CN102638240B - Double-mode type active power filter circuit with adjustable bandwidth - Google Patents
Double-mode type active power filter circuit with adjustable bandwidth Download PDFInfo
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Abstract
The invention provides a double-mode type active power filter circuit with an adjustable bandwidth. The filter circuit can be configured to be at two modes of a complex band-pass filter and a low-pass filter which are respectively used for a receiving chain and an emitting chain in a wireless receiver chip. The filter circuit comprises a first third-order low-pass filter, a second third-order low-pass filter, a multi-resistance network, a first extra input end, a second extra input end, a first first-order passive RC (Remote Control) filter and a second first-order passive RC filter. The filter circuit has the advantages that the double-mode type active power filter circuit can be controlled through an internal switch and can be configured to be at the two work modes, so that the area of the chip is saved and the cost of a system is reduced.
Description
Technical field
The present invention relates to the adjustable double mode active filter circuit of a kind of bandwidth, belong to analog integrated circuit technical field.
Background technology
Adopt technology that CMOS technique realizes short-distance wireless transceiving chip comparative maturity at present, short-distance wireless transceiving chip has been widely used in wireless mouse, wireless remote control, wireless data sending and other Radio Network Systems.On market, there is many moneys product, the competition of radio transmitting and receiving chip.How to reduce chip area, save cost, become the focus of short-distance wireless transceiving chip design.
Short-distance wireless transceiving chip is divided into receiver and transmitting chain, and its working method is semiduplex mode, and this chip can only receive signal at synchronization and maybe can only transmit.This semiduplex mode of operation makes designer when design receiver and transmitting chain, can be by sharing common unit to reach the object that reduces chip cost.
In the design of receiver, system configuration has super-heterodyne architecture, zero-if architecture and low intermediate frequency structure, because low intermediate frequency structure has been taken into account the advantage of super-heterodyne architecture and zero-if architecture, so is widely used.In low intermediate frequency receiver structure, useful signal and image signal pass through respectively quadrature mixing, downconvert to lower intermediate frequency, and useful signal and image signal lay respectively at positive frequency place and negative frequency place.Utilize one to align the different filter of negative frequency components amplitude-frequency response, as complex filter, amplify useful signal filtering mirror image and disturb.Low intermediate frequency receiver suppresses problem by mirror image and transfers to lower intermediate frequency by radio frequency, and integrated level is improved.Signal after down-conversion is not positioned at base band simultaneously, has avoided the problem of DC maladjustment.Low intermediate frequency receiver, has solved the Major Difficulties in superheterodyne receiver and zero intermediate frequency reciver, thereby obtains applying more widely.
In the design of transmitting chain, system configuration is at present most widely used is exactly Direct conversion structure, first digital baseband signal is converted to analog signal by D/A converting circuit (DAC), pass through again the interference signals such as low pass filter filtering clock, then enter into up-conversion mixer, be modulated on output frequency, finally by being launched by power amplifier.
In receiver and transmitting chain, all have separately an intermediate-frequency filter, because operating frequency is low, these two filter circuits can take more chip area.In receiver, need the image signal in complex filter filtering two-way orthogonal signalling, in transmitting chain, need crosstalking of clock signal in a low pass filter filtering DAC outputting analog signal, system is less demanding to the frequency characteristic of this filter.Bandwidth of operation in transmitting chain and system in receiver is the same, and two filters have same band.Above-mentioned two filters can be merged into a filter in conjunction with above-mentioned 2, to reduce chip area, save cost.
In short-distance wireless receive-transmit system, system is higher to the linearity of active filter, and is operated in the active filter in a few MHz frequency ranges, conventionally adopts active RC filter structures to realize, can meet the requirement of the linearity, also can meet the requirement of operating frequency.
Summary of the invention
The object of this invention is to provide the adjustable double mode active filter circuit of a kind of bandwidth, this circuit application is in short-distance wireless receive-transmit system, thereby saving chip area reduces chip cost.
