A kind of Low-power-consumptiohigh-gain high-gain broadband frequency mixer
Technical field
The present invention relates to the frequency mixer in millimetre-wave circuit, especially a kind of Low-power-consumptiohigh-gain high-gain broadband frequency mixer, adopt MOS technique, in millimetre-wave circuit, there is greater advantage, project organization is simple, frequency mixer can be made simultaneously to obtain high-gain and broadband character, when having the gain identical with conventional mixer and bandwidth performance, greatly can reduce the power consumption of frequency mixer.
Background technology
Nineteen sixty-eight BarrieGilbert proposes gilbert's two balance multiplier architecture first, and be widely used in (hereinafter referred to as " gilbert mixer ") in frequency mixer, its circuit block diagram and circuit theory are respectively as shown in Figure 1 and Figure 2, single-ended signal is converted to differential signal RF+ and RF-by Ba Lun by radiofrequency signal RF, connect the grid of transconductance cell common source configuration metal-oxide-semiconductor M1 and M2 respectively, input radio frequency voltage signal is converted to current radio frequency signal by metal-oxide-semiconductor M1, M2.Single-ended signal is converted to differential signal LO+ and LO-by Ba Lun by local oscillation signal LO, respectively the grid of connecting valve unit metal-oxide-semiconductor.Switch element is made up of metal-oxide-semiconductor M3, M4, M5, M6, and the drain electrode of switch element metal-oxide-semiconductor exports middle frequency difference sub-signal, and wherein the drain electrode of metal-oxide-semiconductor M3, M5 exports positive intermediate-freuqncy signal IF+, and the drain electrode of metal-oxide-semiconductor M4, M6 exports anti-phase intermediate-freuqncy signal IF-.Due to self structure, there is following shortcoming in gilbert mixer:
Be that gain is low on the one hand, the voltage in load is determined by the product of intermediate frequency output current and load resistance, when electric current of intermediate frequency is constant, improves load voltage and must improve load resistance.If use resistive load, then the use of large resistance must consume too much voltage, and the voltage remaining of circuit is reduced, and is difficult to obtain high-gain in higher IF-FRE due to the resistive load that affects of parasitic capacitance.If use tuned load, load resistance depends on the quality factor q of inductance, and the Q of general on-chip inductor is very low, makes the gain of frequency mixer very low.
Narrow bandwidth on the other hand, if use resistive load, low-pass characteristic is become by effect of parasitic capacitance gain, extremely low to higher IF-FRE gain, therefore tuned load must be used, and the 3dB tuning bandwidth of typical LC resonant network and the ratio of resonance frequency are 10% ~ 15%, that is the intermediate-frequency bandwidth of frequency mixer is generally 10% ~ 15% with the ratio of IF-FRE, this is obviously inadequate for the application that channel width is larger relative to IF-FRE, such as in a 60GHz millimeter-wave systems, IF-FRE is 12GHz, support the intermediate-frequency bandwidth of 2.5GHz, bandwidth reaches 20.8% with the ratio of carrier frequency.
It is worthy of note, sometimes can exchange bandwidth for gain, such as connect with inductance with a resistance wittingly, can reduce the Q of inductance thus bandwidth becomes large, gain simultaneously diminishes; Sometimes also can exchange gain for by dedicated bandwidth, such as use positive feedback unit, make total resistance become large by introducing negative resistance in parallel in load, such gain uprises same Time Bandwidth and narrows.But these methods are all that it is some for cost is to exchange another lifting for sacrifice in gain and bandwidth, cannot optimize this two indices simultaneously.
Pass through above-mentioned traditional gilbert mixer analysis, can draw to draw a conclusion: the reason that 1. traditional gilbert mixer gain is lower is that the load conductance composition seen after electric current of intermediate frequency is flowed out by switch element is comparatively large, thus the voltage of intermediate frequency produced is less causes.When using tuned load, the Q value that inductance unit is limited and the limited output resistance of switching stage all govern the reduction of load conductance, and this is the major reason that traditional structure cannot improve gain; 2. the main cause that traditional gilbert mixer bandwidth is narrower be tuned load in the frequency of off-resonance point, susceptance composition increases too fast, thus the voltage that electric current produces in load declines fast with frequency departure resonance point and causes; 3. by improving the method for load inductance Q value, the gain of frequency mixer and bandwidth can not improve simultaneously, and gain and bandwidth are often conflicting, need compromise consideration.
