A kind of radio frequency ultra-wideband low-noise amplifier based on inductance compensation
Technical field
The invention belongs to radio frequency integrated circuit design field, be applied to the radio-frequency front-end of receiver, is a kind of ultra-wideband low-noise amplifier that is applicable to various wireless communication standard, is applicable in ultra wideband receiver system.
Background technology
Along with the development of electronics and information industry, circuit integration has become the direction of microelectronic industry talent joint research, and radio frequency chip is in the communications field, shared status can not be substituted.In radio frequency receiver, low noise amplifier is generally as the first order of receiver, and its operating frequency is often very high, need to consider wave reflection characteristic; Simultaneously low noise amplifier need to provide enough gains to overcome the noise that subsequent conditioning circuit brings, and the quality of noise characteristic has determined the sensitivity of receiver, illustrates that low noise amplifier must be able to process the very faint signal that approaches noise level; In addition low noise amplifier will need to process the signal of the very high level that approaches transmitting antenna simultaneously, ensure to receive large-signal and do not produce distortion, therefore the linearity is an important indicator of low noise amplifier, and the quality of the performance of a low noise amplifier plays vital effect to the performance of whole receiver.Owing to being connected with antenna, therefore the input signal source of low noise amplifier is usually expressed as a specific impedance, for example 50 Ω or 75 Ω.Low noise amplifier has determined its researching value in the role of receiver, the quality of wideband low noise amplifier performance is weighed jointly by many indexs such as bandwidth, noise factor, reflection coefficient, the linearity, gain, power consumptions.
Narrow-band low-noise amplifier can only be processed the radiofrequency signal of some frequency ranges, can not meet the demands in some field, for example software wireless electrical domain, if adopting multiple narrow-band low-noise amplifiers realizes, can take so very large chip area, also make circuit complicated, therefore wideband low noise amplifier becomes the focus of current radio frequency integrated circuit research.Wideband low noise amplifier can be processed the radiofrequency signal of multiple frequency ranges, thereby has saved cost.
Super-broadband tech, since proposing, has become the focus of research, and ultra broadband is defined as: the upper limiting frequency f of bandwidth
maxwith lower frequency limit f
mindifference divided by centre frequency f
0value K be greater than 125%, exceed 1.5GHz with Time Bandwidth, meet
f
max-f
min>1.5G (2)
And want to realize the receiver of various modes communication standard, and just need low noise amplifier can process the radiofrequency signal of multiple frequency ranges, ensure the linearity that there is lower noise factor and can receive in the time processing the signal of these frequency ranges simultaneously.
Traditional wideband low noise amplifier as shown in Figure 1, this circuit is active feedback structure wideband low noise amplifier, (following device nmos pass transistor represents with MN, device PMOS transistor represents with MP), device MN1, MN2 forming circuit cascade amplifying stage, RL is the load of amplifier, device R f, MN4 mates in order to realize input impedance for low noise amplifier provides active feedback, Vb1 provides biasing for MN3, can provide electric current for MN4 like this, MP1 plays the effect of shunting to reduce pressure drop above it for load resistance RL, but this structure is difficult to realize high-gain and very wide bandwidth simultaneously, reason is that shunting transistor MP1 will flow through larger electric current, need larger device size, make drain terminal arrive ground parasitic capacitance very large.For this reason, the invention provides a kind of new structure and realize ultra-wideband low-noise amplifier.
Summary of the invention
The object of the invention is in order to realize higher gain in radio frequency ultra wide band range, spy provides the ultra-wideband low-noise amplifier of a kind of 0.1-12GHz based on inductance compensation, to overcome the deficiencies in the prior art, learn that according to (1) formula K value of the present invention is about 1.967, far above other papers and the designed wideband low noise amplifier of patent, obtain the performances such as good broadband Input matching, noise factor, the linearity simultaneously, can be applicable in ultra-wideband communication system.
