CN103684339A - A filtering method and a filtering apparatus for suppressing narrowband single-tone interference - Google Patents

Abstract

The invention provides a filtering method and a filtering apparatus for suppressing narrowband single-tone interference. The method comprises following steps: a step S1 in which a Notch filter reads an index value of a filter coefficient of the time-domain iterative formula of the Notch filter according to the difference between the center frequency of a carrier signal and narrowband single-tone interference frequency; a step 2 in which the Notch filter reads the filter coefficient of the time-domain iterative formula of the Notch filter according to index value; and a step 3 in which the Notch filter filters the carrier signal according to the time-domain iterative formula and filter coefficient calculation thereof and outputs a filtered result. The filtering method and the filtering apparatus for suppressing narrowband single-tone interference perform filtering by using the Notch filter to read the index value according to the difference between the center frequency of the carrier signal and narrowband single-tone interference frequency and the filter coefficient of the time-domain iterative formula of the Notch filter corresponding to the index value. The method and the apparatus have advantages of simple design, good filtering effect, and practicality.

Description

Suppress the filtering method that arrowband single-tone disturbs

Technical field

The present invention relates to communication technical field, particularly a kind of filtering method and device that suppresses arrowband single-tone interference.

Background technology

In communication process, due to a variety of causes, often have the irrelevant voltage of some and measured signal or electric current and exist, can affect like this Performance and quality of communication data.These signals are called interference, and it is divided into internal interference and external disturbance.

Internal interference, is interfering with each other between inner each parts of communication system, and this interference can be by the appropriate design of communicator, the rational deployment of parts, or takes quarantine measures etc. eliminated or weaken.

External disturbance, is to be produced by the factor of communication system outside, and common interference comprises:

1, machinery disturbs

Machinery disturbs the most serious, also very extensive.Mechanical oscillation meeting is moved wire in magnetic field, produces induced electromotive force.Suppress this class and disturb, with vibration reducing measure, as adopted shock-absorbing spring or vibration isolation rubber etc.

2, temperature interference

Due to excess Temperature, fluctuation and inhomogeneous, in detection, temperature often causes electronic component parameter to change or produces thermoelectric potential, thereby measurement result is caused to severe jamming.In engineering, generally adopt heat shielding method to suppress heat and disturb, as senser is packed in insulating box.In electronic measuring device, often adopt temperature-compensating measure, the impact with compensates on testing result.

3, electromagnetic interference

Due to the existence of the stray EM fields such as generator, motor and gas discharge device in factories and miness, the variation in electric field or magnetic field, can make the interference of electric or magnetic enter in electronic measuring device, causes interference signal.

In existing communication system, time domain transmits and disturbs through sneaking into arrowband single-tone after channel, and this arrowband single-tone disturbs as complex exponential form:

$i_l\left(t\right)=A_0{e}^{j{\mathrm{\φ}}_0}{e}^{j2\mathrm{\π}{f}_0(t+t_l)},$

Wherein, A ₀for the amplitude that single-tone disturbs, φ ₀for the initial phase that single-tone disturbs, f ₀frequency for known single-tone interference.

After sneaking into the time-domain signal arrival receiving terminal of single-tone interference, need to disturb and carry out filtering processing this arrowband single-tone, normally add filter module to realize Suppression of narrow band interference function, but the filtration module adding only can carry out filtering, poor effect to specific single interference conventionally.

Summary of the invention

The object of the invention is to propose a kind of simplicity of design, effect and preferably suppress the filtering method that arrowband single-tone disturbs.

For achieving the above object, the present invention proposes a kind of filtering method that arrowband single-tone disturbs that suppresses, comprise the following steps:

Step S1:Notch filter reads the index value of the iterative filter factor of this filter time domain according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency;

Step S2:Notch filter reads the iterative filter factor of this filter time domain according to described index value;

According to time domain, iterative and filter factor calculates described carrier signal is carried out to filtering output filtering result step S3:Notch filter.

Further, in the filtering method disturbing at above-mentioned inhibition arrowband single-tone, before described step S1, also comprise: Notch filter reinitializes before every frame filtering.

Further, in the filtering method disturbing at above-mentioned inhibition arrowband single-tone, before described step S1, also comprise:

According to the difference of carrier signal centre frequency and arrowband single-tone interference frequency, store index value corresponding to this difference filter factor iterative with this filter time domain.

