US4481646A
Expired / Lapsed
US
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Method and apparatus for receiving a data signal modulated by means of a double sideband-quadrature carrier modulation technique
Assignee: International Business Machines Corp
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Filing: 1982-11-19
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Granted: 1984-11-06
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Expires: 2002-11-19
Abstract
Abstract A method and apparatus for receiving a data signal modulated by means of a double sideband-quadrature carrier modulation technique in which the received signal is sampled at a rate higher than the signaling rate 1/T, passed through a compensating filter, and applied to a processing system which provides the detected data. The compensating filter is such that the amplitudes of the components at f 1 =f c -1/2T and f 2 =f c +1/2T, where f c is the carrier, are equal. An initializer enables a filter coefficient to be determined during the turn-on time of the receiver. An adjusting device allows this coefficient to be continually adjusted. The invention can be used in data transmission systems whose channel has an asymmetric amplitude-frequency response curve.
Inventors
- 👤 Dominique Godard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:57
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/01
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
115 words
A method of receiving a data signal sent over a transmission channel by modulating a carrier by means of a DSB-QC modulation technique at a signaling rate of 1/T, comprising the steps of: sampling the signal received from said transmission channel, at a rate of 1/τ equal to a multiple of said signaling rate, 1/T; filtering the sampled signal such that the phase thereof is not altered and that the components at frequencies f 1 and f 2 of the filtered signal are substantially equal, with said frequencies f 1 and f 2 being defined as ##EQU13## where f c is the carrier frequency; and processing said filtered signal to derive the detected data therefrom.
Claim 2
Independent Claim
115 words
A method of receiving a data signal sent over a transmission channel by modulating a carrier by means of a DSB-QC modulation technique at a signaling rate of 1/T, comprising the steps of: sampling the signal received from said transmission channel, at a rate of 1/τ equal to a multiple of said signaling rate, 1/T; filtering the sampled signal such that the phase thereof is not altered and that the components at frequencies f 1 and f 2 of the filtered signal are substantially equal, with said frequencies f 1 and f 2 being defined as ##EQU13## where f c is the carrier frequency; and processing said filtered signal to derive the detected data therefrom.
Claim 3
Dependent Claim
75 words
The method of claim 1, wherein said filtering step is performed in accordance with the following transfer function G(f)=α(1+2β cos 2πfτ) where α is a coefficient representing the gain associated with the filtering process, and β is a coefficient whose value is substantially equal to ##EQU14## where R=A 2 /A 1 , with A 1 and A 2 being the respective amplitudes of the components at f 1 and f 2 of said received signal.
Claim 4
Dependent Claim
39 words
The method of claim 2, wherein the value of said coefficient α is substantially equal to ##EQU15## where K is a constant representing the desired amplitudes of the components at f 1 and f 2 of said filtered signal.
Claim 5
Dependent Claim
45 words
The method of claim 2, further including the step of adjusting said coefficient α in accordance with the relation β.sub.n+1 =β.sub.n -λ.sub.1 [|H(f.sub.1)|.sup.2 ·|G(f.sub.1)|.sup.2 -|H(f.sub.2)|.sup.2 ·|G(f.sub.2)|.sup.2 ] where λ 1 is a positive adjustment step parameter, and H(f) is the spectrum of said received signal.
Claim 6
Dependent Claim
114 words
The method of claim 4, wherein said step of adjusting the coefficient β includes the sub-steps of: passing through a first narrow-band filter the signal resulting from said step of filtering said sampled signal to derive therefrom its component at f 1 , said component at time nT being designated P n ; passing through a second narrow-band filter said signal resulting from said step of filtering said sampled signal to derive therefrom its component at f 2 , said component at time nT being designated g n ; and adjusting said coefficient β in accordance with the relation β.sub.n+1 =β.sub.n -λ.sub.2 [|p.sub.n |.sup.2 -|g.sub.n |.sup.2 ] λ 2 is a positive adjustment parameter.
