CN1790894A - Differential superimposed RF CMOS low noise amplifier - Google Patents

Abstract

The differential-superposition RF CMOS low-noise amplifier belongs technology field of IC design and signal processing. Wherein, based on traditional LNA, adding a NMOS worked on linear area to eliminate the higher transconductance factor in traditional common-source MOS and improve its linearity without effect to forward amplification factor and noise factor. this invention fits to wireless receive module of 1.9GHz PCS, improves spectral purity of wireless signal obviously, and reduces error rate of baseband signal.

Description

Differential superimposed RF CMOS low noise amplifier

Technical field

The present invention relates to a kind of differential superimposed RF CMOS low noise amplifier, belong to the technical field of integrated circuit (IC) design and signal processing.

Background technology

In recent years, along with the development of radio frequency integrated circuit technology is rapid, many wireless communications products have been used in the daily life: 900MHz gsm mobile telephone, 1.9GHz PCS PCS Personal Communications System and 2.4GHz Bluetooth communication product etc.Radio frequency low-noise amplifier (RF LowNoise Amplifier is called for short LNA) is the pith of wireless receiver module front end in these products.Its effect is that the small-signal that receives by antenna is amplified, so that the subsequent module of receiver is handled.Because LNA is a whole receiver except antenna, also be the module of handling wireless signal in the whole system at first simultaneously, its performance is for whole receiver, even whole system has very important influence.Therefore, every index of raising LNA is very necessary.

The major parameter of describing the LNA performance has: positive magnification S ₂₁, input matching degree S ₁₁, output matching degree S ₂₂, reverse isolation degree S ₁₂, power consumption, input linearity IP ₃With noise factor NF.Because interrelated, the mutual restriction of these parameters, therefore the overall performance that adopts which kind of compromise proposal to improve LNA has become the main difficult point of design.According to the investigation to domestic and international research, the cascodes LNA shown in the accompanying drawing 1 is a kind of LNA circuit structure that is widely adopted.The sort circuit structure can be traded off between positive magnification and noise factor.But under the situation that power consumption is determined, the sort circuit structure is traded off between the positive magnification and the linearity and is existed certain deficiency, and bigger positive magnification can cause the linearity of amplifier to descend.The small-signal that receives in order to ensure antenna can obtain enough amplifications, and bigger positive magnification is absolutely necessary.But this can cause the decline of the linearity, and the result causes the output signal of LNA to produce harmonic distortion, causes the phase mutual interference of received signal spectrum component, thereby has influence on the normal reception of wireless signal.In order to guarantee that received signal can be by encoding and decoding correctly, the wireless communication protocol that IEEE formulates has clear and definite requirement as 802.11a/b/g to the linearity of LNA.

In sum, designing a kind of existing big positive magnification has the LNA of the big linearity to be significant again.

Summary of the invention

The technical problem to be solved in the present invention is to release a kind of differential superimposed RF CMOS low noise amplifier (Derivative Superposition-LNA is called for short DS-LNA).Not only have the advantage of traditional cascodes based on the LNA of this kind structure, and when obtaining bigger positive magnification, have the bigger linearity, remedied the weak point of traditional cascade LNA.

For solving above-mentioned technical problem, the present invention adopts following technical scheme.Described differential superimposed RF CMOS low noise amplifier is on the basis of traditional cascade LNA, increase a NMOS pipe that is operated in linear zone, be intended to offset the high-order mutual conductance coefficient of common source metal-oxide-semiconductor in the traditional structure, thereby under the not affected situation of index of the positive magnification of LNA and noise factor, the linearity of LNA is improved.

Now specifically describe technical scheme of the present invention in conjunction with the accompanying drawings.

