CN102545783B - LC voltage-controlled oscillator (LC-VCO) with wide frequency tuning range - Google Patents

Abstract

The invention provides an LC voltage-controlled oscillator (LC-VCO) with a wide frequency tuning range based on an equivalent resonant capacitor; and the equivalent resonant capacitor of a differential circuit structure module comprises an accumulated variable capacitor (AMOS) with the bias voltage being controlled by a switch and a plurality of fixed capacitors which are controlled by the switches. In a high-frequency band, the bias voltage which is controlled by the switch enables the AMOS variable capacitor to work in an area in which the capacitor is not sensitive to the voltage; the AMOS capacitor is equivalent to the fixed capacitors, the noise which is introduced by a bias circuit is reduced, and a higher Q value is realized. In a low-frequency band, the bias voltage which is controlled by the switch enables the AMOS variable capacitor to work in a variable capacity interval, the proportion of the variable capacitance in the loop of the equivalent resonant capacitor is increased, the gains or the low-frequency band VCO are increased, so that the LC-VCO with low noise and the wide frequency tuning range is realized. Compared with an existing broad-band VCO, the wide frequency tuning range is realized to a circuit module with an appropriate amount of switch capacitance, and the LC-VCO with wide frequency tuning range has the characteristics of low power consumption and small chip area.

Description

A kind of wide frequency tuning range LC-VCO

Technical field

The present invention relates to wireless communication electronics circuit engineering field, relate to inductance, capacitance voltage-controlled oscillator VCO, particularly relate to implementation method and the circuit module thereof of wide frequency tuning range LC-VCO.

Background technology

Multi-mode, multiband receiver require that VCO has very large frequency tuning range, and on sheet, the tuning range of LC is limited, and therefore, research broadband VCO technology has great importance.Realizing the broadband the simplest technology of VCO adopts two or more VCO on the same chip integrated exactly, and the output of these VCO selects a road to export by variable connector, therefore, any time only has a VCO in working order, the method can realize the rate-adaptive pacemaker of any range, but need to adopt multiple on-chip inductor, therefore chip area is large, and engineering is not suitable for.In addition, by increasing the voltage gain K of VCO _vCOcan realize wider bandwidth to a certain extent, but the method has two problems, first, with conventional capacitance tuning formula VCO, the adjustable ratio of electric capacity is limited, limits by device self character, secondly, and the K of VCO _vCOtoo large, the noise in control voltage also increases to the gain of rate-adaptive pacemaker, and therefore phase noise can be deteriorated.At present, the most frequently used broadband VCO has two kinds, and one is capacitance switch formula, and another kind is inductance switch formula.In addition also have this to adopt the broadband VCO of these two kinds of switching modes simultaneously.

The maximum advantage of inductance suitching type broadband VCO to realize very large frequency tuning range, but inductance switch is larger on circuit performance impact, because in low GHz frequency range, the Q value of inductance is much smaller than the Q value of electric capacity, Q value is general below 10, and therefore, the conducting resistance of switching tube can reduce the Q value of inductance further, can increase the power consumption of circuit on the one hand, phase noise performance declines simultaneously.In addition, when the conducting of MOS switching tube, inductance is operated in short-circuit condition, and therefore, inductance now can produce induced current due to the effect of mutual inductance, thus increases the loss of circuit further.When circuit work frequency raises, the Q value of inductance can become large thereupon, simultaneously, the Q value of electric capacity reduce because the loss increase of resistance can raise with frequency, when the Q value of inductance is greater than electric capacity Q value, the impact of MOS switching tube can be ignored, and therefore, inductance suitching type broadband VCO is applicable to tens of more than GHz operating frequency.

Capacitance switch formula broadband VCO can realize frequency tuning range in a big way, but when switch controlled capacitance group is more, the parasitic capacitance that switch controlled capacitance is introduced can increase and reduce frequency tuning range, in addition, because the Q value of on-chip inductor is more big changes with frequency, therefore, the span of switch controlled capacitance is subject to the value restriction of on-chip inductor.The defect of capacitance switch formula broadband VCO is: (1) frequency range is subject to the restriction of inductance and parasitic capacitance.(2) when switch controlled capacitance group is more, the conducting resistance of switch can reduce the equivalent Q-value of switched capacitances, thus can reduce phase noise performance.

Prior art " Low Phase Noise Voltage-controlled Oscillator design " is published in " semiconductor technology " 2007.11 and analyzes LC voltage controlled oscillator (VCO) phase noise, by improving circuit structure, PMOS and NMOS tube is adopted to do dynatron, at tail current source, place adds inductance capacitor filtering, optimize inductor design, devise a kind of high-performance voltage controlled oscillator.Adopt TSMC 0.18 μm of IP6M CMOS RF technique, utilize the Spectre RF instrument in Cadence to emulate circuit.When the bias current of circuit is 6mA, supply voltage VDD=1.8v, input control voltage is 0.8 ~ 1.8v, and output frequency is changed to 1.29 ~ 1.51GHz, and tuning range is 12.9%, and phase noise is-134.4dBc/Hz@1MHz, and power consumption is only 10.8mW.The major defect of this circuit is that frequency tuning range is narrow, and power consumption is comparatively large, can not meet low-power consumption wide frequency tuning range application scenario.

