KR20090052770A - Apparatus and method for down-converting digital frequency in wireless telecommunication system - Google Patents
Apparatus and method for down-converting digital frequency in wireless telecommunication system Download PDFInfo
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- KR20090052770A KR20090052770A KR1020070119434A KR20070119434A KR20090052770A KR 20090052770 A KR20090052770 A KR 20090052770A KR 1020070119434 A KR1020070119434 A KR 1020070119434A KR 20070119434 A KR20070119434 A KR 20070119434A KR 20090052770 A KR20090052770 A KR 20090052770A
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- converter
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
- H03D7/16—Multiple-frequency-changing
- H03D7/165—Multiple-frequency-changing at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/12—Analogue/digital converters
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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
- H04B1/0003—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain
- H04B1/0007—Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain wherein the AD/DA conversion occurs at radiofrequency or intermediate frequency stage
- H04B1/001—Channel filtering, i.e. selecting a frequency channel within the SDR system
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- Power Engineering (AREA)
- Theoretical Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Superheterodyne Receivers (AREA)
Abstract
The present invention relates to an apparatus and method for digital frequency down conversion, the apparatus comprising: an A / D converter for sampling and converting an analog signal having an intermediate frequency (IF) into a digital signal; A demodulator for demodulating a digital signal using a cosine wave and a sinusoidal signal; A lowpass filter for removing an image signal from the demodulated signal and for lowering a data rate; And a channel filter for generating a baseband signal by filtering the output signal of the lowpass filter.
According to the present invention, configuration and design are simple and debugging is easy. In addition, the number of ADCs and SAW filters can be reduced, which reduces mass production and system cost, and reduces board size, enabling an integrated system and easily changing frequencies. In addition, the RF path is configured briefly.
Description
The present invention relates to a frequency down converter, and more particularly, to a digital frequency down converter and a method for converting an intermediate frequency signal into a baseband signal in a wireless communication system.
In general, in a wireless communication system, a base station is composed of a remote unit (RU) that is in charge of wireless communication with a terminal and a DU (Digtial Unit) that is in communication with the RU. The part in charge of the Rx function in the RU (Remote Unit) converts an intermediate frequency (Intermediate Frequency) signal input from the RF stage into a baseband signal, and the baseband signal is transmitted to a digital unit (DU). . In this case, in order to convert the intermediate frequency signal into a baseband signal, a frequency down converter is required.
FIG. 1 is a block diagram showing the configuration of a conventional digital frequency down converter, wherein a
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the technical problem to be solved by the present invention is to convert an analog signal to a digital signal using an A / D converter and then perform frequency conversion to perform an expensive SAW filter. It is an object of the present invention to provide an apparatus and method for digital frequency down conversion of a wireless communication system, which is economically advantageous due to no use.
Another object of the present invention is to sample the intermediate frequency signal input from the RF stage, and to down-convert the image signal to generate a baseband signal, so that the circuit configuration is relatively simple and the digital frequency down of the wireless communication system is easy to debug. To provide a conversion device and method.
In order to solve the above technical problem, the digital frequency down converter according to the present invention, the A / D converter for sampling the analog signal and convert it into a digital signal; A demodulator for demodulating the digital signal using a cosine wave and a sinusoidal signal; A low pass filter for passing only the low frequency band signal of the demodulated signal and reducing the data rate; And a channel filter for generating a baseband signal by filtering the output signal of the lowpass filter.
In order to solve the above technical problem, the digital frequency down conversion method according to the present invention comprises the steps of: sampling the analog signal and converting it into a digital signal; Demodulating the digital signal using a cosine wave and a sinusoidal signal; Passing only the low frequency band signal of the demodulated signal and lowering a data rate; And generating a baseband signal by filtering the signal at which the data rate is down.
According to the present invention, the configuration and design of the frequency down converter is simple and easy to debug. In addition, an I Q unbalance problem, which is a problem in the conventional analog signal processing method, is solved. By reducing the number of A / D converters and SAW filters, it is possible to reduce mass production and system cost. It is possible to reduce board size and to realize compact system and to change frequency easily. In addition, the RF path is briefly configured by performing one conversion on the RF stage using the IF stage at 115 MHz.
