CN100578913C - Variable capacitor used in pressure control oscillator - Google Patents
Variable capacitor used in pressure control oscillator Download PDFInfo
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- CN100578913C CN100578913C CN200610170245A CN200610170245A CN100578913C CN 100578913 C CN100578913 C CN 100578913C CN 200610170245 A CN200610170245 A CN 200610170245A CN 200610170245 A CN200610170245 A CN 200610170245A CN 100578913 C CN100578913 C CN 100578913C
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Abstract
The invention discloses a circuit which ensures that a voltage-controlled oscillator has the fixed frequency adjustment constant by a parallel capacitor group and a variable capacitor group. The capacitor group consists of a plurality of parallel switch capacitor branches, the switch capacitor branches are serially connected in the order of capacitor-switch-capacitor. When the switch among the capacitors is closed, the switch capacitor branches are changed into capacitor-capacitor in series for further functioning in the capacitor group. Contrariwise, when the switch is powered on, an open circuit is formed, and the switch capacitor branches fail. Using an external control circuit to control the switch among the capacitors can control the capacitance of the capacitor group. Besides that the capacitors in the capacitor group can be replaced by variable capacitors, the variable capacitor group can control the switch among the variable capacitors by an external control circuit, and then can control the range of the variable capacitance in the variable capacitor group, thus, when the capacitor group and the variable capacitor group are connected in parallel, the needed fixed frequency adjustment constant characteristic can be obtained with the control from the control circuit.
Description
Technical field
The invention relates to a kind of variable capacitor, and be particularly related to a kind of variable capacitor that is used in the voltage controlled oscillator.
Background technology
In general, voltage controlled oscillator (Voltage Controlled Oscillator, VCO) be contained in phase-locked loop (Phase Locked Loop, PLL) in and be applied in digital circuit or analog circuit.Especially be applied to the communications field that to adjust frequency on a large scale.
Please refer to Fig. 1, its illustrate is known voltage controlled oscillator schematic diagram.This voltage controlled oscillator is exposed in U.S.'s bulletin patent No. 7038552, as shown in the figure, first inductor (Inductor) 2 is connected between the drain electrode (Drain) of a voltage source (Vcc) and first field-effect transistor (Field Effect Transistor) 6, and the source electrode of first field-effect transistor 6 (Source) is connected to a current source (Current Source) 10.In like manner, second inductor 22 is connected between the drain electrode of this voltage source (Vcc) and second field-effect transistor 26, and the source electrode of second field-effect transistor 26 is connected to this current source 10.Moreover the grid (Gate) of the drain electrode of first field-effect transistor 6 and second field-effect transistor 26 interconnects, and the grid (Gate) of the drain electrode of second field-effect transistor 26 and first field-effect transistor 6 also interconnects.At last, (node a) and a variable capacitor (Variable Capacitance) is provided between the drain electrode of second field-effect transistor (node b) in the drain electrode of first field-effect transistor.Therefore, can be considered promptly that an inductor in parallel (first inductor adds second inductor) forms a LC oscillating circuit (LC Oscillating Circuit) with this variable capacitor between node a and the node b.Moreover, this variable capacitor is made up of 42 of a switching capacity group (Switch Capacitance Bank) 40 and one capacity-changing units (Varactor Unit), wherein, switching capacity group 40 is to be used for the output frequency of coarse adjustment voltage controlled oscillator, and capacity-changing unit 42 is the output frequencies that are used for finely tuning voltage controlled oscillator.
As shown in the figure, comprise a plurality of capacitive branch in the switching capacity group 40, each capacitive branch comprises one first capacitor 50, a switching transistor 54 and one second capacitor 52 and is serially connected with between node a and the node b.Via the control of the switch control end (Gate) of switching transistor 54, each capacitive branch all can optionally be reached being connected or not connecting between node a and the node b.When capacitive branch was connected between node a and the node b, the equivalent capacitance value of variable capacitor will increase; In like manner, when capacitive branch was not attached between node a and the node b, the equivalent capacitance value of variable capacitor will reduce.Therefore, utilize said method to get final product the output frequency of coarse adjustment voltage controlled oscillator.