In order to realize enough large ultra-wideband low-noise amplifiers of bandwidth, the present invention has adopted new technical scheme, as shown in Figure 2: ultra-wideband low-noise amplifier of the present invention is mainly made up of jointly input amplifying stage, feedback stage, matching stage, load stage, bias stage and output buffer stage circuit:
Input amplifying stage is made up of jointly nmos pass transistor MN1, MN2 and PMOS transistor MP1, in order to realize the enlarging function to input signal;
Feedback stage is made up of jointly nmos pass transistor MN3, resistance R _ f and capacitance C1, C2, be connected between the output and input of input amplifying stage, be used for realizing feedback and obtain equivalent input impedance in circuit, thereby can make matching stage realize input impedance coupling;
Matching stage is made up of jointly the pad parasitic capacitance CP with esd protection, sheet internal inductance L1, feedback device MN3, Rf, C1, C2, can realize like this input impedance coupling, thereby obtain good input reflection coefficient (it is generally acknowledged that be less than-10dBm of reflection coefficient is acceptable value);
Load stage is made up of resistance R L, sheet internal inductance L2, capacitor C L, thereby the effect that provides load to realize normal amplifying signal for low noise amplifier is provided for RL, L2, the electric capacity that CL introduces for simulation low noise amplifier next stage (frequency mixer);
Bias stage is by current source I1, I2, nmos pass transistor MN4, MN5, MN6, MN7, PMOS transistor MP2, resistance R 1, R2, R3 form jointly, low noise amplifier individual channel plays the effect that bias current is provided for low noise amplifier, can normally be worked;
Output buffer stage is made up of nmos pass transistor MN8, resistance R 4, output DC potential can be adjusted to suitable value, also can carry out impedance matching to output port, is convenient to the independent test after low noise amplifier flow.
Input amplifying stage and load stage realize amplifies input signal Vin, input amplifying stage output connects feedback stage, load stage and output buffer stage, drain terminal through MN2 after input amplifying stage amplifies signal is exported, feed back to the input of input amplifying stage by feedback stage, the drain terminal output signal of MN2 flows into output buffer stage simultaneously, the output signal Vout of output low noise amplifier, bias stage is connected with input amplifying stage, feedback stage, provides suitable bias current for inputting amplifying stage and feedback stage.
In the present invention, VDD, GND are respectively low noise amplifier provides the DC potential of power supply 1.2V and 0V, in the rational situation of bias stage circuit design, can realize good Input matching effect by CP, L1, MN3, Rf, C1, C2, therefore input signal Vin can enter amplification grade circuit, and amplify through MN1, MP1, MN2, from the drain terminal output of MN2, entering after the grid buffering of MN8 is Vout from the source output of MN8, and the ratio of output signal Vout and input signal Vin is the gain of low noise amplifier.
Ultra-wideband low-noise amplifier proposed by the invention compared with the traditional low noise amplifier shown in Fig. 1 improved place and advantage as follows:
1. as traditional wideband low noise amplifier, do not shunt MOS transistor one of load resistance two ends parallel connection, the shunting MOS transistor drain terminal that can eliminate like this in conventional art arrives the electric capacity on ground, thereby has improved to a certain extent bandwidth;
2. adopted current multiplexing technology at input amplifying stage, the electric current that flows through MP1 flows through MN1 simultaneously, so not only can increase the mutual conductance of amplifying stage, improve the gain of low noise amplifier, simultaneously MP1 divides to obtain the part electric current of MN1, alleviate the pressure drop above load resistance RL, can obtain more reasonably exporting DC potential, made can normally work under low supply voltage;
3. different from the current multiplexing technology in other papers or in patent, current multiplexing technology of the present invention has adopted two independently biasings, be that MN1, MP1 have relatively independent biasing due to capacitor C 1, C2 every straight effect, such benefit is that the electric current of MN1 and MP1 can be relatively independent, and be not subject to the impact of process deviation, flow through MN1, MP1 electric current determine after, pressure drop substantially constant above load resistance RL so, like this can be for feedback device MN3 provides metastable DC potential, thus make the more stable work of feedback control loop;
4. before inductance L 1 is added in the input amplifying stage of low noise amplifier, not only do certain contribution for coupling, can compensate the electric capacity of input simultaneously, reached the object of the bandwidth that increases low noise amplifier;
5. inductance L 2 is added in the load stage of low noise amplifier, can compensate the output limit of low noise amplifier, makes to export limit and moves to the direction away from initial point, reaches the object of the bandwidth that increases low noise amplifier, has also strengthened the flatness of gain;
6. output buffer stage is used for output signal to cushion, and output DC potential can be adjusted to suitable value, also can mate output port, is convenient to the independent test after low noise amplifier flow.
