CN201096883Y

CN201096883Y - High band digital tuning LC filter

Info

Publication number: CN201096883Y
Application number: CNU200720087869XU
Authority: CN
Inventors: 阮航; 陈泽宗; 郑瑞
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2007-10-31
Filing date: 2007-10-31
Publication date: 2008-08-06
Anticipated expiration: 2017-10-31

Abstract

The utility model relates to a high frequency band digital tuning LC filter. The high frequency band digital tuning LC filter is characterized in that the high frequency band digital tuning LC filter comprises an input analog switch, a four-band fixed filter group, an output analog switch, a tuning capacitor input controller, a PIN switch capacitor array group, a wave band selection input terminal, an in-band tuning code input terminal, a signal input terminal, and a signal output terminal; the tuning capacitor input controller is connected between the four-band fixed filter group and the PIN switch capacitor array group, and connected with wave band selection input terminal 6; the input analog switch and the output analog switch are respectively connected at the input terminal and the output terminal of the four-band fixed filter group. The 64 level digital control hopping frequency tuning filter of most of high frequency wave bands (5.9 to 31.7 MHz) can be realized. The high frequency band digital tuning LC filter can be used for the multi-frequency or frequency agile radar receiver filter part, thereby improving the signal noise ratio of the radar receiver.

Description

The digital tuning LC wave filter of high band

Technical field

The utility model relates to the technical field of receiver in the high-frequency ground wave radar, particularly relates to the digital tuning filter of the receiver that needs frequency agility filtering.

Background technology

Modern signal processing and electrical application technology field, the wave filter ingredient that is absolutely necessary, its topmost effect are separation signals, suppress to disturb.For general wave filter, in case component parameters determines that its filtering characteristic (centre frequency, bandwidth etc.) will be fixed up.But sometimes, we wish that bandpass filter has the adjustable characteristic of band connection frequency, and promptly parameters such as the centre frequency by changing wave filter, bandwidth allow wave filter can apply to various occasions more neatly.For traditional bandpass filter, we can realize by the value of adjusting elements such as resistance on its filtering loop, electric capacity, but in some occasion that need control automatically, when perhaps our inconvenience directly changed circuit structure and parameter by hand, this method obviously was infeasible.

Summary of the invention

The utility model is at the problems referred to above, a kind of digital tuning LC wave filter with high band of digital tuning function is provided, the centre frequency of this frequency agility wave filter changes with the variation of received signal, thereby can improve the signal to noise ratio (S/N ratio) of receiver effectively, make more high efficient and reliable of frequency hopping communications equipment.Simultaneously, this digital tuning wave filter can also effectively solve interference and the electromagnetic compatibility problem that multi-section frequency hopping communications equipment is communicated by letter simultaneously, under the condition of same bandwidth, increases tens of times capacity.

The technical scheme that the utility model provides is: a kind of digital tuning LC wave filter of high band, it is characterized in that: comprise the input analog switch, four wave band fixed filters groups, the output analog switch, tuning capacity input control, PIN switched capacitor array group, the band selection input end, tuning sign indicating number input end in the section, signal input part, signal output part, tuning capacity input control is connected between four wave band fixed filters groups and the PIN switched capacitor array group, and be connected with band selection input end 6, in band selection and section, under tuning yard the control, can realize the digital tuning filter action of 4 different-wavebands; Input analog switch, output analog switch are connected on the input end and the output of four wave band fixed filters groups respectively, control the gating of different-waveband FL-network in the four wave band fixed filters groups.The utility model can realize that finally 5.9MHz is to the 31.7MHz function of totally 64 grades of numerical control tuning filterings.

Described four wave band fixed filters groups are made up of the filter network of 4 dead center frequencies, and each network all is to comprise 4 coupling capacitances, three rank Chebyshev's type LC coupling resonance networks of 3 resonant capacitances and 3 resonant inductances.The squareness factor of this filter network algorithm curve is good, and the insertion loss is low.Design the different electric capacity and the size of inductance, can produce the different wave filter of centre frequency.All electric capacity, inductance are all selected patch capacitor, chip inductor for use.

Described PIN switched capacitor array group, constitute by 3 groups of identical PIN switched capacitor arrays of parameter, (the electric capacity size was than 8: 4: 2: 1), and control corresponding electric capacity inserts or the numerical control PIN switch that disconnects is formed by the capacitor of 4 different capabilities sizes for every group of capacitor array.Each PIN switch with+5V and-input control signal of 5V realizes the access or the disconnection of corresponding capacitance respectively.4 PIN switches are controlled 4 electric capacity break-makes independently, just can realize 16 grades of numerical control transfigurations.PIN switched capacitor array group inserts the resonance branch road of some filter networks in the four above-mentioned wave band fixed filters groups, can change the centre frequency of filter network, reaches tuning effect.

