CN104167991A - Variable-gain low-noise amplifying circuit, variable-gain method thereof and receiver - Google Patents
Variable-gain low-noise amplifying circuit, variable-gain method thereof and receiver Download PDFInfo
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- CN104167991A CN104167991A CN201310184364.5A CN201310184364A CN104167991A CN 104167991 A CN104167991 A CN 104167991A CN 201310184364 A CN201310184364 A CN 201310184364A CN 104167991 A CN104167991 A CN 104167991A
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Abstract
The invention discloses a variable-gain low-noise amplifying circuit, a variable-gain method of the variable-gain low-noise amplifying circuit and a receiver. The variable-gain low-noise amplifying circuit comprises a low-noise amplifier, a bypass switching circuit, a first power circuit and a second power circuit. The low-noise amplifier receives radio frequency input signals. The bypass switching circuit receives switching signals and determines a closed state or an open state according to the switching signals. When the power of the radio frequency input signals is larger than a first power threshold value, the bypass switching circuit is closed so that first driving resistance can be formed by the bypass switching circuit, in addition, the first power circuit and the second power circuit are opened according to a first enabling signal and a second enabling signal respectively so that the low-noise amplifier can be turned off, and the radio frequency input signals are attenuated in a shallow mode through the first driving resistance. When the power of the radio frequency input signals is larger than a second power threshold value, the voltage level of the switching signals is improved so that second driving resistance can be formed by the low-noise amplifier, and the radio frequency input signals are attenuated in a deep mode through the first driving resistance and the second driving resistance.
Description
Technical field
The present invention is about a kind of amplifier circuit in low noise, refers to that especially a kind of power level according to radio-frequency input signals adjusts the amplifier circuit in low noise of gain.
Background technology
Radio communication continues to grow up with unprecedented speed.Now the whole world have exceed 1,000,000,000 action wireless devices.The whole world has for the networking of taking action, wide area networking, local-area network, public security communication and the multiple frequency bands of military communication and communication standard/agreement, and it makes immanent communication be difficult to become best.
Low noise amplifier (Low Noise Amplifier, LNA) is generally used in communication system, and its effect is to be enlarged into the signal of low noise figure via the faint input signal of antenna reception.In addition, low noise amplifier (LNA) is normally placed in the front end of communication system.Generally speaking, low noise amplifier can reduce most noise and amplify near the desired signal (desired signal) of a centre frequency.Not only can improve thus the signal to noise ratio of communication system than (SNR), also can promote the quality that receives signal.
In wireless communication system, the low noise amplifier in receiver is responsible for faint radio-frequency input signals being amplified and offering the demodulator circuit use of rear end.But, in some cases, if receiver very near under signal emitting-source (that is base station), excessively strong transmitting easily causes low noise amplifier saturated, and then causes receiver system to degenerate.
Summary of the invention
The object of the present invention is to provide a kind of variable gain low-noise amplifying circuit, variable gain low-noise amplifying circuit comprises low noise amplifier, by-pass switch circuit, the first power circuit and second source circuit.Low noise amplifier received RF input signal.The by-pass switch circuit low noise amplifier that is connected in parallel, described by-pass switch circuit receiving key signal also determines conducting or cut-off state accordingly.The first power circuit is connected to low noise amplifier and by-pass switch circuit, and described the first power circuit receives the first enable signal and exports accordingly the first output voltage.Second source circuit is connected to low noise amplifier and by-pass switch circuit, and described second source circuit receives the second enable signal and exports accordingly the second output voltage.In the time that the power of radio-frequency input signals is greater than the first power threshold value, conducting by-pass switch circuit and make its form first initiatively resistance and first and second power circuit close so that low noise amplifier cuts out according to first and second enable signal respectively, by first initiatively resistance with shallow degree decay radio-frequency input signals; In the time that the power of radio-frequency input signals is greater than the second power threshold value, improve the voltage level of switching signal so that low noise amplifier forms the second resistance initiatively, by first and second initiatively resistance with depth attenuation's radio-frequency input signals.
