CN104716921A - Medium frequency filtering device, spectrometer and medium frequency filtering method - Google Patents
Medium frequency filtering device, spectrometer and medium frequency filtering method Download PDFInfo
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Abstract
The invention discloses a medium frequency filtering device, a spectrometer and a medium frequency filtering method. The medium frequency filtering device comprises a digital oscillator unit, a digital mixer unit and a filter unit. The digital oscillator unit is connected to the digital mixer unit and is used for generating N oscillation signals with different frequency point information and sending the oscillation information to the digital mixer unit. The digital mixer unit is used for receiving digital medium frequency signals and carries out down-conversion on the digital medium frequency signals into fundamental frequency signals from a first fundamental frequency signal to an <N>th fundamental frequency signal according to the oscillation signals from a first oscillation signal to an <N>th oscillation signal. The filter unit is connected to the digital mixer unit and is used for carrying out filtering on the fundamental frequency signals from the first fundamental frequency signal to the <N>th fundamental frequency signal according to resolution ratio bandwidth, and accordingly filtering signals are obtained. The spectrometer comprises a signal collecting unit, an analog mixing unit, a digital medium frequency filtering unit, a detection unit and a displaying unit. According to the medium frequency filtering device, in one clock period of an ADC, the ADC only collects the digital medium frequency signals for one time, and the working efficiency of the medium frequency filtering device is improved.
Description
Technical field
The present invention relates to spectrum analyzer field, be specifically related to a kind of intermediate frequency filtering device, frequency spectrograph and intermediate frequency filtering method.
Background technology
Existing sweep frequency technique adopts superhet spectrum analyzer usually, based on the principle of beat receiver, by mixing thus the frequency point information obtained required by us, and by the method for change local frequency, reaches the measurement of a frequency range." heterodyne " refers to mixing, namely refers to change frequency, and the meaning of " surpassing " then refers to superaudio frequency or the frequency range higher than audio frequency.
The time of the whole scanning process of frequency spectrograph is determined by intermediate-frequency filter, and bandwidth of operation and the transient response operating time of intermediate-frequency filter are inversely proportional to.When RBW is less time, the response time of intermediate-frequency filter is very long, has a strong impact on spectrum measurement process.
Adopt the spectrum scan method of prior art, owing to being first be down-converted to intermediate frequency through analog circuit, then through digital IF filter, form corresponding resolution, therefore when resolution is too small time, because the intermediate-frequency filter response time is very long, sweep speed will be made very slow.In prior art; usually FFT (Fast Fourier Transformation can be used; fast Fourier transform; the fast algorithm of discrete Fourier transform (DFT)) technology solves long problem of little RBW situation lower response time; but the operation resource that the usual consumption rate of FFT is more, can cause cost compare high.
Be illustrated in figure 1 in the frequency spectrograph of prior art, the principle schematic of intermediate frequency filtering technology.The filtering signal that ADC (Analog-to-Digital Converter, analog to digital converter or analog/digital converter) samples, the signal normally containing broad frequency band, intermediate-frequency filter is according to the frequency f of Current Scan
n, by f
nbe converted to zero-frequency again, then carry out DDC (Digital Down Converter, digital down converter) Digital Down Convert; And according to RBW, through digital IF filter, obtain the signal energy under current RBW, complete one-shot measurement.The next frequency f scanned again
n+1, ADC meeting Resurvey intermediate frequency data, proceeds the process of intermediate frequency frequency conversion and filtering.Because the main time consumption of measuring is on RBW digital IF filter, therefore each frequency needs the time of a consumption RBW digital IF filter.
Namely in prior art, to the measurement completing each frequency, intermediate-frequency filter all will carry out single treatment process according to RBW, and when RBW is less time, the response time of intermediate-frequency filter is very long, has had a strong impact on the efficiency of spectrum measurement like this, has caused energy consumption and waste of time.
In prior art, in fact when little RBW, the very wide signal bandwidth major part entering intermediate frequency, all by filtering, only remains some energy near RBW width; If we in wider intermediate-frequency bandwidth with in the longer time, can carry out intermediate frequency filtering at hardware view concurrently, then under identical resources costs, sweep time can be reduced exponentially, reach the object adding fast scan speed.