Claim 7
Dependent Claim
70 words
The method of claim 2, further including the step of adjusting said coefficient α in accordance with the relation α.sub.n+1 =α.sub.n -λ.sub.3 [|H(f.sub.1)|.sup.2 ·|G(f.sub.1 |.sup.2 -K] where λ 3 is a positive adjustment step parameter, H(f) is the received signal spectrum, and K is a given constant representing the desired amplitude of the component at f 1 and f 2 of the signal resulting from said sampled signal filtering step.
Claim 8
Dependent Claim
94 words
The method of claim 6, wherein said step of adjusting said coefficient α includes the sub-steps of passing through a narrow-band filter the signal resulting from said step of filtering said sampled signal to derive therefrom its component at f 1 , said component at time nT being designated p n , and adjusting said coefficient α in accordance with the relation: α.sub.n+1 =α.sub.n -λ.sub.4 [|p.sub.n |.sup.2 -K/γ] where λ 4 is a positive adjustment step parameter, and γ is the gain associated with the process of passing the signal through said narrow-band filter.
Claim 9
Dependent Claim
70 words
The method of claim 2, further including the step of adjusting said coefficient α in accordance with the relation α.sub.n+1 =α.sub.n -λ.sub.5 [|H(f.sub.2)|.sup.2 ·|G(f.sub.2)|.sup.2 -K ] where λ 5 is a positive adjustment step parameter, H(f) is the received signal spectrum, and K is a given constant representing the desired amplitude of the components at f 1 and f 2 of the signal resulting from said sampled signal filtering step.
Claim 10
Dependent Claim
13 words
The method of claim 2, wherein said coefficient α is equal to 1.
Claim 11
Dependent Claim
133 words
The method of claim 2 for use in a system wherein the data signal is preceded by a synchronizing signal whose spectrum includes components at f c , f 1 and f 2 , further including the steps of: demodulating said filtered signal by means of a local carrier frequency equal to f c at a rate of 2/T; storing the samples of the demodulated signal; determining the signals Δ(nT)=y(nT)-y[(n+1)T ] Δ(nT+T/2)=y(nT+T/2)-y[(n+1)T+T/2 ] where y(nT) represents the demodulated signal at time nT, determining the signal Δ.sub.1 =Δ(nT)+j Δ(nT+T/2) Δ.sub.2 =Δ(nT)-j Δ(nT+T/2) determining the amplitude of signals Δ 1 and Δ 2 ; calculating the ratio, R, of the amplitude of signal Δ 1 to that of signal Δ 2 ; and determining coefficient β in accordance with the relation given in claim 2.
Claim 12
Dependent Claim
117 words
Apparatus for receiving a data signal sent over a transmission channel by modulating a carrier by means of a DSB-QC modulation technique at a signaling rate of 1/T, comprising: means for sampling the signal received from said transmission channel at a rate of 1/τ equal to a multiple of said signaling rate, 1/T; filter means for filtering the received signal such that the phase thereof is not altered and that the components at frequencies f 1 and f 2 of the filtered signal are substantially equal, with frequencies f 1 and f 2 being defined as ##EQU16## where f c is the carrier frequency; and means for processing said filtered signal to derive the detected data therefrom.
Claim 13
Dependent Claim
117 words
Apparatus for receiving a data signal sent over a transmission channel by modulating a carrier by means of a DSB-QC modulation technique at a signaling rate of 1/T, comprising: means for sampling the signal received from said transmission channel at a rate of 1/τ equal to a multiple of said signaling rate, 1/T; filter means for filtering the received signal such that the phase thereof is not altered and that the components at frequencies f 1 and f 2 of the filtered signal are substantially equal, with frequencies f 1 and f 2 being defined as ##EQU16## where f c is the carrier frequency; and means for processing said filtered signal to derive the detected data therefrom.
Claim 14
Dependent Claim
70 words
Apparatus according to claim 11, wherein said filter means has the following transfer function: G(f)=α(1+2βcos 2πfπ) where α is a coefficient representing the gain associated with said filter means, and β is a coefficient whose value is substantially equal to ##EQU17## where R=A 2 /A 1 , with A 1 and A 2 being the respective amplitudes of the components at f 1 and f 2 of said received signal.
