Characteristic variable switched capacitor filter

[Detailed Description of the Invention]

(a) The technical field of an invention Even if the present invention relates to the programmable switched capacitor filter which can carry out a change setup of the filter property arbitrarily and increases the edible kind of filter property especially, it relates to the characteristic variable switched capacitor filter which could be made to lessen the number of the capacity to be used. Can conventional technology and a problem The switched capacitor filter (it calls for short following SCF) which combined the switch, the capacitor, and the operation widening machine, Since Si in whom formation of p monolithic integrated circuit is possible, and filter property excel [ development / of MO8LSI art etc. ] in Decided Si and temperature characteristics by the not the capacity itself but capacity ratio of the capacitor, development is advanced to various kinds of uses. Hereinafter, the conventional characteristic variable switched capacitor fist filter is explained using figures. The block diagram of the circuit of the characteristic variable switched capacitor fist filter of a conventional example is shown in Drawing 1. This example makes the Yoshifiruta characteristic with variable prepare and make change connection only of the kind of variable characteristic of wishing to have the capacitor which determines the characteristic. In Drawing 1, LGI and LG2 are a logic circuit and Ca. It is Construction capacitor and 5W16 to CbUK, C, and K2O'. 5W17 is a switch which determines the number of multiple connection of a capacitor. namely, logic circuit LGI -- be alike LG2 -- Yo Si is made to decide Sisui f 5W16 and the number of 5W 17' (r fti control main-actor-in-a-No-play Capacity ca, cb) multiple connection, and the excursion of the value of 4C is carried out to KIC9. in such composition, although the filter property of the kind of only capacitor Ca and CbO number can be acquired, when it is requested that many kinds are acquired east, Si with many capacitors and necessary area are thick -- To -- it is of and being integrated on 1 A tip becomes difficult. Then, they are capacitors Ca and Cb, respectively Reference volume-Jil(7) 2 .2 .2 ... Two It is considered as n capacitors and the combination of the multiple connection of those capacitors is chosen, It is proposed that the filter property of a 2-n kind is acquired with n capacitors. However, when eight capacitors are prepared, for example and the filter property of 2 = 256 buildings is acquired, the capacitor of the minimum capacity must be made into the capacity of 1/256 of standard capacity C. That is, when standard capacity C is 32 pF, minimum capacity C-Listen is very difficult to manufacture the capacitor of 0.125 pF, Si, and such minute capacity with sufficient accuracy on a chip in practice. (c) The object of an invention Even if it increases Cone and the good varieties of filter property, the above-mentioned fault has little number of a capacitor, it lives in it, and the object of the present invention has integrated circuit-ization in offer of an easy characteristic variable switched capacitor filter. 3- (d) Constitution of an invention Each terminal for every signal which delayed the signal which delayed the input signal and it which carried out the sample hold of the input voltage the time of the integral multiple of a sampling period in order that the present invention might achieve the above-mentioned object, and output voltage the time of the integral multiple of a sampling period, Between the negative input terminals of an operation widening machine, the input capacitance of the same capacity that has a switch is connected to Both ends, respectively, Between the negative input terminal of the operation widening machine, and an output terminal, capacity CB' with the accumulation capacity CB which has a switch, and capacity equal to Accumulation capacity icB and both ends, and the switch for electric charge electric discharge are connected, It has output of the operation widening machine, and composition which provided the sample hold circuit between output terminals, The switch of each input capacitance is controlled according to the coefficient of a binary number, and transmission to this Accumulation capacity-JiCB of the electric charge of each input signal of Terminals. Si of the above-mentioned Each is performed alternatively, and the electric charge transmitted to the accumulation capacity CB -- every time of 1/N of a sampling period -- Ha [-- operating the switch of the both ends of number Capacity of times 1tCB' of a law, and dwindling it after an appropriate time -- the electric charge of output signal 4-capacity CB of the operation widening machine -- the -- carrying out switch To Si electric discharge for electric charge electric discharge -- operation of the above [ Paternal ] -- Repeat -- the characteristic variable switched capacitor filter characterized by things. (e) The example of an invention The block diagram showing the composition of switched capacitor Accumulator by which 0 figure 2 explained according to a figure per example of the present invention below is used for the present invention, and Drawing 3 are the time charts which show ON of each switch of Drawing 2, and the state of OFF, As for Os, switch SWI and 5W21 A C are SuiyfsW3 and 11u Sui y Chi SW6.SW7.gas. When A littleIs and lc are '''W levels in the control signal of switch SW4.SW5 J11a2, respectively, Switch SWI and SW2.SW3 are closed and Oal, gB2 *01 mosquito j'''L" Lehelnotki, and Sui y f S W 4 and SW5 *SW6.SW7 are closed to the ground side. Inside 1 and 4 of a figure, CBfrom dignity coefficient' of a sample hold circuit (S-H is called below) and 2 is capacity OP-AMP and 3, and capacity CB and the value of CB' are equal. If a sample hold is carried out in S@H1 and switch SW4.SW5 closes to S-H1 and OP -AMP2 side when switch SW1 turns on input voltage in Drawing 2 by sampling period T shown in 3rd [ The ] figure 08, the electric charge will be sent and accumulated in capacity CA all Throughout and capacity CB. as for the electric charge accumulated in capacity CB, switch SW6.SW7 is connected to the input/output terminal of OP-AMP2 at the time of H" level of Drawing 3 O1 -- capacity CB' -- be alike -- Si -- it is carried out for 2 minutes each time. the pulse after sampling period T which this capacity CB' shows the operation connected to the input/output terminal of OP-AMP2 to 8 circuit Si return and the 8th time between sampling period T, and shows the output voltage of OP-AMP2 in Drawing 3 O8 -- switch SW2' -- it e closes and carries out a sample hold in 5LIH4. If these eight operations finish, as shown in 3rd [ The ] figure yIc, it will switch SW3'i Close, and the electric charge which was accumulated as for eight capacity CBIC will be cleared, and the same operation will be repeated from the start. On the '''H'' level which switch SW6.SW7 shows in Drawing 3 O1, after capacity CB' is connected in parallel with Capacity:tCB ('L" level of 3rd [ The ] figure 01), it is connected to the ground side and the electric charge of capacity CB' is discharged. The first B shown in capacity CB lal and yIa2 of Drawing 3. The electric charge sent through Capacity fCA to of timing is set to 2 of a binary number after eight above-mentioned operations, the electric charge which Capacity-iCA'e-let it pass and has been sent in the timing of B, is set to 2, and the electric charge sent in the timing of B8 is set to 2. Timing which "H" level, Si, and switch SW4.SW5 close in Drawing 3 phia1 and phia2, If you would like to make it dignity coefficient generator 3 To Si, for example, 2-8, as a binary number shows how much the electric charge accumulated in capacity CB to gradual decrease Refers, To Si and 3rd [ The ] figure phiax, and phia2, it will control to make the time of B, into 'H" level. If a formula shows the relation of the method voltage of a crowd by the above operation, it will become as following. Vout CA ■ n= -- One (bl@2 +b2m2 +b3@2 10b4@2 +bs-2+b6112 +b7@2 +b8and2) ......... (1) 7 - However, bl-bl is 3rd [ The ] figure phiill as Ashitai ming at a dignity coefficient. It corresponds to the ''H'' level of B [ of phia2 ], and ~B8, and a ''L'' level, and is a value of 1 or 0. This matter is 2.2.2 of standard capacity. ...... Capacity of eight pieces of two is realized in equivalent by two of Capacity iCB and CB', and it is supposed [ make / into a dignity coefficient b1~b8't"1"level or IIO" level / selection of the combination of the multiple connection of those capacity ] that it is possible in Measurement. Namely, what is necessary is to make only dignity coefficients bl and bl into 1" level, for making it equivalent if two pieces, 2 and 2 of standard capacity, are arranged in parallel. Drawing 4 is a block diagram of one example of the gone-round type filter applied to the present invention. In inside 5~8 of a figure, the delay circuit of 1 sampling period is shown, 9~13 shows a dignity coefficient multiplier, and 14.15 shows an adding machine. Delay circuit 7 by the side of the gone-round type filter of Drawing 4, or output voltage? 8 and the non-going round type filter which N sees and does not have coefficient multipliers 12 and 13 and adding machine 15 are publicly known things mainly used for the filter of a digital signal. The transfer constant of this filter is as following. 