In one of them embodiment of the present invention, variable gain low-noise amplifying circuit also comprises the first resistance and the second resistance.One end of the first resistance connects second source circuit to receive the second output voltage.One end of the second resistance connects the other end and the low noise amplifier of the first resistance, and its other end connects earthed voltage.The first resistance and the second resistance form bleeder circuit, and the second output voltage is given exporting starting resistor to low noise amplifier after dividing potential drop, and the second power threshold value is greater than the first power threshold value.
In one of them embodiment of the present invention, the first output voltage be system voltage or earthed voltage one of them, and the second output voltage be bias voltage or earthed voltage one of them.
In one of them embodiment of the present invention, low noise amplifier comprises output transistor.The grid of output transistor connects radio-frequency input signals and starting resistor, its source electrode connects earthed voltage, its drain electrode connects the first power circuit to receive the first output voltage and output radio frequency output signal, wherein work in the output transistor of saturation region in order to radio-frequency input signals is amplified, and the output transistor that works in linear zone is the second resistance initiatively.
In one of them embodiment of the present invention, by-pass switch circuit comprises switching transistor.The grid receiving key signal of switching transistor also determines conducting or cut-off state accordingly, its source electrode connects the grid of output transistor, its drain electrode connects the first power circuit to receive the first output voltage, and wherein switching transistor is adjusted the resistance value of the first active resistance according to the voltage level of switching signal.In the time that the power of radio-frequency input signals is greater than the first power threshold value, switching transistor can work in linear zone to form the first active resistance according to the voltage level of switching signal, and first and second power circuit cuts out so that output transistor is closed according to first and second enable signal respectively, so by first initiatively resistance with shallow degree this radio-frequency input signals of decaying.
In one of them embodiment of the present invention, in the time that the power of radio-frequency input signals is greater than the second power threshold value, the voltage level that improves switching signal makes switching transistor work in linear zone and has formed the first active resistance, improve by this starting resistor and open output transistor and make output transistor work in linear zone to form the second active resistance, and then pass through first and second active resistance with depth attenuation's radio-frequency input signals.
The embodiment of the present invention separately provides a kind of receiver, and receiver comprises variable gain low-noise amplifying circuit, demodulator circuit and load.Variable gain low-noise amplifying circuit is in order to received RF input signal and output radio frequency output signal.Demodulator circuit connects variable gain low-noise amplifying circuit, and described demodulator circuit is in order to demodulation radio frequency output signal and export restituted signal.Load connects demodulator circuit, described load receiving demodulation signal.
The embodiment of the present invention provides a kind of variable gain method again, and variable gain method comprises the following steps: detect radio-frequency input signals; Whether the power that judges radio-frequency input signals is greater than the first power threshold value; If the power of radio-frequency input signals is greater than the first power threshold value, continue to judge whether the power of radio-frequency input signals is greater than the second power threshold value; If the power of radio-frequency input signals between first and second power threshold value, passes through the first active resistance with shallow degree decay radio-frequency input signals; If the power of radio-frequency input signals is greater than the second power threshold value, pass through the first active resistance and the second active resistance with this radio-frequency input signals of depth attenuation
In sum, the variable gain low-noise amplifying circuit that the embodiment of the present invention proposes and variable gain method and receiver, can by detect the power level of radio-frequency input signals decide enter " normal mode ", " shallow degree evanescent mode " and " depth attenuation's pattern " one of them, and by the impedance effect of the conducting resistance radio-frequency input signals of decaying that carrys out different amplitudes.Accordingly, to reach effect of protection receiver back-end circuit.
For enabling further to understand feature of the present invention and technology contents, refer to following about detailed description of the present invention and accompanying drawing, but these explanations and appended graphic the present invention that are only used for illustrating but not are done any restriction to claim scope of the present invention.
Brief description of the drawings
Fig. 1 is according to the block schematic diagram of the variable gain low-noise amplifying circuit of the embodiment of the present invention.
Fig. 2 is according to the circuit diagram of the variable gain low-noise amplifying circuit of the embodiment of the present invention.
Fig. 3 A is according to the oscillogram of the power level of the radio-frequency input signals of the embodiment of the present invention.