Moreover, as shown in the figure, capacity-changing unit 42 comprises drain electrode and interconnective two field-effect transistors 60,62 of source electrode, and the grid of field-effect transistor 60,62 is connected to node a and node b respectively, and the drain electrode of field-effect transistor 60,62 then is connected to a voltage controling end 64.When the input voltage of voltage controling end 64 changed, the change of voltage difference can cause the capacitance of field-effect transistor 60,62 to change between field-effect transistor 60,62 drain electrodes and the grid.Therefore, utilize the input voltage of voltage controling end 64 to change, can reach the output frequency of fine setting voltage controlled oscillator.Moreover except field-effect transistor 60,62 can change in response to the change of input voltage the capacitance, capacity-changing unit 42 also can be made up of variable capacitance diode (Varicap Diode).
Please refer to Fig. 2, its illustrate is the output frequency schematic diagram of known voltage controlled oscillator.By among the figure as can be known, the adjustable output frequency interval of voltage controlled oscillator is between f0～f7; Wherein, (f5～f7) provides a variable capacitance scope (Δ c) to finish by one first capacitance (c1) and the capacity-changing unit 42 that first capacitive branch of switching capacity group 40 provides to first frequency band (Band) I; (f3～f6) adds that by this first capacitance that first capacitive branch and second capacitive branch of switching capacity group 40 provides one second capacitance (c1+c2) and capacity-changing unit 42 provide this variable capacitance scope (Δ c) to finish to the second frequency band II; (f1～f4) adds that by this first capacitance that first capacitive branch, second capacitive branch and the 3rd capacitive branch of switching capacity group 40 provides this second capacitance adds that one the 3rd capacitance (c1+c2+c3) and capacity-changing unit 42 provide this variable capacitance scope (Δ c) to finish to the 3rd frequency band III; Wherein, (f0～f2) adds that by first capacitance that first capacitive branch, second capacitive branch, the 3rd capacitive branch, the 4th capacitive branch of switching capacity group 40 provides this second capacitance adds that the 3rd capacitance adds that one the 4th capacitance (c1+c2+c3+c4) and capacity-changing unit 42 provide this variable capacitance scope (Δ c) to finish to the 4th frequency band IV.Because the output frequency of voltage controlled oscillator is to be proportional to
And capacity-changing unit 42 variable capacitance scopes (Δ c) are fixed, and therefore, when the capacitance that provides when switching capacity group 40 was big more, the pairing frequency band of voltage controlled oscillator output frequency can be narrow more.
Moreover voltage controlled oscillator is that frequency is adjusted constant (Kvco) with the constant definition of its reference frequency output and input voltage (Δ f/ Δ V).As shown in Figure 2, when the output frequency of known voltage controlled oscillator is frequently low more frequency adjust constant can be more little, that is to say that known voltage controlled oscillator can't provide a fixing frequency to adjust constant.Angle the designer, when frequency adjustment constant can change along with the output frequency variation, the circuit design of whole phase-locked loop can be very complicated, especially is connected in the previous circuit unit of voltage controlled oscillator in the phase-locked loop, relevant for the design of loop filter (Loop Filter).
Summary of the invention
The purpose of this invention is to provide a kind of variable capacitor that is used in the voltage controlled oscillator, make this voltage controlled oscillator have fixed frequency and adjust constant.
The present invention proposes an a kind of variable capacitor that is used in the voltage controlled oscillator, comprise: a switching capacity group, this switching capacity group comprises N capacitive branch, each this capacitive branch has a switch control end, in order to control being connected or not connecting between a first node and the Section Point, wherein, each this capacitive branch that is connected between this first node and this Section Point all can provide a capacitance; And, one switch transfiguration group, this switch transfiguration group comprises a N transfiguration branch road and a voltage controling end, each this transfiguration branch road has a switch control end and reaches man-to-man corresponding annexation with the switch control end of those capacitive branch, and each this transfiguration branch road all can be finished being connected or not connecting between this first node and this Section Point via the control of this switch control end, wherein, each this transfiguration branch road that is connected between this first node and this Section Point provides a variable capacitance according to the voltage that this voltage controling end provided.