Further, in the filtering method disturbing at above-mentioned inhibition arrowband single-tone, described step S2 specifically comprises:

Step S201:Notch filter obtains the memory address of the iterative filter factor of this filter time domain according to described index value, the memory address of described index value and this filter factor exists a kind of corresponding relation of mapping one by one;

Step S202:Notch filter reads the iterative filter factor of this filter time domain according to described memory address.

Further, in the filtering method disturbing at above-mentioned inhibition arrowband single-tone, the storage of the filter factor of described Notch filter adopts ROM, and the ROM degree of depth is 64, and data bit width is 96bit.

Separately, the invention provides a kind of filter that arrowband single-tone disturbs that suppresses, comprising:

Index value reading unit, reads the index value of the iterative filter factor of this filter time domain according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency for Notch filter;

Filter factor reading unit, reads the iterative filter factor of this filter time domain for Notch filter according to described index value; And

Filtering computing unit, for Notch filter, according to time domain, iterative and filter factor calculates described carrier signal is carried out to filtering output filtering result.

Further, in the filter disturbing at above-mentioned inhibition arrowband single-tone, described filter also comprises initialization unit, for Notch filter, before every frame filtering, reinitializes.

Further, in the filter disturbing at above-mentioned inhibition arrowband single-tone, described filter also comprises index value memory cell, for according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency, stores index value corresponding to this difference filter factor iterative with this filter time domain.

Further, in the filter disturbing at above-mentioned inhibition arrowband single-tone, described filter factor reading unit further comprises:

Memory address subelement, obtains the memory address of the iterative filter factor of this filter time domain according to described index value for Notch filter, the memory address of described index value and this filter factor exists a kind of corresponding relation of mapping one by one; And

Filter factor subelement, reads the iterative filter factor of this filter time domain for Notch filter according to described memory address.

Further, in the filter disturbing at above-mentioned inhibition arrowband single-tone, the storage of the filter factor of described Notch filter adopts ROM, and the ROM degree of depth is 64, and data bit width is 96bit.

Filtering method and device that the present invention suppresses arrowband single-tone interference read index value by Notch filter according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency, and thereby the filter time domain iterative filter factor corresponding with this index value carries out filtering, its simplicity of design, filter effect are better, very practical.

Accompanying drawing explanation

Fig. 1 is the schematic flow sheet that the present invention suppresses filtering method one embodiment of arrowband single-tone interference;

Fig. 2 is difference and the index value corresponding relation structural representation of centre carrier frequency and arrowband single-tone interference frequency;

Fig. 3 is the idiographic flow schematic diagram of Fig. 1 step S2;

Fig. 4 calculates the structural representation that complex multiplication realizes in Fig. 1 step S3;

Fig. 5 is the structural representation that the present invention suppresses filter one embodiment of arrowband single-tone interference.

Embodiment

Below in conjunction with accompanying drawing, describe the preferred embodiments of the present invention in detail.

The filtering method that the present invention suppresses arrowband single-tone interference adopts Notch filter to carry out filtering, and this Notch filter can only have a zero point on unit circle.In order reducing, to realize cost, to adopt first order IIR Notch filter effectively to suppress arrowband single-tone and disturb, the system function of this Notch filter is:

$\frac{\frac{1-j\tan \left(\frac{{\mathrm{\ω}}_0}{2}\right)}{1+\frac{\tan \left(\frac{B_{\mathrm{\ω}}}{2}\right)}{1+\cos \left({\mathrm{\ω}}_0\right)}-j\tan \left(\frac{{\mathrm{\ω}}_0}{2}\right)\sqrt{1-\frac{{\tan }^2\left(\frac{B_{\mathrm{\ω}}}{2}\right)}{{\sin }^2{\mathrm{\ω}}_0}}}-\frac{1+j\tan \left(\frac{{\mathrm{\ω}}_0}{2}\right)}{1+\frac{\tan \left(\frac{B_{\mathrm{\ω}}}{2}\right)}{1+\cos \left({\mathrm{\ω}}_0\right)}-j\tan \left(\frac{{\mathrm{\ω}}_0}{2}\right)\sqrt{1-\frac{{\tan }^2\left(\frac{B_{\mathrm{\ω}}}{2}\right)}{{\sin }^2{\mathrm{\ω}}_0}}}{z}^{-1}}{1-\frac{1-\frac{\tan \left(\frac{B_{\mathrm{\ω}}}{2}\right)}{1+\cos \left({\mathrm{\ω}}_0\right)}+j\tan \left(\frac{{\mathrm{\ω}}_0}{2}\right)\sqrt{1-\frac{{\tan }^2\left(\frac{B_{\mathrm{\ω}}}{2}\right)}{{\sin }^2{\mathrm{\ω}}_0}}}{1+\frac{\tan \left(\frac{B_{\mathrm{\ω}}}{2}\right)}{1+\cos \left({\mathrm{\ω}}_0\right)}-j\tan \left(\frac{{\mathrm{\ω}}_0}{2}\right)\sqrt{1-\frac{{\tan }^2\left(\frac{B_{\mathrm{\ω}}}{2}\right)}{{\sin }^2{\mathrm{\ω}}_0}}}{z}^{-1}}$