A kind of differential superimposed RF CMOS low noise amplifier contains V _DdEnd, V _Bias1End, V _Bias2End, V _Bias3End, V _InEnd, V _OutEnd and ground wire, V _DdThe end and ground cross between voltage source+end and voltage source-end, V _Bias1End and V _Bias3End is connected V with bias voltage 1 end, bias voltage 2 ends and bias voltage 3 ends respectively _InEnd and V _OutEnd is respectively the radio-frequency (RF) signal input end and the radiofrequency signal output of this amplifier, it is characterized in that this amplifier also contains the first metal-oxide-semiconductor M1, the second metal-oxide-semiconductor M2, the 3rd metal-oxide-semiconductor M3, the first inductance L g, the second inductance L s1, the 3rd inductance L s2, the 4th inductance L d, the 5th inductance L out, the first capacitor C c1, the second capacitor C c2, the 3rd capacitor C d, the 4th capacitor C c3, the 5th capacitor C c4 and resistance R d, the first metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, the 3rd metal-oxide-semiconductor M3 is a NMOS pipe, the first inductance L g be connected across that Vin holds after the first capacitor C c1 connects and the grid of the first metal-oxide-semiconductor M1 between, the second capacitor C c2 is connected across V _Bias3End and V _Bias1Between the end, the grid of the grid of the first metal-oxide-semiconductor M1, the second metal-oxide-semiconductor M2 and the grid of the 3rd metal-oxide-semiconductor M3 respectively with V _Bias1End, V _Bias2End and V _Bias3End connects, the second capacitor C c2 is connected across between the grid of the grid of the first metal-oxide-semiconductor M1 and the 3rd metal-oxide-semiconductor M3, the second inductance L s1 is connected across between the source electrode of the source electrode of the first metal-oxide-semiconductor M1 and the 3rd metal-oxide-semiconductor M3, the 3rd inductance L s2 is connected across between the source electrode and ground wire of the 3rd metal-oxide-semiconductor M3, the drain electrode of the first metal-oxide-semiconductor M1, the source electrode of the second metal-oxide-semiconductor M2 is connected with the drain electrode of the 3rd metal-oxide-semiconductor M3, the 4th inductance L d, be connected across behind the 3rd capacitor C d and the resistance R d And connection between the drain electrode and Vdd end of the second metal-oxide-semiconductor M2, the 4th capacitor C c3 is connected across between the end of the drain electrode of the second metal-oxide-semiconductor M2 and the 5th inductance L out, the 5th capacitor C c4 is connected across between the 5th inductance L out and the 4th capacitor C c3 tie point and the ground wire, the other end of the 5th inductance L out and V _OutEnd connects.

In Fig. 2, under certain bias condition, after adding a small-signal between grid-source electrode of the first metal-oxide-semiconductor M1, its output drain current can be expressed as follows:

$i_d\left(v_{\mathrm{gs}}\right)=g_1{v}_{\mathrm{gs}}+g_2{v}_{\mathrm{gs}}^2+g_3{v}_{\mathrm{gs}}^3+......\left(1\right)$

Wherein g1 is exactly the small-signal transconductance coefficient of the first metal-oxide-semiconductor M1, and g2, g3... are the high-order mutual conductances of the first metal-oxide-semiconductor M1, and promptly drain current is to the higher differentiation of input voltage signal, and they are to cause transistor to produce nonlinear main cause.According to the definition of the LNA linearity (IP3), can adopt following formula to represent:

$A_{\mathrm{IP}3}=\sqrt{\frac{4}{3}\left|\frac{g_1}{g_3}\right|}...\left(2\right)$

Obviously, in order to improve the linearity of LNA, must increase transistorized small-signal transconductance g1, or reduce transistorized three rank mutual conductance coefficient g3, but adopt the former must cause increasing the power consumption of circuit, this method is also inadvisable.Therefore, the present invention has adopted the latter.

Shown in Figure 3 is in (1) formula three mutual conductance coefficient g1, g2 and g3.As can be seen, g3 is under low bias level, and promptly the value in linear work district is for just, and under high bias condition, promptly the value in operate in saturation district is for negative.Therefore, can adopt two transistorized ways to reach the purpose that reduces g3, promptly allow a transistor be operated in the saturation region, allow another transistor be operated in linear zone, thereby reach the purpose that two three rank mutual conductance coefficients are cancelled out each other, promptly, reduce their algebraical sum by of the stack of two drain currents to three rank differential of input voltage signal.In view of the noise factor that reduces LNA, guarantee the positive magnification of LNA, the first metal-oxide-semiconductor M1 should be operated in the saturation region.Therefore, should add in circuit shown in Figure 1 that another one is operated in the metal-oxide-semiconductor of linear zone, i.e. the 3rd metal-oxide-semiconductor M3 among Fig. 2.

