KR100962252B1 - Interference suppress system - filter module - Google Patents

Abstract

The present invention relates to a filter module that suppresses an interference signal, and in particular, connects BPF and LNA in series so as to obtain sharp skirt characteristics and high isolation characteristics of a high frequency signal, and amplifies the signal of the LNA using a BSF and a directional filter. It is to provide a filter module that suppresses an interference signal having a compensation circuit capable of compensating for the ripple generated by the.

The technical configuration includes a filter module for passing or blocking a frequency signal of a predetermined band and suppressing an interference signal for amplifying the passed frequency signal; A compensation circuit for compensating for the ripple generated in the filter module suppressing the interference signal; Characterized in that comprises a.

Ripple, Insertion Loss, Compensation, Filter, ISS-FM, LNA, BPF, BSF

Description

Filter module which suppressed interference signal {INTERFERENCE SUPPRESS SYSTEM-FILTER MODULE}

The present invention relates to a filter module capable of processing an operating frequency as it is without using an up / down converter circuit in a repeater of a communication system, and more particularly, compensates for ripple and insertion loss and reduces component cost. The present invention relates to a filter module that suppresses an interference signal applicable to a high power wireless mobile communication repeater.

Generally, a filter is a passive element of an electronic circuit that passes only a signal waveform of a desired shape and filters out an unwanted waveform. A filter is a combination of inductance and capacitance, and has a very high frequency (VHF). In the band, a filter using a reherr or coaxial element is used, and a waveguide filter is used in a microwave band having a higher frequency.

The filter functions are classified into a low pass filter (LPF) for passing a signal below a certain frequency, a high pass filter (HPF) for passing a signal only above a certain frequency, and a band pass filter for passing a signal of a certain frequency band. BPF) and a band stop filter (hereinafter referred to as BSF) for stopping only signals of a certain frequency band.

Here, the signal passing through the filter has an insertion loss ripple characteristic, a skirt characteristic, and an isolation characteristic, wherein the insertion loss means power lost as the signal passes through the filter. The ripple characteristic is the difference between the lowest loss and the largest loss of the signal passing through the passband, the skirt characteristic is a measure of how well the passband and the stopband are distinguished, and the isolation characteristic is a spurious (out of passband) Spurious) refers to the degree of suppression of the signal.

That is, the insertion loss occurs when the signal S21 output from the input port 1 to the output port 2 in the pass band is less than 0 dB, and means that all of the input power does not go to the output.

In addition, the skirt characteristic means a characteristic that increases the clarity of the portion separating the pass band and the stop band, that is, the absolute value of the skirt slope, and increases the filtration characteristic according to the separation of the pass band and the stop band as the skirt characteristic increases. The higher the isolation characteristic, the better the ability to suppress spurious signals outside the passband.

However, since the insertion loss, the ripple characteristic, the skirt characteristic, and the isolation characteristic have a trade-off relationship depending on the order of the filter, the other characteristic becomes inversely worse when one is improved.

In other words, when the BPFs are connected in series, the pass and stop bands have the characteristics of the filters overlapping in series, thereby further suppressing both bands, resulting in poor insertion loss while increasing skirt and isolation characteristics. (Ripple) When the BPFs are combined in series, the ripples of the combined BPFs all add up, and thus, the total ripple characteristic of the combined filter module becomes worse.

Taken together, the skirt and isolation characteristics are better at higher absolute values, and the insertion loss and ripple characteristics are better at absolute values closer to “ZERO.” As described above, one or more BPFs of the same characteristic are serialized. When combined with, the skirt and isolation characteristics are improved by the number of BPFs that combine, but the insertion loss and ripple characteristics are conversely worse by the number.

In mobile communication, high channel separation is required, and conventional BPF cannot obtain sufficient skirt characteristics for channel separation at high carrier frequency, so the down converter has a low operating frequency. It converts to frequency (Intermediate Frequency = IF), and uses the SAW filter with excellent skirt characteristics in this IF to improve channel separation.