Be illustrated in figure 2 the structural representation of the intermediate frequency filtering device of the present embodiment, comprise analog to digital converter (i.e. ADC) 001, digital oscillator (i.e. NCO, numerically controlled oscillator, numerically-controlled oscillator) 002, digital mixer 003 and low pass filter 004.
The middle filter unit of the present embodiment is low pass filter (LPF, Low Pass Filter), in other embodiments of the present invention, also can adopt any one filter existing, such as intermediate-frequency filter.
Composition graphs 3, specifically describes the workflow of intermediate frequency filtering device.
S1, be digital medium-frequency signal by analog to digital converter 001 by an analog if signal collection, and be sent to digital mixer 003.
S2, digital oscillator 002 produce N number of oscillator signal with different frequent points information, and N number of oscillator signal with different frequent points information is sent to digital mixer 003; Wherein, N be greater than 1 integer, N number of oscillator signal with different frequent points information is the first oscillator signal f with the first frequency point information
n, there is the first oscillator signal f of the second frequency point information
n+1there is the N oscillator signal f of N frequency point information
n+N.
In one embodiment, N can equal 1.
S3, as shown in Figure 3, digital mixer 003 is according to f
ndigital medium-frequency signal is down-converted to the first fundamental frequency signal, according to f
n+1digital medium-frequency signal is down-converted to the second fundamental frequency signal ... according to f
n+Ndigital medium-frequency signal is down-converted to N fundamental frequency signal (such as, the first oscillator signal f
ncarry out mixing with digital medium-frequency signal thus down-convert to 0 frequently, namely obtaining the first fundamental frequency signal, the second oscillator signal f
n+1carry out mixing with digital medium-frequency signal thus down-convert to 0 frequently, namely obtaining the second fundamental frequency signal ... the like, N oscillator signal f
n+Ncarry out mixing with digital medium-frequency signal thus down-convert to 0 frequently, namely obtaining N fundamental frequency signal.Or, in other implementations, digital medium-frequency signal is down-converted to baseband signal.)。The value of exemplarily getting N in Fig. 3 is 4, is not construed as limiting the present invention.
S4, low pass filter 004 carry out low-pass filtering to the first fundamental frequency signal to N fundamental frequency signal according to resolution bandwidth is parallel, thus obtain the filtering signal of corresponding first frequency to N frequency.
In said process, digital medium-frequency signal to be down-converted to the first fundamental frequency signal according to the first oscillator signal, according to the second oscillator signal, digital medium-frequency signal is down-converted to the second fundamental frequency signal by digital mixer 003 ... the process control according to N oscillator signal digital medium-frequency signal being down-converted to N fundamental frequency signal completes within a clock cycle of analog to digital converter 001.
In one embodiment, the operating clock cycle of analog to digital converter 001 is T, and the operating clock cycle of digital oscillator 002 is T/N.
Digital mixer 003 adopts time division multiplexing within a clock cycle of analog to digital converter 001, and (time division multiplexing, i.e. Time-Division Multiplexing, TDM are the multiplexing techniques of a kind of numeral or simulation.Use this technology, plural signal or data flow can simultaneously transmission over communication lines, and it shows as the subchannel of same communication channel.But physically, signal still takies physical channel in turn.Time-domain is divided into some segments of loop cycle, and every section of time span is fixing, and each period is used for transmission one sub-channels.) mode N number of digital medium-frequency signal correspondence is down-converted to N number of fundamental frequency signal (according to the first oscillator signal, digital medium-frequency signal is down-converted to the first fundamental frequency signal ... the process control according to N oscillator signal digital medium-frequency signal being down-converted to N fundamental frequency signal completes within a clock cycle of digital oscillator unit).