During micro-Xiao of middle section, luxuriant paper " low-power consumption broadband CMOS LC-VCO designs " is based on capacitance tuning without tail current source complementation-Gm VCO, proposes a kind of method of new broadband VCO optimised power consumption.Realize compensating capacitance-tuning curve by the bias voltage changing four accumulation type variable capacitances (AMOS), make frequency tuning curves close to linearisation within the scope of whole control voltage, thus realize wide frequency tuning range.A 3.0 ~ 3.6GHz frequency range LC-VCO of employing standard 0.18/ μm of IP6M RFCMOS technological design.Test result shows, whole VCO comprises in output is buffered in, and area is 0.45mm ², under being operated in 1.5V power supply, electric current is 1.8mA, and exporting phase noise is-93dBc/Hz in 200kHz skew place.The major defect of this circuit is that the ride gain of VCO is comparatively large, is unfavorable for realizing low phase noise.

Hangzhoupro electricity Cheng Zhi group theory literary composition " based on the research of CMOS technology broadband LC voltage controlled oscillator " is published in " electronic device " 2009.4 phase, devise a kind of broadband inductor electric capacity (LC) voltage controlled oscillator (VCO) being applied to wireless communication system, circuit adopts switched capacitor array to obtain broadband coverage; Switched varactor array is utilized to reduce tuning gain change; And obtain low phase noise by the differential inductance and noise filtering technique adopting high quality factor.Circuit design adopts SMIC0.18 μm of CMOS technology.Simulation result shows: when operating voltage is 1.8V, and DC power is 9mW, and the frequency range 0.87 ~ 1.5GHz (53%) of voltage controlled oscillator, tuning gain is between 67MHz/V to 72MHz/V.Phase noise is better than-100dBc/Hz@100kHz, and the major defect of this circuit is that chip occupying area is large.

Summary of the invention

The object of the invention is the defect overcoming existing capacitive switch switches formula VCO structure, disclose a kind of wide frequency tuning range inductor-capacitor voltage controlled oscillator LC-VCO based on equivalent tank capacitor.Equivalent tank capacitor E-Varactor is made up of the accumulation type electric capacity AMOS of switch control rule the fixed capacitor of multiple switch control rule and a bias voltage.

The object of the invention is achieved through the following technical solutions.A kind of wide frequency tuning range LC-VCO, it is the LC-VCO circuit module formed based on equivalent tank capacitor, comprises negative resistance amplifier 11, inductor 12, variable capacitor 13, and equivalent tank capacitor 14; Negative resistance amplifier 11, inductor 12, variable capacitor 13 and equivalent tank capacitor 14 are and are connected in parallel, and LC-VCO circuit module output is VP and VN; Wherein

Described variable capacitor 13 is that capacitance is with control voltage V _ctrlthe electric capacity C of change _v; Described equivalent tank capacitor 14 is the E-Varactor equivalent variable electric capacity C that capacitance is controlled by switches set and bias voltage _e; Variable capacitor 13 and equivalent tank capacitor 14 form total equivalent capacity C _z;

Described switches set comprises k1 ~ kn and ka and kb; Described bias voltage comprises two fixed voltages VB1, VB2 and a control voltage Vctrl;

Described inductor 12, total equivalent capacity C _zhumorous loop is imitated in the parallel connection formed with negative resistance amplifier 11, for determining output frequency and the quality factor of LC-VCO circuit module, total equivalent capacity is changed by control voltage, switch and bias voltage, for changing the output frequency of VCO circuit and to realize broadband tuning.

Described wide frequency tuning range LC-VCO, it is that the composition of described equivalent tank capacitor E-Varactor comprises: bias voltage by the AMOS variable capacitor of switch control rule to C _varwith the fixed capacitor group C of a switch control rule _g; Wherein

The fixed capacitor group 22 of described switch control rule comprises n to fixed capacitor C ₁~ Cn and n is to control switch K1 ~ Kn, and control signal k1 ~ kn that n outside; The n control signal outside to control switch and n is control connection one to one, often pair of fixed capacitor is for being connected in series, one end of often pair of fixed capacitor connects output VP by a control switch, and the other end all passes through a control switch and connects output VN; By the on-off of the control signal control switch of outside, control the right access of fixed capacitor or disconnection, for adjusting the fixed capacitor group C of switch control rule _gcapacitance, realize the coarse adjustment of equivalent tank condenser capacity, the parasitic capacitance of introducing can be reduced again;

Described bias voltage comprises 2 AMOS capacitor C by the AMOS variable capacitor of switch control rule to 21 _var, control switch ka and kb that 2 partiting dc capacitor C, 3 biasing resistor R and control signal Ka and Kb control; 2 AMOS capacitor C _varbe connected in series, series connection contact connects biasing resistor R, the series connection contact of other end connection control switch ka and kb of biasing resistor R, and the other end of control switch ka connects access External Control Voltage V _ctrlvC end, the other end of control switch kb connects the outside fixed bias voltage V of access _b1vB1 end; The other end of two AMOS capacitors is respectively connected in series a partiting dc capacitor C, and two series connection contacts respectively connect a biasing resistor R, and the other end of two biasing resistors is connected in parallel, and interface connects the outside fixed bias voltage V of access _b2vB2 end; Capacitance for AMOS electric capacity holds control voltage V with VC _ctrlchange and change, realizing the fine tuning of equivalent tank condenser capacity, obtain wide frequency tuning range.