According to technical scheme provided by the invention, the double mode active filter circuit that described bandwidth is adjustable can be configured to complex bandpass filters and two kinds of patterns of low pass filter, be respectively used in the receiver in wireless transceiver chip and transmitting chain in.The double mode active filter circuit that this bandwidth is adjustable comprises: the first third-order low-pass filter, the second third-order low-pass filter, many resistor networks, the first extra input, the second extra input, the first single order passive RC filter, the second single order passive RC filter; Described the first third-order low-pass filter, itself can work alone as the low-pass filter circuit of a real signal, when when forming complex filter circuit a part of, for receiving the in-phase end signal of two-way orthogonal signalling, simultaneously by a signal of its output output, as the in-phase output end signal of complex filter; Described the second third-order low-pass filter, itself can work alone as the low-pass filter circuit of a real signal, when when forming complex filter circuit a part of, for receiving the quadrature end signal of two-way orthogonal signalling, simultaneously by a signal of its output output, as the quadrature output end signal of complex filter; Described many resistor networks are connected between the first third-order low-pass filter and the second third-order low-pass filter, and the first third-order low-pass filter and the second third-order low-pass filter are connected and composed to a complex filter; The described first extra input is connected with many resistor networks with the first third-order low-pass filter; When double mode active filter circuit is configured to low pass filter, the described first extra input is used for receiving input signal, input signal is delivered in the first third-order low-pass filter, simultaneously the isolation between realization and complex filter in-phase input end; The described second extra input is connected with many resistor networks with the second third-order low-pass filter; When double mode active filter circuit is configured to low pass filter, the described second extra input is used for receiving input signal, input signal is delivered in the second third-order low-pass filter, simultaneously the isolation between realization and complex filter orthogonal input; Described the first single order passive RC filter is connected with the output of the first third-order low-pass filter; When double mode active filter circuit is configured to low pass filter, the output of described the first single order passive RC filter for exporting the first third-order low-pass filter, the simultaneously isolation between realization and complex filter in-phase output end; Described the second single order passive RC filter is connected with the output of the second third-order low-pass filter; When double mode active filter circuit is configured to low pass filter, the output of described the second single order passive RC filter for exporting the second third-order low-pass filter, the simultaneously isolation between realization and complex filter quadrature output.
Described the second third-order low-pass filter and the first third-order low-pass filter are identical structures.
When double mode active filter circuit is configured to low pass filter pattern, described the first third-order low-pass filter itself is worked alone as the low-pass filter circuit of a real signal, now the input of the first third-order low-pass filter turn-offs, and input signal is inputted by the first extra input; Described the first third-order low-pass filter is formed by three low-pass first order filter cascades, and the gain of first order low pass filter is A, and the second level and the gain of third level low pass filter are 1; A is the ratio of feedback resistance and input resistance in first order low-pass first order filter, and gain A is for reducing the impact of circuit noise on input signal; Resistance in each low-pass first order filter and electric capacity are adjustable, and the adjusting of resistance is for realizing the selection of different bandwidth pattern, and the adjusting of electric capacity is for the deviation of the filter operating frequency that makes up the factors such as technique and temperature and cause; The input of described the first third-order low-pass filter is connected with switch.
The resistance of described many resistor networks inside is controlled by corresponding switch respectively, all switches are subject to same signal controlling, when switch conduction, double mode active filter circuit is configured to complex filter pattern, when switch turn-offs, double mode active filter circuit is configured to two low pass filter patterns; The switch of controlling each resistance is connected to the output of the first third-order low-pass filter and inner each low-pass first order filter of the second third-order low-pass filter, makes circuit structure symmetrical.
The described first extra input comprises the resistance that two switches are controlled, when switch conduction, and the first extra input work, first input signal passes through resistance again through switch, then enters into the first third-order low-pass filter; When switch turn-offs, the first extra input quits work; When input signal is inputted from the first extra input, the gain of double mode active filter circuit is 1, and the first order firstorder filter of the first third-order low-pass filter inside no longer provides gain A.
The described second extra input comprises the resistance that two switches are controlled, when switch conduction, and the second extra input work, first input signal passes through resistance again through switch, then enters into the second third-order low-pass filter; When switch turn-offs, the second extra input quits work; When input signal is inputted from the second extra input, the gain of double mode active filter circuit is 1, and the first order firstorder filter of the second third-order low-pass filter inside no longer provides gain A.
Described the first single order passive RC filter comprises that the resistance, switch and the electric capacity that connect are successively to ground, the output signal of the one or three rank filter process resistance, then pass through switch, then by electric capacity, after filtering, exported over the ground; When switch conduction, the first single order passive RC filter is as output work, and when switch turn-offs, the first single order passive RC filter quits work.