Claim 15
Dependent Claim
39 words
Apparatus according to claim 12, wherein the value of said coefficient α is substantially equal to ##EQU18## where K is a constant representing the desired amplitude of the components at f 1 and f 2 of said filtered signal.
Claim 16
Dependent Claim
44 words
Apparatus according to claim 12, further including means for adjusting said coefficient β in accordance with the relation: β.sub.n+1 =β.sub.n -λ.sub.1 [|H(f.sub.1)|.sup.2 ·|G(f.sub.1)|.sup.2 -|H(f.sub.2)|.sup.2 ·|G(f.sub.2)|.sup.2 ] where λ 1 is a positive adjustment step parameter, and H(f) is the spectrum of said received signal.
Claim 17
Dependent Claim
121 words
Apparatus according to claim 14, wherein said means for adjusting said coefficient β includes: first narrow-band filter means for deriving the component at f 1 of the signal provided by said filter means, the output from said first narrow-band filter means being designated p n ; second narrow-band filter means for deriving the component at f 2 of the signal provided by said filter means, the output from said second narrow-band filter means being designated q n ; means for determining the quantity |p n | 2 -|q n | 2 ; and means for adjusting said coefficient β in accordance with the relation: β.sub.n+1 =β.sub.n -λ.sub.2 [|p.sub.n |.sup.2 -|q.sub.n |.sup.2 ] where λ 2 is a positive adjustment step parameter.
Claim 18
Dependent Claim
67 words
Apparatus according to claim 12, comprising means for adjusting said coefficient α in accordance with the relation α.sub.n+1 =α.sub.n -λ.sub.3 [|H(f.sub.1)|.sup.2 ·|G(f.sub.1 |.sup.2 -K ] where λ 3 is a positive adjustment step parameter, H(f) is the received signal spectrum, and K is a given constant representing the desired amplitude of the components at f 1 and f 2 of the signal supplied by said filter means.
Claim 19
Dependent Claim
92 words
Apparatus according to claim 16, wherein said means for adjusting said coefficient α includes: narrow-band filter means for deriving the component at f 1 of the signal provided by said filter means, the output from said narrow-band filter means being designated p n ; means for determining the quantity |p n | 2 -K/γ, where γ is the gain of said narrow-band filter means; and adjusting means for adjusting said coefficient α in accordance with the relation α.sub.n+1 =α.sub.n -λ.sub.4 [|p.sub.n |.sup.2 -K/γ] where λ 4 is a positive adjustment gain parameter.
Claim 20
Dependent Claim
65 words
Apparatus according to claim 12, comprising means for adjusting said coefficient α in accordance with the relation α.sub.n+1 =α.sub.n -λ.sub.5 [|H(f.sub.2)|.sup.2 ·|G(f.sub.1)|.sup.2 -K ] where λ 5 is a positive adjustment parameter, H(f) is the received signal spectrum, and K is a given constant representing the desired amplitude of the component at f 1 and f 2 of the signal supplied by said filter means.
Claim 21
Dependent Claim
157 words
Apparatus according to claim 12, as used in a system wherein the data signal is preceded by a synchronizing signal whose spectrum includes components at f c , f 1 and f 2 , further including: means for demodulating the signal provided by said filter means, using a local carrier frequency equal to f c at a rate of 2/T; means for storing samples of the demodulated signal; means for determining the signal Δ(nT)=y(nT)-y[(n+1)T] where y(nT) represents the demodulated signal at time nT, means (52, 54) for determining the signal: Δ(n+1)=y(nT+T/2)-y[(n+1)T+T/2] means for determining the signal: Δ.sub.1 =Δ(nT)+jΔ(nT+T/2) means for determining the signal: Δ.sub.2 =Δ(nT)-jΔ(nT+T/2) means for determining the amplitude of signal Δ 1 and Δ 2 ; means for determining the ratio, R, of the amplitude of signal Δ 1 to that of signal Δ 2 ; and means for determining the value of said coefficient β in accordance with the relation given in claim 12.
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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) | 1987-11-06 | 1988-05-07 | 1988-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-11-06 | 1992-05-07 | 1992-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-11-06 | 1996-05-07 | 1996-11-06 | $7700.00 | Window Closed / Lapsed |