Fig. 3 B is according to the drive waveforms figure of the switching signal of the embodiment of the present invention.
Fig. 4 is according to the simulation curve figure of the variable gain low-noise amplifying circuit of the normal mode of the embodiment of the present invention.
Fig. 5 is according to the circuit diagram of the variable gain low-noise amplifying circuit of the shallow degree evanescent mode of the embodiment of the present invention.
Fig. 6 is according to the simulation curve figure of the variable gain low-noise amplifying circuit of the shallow degree evanescent mode of the embodiment of the present invention.
Fig. 7 is according to the circuit diagram of the variable gain low-noise amplifying circuit of embodiment of the present invention depth attenuation pattern.
Fig. 8 is according to the simulation curve figure of the variable gain low-noise amplifying circuit of depth attenuation's pattern of the embodiment of the present invention.
Fig. 9 is the block schematic diagram according to the receiver of the embodiment of the present invention.
Figure 10 is according to the flow chart of the variable gain method of the embodiment of the present invention.
Wherein, description of reference numerals is as follows:
100,200,500,700: variable gain low-noise amplifying circuit
110: low noise amplifier
120: by-pass switch circuit
130: the first power circuits
140: second source circuit
150: bleeder circuit
160: detector
170: controller
900: receiver
910: variable gain low-noise amplifying circuit
920: demodulator circuit
930: load
A, B: signal path
C1: the first electric capacity
C2: the second electric capacity
EN1: the first enable signal
EN2: the second enable signal
GND: earthed voltage
GBS: switching signal
L1: the first inductance
L2: the second inductance
M: switching transistor
Q: output transistor
R1: the first resistance
R2: the second resistance
RFIN: radio-frequency input signals
RFOUT: radio frequency output signal
RS: testing result
T1, t2: time
TH1: the first power threshold value
TH2: the second power threshold value
VG: starting resistor
VH1: the first high-voltage level
VH2: the second high-voltage level
VL: low voltage level
VOUT1: the first output voltage
VOUT2: the second output voltage
S1010, S1020, S1030, S1040, S1050: step
Embodiment
Below describing more fully various exemplary embodiments referring to alterations, in alterations, show some exemplary embodiments.But concept of the present invention may be with many multi-form embodiments, and should not be construed as and be limited to the exemplary embodiments set forth herein.Definite, provide these exemplary embodiments to make the present invention will be for detailed and complete, and will fully pass on the category of concept of the present invention to those skilled in the art.All graphic in, can be for clear and lavish praise on oneself size and the relative size in Ceng Ji district.Similar numeral is indicated like all the time.
Although should be understood that herein and may describe various elements by term first, second, third, etc., these elements are not limited by these terms should.These terms are to distinguish an element and another element.Therefore the first element of, below discussing can be described as the second element and does not depart from the teaching of concept of the present invention.As used herein, term " and/or " comprise any one and one or many person's all combinations in project of listing that are associated.
(embodiment of variable gain low-noise amplifying circuit)
Please refer to Fig. 1, Fig. 1 is according to the block schematic diagram of the variable gain low-noise amplifying circuit of the embodiment of the present invention.As shown in Figure 1, variable gain low-noise amplifying circuit 100 comprises low noise amplifier 110, by-pass switch circuit 120, the first power circuit 130, second source circuit 140 and bleeder circuit 150.By-pass switch circuit 120 low noise amplifier 110 that is connected in parallel.The first power circuit 130 is connected to low noise amplifier 110 and by-pass switch circuit 120.Second source circuit 140 is connected to bleeder circuit 150.Bleeder circuit 150 is connected to low noise amplifier 110 and by-pass switch circuit 120.The circuit that bleeder circuit 150 is made up of resistance.In the present embodiment, low noise amplifier 110 is generally in order in communication system and in order to received RF input signal RFIN, that is its effect will be enlarged into the signal of low noise figure (low noise figure) via the faint radio-frequency input signals RFIN of antenna reception.By-pass switch circuit 120 is in order to receive a switching signal GBS and to determine accordingly conducting or cut-off state.The first power circuit 130 receives one first enable signal EN1 and exports accordingly one first output voltage VO UT1, second source circuit 140 receives the second enable signal EN2 and exports accordingly the second output voltage VO UT2, the first output voltage VO UT1 be system voltage or earthed voltage one of them, and the second output voltage VO UT1 be bias voltage or earthed voltage one of them.Bleeder circuit 150 gives dividing potential drop and exports accordingly a starting resistor VG to low noise amplifier 110 in order to the second output voltage VO UT2 that it is received.