In order to increase the output of communication equipment, the gain must be increased. The signal passing through the amplifier not only amplifies the signal in the desired band but also amplifies the noise out of the desired band. There were problems such as unwanted oscillation in the amplifier.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a filter module that suppresses an interference signal, which is a filter or a filter module having sufficiently improved insertion loss, ripple, skirt, and isolation characteristics.

Another object of the present invention is to connect the BPF and LNA in series to ensure excellent skirt characteristics and isolation characteristics to suppress the interference signal (Interferece Signal), to compensate for the unwanted oscillation (Oscillation) to obtain a sufficient gain insertion loss It is an object of the present invention to provide a filter module that suppresses an interference signal that can be compensated for.

Another object of the present invention is to connect a compensation circuit equipped with a BSF and a directional filter in series with the BPF and LNA, a filter module that suppresses the interference signal that can compensate for the ripple caused by the series of filters having the same characteristics in series To provide.

In order to achieve the above object, the present invention provides a filter module for suppressing an interference signal that passes or blocks a frequency signal of a predetermined band, and amplifies the frequency signal passed therein; A compensation circuit for compensating for the ripple generated in the filter module suppressing the interference signal; It includes.

Preferably, the filter module for suppressing the interference signal includes two or more filters connected in series to pass and stop a frequency signal of a predetermined band, the plurality of filters having the same characteristics; A low noise amplifier provided to compensate for insertion loss generated according to a stop band in the filter; Characterized in that it comprises a.

Preferably, the plurality of filters are formed of any one of a dielectric or various types of metal cavities or DR-metal cavities or striplines.

Preferably, the plurality of filters are made of a dielectric or a combination of various types of metal cavities or dielectric resonant-metal cavities or striplines.

Preferably, the low noise amplifier has a gain according to insertion loss and is connected in series with the filter to compensate for insertion loss generated in the filter.

Preferably, the low noise amplifier is characterized in that it is provided to suppress the interference noise generated in the stop band.

Preferably, the compensation circuit is characterized by consisting of a filter for suppressing the amplitude of the ripple magnitude in the frequency band where the ripple is generated, to compensate for the ripple generated in the filter module suppressing the interference signal.

Preferably, the compensation circuit is characterized in that the BSF (Band Stop Filter) to block the amplitude as much as the size of the ripple generated frequency band and the ripple.

Preferably, the compensation circuit is a directional filter for blocking the amplitude of the ripple is generated by the frequency band and the magnitude of the ripple.

Preferably, the filter of the compensation circuit is characterized in that made to compensate for the ripple generated by the filter module suppressing the interference signal up to 2dB.

As described above, the present invention having the configuration as described above may have a sharp skirt characteristic and very large isolation characteristics by connecting BPFs in series so as to be used in a repeater, and amplifying the magnitude of a signal in a pass band by connecting LNAs. It is possible to improve the quality of the signal by compensating the circuit to compensate for the bad ripple by connecting several BPFs, so that the filter applied to the high output repeater without using expensive components It can be configured, resulting in a reduction of component cost, and lowering the unit cost and complexity of the configuration.

The present invention guarantees an intermediate frequency band by connecting BPFs in series, and can have isolation characteristics such as sharp skirt characteristics and signal separation, and at the same time, by inserting LNAs between BPFs connected in series, amplifying a signal while minimizing noise By combining multiple BPFs in series, it is possible to compensate for the bad ripple with a compensation circuit.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically showing a filter module suppressing an interference signal according to the present invention. As shown in the figure, an interference signal suppressed filter module (Interference Suppress System Filter Module) 10 includes a filter and an amplifier.

According to the present invention, when two or more filters are connected in series, the skirt and isolation characteristics according to two or more filter combinations are more than doubled when compared to one characteristic, but another important characteristic of the filter combination is insertion. Loss and ripple characteristics will more than double.

