FSK demodulator

Claim 2

A detector (100) for an FM-modulated IF signal having a frequency deviation Δω, comprising: splitting means for providing the IF signal to a first input (105) of a first product detector (109) and to a first input (107) of a second product detector (111), oscillator means (127) for providing a signal at the IF frequency to the input of a 90° phase shift means (115) and to the input of a 0° or 360° phase shift means (113), the 90° phase shift means output signal coupled to a second input of said second product detector (111), the 0° or 360° phase shift means output signal coupled to a second input of said first product detector (109), said first product detector output (171) coupled to the input (121) of a time-delay means (131) having a time-delay Δt that is based on the quotient (90°/Δω), the time-delay means output (137) coupled to a first input of a third product detector (135), said second product detector output (173) coupled to a second input (123) of said third product detector (135).

Claim 3

The detector of claim 1, said oscillator means including a crystal-controlled oscillator.

Claim 4

The detector of claim 2, said oscillator means including a buffer means connected in series with said oscillator.

Claim 5

A detector (200) for an FM-modulated IF signal having a frequency deviation Δω, comprising: splitting means (203) for providing the IF signal to a first input (205) of a first product detector (209) and to a first input (207) of a second product detector (211), oscillator means (227) for providing a signal at the IF frequency to the input of a 90° phase shift means (215) and to the input of a 0° or 360° phase shift means (213), the 90° phase shift means (215) output signal coupled to a second input of said second product detector (211), the 0° or 360° phase shift means (213) output signal coupled to a second input of said first product detector (209), said first product detector (209) output coupled to the input (221) of a time-delay means (231) having a time-delay Δt that is based on the quotient (90°/Δω), the time-delay means output (237) coupled to a first input of a third product detector (237), said second product detector (211) output coupled to a second input of said third product detector (235), said third product detector output (269) coupled to a converter means (239, 241, 245) for sampling said output at the symbol rate, and for providing a digital form of the sampled signal to a processor means, said processor means (249, 251, 253, 257, 259) having means for computing the desired value of said time-delay means, and means (263, 233) coupled to said time-delay means (231) for adjusting said setting to said desired value.

Claim 6

A detector (200) for an FM-modulated IF signal having a frequency deviation Δω, comprising: splitting means (203) for providing the IF signal to a first input (205) of a first product detector (209) and to a first input (207) of a second product detector (211), oscillator means (227) for providing a signal at the IF frequency to the input of a 90° phase shift means (215) and to the input of a 0° or 360° phase shift means (213), the 90° phase shift means (215) output signal coupled to a second input of said second product detector (211), the 0° or 360° phase shift means (213) output signal coupled to a second input of said first product detector (209), said first product detector (209) output coupled to the input (221) of a time-delay means (231) having a time-delay Δt that is based on the quotient (90°/Δω), the time-delay means output (237) coupled to a first input of a third product detector (237), said second product detector (211) output coupled to a second input of said third product detector (235), said third product detector output (269) coupled to a converter means (239, 241, 245) for sampling said output at the symbol rate, and for providing a digital form of the sampled signal to a processor means, said processor means (249, 251, 253, 257, 259) having means for computing the desired value of said time-delay means, and means (263, 233) coupled to said time-delay means (231) for adjusting said setting to said desired value.

Claim 7

The detector of claim 4, said oscillator means including a crystal-controlled oscillator (229).

Claim 8

The detector of claim 5, said oscillator means including a buffer means (225) connected in series with said oscillator.

Claim 9

The detector of claim 6, said converter means including an A/D converter (245).

Claim 10

The detector of claim 7, said time-delay means including a multiplicity of taps (275) for adjusting the setting.

Claim 11

The detector of claim 8, said processor means including a multiplicity (N) of bit lines (247) coupled from said A/D converter (245) to the inputs of an addressable EPROM (249), said EPROM's outputs coupled to a digital comparator (259) arranged to compare said outputs with an expected pattern (257), the output (261) of said comparator coupled to an up/down counter (263), the outputs (265) of said up/down counter coupled to said multiplicity of taps (275) of said time-delay means (231).

Claim 14

An FSK demodulator for detecting an FM-modulated IF signal having a frequency deviation Δω, comprising: means for providing a detection signal at the IF center frequency of the received signal; means for providing a first version of said detection signal that is phase-shifted by 90°; means for providing a second version of said detection signal that is phase-shifted by 0° or 360°; means for forming a first signal based on the product of said first version and said IF signal; means for forming a second signal based on the product of said second version and said IF signal; means for time-delaying said first signal by a Δ based on the quotient (90°/Δω), thereby forming a delayed first signal; means for forming an output signal based on the product of said delayed first signal and said second signal.

Claim 15

An FSK demodulator for detecting an FM-modulated IF signal having a frequency deviation Δω, comprising: means for providing a detection signal at the IF center frequency of the received signal; means for providing a first version of said detection signal that is phase-shifted by 90°; means for providing a second version of said detection signal that is phase-shifted by 0° or 360°; means for forming a first signal based on the product of said first version and said IF signal; means for forming a second signal based on the product of said second version and said IF signal; means for time-delaying said first signal by a Δ based on the quotient (90°/Δω), thereby forming a delayed first signal; means for forming an output signal based on the product of said delayed first signal and said second signal.