US4965536A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Quadrature amplitude modulation system using digital filters
Assignee: NEC Corp
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Filing: 1989-05-30
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Granted: 1990-10-23
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Expires: 2009-05-30
Abstract
Abstract A modulating device applicable to a digital radio communications system which is adaptable to a 16 or greater multi-level QAM modulation system. The device has two multi-input digital filters to implement the role of cosine roll-off filters. A logic circuit precedes the digital filters to logically manipulate n-bit data streams except for m bits (m<n) thereof which should be modulated, in a predetermined manner. The logic circuit is capable of correcting deviations of signal points of a QAM wave or changing the contour of signal constellation to a circular contour or the like, as desired.
Inventors
- 👤 Yasuharu Yoshida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 07:14
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/02; H04L25/03; H04L25/03006; H04L25/03012; H04L25/03114; H04L25/03133; H04L27/00; H04L27/32; H04L27/34; H04L27/36; H04L27/362; H04L27/364
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
189 words
A modulating device comprising: two digital filters each for digitally processing input parallel n-bit data streams which include m (an integer equal to or smaller than n) data signals to thereby produce G (larger than m) data signal streams; two digital-to-analog converters each being associated with a respective one of said two digital filters and, in response to outputs of said associated digital filters, individually producing multi-level signals P and Q; and a quadraphase modulator for producing a quadrature amplitude modulated wave in response to the multi-level signals P and Q; wherein said digital filters each comprises a plurality of n-bit shift registers, each of said n-bit shift registers being operative to receive said n-bit data streams and output B-bit (equal to or larger than m) data streams; a plurality of multipliers for multiplying said B-bit data streams by a fixed weighting coefficient, each of said weighting coefficients having A (larger than m) bits and each of said multipliers being connected to an output of a respective one of said n-bit shift registers; and an adder for adding outputs of said multipliers to produce said G data signal streams.
Claim 2
Dependent Claim
189 words
A modulating device comprising: two digital filters each for digitally processing input parallel n-bit data streams which include m (an integer equal to or smaller than n) data signals to thereby produce G (larger than m) data signal streams; two digital-to-analog converters each being associated with a respective one of said two digital filters and, in response to outputs of said associated digital filters, individually producing multi-level signals P and Q; and a quadraphase modulator for producing a quadrature amplitude modulated wave in response to the multi-level signals P and Q; wherein said digital filters each comprises a plurality of n-bit shift registers, each of said n-bit shift registers being operative to receive said n-bit data streams and output B-bit (equal to or larger than m) data streams; a plurality of multipliers for multiplying said B-bit data streams by a fixed weighting coefficient, each of said weighting coefficients having A (larger than m) bits and each of said multipliers being connected to an output of a respective one of said n-bit shift registers; and an adder for adding outputs of said multipliers to produce said G data signal streams.
Claim 3
Dependent Claim
52 words
A device as claimed in claim 1, further comprising a logic circuit for receiving the m input data signal streams and feeding to each of said two digital filters parallel n-bit (larger than m) data streams by applying a predetermined logical manipulation to parallel n bits of the input data signal streams.
References Cited (Backward Citations)
US4812786A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-10-22 | 1994-04-23 | 1994-10-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-10-22 | 1998-04-23 | 1998-10-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-10-22 | 2002-04-23 | 2002-10-23 | $7700.00 | Window Closed / Lapsed |