Therefore, in the present invention, first, a low noise amplifier (LNA) 11 is combined with one or more filters as shown in FIG. 1 to compensate for insertion loss and to obtain the total gain required by the filter module.

Here, Insertion Loss is one of the important characteristics of the filter, which means that the signal loses power as it passes through the filter.If S21 is less than 0 dB in the pass band, all input power is not output. In other words, it means that a loss of power has occurred. In other words, the loss as far as 0dB is called insertion loss.

At this time, the number of the low noise amplifier 11 is determined by the gain characteristic required in the filter module, and in order to reduce the noise figure (NF), which is also one of the important characteristics, the low noise amplifier 11 is the first of the filter modules. Fit in front of filter.

In this embodiment, a filter having the same characteristic is applied as a BPF (Band Pass Filter) 11, three filters 12 having the same characteristic are coupled in series, and four low noise amplifiers 11 are coupled in series. The filter module 10 is shown.

The above-described filter module 10 can be designed so that the skirt, isolation, and gain can be sufficiently used to be used in a high output repeater of 100 watts or more, which means that the interference noise signal outside the signal band can be sufficiently suppressed. .

Here, the ripple is increased according to the number of filters 12, and as a result, the ripple characteristic is deteriorated by a multiple of the number of the filters 12 to be coupled, thereby sufficiently compensating the total of the filter modules ISS-FM. Ensure that the ripple value is less than 2 dB.

The filter according to the present invention can use all kinds of filters, and depending on the implementation type, a lumped element, a transmission line, a microstrip or a stripline, a ceramic, or a dielectric (Dielectric) or Waveguide, Surface Acoustic Wave (SAW), MEMS, LTCC, FBAR and the like can be used.

Here, the lumped element is a device that can be made by soldering the L, C elements of lead or SMD to the PCB, a waveguide or stripline that can be implemented in consideration of coupling, resonance, multiple impedance connection in the case of several GHz or more is used.

In addition, the ceramic or the dielectric is a structural filter using the resonance according to the wavelength, it is made by using a high dielectric dielectric ceramic to reduce the electrical wavelength of the signal, to implement a smaller filter.

In addition, the waveguide is a case of directly using the resonance phenomenon, there is a Cavity method using a metal block or a ceramic method to insert a dielectric, SAW is used in the filter of portable equipment, such as mobile communication terminal pursuing small size, light weight, thin do.

2 is a view schematically showing a filter module suppressing an interference signal having a ripple compensation circuit according to the present invention. As shown in the figure, a ripple compensation circuit 20 is provided between the filter modules 10a and 10b which suppressed the interference signal according to the present invention.

Here, ripple means the difference between the highest point and the lowest point of the insertion loss in the signal pass band, which can be known by measuring S21, which is mainly expressed in dB.

Therefore, in order to perform the above-described compensation, the ripple compensation circuit 20 uses a band stop filter (BSF) as much as the band where the ripple exists to compensate for the ripple.

In other words, by using the BSF, the ripple is prevented from passing by the existing frequency band, thereby compensating for the ripple.

Alternatively, a compensation filter 20 includes a directional filter, which is configured to separate and combine a transmission frequency band and a reception frequency band when the transmission line is a 2-wire type, and separates the band where the ripple exists. And compensate.

3A and 3B are graphs schematically showing one filter output and two filter outputs. As shown in the figure, the S21 output graph in the case where two BPFs 10 are connected in series can be seen that the ripple has increased twice compared to the case where one BPF 10 is connected.

Here, the following characteristics are shown in the graph of S21 when one BPF 10 is provided.

Isolation = (D)-(A) = (-50dB)-(-5dB) =-45dB,

Skirt = (D)-(B) / delta F = -40 dB / delta F,

Ripple = (B)-(A) =-10dB + 5dB = -5dB,

Insertion Loss = (A) =-5 dB.

And the graph of S21 when two BPFs 10 are provided shows the following characteristic.