In wireless communication system, the low noise amplifier in receiver is responsible for faint radio-frequency input signals being amplified and offering the demodulator circuit use of rear end.But, in some cases, if receiver very near under signal emitting-source (that is base station), excessively strong transmitting easily causes low noise amplifier saturated, and then causes receiver system to degenerate.Accordingly, low noise amplifier need to have the ability, and shallow degree is decayed or these excessively strong radio-frequency input signalss of depth attenuation are stable to maintain receiver system.
Next wanting teaching, is the operation principle that further illustrates variable gain low-noise amplifying circuit 100.
Continue referring to Fig. 1, in the present embodiment, variable gain low-noise amplifying circuit 100 detects the power level of radio-frequency input signals RFIN by detector 160, and this testing result RS is sent to controller 170 by detector 160, then controller 170 can transmit respectively the first enable signal EN1 according to testing result RS, the first power circuit 130 that the second enable signal EN2 is extremely corresponding with switching signal GBS, second source circuit 140 and by-pass switch circuit 120 are to control its relevant action, by this radio-frequency input signals RFIN of different capacity intensity is carried out to decay in various degree.Furthermore, in the time that detector 160 detects that the power of radio-frequency input signals RFIN is greater than the first power threshold value, variable gain low-noise amplifying circuit 100 can enter " shallow degree evanescent mode " and detector 160 and this testing result RS can be sent to controller 170, then controller 170 can according to testing result RS transmit respectively the first enable signal EN1, the second enable signal EN2 with switching signal GBS to the first corresponding power circuit 130, second source circuit 140 and by-pass switch circuit 120.By-pass switch circuit 120 can be switched on and form according to switching signal GBS the kenel of the first active resistance, and the first power circuit 130 cuts out according to the first enable signal EN1 and the second enable signal EN2 respectively with second source circuit 140, that is its output voltage VO UT1 and the VOUT2 of corresponding output be earthed voltage or no-voltage (zero voltage), accordingly so that low noise amplifier 110 close.Therefore, when radio-frequency input signals RFIN enters into after the input of variable gain low-noise amplifying circuit 100, can transfer a radio frequency output signal RFOUT to the output of variable gain low-noise amplifying circuit 100 via by-pass switch circuit 120 and export next stage circuit blocks (not illustrating) to, that is, radio-frequency input signals RFIN can be bypassed that switching circuit 120 forms first initiatively resistance carry out shallow degree its power level of decaying.
On the other hand, in the time that detector 160 detects that the power of radio-frequency input signals RFIN is greater than the second power threshold value (the second power threshold value is greater than the first power threshold value), variable gain low-noise amplifying circuit 100 can enter " depth attenuation's pattern " and detector 160 and can equally this testing result RS be sent to controller 170, then controller 170 can transmit respectively the first enable signal EN1 according to testing result RS, the first power circuit 130 second source circuit 140 and by-pass switch circuit 120 that the second enable signal EN2 is extremely corresponding with switching signal GBS, wherein the first power circuit and 130 and the output voltage VO UT1 that exports of second source circuit 140 and VOUT2 be still earthed voltage.It should be noted that, the voltage level that this Time Controller 170 is sent to the switching signal GBS of by-pass switch circuit 120 is greater than the voltage level of " shallow degree evanescent mode " lower switching signal GBS, draws high a little the voltage level of starting resistor VG so that low noise amplifier 110 forms the second active resistance by the voltage level that improves switching signal GBS.Therefore, when radio-frequency input signals RFIN enters into after the input of variable gain low-noise amplifying circuit 100, first the second active depth attenuation of resistance institute that initiatively resistance and low noise amplifier 110 form that radio-frequency input signals RFIN can be bypassed that switching circuit 120 forms, and export a radio frequency output signal RFOUT to next stage circuit blocks (not illustrating) at the output of variable gain low-noise amplifying circuit 100.
