Deutsche Forschungsanstalt Fur Luft-und Raumfahrt E.v.

Blaupunkt-werke Gmbh

Peter Hoher

Joachim Hagenauer

Harald Bochmann

Henrik Schulze

A novel receiver for subcarriers in a radio broadcasting system is described, in which the characteristic frequency of the mixing oscillator is varied under program control. An incoming signal from antenna 1 passes through an input stage 2 to a mixing stage 3. Mixing stage 3 receives the output of an oscillator 4. The output of the mixing stage passes into an intermediate frequency filter stage 5, which preferably includes A/D converters 13 and demultiplexers 14. Stage 5 feeds a plurality of demodulators 6, which may include equalizers 12. Buffer memories 7 store information from demodulated subcarrier signals, and feed an evaluation unit 8. Evaluation unit 8 has a first output which drives a speaker 9 and a second output which is applied to a memory 11. A control unit 10, connected to the output of memory 11, controls the frequency generated by mixing oscillator 4. This system facilitates digital signal transmission by compensating for poor transmission conditions which would otherwise cause serious dropouts in the digital signal.

Digital radio receiver with program-controlled mixing oscillator

In a method for generalizing the conventional Viterbi algorithm, in which the transition costs are formed in a metric increment unit (TMU) and adding, comparing and selection are performed in a succeeding add-compare-select (ACS) unit, the difference costs from two arriving paths are calculated for each individual state, the reliability information at the beginning of each path being set to the highest value. Then the reliability value of the path with the least costs is updated at the points where the information points differ from the competing path, updating being performed in accordance with a table, and where the prior value of the reliability information and the difference costs are inserted into the table as the new input values. Then this new value is taken from the table and is stored, together with hard decisions, as path memory, where storage can be in the form of fixed or floating point values. Finally the analog value decision is read out from the point which, after a decision delay, is the result for the path with the lowest cost and where the hard decisions of the conventional Viterbi algorithm are the sign of the analog value decision. By means of the method according to the invention a Viterbi algorithm has been created at the output of which analog value decisions, i.e. soft decisions are supplied.

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Seefeld, Germany

Peter Hoher