Isolation = (D)-(A) = -100dB + 10dB =-90dB

Skirt = (D)-(B) / delta F = -80 dB / delta F

Ripple = (B)-(A) = -20 + 10 =-10 dB

Insertion Loss = (A) =-10 dB

Comparing Equations 1 and 2, it can be seen that isolation, skirt, ripple, and insertion loss increase linearly in proportion to the number of BPFs 10, that is, N series filters having the same characteristics are serially increased. When combined with the following formula is established.

That is, in the case of combining N filters of the same characteristics in series, the isolation and skirt characteristics are increased by N times, but at the same time, the insertion loss and ripple characteristics are reduced by N times.

In addition, a low noise amplifier is provided to compensate for the insertion loss, which is amplified to compensate for -10 dB as shown in (A), and sufficiently amplifies a small input signal from the repeater circuit through the antenna. This function is always necessary to supply the power amplifier of the output stage.

Here, to compensate for the insertion loss-10 dB, the gain of the low noise amplifier must have + 10 dB, and the total loss is-10 dB + 10 dB = 0 dB, and in this process the gain of the low noise amplifier Has no effect on the isolation and skirt properties, so the improved properties are retained.

3 (A), (B), (C), and (D), even if they are all amplified by +10 dB, the isolation and skirt characteristics of these difference values are the same before or after amplification.

4 is a graph schematically illustrating an output of a compensation circuit applied to FIG. 2. As shown in the figure, a compensation circuit 20 according to the present invention is provided to compensate for the ripple characteristics as shown in FIGS. 3A and 3B.

Here, the compensation circuit 20 according to the present invention consists of a BSF or a directional filter, and compensates the frequency having the amplitude as much as the ripple generated in the frequency band where the ripple is generated to the stop band.

In addition, the ripple is compensated by connecting the series-connected filter and the BSF or directional filter in series.

FIG. 5 is a graph schematically illustrating an output of a filter module suppressing an interference signal having the compensation circuit of FIG. 2. As shown in the figure, in order to compensate for the ripple characteristics as shown in FIGS. 3A and 3B, the BSF or the directional filter of FIG. 4 was inserted and applied to the filter module 10 suppressing the interference signal.

That is, in the case of compensating ripple by connecting the compensation circuits 20 in series, the following Equation 4 is established.

A '= A + a =-10dB-10dB =-20dB

B '= B + b =-20dB-0dB =-20dB

C '= C + c =-100dB-0dB =-100dB

D '= D + d =-100dB-0dB =-100dB

In other words, when the compensation circuit 20 as shown in FIG. 4 is tuned to match the frequency band and frequency amplitude in which the ripple is generated, the ripple generated in the filters connected in series can be compensated for.

FIG. 6 schematically illustrates a stripline BSF applied to the compensation circuit of FIG. 2. FIG. 7 schematically illustrates a wave guide BSF applied to the compensation circuit of FIG. 2.

As shown in the figure, it can be seen that the BSF (Band Stop Filter) is designed as a stripline and a waveguide.

Here, the stripline is used to transmit a balance signal of + or-by using two metals, and various passive circuits may be implemented by changing or combining the structure itself, and the BSF used in the present invention may be implemented using the stripline and waveguide. Designed as a Wave Guide.

In addition, since the waveguide spreads only the lower surface of the waveguide, it is not transmitted in the full TEM mode, and because the signal is bent and leaked into the air, unnecessary loss may occur.

Therefore, it is preferable to use a stripline in which the same GND plate is formed on the upper and lower surfaces, because the field is vertically distributed on the upper and lower surfaces, so that the signal leaking while bending can be minimized, so that the perfect TEM Transmission in the mode is possible.

Here, in actual implementation, the waveguide only needs to care about the circuit pattern on the upper surface, but since the stripline has to make and assemble the pattern separately because the signal pattern is between the GND plates, the stripline is disadvantageous rather than the waveguide. Various materials may be used depending on the use.