In order to illustrate in greater detail the operation workflow of variable gain low-noise amplifying circuit 100 of the present invention, below by for one of being at least further described in multiple embodiment and sequentially describing with " depth attenuation's pattern " with regard to three kinds of patterns " normal mode ", " the shallow degree evanescent mode " of variable gain low-noise amplifying circuit.
In ensuing multiple embodiment, description is different to the part of above-mentioned Fig. 1 embodiment, and all the other clippeds are identical with the part of above-mentioned Fig. 1 embodiment.In addition,, for the purpose of facility is described, similar reference number or label are indicated similar element.
(another embodiment of variable gain low-noise amplifying circuit)
Please refer to Fig. 2, Fig. 2 is according to the circuit diagram of the variable gain low-noise amplifying circuit of the embodiment of the present invention.Fig. 2 embodiment is for disclosing the relevant start of variable gain low-noise amplifying circuit at " normal mode ", and different from above-mentioned Fig. 1 embodiment, bleeder circuit 150 comprises the first resistance R 1 and the second resistance R 2.Low noise amplifier 110 comprises output transistor Q.By-pass switch circuit 120 comprises switching transistor M.Variable gain low-noise amplifying circuit 200 also comprises one first inductance L 1, the first capacitor C 1, the second inductance L 2 and the second capacitor C 2.One end of the first resistance R 1 connects second source circuit 140.One end of the second resistance R 2 connects the other end of the first resistance R 1, and the other end of the second resistance R 2 connects earthed voltage GND.The grid of output transistor Q connects one end of the second resistance R 2, and the source electrode of output transistor Q connects earthed voltage GND.One end of the first inductance L 1 connects radio-frequency input signals RFIN, and the other end of the first inductance L 1 connects one end of the first capacitor C 1, and the other end of the first capacitor C 1 connects the grid of output transistor Q.The grid receiving key signal GBS of switching transistor M also determines conducting or cut-off state accordingly, and the source electrode of switching transistor M connects the grid of output transistor Q.The drain electrode of switching transistor M connects one end of the second capacitor C 2.The other end of the second capacitor C 2 connects one end of the second inductance L 2, and the other end of the second inductance L 2 connects the first power circuit 130.
Next wanting teaching, is the operation principle that further illustrates the variable gain low-noise amplifying circuit 200 of " normal mode ".
Referring to Fig. 2, Fig. 3 A and Fig. 3 B, Fig. 3 A is according to the oscillogram of the power level of the radio-frequency input signals of the embodiment of the present invention.Fig. 3 B is according to the drive waveforms figure of the switching signal of the embodiment of the present invention.Before time t1, the power level that radio-frequency input signals RFIN detected when detector 160 is in normal range (NR), that is the power level of radio-frequency input signals RFIN is less than the first power threshold value TH1, variable gain low-noise amplifying circuit 200 can enter " normal mode " and detector 160 and can equally this testing result RS be sent to controller 170, then controller 170 can transmit respectively the first enable signal EN1 according to testing result RS, the first power circuit 130 that the second enable signal EN2 is extremely corresponding with switching signal GBS, second source circuit 140 and switching transistor M.Accordingly, switching transistor M can end or disconnect according to the switching signal GBS of low voltage level VL, the first power circuit 130 can be exported system voltage according to the first enable signal EN1 as the first output voltage VO UT1, second source circuit 140 can export bias voltage to bleeder circuit 150 as the second output voltage VO UT2 according to the second enable signal EN2, the dividing potential drop ratio that wherein bleeder circuit 150 forms by the first resistance R 1 and the second resistance R 2 carrys out further bias voltage to be given dividing potential drop and exports the grid of a starting resistor VG to output transistor Q, now, output transistor Q is operated in saturation region.Therefore, when radio-frequency input signals RFIN enters into after the input of variable gain low-noise amplifying circuit 200, radio-frequency input signals RFIN can be enlarged into by the output transistor Q of low noise amplifier 110 the radio frequency output signal RFOUT of low noise figure, to improve the signal to noise ratio of communication system than (SNR), wherein radio-frequency input signals RFIN can follow signal path A and amplified and transfer radio-frequency input signals RFOUT to.Then, referring to Fig. 4, Fig. 4 is according to the simulation curve figure of the variable gain low-noise amplifying circuit of the normal mode of the embodiment of the present invention, and its transverse axis is for representing frequency (unit is GHz), and its longitudinal axis is for representing gain (unit is dB).As shown in Figure 4, be about 18.157dB at the variable gain low-noise amplifying circuit 200 of " normal mode " in the gain under 2.45GHz, it conforms with the communication standard of low noise amplifier very much.