In resonant frequencies rate section, external control signal ka is that logic level 0 control switch Ka disconnects, and external control signal kb is logic level 1 control switch Kb conducting, outside fixed bias voltage V _b1the series connection contact accessing two AMOS electric capacity through K switch b and biasing resistor R is held, outside fixed bias voltage V by VB1 _b2access VB2 end, access the other end of two AMOS electric capacity through biasing resistor R, in equivalent tank capacitor, the fixed bias voltage at AMOS two ends is V _b1and V _b2, the size of fixed bias voltage ensures that the capacitance of AMOS electric capacity is not with both end voltage change, and AMOS electric capacity is operated in the insensitive region of capacitance versus voltage, and AMOS capacitance is equivalent to a constant capacitance, and the capacitance of equivalent tank capacitor reduces; The noise introduced by biasing circuit is less, and resonant circuit has higher Q value;

In resonance low frequency section, external control signal ka is logic level 1 control switch Ka conducting, and external control signal kb is that logic level 0 control switch Kb disconnects, outside control voltage V _ctrlheld the series connection contact accessing two AMOS electric capacity in equivalent tank capacitor through control switch Ka and biasing resistor R by VC, two AMOS electric capacity other ends connect through biasing resistor R respectively and add V _b2vB2 end, the series connection end of AMOS electric capacity adds control voltage, and one end is fixed bias voltage, and make AMOS electric capacity be operated in variable capacitance interval, its capacitance is with control voltage V _ctrlchange and change, improve the gain of VCO, the capacitance of equivalent tank capacitor just becomes large, thus realizes the fine tuning of equivalent tank condenser capacity, obtains wide frequency tuning range.

Described wide frequency tuning range LC-VCO, it is that described LC-VCO circuit module is difference channel structure, two-pass DINSAR output VP and VN of circuit module is inductance two ends in electricity or electric capacity two ends, and the amplitude output signal of two-pass DINSAR output is equal, and phase place is contrary.

Described wide frequency tuning range LC-VCO, it is that the negative resistance amplifier-G circuit of described LC-VCO circuit module is the differential negative resistance amplifier be made up of cross-linked metal-oxide-semiconductor or BJT pipe, stablizes for the amplitude output signal controlling voltage controlled oscillator VCO.

Described wide frequency tuning range LC-VCO, it is that the inductor that described LC-VCO circuit module comprises is the fixed inductor of the on-chip spiral inductor adopting high-quality-factor, and its inductance value is L.

Described wide frequency tuning range LC-VCO, it is the RF variable capacitor C based on CMOS technology that the variable capacitor 13 that described VCO circuit module comprises connects for pair of series _v, two variable capacitors are connected in series end connection control voltage V _ctrl, its capacitance is with control voltage V _ctrlchange and change, capacitance presents monotone variation with the change of control voltage.

Described wide frequency tuning range LC-VCO, it is the described control voltage V from outside _ctrlfor the frequency tuning voltage of VCO, the VC end of access VCO circuit module, control voltage V _ctrlbe used for arranging the frequency of VCO, the frequency of VCO is consecutive variations with control voltage change, makes VCO be operated in required Frequency point.

Described wide frequency tuning range LC-VCO, it is that described broadband is tuned as differentially tuned structure, adopt a pair AMOS variable capacitance, by changing the bias voltage of a pair AMOS variable capacitance, realize the tuning curve of the LC-VCO circuit module formed based on equivalent tank capacitor, for reducing the tuning gain of VCO, realize wideband, low noise and low consumption LC-VCO;

Described AMOS electric capacity is a kind of voltage controlled variable electric capacity of accumulation type, and on this sheet, voltage control variable capacitance is the NMOS tube being placed in N trap, and two ports of this AMOS electric capacity are respectively grid and substrate.

Described wide frequency tuning range LC-VCO, it is that each control switch of described n to control switch K1 ~ Kn is NMOS tube, has little conducting resistance; The pair of switches pipe that control signal ka and kb correspondence controls is NMOS tube, any time, and only have a switch to be conducting state in the pair of switches pipe that control signal ka and kb controls, another switch is off state; Described control signal ka and kb or be kab, control signal kab forms-kab by inverter, and control signal kab and-kab correspondence controls pair of switches pipe.

Described wide frequency tuning range LC-VCO, it is that the n in the fixed capacity group of described switch control rule adopts connecting electricity in n to switch to fixed capacity, and the span of n is 2 ~ 5; N preferred value depends on the loss of the gain of frequency tuning range, control voltage, chip area, AMOS electric capacity.N value is bigger than normal, and total equivalent capacity coarse adjustment shelves increase, and frequency tuning range can increase, but on-chip circuit is more complex, and the parasitic capacitance that switch is introduced increases, and due to the loss that switching tube is introduced, power consumption also can strengthen.As little in n value, have impact to wide frequency tuning range, if can meet frequency tuning range requirement, then circuit is simpler, and introduce noise little, because of the loss of AMOS electric capacity, power consumption is also little.

The present invention easily preferably reduces the quantity of capacitance switch, therefore conducting resistance loss is little, realize compensating capacitance-tuning curve by the bias voltage changing two accumulation type variable capacitance AMOS, make frequency tuning curves within the scope of whole control voltage close to linear, realize wide frequency tuning range, the ride gain needed for VCO is less, is conducive to realizing low phase noise, when same tuning range, the power consumption needed for VCO of the present invention, phase noise and chip area are all less.LC-VCO of the present invention adopts whole CMOS integrated, and all elements of VCO can adopt standard CMOS process, mature technology, is easy to technique and realizes.

Substantial effect of the present invention:

(1) when VCO is operated in high-frequency frequency range, resonant tank total capacitance value is less, in equivalent tank capacitor, AMOS is operated in fixed capacity district, it is equivalent to fixed capacitor, AMOS electric capacity is larger in the Q value of service area, AMOS and fixed capacity have close performance, and therefore, VCO of the present invention has good low phase noise.