The present invention can realize amplifying under low noise environment radio frequency signal by simple circuit configuration, the invention has the advantages that: existing with quiescent bias current relatively be 4.6mA, the differential superimposed RF CMOS low noise amplifier that adopts 0.25 μ m CMOS technology manufacturing with the performance specification of traditional cascade electrode structure RF CMOS low noise amplifier with identical quiescent bias current, identical manufacturing process it.

As can be seen from the above table, under identical bias condition, identical power consumption, although sacrificed the power gain of the noise that is about 0.2dB and about 3.5dB, the linearity of low noise amplifier of the present invention has increased about 6dBm.15.2dB gain be enough to faint radio frequency signal is amplified, make that subsequent module can be to its correct processing in the system, but the linearity of+1.8dBm can further reduce the harmonic distortion of amplifying signal, make the purity of its signal spectrum become higher, the error rate of baseband signal just becomes lower like this.

Description of drawings

Fig. 1 is the circuit diagram of traditional cascade RF CMOS low noise amplifier.

Fig. 2 is the circuit diagram of differential superimposed RF CMOS low noise amplifier of the present invention.

Fig. 3 is the mutual conductance coefficient curve of the metal-oxide-semiconductor under the different bias conditions.

Embodiment

Now describe technical scheme of the present invention in conjunction with the accompanying drawings and embodiments in detail.

Embodiment

Present embodiment has and the identical circuit structure of circuit shown in Figure 2.The components and parts of present embodiment and circuit parameter are enumerated as follows:

The first inductance L g, the inductance value of the second inductance L s1 and the 3rd inductance L s2 is respectively 9.15nH, 0.6nH and 0.8nH;

The capacitance of the first capacitor C c1 and the second capacitor C c2 is respectively 50pF and 50pF.The inductance value of the 4th inductance L d and the 5th inductance L out is respectively 14.5nH and 10.3nH;

The 3rd capacitor C d, the capacitance of the 4th capacitor C c3 and the 5th capacitor C c4 is respectively 200fF, 50pF and 572fF;

The resistance of resistance R d is 300 ohm;

The voltage of bias voltage 1 end is 690mV;

The voltage of bias voltage 2 ends is 1.3V;

The voltage of bias voltage 3 ends is 530mV.

Describe the operation principle of technical solution of the present invention below in detail.Differential superimposed RF CMOS low noise amplifier circuit diagram of the present invention as shown in Figure 2.Bias voltage 1 end is the first metal-oxide-semiconductor M1 grid voltage control end, and its voltage is 690mV, and bias voltage 2 ends are second metal-oxide-semiconductor M2 grid voltage control ends, and its voltage is 1.3V, and bias voltage 3 ends are the 3rd metal-oxide-semiconductor M3 grid voltage control ends, and its voltage is 530mV.The first inductance L g, the inductance value of the second inductance L s1 and the 3rd inductance L s2 is respectively 9.15nH, 0.6nH and 0.8nH.The capacitance of the first capacitor C c1 and the second capacitor C c2 is respectively 50pF and 50pF.The first inductance L g, the second inductance L s1, the 3rd inductance L s2, the first capacitor C c1 and the second capacitor C c2 form input matching network, reduce the input signal reflectance.The inductance value of the 4th inductance L d and the 5th inductance L out is respectively 14.5nH and 10.3nH.The 3rd capacitor C d, the capacitance of the 4th capacitor C c3 and the 5th capacitor C c4 is respectively 200fF, 50pF and 572fF.The resistance of resistance R d is 300 ohm.The 4th inductance L d, the 5th inductance L out, the 3rd capacitor C d, the 4th capacitor C c3, the 5th capacitor C c4 and resistance R d form output matching network, reduce the output signal reflectance.When radio frequency signal is imported from the Vin end as input signal, the first metal-oxide-semiconductor M1 converts the voltage signal that changes to the current signal of variation, the current signal that this current signal produces with the 3rd metal-oxide-semiconductor M3 flows through the second metal-oxide-semiconductor M2 as current follower, when this electric current passes through output network, produced the voltage signal that changes, and from the output of Vout end.The amplitude of output voltage signal is bigger than the amplitude of input voltage signal, and input signal has been exaggerated.