In one embodiment, particularly, analog to digital converter 001 carries out work with the work clock of 40MHz, is digital medium-frequency signal by the analog if signal collection be carried near 10.7MHz; Digital oscillator 002 produces with the work clock of 160MHz the oscillator signal that 4 have different frequent points information, is respectively f
n=10.7MHz, f
n+1=10.6MHz, f
n+2=10.5MHz, f
n+3=10.4MHz, and the oscillator signal that these 4 have different frequent points information is sent to digital mixer 003; Digital mixer 003 has the oscillator signal of different frequent points information according to these 4, within the clock cycle of 1 40MHz, in the clock cycle of also i.e. 4 160MHz, (namely digital mixer 003 is according to f the digital medium-frequency signal near 10.7MHz to be down-converted to 4 corresponding fundamental frequency signals
n=digital medium-frequency signal is down-converted to the first fundamental frequency signal, according to f by 10.7MHz oscillator signal
n+1=digital medium-frequency signal is down-converted to the second fundamental frequency signal by 10.6MHz oscillator signal, according to f
n+2=digital medium-frequency signal is down-converted to the 3rd fundamental frequency signal by 10.5MHz oscillator signal, according to f
n+3=digital medium-frequency signal is down-converted to the 4th fundamental frequency signal by 10.4MHz oscillator signal; Low pass filter 004 carries out filtering according to resolution bandwidth is parallel to these 4 fundamental frequency signals, thus in the sampling clock cycle of a 40MHz, obtain the filtering signal of 4 frequencies.
In one embodiment, the intermediate-frequency filter etc. meeting RBW bandwidth also can be adopted to carry out filtering to fundamental frequency signal.
Best prior art adopts FFT to scan little RBW, though but to consume Storage and Processing resource too much for the fast FFT of speed, be not suitable for FPGA or DSP use when resource anxiety.And adopt parallel scan technology of the present invention, under current less resource consumption, the sweep speed faster under little RBW can be completed.The present invention creatively uses the technology of parallel scan, frequency spectrograph is reduced the sweep time under identical RBW exponentially, thus adds fast scan speed, optimize Measuring Time.Use the technology that parallel DDC scans, the effect simultaneously using many intermediate-frequency channels can be reached, make the entire scan time become to reduce several fold, add fast scan speed.
Summary of the invention
According to a first aspect of the invention, the invention provides a kind of intermediate frequency filtering method, comprise the steps:
S1, be digital medium-frequency signal by analog to digital converter unit by an analog if signal collection, and be sent to digital mixer unit;
S2, being walked abreast by digital oscillator unit produces N number of oscillator signal with different frequent points information, and by N number of oscillator signal transmitted in parallel with different frequent points information to digital mixer unit; Wherein, N be greater than 1 integer or N equal 1 (N number of oscillator signal with different frequent points information be have the first oscillator signal of the first frequency point information, have the second oscillator signal of the second frequency point information ... there is the N oscillator signal of N frequency point information);
Digital medium-frequency signal to be down-converted to corresponding N number of fundamental frequency signal according to N number of oscillator signal with different frequent points information and (digital medium-frequency signal is down-converted to the first fundamental frequency signal according to the first oscillator signal, according to the second oscillator signal, digital medium-frequency signal is down-converted to the second fundamental frequency signal by S3, digital mixer unit ... according to N oscillator signal, digital medium-frequency signal is down-converted to N fundamental frequency signal);
S4, intermediate-frequency filter unit carry out filtering according to resolution bandwidth is parallel to N number of fundamental frequency signal (the first fundamental frequency signal is to N fundamental frequency signal), thus obtain the filtering signal (namely to N fundamental frequency signal, filtering is carried out to the first fundamental frequency signal, thus obtain the filtering signal of corresponding first frequency to N frequency) of corresponding N number of frequency.
In one embodiment, the operating clock cycle of analog to digital converter unit is T, and the operating clock cycle of digital oscillator unit is T/N.
In one embodiment, digital medium-frequency signal correspondence is down-converted to N number of fundamental frequency signal and (according to the first oscillator signal, digital medium-frequency signal is down-converted to the first fundamental frequency signal by digital mixer unit within a clock cycle of analog to digital converter unit ... the process control according to N oscillator signal digital medium-frequency signal being down-converted to N fundamental frequency signal completes within a clock cycle of analog to digital converter unit).
In one embodiment, digital medium-frequency signal is down-converted to fundamental frequency signal according to oscillator signal by digital mixer unit.