(2), when VCO is operated in low frequency frequency range, resonant tank total capacitance value is comparatively large, and AMOS electric capacity is operated in variable capacitance district, increases the ratio of resonant tank variable capacitance, improves the control voltage gain K of low-frequency range VCO _vCO, therefore, under same wide frequency tuning range requires, VCO of the present invention can reduce the fixed capacity group number of switch control rule, both can reduce the loss of switch conduction resistance, improves the Q value of resonant tank, can reduce again the parasitic capacitance that switch is introduced.Under the condition of same variable capacitance, increase the resonant tank ratio of varying capacitance, the VCO easily extensible of the present invention frequency tuning range of resonant tank.

(3) quantity of capacitance switch is easily preferably reduced, therefore conducting resistance loss is little, realize compensating capacitance-tuning curve by the bias voltage changing two accumulation type variable capacitance AMOS, make frequency tuning curves within the scope of whole control voltage close to linear, realize wide frequency tuning range, the ride gain needed for VCO is less, is conducive to realizing low phase noise, when same tuning range, the power consumption needed for VCO of the present invention, phase noise and chip area are all less.

(4) this VCO adopts whole CMOS integrated, and all elements of VCO can adopt standard CMOS process, mature technology, is easy to technique and realizes.

(5) wide frequency tuning range LC-VCO of the present invention, can be applied to various rf broadband high-performance and receive in emitter chip.

Accompanying drawing explanation

Fig. 1 is equivalent tank capacitor arrangement schematic diagram.

Fig. 2 a is the function structure chart of the equivalent tank capacitor of the embodiment of the present invention 1 wide frequency tuning range VCO.

Fig. 2 b is the modular structure schematic diagram of the equivalent tank capacitor of Fig. 2 a embodiment of the present invention 1 wide frequency tuning range VCO.

Fig. 2 c is the structural representation of AMOS type variable capacitance in the modular structure of Fig. 2 b equivalent tank capacitor.

Fig. 2 d is the component symbol figure of Fig. 2 cAMOS type variable capacitance.

Fig. 3 a is the principle of compositionality figure of the embodiment of the present invention 2 based on the concrete n=2 of wide frequency ranges VCO of equivalent tank capacitor.

Fig. 3 b is Fig. 3 a embodiment of the present invention 2 based on the electrical schematic diagram of the concrete n=2 of wide frequency ranges VCO of equivalent tank capacitor and the equivalent tank capacitor of a pair AMOS variable capacitance.

Fig. 4 a is the principle of compositionality figure of the embodiment of the present invention 3 based on the concrete n=3 of wide frequency ranges VCO of equivalent tank capacitor.

Fig. 4 b is Fig. 4 a embodiment of the present invention 3 based on the electrical schematic diagram of the concrete n=3 of wide frequency ranges VCO of equivalent tank capacitor and the equivalent tank capacitor of a pair AMOS variable capacitance.

Embodiment

Also by reference to the accompanying drawings technical solution of the present invention is described in detail below by embodiments of the invention.

Based on equivalent tank capacitor wide frequency tuning range inductor-capacitor voltage controlled oscillator LC-VCO as shown in Figure 1, LC-VCO is by active negative resistance circuit 11, inductor 12, variable capacitor (Varactor) 13 and equivalent tank capacitor (E-Varactor) 14 form.In Fig. 1 ,-Gm is active negative resistance circuit 11, and active negative resistance adopts cross-linked metal-oxide-semiconductor to form.Active negative resistance realizes compensating the resistance loss of resonant tank, and when active negative resistance is equal with the resistance loss of resonant tank, VCO meets starting condition for oscillation, and VCO exports the sine wave signal of constant amplitude.The inductance of on chip spiral inductor device 12 is L, is made up of, can improves the Q of inductance the thick metal of top layer in chip, reduces resistance loss.Varactor variable capacitor 13 is the main tuned cell of VCO, the element that it is changed with control voltage by capacitance realizes, can be variable capacitance diode or AMOS electric capacity, when the capacitance of variable capacitor changes with control voltage, the resonance frequency of VCO changes with control voltage change.

Embodiment 1

As shown in Figure 2 a, Fig. 2 b is the circuit theory diagrams of the equivalent tank capacitor 14 of Fig. 2 a VCO of the present invention to the equivalent tank capacitor 14 of VCO of the present invention.This equivalent resonant capacitor circuit comprises bang-bang control variable capacitance 21 and bang-bang control fixed capacity 22, and circuit adopts differential symmetry structure, C ₁, C ₂..., C _nfor fixed capacity, k1, k2 ..., kn is the control switch of fixed capacity.The same with conventional switch mode capacitance structure, C1-Cn and k1-kn forms bang-bang control fixed capacity.With conventional switch mode electric capacity difference, introduce the AMOS variable capacitance of accumulation type in switching regulator variable capacitance of the present invention, control switch ka and kb is logical complement MOS switch, and when switch ka disconnects, switch kb conducting, the voltage at AMOS electric capacity two ends is V _b2-V _b1; When switch ka conducting, when switch kb disconnects, the voltage at AMOS electric capacity two ends is V _b2-V _ctrl, therefore, AMOS electric capacity can be made by the conducting of control switch ka and kb to be operated in different states from disconnection.In addition, C is fixed capacity, and with AMOS capacitances in series, resistance R is biasing resistor, for AMOS electric capacity provides bias voltage.As shown in Figure 2 a, it is equivalent to one by switch k1, k2 to the symbol of equivalent tank capacitor ..., kn, ka, kb and control voltage V _ctrlcontrolled variable capacitor E-Varactor, VP and VN is the difference output end of equivalent variable electric capacity.