8- X [ however, ] -- input voltage and Y -- output voltage and Z-'= e" -- "omega= angle frequency, T-sampling period, and a""" -- boil e each multiplier 9~13 -- it is a dignity coefficient by which the Si multiplication is carried out. Power consumption can also be made to carry out the few fence of the present invention greatly [ filter / this gone-round type or / non-going round type / a circuit scale ] using switched capacitor Accumulator. Drawing 5 is a block diagram showing the composition of the characteristic variable switched e capacitor filter of the example of the present invention. The same sign shows the thing of the same function as In Fig. 2 figure. 5'~7'J -- the delay circuit of 1 sampling period, and 16 -- a dignity coefficient generator and 5W4- 1 and 5W4-6.SW5' is a switch, and 5W4-1~5W4-6 carries out the same operation to the same timing as switch SW4 of Drawing 2, and each switch is seen one and controlled by coefficient generator 16. a switch -- SW -- five -- ' -- a ground -- a side -- connecting -- having had -- a case -- the -- three -- a figure -- phi -- l -- being shown -- ' -- ' -- H -- ' -- ' -- a level -- timing -- ON -- becoming -- OP-AMP -- two -- a side -- pressure -- connecting -- having had -- a case -- the -- three -- a figure -- phi -- one -- being shown -- ' -- L -- " -- a level -- timing -- ON -- becoming . CA-1~CA-5 is equivalent to capacity CA of Drawing 2 by the capacity of the same value. The circuit of Drawing 5 is what applied the circuit of Accumulator of Drawing 2 to the circuit of the gone-round type filter of Drawing 4, and Ah Si and each switch carry out the same operation as the case of Accumulator of Drawing 2. S -Hl It is [ the voltage by which the sample hold was carried out, and ] this voltage, Delay circuit 5' The output voltage delayed one sampling period in the signal respectively delayed by 6' one sampling period, and the operation, and the signal further delayed by delay circuit 7' one sampling period, Dignity coefficient b1~b8 of (1) type of the method [ of one ] above-mentioned explanation equivalent to dignity coefficient a~e of (2) types explained before dignity coefficient generator 16 is set to 1 and 0, The electric charge which passes 0 which controls the electric charge which passes along Capacity ftcA-1~CA-5, and this capacity CA-1~CA-5 is simultaneously transmitted and added to Capacity icB. Therefore, the circuit of Drawing 5 becomes equivalent to the circuit of Drawing 4. Therefore, a characteristic variable switched fist capacitor filter is realizable. boil the dignity coefficient equivalent to this dignity coefficient a~e dignity coefficient generator 16 -- Outside Si -- it can give arbitrarily. If a delay circuit 7'-related circuit is removed, it will become a non-going round type filter. since the value which there is little number of a capacitor, it ends and 8' boils again should just also observe the value of &JiCA and capacity CB when carrying out characteristic variable, the circuit of Drawing 5 can be made into what has easy integrated-circuit-izing. (f) EFFECT OF THE INVENTION the above -- details -- explanation To -- it needs -- since few Sakura of the number of the capacity to be used and the ratio of the capacity used few at best again is also good according to the present invention, integration becomes easy It is made to the value from which Storey capacity, such as a Value switch of capacity, does not serve as an error, and is effective in the characteristic variable switched capacity filter which was excellent in the characteristic being realizable.

[Brief Description of the Drawings]

Drawing 1 is a block diagram showing the composition of the characteristic variable switched capacitor filter of a conventional example, Drawing 2 is a block diagram showing the composition of the switched capacitor and Accumulator used for the present invention, The time chart of ON/OFF of each switch of Drawing 2 and 4th [ The ] figure 11- of Drawing 3 are a block diagram of a gone-round type filter, and a block diagram in which Drawing 5 shows the composition of the characteristic variable switched phi capacitor filter of the example of the present invention. inside 1 and 4 of a figure -- a sample hold circuit and 3.16 -- a dignity coefficient generating circuit and 2. -- OPI, a 0P2Fi operation widening machine, 5~8, and 5'~7' -- a delay circuit and 9~13 -- a dignity coefficient multiplier, 14.15H adding machine, K, and 0% -- C. C, Ca, Cb, CA, CB, CB', and CA-1~CA-5 is capacity. As for a switch, LGI, and LG2, SWI~SW7.SW5' and 5W4-1~5W4-5 and 5W11~5W16 shows a logic circuit. 12-