Described input analog switch and output analog switch adopt 4: 1 analog switch MAX4582L of two-way chip of a slice MAXIM company to realize.This model analog switch conducting resistance is little, and slewing rate is fast, and it is good that high frequency inserts indexs such as loss, shutoff isolation down, can satisfy requirement of the present utility model.

Described tuning capacity input control also is that the MAX4582L analog switch chip that adopts is realized.Two MAX4582L can finish the function of three tunnel 4: 1 analog switch gatings.

Design concept of the present utility model is such: each of digital bounce frequency filter grade centre frequency, all corresponding the tuning sign indicating number of scale-of-two of a 6bit.According to the value of circuit element parameter, can calculated in advance and debug out " the tuning sign indicating number-frequency table of comparisons ", again according to this table of comparisons and required centre frequency, from the parallel tuning code data of 6bit of importing of tuning sign indicating number input control end.Logical one and " 0 " are exported to each analog switch respectively to high 2 of tuning code data with the form of+3V and 0V level as the band selection signal, are used for choosing the filter network of a certain band limits in the four wave band fixed filters groups.A tuning coded signal in low 4 the conduct sections of tuning sign indicating number, logical one and " 0 " respectively with+5V and-the form control PIN switched capacitor array of 5V level, the electric capacity that makes it suitable capacity inserts four wave band fixed filters groups, reaches the function of adjusting the filter center frequency.Like this, select different filter networks (high 2) and resonance branch road to insert electric capacity (low 4 s') mode, can realize 64 grades of frequency hopping filtering of high frequency band by the tuning sign indicating number of 6bit.

The utility model is compared the following points advantage with existing digital tuning wave filter:

1. the utility model can be realized the digital tuning filtering of 5.9MHz to the 31.7MHz relative broad range, has covered the frequency of high frequency band substantially; Squareness factor was better than similar digital tuning wave filter less than 4.5: 1.

2. with respect to digital tuning wave filter or the active tuned filter of RC based on FPGA and varactor, the utility model is a LC passive coupling network owing to what adopt, has to design and produce simply stable performance, the advantage that cost is low.

3. the utility model applies in the radar receiver device, can change filtering characteristic fast as required, can improve the signal to noise ratio (S/N ratio) of radar receiver.

The parallel input of the tuning sign indicating number of major parameter index of the present utility model: 6bit; The filtering of 64 grades of numerical control frequency hoppings; Frequency range 5.9MHz is to 31.7MHz; Four band frequency scopes are respectively 5.9～7.9MHz, 7.8～11.0MHz, 10.6～16.9MHz, 16.2～31.7MHz; The scope of four sections filter network relative bandwidths is respectively 6.8～11.4%, 5.8～10.0%, 5.7～11.8%, 3.1～7.0%; Input, output impedance are 50 Ω; The 30dB squareness factor was less than 4.5: 1.

Description of drawings

Fig. 1 is the composition frame chart of the utility model embodiment.

Fig. 2 is an input analog switching circuit schematic diagram among the utility model embodiment.

Fig. 3 is four wave band fixed filters group circuit theory diagrams among the utility model embodiment.

Fig. 4 is an output analog switching circuit schematic diagram among the utility model embodiment.

Fig. 5 is tuning capacity Access Control circuit theory diagrams among the utility model embodiment.

Fig. 6 is PIN switched capacitor array group circuit theory diagrams among the utility model embodiment.

Embodiment

Below in conjunction with drawings and Examples, the utility model is described in further detail.

Referring to Fig. 1, the digital tuning LC wave filter of the high band of the utility model embodiment, comprise input analog switch 1, four wave band fixed filters group 2, output analog switch 3, tuning capacity input control 4, PIN switched capacitor array group 5, band selection input end 6, tuning sign indicating number input end 7 in the section, signal input part 8, signal output part 9.Tuning capacity input control 4 is connected between four wave band fixed filters groups 2 and the PIN switched capacitor array group 5, and be connected with band selection input end 6, in band selection input end 6 and section, under the control of tuning sign indicating number input end 7, can realize the digital tuning filter action of 4 different-wavebands; Input analog switch 1, output analog switch 3 are connected on the input end and the output of four wave band fixed filters groups 2 respectively, control the gating of different-waveband FL-network in the four wave band fixed filters groups 2.