8 is a graph schematically showing the output of the BSF according to FIGS. 6 and 7. As shown in the figure, an output for compensating the ripple characteristics of a BSF using a stripline or waveguide in the compensation circuit 20 according to the invention is shown.

Here, by using a stripline or a waveguide in the compensation circuit 20 according to the present invention, the BSF compensates the frequency having the amplitude as much as the ripple generated in the frequency band where the ripple occurs.

That is, if the frequency amplitude and the frequency band of the BSF are tuned to be the same as the band where the ripple occurs, the ripple may be compensated because the frequency band where the ripple occurs is caught in the stop band WIDTH.

9 is a diagram schematically illustrating a directional filter applied to the compensation circuit of FIG. 2, FIG. 10 is a diagram schematically illustrating a directional filter applied to the compensation circuit of FIG. 2, and FIG. 11 is a diagram illustrating a compensation circuit of FIG. 2. Figure schematically shows a directional filter applied to.

As shown, a directional filter is a filter that separates and combines a transmission frequency band and a reception frequency band when the transmission line is two-wire.

That is, the directional filter is implemented using the principle of coupling between lines, resonance on the line, and connection of multiple impedances, and an equivalent circuit analysis is possible due to the relationship between inductance (L) and capacitance (C). Do.

For a detailed description of the BSF and the directional filter, see Reference Microwave Filters, Impedance-Matching Networks, And Coupling Structures, Authors by George L, MATTHAEI, Leo YOUNG, and E.M.T. {12} Band Stop Filter in Chapter 12 of JONES, Published by ARTECH HOUSE, INC, 1980. and {2} Directional Filter in Chapter 14, detailed description thereof will be omitted.

12 is a graph schematically showing the output of the directional filter according to FIGS. 9 to 11. As shown in the figure, an output for compensating ripple characteristics using a directional filter in the compensation circuit 20 according to the present invention is shown.

Here, by using a stripline or a waveguide in the compensation circuit 20 according to the present invention, the BSF compensates the frequency having the amplitude as much as the ripple generated in the frequency band where the ripple occurs.

That is, if the frequency amplitude and the frequency band of the directional filter are tuned to be the same as the band where the ripple occurs, the ripple can be compensated because the frequency band where the ripple occurs is caught in the stop band WIDTH. .

FIG. 13 is a diagram illustrating an output of a filter module which suppresses an interference signal before the compensation circuit of FIG. 1 is applied. As shown in the figure, the output according to the filter combination according to the filter module suppressing the interference signal according to the present invention is shown in S21.

Here, the filter module filter that suppresses the interference signal uses a dielectric filter having a 900 MHz frequency band and a pass band of 25 MHz, and a low noise amplifier has a low noise figure (NF) and a gain of about 10 to 20 dB. Inexpensive devices were used.

In this case, the reflection loss S11 in which the signal input from the port 1 is output to the port 1 and the output signal S21 in which the signal input from the port 1 is output to the port 2 are illustrated.

In the figure, the skirt characteristics, isolation, gain, and return loss are all suitable for high power repeaters, but the amplitude at center frequency 881 MHz is 29.295 dB and the amplitude at 894 MHz is 23.739 dB, which is about 6 dB more than ripple. It can be seen that this has occurred, and a compensation circuit is required to compensate for the ripple.

14 is a diagram illustrating an output of a compensation circuit applied to FIG. 2. As shown in the figure, the output of the filter module and compensation circuit which suppressed the interference signal according to the present invention is shown in S21.

Here, the reflection loss S11 in which the signal input from port 1 of the compensation circuit is output back to port 1 and the output signal S21 in which the signal input from port 1 are output to port 2 are shown.

In addition, the stop band has a center frequency of 881.50 MHz, and the start frequency of the stop is designed to have a bandwidth of about 100 MHz with the end frequency of the stop at 931.50 MHz at 831.50 MHz.

