CN103201994B - Method and system for programmable digital down-converter - Google Patents

Abstract

There is provided herein the radio communication equipment that can operate in the frequency of wide scope including signal processing apparatus.Device performs analog digital conversion to generate digital signal with the sample rate of pre-determining, and independent of the selected frequency in the frequency of this width scope, and digital signal is carried out digital processing with the data signal being associated with selected frequency band in base band output.

Description

Method and system for programmable digital down-converter

Technical field

The present invention relates generally to be configured to use able to programme to adapt to the Digital Down Convert of multiple frequency band, from the method and system of the quadrature modulation analog signal extraction data signal received.

Background technology

Existing radio receptor uses analog down converter that radio frequency (RF) signal is converted into the signal with one or more lower intermediate frequencies (IF).Analog down converter can have heterodyne (IF), superhet (multiple IF) or zero IF architecture (IF is actually 0 Hz).Analog down converter be subjected to simulation infringement, as analog variation (such as, component to component variation, temperature change, change in voltage and due to aging variability) and ineffective activity (that is, be designed to such as 880-915 The analog down converter that the special frequency bands such as MHz effectively operate is performed poor for other frequency bands such as such as 1920-1980 MHz).

Some analog down converter are also affected (but and not all architecture have all problems being listed below) by other problem: change (phase and amplitude), quadrature imbalance in frequency (in-phase component leak in quadrature component or vice versa as the same), gain are uneven, DC biasing and limited mirror image suppression (image rejection).

These infringements and problem currently make it difficult to be designed to process the frequency analog down converter (such as, to 880-915 MHz frequency band and all operate well 1920-1980 MHz frequency band) across the radiofrequency signal of wide frequency ranges.

Radiofrequency signal of directly sampling can not be down-converted to base band (0 Hz) by commercially available digital down converter unintentionally.In general it is assumed that the analogue signal inputting these digital down converters has been enter into intermediate frequency in the previous analog section of signal processing chain.

Correspondingly, it is desirable to provide avoid the problems referred to above and the device of defect, system and method.

Summary of the invention

One purpose is to overcome some defects described in front portion, and provides the method and apparatus that can operate in the frequency including the wide scope of frequency band of multiple pre-determining.One or more independent claims items are advantageously in cost and the reliability providing reduction in terms of the quadrature modulation analog signal extraction data signal received.

According to an example embodiment, signal processing apparatus can be included by the radio communication equipment of operation in the frequency of wide scope, signal processing apparatus is configured to receive analogue signal, perform analog digital conversion with the sample rate of pre-determining and independent of the selected frequency band in the frequency of wide scope, and export the data signal in base band, during Digital Signal Processing, concentrate on selected frequency band simultaneously.

According to another example embodiment, it is provided that a kind of analogue signal of orthogonal modulation that processes to export baseband digital data signal, the method for selected frequency band concentrate on the frequency of wide scope in a digital signal simultaneously in.Method includes being filtered the analogue signal received exporting the filtered analog signals including having the component of the frequency in the frequency range of pre-determining.Method also includes that filtered analog signals is converted into digital signal by the sample rate with pre-determining, and demodulated digital signal is to export complex digital signal.Method also includes being filtered complex digital signal including single mirror image in complex data signals.Method also includes filtered complex word signal is carried out down-sampling, is included in the down-sampling complex signal of a sample of each group of N number of continuous sample in filtered complex word signal to generate, and wherein, N is greater than or equal to the integer of two, and depends on selected frequency band.Method also includes extracting complex base band data signal from down-sampling complex signal.

According to another example embodiment, a kind of method processing modulated analog signal includes converting analog signals into digital signal with certain sample rate, and the target band of the frequency band independent of multiple pre-determining.Method also includes that quadrature demodulation digital signal is to export complex signal.Method also includes filtering, filtering complex signal is carried out down-sampling with output sample of each group of N number of continuous sample in supplied with digital signal, wherein, N is greater than or equal to the integer of two, and depend on that the selected frequency band of the frequency band of pre-determining, filtering and down-sampling use multiphase filter to perform.

According to another example embodiment, the method for the radio communications system that a kind of manufacture can operate in the wide frequency ranges including multiple frequency band is included on substrate between analog-digital converter and base band tuner installation quadrature demodulator, complex channel wave filter and down-sampler.Method also includes installing band selector, and band selector is configured to the offer operating parameter relevant with target band in multiple frequency bands to complex channel wave filter and down-sampler.