In one embodiment, the method also comprises the acquisition process of analog if signal, and (so just constituting the scan method of the whole spectrum instrument), detailed step is as follows.
Step one, to be gathered by signal gathering unit and to process external signal, and the external signal after process is sent to analog frequency mixing unit.
Step 2, produce local oscillation signal be sent to analog frequency mixing unit by local oscillation signal unit, control simulation mixing unit utilizes local oscillation signal to carry out mixing to the external signal after process thus obtains the analog if signal of sampling for analog to digital converter unit.
Step 3, be digital medium-frequency signal by analog to digital converter unit by an analog if signal collection, and be sent to digital mixer unit; Walked abreast by digital oscillator unit and produce N number of oscillator signal with different frequent points information, and by N number of oscillator signal transmitted in parallel with different frequent points information to digital mixer unit; Wherein, N be greater than 1 integer or N equal 1 (N number of oscillator signal with different frequent points information be have the first oscillator signal of the first frequency point information, have the second oscillator signal of the second frequency point information ... there is the N oscillator signal of N frequency point information); Digital medium-frequency signal to be down-converted to corresponding N number of fundamental frequency signal according to N number of oscillator signal with different frequent points information and (digital medium-frequency signal is down-converted to the first fundamental frequency signal according to the first oscillator signal, according to the second oscillator signal, digital medium-frequency signal is down-converted to the second fundamental frequency signal by digital mixer unit ... according to N oscillator signal, digital medium-frequency signal is down-converted to N fundamental frequency signal); Intermediate-frequency filter unit carries out filtering according to resolution bandwidth is parallel to N number of fundamental frequency signal (the first fundamental frequency signal is to N fundamental frequency signal), thus obtain the filtering signal (namely to N fundamental frequency signal, filtering is carried out to the first fundamental frequency signal, thus obtain the filtering signal of corresponding first frequency to N frequency) of corresponding N number of frequency.
Step 4, by detection unit, detection is carried out to the filtering signal that intermediate frequency filter cell produces and operate thus outputed signal;
Step 5, receive the output signal that produces of detection unit by display unit thus produce display result.
According to a second aspect of the invention, the invention provides a kind of intermediate frequency filtering device, comprising: digital oscillator unit, be connected to digital mixer unit, produce N number of oscillator signal with different frequent points information, and N number of oscillator signal with different frequent points information is sent to digital mixer unit; Wherein, N is greater than 1 integer equaled (N number of oscillator signal with different frequent points information is first oscillator signal with the first frequency point information ... there is the N oscillator signal of N frequency point information); Digital mixer unit, receive digital medium-frequency signal, according to N number of oscillator signal with different frequent points information, digital medium-frequency signal is down-converted to corresponding N number of fundamental frequency signal and (according to the first oscillator signal, digital medium-frequency signal is down-converted to the first fundamental frequency signal ... according to N oscillator signal, digital medium-frequency signal is down-converted to N fundamental frequency signal); Filter cell, is connected to digital mixer unit, carries out filtering, thus obtain the filtering signal of corresponding first frequency to N frequency according to resolution bandwidth is parallel to N number of fundamental frequency signal (the first fundamental frequency signal is to N fundamental frequency signal).
In one embodiment, intermediate frequency filtering device also comprises analog to digital converter unit, is connected to digital mixer unit, is digital medium-frequency signal, and is sent to digital mixer unit by an analog if signal collection; The operating clock cycle of analog to digital converter unit is T, and the operating clock cycle of digital oscillator unit is T/N.
In one embodiment, digital medium-frequency signal correspondence is down-converted to N number of fundamental frequency signal and (digital medium-frequency signal is down-converted to the first fundamental frequency signal according to the first oscillator signal, according to the second oscillator signal, digital medium-frequency signal is down-converted to the second fundamental frequency signal by digital mixer unit within a clock cycle of analog to digital converter unit ... the process control according to N oscillator signal digital medium-frequency signal being down-converted to N fundamental frequency signal completes within a clock cycle of analog to digital converter unit).