Summary of the invention
The object of the invention is the deficiency for overcoming prior art, providing a kind of Low-power-consumptiohigh-gain high-gain broadband frequency mixer, the technical scheme of employing is:
A kind of Low-power-consumptiohigh-gain high-gain broadband frequency mixer, containing the basic structure of gilbert mixer, be provided with Ba Lun unit, transconductance cell, switch element and the load unit containing differential inductance and load end parasitic capacitance in parallel, wherein, Ba Lun unit comprises radio frequency Ba Lun and local oscillator Ba Lun, and radio frequency Ba Lun converts the radio frequency single-ended signal of input to differential voltage signal V
rF+ and V
rF-after export transconductance cell to, transconductance cell converts radio frequency voltage signal to current radio frequency signal RF+ and RF-and inputs to switch element; Local oscillator Ba Lun converts the local oscillator single-ended signal of input to differential voltage signal V
lO+ with V
lO-after also export switch element to, switch element is by radio-frequency differential current signal RF+ and RF-of input and the local oscillator differential voltage signal V of input
lO+ with V
lO-be multiplied after export intermediate frequency differential current signal IF+ and IF-and export middle frequency difference divided voltage signal V by the load unit containing differential inductance and load end parasitic capacitance in parallel
oUT+and V
oUT-the centre cap of differential inductance connects power supply Vdd, the intermediate frequency differential current signal IF+ of the two ends difference connecting valve unit output of differential inductance and IF-, it is characterized in that: after switch element, set up positive feedback unit, LCR resonant element and buffer cell, jointly form new load unit with the load unit containing differential inductance and parallel parasitic capacitance, export final middle frequency difference divided voltage signal V by buffer cell
iF+and V
iF-;
Said positive feedback unit is for reducing the conductance composition of new load unit, to improve the gain of frequency mixer, comprise NMOS tube M7, M8 and electric capacity C3, C4, the Source interconnect of NMOS tube M7 and NMOS tube M8 ground connection, the grid of NMOS tube M7 and NMOS tube M8 connects bias voltage V respectively
bias1the drain electrode of NMOS tube M7 connects one end of electric capacity C4 and the differential signal output forward end IF+ of switch element, the other end of electric capacity C4 connects the grid of NMOS tube M8, the drain electrode of NMOS tube M8 connects one end of electric capacity C3 and the differential signal output backward end IF-of switch element, and the other end of electric capacity C3 connects the grid of NMOS tube M7;
Said LCR resonant element is used for the equivalent opposite sign of susceptance composition by the susceptance composition of LCR resonant element and new load unit itself, offset the susceptance composition of new load unit, with the bandwidth of extended mixer, comprise inductance L 1, L2, resistance R1, R2 and electric capacity C1, C2, one end of resistance R1 connects the drain electrode of NMOS tube M7 and the link of electric capacity C4 in positive feedback unit, the other end series capacitance C1 of resistance R1, one end of inductance L 2 is connected after inductance L 1, the other end series capacitance C2 of inductance L 2, the drain electrode of NMOS tube M8 in positive feedback unit and the link of electric capacity C3 is connected after R2,
Said buffer cell comprises NMOS tube M9, M10, M11, M12, the drain interconnection of NMOS tube M11, M12 also connects power supply Vdd, the grid of NMOS tube M11 to connect in LCR resonant element the drain electrode of NMOS tube M8 and the link of electric capacity C3 in resistance R2 and positive feedback unit, the grid of NMOS tube M12 to connect in LCR resonant element the drain electrode of NMOS tube M7 and the link of electric capacity C4 in resistance R1 and positive feedback unit, the Source interconnect of NMOS tube M9, M10 ground connection, the grid of NMOS tube M9, M10 connects bias voltage V respectively
bias2, the drain electrode of NMOS tube M9 and the Source interconnect of M11 as final intermediate frequency differential signal outputs V
iF+, the drain electrode of NMOS tube M10 and the Source interconnect of M12 as final intermediate frequency differential signal outputs V
iF-.
Two PMOS M13 and M14 can be set up in said switch element, PMOS M13 is connected Vdd with the source electrode of M14, PMOS M13 is connected with the drain and gate of two metal-oxide-semiconductors in transconductance cell respectively with the drain and gate of M14, form current injection structures, to reduce the electric current flowing through switch element.