The capacitance variations of variable capacitor is limited in scope, and adopts the equivalent tank capacitor of the combining structure of switching regulator variable capacitor and switching regulator fixed capacitor to expand the excursion of resonant tank electric capacity further.Control switch k1, k2 ... kn and fixed capacity C1, C2 ..., Cn realizes the coarse adjustment to equivalent resonant capacitor electric capacity, and control switch ka, kb and bias voltage V _b1, V _b2with control voltage V _ctrlrealize the fine tuning to equivalent resonant capacitor electric capacity.In equivalent tank capacitor, AMOS capacitor has two kinds of different mode of operations:

The mode of operation of switch ka and kb control AMOS electric capacity, and the control signal logical complement of ka and kb, i.e. any time, ka and kb has and only has a switch to be conducting state.When switch ka disconnects, during kb conducting, V _b2-V _b1make AMOS electric capacity work in electric capacity not with the interval of change in voltage, AMOS electric capacity is equivalent to fixed capacitor, when C is much larger than AMOS electric capacity C _vartime, the equivalent capacity of E-Varactor is:

${2C}_{\mathrm{eq}}=\underset{k=1}{\overset{n}{\mathrm{\Σ}}}\left(S_k{C}_k\right)+C_{\mathrm{fix}}---\left(1\right)$

S in formula _kfor the state of a kth switch, be 1 when the switch is closed, otherwise be 0; C _kfor the constant capacitance that a kth switch controls, C _fixfor minimum total equivalent capacitance value, be the minimum value sum of AMOS electric capacity, AMOS capacitance C _varfor fixed numbers.Now, because all electric capacity is all not with the fixed value of electric capacity both end voltage change, therefore C _eqalso be constant capacitance.

When switch ka conducting, when kb disconnects, AMOS electric capacity is operated in transfiguration district, due to now, and one end of AMOS electric capacity and the control voltage V of VCO _ctrlend be connected, AMOS electric capacity as the variable capacitance of in resonant tank, when C is much larger than C _vartime, the total equivalent capacity of E-Varactor is:

${2C}_{\mathrm{eq}}\left(V_{\mathrm{ctrl}}\right)=\underset{k=1}{\overset{n}{\mathrm{\Σ}}}\left(S_k{C}_k\right)+C_{\mathrm{var}}(V_{B1}-V_{\mathrm{ctrl}})---\left(2\right)$

C in formula _var(V _b1-V _ctrl) for AMOS electric capacity is with control voltage V _ctrlthe capacitance of change, as can be seen from the above equation, total the equivalent capacity of E-Varactor changes with the control voltage change of VCO.

The selection of AMOS electric capacity mode of operation primarily of switch k1, k2 ..., the operating state of kn determines, when all switches all conducting time, the total equivalent capacity of E-Varactor is maximum, when all switches all disconnect, and when not considering the parasitic capacitance of switch, the total equivalent capacity of E-Varactor is minimum.If m is the group number of fixed capacity, if n is master switch number.When selecting n≤m, AMOS electric capacity is operated in fixed capacity district; As n > m, AMOS electric capacity is operated in transfiguration district, and when partiting dc capacitor C capacitance C is much larger than AMOS capacitance Cvar, the total equivalent capacity of E-Varactor is expressed as following formula:

$\left\{\begin{array}{cc}{C}_{\mathrm{eq}}\left(v\right)=\frac{1}{2}(\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}\left(S_k{C}_k\right)+C_{\mathrm{fix}})& k<m\\ C_{\mathrm{eq}}\left(v\right)=\frac{1}{2}[\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}\left(S_k{C}_k\right)+C_{\mathrm{var}}(V_{B1}-V_{\mathrm{ctrl}})]& k\&GreaterEqual;m\end{array}\right.---\left(3\right)$

In formula: m is≤n.

Fig. 2 c is the structural representation of AMOS type variable capacitance in the modular structure of Fig. 2 b equivalent tank capacitor.This AMOS type variable capacitance is the NMOS tube being placed in N trap, and two ports of this AMOS electric capacity are respectively grid and substrate.N-well is N trap, and Bulk is substrate, and two NMOS tube N+ in parallel are placed in N trap, and Gate is that control end connects grid.As shown in Figure 2 d, Gate is grid to the schematic diagram of AMOS type variable capacitance, and Bulk is substrate.

2nd embodiment

The embodiment of the present invention based on the electrical schematic diagram of the wide frequency tuning range LC-VCO of equivalent tank capacitor, as shown in 3a.NMOS tube 308,309 and PMOS 303,302 cross-couplings produce active negative resistance.The active negative resistance that NMOS tube and PMOS produce is respectively-Gmn and-Gmp, and when active negative resistance is greater than the resistance loss of resonant tank, VCO meets oscillating condition.Variable capacitance main in circuit is 305 and 306, and both capacitances are identical, is all Cv.The electric capacity of variable capacitance changes with control voltage Vctrl.Inductance 304 adopts top-level metallic in CMOS technology to realize, and its structure is spiral inductance, and shape is quadrangle.In circuit, 307 is equivalent tank capacitor, and it has two fixed bias voltage V _b3with V _b4, a control voltage V _ctrl, these three voltages provide bias voltage for AMOS electric capacity in equivalent tank capacitor.K1 and k2 is the switch controlling signal of fixed capacity in equivalent tank capacitor, ka and kb is the operational module control signal of AMOS electric capacity, realizes AMOS two ends and is biased different voltage, thus be operated in different operation intervals by ka and kb.