Next wanting teaching, is the operation principle that further illustrates the variable gain low-noise amplifying circuit of " shallow degree evanescent mode ".
(embodiment again of variable gain low-noise amplifying circuit)
Referring to Fig. 3 A, Fig. 3 B and Fig. 5, Fig. 5 is according to the circuit diagram of the variable gain low-noise amplifying circuit of the shallow degree evanescent mode of the embodiment of the present invention.Fig. 5 embodiment is for disclosing the 500 relevant starts at " shallow degree evanescent mode " of variable gain low-noise amplifying circuit.Between time t1 and time t2, in the time that detector 160 detects that the power level of radio-frequency input signals RFIN is greater than the first power threshold value TH1, that is the power level of radio-frequency input signals RFIN is between the first power threshold value and the second power threshold value TH2, variable gain low-noise amplifying circuit 500 can enter " shallow degree evanescent mode " and detector 160 and can equally this testing result RS be sent to controller 170, then controller 170 can transmit respectively the first enable signal EN1 according to testing result RS, the first power circuit 130 that the second enable signal EN2 is extremely corresponding with switching signal GBS, second source circuit 140 and switching transistor M.Switching transistor M can be according to the switching signal GBS of the first high-voltage level VH1 and conducting and enter into the range of linearity to form the first resistance (that is conducting resistance of switching transistor M) initiatively, the first power circuit 130 can be exported earthed voltage according to the first enable signal EN1 as the first output voltage VO UT1, second source circuit 140 can export earthed voltage to bleeder circuit 150 as the second output voltage VO UT2 according to the second enable signal EN2, the dividing potential drop ratio that wherein bleeder circuit 150 forms by the first resistance R 1 and the second resistance R 2 carrys out further earthed voltage to be given dividing potential drop and exports the grid of a starting resistor VG to output transistor Q, now output transistor Q is for being operated in cut-off region.Therefore, when radio-frequency input signals RFIN enters into after the input of variable gain low-noise amplifying circuit 500, radio-frequency input signals RFIN can follow signal path B and respectively through the first initiatively resistance (the switching transistor M that enters into the range of linearity forms) and the second capacitor C 2 and output of the variable gain low-noise amplifying circuit 500 that arrives, that is the present embodiment is by the next shallow degree decay of the impedance effect radio-frequency input signals RFIN of the first active resistance, unstable to avoid receiver system to suffer strong radiofrequency signal.Referring to Fig. 6, Fig. 6 is according to the simulation curve figure of the variable gain low-noise amplifying circuit of the shallow degree evanescent mode of the embodiment of the present invention, its transverse axis is for representing frequency (unit is GHz), and its longitudinal axis is for representing gain (unit is dB).As shown in Figure 6, at the variable gain low-noise amplifying circuit 500 of " shallow degree evanescent mode " at be about-3.056dB of the gain under 2.45GHz.