Described the second single order passive RC filter comprises that the resistance, switch and the electric capacity that connect are successively to ground, the output signal of the two or three rank filter process resistance, then pass through switch, then by electric capacity, after filtering, exported over the ground; When switch conduction, the second single order passive RC filter is as output work, and when switch turn-offs, the second single order passive RC filter quits work.
The switch of the switch of the switch of described the first third-order low-pass filter inside, the second third-order low-pass filter inside and many resistor networks inside, is controlled by first signal S1 jointly; The switch of the first extra input inside, second switch of extra input inside are, the switch of the switch of the first single order passive RC filter inside and the second single order passive RC filter inside is controlled by secondary signal S2 jointly; Conducting when S1 is different with S2; When S1 controls corresponding switch conduction, S2 controls corresponding switch and turn-offs, and double mode active filter circuit is operated in complex filter pattern; When S2 controls corresponding switch conduction, S1 controls corresponding switch and turn-offs, and double mode active filter circuit is operated in low pass filter pattern.
Advantage of the present invention is:
1, the present invention is on the basis of the active RC complex filter based on traditional, has adopted digital switch to control the switching of active filter between complex filter and two kinds of mode of operations of low pass filter, has realized two kinds of mode of operations.
2, in circuit of the present invention, there are two input stages and two output stages, with switch, control respectively, thereby realized the isolation between two kinds of mode of operations, unaffected each other.
3, the extra output stage in circuit of the present invention adopts the passive RC low pass filter of a single order, has both realized isolation, does not consume again large power consumption and area.
4, in circuit of the present invention, adopt digital switch technology to realize complex filter and two kinds of mode of operations of low pass filter, realized sharing of circuit, thereby saved chip area, saved cost.
Accompanying drawing explanation
Fig. 1 is circuit theory diagrams of the present invention.
Fig. 2 is the circuit structure diagram of adjustable resistance icon in Fig. 1.
Fig. 3 is the circuit structure diagram of tunable capacitor icon in Fig. 1.
Fig. 4 is the circuit structure diagram of switch icon in Fig. 1.
Embodiment
Below in conjunction with drawings and Examples, the invention will be further described.
The adjustable double mode active filter circuit of bandwidth that the present invention proposes, as shown in Figure 1.The low-pass first order filter structure of this circuit based on traditional, by three-stage cascade, form third-order low-pass filter circuit, two third-order low-pass filters connect through too much resistor network, just formed a complex filter circuit, be that complex filter is comprised of two low pass filters and many resistor networks, when controlling conducting and the shutoff of many resistor networks, just realized the switching between complex filter and low-pass filter circuit.
In short-distance wireless transceiving chip, complex filter is used in receiver, realizes the inhibition to image signal, and low pass filter is used in transmitting chain, realizes the inhibition to clock interference signal.In transmitting chain, only need a low-pass filter circuit, have two low-pass filter circuits in this active filter circuit, when emission state, another low pass filter is not worked, to save power consumption.
The double mode active filter circuit concrete structure that described bandwidth is adjustable comprises: the first third-order low-pass filter 26, the second third-order low-pass filter 27, the extra input 22 of the extra input 21, second of many resistor networks 23, first, the first single order passive RC filter 24, the second single order passive RC filter 25; Described the first third-order low-pass filter 26, itself can work alone as the low-pass filter circuit of a real signal, when when forming complex filter circuit a part of, for receiving the in-phase end signal of two-way orthogonal signalling, simultaneously by a signal of its output output, as the in-phase output end signal of complex filter; Described the second third-order low-pass filter 27, itself can work alone as the low-pass filter circuit of a real signal, when when forming complex filter circuit a part of, for receiving the quadrature end signal of two-way orthogonal signalling, simultaneously by a signal of its output output, as the quadrature output end signal of complex filter; Described many resistor networks 23 are connected between the first third-order low-pass filter 26 and the second third-order low-pass filter 27, and the first third-order low-pass filter 26 and the second third-order low-pass filter 27 are connected and composed to a complex filter; The described first extra input 21 is connected with many resistor networks 23 with the first third-order low-pass filter 26; When double mode active filter circuit is configured to low pass filter, the described first extra input 21, for receiving input signal, is delivered to input signal in the first third-order low-pass filter 26, simultaneously the isolation between realization and complex filter in-phase input end; The described second extra input 22 is connected with many resistor networks 23 with the second third-order low-pass filter 27; When double mode active filter circuit is configured to low pass filter, the described second extra input 22, for receiving input signal, is delivered to input signal in the second third-order low-pass filter 27, simultaneously the isolation between realization and complex filter orthogonal input; Described the first single order passive RC filter 24 is connected with the output of the first third-order low-pass filter 26; When double mode active filter circuit is configured to low pass filter, described the first single order passive RC filter 24 is for exporting the output of the first third-order low-pass filter 26, realize simultaneously and complex filter in-phase output end between isolation; Described the second single order passive RC filter 25 is connected with the output of the second third-order low-pass filter 27; When double mode active filter circuit is configured to low pass filter, described the second single order passive RC filter 25, for exporting the output of the second third-order low-pass filter 27, is realized and the defeated isolation of just surrendering between end of complex filter simultaneously.