According to a third aspect of the invention we, the invention provides a kind of frequency spectrograph, comprise above-mentioned intermediate frequency filtering device.
In the present invention, ADC only once gathers the operation of digital medium-frequency signal, DDC is completed within a clock cycle of ADC, to N oscillator signal, digital medium-frequency signal is down-converted to first to N fundamental frequency signal according to first, then carry out the operation of intermediate frequency filtering to first to N fundamental frequency signal by intermediate-frequency filter.By the present invention, use the technology that parallel DDC scans, the effect simultaneously using many intermediate-frequency channels can be reached, make the entire scan time become to reduce several fold, add fast scan speed, optimize Measuring Time.
Beneficial effect of the present invention is, adopts parallel scan technology of the present invention, under current less resource consumption, can complete the sweep speed faster under little RBW.
Accompanying drawing explanation
Fig. 1 is the principle schematic of the intermediate frequency filtering of prior art;
Fig. 2 is the structural representation of the intermediate frequency filtering device of the embodiment of the present invention one;
Fig. 3 is the principle schematic of intermediate frequency filtering device of the present invention;
Fig. 4 is the structural representation of the intermediate frequency filtering device of the embodiment of the present invention two;
Fig. 5 is the structural representation of the frequency spectrograph of the embodiment of the present invention three.
Embodiment
By reference to the accompanying drawings the present invention is described in further detail below by embodiment.
Embodiment one:
Embodiment two:
Be illustrated in figure 4 the structural representation of the intermediate frequency filtering device of the present embodiment, comprise analog to digital converter (i.e. ADC) 101, numerically-controlled oscillator unit (being made up of N number of numerically-controlled oscillator) 102, digital mixer unit (being made up of N number of digital mixer) 103 and intermediate-frequency filter unit (being made up of N number of intermediate-frequency filter) 104, wherein, N be greater than 1 integer.
Composition graphs 3, specifically describes the workflow of intermediate frequency filtering device.
S1, be digital medium-frequency signal by analog to digital converter 101 by an analog if signal collection, and be sent to digital mixer unit 103.
S2, digital oscillator unit 102 produce N number of oscillator signal (N number of digital oscillator respectively produces the oscillator signal that has certain frequency point information) with different frequent points information, and N number of oscillator signal with different frequent points information is sent to digital mixer unit 103; N number of oscillator signal with different frequent points information is the first oscillator signal f with the first frequency point information
n, there is the first oscillator signal f of the second frequency point information
n+1there is the N oscillator signal f of N frequency point information
n+N.
S3, as shown in Figure 3, digital mixer unit 103 is according to f
ndigital medium-frequency signal is down-converted to the first fundamental frequency signal, according to f
n+1digital medium-frequency signal is down-converted to the second fundamental frequency signal ... according to f
n+Ndigital medium-frequency signal is down-converted to N fundamental frequency signal, and (that is, digital medium-frequency signal is respectively down-converted to fundamental frequency signal according to a certain oscillator signal by N number of digital mixer.First oscillator signal f
ncarry out mixing with digital medium-frequency signal thus down-convert to 0 frequently, namely obtaining the first fundamental frequency signal, the second oscillator signal f
n+1carry out mixing with digital medium-frequency signal thus down-convert to 0 frequently, namely obtaining the second fundamental frequency signal ... the like, N oscillator signal f
n+Ncarry out mixing with digital medium-frequency signal thus down-convert to 0 frequently, namely obtaining N fundamental frequency signal).The value of exemplarily getting N in Fig. 3 is 4, is not construed as limiting the present invention.
S4, intermediate-frequency filter unit 104 carry out intermediate frequency filtering to the first fundamental frequency signal to N fundamental frequency signal according to resolution bandwidth, thus obtain the filtering signal (N number of intermediate-frequency filter respectively according to resolution bandwidth to fundamental frequency signal carry out intermediate frequency filtering) of corresponding first frequency to N frequency.
In said process, digital medium-frequency signal to be down-converted to the first fundamental frequency signal according to the first oscillator signal, according to the second oscillator signal, digital medium-frequency signal is down-converted to the second fundamental frequency signal by digital mixer unit 103 ... the process control according to N oscillator signal digital medium-frequency signal being down-converted to N fundamental frequency signal completes within a clock cycle of analog to digital converter 101.