A variable capacitor that is used in the voltage controlled oscillator of the present invention, wherein, each this transfiguration branch road comprises one first capacitor that is series between this first node and this Section Point, one first variable capacitance diode, one switching circuit, one second variable capacitance diode and one second capacitor, wherein, one first end of this first capacitor is connected to this first node, one second end of this first capacitor is connected to the cathode terminal of this first variable capacitance diode, the anode tap of this first variable capacitance diode is connected to one first end of this switching circuit, one second end of this switching circuit is connected to the anode tap of this second variable capacitance diode, the cathode terminal of this second variable capacitance diode is connected to this second capacitor, one first end, and this second capacitor, one second end is connected to this Section Point.
Wherein, this first variable capacitance diode in each this transfiguration branch road and second variable capacitance diode can be controlled the depletion width of this first variable capacitance diode and this second variable capacitance diode according to this voltage that this voltage controling end provides, and then adjust this variable capacitance.
A described variable capacitor that is used in the voltage controlled oscillator, wherein, this transfiguration branch road also comprises:
One inverter, this switch control end is connected to the input of this inverter;
One first resistance is connected between the control end and switch control end of this switching circuit;
One the 5th P transistor npn npn is connected one second resistance between the anode tap of the source electrode of the 5th P transistor npn npn and this second variable capacitance diode, and the grid of this five P transistor npn npn is connected to this switch control end, and the drain electrode of the 5th P transistor npn npn is connected to a voltage source;
One the 4th N transistor npn npn, the drain electrode of the 4th N transistor npn npn is connected to the source electrode of the 5th P transistor npn npn, and the grid of the 4th N transistor npn npn is connected to this switch control end, and the source electrode of the 4th N transistor npn npn is connected to an earth terminal;
One the 6th P transistor npn npn is connected one the 3rd resistance between the cathode terminal of the source electrode of the 6th P transistor npn npn and this second variable capacitance diode, and the grid of the 6th P transistor npn npn is connected to this switch control end, and the drain electrode of the 6th P transistor npn npn is connected to this voltage source;
One the 5th N transistor npn npn, the drain electrode of the 5th N transistor npn npn is connected to the source electrode of the 6th P transistor npn npn, the grid of the 5th N transistor npn npn is connected to this switch control end, is connected one the 6th resistance between the source electrode of the 5th N transistor npn npn and this voltage controling end;
One the 7th P transistor npn npn, the source electrode of the 7th P transistor npn npn are connected to the 6th P transistor npn npn source electrode, and the grid of the 7th P transistor npn npn is connected to the output of this inverter, and the drain electrode of the 7th P transistor npn npn is connected to the source electrode of the 5th N transistor npn npn;
One the 4th P transistor npn npn is connected one the 4th resistance between the anode tap of the source electrode of the 4th P transistor npn npn and this first variable capacitance diode, and the grid of the 4th P transistor npn npn is connected to this switch control end, and the drain electrode of the 4th P transistor npn npn is connected to this voltage source;
One the 3rd N transistor npn npn, the drain electrode of the 3rd N transistor npn npn are connected to the 4th P transistor npn npn source electrode, and the grid of the 3rd N transistor npn npn is connected to this switch control end, and the source electrode of the 3rd N transistor npn npn is connected to this earth terminal;
One the 3rd P transistor npn npn is connected one the 5th resistance between the cathode terminal of the source electrode of the 3rd P transistor npn npn and this first variable capacitance diode, and the grid of the 3rd P transistor npn npn is connected to this switch control end, and the drain electrode of the 3rd P transistor npn npn is connected to this voltage source;
One the 2nd N transistor npn npn, the drain electrode of the 2nd N transistor npn npn is connected to the source electrode of the 3rd P transistor npn npn, the grid of the 2nd N transistor npn npn is connected to this switch control end, is connected the 6th resistance between the source electrode of the 2nd N transistor npn npn and this voltage controling end; And
One the 2nd P transistor npn npn, the source electrode of the 2nd P transistor npn npn is connected to the source electrode of the 3rd P transistor npn npn, and the grid of the 2nd P transistor npn npn is connected to the output of this inverter, and the drain electrode of the 2nd P transistor npn npn is connected to the source electrode of the 2nd N transistor npn npn.
Wherein, this switching circuit is a field-effect transistor, and a grid of this field-effect transistor is the control end of this switching circuit, links to each other with described first resistance.
