Koninklijke Philips Corporation N.V.

Simon Derek Bramwell

William Redman-White

Willem Marie Julia Marcel Coene

Johannes Wilhelmus Maria Bergmans

Rob Otte

An arrangement for selecting the largest of a plurality of input currents (pma (k&#x2212;1), pmb (k&#x2212;1)) and adding a further current (Ibmk) to the selected current, the arrangement comprising: a plurality of inputs () for receiving said input currents; a further input () for receiving said further current; an output () for delivering an output current proportional to the sum of the largest of the input currents and the further current; means for feeding each of the received input currents to the main current conducting path of a respective transistor, (T, T) each of the transistors having its control electrode connected to a common point; a respective follower transistor (T, T) connected between the input and the common point; and a mirror transistor (T) having its control electrode connected to the common point for producing a current whose value is related to that of the largest input current. The currents through transistors (T, T) are summed and sensed by a diode connected transistor (T) whose gate voltage is stored on a capacitor (C, C) by means of respective switches (S, S). The voltages across the capacitors (C, C) are fed via respective switches (S, S) to the gate electrodes of transistors (T, T) whose drain electrodes feed an output current (pmc (k&#x2212;)) to outputs () of the arrangement. A plurality of such arrangements are used for producing path metric currents for a Viterbi decoder.

Dada decoding

An optical disk data decoder generates estimates of serial input signal values by slicing them into samples. The data sequences contained in each sample are detected. Successive samples are compared and used to increase or decrease the estimates. Such permits the center bit in a string of identical bits to be detected after subsequent bits have already been received and are being processed.

Data decoding

A partial response maximum likelihood (PRML) bit detection apparatus is disclosed for deriving a bit sequence (x ) from an input information signal. The apparatus comprises input means for receiving the input information signal. The apparatus further comprises sampling means for sampling the input information signal at sampling instants so as to obtain samples (z ) of the information signal at said sampling instants. The apparatus also comprises calculating means ( ) for (a) calculating ( ) at a sampling instant t for one or more of a plurality of states s (Sa, Sb, Sc) at said sampling instant, an optimum path metric value PM(s ,t ) and for determining for said one or more states a best predecessor state at the directly preceding sampling instant t , a state at said sampling instant identifying a sequence of n subsequent bits. The apparatus further comprises calculating means for (b) establishing ( ) the best path from the state at the said sampling instant t having the lowest optimum path metric value, back in time towards the sampling instant t via best predecessor states, established earlier for earlier sampling instants, to establish an optimum state at said sampling instant t . The apparatus further comprises the calculating means for (c) outputting at least one bit (x ) of said n bits of the sequence of bits corresponding to said established optimum state at said sampling instant t . The steps (a) to (c) are repeated for a subsequent sampling instant t . The apparatus is characterized in that mutually complementary sequences of n subsequent bits are allocated to the same state.

Detection apparatus

An arrangement for generating an error signal representing the differences between an input signal voltage level (xp , xn ) and an estimated value (rp, rn) for the input signal voltage level comprises first (T T ) and second (T T ) transconductors and a differencing circuit (T T T T ) which forms the modulus of the difference between the outputs of the transconductors. The error signal is converted into a probability signal by subtracting the error signal from a constant signal ( ) to produce a signal at the output ( ) which is a maximum when the input voltage level and estimated voltage level are equal.

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Romsey, United Kingdom

Simon Derek Bramwell