Approximate linear FM synchronization symbols for a bandwidth configurable OFDM modem
AssigneeEdgewater Computer Systems, Inc.
InventorJohn Fanson
Life of this patent
Estimating the term…
Abstract
A communications system permits bandwidth configurability using a linear frequency modulated (LFM) waveform for transmitter/receiver synchronization. The system permits enhancement of MIL-STD-1553 data buses, and is likewise applicable to any bandwidth-configurable modem.
Claims18
A method of generating synchronization symbols for a bandwidth configurable modem, comprising:
- using the equation
- x
- ′
-
- (
- n
- )
- =
- ⅇ
- jπ
-
-
- vn
- 2
- N
- 2
- +
- j2π
-
-
- k
- 0
-
- n
- N
- where:
- x′(n) is the discrete time LFM waveform;
- N is the length of the waveform in samples;
- n=0 to N-1;
- v is the number of frequency bins over which the signal is swept;
- and k0 is the sub-carrier index corresponding to the start of the sweep;
- to generate the synchronization symbols in a time domain.
A method of generating synchronization symbols for a bandwidth configurable modem, comprising:
- using the approximation equation:
- X
- ′
-
- (
- k
- +
- k
- 0
- )
- mod
-
-
- N
- ≈
- X
- ″
-
- (
- k
- +
- k
- 0
- )
- mod
-
-
- N
- =
- {
- N
- v
-
- ⅇ
- -
- j
-
- π
- v
-
- k
- 2
- +
- j
-
- π
- 4
- k
- =
- 0
- ,
- 1
- ,
- …
-
- ,
- v
- -
- 1
- 0
- otherwise
- where:
- N is the number of sub-carrier frequencies;
- k=0 to N-1;
- v is the number of frequency bins over which the signal is swept;
- and k0 is the index of the sub-carrier corresponding to the start of the sweep;
- to generate the synchronization symbols in a frequency domain;
- and
- using an inverse fast Fourier transform (IFFT) to convert sub-carrier signals to a time domain before the waveform is transmitted.
A bandwidth-configurable modem adapted to generate synchronization symbols comprising:
- logic circuits that generate the synchronization symbols in a time domain using the equation
- x
- ′
-
- (
- n
- )
- =
- ⅇ
- jπ
-
-
- vn
- 2
- N
- 2
- +
- j2π
-
-
- k
- 0
-
- n
- N
- where:
- N is the length of the waveform in samples;
- n=0 to N-1;
- v is the number of frequency bins over which the signal is swept;
- and k0 is the index of the sub-carrier corresponding to the start of the sweep.
A bandwidth-configurable modem adapted to generate synchronization symbols comprising:
- logic circuits that generate the synchronization symbols in frequency domain by using the approximation equation:
- X
- ′
-
- (
- k
- +
- k
- 0
- )
- mod
-
-
- N
- ≈
- X
- ″
-
- (
- k
- +
- k
- 0
- )
- mod
-
-
- N
- =
- {
- N
- v
-
- ⅇ
- -
- j
-
- π
- v
-
- k
- 2
- +
- j
-
- π
- 4
- k
- =
- 0
- ,
- 1
- ,
- ⋯
-
- ,
- v
- -
- 1
- 0
- otherwise
- where:
- N is the number of sub-carrier frequencies;
- k=0 to N-1;
- v is the number of frequency bins over which the signal is swept;
- and k0 is the index of the sub-carrier corresponding to the start of the sweep;
- and
- logic circuits for performing an inverse fast Fourier transform (IFFT) for converting sub-carrier signals to a time domain before the waveform is transmitted.
Dependencies are inferred from the claim text.