The present invention is by providing a variable capacitor, comprise a switch transfiguration group and a switching capacity group in this variable capacitor, wherein the transfiguration branch road of switch transfiguration group is corresponding one by one with the capacitive branch of switching capacity group, when the switching capacity group inserts capacitance variations, switch transfiguration group provides the variable capacitance range of variation accordingly, when this variable capacitor is used for voltage controlled oscillator, the variable capacitance scope that makes each transfiguration branch road be provided via design can compensate the width of frequency band, keep the width unanimity of each frequency band, thereby can maintain a fixed value so that the frequency of voltage controlled oscillator is adjusted constant (Kvco), make the design simplification of phase-locked loop.
Description of drawings
Fig. 1 illustrate is known voltage controlled oscillator schematic diagram;
Fig. 2 illustrate is the output frequency schematic diagram of known voltage controlled oscillator;
Fig. 3 illustrate is used in variable capacitor in the voltage controlled oscillator for the present invention;
Fig. 4 illustrate is switch transfiguration group of the present invention;
Fig. 5 illustrate is the circuit diagram of a transfiguration branch road of the present invention;
Fig. 6 illustrate is the output frequency schematic diagram of voltage controlled oscillator of the present invention.
Embodiment
Please refer to Fig. 3, its illustrate is used in variable capacitor in the voltage controlled oscillator for the present invention.This variable capacitor is connected between node c and the node d, this variable capacitor comprises a switching capacity group (Switch Capacitance Bank) 140 and one switch transfiguration group (Switch Varactor Bank) 142, wherein, switching capacity group 140 is to be used for the output frequency of coarse adjustment voltage controlled oscillator, and switch transfiguration group 142 is the output frequencies that are used for finely tuning voltage controlled oscillator.
As shown in the figure, switching capacity group 140 and switch transfiguration group 142 are parallel between node c and the node d.Under small signal model, insert an inductor (L) between node c and the node d and make this inductor and this variable capacitor form a LC oscillating circuit.Moreover the structure of switching capacity group 140 can be similar to the known switch capacitance group, and it has a plurality of capacitive branch, and each capacitive branch all has a switch control end, those capacitive branch can reach via control with node c and node d between be connected or do not connect.When capacitive branch was connected between node c and the node d, the equivalent capacitance value of variable capacitor will increase; In like manner, when capacitive branch was not attached between node c and the node d, the equivalent capacitance value of variable capacitor will reduce.Because the form of the switching capacity group in the voltage controlled oscillator is not limited in the switching capacity group 40 among Fig. 1, that is to say the not structure of limit switch capacitance group of the present invention.
Moreover switch transfiguration group 142 includes a plurality of transfiguration branch roads, and each transfiguration branch road all has a switch control end, and the switch control end of each transfiguration branch road all can be connected to the switch control end of a capacitive branch in this switching capacity group 140.That is to say, those capacitive branch are man-to-man corresponding (One to OneCorrespondence) in those transfiguration branch roads of switch transfiguration group 142 and this switching capacity group 140, when a capacitive branch is reached being connected between node c and the node d via control, simultaneously, corresponding transfiguration branch road also can be reached being connected between node c and the node d.
Moreover, all transfiguration branch roads all are connected to a voltage controling end, via the change in voltage that this voltage controling end provided, can make the capacitance that is connected on the transfiguration branch road between node c and the node d change, and then reach the variation of voltage controlled oscillator output frequency.
Because the known variable capacitance scope of capacity-changing unit is fixed, and therefore, can cause the frequency adjustable scope difference of each frequency band, thereby cause unfixed frequency to adjust constant (Kvco).And use switch transfiguration group 142 provided by the present invention, via making that the frequency adjustable scope of each frequency band is identical after the design, can reach and have fixing frequency and adjust constant (Kvco).
Please refer to Fig. 4, its illustrate is switch transfiguration group of the present invention.This switch transfiguration group 142 includes n transfiguration branch road, it is respectively 150～15n, each transfiguration branch road all has a switch control end 160～16n, and the switch control end of each transfiguration branch road all can be connected to the switch control end of corresponding capacitive branch in this switching capacity group 140.That is to say that when the first switch control end 161 control, the first transfiguration branch road 151 was reached being connected between node c and the node d, corresponding first capacitive branch also can be reached being connected between node c and the node d.Moreover, each transfiguration branch road comprises variable capacitance diode (Varicap Diode) at least, so voltage controling end can make the change that the depletion width (Depletion Layer Width) of variable capacitance diode changes and then reach capacitance via changing magnitude of voltage.Moreover capister also can replace with known capacity-changing unit 42, the change that voltage controling end provides the magnitude of voltage of variation to make the voltage difference between field-effect transistor drain electrode and the grid, and then the change of reaching capacitance.