According to another example embodiment, the method for the radio communications system that a kind of manufacture can operate in the wide frequency ranges including multiple frequency band is included on substrate between analog-digital converter and base band tuner installation quadrature demodulator and multiphase filter.Method also includes installing band selector, and band selector is configured to the offer operating parameter relevant with target band in multiple frequency bands to multiphase filter.

Accompanying drawing explanation

Accompanying drawing combines in the description and constitutes one part, it is shown that one or more embodiments, and explains these embodiments together with the description.In the drawings:

Fig. 1 is according to an example embodiment, is configured to receive analogue signal, sampled analogue signals carries out Digital Down Convert and the output schematic diagram at the equipment of the digital signal of base band；

Fig. 2 A represents according to an example embodiment, by the frequency spectrum of the signal of the analog filter output of equipment；

Fig. 2 B represents according to an example embodiment, by the frequency spectrum of the signal of the analog-digital converter output of equipment；

Fig. 2 C represents according to an example embodiment, by the frequency spectrum of the complex signal of the quadrature demodulator output of equipment；

Fig. 2 D represents according to an example embodiment, the frequency spectrum of the multiple filtering signal being selected wave filter output by the complex channel of equipment；

Fig. 2 E represents according to an example embodiment, by the frequency spectrum of the complex signal of the digital down converter output of equipment；

Fig. 2 F represents according to an example embodiment, by the frequency spectrum of the complex data signals of the complex base band tuner output of equipment；

Fig. 3 is the schematic diagram of the equipment according to another example embodiment；

Fig. 4 be illustrate according to an example embodiment, process quadrature modulation analog signal with the method for output digital data signal in the flow chart of step that performs；

Fig. 5 is the schematic diagram according to an example embodiment, in a radio communications system device；

Fig. 6 is to illustrate according to an example embodiment, the flow chart of step that performs in the method processing modulated analog signal；

Fig. 7 is flow chart, it is shown that according to an example embodiment, in manufacturing the method for radio communications system that can operate in the wide frequency ranges including multiple frequency band the step of execution；And

Fig. 8 is flow chart, it is shown that according to another example embodiment, in manufacturing the method for radio communications system that can operate in the wide frequency ranges including multiple frequency band the step of execution.

Detailed description of the invention

The following description of example embodiment is referring to the drawings.The identical same or similar unit of label identification in different graphic.Described in detail below it is not intended to the present invention.On the contrary, the scope of the present invention is defined by appended claims.For simplicity's sake, the following examples are described according to term and the structure of radio frequency receiver.But, embodiment to be discussed is not limited to these systems, but may be used on other system being configured to process radiofrequency signal.

" embodiment " or " embodiment " are quoted special characteristic, structure or the characteristic referring to combine an embodiment description and are included at least one embodiment of the present invention by description in the whole text.Therefore, " an embodiment " or " in one embodiment " phrase in the appearance of description various places throughout are not necessarily all referring to same embodiment.Additionally, specific feature, structure or characteristic can combine the most in any suitable manner.

Process described below and equipment by such as combining digital quadrature demodulation, aliasing (aliasing) that digital filtering, extraction sampled signal cause and numeral polyphony humorous, it is achieved that the flexible digital down coversion of the radio signal sampled with the sample rate of pre-determining in the frequency of wide scope.

For ease of illustrating and noting limit, according to an example embodiment, equipment 100 shown in Fig. 1 is configured to receive quadrature modulation analog radio signal, and exports base-band data signal.

Equipment 100 shown in Fig. 1 includes that analog filter 110, analog-digital converter (ADC) 120, quadrature demodulator 130, complex channel select wave filter 140, numeral down-sampler 150 and base band tuner 160.

Analog filter 110 is configured to receive quadrature modulation analog radio signal, and the analogue signal received is filtered with only by having the component of the frequency in some or all frequency ranges in Nyquist region, in Nyquist region, analog-digital converter (ADC) 120 provide enough performances.Nyquist region is defined as equal to sample frequency (F_s) the bandwidth of half.Frequency domain includes this type of region an infinite number of.Such as, in positive frequency domain, the first Nyquist region is from " 0 " frequency (that is, DC) to F_s/ 2, the second Nyquist region is from F_s/ 2 arrive F_s, the 3rd Nyquist region is from F_sTo 3F_s/ 2 etc..Assume that the mirror image of target band is about in frequency F_a, Fig. 2 A represents the frequency spectrum of the filtering signal exported by analog filter 110.