Wherein, ω ₀=2 π f ₀/ F _sfor digital Notch angular frequency, B _ω=2 π B/F _s, B is 3-dB Notch bandwidth, Fs is sample frequency.

Refer to Fig. 1, the filtering method that the present invention suppresses arrowband single-tone interference comprises the following steps:

Step S1:Notch filter reads the index value of the iterative filter factor of this filter time domain according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency;

Step S2:Notch filter reads the iterative filter factor of this filter time domain according to described index value;

According to time domain, iterative and filter factor calculates described carrier signal is carried out to filtering output filtering result step S3:Notch filter.

The present invention suppresses the filtering method employing Notch filter that arrowband single-tone disturbs, and its time domain is iterative is:

y(n)＝α ₁y(n-1)+β ₀x(n)+β ₁x(n-1) (1)

Wherein, α, β ₀, β ₁filter factor for Notch filter.

While realizing, different from the difference of arrowband single-tone interference frequency according to carrier signal centre frequency, this Notch filter selects different filter factors to carry out filtering.

Before described step S1, also comprise: Notch filter reinitializes before every frame filtering.

Notch filter Yi Zhengwei unit carries out filtering, and every frame starts, and Notch filter all needs to reinitialize (y (n)=0), adopts reception reset signal to reset to filter.Every frame all initialization has a benefit, can ignore the intrinsic error accumulation problem of iir filter.

From formula (1), Notch filter has three complex coefficients (being filter factor), this communication system is when centre carrier frequency is identical with arrowband single-tone interference frequency, receptivity can not be affected, without carrying out Notch filtering, but in order to guarantee system signal uniformity for the treatment of, also carry out filtering processing in this situation, filter coefficient is got α ₁=0, β ₀=1, β ₁=0, this filter coefficient adopts Q15 calibration, and 16 ' h7FFF represents 1 (the filter factor fixed point of floating number is about to filter factor and is multiplied by 2 ¹⁵after round, use 16bit binary number representation).

If during this communication system configuration carrier signal centre frequency, step value is 25KHz.Supposing the system exists 51 kinds of different filter factor combination situations (to comprise that filter factor is α ₁=0, β ₀=1, β ₁=0 situation).The bit wide of filter complex coefficient real part and imaginary part is 16bit, and filter coefficient needs the memory space of 51*3* (16+16) bit=612Byte altogether.

The filter factor storage of this filter adopts ROM, and the ROM degree of depth is 64, and data bit width is 96bit.In three complex coefficient ROM of filter, storage mode is:

D95-d80 α ₁real part, d79-d64 α ₁imaginary part; D63-d48 β ₀real part, d47-d32 β ₀imaginary part; D31-d16 β ₁real part, d15-d0 β ₁imaginary part.(real part of the filter factor of this filter and imaginary part adopt the rear bit wide of Q15 calibration to be 16bit)

Refer to Fig. 2, Fig. 2 is difference and the index value corresponding relation structural representation of centre carrier frequency and arrowband single-tone interference frequency.Before described step S1, also comprise:

According to the difference of carrier signal centre frequency and arrowband single-tone interference frequency, store index value corresponding to this difference filter factor iterative with this filter time domain.

During this communication system work, according to centre carrier frequency f and arrowband single-tone interference frequency f ₀difference (Δ f=f-f ₀) read index (Index) value.

Refer to Fig. 3, described step S2 specifically comprises:

Step S201:Notch filter obtains the memory address of the iterative filter factor of this filter time domain according to described index value, the memory address of described index value and this filter factor exists a kind of corresponding relation of mapping one by one;

For different communication systems, it is inconsistent that system inhibition arrowband single-tone disturbs the Notch filter adopting to have different filter factors combination quantity, be that index value Index is inconsistent, filter three complex coefficients (being filter factor) memory addresss in ROM (rom_address) are also inconsistent.But between this memory address rom_address and index value Index, there is the corresponding relation of mapping one by one, i.e. concrete mapping relations.