Said Ba Lun unit comprises on sheet or the type of sheet outer Ba Lun, Ba Lun comprises lamped element Ba Lun, transformer Balun, transmission line Ba Lun;
As long as said buffer cell has condensance input composition and low-resistance exports, such as, drain electrode can be adopted to connect the common-source stage structure of tuning coil;
It is used in combination that metal-oxide-semiconductor in said circuit can be replaced bipolar transistor or metal-oxide-semiconductor and bipolar transistor;
Load end parasitic capacitance in parallel with differential inductance in said load unit can adopt external capacitor.
Advantage of the present invention and remarkable result:
(1) in millimeter wave mixer design, how under low-power consumption, gain is improved and bandwidth is design challenges always.The raising of gain and bandwidth is mainly exchanged for by power consumption in prior art designs, and gain often contradicts with the improvement of bandwidth, needs compromise consideration.The present invention adopts positive feedback unit to reduce load conductance, uses additional series resonant circuit in parallel with load unit simultaneously, balances out the change of susceptance part with frequency, can improve gain simultaneously and extend bandwidth like this.Compare traditional structure, gain and bandwidth are obtained for and increase substantially, and see Fig. 5.
(2) using frequency mixer of the present invention, when obtaining the gain suitable with traditional structure and bandwidth performance, can greatly reducing the power consumption of frequency mixer.When such as power consumption is identical, the gain of this structure frequency mixer is four times of traditional structure, and bandwidth is the twice of traditional structure, then, when gain and bandwidth are all suitable with traditional structure, power consumption can be down to 1/8th of traditional structure.
Accompanying drawing explanation
Fig. 1 is the circuit block diagram of traditional gilbert mixer;
Fig. 2 is the circuit theory diagrams of traditional gilbert mixer;
Fig. 3 is the circuit block diagram of frequency mixer of the present invention;
Fig. 4 is the circuit theory diagrams of frequency mixer of the present invention;
The conversion gain curve that Fig. 5 is traditional gilbert mixer, load adds positive feedback unit and load adds positive feedback unit and LCR resonant element simultaneously compares;
Fig. 6 is the another kind of implementing circuit of Fig. 4 breaker in middle cell mesh.
Embodiment
Referring to Fig. 3, radiofrequency signal is converted to differential voltage signal V by radio frequency Ba Lun unit 1
rF+ and V
rF-send into transconductance cell 2, transconductance cell 2 is converted to the voltage signal of input current signal and sends into switch element 3, and local oscillation signal converts differential voltage signal V to by Ba Lun unit 4 simultaneously
lO+ with V
lO-after be also added on switch element 3, make it switch radio-frequency current with local frequency.Switch element 3 exports intermediate frequency differential current signal IF+ and is connected load unit 5 with IF-.Identical with circuitry block Fig. 1 of traditional gilbert's structure frequency mixer with upper part.The present invention adds positive feedback unit 6, LCR resonant element 7 and buffer cell 8 after switch element 3, they and load unit 5 form the intermediate frequency output loading of new load unit as switch element 3 jointly, on intermediate frequency differential signal line before buffer 8, in parallel positive feedback unit 6 and LCR resonant element 7, export final middle frequency difference divided voltage signal V by buffer cell 8
iF+and V
iF-.
Referring to Fig. 4, single ended input radiofrequency signal V
rFconnect the single-end port of radio frequency Ba Lun 1, the difference output of radio frequency Ba Lun 1 connects the grid (M1 and M2 forms transconductance cell 2) of M1 and M2 respectively, the source ground of M1 and M2, the drain electrode of M1 with M2 is connected with the source electrode of M3, M4 and M5, M6 respectively (M3, M4, M5, M6 form switch element); Single ended input local oscillation signal V
lOconnect the single-end port of local oscillator Ba Lun 2, the difference output of local oscillator Ba Lun 2 connects the grid of M3, M6 and M4, M5 respectively, the drain electrode of M3 and M5 connects and exports forward port middle frequency difference sub-signal, and the drain electrode of M4 and M6 connects and exports reverse port middle frequency difference sub-signal.After middle frequency difference sub-signal exports from switch element 3, with the differential inductance L in load unit
diffconnect, differential inductance L
diffcentre cap meet power vd D, with differential inductance L
diffparallel connection, the electric capacity summation added by the parasitic capacitance or have a mind to that the electric capacity that dotted line connects represents load end.Above partial circuit and traditional gilbert's structure frequency mixer indifference.The present invention adds positive feedback unit 6, LCR resonant element 7 and buffer cell 8 in the intermediate frequency output loading of above-mentioned switch element 3, differential inductance L
diffwith the total capacitance of composition load (comprising the input capacitance etc. of parasitic capacitance that switching tube drains, electric capacity that positive feedback unit is introduced and buffer cell) resonance in IF-FRE.
