Detection apparatus

• US 6,678,862 B1
• Filed: 03/30/2001
• Issued: 01/13/2004
• Est. Priority Date: 08/02/1999
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Bramwell, Simon Derek, Coene, Willem Marie Julia Marcel, Otte, Rob, Bergmans, Johannes Wilhelmus Maria
• Primary Examiner(s): TU, CHRISTINE TRINH LE
• Application Number:
  US09/806,585
• Time in Patent Office: 1,019 Days
• Field of Search: 714/794, 714/795, 714/792, 714/796, 369/59.22, 369/47, 369/47.35, 375/341, 375/262, 375/263, 375/265
• US Class Current: 714/794
• CPC Class Codes: G11B 20/00 Signal processing not specific to the method of recording or reproducing; Circuits therefor
• CPC Class Codes: H03M 13/015 Simulation or testing of codes, e.g. bit error rate [BER] measurements
• CPC Class Codes: H03M 13/3961 Arrangements of methods for branch or transition metric calculation
• CPC Class Codes: H03M 13/41 using the Viterbi algorithm or Viterbi processors
• CPC Class Codes: H03M 13/4107 implementing add, compare, select [ACS] operations
• CPC Class Codes: H03M 13/4169 using traceback H03M13/4192 takes precedence
• CPC Class Codes: H03M 13/6343 Error control coding in combination with techniques for partial response channels, e.g. recording

Abstract

A partial response maximum likelihood (PRML) bit detection apparatus is disclosed for deriving a bit sequence (x_k) 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_k) of the information signal at said sampling instants. The apparatus also comprises calculating means (50, 70) for (a) calculating (50) at a sampling instant t_i for one or more of a plurality of states s_j (Sa, Sb, Sc) at said sampling instant, an optimum path metric value PM(s_j,t_i) and for determining for said one or more states a best predecessor state at the directly preceding sampling instant t_i−1, a state at said sampling instant identifying a sequence of n subsequent bits. The apparatus further comprises calculating means for (b) establishing (70) the best path from the state at the said sampling instant t_i having the lowest optimum path metric value, back in time towards the sampling instant t_i−N via best predecessor states, established earlier for earlier sampling instants, to establish an optimum state at said sampling instant t_i−N. The apparatus further comprises the calculating means for (c) outputting at least one bit (x_k−MB−1) of said n bits of the sequence of bits corresponding to said established optimum state at said sampling instant t_i−N. The steps (a) to (c) are repeated for a subsequent sampling instant t_i+1. The apparatus is characterized in that mutually complementary sequences of n subsequent bits are allocated to the same state.

Claims

1. A partial response maximum likelihood bit detection apparatus for deriving a bit sequence ({circumflex over (x)}_k) from an input information signal, comprising

an input for receiving the input information signal,

sampling means for sampling, at a predetermined sampling frequency, the input information signal at sampling instants t_i so as to obtain sample values (z_k) of the input information signal at said sampling instants t_i, said sampling frequency having a relationship with a bit frequency,

calculating means for

(a) calculating at a sampling instant t_i for one or more of a plurality of states s_j (Sa, Sb, Sc) at said sampling instant, an optimum path metric value PM(s_j,t_i) and for determining for said one or more states a best predecessor state at the directly preceding sampling instant t_i−

1, a state at said sampling instant identifying a sequence of n subsequent bits,

(b) establishing the best path from the state at the said sampling instant t_i having the lowest optimum path metric value, back in time towards the sampling instant t<sub>i−

N</sub> via best predecessor states, established earlier for earlier sampling instants, to establish an optimum state at said sampling instant t<sub>i−

N</sub>,

(c) outputting at least one bit (x<sub>k−

MB−

1</sub>) of said n bits of the sequence of bits corresponding to said established optimum state at said sampling instant t<sub>i−

N</sub>,

(d) repeating said steps (a) to (c) for a subsequent sampling instant t_i+1, characterized in that mutually complementary sequences of n subsequent bits are allocated to the same state.

2. A detection apparatus according to claim 1, characterized in that it is arranged for deriving a bit sequence ({circumflex over (x)}_k) from an input information signal according to a runlength limited code, n being equal to the minimum allowed runlength of said code.

3. A detection apparatus according to claim 2, characterized in that the path metric is a difference metric.

4. A detection apparatus according to claim 2, characterized in that the calculation of the path metric is based on an M-taps partial response, wherein M>

n+1 and in that the calculation includes local sequence feedback.

5. A detection apparatus according to claim 2, characterized in that the calculation of the path metric is based on an M-taps partial response, wherein M>

n+1 and in that the calculation includes threshold detection.

6. A detection apparatus according to claim 2, characterized in that the calculation of the path metric is based on an M-taps partial response, wherein M>

n+1 and in that the calculation includes runlength pushback detection.

7. A detection apparatus according to claim 1, characterized in that it is arranged for detecting a runlength limited signal having a minimum allowed runlength of 2 symbols.

8. A detection apparatus according to claim 1, characterized in that it is arranged for detecting a runlength limited signal having a minimum allowed runlength of 3 symbols.