Step S202:Notch filter reads the iterative filter factor of this filter time domain according to described memory address.

As shown in table 1, Notch filter can read three complex coefficient α of filter, β according to described memory address from ROM ₀, β ₁, complete the selection to filter coefficient.

Three complex coefficients of table 1Notch filter are stored corresponding table in ROM

In described step S3, Notch filter is obtaining filter coefficient alpha, β ₀, β ₁after, by its substitution

Formula (1) y (n)=α ₁y (n-1)+β ₀x (n)+β ₁x (n-1) carries out computing, wherein, completes first respectively α ₁y (n-1), β ₀x (n), β ₁the complex multiplication operation of x (n-1).

Complex multiplication operation process can be represented by the formula:

C _i+jC _q＝(A _i+jA _q)*(B _i+jB _q)＝(A _iB _i-A _qB _q)+j(A _iB _q+A _qB _i) (2)

By formula (2), can find out that a complex multiplication needs four multiplication, a sub-addition and a subtraction.Specific implementation adopts adder and multiplier and takes advantage of and subtracts device, and complex multiplication operation result is DATA_OUT_I[31:0], DATA_OUT_Q[31:0].Filter factor adopts Q15 calibration, and after complex multiplication operation, multiplication DATA_OUT_I[30:15 is got in the output of IQ], DATA_OUT_Q[30:15].

Specific implementation structure as shown in Figure 4, α ₁y (n-1), β ₀x (n), β ₁the complex multiplication of x (n-1) the respectively output data of computing divides real part (high 16bit) and imaginary part (low 16bit) data to carry out respectively add operation again.The result output of add operation can realize and suppress arrowband single-tone interference function.

Refer to Fig. 5, the present invention also provides a kind of filter that arrowband single-tone disturbs that suppresses, comprise index value reading unit 10, filter factor reading unit 20 and filtering computing unit 30, described index value reading unit 10 reads the index value of the iterative filter factor of this filter time domain according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency for Notch filter; Described filter factor reading unit 20, reads the iterative filter factor of this filter time domain for Notch filter according to described index value; For Notch filter, according to time domain, iterative and filter factor calculates described carrier signal is carried out to filtering output filtering result described filtering computing unit 30.

Wherein, the present invention suppresses the filtering method employing Notch filter that arrowband single-tone disturbs, and its time domain is iterative is:

y(n)＝α ₁y(n-1)+β ₀x(n)+β ₁x(n-1) (1)

While realizing, different from the difference of arrowband single-tone interference frequency according to carrier signal centre frequency, this Notch filter selects different filter factors to carry out filtering.

Described filter also comprises initialization unit 40, for Notch filter, before every frame filtering, reinitializes.

Notch filter Yi Zhengwei unit carries out filtering, and every frame starts, and Notch filter all needs to reinitialize (y (n)=0), adopts reception reset signal to reset to filter.Every frame all initialization has a benefit, can ignore the intrinsic error accumulation problem of iir filter.

From formula (1), Notch filter has three complex coefficients (being filter factor), this communication system is when centre carrier frequency is identical with arrowband single-tone interference frequency, receptivity can not be affected, without carrying out Notch filtering, but in order to guarantee system signal uniformity for the treatment of, also carry out filtering processing in this situation, filter coefficient is got α ₁=0, β ₀=1, β ₁=0 (this filter coefficient adopts Q15 calibration, and 16 ' h7FFF represents 1).

If during this communication system configuration carrier signal centre frequency, step value is 25KHz.Supposing the system exists 51 kinds of different filter factor combination situations (to comprise that filter factor is α ₁=0, β ₀=1, β ₁=0 situation).The bit wide of filter complex coefficient real part and imaginary part is 16bit, and filter coefficient needs the memory space of 51*3* (16+16) bit=612Byte altogether.

The filter factor storage of this Notch filter adopts ROM, and the ROM degree of depth is 64, and data bit width is 96bit.In three complex coefficient ROM of filter, storage mode is:

D95-d80 α ₁real part, d79-d64 α ₁imaginary part; D63-d48 β ₀real part, d47-d32 β ₀imaginary part; D31-d16 β ₁real part, d15-d0 β ₁imaginary part.