In one embodiment, the operating clock cycle of analog to digital converter 101 is T, and the operating clock cycle of digital oscillator unit 102 is T/N.
In one embodiment, particularly, the work clock of analog to digital converter 101 is 40MHz, and will be carried on analog if signal collection near 10.7MHz is digital medium-frequency signal; Digital oscillator unit 102 produces with the work clock of 160MHz the oscillator signal that 4 have different frequent points information, is respectively f
n=10.7MHz, f
n+1=10.6MHz, f
n+2=10.5MHz, f
n+3=10.4MHz, and the oscillator signal that these 4 have different frequent points information is sent to digital mixer unit 103; Digital mixer unit 103 has the oscillator signal of different frequent points information according to these 4, within the clock cycle of 1 40MHz, in the clock cycle of also i.e. 4 160MHz, (namely digital mixer unit 103 is according to oscillator signal f the digital medium-frequency signal near 10.7MHz to be down-converted to 4 corresponding fundamental frequency signals
n(01.7MHz) digital medium-frequency signal is down-converted to the first fundamental frequency signal, according to oscillator signal f
n+1(10.6MHz) digital medium-frequency signal is down-converted to the second fundamental frequency signal, according to oscillator signal f
n+2(10.5MHz) digital medium-frequency signal is down-converted to the 3rd fundamental frequency signal, according to oscillator signal f
n+3(0.4MHz) digital medium-frequency signal is down-converted to the 4th fundamental frequency signal; Intermediate-frequency filter unit 104 carries out filtering according to resolution bandwidth is parallel to these 4 fundamental frequency signals, thus in the sampling clock cycle of a 40MHz, obtain the filtering signal of 4 frequencies.
Best prior art adopts FFT to scan little RBW, though but to consume Storage and Processing resource too much for the fast FFT of speed, be not suitable for FPGA or DSP use when resource anxiety.And adopt parallel scan technology of the present invention, under current less resource consumption, the sweep speed faster under little RBW can be completed.The present invention creatively uses the technology of parallel scan, frequency spectrograph is reduced the sweep time under identical RBW exponentially, thus adds fast scan speed, optimize Measuring Time.Use the technology that parallel DDC scans, the effect simultaneously using many intermediate-frequency channels can be reached, make the entire scan time become to reduce several fold, add fast scan speed.
In other embodiments of the invention, intermediate frequency filtering device can only include a digital mixer, digital oscillator, a filter; Or intermediate frequency filtering device can comprise a digital mixer, N number of digital oscillator, N number of filter; Or intermediate frequency filtering device can comprise N number of digital mixer, digital oscillator, a N number of filter; Or intermediate frequency filtering device can comprise a digital mixer, N number of digital oscillator, a filter; Or digital mixer, the mode such as digital oscillator, N number of filter.As long as it will be appreciated by those skilled in the art that these modes are based on design of the present invention, then belong to simple replacement.
Embodiment three:
Be illustrated in figure 5 the structural representation of the frequency spectrograph of the present embodiment, wherein, signal gathering unit comprises attenuator (att, attenuator) 200, first low pass filter 110; Mixing unit comprises frequency mixer 300 (Mixer), intermediate frequency amplifier 410, if bandpas filter (Analog Filter) 140; Local oscillation signal unit comprises local oscillator (LO, Local Oscillator) 820; Intermediate frequency filtering unit (i.e. intermediate frequency filtering device) 120 comprises analog to digital converter (ADC, Analog-Digital Converter) 1201, numerically-controlled oscillator (i.e. NCO) 1202, digital mixer 1203 and low pass filter 1204; Detection unit comprises envelope detector 500; Display unit comprises video filtering (VBW, Video Band Width) device 130, display 600.
The workflow of frequency spectrograph is described in detail below in conjunction with Fig. 3 and Fig. 5.
Step one, original input signal (i.e. external signal), first through attenuator 200, are sent to frequency mixer 300 through the first low pass filter 110 subsequently.
