that during normal operation of a data carrier in accordance with the invention and of a circuit in accordance with the invention the voltage limiting means, which serve for limiting the supply voltage to a value which is permissible for the data processing means, always respond with a delay to amplitude variations in the received amplitude-modulated carrier signal, thereby assuring in a very simple manner that amplitude transitions in the received amplitude-modulated carrier signal are not reduced or evened out by the voltage limiting means, i.e. that the modulation percentage of the received amplitude-modulated carrier signal is not reduced. Moreover, by means of the measures in accordance with the invention it is achieved that in the case that a data carrier in accordance with the invention comprising a circuit in accordance with the invention is directly and suddenly brought into the so-called near field of a transmitting/receiving station, i.e. is situated at only a few centimeters from t
Koller Manfred
Thuringer Peter
Tse Young T.
U.S. Philips Corporation
LandOfFree
Data carrier having rectifier and improved voltage limiter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data carrier having rectifier and improved voltage limiter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data carrier having rectifier and improved voltage limiter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2595005