Single sideband signal demodulator
First Claim
1. A demodulator for demodulating a received signal that can be represented by the equation Y(t)=X(t) cos (ω
-
c t+φ
)±
X(t) sin (ω
c t+φ
) where ω
c is the carrier frequency and φ
is a constant phase shift, comprising;
means for converting the received signal y(t) into a first baseband signal Y(nts) where n is an integer variable and ts is a sampling period;
means for converting the received signal Y(t) into a second baseband signal Y(nts);
where n is an integer variable and ts is a sampling period;
means for performing a Hilbert'"'"'s transform on the second baseband signal Y(nts) to obtain a quadrature second baseband signal Y(nts);
means for adding the first baseband signal Y(nts) to the quadrature second baseband signal Y(nts) to obtain a lower sideband signal; and
means for subtracting the quadrature second baseband signal Y(nts) from the first baseband signal Y(nts) to obtain an upper sideband signal.
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Abstract
A single sideband signal can be demodulated by using sampled data techniques. An intermediate frequency (IF) radio signal is split into two branches and is sampled by two sample and hold devices; each sample and hold device operates at a rate that is not only a submultiple of the carrier frequency, but is also at least twice the information bandwidth. Prior to, or during sampling of one branch (the quadrature branch), a Hilbert'"'"'s transform is performed upon the IF signal which results in the output of the two sample and hold devices being in phase quadrature. A phase shift of 90°, using a baseband finite impulse response Hilbert'"'"'s transform filter, is performed upon the output signal of the quadrature branch'"'"'s sample and hold device. The sum of the inphase sampled signal and the filtered quadrature phase sampled signal produces the demodulated lower sideband while the difference between the two produces the demodulated upper sideband. There are two basic examples shown of single sideband demodulation through the use of sampled data techniques; in addition, there are several examples of implementing the Hilbert'"'"'s Transformer.
107 Citations
13 Claims
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1. A demodulator for demodulating a received signal that can be represented by the equation Y(t)=X(t) cos (ω
-
c t+φ
)±
X(t) sin (ω
c t+φ
) where ω
c is the carrier frequency and φ
is a constant phase shift, comprising;means for converting the received signal y(t) into a first baseband signal Y(nts) where n is an integer variable and ts is a sampling period; means for converting the received signal Y(t) into a second baseband signal Y(nts);
where n is an integer variable and ts is a sampling period;means for performing a Hilbert'"'"'s transform on the second baseband signal Y(nts) to obtain a quadrature second baseband signal Y(nts); means for adding the first baseband signal Y(nts) to the quadrature second baseband signal Y(nts) to obtain a lower sideband signal; and means for subtracting the quadrature second baseband signal Y(nts) from the first baseband signal Y(nts) to obtain an upper sideband signal. - View Dependent Claims (2, 3, 4, 5, 6)
-
c t+φ
-
7. In combination, a single sideband radio receiver for receiving a signal that can be represented by the equation Y(t)=X(t) cos (ω
-
c t+φ
)∓
X(t) sin (ω
c t+φ
) where ω
c is the carrier frequency and φ
is a constant phase shift including, in cascade arrangement, an antenna, a filter and RF amplifier means, a mixer means, IF filter and amplifier means, a single sideband demodulator means, and a local oscillator means connected to said mixer means, wherein said single sideband demodulator means, comprises;means for converting the received signal Y(t) into a first baseband signal Y(nts) where n is an integer variable and ts is an sampling period; means for converting the received signal Y(t) into a second baseband signal Y(nts);
where n is an integer variable and ts is an sampling period;means for performing a Hilbert'"'"'s transform on the second baseband signal Y(nts) to obtain a quadrature second baseband signal Y(nts); means for adding the first baseband signal Y(nts) to the quadrature second baseband signal Y(nts) to obtain an lower sideband signal; and means for subtracting the quadrature second baseband signal Y(nts) from the first baseband signal Y(nts) to obtain an upper sideband signal. - View Dependent Claims (8, 9, 10, 11, 12)
-
c t+φ
-
13. A method for demodulating a signal that can be represented by the equation Y(t)=X(t) cos (ω
-
c t+φ
)∓
X(t) sin (ω
c t+φ
) where ω
c is the carrier frequency and φ
is a constant phase shift, comprising;converting the received signal y(t) into a first baseband signal Y(nts) where n is an integer variable and ts is an sampling period; converting the received signal Y(t) into a second baseband signal Y(nts);
where n is an integer variable and ts is an sampling period;performing a Hilbert'"'"'s transform on the second baseband signal Y(nts) to obtain a quadrature second baseband signal Y(nts); adding the first baseband signal Y(nts) to the quadrature second baseband signal Y(nts) to obtain an lower sideband signal; and subtracting the quadrature second baseband signal, Y(nts) from the first baseband signal Y(nts) to obtain an upper sideband signal.
-
c t+φ
Specification
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- Resources
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Current AssigneeRockwell International Corporation
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Original AssigneeRockwell International Corporation
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InventorsMarston, Robert K., Massad, Khalil E., Maixner, Richard C.
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Primary Examiner(s)Bookbinder, Marc E.
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Application NumberUS05/919,021Time in Patent Office911 DaysField of Search325/330, 325/50, 325/449, 329/50, 329/145, 328/133, 328/37, 328/55, 331/2, 455/47, 455/203, 455/46, 455/202US Class Current455/202CPC Class CodesH03D 1/24 for demodulation of signals...
