CN109547043B - Modulation method for saving radio frequency bandwidth - Google Patents

Modulation method for saving radio frequency bandwidth Download PDF

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CN109547043B
CN109547043B CN201811582743.9A CN201811582743A CN109547043B CN 109547043 B CN109547043 B CN 109547043B CN 201811582743 A CN201811582743 A CN 201811582743A CN 109547043 B CN109547043 B CN 109547043B
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digital
frequency synthesizer
baseband
component
digital direct
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CN109547043A (en
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夏永平
张勇
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CETC 58 Research Institute
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/005—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/12—Modulator circuits; Transmitter circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H04B2001/0491—Circuits with frequency synthesizers, frequency converters or modulators

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

The invention discloses a modulator for saving radio frequency bandwidth and a modulation method thereof, wherein the modulation method comprises the following steps: an in-phase channel Ib and an orthogonal channel Qb of the baseband forming signal are divided into two paths, and one path is subjected to complex multiplication with a signal generated by a digital direct frequency synthesizer; the other path is delayed and then carries out complex multiplication with a signal generated by a digital direct frequency synthesizer; the same-phase channel output phases output by the two complex multiplication are added and sent to a first digital-to-analog converter to be converted into analog signals, and the analog signals are sent to an up converter; meanwhile, the output phases of the two orthogonal channels output by complex multiplication are sent to a second digital-to-analog converter and are also sent to an up-converter after being converted into analog signals; and finally, outputting the radio frequency signal by an up-converter. In the invention, two paths of signals output by complex multiplication modulation are respectively converted by the digital-to-analog converter and then are subjected to up-conversion to output the frequency spectrum of the radio frequency signal, the image frequency of the useful signal does not exist, the useful signal is totally the useful signal, the bandwidth only occupies half of the frequency spectrum of the quadrature modulation radio frequency output signal, and the frequency spectrum efficiency is high.