Because the three rank mutual conductance coefficients that the 3rd metal-oxide-semiconductor M3 produces have negative function to the three rank mutual conductance coefficients that the first metal-oxide-semiconductor M1 produces, so three rank mutual conductance coefficients of whole amplifier have diminished, and promptly the linearity of amplifier has improved.Simultaneously, because the multiplication factor of amplifier depends primarily on the first metal-oxide-semiconductor M1, and do not have influence on the parameter of the first metal-oxide-semiconductor M1 in the process of the three rank mutual conductance coefficients that reduce whole amplifier, so the positive magnification of whole amplifier still can keep bigger numerical value.

Claims (2)

1, a kind of differential superimposed RF CMOS low noise amplifier contains V _DdEnd, V _Bias1End, V _Bias2End, V _Bias3End, V _InEnd, V _OutEnd and ground wire, V _DdThe end and ground cross between voltage source+end and voltage source one end, V _Bias1End and V _Bias3End is connected V with bias voltage 1 end, bias voltage 2 ends and bias voltage 3 ends respectively _InEnd and V _OutEnd is respectively the radio-frequency (RF) signal input end and the radiofrequency signal output of this amplifier, it is characterized in that, this amplifier also contains first metal-oxide-semiconductor (M1), second metal-oxide-semiconductor (M2), the 3rd metal-oxide-semiconductor (M3), first inductance (Lg), second inductance (Ls1), the 3rd inductance (Ls2), the 4th inductance (Ld), the 5th inductance (Lout), first electric capacity (Cc1), second electric capacity (Cc2), the 3rd electric capacity (Cd), the 4th electric capacity (Cc3), the 5th electric capacity (Cc4) and resistance (Rd), first metal-oxide-semiconductor (M1), second metal-oxide-semiconductor (M2), the 3rd metal-oxide-semiconductor (M3) all is a NMOS pipe, first inductance (Lg) be connected across that Vin holds after first electric capacity (Cc1) is connected and the grid of first metal-oxide-semiconductor (M1) between, second electric capacity (Cc2) is connected across V _Bias3End and V _Bias1Between the end, the grid of the grid of first metal-oxide-semiconductor (M1), second metal-oxide-semiconductor (M2) and the grid of the 3rd metal-oxide-semiconductor (M3) respectively with V _Bias1End, V _Bias2End and V _Bias3End connects, second electric capacity (Cc2) is connected across between the grid of the grid of first metal-oxide-semiconductor (M1) and the 3rd metal-oxide-semiconductor (M3), second inductance (Ls1) is connected across between the source electrode of the source electrode of first metal-oxide-semiconductor (M1) and the 3rd metal-oxide-semiconductor (M3), the 3rd inductance (Ls2) is connected across between the source electrode and ground wire of the 3rd metal-oxide-semiconductor (M3), the source electrode of the drain electrode of first metal-oxide-semiconductor (M1), second metal-oxide-semiconductor (M2) is connected with the drain electrode of the 3rd metal-oxide-semiconductor (M3), and the 4th inductance (Ld), the 3rd electric capacity (Cd) and resistance (are connected across the drain electrode and the V of second metal-oxide-semiconductor (M2) behind the Rd) And connection _DdBetween the end, the 4th electric capacity (Cc3) is connected across between the end of the drain electrode of second metal-oxide-semiconductor (M2) and the 5th inductance (Lout), the 5th electric capacity (Cc4) is connected across between the 5th inductance (Lout) and the 4th electric capacity (Cc3) tie point and the ground wire, the other end and the V of the 5th inductance (Lout) _OutEnd connects.

2, differential superimposed RF CMOS low noise amplifier according to claim 1 is characterized in that, the components and parts of this amplifier and circuit parameter are enumerated as follows:

First inductance (Lg), the inductance value of second inductance (Ls1) and the 3rd inductance (Ls2) is respectively 9.15nH, 0.6nH and 0.8nH;

The capacitance of first electric capacity (Cc1) and second electric capacity (Cc2) is respectively 50pF and 50pF.The inductance value of the 4th inductance (Ld) and the 5th inductance (Lout) is respectively 14.5nH and 10.3nH;

The 3rd electric capacity (Cd), the capacitance of the 4th electric capacity (Cc3) and the 5th electric capacity (Cc4) is respectively 200fF, 50pF and 572fF;

The resistance of resistance (Rd) is 300 ohm;

The voltage of bias voltage 1 end is 690mV

The voltage of bias voltage 2 ends is 1.3V;

The voltage of bias voltage 3 ends is 530mV.

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