It is equivalent tank capacitor 307 that VCO low-power consumption shown in Fig. 3 a realizes the tuning critical component of wide frequency ranges, shown in its concrete schematic diagram 3b.The fixed capacity 310,311 and 314,315 of two groups of switch control rule is adopted in equivalent tank capacitor, the switch of its correspondence is switching tube 312,313 and 316,317, the grid connection control voltage K1 of switching tube 312 and 313, the grid connection control voltage K2 of switching tube 316 and 317.Fixed capacity adopts mim type electric capacity or MOM type electric capacity in CMOS technology, and these electric capacity have high-quality-factor, and electric capacity does not change with the change in voltage at two ends.Switch adopts NMOS tube in CMOS technology to realize, and NMOS tube has little conducting resistance, less on the quality factor impact of fixed capacity.Adjustment switch 312,313 and 316,317, can realize the capacitance coarse adjustment of equivalent tank capacitor.In equivalence tuning capacitor, AMOS variable capacitance Cvar is 319 and 320.AMOS variable capacitance 319,320 respectively with fixed capacity 318,321 series connection, the capacitance of fixed capacity 318 and 321 is C, is partiting dc capacitor, and therefore the value of C is much larger than AMOS electric capacity Cvar.The operation interval of switching signal ka, kb control AMOS electric capacity, when switching signal ka logic level is 0, MOS switch 325 ends, and kb logic level is 1, receives the grid of MOS switching tube NM32, MOS switching tube 328 conducting, bias voltage V _b4through biasing resistor 327 and 322, AMOS electric capacity 319 and 320 tie point produce fixed bias voltage, the other end of AMOS electric capacity 319 and 320 respectively through biasing resistor 322 and 324, with bias voltage V _b3be connected, now, AMOS electric capacity works in fixed capacity interval, and AMOS electric capacity is equivalent to fixed capacity.When ka is logic level 1, MOS switching tube 325NM31 conducting, kb logic level is 0, and switching tube 328NM32 turns off, VCO control voltage V _ctrlthrough the source electrode of actuating switch pipe 325 and drain electrode and biasing resistor 326 and 322, with AMOS electric capacity 319 with 320 tie point be connected, produce fixed bias voltage.Bias voltage V _b3meet | V _b3-V _ctrl| be worth less, AMOS electric capacity is operated in variable capacitance district, and now, AMOS is tuning by VCO control voltage.AMOS electric capacity is equivalent to the varactor element of resonant circuit, and its effect is the same with 304,305.AMOS electric capacity 319 and 320 and fixed capacity 310,311, the value of 314,315 satisfies condition: Cvar < C1 < C2.Therefore when k1 and k2 is high level simultaneously, two pairs of fixed capacities all access resonant tank, and resonant tank equivalent capacity has maximum capacitor value, now VCO control voltage gain K _vCOhave minimum value, the operating frequency of VCO is minimum.When k1 and k2 is low electricity frequency, two pairs of fixed capacities 310 and 311,314 and 315 are all turned off, and resonant tank equivalent capacity has position of minimum capacitance, and now VCO control voltage gain has maximum, and VCO is operated in low-limit frequency.When VCO is operated in high-frequency, it is little that resonant tank fixes constant capacitance, therefore within the scope of certain control voltage, VCO frequency range is large, and when VCO is operated in low frequency, resonant tank constant capacitance is large, it is little that variable capacitance takies proportion, in same control voltage excursion, VCO frequency tuning range is little, realizes the parasitic capacitance due to switch, the frequency tuning range of VCO is narrower, therefore only have and increase fixed capacity group number, same increase parasitic capacitance and conducting resistance, add power consumption and the area of VCO.In the design, when the low frequency of VCO, be operated in variable capacitance district by AMOS electric capacity in equivalent tank capacitor, VCO control voltage when improve low frequency increases, and frequency range can with close during high-frequency.Therefore the fixed capacity of the switch control rule of minority can be adopted to realize very wide frequency range, and that is, when same frequency tuning range, the power consumption of VCO and area are less than traditional VCO circuit.

As external control signal K ₁, k ₂, k _aand k _bbe 0, when K switch 1, k2, ka and kb disconnect, equivalent tank condenser capacitance is minimum value, and corresponding VCO is operated in highest frequency wave band, when not considering the parasitic capacitance of resonant tank, the frequency range of its correspondence as shown in the formula:

$f_{\min }\left(v\right)=\frac{\sqrt{2}}{2\mathrm{\&pi;}\sqrt{L(C_{\mathrm{e\; var}}\left(v\right)+C_{\min })}}---\left(4\right)$

In formula: C _{e var}v () is the capacitance of variable capacitor 305 and 306, C _minfor the capacitance of AMOS electric capacity in equivalent tank capacitor, it is fixed value.V is VCO control voltage.

As external control signal K ₁, k ₂, k _aand k _bbe 1, K switch 1, k2, ka and kb all conducting time, the equivalent capacity of equivalent tank capacitor is minimum value, and corresponding VCO is operated in low-limit frequency wave band, and when not considering the parasitic capacitance of resonant tank, the frequency range of its correspondence is:

$f_{\max }\left(v\right)=\frac{\sqrt{2}}{2\mathrm{\&pi;}\sqrt{L(C_{\mathrm{e\; var}}\left(v\right)+C_{\mathrm{var}}\left(v\right)+C_1+C_2)}}---\left(5\right)$

C in above formula _varv () is AMOS capacitance in equivalent tank capacitor, with control voltage change, and C ₁be the capacitance of 310,311, C ₂be 314,315 capacitances.

Fig. 2 d is the component symbol figure of Fig. 2 c AMOS type variable capacitance.