Please refer to Fig. 5, its illustrate is the circuit diagram of a transfiguration branch road of the present invention.Connect in regular turn between node c and the node d first capacitor (C1), first variable capacitance diode (VCD1), switching transistor (Mn6), second variable capacitance diode (VCD2), second capacitor (C2).Wherein, one end of first capacitor (C1) is connected to node c, the other end of first capacitor (C1) is connected to the cathode terminal (Kathode) of first variable capacitance diode (VCD1), the anode tap (Anode) of first variable capacitance diode (VCD1) is connected to an end of switching transistor (Mn6), the other end of switching transistor (Mn6) is connected to the anode tap of second variable capacitance diode (VCD2), the cathode terminal of second variable capacitance diode (VCD2) is connected to second capacitor (C2) end, and second capacitor (C2) other end is connected to node d.
Moreover, control circuit in this transfiguration branch road comprises: a P transistor npn npn (Mp1) connects into an inverter (Not Gate) with a N transistor npn npn (Mn1), and the switch control end is connected to the inverter input grid of a P transistor npn npn (Mp1) and a N transistor npn npn (Mn1) just, and inverter output is the drain electrode of a P transistor npn npn (Mp1) and a N transistor npn npn (Mn1).Moreover, be connected one first resistance (R1) between the control end of this switching transistor (Mn6) and the switch control end.Be connected one second resistance (R2) between the anode tap of second variable capacitance diode (VCD2) and the 5th P transistor npn npn (Mp5) source electrode, the 5th P transistor npn npn (Mp5) grid is connected to the switch control end, and the drain electrode of the 5th P transistor npn npn (Mp5) is connected to voltage source (Vcc); The drain electrode of the 4th N transistor npn npn (Mn4) is connected to the 5th P transistor npn npn (Mp5) source electrode, and the 4th N transistor npn npn (Mn4) grid is connected to the switch control end, and the 4th N transistor npn npn (Mn4) source electrode is connected to earth terminal.Be connected one the 3rd resistance (R3) between the cathode terminal of second variable capacitance diode (VCD2) and the 6th P transistor npn npn (Mp6) source electrode, the 6th P transistor npn npn (Mp6) grid is connected to the switch control end, and the drain electrode of the 6th P transistor npn npn (Mp6) is connected to voltage source (Vcc); The 5th N transistor npn npn (Mn5) drain electrode is connected to the 6th P transistor npn npn (Mp6) source electrode, and the 5th N transistor npn npn (Mn5) grid is connected to the switch control end, is connected one the 6th resistance (R6) between the 5th N transistor npn npn (Mn5) source electrode and the voltage controling end; The 7th P transistor npn npn (Mp7) source electrode is connected to the 6th P transistor npn npn (Mp6) source electrode, and the 7th P transistor npn npn (Mp7) grid is connected to inverter output, and the drain electrode of the 7th P transistor npn npn (Mp7) is connected to the 5th N transistor npn npn (Mn5) source electrode.Be connected one the 4th resistance (R4) between the anode tap of first variable capacitance diode (VCD1) and the 4th P transistor npn npn (Mp4) source electrode, the 4th P transistor npn npn (Mp4) grid is connected to the switch control end, and the drain electrode of the 4th P transistor npn npn (Mp4) is connected to voltage source (Vcc); The drain electrode of the 3rd N transistor npn npn (Mn3) is connected to the 4th P transistor npn npn (Mp4) source electrode, and the 3rd N transistor npn npn (Mn3) grid is connected to the switch control end, and the 3rd N transistor npn npn (Mn3) source electrode is connected to earth terminal.Be connected one the 5th resistance (R5) between the cathode terminal of first variable capacitance diode (VCD1) and the 3rd P transistor npn npn (Mp3) source electrode, the 3rd P transistor npn npn (Mp3) grid is connected to the switch control end, and the drain electrode of the 3rd P transistor npn npn (Mp3) is connected to voltage source (Vcc); The 2nd N transistor npn npn (Mn2) drain electrode is connected to the 3rd P transistor npn npn (Mp3) source electrode, and the 2nd N transistor npn npn (Mn2) grid is connected to the switch control end, is connected one the 6th resistance (R6) between the 2nd N transistor npn npn (Mn2) source electrode and the voltage controling end; The 2nd P transistor npn npn (Mp2) source electrode is connected to the 3rd P transistor npn npn (Mp3) source electrode, and the 2nd P transistor npn npn (Mp2) grid is connected to inverter output, and the drain electrode of the 2nd P transistor npn npn (Mp2) is connected to the 2nd N transistor npn npn (Mn2) source electrode.