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments. For reference, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted in the following description.
2 is a block diagram showing an embodiment of the configuration of the digital frequency down conversion apparatus according to the present invention. The configuration is an A /
The A /
3 (1) and (2) show the frequency spectrum of the input signal and the output signal of the A /
The
4 is a block diagram illustrating a more detailed configuration of the
The
3 (2) and (3) shows the frequency spectrum of the input signal and the output signal of the
The
FIG. 5 is a block diagram illustrating a more detailed configuration of the
The second half
The
6 is a block diagram illustrating a more detailed configuration of the
The second
The digital frequency down converter according to the present invention can implement some components as a Field Programmable Gate Array (FPGA). The baseband signal output from the
9 is a flowchart illustrating a digital frequency down conversion method according to the present invention. An operation of the digital frequency down converter according to the present invention will be described with reference to FIG. 9.
First, an analog signal is sampled and converted into a digital signal. (Step S910) In this embodiment, a 115 MHz intermediate frequency (IF) signal is input to the A /
The signal input to the A /
Then, only the low frequency band signal of the demodulated signal is passed and the data rate is lowered (step S930). More specifically, the digital gained data is 32 bits, which is a half-band filter. Half-band Filter, 504, 554) must be changed to 16 bits. To this end, the bit width is adjusted through the
The half band filters 504 and 554 pass only a low frequency band signal among the signals demodulated by the
The
Thereafter, the signal which is down at the data rate of 20 Mbps by the
The channel filter design characteristic is expressed by
[Equation 1]
Bu = Fs (Nused / NFFT)
Where Bu is useful bandwidth and Fs is a baseband sampling rate.
The
On the other hand, the present invention described above can also be embodied as computer readable codes on a computer readable recording medium. Computer-readable recording media include any type of recording device that stores data that can be read by a computer system. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, hard disks, optical data storage devices, and also in the form of carrier waves (e.g., transmission over the Internet). It includes what is implemented. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. And functional programs, codes and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.
Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art to which the present invention pertains can implement the present invention in other specific forms without changing the technical spirit or essential features, The examples are to be understood in all respects as illustrative and not restrictive.
In addition, the scope of the present invention is specified by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention. Should be interpreted as
1 is a block diagram showing the configuration of a conventional digital frequency down converter.
2 is a block diagram showing an embodiment of the configuration of the digital frequency down conversion apparatus according to the present invention.
Figure 3 shows the frequency spectrum of the input and output signals for each component of the digital frequency down converter according to the present invention.
4 is a block diagram illustrating a more detailed configuration of the demodulator.
5 shows a more detailed configuration of the lowpass filter in a block diagram.
6 is a block diagram illustrating a more detailed configuration of the channel filter.
FIG. 7 may include a CPRI interface unit and a GTP, except for an A / D converter, to implement a digital frequency down converter according to the present invention as an FPGA.
8 is a block diagram of a digital frequency down converter according to the present invention designed using a system generator.
9 is a flowchart illustrating a digital frequency down conversion method according to the present invention.
10 shows the output baseband out of the channel filter.
Claims (18)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020070119434A KR20090052770A (en) | 2007-11-21 | 2007-11-21 | Apparatus and method for down-converting digital frequency in wireless telecommunication system |
PCT/KR2008/006855 WO2009066945A2 (en) | 2007-11-21 | 2008-11-20 | Apparatus and method for down-converting frequency in wireless communication system |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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KR1020070119434A KR20090052770A (en) | 2007-11-21 | 2007-11-21 | Apparatus and method for down-converting digital frequency in wireless telecommunication system |
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Publication Number | Publication Date |
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KR20090052770A true KR20090052770A (en) | 2009-05-26 |
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KR1020070119434A KR20090052770A (en) | 2007-11-21 | 2007-11-21 | Apparatus and method for down-converting digital frequency in wireless telecommunication system |
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KR (1) | KR20090052770A (en) |
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2007
- 2007-11-21 KR KR1020070119434A patent/KR20090052770A/en active IP Right Grant
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