Near direct conversion receiver and method for equalizing amplitude and phase therein
First Claim
Patent Images
1. A receiver including:
- (a) a downconversion means for receiving a radio frequency (RF) signal and downconverting said RF signal to an in-phase intermediate frequency (IF) signal (IFI) and a quadrature-phase IF signal (IFQ); and
(b) processing means, operatively coupled to said downconversion means, and including a pair of analog-to-digital converters for digitizing the IFI and IFQ signals, and a digital signal processor (DSP), operatively coupled to said analog-to-digital converters, for correcting the digitized IF signals (IFI, IFQ) so that they are substantially equal in magnitude and substantially 90°
out of phase, and then downconverting said digitized IF signals to baseband signals (I, Q), wherein said DSP includes phase correcting means including;
(1) a phase shifter for phase shifting at least one of said IF signals and providing as a phase shifter output phase shifted representations of said at least one of said IF signals;
(2) a multiplier, operatively coupled to said phase shifter, for multiplying said IF signals and providing as a multiplier output product signals representing products of said IF signals; and
(3) an integrator, operatively coupled to said multiplier and said phase shifter, for summing said product signals, providing sum signals representing cumulative sums of said product signals, and feeding said sum signals back to said phase shifter;
wherein said phase shifter shifts the phase of said at least one of said IF signals so as to minimize any error in the quadrature-phase relationship between the IFI and IFQ signals,wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal.
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Abstract
A low cost, high performance near direct conversion FM receiver having a single local oscillator is configured to equalize in-phase and quadrature-phase IF signals. The receiver includes a downconverter and a processor. The downconverter receives an RF signal and downconverts the RF signal to an in-phase IF signal (IFI) and a quadrature-phase IF signal (IFQ). The processor digitizes IFI and IFQ, corrects these signals so that they are substantially equal in magnitude and substantially 90° out of phase, and then downconverts the IF signals to baseband signals (I, Q).
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Citations
34 Claims
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1. A receiver including:
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(a) a downconversion means for receiving a radio frequency (RF) signal and downconverting said RF signal to an in-phase intermediate frequency (IF) signal (IFI) and a quadrature-phase IF signal (IFQ); and (b) processing means, operatively coupled to said downconversion means, and including a pair of analog-to-digital converters for digitizing the IFI and IFQ signals, and a digital signal processor (DSP), operatively coupled to said analog-to-digital converters, for correcting the digitized IF signals (IFI, IFQ) so that they are substantially equal in magnitude and substantially 90°
out of phase, and then downconverting said digitized IF signals to baseband signals (I, Q), wherein said DSP includes phase correcting means including;(1) a phase shifter for phase shifting at least one of said IF signals and providing as a phase shifter output phase shifted representations of said at least one of said IF signals; (2) a multiplier, operatively coupled to said phase shifter, for multiplying said IF signals and providing as a multiplier output product signals representing products of said IF signals; and (3) an integrator, operatively coupled to said multiplier and said phase shifter, for summing said product signals, providing sum signals representing cumulative sums of said product signals, and feeding said sum signals back to said phase shifter; wherein said phase shifter shifts the phase of said at least one of said IF signals so as to minimize any error in the quadrature-phase relationship between the IFI and IFQ signals, wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A receiver including:
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(a) a downconversion means for receiving a radio frequency (RF) signal and downconverting said RF signal to an in-phase intermediate frequency (IF) signal (IFI) and a quadrature-phase IF signal (IFQ); and (b) processing means, operatively coupled to said downconversion means, and including a pair of analog-to-digital converters for digitizing the IFI and IQ signals, and a digital signal processor (DSP), operatively coupled to said analog-to-digital converters, for correcting the digitized IF signals (IFI, IFQ) so that they are substantially equal in magnitude and substantially 90°
out of phase, and then downconverting said digitized IF signals to baseband signals (I, Q), wherein said DSP comprises an amplitude correcting means including;(1) scaling means for adjusting the magnitude of at least one of said IF signals; and (2) summing means, operatively coupled to said scaling means, for providing a sum signal representative of a sum of a difference, if any, in the magnitudes of said IF signals, and feeding said sum signal back to said scaling means; wherein said scaling means adjusts the magnitude of said at least one of said IF signals so as to minimize any difference in the magnitudes of said IF signals, and wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal.
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8. A receiver, including:
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(a) a downconversion means for receiving a radio frequency (RF) signal and downconverting said RF signal to an in-phase intermediate frequency (IF) signal (IFI) and a quadrature-phase IF signal (IFQ); and (b) processing means, operatively coupled to said downconversion means, for digitizing said IF signals (IFI, IFQ), correcting said IF signals so that they are substantially equal in magnitude and substantially 90°
out of phase, and then downconverting said IF signals to baseband signals (I, Q), wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal,wherein said receiver is constructed and arranged to receive frequency modulated (FM) signals, and further comprising an FM demodulator or discriminator for providing a demodulated baseband signal (FM) according to the equation;
space="preserve" listing-type="equation">FM=IdQ-QdI/I.sup.2 +Q.sup.2.