ADC 120 is configured to sample frequency F_sThe analog filtering signal of analog filter 110 output is sampled.Recently, the ADC device of the increase precision with high sample rate and sample is made available by.According to Nyquist sampling theory, if at least if its frequency twice is soon to analog signal sampling, then not losing information when reconstruction signal.When analogue signal has higher than the frequency of the half of sample frequency, signal is by double sampling, and relative to F_s/ 2 " reflections " or " folding ".Therefore, if the signal packet paid close attention to is contained in a Nyquist region, the most such as, tool 2GSps(lucky sub-sampling number per second) the ADC of sample rate ability be of about 900 The frequency band of MHz and the frequency band of about 1900 MHz are provided which enough samples.We it is contemplated that hereinafter described equipment and method there is the specific dependency of the sample rate more than 1 GSps, but they are not limited to this.

Fig. 2 B represents the frequency spectrum of the digital signal that ADC 120 exports.The signal of ADC 120 output is real signal, and it or orthogonal demodulation signal.After sampling, in a digital signal, relative to F_s/ 2 reflections are about at F_aThe frequency spectrum of analogue signal, and at all other (n-1, n) individual F_sInterval is repeated arrive F with 0_sThe frequency distribution (wherein, n is any integer) of interval medium frequency distribution analogous shape.

Generally, ADC 120 operates with the sample rate of pre-determining, but sample rate needs not to be fixing.Clock signal (can be generated by local oscillator, not shown) is used for driving ADC 120 to perform sampling with the sample rate of pre-determining.The frequency of clock signal can be fixing or variable.

Quadrature demodulator 130 is configured to receive the sampled signal of ADC 120 output, and the digital signal conversion received becomes to have the complex signal of the frequency distribution relative to digital signal medium frequency distributions shift.Such as, F can be passed through_s/ 4 by frequency shift (FS) to about at F_a-F_s/ 4 and 2F_s-F_a-F_sI.e., high side mixing and downside are mixed/4().Fig. 2 C represents the frequency spectrum of the complex signal that quadrature demodulator 130 exports.As will be discussed in more detail, in signal processing chain, the position of quadrature demodulator 130 can be different from its position in equipment 100.

Complex channel selection wave filter 140 filters complex signal and has about 2F_s-F_a-F_sA part for the frequency of/4, output has about F_a-F_sThe residual signal of the frequency of/4.Fig. 2 D represents the frequency spectrum of the multiple filtering signal being selected wave filter 140 to export by complex channel.

Numeral down-sampler 150, by abandoning N-1 sample of N number of sample, extracts the complex signal selecting wave filter 140 to receive from complex channel and has about at F with output_aliased=mod(F_a-F_s/4, F_s/ N) the signal of new lower frequency.Such as, if N=8, then Fig. 2 E represents had about at mod (F by what digital down converter 150 exported_a-F_s/4, F_s/ 8) frequency spectrum of the new lower frequency complex signal of frequency.The existence of numeral down-sampler 150 reduces the quantity of sample, and therefore reduces the power consumption for complex base band tuner 160.In signal processing chain, the position of digital down converter 150 can be different from its position in equipment 100.

The new lower frequency signal that complex channel is selected wave filter 140 to export by complex base band tuner 160 subsequently is transformed into base band (that is, being centered in 0 Hz).Fig. 2 F represents the frequency spectrum of the digital signal in base band exported by complex base band tuner 160.The example of complex base band tuner is described in U.S. Patent Application Publication description 2009/0316838.

In view of the above description of equipment 100, it will be appreciated by those skilled in the art that equipment 100 is by depending on that the different parameters of target band operates.It is to say, equipment 100 is configured to use in the frequency of wide scope, but in preset time, it is tuned to the predefined frequency band in the frequency band that the widest scope covers as target.Special frequency band is selected to be made up of multiple tuner frequencies (can the be 0) N of appointment and filter coefficient physically.