3rd embodiment

Fig. 4 a embodiment of the present invention based on the electrical schematic diagram of the wide frequency tuning range LC-VCO of equivalent tank capacitor, as shown in fig. 4 a.Structure as Fig. 4 a is substantially identical with Fig. 3 a, and difference is in equivalent tank capacitor 407 circuit, and the switch controlling signal of fixed capacity is three right: k ₁, k ₂, k ₃; Adopt kab to be the operational module control signal of AMOS electric capacity in circuit 407, realize AMOS two ends by kab and be biased different voltage, thus be operated in different operation intervals.Shown and NMOS tube 408,409 produces active negative resistance with PMOS 403,402 cross-couplings.The active negative resistance that NMOS tube and PMOS produce is respectively-Gmn and-Gmp, and when active negative resistance is greater than the resistance loss of resonant tank, VCO meets oscillating condition.Variable capacitance main in circuit is 405 and 406, and both capacitances are identical, is all Cv.The electric capacity of variable capacitance is with control voltage V _ctrlchange.Inductance 404 adopts CMOS technology, and its structure is spiral inductance, and shape is octagon.Equivalent tank capacitor 407, it has two fixed bias voltage V _b3with V _b4, a control voltage V _ctrl, these three voltages provide bias voltage k for AMOS electric capacity in equivalent tank capacitor ₁, k ₂, k ₃with operational module control signal k _ab.

It is equivalent tank capacitor 407 that VCO low-power consumption shown in Fig. 4 a realizes the tuning critical component of wide frequency ranges, and its concrete schematic diagram is as shown in 4b.The fixed capacity 410 and 411 of two groups of switch control rule is adopted in equivalent tank capacitor, 414 and 415 and 418 and 419, the switch of its correspondence is switching tube 412 and 413,416 and 417 and 420 and 421, the grid connection control voltage K1 of switching tube 412 and 413, the grid connection control voltage K2 of switching tube 416 and 417.Fixed capacity adopts mim type electric capacity or MOM type electric capacity in CMOS technology, and these electric capacity have high-quality-factor, and electric capacity does not change with the change in voltage at two ends.Switch adopts NMOS tube in CMOS technology to realize, and NMOS tube has little conducting resistance, less on the quality factor impact of fixed capacity.Adjustment switch 412 and 413,416 and 417 and 420 and 421, can realize the capacitance coarse adjustment of equivalent tank capacitor.In equivalence tuning capacitor, AMOS variable capacitance Cvar is 423 and 424.AMOS variable capacitance 423 and 424, respectively with fixed capacity 422,425 series connection, the capacitance of fixed capacity 422 and 425 is C, is partiting dc capacitor, and therefore the value of C is much larger than AMOS electric capacity Cvar.The operation interval of switching signal kab control AMOS electric capacity, when switching signal kab logic level is 0, MOS switching tube 429 ends, kab output logic level after inverter 433 is anti-phase is 1, receive the grid of MOS switching tube NM42, MOS switching tube 432 conducting, bias voltage V _b4through biasing resistor 431 and 427, AMOS electric capacity 423 and 424 tie point produce fixed bias voltage, the other end of AMOS electric capacity 423 and 424 respectively through biasing resistor 426 and 428, with bias voltage V _b3be connected, now, AMOS electric capacity works in fixed capacity interval, and AMOS electric capacity is equivalent to fixed capacity.When kab is logic level 1, MOS switching tube 429 conducting, kab output logic level after inverter 433 is anti-phase is 0, and switching tube 432 turns off, VCO control voltage V _ctrlthrough the source electrode of actuating switch pipe 429 and drain electrode and biasing resistor 430 and 427, with AMOS electric capacity 423 with 424 tie point be connected, produce fixed bias voltage.Bias voltage V _b3meet | V _b3-V _ctrl| be worth less, AMOS electric capacity is operated in variable capacitance district, and now, AMOS is tuning by VCO control voltage.AMOS electric capacity is equivalent to the varactor element of resonant circuit, and its effect is the same with 405 and 406.The value of AMOS electric capacity 423 and 424 and fixed capacity 410 and 411,414 and 415 and 418 and 419 satisfies condition: Cvar < C1 < C2 < C3.Therefore work as k1, when k2 and k3 is high level simultaneously, three pairs of fixed capacities 410 and 411,414 and 415 and 418 and 419 all access resonant tank, and resonant tank equivalent capacity has maximum capacitor value, now VCO control voltage gain K _vCOhave minimum value, the operating frequency of VCO is minimum.When k1, k2, k3 and kab are low electricity frequency, three pairs of fixed capacities 410 and 411,414 and 415 and 418 and 419 are all turned off, and resonant tank equivalent capacity has position of minimum capacitance, now VCO control voltage gain has maximum, and VCO is operated in low-limit frequency.When VCO is operated in high-frequency, it is little that resonant tank fixes constant capacitance, therefore within the scope of certain control voltage, VCO frequency range is large, and when VCO is operated in low frequency, resonant tank constant capacitance is large, it is little that variable capacitance takies proportion, in same control voltage excursion, VCO frequency tuning range is little, realizes the parasitic capacitance due to switch, the frequency tuning range of VCO is narrower, therefore only have and increase fixed capacity group number, same increase parasitic capacitance and conducting resistance, add power consumption and the area of VCO.In the design, when the low frequency of VCO, be operated in variable capacitance district by AMOS electric capacity in equivalent tank capacitor, VCO control voltage when improve low frequency increases, and frequency range can with close during high-frequency.Therefore the fixed capacity of the switch control rule of minority can be adopted to realize very wide frequency range, and that is, when same frequency tuning range, the power consumption of VCO and area are less than traditional VCO circuit.As external control signal k ₁, k ₂, k ₃and k _abbe 0, when K switch 1, k2, k3 and kab disconnect, equivalent tank condenser capacitance is minimum value, and corresponding VCO is operated in highest frequency wave band, and when not considering the parasitic capacitance of resonant tank, the frequency range of its correspondence is as formula (4).