Ultra-wideband low-noise amplifier of the present invention has enough large bandwidth: in 0.1-12GHz broadband range, all can realize good Input matching, the indexs such as while noise, the linearity, gain, power consumption all meet the standard (specific performance will provide in execution mode) of typical ultra-wideband low-noise amplifier design, are applicable to wireless broadband communication.
Brief description of the drawings
Fig. 1 is traditional wideband low noise amplifier.
Fig. 2 is the circuit theory diagrams of ultra-wideband low-noise amplifier of the present invention.
Fig. 3 is the input reflection coefficient simulation curve of ultra-wideband low-noise amplifier of the present invention.
Fig. 4 is the gain simulation curve of ultra-wideband low-noise amplifier of the present invention.
Fig. 5 is the noise factor simulation curve of ultra-wideband low-noise amplifier of the present invention.
Fig. 6 is three rank input intermodulation point simulation curves of ultra-wideband low-noise amplifier of the present invention.
Embodiment
Below in conjunction with Fig. 2, ultra-wideband low-noise amplifier of the present invention is described further.
Ultra-wideband low-noise amplifier of the present invention is mainly made up of jointly input amplifying stage, feedback stage, matching stage, load stage, bias stage and output buffer stage circuit, and annexation and the role of each several part are as follows:
Supply voltage VDD is 1.2V, and GND is 0V;
Input amplifying stage is made up of jointly nmos pass transistor MN1, MN2 and PMOS transistor MP1, in order to realize the enlarging function to input signal, and the source ground of MN1, drain electrode is connected with the drain electrode of MP1 and the source electrode of MN2 respectively, and the source electrode of MP1 connects power vd D;
Feedback stage is made up of jointly nmos pass transistor MN3, resistance R _ f and capacitance C1, C2, the drain electrode of MN3 meets power vd D, grid connects the output of input amplifying stage, source electrode connects feedback resistance Rf, and by capacitance C1, C2 be connected to input amplifying stage input, be used for realizing feedback and obtain equivalent input impedance in circuit, thereby make matching stage realize input impedance coupling;
Matching stage is made up of jointly the pad parasitic capacitance CP with esd protection, sheet internal inductance L1, feedback device MN3, Rf, C1, C2, inductance L 1 compensates the capacitive of input, choose suitable inductance value and can realize wide-band impedance coupling, thereby reach the object that obtains good input reflection coefficient in needed frequency band;
Load stage is made up of resistance R L, sheet internal inductance L2, capacitor C L, thereby RL, L2 play as low noise amplifier provides load and realize the effect of normal amplifying signal, inductance L 2 is connected with resistance R L, the electric capacity that CL introduces for simulation low noise amplifier next stage (frequency mixer);
Biasing part is by current source I1, I2, nmos pass transistor MN4, MN5, MN6, MN7, PMOS transistor MP2, resistance R 1, R2, R3 form jointly, bias stage is connected to respectively the grid of MN1 and MP1 in input amplifying stage by resistance R 1, R2, play the effect that bias current is provided for low noise amplifier, so that low noise amplifier individual channel can normally be worked, input amplifying stage, the required electric current of feedback stage provide by bias stage;
Output buffer stage is made up of nmos pass transistor MN8, resistance R 4, the grid of MN8 is connected with the output (drain electrode of MN2) of input amplifying stage, the source electrode of MN8 is connected with resistance R 4, output DC potential can be adjusted to suitable value, also can carry out impedance matching to output port, be convenient to the independent test after low noise amplifier flow.
Vin is radio-frequency input signals, in the situation that Input matching is good, through C1, after C2, enter MN1, the grid of MP1, input out the source that enters MN2 from the drain terminal of MN1 and MP1, and export from the drain terminal of MN2, be equivalent to like this MN1, MP1 has used current multiplexing technology, form mutual conductance enhancement mode cascade amplifying stage with MN2 simultaneously, be conducive to improve gain, bank tube MN2 is used for strengthening the reverse isolation of low noise amplifier altogether, suppress Miller effect, reduce the local oscillation signal leakage of subsequent conditioning circuit (as frequency mixer) generation and reduced the feedback effect of output to input, improve the stability of circuit.