As operating parameter, the information about selected frequency band can be to select one of multiple available filters as necessary to analog filter 110.But, ADC 120 can operate in identical sample rate, and does not consider target band (it is therefore not necessary to receiving the information about selected frequency band).It is similar to ADC 120, quadrature demodulator 130 is without receiving the information about selected frequency band as operating parameter.

Complex channel selects wave filter 140 to be at F_sSample rate run and select at 0≤F_a<=F_sBetween the digital filter of frequency.But, complex channel selection wave filter 140 can be used in filtering complex signal to be had about at 2F_s-F_a-F_sThe part of the frequency of/4, and export complex signal there is about F_a-F_sThe part of the frequency of/4.Complex channel selects wave filter 140 can include the multiple wave filter corresponding to different target frequency band, and depending on the information about target band to be processed, these frequency bands are each is inserted into signal processing chain (or being removed from it).

The digital N of the operation characterizing numeral down-sampler 150 depends on target band.Between final output sample rate and ADC sample rate, the fine setting of relation can be realized by adding rate change wave filter after complex channel selects wave filter 140.For example, it is contemplated that maximum possible ADC sample rate is 2.5 GSps, and final goal sample rate is about the exemplary rate that 245.76 MSps(with LTE sample rates are relevant).For realizing simplicity, it is desirable to the integral number power (N=8 in this example) of decimal scale 2.In the case of not having speed change wave filter, this is by the ADC sample rate of hint 1966.08.By add 8/10 speed change wave filter, it is desirable to ADC sample rate become 2.4576 GSps, this is closer to maximum possible speed.The precise controlling with final sample rate allows system-level optimization.Speed change wave filter such as can provide after multiple tuner.

In one embodiment, user interface or controller allow one of user's selection of equipment 100 frequency band in the frequency of the wide scope of equipment 100 covering, and user interface or controller are then able to provide operating parameter for equipment 100, such as multiple tuner frequencies (may be 0) N and filter coefficient, these parameter configuration equipment 100 performs the Digital Down Convert for selected frequency band.

In an alternative shown in Fig. 3, equipment 200 includes being similar to analog filter 110, ADC 120, quadrature demodulator 130 and the analog filter 210 of the humorous device of baseband complex 160, ADC 220, quadrature demodulator 230 and the humorous device of baseband complex 260.In the device 200, by use multiphase filter 245 realize complex channel wave filter and numeral down-sampler functional.

In another alternative embodiment, if N is the integral multiple of 4, then realize other hardware optimization by combination multiphase filter 245 and quadrature demodulator 230.In the case, the wave filter of combination/quadrature demodulator complexity is minimized, and on tuning motility without impact.

Fig. 4 is the flow chart of the step performed in process quadrature modulation analog signal is with the method 300 of output digital data signal.Method 300 can be performed by equipment 100.

At S310, method 300 includes being filtered the orthogonal demodulation signal received selecting the part of analogue signal received, and this part includes the component with the frequency in the frequency range of pre-determining.Additionally, at S320, method 300 includes that this fractional conversion of the analogue signal received is become digital signal by the sample rate with pre-determining.

At S330, method 300 includes that demodulated digital signal is to export complex digital signal.Subsequently, at S340, method 300 includes being filtered complex digital signal including single mirror image in complex data signals.At S350, method 300 includes filtered complex word signal is carried out down-sampling, is included in the down-sampling complex signal of a sample of each group of N number of continuous sample in filtering complex signal to generate, and wherein, N is greater than or equal to the integer of two.Finally, at S360, method 300 includes extracting complex base band data signal from down-sampling complex signal.

Method 300 may also comprise selection one of frequency band of multiple pre-determining in operable frequency range.By depending on the operating parameter of the selected frequency band of the frequency band of multiple pre-determining, perform in the down-sampling (S350) of the filtering (S310) of orthogonal demodulation signal, the filtering (S340) of complex digital signal and filtered complex word signal received is one or more.Therefore, the frequency range of pre-determining can be depending on the selected frequency band of frequency band of multiple pre-determining.It can be the value execution down-sampling of the N of the selected frequency band of the frequency band depending on multiple pre-determining.It it is alternatively the value execution down-sampling of the N of the power of 2.

Fig. 5 illustrates the device 400 that can be used together in a radio communications system with other (unshowned) general components.The such as existence of 400 devices such as grade makes radio communications system can operate in the frequency including the wide scope of frequency band of multiple pre-determining.