(a more embodiment of variable gain low-noise amplifying circuit)
Referring to Fig. 3 A, Fig. 3 B and Fig. 7, Fig. 7 is according to the circuit diagram of the variable gain low-noise amplifying circuit of embodiment of the present invention depth attenuation pattern.Fig. 7 embodiment is for disclosing the 700 relevant starts in " depth attenuation's pattern " of variable gain low-noise amplifying circuit.After time t2, in the time that detector 160 detects that the power level of radio-frequency input signals RFIN is greater than the second power threshold value TH2, variable gain low-noise amplifying circuit 700 can enter " depth attenuation's pattern " and detector 160 and can equally this testing result RS be sent to controller 170, then controller 170 can according to testing result RS transmit respectively the first enable signal EN1, the second enable signal EN2 with switching signal GBS to the first corresponding power circuit 130 second source circuit 140 and switching transistor M.Switching transistor M can continue conducting and still maintain the range of linearity to form more the first active resistance (that is conducting resistance of switching transistor M) of high impedance according to the switching signal GBS of the second high-voltage level VH2, wherein the second high-voltage level VH2 is slightly larger than the first high-voltage level VH1, it all makes switching transistor M conducting and enters into the range of linearity, that is this disclosure utilizes different voltage levels to reach the first active resistance of different resistance values.The first power circuit 130 can continue earthed voltage to export as the first output voltage VO UT1 according to the first enable signal EN1, second source circuit 140 can continue bias voltage to export bleeder circuit 150 to as the second output voltage VO UT2 according to the second enable signal EN2, and the dividing potential drop ratio that wherein bleeder circuit 150 forms by the first resistance R 1 and the second resistance R 2 carrys out further earthed voltage to be given dividing potential drop and exports the grid of a starting resistor VG to output transistor Q.It should be noted that, because the grid of switching transistor receives the switching signal GBS of the second high-voltage level VH2, can therefore draw high the level of the grid voltage of output transistor Q, that is now starting resistor VG is not for the magnitude of voltage size of no-voltage and starting resistor can make output transistor Q enter into the range of linearity, and then make output transistor Q form the second active resistance (that is conducting resistance of output transistor Q).In simple terms, the present embodiment is deepened the attenuation amplitude of radio-frequency input signals RFIN by the first active resistance and the second active resistance.Therefore, when radio-frequency input signals RFIN enters into after the input of variable gain low-noise amplifying circuit 700, radio-frequency input signals RFIN can follow signal path C and respectively through first initiatively resistance (the switching transistor M that enters into the range of linearity forms) with the second capacitor C 2 and the output of the variable gain low-noise amplifying circuit 700 that arrives, and radio-frequency input signals RFIN can be subject to first initiatively resistance with the impedance effect of the second active resistance and therefore significantly decay.Referring to Fig. 8, Fig. 8 is according to the simulation curve figure of the variable gain low-noise amplifying circuit of depth attenuation's pattern of the embodiment of the present invention, its transverse axis is for representing frequency (unit is GHz), and its longitudinal axis is for representing gain (unit is dB).As shown in Figure 8, at the variable gain low-noise amplifying circuit 700 of " depth attenuation's pattern " at be about-13.188dB of the gain under 2.45GHz.
Generally speaking, this disclosure by detect the power level of radio-frequency input signals decide enter " normal mode ", " shallow degree evanescent mode " and " depth attenuation's pattern " one of them, and by the impedance effect of the conducting resistance radio-frequency input signals of decaying.It is worth mentioning that, this disclosure not only have with first initiatively resistance decay " the shallow degree evanescent mode " of radio-frequency input signals, have more with the first " depth attenuation's pattern " that initiatively resistance and the second active resistance are deepened radio-frequency input signals attenuation amplitude.
(thering is an embodiment of the receiver of variable gain low-noise amplifying circuit)
Please refer to Fig. 9, Fig. 9 is the block schematic diagram according to the receiver of the embodiment of the present invention.Receiver 900 comprises variable gain low-noise amplifying circuit 910, demodulator circuit 920 and load 930.Demodulator circuit 920 connects variable gain low-noise amplifying circuit 910, and load 930 connects demodulator circuit 920.Demodulator circuit 920 is in order to demodulation radio frequency output signal RFOUT and export restituted signal OUT to load 930.Variable gain low-noise amplifying circuit 910 can be one of them of variable gain low-noise amplifying circuit 100,200,500 and 700 in above-described embodiment, and receive by antenna the radio-frequency input signals RFIN that base station is launched, and decide and enter " normal mode ", " shallow degree evanescent mode " and " depth attenuation's pattern " by detecting the power level of radio-frequency input signals RFIN, and by the impedance effect of the conducting resistance radio-frequency input signals RFIN that decays.
