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US4888557A
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Digital subharmonic sampling down-converter
Assignee: Lockheed Martin Corp
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Filing: 1989-04-10
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Granted: 1989-12-19
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Expires: 2009-04-10
Abstract
Abstract A digital subharmonic sampling converter, for use in an analog IF signal demodulator and the like, includes: an analog-to-digital converter (ADC) means receiving the IF analog signal for conversion to a digital data stream by sampling at a sampling rate frequency substantially equal to 4/(2n+1) times the IF signal frequency, where n is an integer greater than zero. A digital mixer means is used to convert the sampled data to baseband. The interleaved sequential in-phase I data words and quadrature-phase Q data words are then sorted into a pair of concurrent I and Q data word streams.
Inventors
- 👤 Charles M. Puckette, IV
- 👤 Gary J. Saulnier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 07:36
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/007; H03D3/009; H03D3/008; H03D7/00; H03D2200/00; H03D2200/0041; H03D2200/0047; H03D2200/005; H03D2200/006; H03D2200/0066; H03D2200/007; H03D2200/008; H03D2200/0082; H03D3/006
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
131 words
A digital subharmonic down-converter, receiving an analog IF signal for providing substantially simultaneous output streams of in-phase I data and quadrature-phased Q data words, comprises: ADC means for converting the analog IF signal, having a frequency f IF , to a stream of digital data samples taken at a sampling frequency f c ; digital mixer means for converting the digital data sample stream to a stream of baseband digital data words; sorter means for separating interleaved alternating ones of the baseband data words stream into sequential sorted pairs of an in-phase I data word and a quadrature-phase Q data word; and means for causing the ADC means sampling frequency f c to be a subharmonic of the IF frequency, with ##EQU2## where n is a selected integer greater than zero.
Claim 2
Dependent Claim
131 words
A digital subharmonic down-converter, receiving an analog IF signal for providing substantially simultaneous output streams of in-phase I data and quadrature-phased Q data words, comprises: ADC means for converting the analog IF signal, having a frequency f IF , to a stream of digital data samples taken at a sampling frequency f c ; digital mixer means for converting the digital data sample stream to a stream of baseband digital data words; sorter means for separating interleaved alternating ones of the baseband data words stream into sequential sorted pairs of an in-phase I data word and a quadrature-phase Q data word; and means for causing the ADC means sampling frequency f c to be a subharmonic of the IF frequency, with ##EQU2## where n is a selected integer greater than zero.
Claim 3
Dependent Claim
35 words
The down-converter of claim 1, wherein the IF signal has a maximum frequency F H and a minimum frequency F L and n is less than K=Int(f H /BW), where BW=(f H -f L ).
Claim 4
Dependent Claim
29 words
The down-converter of claim 2, further comprising means for compensating the sorted pairs of data words for at least one of quadrature misalignment offset and input signal DC bias.
Claim 5
Dependent Claim
9 words
The down-converter of claim 2, wherein n=1 and ##EQU3##
Claim 6
Dependent Claim
15 words
The down-converter of claim 4, wherein f IF is on the order of 10 MHz.
Claim 7
Dependent Claim
16 words
The down-converter of claim 5, wherein f IF is between about 4 and about 20 MHz.
Claim 8
Dependent Claim
9 words
The down-converter of claim 2, wherein n=2 and ##EQU4##
Claim 9
Dependent Claim
15 words
The down-converter of claim 7, wherein f IF is on the order of 10 MHz.
Claim 10
Dependent Claim
16 words
The down-converter of claim 8, wherein f IF is between about 4 and about 20 MHz.
References Cited (Backward Citations)
US4647864A
Cited
US4755761A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-12-18 | 1993-06-19 | 1993-12-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-18 | 1997-06-19 | 1997-12-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-18 | 2001-06-19 | 2001-12-19 | $7700.00 | Window Closed / Lapsed |