Described filter also comprises index value memory cell 50, for according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency, stores index value corresponding to this difference filter factor iterative with this filter time domain.

Described filter factor reading unit 20 further comprises memory address subelement 202 and filter factor subelement 204, described memory address subelement 202 obtains the memory address of the iterative filter factor of this filter time domain according to described index value for Notch filter, the memory address of described index value and this filter factor exists a kind of corresponding relation of mapping one by one; Described filter factor subelement 204 reads the iterative filter factor of this filter time domain for Notch filter according to described memory address.

Than prior art, filtering method and device that the present invention suppresses arrowband single-tone interference read index value by Notch filter according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency, and thereby the filter time domain iterative filter factor corresponding with this index value carries out filtering, its simplicity of design, filter effect are better, very practical.

Here description of the invention and application is illustrative, not wants by scope restriction of the present invention in the above-described embodiments.Here the distortion of disclosed embodiment and change is possible, and for those those of ordinary skill in the art, the various parts of the replacement of embodiment and equivalence are known.Those skilled in the art are noted that in the situation that not departing from spirit of the present invention or substantive characteristics, and the present invention can be with other form, structure, layout, ratio, and realizes with other assembly, material and parts.In the situation that not departing from the scope of the invention and spirit, can carry out other distortion and change to disclosed embodiment here.

Claims (10)

1. suppress the filtering method that arrowband single-tone disturbs, it is characterized in that, comprise the following steps:

Step S1:Notch filter reads the index value of the iterative filter factor of this filter time domain according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency;

Step S2:Notch filter reads the iterative filter factor of this filter time domain according to described index value;

According to time domain, iterative and filter factor calculates described carrier signal is carried out to filtering output filtering result step S3:Notch filter.

2. the filtering method that inhibition according to claim 1 arrowband single-tone disturbs, is characterized in that, also comprises: Notch filter reinitializes before every frame filtering before described step S1.

3. the filtering method that inhibition according to claim 2 arrowband single-tone disturbs, is characterized in that, before described step S1, also comprises:

According to the difference of carrier signal centre frequency and arrowband single-tone interference frequency, store index value corresponding to this difference filter factor iterative with this filter time domain.

4. the filtering method that inhibition according to claim 1 arrowband single-tone disturbs, is characterized in that, described step S2 specifically comprises:

Step S201:Notch filter obtains the memory address of the iterative filter factor of this filter time domain according to described index value, the memory address of described index value and this filter factor exists a kind of corresponding relation of mapping one by one;

Step S202:Notch filter reads the iterative filter factor of this filter time domain according to described memory address.

5. the filtering method that inhibition according to claim 1 arrowband single-tone disturbs, is characterized in that, the filter factor storage of described Notch filter adopts ROM, and the ROM degree of depth is 64, and data bit width is 96bit.

6. suppress the filter that arrowband single-tone disturbs, it is characterized in that, comprising:

Index value reading unit, reads the index value of the iterative filter factor of this filter time domain according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency for Notch filter;

Filter factor reading unit, reads the iterative filter factor of this filter time domain for Notch filter according to described index value; And

Filtering computing unit, for Notch filter, according to time domain, iterative and filter factor calculates described carrier signal is carried out to filtering output filtering result.

7. the filter that inhibition according to claim 6 arrowband single-tone disturbs, is characterized in that, described filter also comprises initialization unit, for Notch filter, before every frame filtering, reinitializes.

8. the filter that inhibition according to claim 6 arrowband single-tone disturbs, it is characterized in that, described filter also comprises index value memory cell, for according to the difference of carrier signal centre frequency and arrowband single-tone interference frequency, store index value corresponding to this difference filter factor iterative with this filter time domain.

9. the filter that inhibition according to claim 6 arrowband single-tone disturbs, is characterized in that, described filter factor reading unit further comprises:

Memory address subelement, obtains the memory address of the iterative filter factor of this filter time domain according to described index value for Notch filter, the memory address of described index value and this filter factor exists a kind of corresponding relation of mapping one by one; And

Filter factor subelement, reads the iterative filter factor of this filter time domain for Notch filter according to described memory address.

10. the filter that inhibition according to claim 9 arrowband single-tone disturbs, is characterized in that, the filter factor storage of described Notch filter adopts ROM, and the ROM degree of depth is 64, and data bit width is 96bit.

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