Step 2, local oscillator 820 produce local oscillation signal f
lOand be sent to frequency mixer 300, signal from the first low pass filter 110 is with the local oscillation signal phase mixing from local oscillation signal unit (i.e. local oscillator 820) thus obtain mixed frequency signal (i.e. measured signal), mixed frequency signal is through intermediate frequency amplifier 410 and if bandpas filter 140, be sent to intermediate frequency filtering unit after in the free transmission range that mixed frequency signal drops on analog intermediate frequency band pass filter 140, digital signal will be sampled as by analog to digital converter 1201 and do further Digital IF Processing.
The analog to digital converter 1201 of step 3, intermediate frequency filtering unit is sampled mixed frequency signal convert thereof into digital medium-frequency signal, digital medium-frequency signal is sent to digital mixer 1203.
Step 4, digital oscillator 1202 produce N number of oscillator signal with different frequent points information, and N number of oscillator signal with different frequent points information is sent to digital mixer 1203; Wherein, as shown in Figure 5, getting N in the present embodiment is 3, is not construed as limiting the present invention, N be greater than 1 integer, N number of oscillator signal with different frequent points information is the first oscillator signal f with the first frequency point information
n, there is the second oscillator signal f of the second frequency point information
n+1, there is the 3rd oscillator signal f of the 3rd frequency point information
n+2, there is the 4th oscillator signal f of the 4th frequency point information
n+3.As shown in Figure 5, digital mixer is according to f
ndigital medium-frequency signal is down-converted to the first fundamental frequency signal, according to f
n+1digital medium-frequency signal is down-converted to the second fundamental frequency signal, according to f
n+2digital medium-frequency signal is down-converted to the 3rd fundamental frequency signal; Mixed frequency signal IF drops in the free transmission range of low pass filter 1204, then mixed frequency signal IF can be further processed, according to variable-resolution bandwidth (RBW, Resolution Band With), low pass filter 1204 obtains the filtering signal meeting current RBW, namely low pass filter 1204 carries out intermediate frequency filtering to the first fundamental frequency signal to the 4th fundamental frequency signal according to resolution bandwidth, thus obtains the filtering signal of corresponding first frequency to the 4th frequency.The detailed process of step 4 can refer to embodiment two.
Step 5, the filtering signal meeting current RBW are sent to video filter 130 by the output signal after envelope detector 500 calculates signal amplitude.
Step 6, output signal after video filter 130 be shown device 600 receive thus produces show result.
In said process, digital medium-frequency signal is down-converted to the first fundamental frequency signal according to the first oscillator signal by digital mixer 1203 ... the process control according to N oscillator signal digital medium-frequency signal being down-converted to N fundamental frequency signal completes within a clock cycle of analog to digital converter 1201.
Afterwards, the scanning process of frequency spectrograph in the next ADC clock cycle is repeated.
Best prior art adopts FFT to scan little RBW, though but to consume Storage and Processing resource too much for the fast FFT of speed, be not suitable for FPGA or DSP use when resource anxiety.And adopt parallel scan technology of the present invention, under current less resource consumption, the sweep speed faster under little RBW can be completed.The present invention creatively uses the technology of parallel scan, frequency spectrograph is reduced the sweep time under identical RBW exponentially, thus adds fast scan speed, optimize Measuring Time.Use the technology that parallel DDC scans, the effect simultaneously using many intermediate-frequency channels can be reached, make the entire scan time become to reduce several fold, add fast scan speed.
Above content is in conjunction with concrete execution mode further description made for the present invention, can not assert that specific embodiment of the invention is confined to these explanations.For general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, some simple deduction or replace can also be made.