Referring to the figure, it can be seen that the reflection loss S11 is less than about 1 to 2 dB, and the ripple has an amplitude capable of compensating the ripple of 6 dB shown in FIG.

FIG. 15 is a diagram illustrating an output of a filter module that suppresses an interference signal provided with the compensation circuit of FIG. 2. As shown in the figure, the measured values S21 and S11 of the filter module suppressing the interference signal to which the compensation circuit according to the present invention is applied are shown.

Here, the reflection loss S11 in which the signal input from port 1 of the compensation circuit is output back to port 1 and the output signal S21 in which the signal input from port 1 are output to port 2 are shown.

33.752dB is output at the center frequency 881.5MHz, 30.621dB is output at 894MHz, and about 3dB of ripple is generated, and the ripple is compensated by about 3dB through the compensation circuit. To further improve the ripple characteristic, the characteristics of the compensation circuit may be readjusted or a plurality of compensation circuits may be applied.

In the above described exemplary embodiments of the present invention by way of example, the scope of the present invention is not limited to this specific embodiment, and those skilled in the art within the scope described in the claims of the present invention Changes may be made as appropriate.

1 shows schematically a filter module suppressing an interference signal according to the invention.

Figure 2 schematically shows a filter module for suppressing an interference signal with a compensation circuit according to the present invention.

3 is a schematic illustration of a repeater with a filter module that suppresses an interference signal with the compensation circuit of FIG.

3A and 3B are graphs schematically showing one filter output and two filter outputs.

4 is a graph schematically showing the output of the compensation circuit applied to FIG.

FIG. 5 is a graph schematically showing an output of a filter module suppressing an interference signal having the compensation circuit of FIG. 2. FIG.

6 schematically illustrates a stripline BSF applied to the compensation circuit of FIG.

FIG. 7 shows schematically a waveguide BSF applied to a compensation circuit according to FIG. 2; FIG.

8 is a graph schematically showing the output of the BSF according to FIGS. 6 and 7.

9 schematically illustrates a directional filter applied to the compensation circuit of FIG.

10 is a schematic illustration of a directional filter applied to the compensation circuit of FIG.

FIG. 11 is a schematic illustration of a directional filter applied to the compensation circuit of FIG.

12 is a graph schematically showing the output of the directional filter according to FIGS. 9 to 11.

FIG. 13 illustrates an output of a filter module that suppresses an interference signal before the compensation circuit of FIG. 1 is applied. FIG.

14 shows the output of the compensation circuit applied in FIG.

FIG. 15 illustrates the output of a filter module that suppresses an interference signal with the compensation circuit of FIG. 2. FIG.

<Brief description of reference numerals for the main parts of the drawings>

10: filter module suppresses the interference signal

11: LNA 12: filter

20: compensation circuit 32, 42: power amplifier

51, 53: duplexer

Claims (10)

A filter module for suppressing an interference signal that passes or stops a frequency signal of a predetermined band and amplifies the frequency signal that has been passed; Compensation circuit for compensating for the ripple generated in the filter module that suppressed the interference signal; The filter module suppressing the interference signal, A plurality of filters passing and blocking frequency signals of a band, connected in series with each other, and having the same characteristics; A low noise amplifier inserted between the plurality of filters to compensate for insertion loss generated according to a stop band in the plurality of filters; Filter module for suppressing the interference signal provided with a compensation circuit comprising a. delete The method according to claim 1, And the plurality of filters are formed of any one of a dielectric or various types of metal cavities or DR-metal cavities or striplines. The method according to claim 1, And said plurality of filters comprises a dielectric or various types of metal cavities or a combination of dielectric resonance-metal cavities or striplines. The method according to claim 1, The low noise amplifier has a gain due to insertion loss, and the filter module suppressing the interference signal with a compensation circuit, characterized in that connected in series with the filter. The method according to claim 5, The low noise amplifier is a filter module for suppressing the interference signal having a compensation circuit, characterized in that the interference noise generated in the stop band is provided to minimize. delete delete delete delete

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