When double mode active filter circuit is configured to low pass filter pattern, described the first third-order low-pass filter 26 itself is worked alone as the low-pass filter circuit of a real signal, now the input of the first third-order low-pass filter 26 turn-offs, and input signal is inputted by the first extra input 21.Described the first third-order low-pass filter 26 is formed by three low-pass first order filter cascades, and the gain of first order low pass filter is A, and the second level and the gain of third level low pass filter are 1; By adjusting the ratio of feedback resistance and input resistance in first low-pass first order filter, be A, the gain that can realize first order low pass filter is A, and A is greater than 1 conventionally, and this gain is for reducing the impact of circuit noise on input signal; Resistance in each low-pass first order filter and electric capacity are adjustable, and the adjusting of resistance is for realizing the selection of different bandwidth pattern, and the adjusting of electric capacity is for the deviation of the filter operating frequency that makes up the factors such as technique and temperature and cause; The input of described the first third-order low-pass filter 26 is connected with switch.The second third-order low-pass filter 27 and the first third-order low-pass filter 26 are identical structures.
The resistance of described many resistor networks 23 inside is controlled by corresponding switch respectively, all switches are subject to same signal controlling, when switch conduction, double mode active filter circuit is configured to complex filter pattern, when switch turn-offs, double mode active filter circuit is configured to two low pass filter patterns; The switch of controlling each resistance is connected to the output of the first third-order low-pass filter 26 and second third-order low-pass filter 27 inner each low-pass first order filter, makes circuit structure symmetrical.
The described first extra input 21 comprises the resistance that two switches are controlled, when switch conduction, and the first extra input 21 work, first input signal passes through resistance again through switch, then enters into the first third-order low-pass filter 26; When switch turn-offs, the first extra input 21 quits work; When input signal is inputted from the first extra input 21, the gain of double mode active filter circuit is 1, and the first order firstorder filter of the first third-order low-pass filter 26 inside no longer provides gain A.
The described second extra input 22 comprises the resistance that two switches are controlled, when switch conduction, and the second extra input 22 work, first input signal passes through resistance again through switch, then enters into the second third-order low-pass filter 27; When switch turn-offs, the second extra input 22 quits work; When input signal is inputted from the second extra input 22, the gain of double mode active filter circuit is 1, and the first order firstorder filter of the second third-order low-pass filter 27 inside no longer provides gain A.
Described the first single order passive RC filter 24 comprises that the resistance, switch and the electric capacity that connect are successively to ground, the output signal of the one or three rank filter 26 process resistance, then pass through switch, then by electric capacity, after filtering, exported over the ground; When switch conduction, the first single order passive RC filter 24 is as output work, and when switch turn-offs, the first single order passive RC filter 24 quits work.
Described the second single order passive RC filter 25 comprises that the resistance, switch and the electric capacity that connect are successively to ground, the output signal of the two or three rank filter 27 process resistance, then pass through switch, then by electric capacity, after filtering, exported over the ground; When switch conduction, the second single order passive RC filter 25 is as output work, and when switch turn-offs, the second single order passive RC filter 25 quits work.
The switch of the switch of the switch of described the first third-order low-pass filter 26 inside, the second third-order low-pass filter 27 inside and many resistor networks 23 inside, is controlled by first signal S1 jointly; The switch of the first extra input 21 inside, second switch of extra input 22 inside are, the switch of the switch of the first single order passive RC filter 24 inside and the second single order passive RC filter 25 inside is controlled by secondary signal S2 jointly; Conducting when S1 is different with S2; When S1 controls corresponding switch conduction, S2 controls corresponding switch and turn-offs, and double mode active filter circuit is operated in complex filter pattern; When S2 controls corresponding switch conduction, S1 controls corresponding switch and turn-offs, and double mode active filter circuit is operated in low pass filter pattern.