Device 400 in Fig. 5 includes the analog-digital converter 410 being configured to convert analog signals into digital signal with certain sample rate, and independent of the target band of multiple pre-determining frequency bands.Additionally, device 400 includes the quadrature demodulator 420 being configured to that the digital signal received from analog-digital converter 410 is converted into complex signal.

Equipment 400 also includes multiphase filter 430, multiphase filter 430 is configured to be filtered including the single mirror image of the target band of pre-determining frequency band to complex signal, and filtering complex signal carries out down-sampling to export a sample of each group of N number of continuous sample.N is greater than or equal to the integer of 2 herein, and depends on the selected frequency band of the frequency band of pre-determining.

Fig. 6 includes the flow chart being shown in the method 600 processing modulated analog signal the step performed.At S610, method 600 includes converting analog signals into digital signal with certain sample rate, and independent of the target band of pre-determining frequency band.At S620, method 600 includes that quadrature demodulation digital signal is to export complex signal.Method 600 is additionally included in S630 and complex signal is filtered including the single mirror image of the target band of pre-determining frequency band, and filtering complex signal carries out a down-sampling sample with each group of the N number of continuous sample of output, and filtering and down-sampling use multiphase filter to perform.N is greater than or equal to the integer of two herein, and depends on the selected frequency band of the frequency band of pre-determining.

Fig. 7 and 8 is flow chart, it is shown that the step performed in the method 800 and 900 manufacturing the radio communications system that can operate in the wide frequency ranges including multiple frequency band.In step S810, method 800 is included between analog-digital converter and base band tuner installation quadrature demodulator, complex channel wave filter and down-sampler.Additionally, at S820, method 800 includes installing band selector, band selector is configured to the offer operating parameter relevant with target band in multiple frequency bands to complex channel wave filter and down-sampler.

Method 900 is included in S910 and installs quadrature demodulator and multiphase filter between analog-digital converter and base band tuner.Method 900 is additionally included in S920 and installs band selector, and band selector is configured to the offer operating parameter relevant with target band in multiple frequency bands to multiphase filter.

Disclosed example embodiment provides the method and apparatus that can use in a radio communications system and the method manufactured for it.Should be understood that this description is not intended to limit the present invention.On the contrary, example embodiment be intended to the scope of the present invention that such as appended claims define include alternative, amendment and equivalent.Additionally, in the detailed description of example embodiment, set forth many specific details to provide the detailed understanding of described invention.However, it will be apparent to those skilled in the art that, various embodiment can be put into practice in the case of without this type of specific detail.

As those skilled in the art it will also be understood that, example embodiment can be implemented in a wireless communication device.Correspondingly, example embodiment can use the form of embodiment of complete hardware embodiment or combination hardware and software aspects.

Although the feature of shown example embodiment and embodiment are described in the embodiment of particular combination, but each feature or unit can be used alone and without the further feature of embodiment and unit, or use with or without the various combining forms of further feature disclosed herein and unit with band.

Claims (13)

1. the radio communication equipment that can operate in the frequency of wide scope, including:

Signal processing apparatus, it is configured to receive analogue signal, analog digital conversion is performed to generate digital signal with the sample rate of pre-determining, and independent of the selected frequency band in the frequency of described wide scope, and described digital signal is carried out digital processing with the data signal being associated with described selected frequency band in base band output, wherein, described signal processing apparatus includes:

Analog filter, is configured to be filtered the analogue signal received with only by having the component of some or all frequency range medium frequencys in Nyquist region；

Analog-digital converter, is configured to the analog signal sampling to being filtered of the sample rate with described pre-determining, and exports described digital signal；

Quadrature demodulator, is configured to perform the quadrature demodulation of described digital signal, and exports the complex signal of the mirror image including complex data signals and described complex data signals；

Complex channel selects wave filter, is configured to receive described complex data signals, and exports the filtering complex signal of one of the described mirror image including the most described complex data signals or described complex data signals；

Numeral down-sampler, is configured to receive described filtering complex signal and generation is included in the down-sampling complex signal of a sample of each group of N number of continuous sample in described filtering complex signal, and wherein N is greater than or equal to the integer of two, and depends on selected frequency band；And

Complex base band tuner, is configured to receive described down-sampling complex signal, and exports complex base band data signal.

2. radio communication equipment as claimed in claim 1, also includes:

Band selector, is at least connected to described numeral down-sampler, and is configured to provide the information about selected frequency band.