As external control signal K ₁, k ₂, k ₃and k _abbe 1, K switch 1, k2, k3 and kab all conducting time, the equivalent capacity of equivalent tank capacitor is minimum value, and corresponding VCO is operated in low-limit frequency wave band, and when not considering the parasitic capacitance of resonant tank, the frequency range of its correspondence is formula (6):

$f_{\max }\left(v\right)=\frac{\sqrt{2}}{2\mathrm{\&pi;}\sqrt{L(C_{\mathrm{e\; var}}\left(v\right)+C_{\mathrm{var}}\left(v\right)+C_1+C_2+C_3)}}---\left(6\right)$

C in above formula _varv () is AMOS capacitance in equivalent tank capacitor, with control voltage change, and C ₁be the capacitance of 410 and 411, C ₂be 414 and 415 capacitances, C ₃be 418 and 419 capacitances.

Embodiments of the invention show through emulation, chip stream built-in testing, and under employing 0.18um CMOS technology condition, the chip area of whole LC-VCO is only 0.36mm ², power consumption is only 7.2mW, and frequency tuning range is 2.13GHz ~ 3.32GHz.Above index is all better than existing background technology.

The above; be only the detailed description realizing the specific embodiment of the invention of specification description of the present invention and graphic; unrestricted for illustration; but feature of the present invention is not limited thereto; those skilled in the art obviously understand; all scopes of the present invention should be as the criterion with the protection range of its claim; under the prerequisite not deviating from invention spirit that appended claims defines and invention scope; the change similar with it of all spirit according to the present invention and other embodiment implemented, all should be included among protection category of the present invention.

Claims (6)

1. a wide frequency tuning range LC-VCO, comprises negative resistance amplifier, inductor, variable capacitor, and equivalent tank capacitor, it is characterized in that, it is the LC-VCO circuit module formed based on equivalent tank capacitor;

The composition of described equivalent tank capacitor E-Varactor comprises: bias voltage by the AMOS variable capacitor of switch control rule to C _var(21) the fixed capacitor group C of and one switch control rule _g(22); Wherein

The fixed capacitor group (22) of described switch control rule comprises n to fixed capacitor C1 ~ Cn and n to control switch K1 ~ Kn, and control signal k1 ~ kn that n outside; The span of n is 2 ~ 5; The n control signal outside to control switch and n is control connection one to one, often pair of fixed capacitor is for being connected in series, one end of often pair of fixed capacitor connects output VP by a control switch, and the other end all passes through a control switch and connects output VN; By the on-off of the control signal control switch of outside, control the right access of fixed capacitor or disconnection, for adjusting the fixed capacitor group C of switch control rule _gcapacitance, realize the coarse adjustment of equivalent tank condenser capacity, the parasitic capacitance of introducing can be reduced again;

Described bias voltage comprises 2 AMOS capacitor C by the AMOS variable capacitor of switch control rule to (21) _var, control switch ka and kb that 2 partiting dc capacitor C, 3 biasing resistor R and control signal Ka and Kb control; 2 AMOS capacitor C _varbe connected in series, series connection contact connects biasing resistor R, the series connection contact of other end connection control switch ka and kb of biasing resistor R, and the other end of control switch ka connects access External Control Voltage V _ctrlvC end, the other end of control switch kb connects the outside fixed bias voltage V of access _b1vB1 end; The other end of two AMOS capacitors is respectively connected in series a partiting dc capacitor C, and two series connection contacts respectively connect a biasing resistor R, and the other end of two biasing resistors is connected in parallel, and interface connects the outside fixed bias voltage V of access _b2vB2 end; Capacitance for AMOS electric capacity holds control voltage V with VC _ctrlchange and change, realizing the fine tuning of equivalent tank condenser capacity, obtain wide frequency tuning range.

2. wide frequency tuning range LC-VCO according to claim 1, it is characterized in that, described LC-VCO circuit module is difference channel structure, two-pass DINSAR output VP and VN of circuit module is inductance two ends in electricity or electric capacity two ends, the amplitude output signal of two-pass DINSAR output is equal, and phase place is contrary.

3. wide frequency tuning range LC-VCO according to claim 1, is characterized in that, the inductor that described LC-VCO circuit module comprises is the fixed inductor of the on-chip spiral inductor adopting high-quality-factor, and its inductance value is L.

4. wide frequency tuning range LC-VCO according to claim 1, is characterized in that, the RF variable capacitor C based on CMOS technology that the variable capacitor (13) that described VCO circuit module comprises connects for pair of series _v, two variable capacitors are connected in series end connection control voltage V _ctrl, its capacitance is with control voltage V _ctrlchange and change, capacitance presents monotone variation with the change of control voltage.

5. wide frequency tuning range LC-VCO according to claim 4, is characterized in that, described control voltage V _ctrlfor the frequency tuning voltage of VCO, the VC end of access VCO circuit module, control voltage V _ctrlbe used for arranging the frequency of VCO, the frequency of VCO is consecutive variations with control voltage change, makes VCO be operated in required Frequency point.

6. according to the wide frequency tuning range LC-VCO one of claim 1-5 Suo Shu, it is characterized in that, the n in the fixed capacity group of described switch control rule adopts connecting electricity in n to switch to fixed capacity, and the span of n is 2 ~ 5; N preferred value depends on the loss of the gain of frequency tuning range, control voltage, chip area, AMOS electric capacity.