In Fig. 1, input VIIP, VIIN and VQIP, VQIN is respectively two groups of inputs of complex filter, receives the two-way positive blending output signal of front stage circuits output.VIIP wherein, VIIN receives in-phase input end signal, VQIP, VQIN receives orthogonal input signal.Output VION, VIOP and VQON, VQOP is respectively two groups of outputs of complex filter, is respectively in-phase output end and quadrature output.When filter of the present invention is operated in complex filter pattern, signal is exactly to enter from above-mentioned input, output output.
In Fig. 1, input port VTIP, the input that VTIN is low pass filter, the input of signal when correspondence system is operated in emission state, output port VTOP, the output that VTON is low pass filter.Transmitting chain only needs a low-pass filter circuit, and now signal is through above-mentioned input port VTIP, and VTIN enters into third-order low-pass filter circuit 26, and from output port VTOP, VTON output.
The input port VTIP of the first third-order low-pass filter 26, the input port VIIP of VTIN and complex filter, VIIN contains pair of switches separately, in order to realize two isolation between port.The output port VTOP of low pass filter, the output port VION of VTON and complex filter, VIOP isolates by a first single order passive RC filter 24 with switch.When being operated in low pass filter pattern, the switch conduction of the first single order passive RC filter 24 inside, when being operated in complex filter pattern, the switch of the first single order passive RC filter 24 inside turn-offs.
Under the mode of operation of low pass filter, because transmitting chain only needs a third-order low-pass filter circuit, therefore, the second third-order low-pass filter 27 is in idle state, but be the symmetry of holding circuit structure, guarantee the performance of complex filter, the second third-order low-pass filter 27 is also with the first third-order low-pass filter 26, one second extra input 22 and output, i.e. the second single order passive RC filter 25 have been added respectively.Owing to there is no the input of signal, so the input of this second third-order low-pass filter 27 and output termination reference potential VCM.Conventionally VCM is exactly earth potential.
In Fig. 1, the structure of all adjustable resistances all as shown in Figure 2, connect successively by the first resistance R 1, the second resistance R 2, the 3rd resistance R 3, a switch in parallel in the 3rd resistance R 3, a switch in parallel again on the tandem compound of the second resistance R 2 and the 3rd resistance R 3.In the design, resistance has three kinds of optional values, corresponding three kinds of bandwidth selection patterns.When changing resistance R BW1, RBW2, during RBW3, bandwidth is adjusted accordingly, and the centre frequency of complex filter can be affected when bandwidth changes, thus the resistance R FC1 in many resistor networks, RFC2, RFC3 also will adjust accordingly, so that the centre frequency of complex filter is constant.
In Fig. 1, the structure of all tunable capacitors all as shown in Figure 3, realize by a capacitor array by the tunable capacitor shown in Fig. 3, and it is comprised of 6 sub-electric capacity in parallel, and every sub-electric capacity is all controlled by switch separately.The value of 6 sub-electric capacity is respectively △ C, 2 △ C, 4 △ C, 8 △ C, 16 △ C and C.Wherein C is the fixing electric capacity of conducting, and it is controlled by switch Tclosed, the state of this switch in normal conducting.Capacitance is that the electric capacity of △ C is controlled by switch T0, capacitance is that the electric capacity of 2 △ C is controlled by switch T1, capacitance is that the electric capacity of 4 △ C is controlled by switch T2, capacitance is that the electric capacity of 8 △ C is controlled by switch T3, capacitance is that the electric capacity of 16 △ C is controlled by switch T4, its control signal is from automatic frequency tuning circuit on sheet (this electricity route system provides), and the object of control capacittance is the deviation that compensate for process and temperature etc. are introduced filter operating frequency.
In many resistor networks 23, each resistance has switch to control its conducting and shutoff, one end of one end contact resistance of each switch, the other end is connected to the output of the first third-order low-pass filter 26 and second third-order low-pass filter 27 inner each low-pass first order filter, makes circuit structure symmetrical.The structure of many resistor networks 23 is symmetrical, and the ghost effect of its introducing is also symmetrical to two filter circuits, makes the best performance of filter.