Description

Modulation method for saving radio frequency bandwidth
Technical Field
The invention belongs to the technical field of communication, and particularly relates to a modulation method for saving radio frequency bandwidth.
Background
In a transmitter of a wireless communication system, a baseband modulation signal carrying information needs to be up-converted to a radio frequency carrier for transmission, then is received by a receiver after wireless transmission, and then is down-converted, and finally the information is demodulated. In the modulator, the baseband signal is usually quadrature modulated, modulated to an intermediate frequency (e.g., 72MHz), and then up-converted.
Baseband shaping signal modulation, typically quadrature modulation, is employed. The schematic block diagram is shown in figure 1. The baseband forming signals (an in-phase channel Ib and an orthogonal channel Qb) are divided into two paths, and one path is multiplied by a corresponding path of a 10MHz signal (an in-phase channel I10 and an orthogonal channel Q10) generated by the digital direct frequency synthesizer respectively. The other path is respectively multiplied by corresponding channels of 24MHz signals (an in-phase channel I24 and a quadrature channel Q24) generated by a digital direct frequency synthesizer after time delay. Then adding products of the same-phase channels, and sending the products and Iout to a first digital-to-analog converter DACi to be converted into analog signals and then sending the analog signals to an up-converter; and simultaneously, transmitting the product sum Qout of the orthogonal channel to a second digital-to-analog converter DACq, converting the product sum Qout into an analog signal, and then transmitting the analog signal to an up-converter. And finally, outputting the radio frequency signal by an up-converter.
The quadrature modulation part uses the mathematical expression as follows:
Iout＝Ib*I10+Ib1*I24,
Qout＝Qb*Q10+Qb1*Q24。
the two signals (Iout and Qout) output by the quadrature modulation also contain the mirror frequency of the signals except the signals required by the quadrature modulation. The frequency spectrums of the radio frequency signals output after the two paths of signals (Iout and Qout) are respectively converted by the digital-to-analog converter and then subjected to up-conversion are mirror image frequencies which are distributed symmetrically left and right and also contain useful signals, so that the bandwidth of the useful signals is only about half of the frequency spectrum of the radio frequency output signals, and the frequency spectrum efficiency is low.
Disclosure of Invention
In order to solve the above technical problem, the present invention provides a modulation method that saves the radio frequency bandwidth.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the invention provides a modulation method for saving radio frequency bandwidth, which uses a modulator to modulate, wherein the modulator comprises a digital direct frequency synthesizer DDS, a delayer, a first complex multiplication device, a second digital-to-analog converter DACq, a first digital-to-analog converter DACi and an up-converter, the first complex multiplication device multiplies an in-phase component Ib of a baseband forming signal by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies a quadrature component Qb of the baseband forming signal by an in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies an in-phase component Ib1 of the baseband forming signal delayed by the delayer by an in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies a quadrature component Qb1 of the baseband forming signal delayed by the delayer by a quadrature component Q7 of the digital direct frequency synthesizer DDS, then, Qout obtained by adding the four multiplied signals is sent to a second digital-to-analog converter DACq; the second complex multiplication device multiplies the in-phase component Ib of the baseband forming signal by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies the quadrature component Qb of the baseband forming signal by the quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies the in-phase component Ib1 of the baseband forming signal delayed by the delayer by the quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies the quadrature component Qb1 of the baseband forming signal delayed by the delayer by the in-phase component I7 of the digital direct frequency synthesizer DDS, and then sends the obtained Iout to the first digital-to-analog converter DACi; the output ends of the second digital-to-analog converter DACq and the second digital-to-analog converter DACq are electrically connected with the input end of the up-converter;
the modulation method comprises the following steps:
s1, multiplying the in-phase component Ib of the baseband forming signal by the orthogonal component Q7 of the digital direct frequency synthesizer DDS, multiplying the orthogonal component Qb of the baseband forming signal by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplying the in-phase component Ib1 of the baseband forming signal delayed by a delayer by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplying the orthogonal component Qb1 of the baseband forming signal delayed by the delayer by the orthogonal component Q7 of the digital direct frequency synthesizer DDS, and then sending Qout obtained by adding the four multiplied signals to a second digital-to-analog converter DACq;
s2, multiplying an in-phase component Ib of a baseband forming signal by an in-phase component I7 of a digital direct frequency synthesizer DDS, multiplying a quadrature component Qb of the baseband forming signal by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplying the in-phase component Ib1 of the baseband forming signal delayed by a delayer by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplying the quadrature component Qb1 of the baseband forming signal delayed by the delayer by an in-phase component I7 of the digital direct frequency synthesizer DDS, and then sending the obtained Iout to a first digital-to-analog converter DACi;
s3, sending the analog signals converted in the steps S1 and S2 to an up-converter;
the complex multiplication modulation part adopts the following mathematical expression:
Iout＝(Ib*I7–Qb*Q7)+(Ib1*Q7–Qb1*I7)；
Qout＝(Ib*Q7+Qb*I7)+(Ib1*I7+Qb1*Q7)；
and S4, outputting the radio frequency signal by the up converter.
Preferably, the frequency of the signal generated by the digital direct frequency synthesizer DDS in steps S1 and S2 is twice the center frequency of the baseband shaping signal.
The invention has the following beneficial effects: in the invention, two paths of signals output by complex multiplication modulation are respectively converted by the digital-to-analog converter and then are subjected to up-conversion to output the frequency spectrum of the radio frequency signal, the image frequency of the useful signal does not exist, the useful signal is totally the useful signal, the bandwidth only occupies half of the frequency spectrum of the quadrature modulation radio frequency output signal, and the frequency spectrum efficiency is high. Meanwhile, intermediate frequency modulation and a filter thereof, and a radio frequency image rejection filter are cancelled, so that the cost is saved.
Drawings
Fig. 1 is a diagram illustrating the operation of quadrature modulation in the background art of the present invention.
Fig. 2 is a schematic diagram of the operation of a modulator for saving radio frequency bandwidth according to the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
To achieve the object of the present invention, as shown in fig. 2, in one embodiment of the present invention, a modulation method for saving radio frequency bandwidth is provided, which uses a modulator to perform modulation, the modulator includes a digital direct frequency synthesizer DDS, a time delay, a first complex multiplication device, a second digital-to-analog converter DACq, a first digital-to-analog converter DACi, and an up-converter, the first complex multiplication device multiplies an in-phase component Ib of a baseband shaping signal by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies a quadrature component Qb of the baseband shaping signal by an in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies an in-phase component Ib1 of the baseband shaping signal delayed by an in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies a quadrature component Qb1 of the baseband shaping signal delayed by the time delay by the digital direct frequency synthesizer DDS by a quadrature component Q7 of the digital direct frequency synthesizer DDS, then, Qout obtained by adding the four multiplied signals is sent to a second digital-to-analog converter DACq; the second complex multiplication device multiplies the in-phase component Ib of the baseband forming signal by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies the quadrature component Qb of the baseband forming signal by the quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies the in-phase component Ib1 of the baseband forming signal delayed by the delayer by the quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies the quadrature component Qb1 of the baseband forming signal delayed by the delayer by the in-phase component I7 of the digital direct frequency synthesizer DDS, and then sends the obtained Iout to the first digital-to-analog converter DACi; the output ends of the second digital-to-analog converter DACq and the second digital-to-analog converter DACq are electrically connected with the input end of the up-converter;
the modulation method comprises the following steps:
s1, multiplying the in-phase component Ib of the baseband forming signal by the orthogonal component Q7 of the digital direct frequency synthesizer DDS, multiplying the orthogonal component Qb of the baseband forming signal by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplying the in-phase component Ib1 of the baseband forming signal delayed by a delayer by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplying the orthogonal component Qb1 of the baseband forming signal delayed by the delayer by the orthogonal component Q7 of the digital direct frequency synthesizer DDS, and then sending Qout obtained by adding the four multiplied signals to a second digital-to-analog converter DACq;
s2, multiplying an in-phase component Ib of a baseband forming signal by an in-phase component I7 of a digital direct frequency synthesizer DDS, multiplying a quadrature component Qb of the baseband forming signal by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplying the in-phase component Ib1 of the baseband forming signal delayed by a delayer by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplying the quadrature component Qb1 of the baseband forming signal delayed by the delayer by an in-phase component I7 of the digital direct frequency synthesizer DDS, and then sending the obtained Iout to a first digital-to-analog converter DACi;
s3, sending the analog signals converted in the steps S1 and S2 to an up-converter;
the complex multiplication modulation part adopts the following mathematical expression:
Iout＝(Ib*I7–Qb*Q7)+(Ib1*Q7–Qb1*I7)；
Qout＝(Ib*Q7+Qb*I7)+(Ib1*I7+Qb1*Q7)；
and S4, outputting the radio frequency signal by the up converter.
Specifically, the frequency of the signal generated by the digital direct frequency synthesizer DDS in steps S1 and S2 is twice the center frequency of the baseband shaping signal.
In the invention, two paths of signals output by complex multiplication modulation are respectively converted by the digital-to-analog converter and then are subjected to up-conversion to output the frequency spectrum of the radio frequency signal, the image frequency of the useful signal does not exist, the useful signal is totally the useful signal, the bandwidth only occupies half of the frequency spectrum of the quadrature modulation radio frequency output signal, and the frequency spectrum efficiency is high.
Meanwhile, intermediate frequency modulation and a filter thereof, and a radio frequency image rejection filter are cancelled, so that the cost is saved.
By comparing the performance of quadrature modulation and complex multiplication modulation, we can see that the complex multiplication modulation occupies more than half of radio frequency bandwidth than the conventional quadrature modulation on the premise of equivalent implementation complexity (occupying FPGA resources), and has higher spectral efficiency and communication performance. In the baseband signal processing of a transmitter of a wireless communication system, it is recommended to replace quadrature modulation with complex-product modulation.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept of the present invention, and these changes and modifications are all within the scope of the present invention.