The drain terminal of MN2 is connected with load resistance RL and inductance L 2, can realize like this amplification to input signal, inductance L 2 has certain compensating action to high-frequency gain, thereby can expand the bandwidth of low noise amplifier, L2 be carried out to suitable value and can make ultra-wideband low-noise amplifier there is good gain flatness.
The drain terminal of MN2 is to there being a feedback control loop between input signal port; formed by MN3, Rf; because transistor has parasitic capacitance; esd protection also presents capacitive; in order to compensate the capacitive of input; the present invention has used inductance L 1 to do compensation to a certain degree, can realize like this coupling that input is good, makes being reflected within the scope of acceptable of input signal Vin.The condition of low noise amplifier input impedance coupling is
1/g
mn3+R
f=R
S(1+A
v) (3)
Rs is source input impedance, Rs value 50 Ω in the present invention, g
mn3for the mutual conductance of transistor MN3, R
ffor the resistance with internal resistance Rf in feedback control loop, A
vfor the input signal of MN2 drain terminal and the ratio of input signal.Known according to (3) formula, if want Satisfying Matching Conditions, have
R
f<R
S(1+A
v) (4)
The drain terminal of MN2 is connected to the grid of buffer stage MN8, the source electrode contact resistance R4 of MN8, and output signal Vout is radio frequency output signal, Vout is from the junction output between resistance R 4 and MN8.By regulating the output impedance of buffer stage MN8 and R4, make the impedance matching with tester, can after flow, test separately to low noise amplifier, simultaneous buffering level has further strengthened the isolation of low noise amplifier, and in the present invention, buffer stage has the decay of 2dB to gain.
Normally work if realize input amplifying stage, need to set up suitable quiescent point.The present invention adopts capacitance C1, C2 to make to input amplifying stage transistor MN1, MP1 to have independently biasing, thereby is not subject to the impact of the factors such as technique; Current source I1, transistor MN6 and resistance R 1 provide suitable bias current for MN1, to complete the effect of current mirror; Transistor MN7, MP2 and resistance R 2, R3 provide suitable bias current for MP1, to complete the effect of current mirror; Current source I2, transistor MN4, MN5, for feedback control loop provides stable electric current, complete the effect of current mirror, thereby ensure that MN3 has relatively constant mutual conductance.
Capacitor C L is load capacitance, is used for simulating the grid of next stage (frequency mixer) to the electric capacity on ground, and it is 100fF that CL is set when emulation.
The simulation curve of the input reflection coefficient (S11) of ultra-wideband low-noise amplifier of the present invention as shown in Figure 3.All be less than-10dB of input reflection coefficient in 0.1-12GHz frequency range, meets the requirement of general low noise amplifier input impedance coupling.Gain curve (Gain) as shown in Figure 4.In 0.1-12GHz frequency range, gain and change between 15.26-16.76dB, realized good gain flatness.
Ultra-wideband low-noise amplifier noise factor of the present invention (Noise Figure) as shown in Figure 5, in 0.1-12GHz frequency range, noise factor is between 2.3-3.5dB, and in 0.2-8GHz frequency range, be less than 2.8dB, meet the low noise requirement of ultra-wideband low-noise amplifier completely.
For low noise amplifier, the linearity is also vital, it determined low noise amplifier the maximum intensity of receptible signal, low noise amplifier of the present invention is under the power supply of 1.2V supply voltage, the simulation curve of 3 rank input intermodulation points (IIP3) as shown in Figure 6, in 0.1-12GHz frequency range, IIP3 changes between-4.4dBm at-10dBm, meets the linearity of general low noise amplifier.
In sum, ultra-wideband low-noise amplifier of the present invention uses 65nm RFCMOS technique to carry out simulating, verifying, in 0.1-12GHz bandwidth, can normally work, Input matching is functional, noise and the linearity all can meet normal working index, and main amplifying stage electric current is 5.54mA, and feedback stage electric current is 1.73mA, buffer stage electric current is 1.38mA below, consumes total current and is about 8.65mA.
Finally it should be noted that the present invention is not only applicable to work in the low noise amplifier in 0.1-12GHz bandwidth range, the present invention proposes concrete scheme and simulating, verifying, therefore only otherwise depart from the enforcement thought in the present invention, all belong in claim scope of the present invention.