摘要:
In a multi-carrier system employing OFDM, for example DMT, an adaptive channel equalizer is normally used, operating in the frequency domain. The sampling clock is controlled so that the time delay between the transmitter and the receiver is effectively eliminated. If the information used to control the sampling clock is received from the equalized data stream, it will introduce an ambiguity between the operation of the channel equalizer and the mechanism used to control the sampling clock. Operation of the equalizer can mask an increasing time difference, between transmitter and receiver, which the sample clock controller should be tracking. The present invention eliminates the ambiguities in the operation of the equalizer and sample clock controller by preventing the equalizer from accepting time differences which should be corrected by operation of the sample clock controller.
摘要:
An endless conveyor belt for an air conditioning plant, in which the conveyor belt extends helically along part of its length, comprising transverse rods (4) and lateral elements (3). The conveyor belt is characterised in that the lateral elements (3) are connected in pairs to only two rods (4), which are fixedly connected to said lateral elements (3) and form, with these, a link means (2), and adjoining link means (2) are articulated to each other by a coupling element (5) arranged therebetween and connected to neighbouring rods (4) of the adjoining link means (2).
摘要:
A device (4) for transferring a pattern to an object (2). The invention relates especially to production of micro and nanostructures. The device comprises an alignment means (10) arranged in connection with a first contacting means (7) for controlling the motion of the first stamp (8) in a direction perpendicular to the pressing direction (A), and a second contacting means (11) having a second stamp (12) adapted to imprint a second pattern in the second surface (6) of the object (2), and a pressing means (9) further adapted to press the second stamp (12) into contact with the second surface (6) of the object (2) in the pressing direction (A). Hereby is obtained a device of a simple design, which has a high accuracy of the alignment of the stamps in relation to the object.
摘要:
A multi-carrier transmission system has a plurality of transceivers, each having a receiver and a transmitter. Data is transmitted between the transceivers by modulating the data onto a multiplicity of carrier waves in the form of multi-bit symbols, wherein each carrier wave constitutes a channel, and wherein the number of bits per symbol (the bit loading), varies between channels and, within a channel, with time, so that each channel has associated therewith a bit loading parameter. In operation, the multi-carrier system is adapted to synchronously update, at the transceivers, the bit loading parameters associated with each channel by transmission of data over a control channel, in that the control channel is established, at system start-up, on a predetermined one of the multiplicity of carrier waves whose identity is known to the transceivers, and in that the control channel is, after start-up, changed from the predetermined channel to a further channel, selected by the first transceiver on the basis of channel characteristics.
摘要:
With OFDM systems the frequency domain data is the Fourier transform of the received time domain OFDM frames. The time domain frames must be sampled, at the receiver, in synchronism with the transmitter, so that each received frame contains data from only a single transmitted frame. It is vital for this synchronism to be maintained in order to maintain the orthogonality of the frames. A typical multi-carrier system, of the OFDM type, which uses a cyclic prefix permits orthogonality to be maintained when there is a small deviation from exact frame synchronisation. Because the signalling interval includes both an entire frame and the cyclic prefix, which is a repetition of part of the frame, a frame sampled within the signalling interval will contain data from only one frame. Since the signalling interval is greater than the frame period, this gives some leeway in frame alignment. In a multi-carrier system of the OFDM type, an adaptive channel equalizer, operating in the frequency domain, is often used. The internal parameters in such an equalizer contain, in addition to information about the characteristics of the channel, information which can be interpreted as the time deviation between the sampling clocks of the transmitter and the receiver. The present invention utilizes this information to control the sampling clock of the receiver in a more robust way than has previously been possible with known techniques. The present invention is particularly suitable for use in ADSL and VDSL modems which can be used to give broadband access over copper networks. The invention is also of relevance to broadband transmission in mobile and semi-mobile systems for transmission over the radio channels.
摘要:
A RFI canceller, for use in a subscriber line system using multi-carrier modulation, measures a RFI disturbance in carriers falling within a band of frequencies causing the RFI. The RFI ingress into carriers outside the band of frequencies is estimated, and an error correcting signal derived from the estimation of the RFI ingress is subtracted from a received signal. The subscriber line system may be a VDSL system and the multi-carrier modulation may be DMT. The RFI canceller includes a demodulator for demodulating an incoming data stream to provide a first parallel data stream. A parallel to serial convertor converts the first parallel data stream to a first serial data stream. A digital to analogue convertor converts the first serial data stream to a first analogue signal. An analogue RFI canceller circuit combines the analogue signal with an analogue error correcting signal, to produce a second analogue signal. An analogue to digital convertor converts the second analogue signal to a second serial data signal. A serial to parallel convertor converts the second serial data stream to a second parallel data stream. A modulator modulates the second parallel data stream onto a multiplicity of carriers.
摘要:
A transmission system using nQAM. A control channel is superimposed on a nQAM data channel. It is desirable to separate control channel data from user data without using a higher level protocol layer. In multi-carrier systems with variable bit-loading it is particularly desirable that the control channel data be separable from user data when the value of n. that is the bit-loading, or constellation identifier are unknown. Binary data is transmitted using nQAM modulation. The binary data includes both user data and control data. This means that a control channel is superimposed on a user data channel within the same nQAM constellation. Separation of the control data is facilitated by arranging control data points to have either a unique phase or unique amplitude values. These unique values are not employed for user data points.
摘要:
A multi-carrier transmission system. A received multi-carrier signal is sampled and digitized before FFT processing. Multi-carrier signals consist of many narrow band carrier waves which convey data via a wide band channel. The amplitude distribution of the sum of all the individual carriers is Gaussian. This means that high amplitudes occur with low probability. At the present time, analog to digital converters have a limited dynamic range. It is therefore normal practice to provide a compromise between cutting and quantization noise. The adverse affects of a course quantization have to be balanced between signal distortions caused by the loss of the low probability high amplitude signals.
摘要:
A method of making, by etching, depressions in selected portions of an etching surface of an electrically conductive etching material, the depressions forming an etching pattern, comprises the step of contacting the etching material with an etchant. A passivating layer is formed on the etching material which layer decreases or stops the etching capability of the etchant on the surface and which is dissolved in a chemical reaction when exposed to electromagnetic radiation. An electrode with electrically conductive electrode portions in selected portions of an electrode surface is provided, the electrode portions forming an electrode pattern corresponding to the etching pattern. The electrode is arranged in contact with the etchant and with the electrode portions facing the etching surface of the etching material, an electric voltage is applied between the electrode and the etching material, and the etching material is exposed to electromagnetic radiation essentially perpendicular to the etching surface.
摘要:
Methods for the central preparation and distribution of a concentrate to a plurality of medical treatment devices are disclosed comprising supplying a stream of substantially only water to a central container which includes a single salt composition at least partially in solid form, producing a substantially saturated solution of the salt composition in the central container, and distributing the salt solution to a distribution conduit which includes a plurality of concentrate connectors whereby the salt solution can be distributed to the plurality of medical treatment devices. Methods for disinfecting this apparatus, the apparatus itself, and containers for use in the apparatus are also disclosed.