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9. A receiver, including:
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(a) a downconversion means for receiving a radio frequency (RF) signal and downconverting said RF signal to an in-phase intermediate frequency (IF) signal (IFI) and a quadrature-phase IF signal (IFQ); and (b) processing means, operatively coupled to said downconversion means, and including a pair of analog-to-digital converters for digitizing the IFI and IFQ signals, and a digital signal processor (DSP), operatively coupled to said analog-to-digital converters, for correcting the digitized IF signals (IFI, IFQ) so that they are substantially equal in magnitude and substantially 90°
out of phase, and then downconverting said digitized IF signals to baseband signals (I, Q), wherein said DSP comprises;(1) phase correcting means comprising a phase shifter for phase shifting at least one of said IF signals and providing as a phase shifter output phase shifted representations of said at least one of said IF signals;
a multiplier, operatively coupled to said phase shifter, for multiplying said IF signals and providing as a multiplier output product signals representing products of said IF signals; and
an integrator, operatively coupled to said multiplier and said phase shifter, for summing said product signals, providing sum signals representing cumulative sums of said product signals, and feeding said sum signals back to said phase shifter;
wherein said phase shifter shifts the phase of said at least one of said IF signals so as to minimize any error in the quadrature-phase relationship between the IFI and IFQ signals; and(2) amplitude correcting means comprising scaling means for adjusting the magnitude of at least one of said IF signals; and
summing means, operatively coupled to said scaling means, for providing a sum signal representative of a sum of a difference, if any, in the magnitudes of said IF signals, and feeding said sum signal back to said scaling means;
wherein said scaling means adjusts the magnitude of said at least one of said IF signals so as to minimize any difference in the magnitudes of said IF signals;wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal. - View Dependent Claims (10, 11)
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12. A method for receiving and downconverting a radio frequency (RF) signal, comprising the steps of:
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(a) receiving said RF signal; (b) downconverting said RF signal to an in-phase intermediate frequency (IF) signal (IFI) and a quadrature-phase IF signal (IFQ); (c) digitizing said IF signals (IFI, IFQ); (d) correcting said IF signals so that they are substantially equal in magnitude and substantially 90°
out of phase by;(1) phase shifting at least one of said IF signals and providing phase shifted representations of said at least one of said IF signals; (2) multiplying said IF signals and providing product signals representing products of said IF signals; and (3) summing said product signals and providing sum signals representing cumulative sums of said product signals, and employing said sum signals as feedback signals in said phase shifting step;
wherein said phase shifting step shifts the phase of said at least one of said IF signals so as to minimize any error in the quadrature-phase relationship between the IFI and IFQ signals;(e) downconverting said IF signals to baseband signals (I, Q), wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for receiving and downconverting a radio frequency (RF) signal, comprising the steps of:
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(a) receiving said RF signal; (b) downconverting said RF signal to an in-phase intermediate frequency (IF) signal (IFI) and a quadrature-phase IF signal (IFQ); (c) digitizing said IF signals (IFI, IQ); (d) correcting said IF signals so that they are substantially equal in magnitude and substantially 90°
out of phase by;(1) adjusting the magnitude of at least one of said IF signals; and (2) providing a sum signal representative of a sum of a difference, if any, in the magnitudes of said IF signals, and employing said sum signal as a feedback signal in said adjusting step;
wherein said adjusting step adjusts the magnitude of said at least one of said IF signals so as to minimize any difference in the magnitudes of said IF signals;(e) downconverting said IF signals to baseband signals (I, Q), wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal.