Control complex filter input VIIP, VIIN and VQIP, the switch of the switch of VQIN and many resistor networks 23 inside is with the control that is subject to first signal S1, and the switch of two extra input 21,22 inside and the switch of two single order passive RC filter 24,25 inside are with controlled by secondary signal S2.When S1 controls corresponding switch conduction, S2 controls corresponding switch and turn-offs, and now filter is operated under the pattern of complex filter; When S2 controls corresponding switch conduction, S1 controls corresponding switch and turn-offs, and now filter is operated under the pattern of low pass filter.
Switches all in Fig. 1 all adopt the structure shown in Fig. 4, i.e. the structure of transmission gate.In CMOS technique, transmission gate consists of a NMOS pipe and a PMOS pipe.The drain terminal of NMOS pipe connects the source of PMOS pipe, as the input of transmission gate; The source of NMOS pipe connects the drain terminal of PMOS pipe, as the output of transmission gate; The grid end connection control signal S of NMOS pipe, simultaneously, control signal S is also connected to an inverter, the output signal of inverter is connected to the grid end of PMOS pipe, when control signal S is high level, and transmission gate conducting, input signal can pass through, when control signal S is low level, transmission gate turn-offs, and input signal can not pass through.
Claims (9)
1. the adjustable double mode active filter circuit of bandwidth, is characterized in that: comprise the first third-order low-pass filter (26), the second third-order low-pass filter (27), many resistor networks (23), the first extra input (21), the second extra input (22), the first single order passive RC filter (24), the second single order passive RC filter (25);
Described the first third-order low-pass filter (26), itself can work alone as the low-pass filter circuit of a real signal, when when forming complex filter circuit a part of, for receiving the in-phase end signal of two-way orthogonal signalling, export a signal, as the in-phase output end signal of complex filter simultaneously;
Described the second third-order low-pass filter (27), itself can work alone as the low-pass filter circuit of a real signal, when when forming complex filter circuit a part of, for receiving the quadrature end signal of two-way orthogonal signalling, export a signal, as the quadrature output end signal of complex filter simultaneously;
Described many resistor networks (23) are connected between the first third-order low-pass filter (26) and the second third-order low-pass filter (27), and the first third-order low-pass filter (26) and the second third-order low-pass filter (27) are connected and composed to a complex filter;
The described first extra input (21) is connected with many resistor networks (23) with the first third-order low-pass filter (26); When double mode active filter circuit is configured to low pass filter, the described first extra input (21) is for receiving input signal, input signal is delivered in the first third-order low-pass filter (26), simultaneously the isolation between realization and complex filter in-phase input end;
The described second extra input (22) is connected with many resistor networks (23) with the second third-order low-pass filter (27); When double mode active filter circuit is configured to low pass filter, the described second extra input (22) is for receiving input signal, input signal is delivered in the second third-order low-pass filter (27), simultaneously the isolation between realization and complex filter orthogonal input;
Described the first single order passive RC filter (24) is connected with the output of the first third-order low-pass filter (26); When double mode active filter circuit is configured to low pass filter, described the first single order passive RC filter (24) is for exporting the output of the first third-order low-pass filter (26), realize simultaneously and complex filter in-phase output end between isolation;
Described the second single order passive RC filter (25) is connected with the output of the second third-order low-pass filter (27); When double mode active filter circuit is configured to low pass filter, described the second single order passive RC filter (25) is for exporting the output of the second third-order low-pass filter (27), realize simultaneously and complex filter quadrature output between isolation.
2. the adjustable double mode active filter circuit of bandwidth as claimed in claim 1, is characterized in that, described the second third-order low-pass filter (27) is identical structure with the first third-order low-pass filter (26).
3. the adjustable double mode active filter circuit of bandwidth as claimed in claim 2, it is characterized in that, when double mode active filter circuit is configured to low pass filter pattern, described the first third-order low-pass filter (26) itself is worked alone as the low-pass filter circuit of a real signal, now the input of the first third-order low-pass filter (26) turn-offs, and input signal is inputted by the first extra input (21);
Described the first third-order low-pass filter (26) is formed by three low-pass first order filter cascades, and the gain of first order low pass filter is A, and the second level and the gain of third level low pass filter are 1; A is the ratio of feedback resistance and input resistance in first order low-pass first order filter, and gain A is for reducing the impact of circuit noise on input signal; Resistance in each low-pass first order filter and electric capacity are adjustable, and the adjusting of resistance is for realizing the selection of different bandwidth pattern, and the adjusting of electric capacity is for the deviation of the filter operating frequency that makes up the factors such as technique and temperature and cause; The input of described the first third-order low-pass filter (26) is connected with switch;
By adjusting the ratio A of feedback resistance and input resistance in first low-pass first order filter, can realize the gain A of first order low pass filter, A is greater than 1 conventionally.