When the switch control end provides a high level, inverter output can be exported a low level, switching transistor (Mn6), the 2nd P transistor npn npn (Mp2), the 2nd N transistor npn npn (Mn2), the 3rd N transistor npn npn (Mn3), the 4th N transistor npn npn (Mn4), the 5th N transistor npn npn (Mn5) and the 7th P transistor npn npn (Mp7) all can conductings (On), and the 3rd P transistor npn npn (Mp3), the 4th P transistor npn npn (Mp4), the 5th P transistor npn npn (Mp5) all can end (Off) with the 6th P transistor npn npn (Mp6).Therefore, the transfiguration branch road is connected between node c and the node d and the anode tap of first variable capacitance diode (VCD1) is connected to earth terminal and the cathode terminal of first variable capacitance diode (VCD1) is connected to voltage controling end causes first variable capacitance diode (VCD1) reverse biased (Reverse Bias), therefore the voltage on the voltage controling end promptly can be controlled the capacitance of first variable capacitance diode (VCD1), in like manner, the anode tap of second variable capacitance diode (VCD2) is connected to earth terminal and the cathode terminal of second variable capacitance diode (VCD2) is connected to voltage controling end causes second variable capacitance diode (VCD2) reverse biased, so the voltage on the voltage controling end also can be controlled the capacitance of second variable capacitance diode (VCD1).And when this transfiguration branch road was connected between node c and the node d, the series connection of first capacitor (C1), first variable capacitance diode (VCD1), second variable capacitance diode (VCD2), second capacitor (C2) was the capacitor equivalent value of this transfiguration branch road.And, can change the capacitor equivalent value of controlled path via the voltage that changes voltage controling end.
When the switch control end provides low level, inverter output can be exported high level, switching transistor (Mn6), the 2nd P transistor npn npn (Mp2), the 2nd N transistor npn npn (Mn2), the 3rd N transistor npn npn (Mn3), the 4th N transistor npn npn (Mn4), the 5th N transistor npn npn (Mn5), the 7th P transistor npn npn (Mp7) end, the 3rd P transistor npn npn (Mp3), the 4th P transistor npn npn (Mp4), the 5th P transistor npn npn (Mp5) and the 6th P transistor npn npn (Mp6) meeting conducting.Therefore, the transfiguration branch road is not attached between node c and the node d and the cathode terminal of first variable capacitance diode (VCD1) and anode tap are connected to voltage source (Vcc), so can't cause the reverse biased of first variable capacitance diode (VCD1), in like manner, the cathode terminal of second variable capacitance diode (VCD2) and anode tap are connected to voltage source (Vcc), therefore can't cause the reverse biased of second variable capacitance diode (VCD2).
