US5319676A
Expired / Lapsed
US
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Digital pre-modulation filter
Assignee: US Philips Corp
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Filing: 1988-12-21
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Granted: 1994-06-07
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Expires: 2008-12-21
Abstract
Abstract A digital pre-modulation filter with a finite impulse response having the value k(t)=h(t)·w(t), where h(t) represents an impulse response of the type that is customary for a modulator, for generating in response to data signals an angle-modulated carrier signal having a substantially constant amplitude, and w(t) represents a window function by which the impulse response of the pre-modulation filter is truncated softly. It turns out to be possible to reduce the disturbing effects with respect to the power spectrum caused by such a soft truncation and cancel them with respect to the phase of the angle-modulated carrier signal. Thereto, according to the invention the impulse response k(t)=A{g(t)+x(t)}·w(t) is selected where A is a correction factor which is usually equal to one, g(t) is the untruncated impulse response of the filter, x(t) is a constant c c or a time-dependent correction function which in a preferred embodiment has such a variation that for example ##EQU1## for any integer value of i.
Inventors
- 👤 Gerrit Van Dasler
- 👤 Hendrikus L. Verstappen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 11:36
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/02; H04L25/03; H04L25/03828; H04L25/03834; H04L27/00; H04L27/18; H04L27/20; H04L27/2003; H04L27/2007; H04L27/2017
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
145 words
A digital pre-modulation filter comprising: a) means for receiving an input signal; b) filter means for forming an output signal from the input signal in accordance with an overall impulse response k(t), where k(t) is defined as follows: k(t)=A·{g(t)+x(t)}·w(t), where A is a correction factor, g(t) is the untruncated impulse response of the filter, x(t) represents a continuous correction function operating over p symbol intervals, w(t) represents a window function determining a finite width of the overall impulse response; k(t) is a continuous function, ##EQU19## where r is an arbitrary integer, w(t)=1 for |t|<(i+1/2)T, where i can be 0, 1, 2, . . . , w(t) is a continuous function for (i+1/2)T≦|t|≦(i+j)T w(t)=0 for |t|>(i+j)T, where j=(2p+1)/2; p is an integer greater than zero representing a number of symbol intervals; and T is the symbol interval; and c) output means for supplying the output signal.
Claim 2
Dependent Claim
145 words
A digital pre-modulation filter comprising: a) means for receiving an input signal; b) filter means for forming an output signal from the input signal in accordance with an overall impulse response k(t), where k(t) is defined as follows: k(t)=A·{g(t)+x(t)}·w(t), where A is a correction factor, g(t) is the untruncated impulse response of the filter, x(t) represents a continuous correction function operating over p symbol intervals, w(t) represents a window function determining a finite width of the overall impulse response; k(t) is a continuous function, ##EQU19## where r is an arbitrary integer, w(t)=1 for |t|<(i+1/2)T, where i can be 0, 1, 2, . . . , w(t) is a continuous function for (i+1/2)T≦|t|≦(i+j)T w(t)=0 for |t|>(i+j)T, where j=(2p+1)/2; p is an integer greater than zero representing a number of symbol intervals; and T is the symbol interval; and c) output means for supplying the output signal.
Claim 3
Dependent Claim
32 words
A digital pre-modulation filter as claimed in claim 1, characterized in that the correction function x(t) is at time independent constant c c , while the following holds for this constant: ##EQU20##
Claim 4
Dependent Claim
69 words
A digital pre-modulation filter as claimed in claim 1, wherein A=1, and the correction function x(t) is time-dependent and for each interval l, where l represents the time interval (i+l-1/2)T≦|t|≦(i+l+1/2)T, and where x(t) is equal to ##EQU21## where c l represents a constant for each interval l and n represents a positive integer, the constant c l being determined for each interval l according to the following equation ##EQU22##
Claim 5
Dependent Claim
90 words
The filter of claim 1 wherein the filter means comprises i) a first filter for filtering the input signal and having an impulse response g(t); ii) a second filter arranged in parallel with the first filter and having an impulse response x(t); iii) means for adding output signals from the first and second filters; iv) means for scaling an output signal from the adding means by a factor of A; and v) means for windowing an output signal from the scaling means the windowing means having an impulse response w(t).
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-06-06 | 1997-12-06 | 1998-06-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-06-06 | 2001-12-06 | 2002-06-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-06-06 | 2005-12-06 | 2006-06-07 | $7700.00 | Window Closed / Lapsed |