4. the adjustable double mode active filter circuit of bandwidth as claimed in claim 3, it is characterized in that, the inner resistance of described many resistor networks (23) is controlled by corresponding switch respectively, all switches are subject to same signal controlling, when switch conduction, double mode active filter circuit is configured to complex filter pattern, and when switch turn-offs, double mode active filter circuit is configured to two low pass filter patterns; The switch of controlling each resistance is connected to the output of the first third-order low-pass filter (26) and inner each low-pass first order filter of the second third-order low-pass filter (27), makes circuit structure symmetrical.
5. the adjustable double mode active filter circuit of bandwidth as claimed in claim 3, it is characterized in that, the described first extra input (21) comprises the resistance that two switches are controlled, when switch conduction, the first extra input (21) work, first input signal passes through resistance again through switch, then enters into the first third-order low-pass filter (26); When switch turn-offs, the first extra input (21) quits work; When input signal is inputted from the first extra input (21), the gain of double mode active filter circuit is 1, and the inner first order firstorder filter of the first third-order low-pass filter (26) no longer provides gain A.
6. the adjustable double mode active filter circuit of bandwidth as claimed in claim 3, it is characterized in that, the described second extra input (22) comprises the resistance that two switches are controlled, when switch conduction, the second extra input (22) work, first input signal passes through resistance again through switch, then enters into the second third-order low-pass filter (27); When switch turn-offs, the second extra input (22) quits work; When input signal is inputted from the second extra input (22), the gain of double mode active filter circuit is 1, and the inner first order firstorder filter of the second third-order low-pass filter (27) no longer provides gain A.
7. the adjustable double mode active filter circuit of bandwidth as claimed in claim 1, it is characterized in that, described the first single order passive RC filter (24) comprises that the resistance, switch and the electric capacity that connect are successively to ground, the output signal of the one or three rank filter (26) is through resistance, pass through again switch, then by electric capacity, after filtering, exported over the ground; When switch conduction, the first single order passive RC filter (24) is as output work, and when switch turn-offs, the first single order passive RC filter (24) quits work.
8. the adjustable double mode active filter circuit of bandwidth as claimed in claim 1, it is characterized in that, described the second single order passive RC filter (25) comprises that the resistance, switch and the electric capacity that connect are successively to ground, the output signal of the two or three rank filter (27) is through resistance, pass through again switch, then by electric capacity, after filtering, exported over the ground; When switch conduction, the second single order passive RC filter (25) is as output work, and when switch turn-offs, the second single order passive RC filter (25) quits work.
9. the adjustable double mode active filter circuit of bandwidth as claimed in claim 1, it is characterized in that, inner switch and the inner switch of many resistor networks (23) of switch, the second third-order low-pass filter (27) that described the first third-order low-pass filter (26) is inner, is controlled by first signal S1 jointly; Inner inner switch and the inner switch of the second single order passive RC filter (25) of switch, the first single order passive RC filter (24) of switch, the second extra input (22) that the first extra input (21) is inner, is controlled by secondary signal S2 jointly; Conducting when S1 is different with S2; When S1 controls corresponding switch conduction, S2 controls corresponding switch and turn-offs, and double mode active filter circuit is operated in complex filter pattern; When S2 controls corresponding switch conduction, S1 controls corresponding switch and turn-offs, and double mode active filter circuit is operated in low pass filter pattern.
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| CN103151996B (en) * | 2013-03-01 | 2016-03-16 | 东南大学 | A kind of reconfigurable filter |
| CN103326693B (en) * | 2013-05-09 | 2016-05-18 | 重庆西南集成电路设计有限责任公司 | Reconfigurable Gm_C filter circuit |
| CN103227620B (en) * | 2013-05-09 | 2016-06-22 | 重庆西南集成电路设计有限责任公司 | reconfigurable Gm-C filter circuit |
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| CN103715876B (en) * | 2013-12-23 | 2018-03-13 | 延锋伟世通电子科技（上海）有限公司 | Low-voltage drop active power filter |
| CN103956989B (en) * | 2014-05-23 | 2018-01-26 | 武汉大学 | A Multimode Multifrequency Reconfigurable Gm‑C Complex Filter |
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