Please refer to the 6th figure, its illustrate is the output frequency schematic diagram of voltage controlled oscillator of the present invention.By among the figure as can be known, the adjustable output frequency interval of voltage controlled oscillator is between f0 '～f7 '; Wherein, first frequency band (Band) I (f5 '～f7 ') is that the variable capacitance scope (Δ c1) that the first transfiguration branch road of one first capacitance (c1) that provides of first capacitive branch by switching capacity group 140 and switch transfiguration group 142 provides is finished; The second frequency band II (f3 '～f6 ') is that this first capacitance that first capacitive branch and second capacitive branch by switching capacity group 140 provides adds that first transfiguration branch road of one second capacitance (c1+c2) and switch transfiguration group 142 and the variable capacitance scope that the second transfiguration branch road provides (Δ c1+ Δ c2) finish; The 3rd frequency band III (f1 '～f4 ') is that this first capacitance that first capacitive branch, second capacitive branch, the 3rd capacitive branch by switching capacity group 140 provides adds that the variable capacitance scope that this second capacitance adds the first transfiguration branch road, the second transfiguration branch road, the 3rd transfiguration branch road of one the 3rd capacitance (c1+c2+c3) and switch transfiguration group 142 to be provided (Δ c1+ Δ c2+ Δ c3) finishes; Wherein, the 4th frequency band IV (f0 '～f2 ') is that first capacitance that first capacitive branch, second capacitive branch, the 3rd capacitive branch, the 4th capacitive branch by switching capacity group 140 provide adds that the variable capacitance scope (Δ c1+ Δ c2+ Δ c3+ Δ c4) that this second capacitance adds that the 3rd capacitance adds the first transfiguration branch road, the second transfiguration branch road, the 3rd transfiguration branch road, the 4th transfiguration branch road of one the 4th capacitance (c1+c2+c3+c4) and switch transfiguration group 142 to be provided finishes.
Because the output frequency of voltage controlled oscillator is to be proportional to
Therefore, when the capacitive branch number that is connected in node c and node d increases, the transfiguration number of branches that is connected in node c and node d relatively also can increase, therefore, the variable capacitance scope that switch transfiguration group 142 is provided can become big, therefore the variable capacitance scope that is provided via each transfiguration branch road of design promptly can compensate the width of frequency band, makes the width of each frequency band keep unanimity.And utilize switch transfiguration group 142 provided by the present invention to make when the width of each frequency band is kept unanimity, and can determine that its frequency adjusts constant (Kvco) and can maintain a fixed value, make the design simplification of phase-locked loop.
In sum; though the present invention discloses as above with preferred embodiment; right its is not in order to limit the present invention; those skilled in the art; without departing from the spirit and scope of the present invention; when can doing various changes and retouching, so protection scope of the present invention is as the criterion with the appended claim scope in back.
Claims (3)
1, an a kind of variable capacitor that is used in the voltage-controlled oscillator (VCO) comprises:
One switching capacity group, this switching capacity group comprises N capacitive branch, each this capacitive branch has a switch control end, in order to control being connected or not connecting between a first node and the Section Point, wherein, each this capacitive branch that is connected between this first node and this Section Point all can provide a capacitance; And
One switch transfiguration group, this switch transfiguration group comprises a N transfiguration branch road and a voltage controling end, each this transfiguration branch road has a switch control end and reaches man-to-man corresponding annexation with the switch control end of those capacitive branch, and each this transfiguration branch road all can be finished being connected or not connecting between this first node and this Section Point via the control of this switch control end, wherein, each this transfiguration branch road that is connected between this first node and this Section Point provides a variable capacitance according to the voltage that this voltage controling end provided, wherein:
Each this transfiguration branch road comprises one first capacitor that is series between this first node and this Section Point, one first variable capacitance diode, one switching circuit, one second variable capacitance diode and one second capacitor, wherein, one first end of this first capacitor is connected to this first node, one second end of this first capacitor is connected to the cathode terminal of this first variable capacitance diode, the anode tap of this first variable capacitance diode is connected to one first end of this switching circuit, one second end of this switching circuit is connected to the anode tap of this second variable capacitance diode, the cathode terminal of this second variable capacitance diode is connected to this second capacitor, one first end, and this second capacitor, one second end is connected to this Section Point;
This transfiguration branch road also comprises:
One inverter, this switch control end is connected to the input of this inverter;
One first resistance is connected between the control end and switch control end of this switching circuit;