3. radio communication equipment as claimed in claim 1, wherein said complex channel selects wave filter to be configured to filter the component of the complex data signals received described in the frequency having in the scope depending on selected frequency band.

4. radio communication equipment as claimed in claim 1, wherein said numeral down-sampler is configured to select to depend on the digital N of selected frequency band.

5. radio communication equipment as claimed in claim 1, the digital N that wherein said numeral down-sampler is configured as having the value of the power being 2 operates.

6. radio communication equipment as claimed in claim 1, the sample rate of wherein said pre-determining is more than 1 GSps.

7. radio communication equipment as claimed in claim 1, also includes:

Speed change wave filter, is connected to described base band tuner, and is configured to input described speed change wave filter and have the digital signal of described pre-determining sample rate and be converted into the digital signal of the part sampling with described pre-determining sample rate.

8. the radio communication equipment that can operate in the frequency of wide scope, including:

Signal processing apparatus, it is configured to receive analogue signal, analog digital conversion is performed to generate digital signal with the sample rate of pre-determining, and independent of the selected frequency band in the frequency of described wide scope, and described digital signal is carried out digital processing with the data signal being associated with described selected frequency band in base band output, wherein, described signal processing apparatus includes:

Analog filter, is configured to be filtered the analogue signal received with only by having the component of some or all frequency range medium frequencys in Nyquist region；

Analog-digital converter, is configured to the analog signal sampling to being filtered of the sample rate with pre-determining, and exports sampled digital signal；

Quadrature demodulator, is configured to perform the quadrature demodulation of described sampled digital signal, and exports complex signal；

Multiphase filter, it is configured to be filtered including single mirror image in described complex signal to described complex signal, and filter complex signal described in down-sampling and be included in the down-sampling complex signal of a sample of each group of N number of continuous sample in described filtering complex signal with output, wherein N is greater than or equal to the integer of two, and depends on selected frequency band；And

Complex base band tuner, is configured to receive described down-sampling complex signal, and extracts complex base band data signal from described down-sampling complex signal.

9. radio communication equipment as claimed in claim 8, wherein said quadrature demodulator and described multiphase filter are integrated with each other.

10. process the analogue signal of orthogonal modulation to export a baseband digital data signal, the method for selected frequency band in simultaneously concentrating on the frequency of wide scope in a digital signal, including:

Multiple pre-determining frequency bands in operable frequency range select described frequency band；

Analogue signal is filtered with only by having the component of some or all frequency range medium frequencys in Nyquist region；

With the sample rate of pre-determining, the analogue signal filtered is converted into digital signal；

Digital signal described in quadrature demodulation is to export complex signal；

It is filtered including single mirror image in described complex signal to described complex signal；

Described filtering complex signal being carried out down-sampling, is included in the down-sampling complex signal of a sample of each group of N number of continuous sample in described filtering complex signal to generate, wherein N is greater than or equal to the integer of two, and depends on selected frequency band；And

Complex base band data signal is extracted from described down-sampling complex signal, wherein based on depending on the operating parameter of selected frequency band, one or more in the described extraction of the described filtering of orthogonal demodulation signal, the described filtering of described complex signal and the described complex base band data signal that receive described in execution.

11. methods as claimed in claim 10, the sample rate of wherein said pre-determining is more than 1 Gsps.

12. methods as claimed in claim 10, also include:

Change pre-determining sample rate described digital signal with output described pre-determining sample rate a part sampling signal.

13. 1 kinds of analogue signals processing orthogonal modulation to export baseband digital data signal, the method for selected frequency band concentrate on the frequency of wide scope in a digital signal simultaneously in, including:

Analogue signal is filtered with only by having the component of some or all frequency range medium frequencys in Nyquist region；

With the sample rate of pre-determining, the analogue signal filtered is converted into digital signal；

Digital signal described in quadrature demodulation is to export complex signal；

It is filtered including single mirror image in described complex signal to described complex signal；

Described filtering complex signal being carried out down-sampling, is included in the down-sampling complex signal of a sample of each group of N number of continuous sample in described filtering complex signal to generate, wherein N is greater than or equal to the integer of two, and depends on selected frequency band；And

Extract complex base band data signal from described down-sampling complex signal, be wherein that the value of the N of the power being 2 performs described down-sampling.