Positive feedback unit 6 is for reducing the conductance composition of new load unit, to improve the gain of frequency mixer, comprise NMOS tube M7, M8 and electric capacity C3, C4, the Source interconnect of NMOS tube M7 and NMOS tube M8 ground connection, the grid of NMOS tube M7 and NMOS tube M8 connects bias voltage V respectively
bias1the drain electrode of NMOS tube M7 connects one end of electric capacity C4 and the differential signal output forward end IF+ of switch element, the other end of electric capacity C4 connects the grid of NMOS tube M8, the drain electrode of NMOS tube M8 connects one end of electric capacity C3 and the differential signal output backward end IF-of switch element, and the other end of electric capacity C3 connects the grid of NMOS tube M7;
LCR resonant element 7 is for by equivalent for the susceptance composition of the susceptance composition of LCR resonant element and new load unit itself opposite sign, offset the susceptance composition of new load unit, with the bandwidth of extended mixer, comprise inductance L 1, L2, resistance R1, R2 and electric capacity C1, C2, one end of resistance R1 connects the drain electrode of NMOS tube M7 and the link (namely IF+ holds) of electric capacity C4 in positive feedback unit, the other end series capacitance C1 of resistance R1, one end of inductance L 2 is connected after inductance L 1, the other end series capacitance C2 of inductance L 2, the drain electrode of NMOS tube M8 in positive feedback unit and the link (namely IF-holds) of electric capacity C3 is connected after R2.Wherein, L1, C1 and R1 form series resonant network, and L2, C2 and R2 form series resonant network, and resonance frequency is IF-FRE.
Buffer cell 8 comprises NMOS tube M9, M10, M11, M12, the drain interconnection of NMOS tube M11, M12 also connects power supply Vdd, the grid of NMOS tube M11 to connect in LCR resonant element the drain electrode of NMOS tube M8 and the link of electric capacity C3 in resistance R2 and positive feedback unit, the grid of NMOS tube M12 to connect in LCR resonant element the drain electrode of NMOS tube M7 and the link of electric capacity C4 in resistance R1 and positive feedback unit, the Source interconnect of NMOS tube M9, M10 ground connection, the grid of NMOS tube M9, M10 connects bias voltage V respectively
bias2, the drain electrode of NMOS tube M9 and the Source interconnect of M11 as final intermediate frequency differential signal outputs V
iF+, the drain electrode of NMOS tube M10 and the Source interconnect of M12 as final intermediate frequency differential signal outputs V
iF-.