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24. A transceiver for receiving first radio frequency (RF) signals in a first set of frequency channels and transmitting second RF signals in a second set of frequency channels without the use of a diplexer, comprising:
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(a) a receiver comprising downconversion means for downconverting said first RF signals to in-phase intermediate frequency (IF) signals (IFI) and quadrature-phase IF signals (IFQ);
analog-to-digital conversion means for digitizing said IF signals; and
processing means including a digital signal processor (DSP), operatively coupled to said analog-to-digital conversion means, for correcting the digitized IF signals (IFI, IFQ) so that they are substantially equal in magnitude and substantially 90°
out of phase and then downconverting said digitized IF signals to baseband signals (I, Q), wherein said DSP comprises phase correcting means including;(1) a phase shifter for phase shifting at least one of said IF signals and providing as a phase shifter output phase shifted representations of said at least one of said IF signals; (2) a multiplier, operatively coupled to said phase shifter, for multiplying said IF signals and providing as a multiplier output product signals representing products of said IF signals; and (3) an integrator, operatively coupled to said multiplier and said phase shifter, for summing said product signals, providing sum signals representing cumulative sums of said product signals, and feeding said sum signals back to said phase shifter; wherein said phase shifter shifts the phase of said at least one of said IF signals so as to minimize any error in the quadrature-phase relationship between IFI and IFQ ; (b) a transmitter comprising means for upconverting second baseband signals to said second RF signals; (c) a synthesizer operatively coupled to said receiver and transmitter for providing a downconversion local oscillator (LO) signal to said receiver and an upconversion LO signal to said transmitter; (d) a first antenna operatively coupled to said receiver for receiving said first RF signals; and (e) a second antenna operatively coupled to said transmitter for transmitting said second RF signals, wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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31. A transceiver, for receiving first radio frequency (RF) signals in a first set of frequency channels and transmitting second RF signals in a second set of frequency channels without the use of a diplexer, including:
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(a) a receiver comprising downconversion means for downconverting said first RF signals to in-phase intermediate frequency (IF) signals (IFI) and quadrature-phase IF signals (IFQ);
analog-to-digital conversion means for digitizing said IF signals; and
processing means including a digital signal processor (DSP), operatively coupled to said analog-to-digital conversion means, for correcting the digitized IF signals (IFI, IQ) so that they are substantially equal in magnitude and substantially 90°
out of phase, and then downconverting said digitized IF signals to baseband signals (I, Q), wherein said DSP comprises an amplitude correcting means including;(1) scaling means, for adjusting the magnitude of at least one of said IF signals; and (2) summing means, operatively coupled to said scaling means, for providing a sum signal representative of a sum of a difference, if any, in the magnitudes of said IF signals, and feeding said sum signal back to said scaling means; wherein said scaling means adjusts the magnitude of said at least one of said IF signals so as to minimize any difference in the magnitude of said IF signals; (b) a transmitter comprising means for upconverting second baseband signals to said second RF signals; (c) a synthesizer operatively coupled to said receiver and transmitter for providing a downconversion local oscillator (LO) signal to said receiver and an upconversion LO signal to said transmitter; (d) a first antenna operatively coupled to said receiver for receiving said first RF signals; and (e) a second antenna operatively coupled to said transmitter for transmitting said second RF signals.
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32. A transceiver for receiving first radio frequency (RF) signals in a first set of frequency channels and transmitting second RF signals in a second set of frequency channels without the use of a diplexer, comprising:
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(a) a receiver comprising downconversion means for downconverting said first RF signals to in-phase intermediate frequency (IF) signals (IFI) and quadrature-phase IF signals (IFQ);
analog-to-digital conversion means for digitizing said IF signals; and
processing means including a digital signal processor (DSP), operatively coupled to said analog-to-digital conversion means, for correcting the digitized IF signals (IFI, IQ) so that they are substantially equal in magnitude and substantially 90°
out of phase, and then downconverting said digitized IF signals to baseband signals (I, Q), wherein said DSP includes;(1) phase correcting means comprising a phase shifter for phase shifting at least one of said IF signals and providing as a phase shifter output phase shifted representations of said at least one of said IF signals;
a multiplier, operatively coupled to said phase shifter, for multiplying said IF signals and providing as a multiplier output product signals representing products of said IF signals; and
an integrator, operatively coupled to said multiplier and said phase shifter, for summing said product signals, providing sum signals representing cumulative sums of said product signals, and feeding said sum signals back to said phase shifter;
wherein said phase shifter shifts the phase of said at least one of said IF signals so as to minimize any error in the quadrature-phase relationship between IFI and IFQ ; and(2) amplitude correcting means comprising scaling means for adjusting the magnitude of at least one of said IF signals; and
summing means, operatively coupled to said scaling means, for providing a sum signal representative of a sum of a difference, if any, in the magnitudes of said IF signals, and feeding said sum signal back to said scaling means;
wherein said scaling means adjusts the magnitude of said at least one of said IF signals so as to minimize any difference in the magnitude of said IF signals;(b) a transmitter comprising means for upconverting second baseband signals to said second RF signals; (c) a synthesizer operatively coupled to said receiver and transmitter for providing a downconversion local oscillator (LO) signal to said receiver and an upconversion LO signal to said transmitter; (d) a first antenna operatively coupled to said receiver for receiving said first RF signals; and (e) a second antenna operatively coupled to said transmitter for transmitting said second RF signals, wherein said RF signal is downconverted to an intermediate frequency of approximately one-half the channel spacing of the RF signal. - View Dependent Claims (33, 34)
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Specification