Ant Nachrichtentechnik Gmbh

Karlheinz Grotz

Heinz Gockler

Georg Sussmeier

Klaus Krull

Wolfgang Bambach

Jorg Mayer

Jann Binder

A method is provided for linearizing variations in a transfer characteristic of a digital-to-analog (D/A) converter to which a digitized input signal is fed for being converted to an analog output signal. The method includes balancing the D/A converter so that essentially only negative differential variations result in the transfer characteristic at identified locations; determining amplitudes of the negative differential variations; and adding, with an inverse operational sign, the respective amplitudes of the negative differential variations to the input signal of the D/A converter at the respective locations of the variations.

Method of linearizing variations in the transfer characteristic of a D/A

For the preparation of data such as digitized television channel signals or television channel bundles, useful data are periodically replaced by a frame marker (F) in at least one of N parallel partial data streams of different bit significance. For this replacement, a partial data stream of low bit significance is selected because there the degradation is lowest. Because of this measure, the bit rate does not have to be increased in order to include a frame marker and a simple structure is possible for the multiplexer and demultiplexer at the respective transmission interfaces.

Method and arrangement for inserting frame markers in data for

A distribution system, useful with radio and television distribution, for distributing a signal having a plurality of channels includes a central station. The central station produces a first frequency division multiplexed signal in which signals from a plurality of channels or channel groups are frequency-converted and combined, and introduces the first frequency division multiplexed signal into transmission media of the distribution system. The first frequency division multiplexed signal may include occupied channels, freely selectable occupied channels, and free channels. A plurality of further stations receive the first frequency division multiplexed signal from the central station and process it with signals of a plurality of further channels to produce a second frequency division multiplexed signal. The signals of the plurality of further channels may be put in free channels, or used to replace signals in freely selectable occupied channels of the first frequency division multiplexed signal. A plurality of user devices receive the second frequency division multiplexed signal from at least one of the plurality of further stations, and split it into individual channel or channel group signals for user access.

Radio and television distribution system

A drop-and-add multiplexer for receiving an incoming FDM signal with a plurality of channels, for receiving signals of additional channels, and for outputting an outgoing FDM signal. The multiplexer includes at least one single channel filter for receiving an incoming FDM signal, filtering the incoming FDM signal by blocking a selected channel frequency, and outputting a filtered FDM signal. At least one interpolating digital frequency converter receives another channel signal which is not in the incoming FDM signal, converts the other channel signal into a channel frequency which has been blocked by the at least one single channel filter or was an empty channel frequency in the incoming FDM signal, and outputs a converted other channel signal. At least one digital frequency converter is provided and includes a cascade connection of a decimating digital frequency converter and an interpolating digital frequency converter, for receiving the incoming FDM signal, frequency-converting a selected channel from an input frequency to a different outgoing frequency, and outputting a frequency-converted channel signal. An adder adds the converted other channel signal output by the interpolating digital frequency converter, the filtered FDM signal output by the single channel filter, and the frequency-converted channel signal output by the digital frequency converter, and outputs an outgoing FDM signal.

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Fellbach, Germany

Karlheinz Grotz