One the 5th P transistor npn npn is connected one second resistance between the anode tap of the source electrode of the 5th P transistor npn npn and this second variable capacitance diode, and the grid of this five P transistor npn npn is connected to this switch control end, and the drain electrode of the 5th P transistor npn npn is connected to a voltage source;
One the 4th N transistor npn npn, the drain electrode of the 4th N transistor npn npn is connected to the source electrode of the 5th P transistor npn npn, and the grid of the 4th N transistor npn npn is connected to this switch control end, and the source electrode of the 4th N transistor npn npn is connected to an earth terminal;
One the 6th P transistor npn npn is connected one the 3rd resistance between the cathode terminal of the source electrode of the 6th P transistor npn npn and this second variable capacitance diode, and the grid of the 6th P transistor npn npn is connected to this switch control end, and the drain electrode of the 6th P transistor npn npn is connected to this voltage source;
One the 5th N transistor npn npn, the drain electrode of the 5th N transistor npn npn is connected to the source electrode of the 6th P transistor npn npn, the grid of the 5th N transistor npn npn is connected to this switch control end, is connected one the 6th resistance between the source electrode of the 5th N transistor npn npn and this voltage controling end;
One the 7th P transistor npn npn, the source electrode of the 7th P transistor npn npn are connected to the 6th P transistor npn npn source electrode, and the grid of the 7th P transistor npn npn is connected to the output of this inverter, and the drain electrode of the 7th P transistor npn npn is connected to the source electrode of the 5th N transistor npn npn;
One the 4th P transistor npn npn is connected one the 4th resistance between the anode tap of the source electrode of the 4th P transistor npn npn and this first variable capacitance diode, and the grid of the 4th P transistor npn npn is connected to this switch control end, and the drain electrode of the 4th P transistor npn npn is connected to this voltage source;
One the 3rd N transistor npn npn, the drain electrode of the 3rd N transistor npn npn are connected to the 4th P transistor npn npn source electrode, and the grid of the 3rd N transistor npn npn is connected to this switch control end, and the source electrode of the 3rd N transistor npn npn is connected to this earth terminal;
One the 3rd P transistor npn npn is connected one the 5th resistance between the cathode terminal of the source electrode of the 3rd P transistor npn npn and this first variable capacitance diode, and the grid of the 3rd P transistor npn npn is connected to this switch control end, and the drain electrode of the 3rd P transistor npn npn is connected to this voltage source;
One the 2nd N transistor npn npn, the drain electrode of the 2nd N transistor npn npn is connected to the source electrode of the 3rd P transistor npn npn, the grid of the 2nd N transistor npn npn is connected to this switch control end, is connected the 6th resistance between the source electrode of the 2nd N transistor npn npn and this voltage controling end; And
One the 2nd P transistor npn npn, the source electrode of the 2nd P transistor npn npn is connected to the source electrode of the 3rd P transistor npn npn, and the grid of the 2nd P transistor npn npn is connected to the output of this inverter, and the drain electrode of the 2nd P transistor npn npn is connected to the source electrode of the 2nd N transistor npn npn.
2, a variable capacitor that is used in the voltage-controlled oscillator (VCO) as claimed in claim 1, wherein, this switching circuit is a field-effect transistor, and a grid of this field-effect transistor is the control end of this switching circuit, links to each other with described first resistance.
3, a variable capacitor that is used in the voltage-controlled oscillator (VCO) as claimed in claim 1, wherein, this first variable capacitance diode in each this transfiguration branch road and second variable capacitance diode can be controlled the depletion width of this first variable capacitance diode and this second variable capacitance diode according to this voltage that this voltage controling end provides, and then adjust this variable capacitance.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102916686A (en) * | 2012-11-02 | 2013-02-06 | 长沙景嘉微电子股份有限公司 | Improved switch capacitor structure with low parasitic effect and high quality factor |
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| US8242854B2 (en) | 2009-06-30 | 2012-08-14 | Qualcomm, Incorporated | Enhancing device reliability for voltage controlled oscillator (VCO) buffers under high voltage swing conditions |
| US20120286888A1 (en) * | 2011-05-09 | 2012-11-15 | Taiwan Semiconductor Manufacturing Company, Ltd. | Switched Capacitor Array for Voltage Controlled Oscillator |
| KR101873300B1 (en) * | 2012-01-30 | 2018-07-02 | 삼성전자주식회사 | Voltage controlled oscillator using variable capacitor and phase locked loop thereof |
| CN106850937A (en) * | 2016-09-09 | 2017-06-13 | 联发科技（新加坡）私人有限公司 | Mobile terminal and overcome crystal aging method for searching network |
| CN111951721B (en) * | 2020-08-24 | 2021-11-02 | 上海天马微电子有限公司 | Driving back plate, light-emitting panel, display device and forming method |
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| CN102916686A (en) * | 2012-11-02 | 2013-02-06 | 长沙景嘉微电子股份有限公司 | Improved switch capacitor structure with low parasitic effect and high quality factor |
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