Referring to Fig. 2, the input analog switch 1 among the utility model embodiment adopts the MAX4582L pattern to intend switch.Channel selecting control port A and B that the band selection signal BandSel0 of 2bit and BandSel1 are input to analog switch, the high-frequency signal of input is through selecting a certain road output from these 4 passages of BAND1A～BAND4A.

Referring to Fig. 3, four wave band fixed filters groups 2 among the utility model embodiment are made up of the filter network of 4 dead center frequencies.Each network all is to comprise 4 coupling capacitances, three rank Chebyshev's type LC coupling resonance networks of 3 resonant capacitances and 3 resonant inductances.The squareness factor of this resonator, filter network filtering die-away curve is good, and the insertion loss is low.X0-2, Y0-2, Z0-2, W0-2 links to each other with the circuit of tuning capacity input control 4, becomes the branch road additional capacitor so that obtain the victory of digit control.From the high-frequency signal of input analog switch 1 output terminal BANID1A～BAND4A output, can under such filter network, finish the filtering of particular centre frequency, filtered signal is exported to output analog switch 3 from BAND1B～BAND4B.

Referring to Fig. 4, the output analog switch 3 among the utility model embodiment, design proposal is similar to input analog switch 1, and with input analog switch 1 shared same MAX4582L chip.Export to output analog switch 3 through four wave band fixed filters groups, 2 filtered signals from BAND1B～BAND4B, from 3 outputs of output analog switch, finish whole filtering again.When the effect of output analog switch 3 mainly is a filter network job in four wave band fixed filters groups 2, shield of the influence of other three filter network capacitor and inductors to system.

Referring to Fig. 5, the control of 3 path analoging switch realization to three branch road additional capacitors of three rank LC filter networks in the four wave band fixed filters groups 2 is used in the tuning capacity Access Control 4 among the utility model embodiment, has adopted two MAX4582L analog switch chips.POINT1-3 connects the lumped capacitance of certain specific size of PIN switched capacitor array group output, this lumped capacitance inserts the X0-2 of four wave band fixed filters groups 2, Y0-2 under the selection of band selection signal BandSel0-1, Z0-2, a certain group of tributary port among the W0-2.

Referring to Fig. 6, PIN switched capacitor array group 5 among the utility model embodiment, the TUNE0-3 termination receive from the logical signal " 1 " of low 4 of digital tuning sign indicating number (tuning sign indicating number in both described section) or " 0 " (voltage swing is respectively+5V and-5V), the POINT1-3 end is by tuning capacity Access Control 4 and receive the branch road of four wave band fixed filters groups 2.Under the situation of the analog switch of tuning capacity Access Control 4 a certain road conducting, the loop of forming with tuning sign indicating number TUNE0, inductance L 1_1, current-limiting resistance R1_1, diode PIN1_1, fixed capacity C1_1 and output terminal POINT1 in the section is an example, if the logical signal that receives of TUNE0 for " 1 " (+5V) time, PIN1_1 manages conducting, this moment, capacitor C 1_1 exported to POINT1, parallel connection inserts the branch road of filter network, changes the parameter of former network.The logical signal that receives as TUNE0 for " 0 " (5V) time, the PIN1_1 pipe ends, open circuit, capacitor C 1_1 is inoperative.Four such PIN on-off circuits are formed one group of PIN switched capacitor array, and (C1_3 C1_4), just can realize the function of 16 grades of numerical control transfigurations for C1_1, C1_2 to cooperate different lumped capacitancies.

Claims

1. the digital tuning LC wave filter of a high band, it is characterized in that: comprise the input analog switch, four wave band fixed filters groups, the output analog switch, tuning capacity input control, PIN switched capacitor array group, the band selection input end, tuning sign indicating number input end in the section, signal input part, signal output part; Tuning capacity input control is connected between four wave band fixed filters groups and the PIN switched capacitor array group, and is connected with band selection input end 6; Input analog switch, output analog switch are connected on the input end and the output of four wave band fixed filters groups respectively.

2. the digital tuning LC wave filter of high band according to claim 1 is characterized in that: four wave band fixed filters groups, to form by the filter network of 4 dead center frequencies, and each network all is three rank Chebyshev's type LC coupling resonance networks.

3. the digital tuning LC wave filter of high band according to claim 1, it is characterized in that: PIN switched capacitor array group, constitute by 3 groups of identical PIN switched capacitor arrays of parameter, every group of capacitor array comprises the capacitor of 4 different capabilities sizes, and control corresponding electric capacity inserts or the numerical control PIN switch of disconnection, 4 PIN switches are controlled 4 electric capacity break-makes independently, and PIN switched capacitor array group inserts the resonance branch road of some filter networks in the four above-mentioned wave band fixed filters groups.