The Low-power-consumptiohigh-gain high-gain broadband frequency mixer that foregoing circuit of the present invention is formed compares traditional gilbert mixer, owing to adding: 1. positive feedback unit: adopt cross coupling structure to produce negative conductance, in parallel with the positive conductance of the load of switch element own, thus reduce load conductance, improve the voltage that electric current of intermediate frequency produces in load, thus improve gain.But also should see, when only adding positive feedback unit, reduce load conductance component, load susceptance component does not then change, therefore when frequency shift (FS) resonance frequency, susceptance becomes branch to divide to walk more electric current, and the bandwidth of frequency mixer is reduced further, and therefore positive feedback can only improve gain, and the overall performance of gain and bandwidth can not be improved, still exist compromise between gain and bandwidth.2. LCR resonant element: by a LCR network in parallel on intermediate frequency load, its resonance frequency is identical with intermediate frequency tuning network, and this network produces a susceptance component on the frequency of off-resonance frequency, the symbol of this susceptance component is contrary with the susceptance that intermediate frequency resonant load itself produces, counteract the change of susceptance with frequency shift (FS), make load all show as a pure conductance on a very wide frequency band, greatly extend the bandwidth of frequency mixer.Wherein the value of resistance, inductance, electric capacity to select suitable, choosing of resistance is moderate, the too small meeting of resistance value makes gain very low, cross conference and produce self-excitation, inductance and electric capacity will be tuned in IF-FRE, and the susceptance equal and opposite in direction that the susceptance composition size that they produce when off-resonance frequency will produce with laod network itself, thus offset completely.Be described as follows:
The resistance that when not having a LCR network in parallel, laod network has, inductance, electric capacity are respectively R
0, L
0and C
0, the resistance of LCR network in parallel, inductance, electric capacity are respectively R, L and C, through the admittance obtaining new laod network of deriving:
Wherein Δ ω leaves resonance point ω
0frequency shift (FS).As can be seen from the above equation, in order to make load show as pure conductance over a wide frequency band, the imaginary part of above formula should be 0 in very wide scope, and L and C also will meet resonance at ω
0, the value of L and C can be determined thus.Due to the effect of positive feedback, the R in above formula
0for negative value, if the value of R is too little, when Δ ω → 0, the real part of above formula will be very large, and therefore load conductance is very large and gain is very low, but if the value of R is too large, the absolute value of above formula Section 2 can be less than Section 1 (negative value), then whole conductance is negative, produce self-excitation, therefore the value of resistance R to select suitable.
The advantage simultaneously increasing positive feedback unit 6 and LCR resonant element 7 also has: 1. make gain and bandwidth improve simultaneously, compare traditional raising gain or the method for spread bandwidth, this programme controls conductance composition and the susceptance composition of load simultaneously, and gain and bandwidth are increased dramatically on original structure basis simultaneously; 2. the bias voltage Vbias1 by changing positive feedback adjusts gain.In use can adjust the gain of frequency mixer according to actual needs, when noise is the primary restraining factors of system, the gain of frequency mixer can be improved to suppress the noise of late-class circuit; When being linearly the primary restraining factors of system, the gain of frequency mixer suitably can be reduced with the pressure of the relieving system linearity.As can be seen from formula above, after the parameter of all elements is determined, also has R
0can change with the intensity of positive feedback, R
0this is as negative, the stronger R of positive feedback
0absolute value less, therefore load conductance is less and gain is higher, and the intensity of positive feedback can be adjusted by bias voltage Vbias1 easily, and Vbias1 is higher, and positive feedback is stronger, thus changes the effect that bias voltage Vbias1 can play adjustment gain.In use can adjust the gain of frequency mixer according to actual needs, when noise is the primary restraining factors of system, the gain of frequency mixer can be improved to suppress the noise of late-class circuit; When being linearly the primary restraining factors of system, the gain of frequency mixer suitably can be reduced with the pressure of the relieving system linearity.
Fig. 5 respectively to traditional gilbert's structure, only add positive feedback unit and add positive feedback unit and LCR resonant element simultaneously time mixer gain compare with the change of frequency.Can find out and compare traditional gilbert's structure, after adding positive feedback, its gain significantly increases, but also greatly declines with Time Bandwidth, but after adding positive feedback and LCR resonant network, gain and bandwidth significantly improve simultaneously simultaneously.
Fig. 6 is the embodiment adding PMOS M13 and M14 in the circuit of Fig. 4 circuit breaker in middle power supply 3 part.The source electrode of M13 and M14 meets power supply Vdd, and drain electrode is connected with the drain electrode of M1 and M2 respectively, and grid is connected with the grid of M1 and M2 respectively, forms current injection structures, to reduce the electric current flowing through switch element.
Some unit in the present invention can change and do other structures, does not affect use of the present invention.Its mini-bus human relations unit can be used on sheet or the outer Ba Lun of sheet realizes, and can be various types of barron device, as lamped element Ba Lun, transformer Balun, transmission line Ba Lun etc., also can be passive or active any form.The effect of buffer cell be to buffer before and after circuit isolate, after using positive feedback technique, the conductance very different before and after buffer, therefore buffer should have good isolation.Except the source class used in this programme is followed except structure, buffer also may be selected to be other structures such as common source, as long as have condensance input composition and low-resistance exports, such as draining connects the common-source stage structure of tuning coil.In circuit, metal-oxide-semiconductor used can be replaced bipolar transistor, also can metal-oxide-semiconductor and bipolar transistor used in combination, circuit realiration function is constant.