Claims (2)

1. A modulation method for saving radio frequency bandwidth is characterized in that a modulator is used for modulation, the modulator comprises a digital direct frequency synthesizer DDS, a delayer, a first complex multiplication device, a second digital-to-analog converter DACq, a first digital-to-analog converter DACi and an up-converter, the first complex multiplication device multiplies an in-phase component Ib of a baseband shaping signal by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies a quadrature component Qb of the baseband shaping signal by an in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies an in-phase component Ib1 of the baseband shaping signal delayed by the delayer by an in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies a quadrature component Qb1 of the baseband shaping signal delayed by the delayer by a quadrature component Q7 of the digital direct frequency synthesizer DDS, then, Qout obtained by adding the four multiplied signals is sent to a second digital-to-analog converter DACq; the second complex multiplication device multiplies the in-phase component Ib of the baseband forming signal by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplies the quadrature component Qb of the baseband forming signal by the quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies the in-phase component Ib1 of the baseband forming signal delayed by the delayer by the quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplies the quadrature component Qb1 of the baseband forming signal delayed by the delayer by the in-phase component I7 of the digital direct frequency synthesizer DDS, and then sends the obtained Iout to the first digital-to-analog converter DACi; the output ends of the second digital-to-analog converter DACq and the second digital-to-analog converter DACq are electrically connected with the input end of the up-converter;
the modulation method comprises the following steps:
s1, multiplying the in-phase component Ib of the baseband forming signal by the orthogonal component Q7 of the digital direct frequency synthesizer DDS, multiplying the orthogonal component Qb of the baseband forming signal by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplying the in-phase component Ib1 of the baseband forming signal delayed by a delayer by the in-phase component I7 of the digital direct frequency synthesizer DDS, multiplying the orthogonal component Qb1 of the baseband forming signal delayed by the delayer by the orthogonal component Q7 of the digital direct frequency synthesizer DDS, and then sending Qout obtained by adding the four multiplied signals to a second digital-to-analog converter DACq;
s2, multiplying an in-phase component Ib of a baseband forming signal by an in-phase component I7 of a digital direct frequency synthesizer DDS, multiplying a quadrature component Qb of the baseband forming signal by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplying the in-phase component Ib1 of the baseband forming signal delayed by a delayer by a quadrature component Q7 of the digital direct frequency synthesizer DDS, multiplying the quadrature component Qb1 of the baseband forming signal delayed by the delayer by an in-phase component I7 of the digital direct frequency synthesizer DDS, and then sending the obtained Iout to a first digital-to-analog converter DACi;
s3, sending the analog signals converted in the steps S1 and S2 to an up-converter;
the complex multiplication modulation part adopts the following mathematical expression:
Iout＝(Ib*I7–Qb*Q7)+(Ib1*Q7–Qb1*I7)；
Qout＝(Ib*Q7+Qb*I7)+(Ib1*I7+Qb1*Q7)；
and S4, outputting the radio frequency signal by the up converter.
2. The modulation method for saving radio frequency bandwidth according to claim 1, wherein the frequency of the signal generated by the digital direct frequency synthesizer DDS in steps S1 and S2 is twice the center frequency of the baseband shaping signal.
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