Claims (10)
1. an intermediate frequency filtering method, is characterized in that, comprising:
Be digital medium-frequency signal by analog to digital converter unit by an analog if signal collection, and be sent to digital mixer unit;
Walked abreast by digital oscillator unit and produce N number of oscillator signal with different frequent points information, and by described N number of oscillator signal transmitted in parallel with different frequent points information to digital mixer unit; Wherein, N be more than or equal to 1 integer (N number of oscillator signal with different frequent points information is first oscillator signal with the first frequency point information ... there is the N oscillator signal of N frequency point information);
Described digital medium-frequency signal is down-converted to corresponding N number of fundamental frequency signal according to described N number of oscillator signal with different frequent points information and (according to described first oscillator signal, described digital medium-frequency signal is down-converted to the first fundamental frequency signal by digital mixer unit ... according to described N oscillator signal, described digital medium-frequency signal is down-converted to N fundamental frequency signal);
Intermediate-frequency filter unit carries out filtering according to resolution bandwidth is parallel to described N number of fundamental frequency signal (described first fundamental frequency signal is to described N fundamental frequency signal), thus obtains the filtering signal of corresponding N number of frequency.
2. the method for claim 1, is characterized in that, the operating clock cycle of described analog to digital converter unit is T, and the operating clock cycle of described digital oscillator unit is T/N.
3. the method for claim 1, it is characterized in that, described digital medium-frequency signal correspondence is down-converted to N number of fundamental frequency signal and (according to the first oscillator signal, described digital medium-frequency signal is down-converted to the first fundamental frequency signal by described digital mixer unit within a clock cycle of described analog to digital converter unit ... the process control according to described N oscillator signal described digital medium-frequency signal being down-converted to N fundamental frequency signal completes within a clock cycle of analog to digital converter unit).
4. the method for claim 1, is characterized in that, described digital medium-frequency signal is down-converted to fundamental frequency signal according to oscillator signal by described digital mixer unit.
5. the method as described in any one of Claims 1-4, is characterized in that, also comprises the acquisition process of described analog if signal:
Gathered by signal gathering unit and process external signal, and the external signal after process is sent to analog frequency mixing unit;
By analog frequency mixing unit mixing carried out to the external signal after described process thus obtain the analog if signal of sampling for analog to digital converter unit.
6. method as claimed in claim 5, is characterized in that, also comprise:
Carry out detection by detection unit to the described filtering signal that described intermediate-frequency filter unit produces operate thus outputed signal;
Receive the output signal that produces of detection unit by display unit thus produce display result.
7. an intermediate frequency filtering device, is characterized in that, comprising:
Digital oscillator unit, is connected to digital mixer unit, produces N number of oscillator signal with different frequent points information, and N number of oscillator signal with different frequent points information is sent to digital mixer unit; Wherein, N is greater than 1 integer equaled (N number of oscillator signal with different frequent points information is first oscillator signal with the first frequency point information ... there is the N oscillator signal of N frequency point information);
Digital mixer unit, receive digital medium-frequency signal, according to described N number of oscillator signal with different frequent points information, described digital medium-frequency signal is down-converted to corresponding N number of fundamental frequency signal and (according to described first oscillator signal, described digital medium-frequency signal is down-converted to the first fundamental frequency signal ... according to described N oscillator signal, described digital medium-frequency signal is down-converted to N fundamental frequency signal);
Filter cell, be connected to digital mixer unit, according to resolution bandwidth is parallel, filtering is carried out to described N number of fundamental frequency signal (described first fundamental frequency signal is to described N fundamental frequency signal), thus obtain the filtering signal of corresponding first frequency to N frequency.
8. device as claimed in claim 7, it is characterized in that, also comprise analog to digital converter unit, be connected to described digital mixer unit, is digital medium-frequency signal by an analog if signal collection, and is sent to described digital mixer unit.
9. device as claimed in claim 8, it is characterized in that, described digital medium-frequency signal correspondence is down-converted to N number of fundamental frequency signal and (according to the first oscillator signal, described digital medium-frequency signal is down-converted to the first fundamental frequency signal by described digital mixer unit within a clock cycle of described analog to digital converter unit ... the process control according to N oscillator signal described digital medium-frequency signal being down-converted to N fundamental frequency signal completes within a clock cycle of analog to digital converter unit).
10. a frequency spectrograph, is characterized in that, comprises the intermediate frequency filtering device as described in any one of claim 7 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510131603.XA CN104716921A (en) | 2015-03-24 | 2015-03-24 | Medium frequency filtering device, spectrometer and medium frequency filtering method |
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