(embodiment of variable gain method)
Please refer to Figure 10, Figure 10 is according to the flow chart of the variable gain method of the embodiment of the present invention.The described method of this example can be carried out at the portable electronic devices of the variable gain low-noise amplifying circuit shown in Fig. 1, Fig. 2, Fig. 5 or Fig. 7, therefore please with reference to Fig. 1, Fig. 2, Fig. 5 or Fig. 7 in order to understanding.Variable gain method comprises the following steps: detect radio-frequency input signals (step S1010).Whether the power that judges radio-frequency input signals is greater than the first power threshold value (step S1020).If the power of radio-frequency input signals is greater than the first power threshold value, continue to judge whether the power of radio-frequency input signals is greater than the second power threshold value (step S1030).If the power of radio-frequency input signals between first and second power threshold value, passes through the first active resistance with shallow degree decay radio-frequency input signals (step S1040).If the power of radio-frequency input signals is greater than the second power threshold value, pass through the first active resistance and the second active resistance with depth attenuation's radio-frequency input signals (step S1050).
Correlative detail about each step of the variable gain method of variable gain low-noise amplifying circuit describes in detail at above-mentioned Fig. 1～Fig. 8 embodiment, does not repeat for this reason at this.
Should be noted that at this, each step of Figure 10 embodiment only for convenience of description need, the embodiment of the present invention is not using each step order to each other as the restrictive condition of implementing the present invention each embodiment.
(possible effect of embodiment)
In sum, the variable gain low-noise amplifying circuit that the embodiment of the present invention proposes and variable gain method and receiver, can by detect the power level of radio-frequency input signals decide enter " normal mode ", " shallow degree evanescent mode " and " depth attenuation's pattern " one of them, and by the impedance effect of the conducting resistance radio-frequency input signals of decaying that carrys out different amplitudes.Accordingly, to reach effect of protection receiver back-end circuit.
The foregoing is only embodiments of the invention, it is not in order to limit to Patent right requirement scope of the present invention.
Claims (10)
1. a variable gain low-noise amplifying circuit, is characterized in that, this variable gain low-noise amplifying circuit comprises:
One low noise amplifier, receives a radio-frequency input signals;
Path switching circuit on one side, this low noise amplifier that is connected in parallel, this by-pass switch circuit receives a switching signal and determines accordingly conducting or cut-off state;
One first power circuit, is connected to this low noise amplifier and this by-pass switch circuit, and this first power circuit receives one first enable signal and exports accordingly one first output voltage; And
One second source circuit, is connected to this low noise amplifier and this by-pass switch circuit, and this second source circuit receives one second enable signal and exports accordingly one second output voltage,
Wherein in the time that the power of this radio-frequency input signals is greater than one first power threshold value, this by-pass switch circuit of conducting and make its form one first initiatively resistance and this first and this second source circuit respectively according to this first and this second enable signal close so that this low noise amplifier cuts out, by this first initiatively resistance with shallow degree this radio-frequency input signals of decaying; In the time that the power of this radio-frequency input signals is greater than one second power threshold value, improve the voltage level of this switching signal so that this low noise amplifier forms one second resistance initiatively, by this first and this second initiatively resistance with this radio-frequency input signals of depth attenuation.
2. variable gain low-noise amplifying circuit as claimed in claim 1, also comprises:
One first resistance, its one end connects this second source circuit to receive this second output voltage; And
One second resistance, its one end connects the other end and this low noise amplifier of this first resistance, and its other end connects an earthed voltage,
Wherein this first and this second resistance form a bleeder circuit, and this second output voltage is given exporting this starting resistor to this low noise amplifier after dividing potential drop, and this second power threshold value is greater than this first power threshold value.
3. variable gain low-noise amplifying circuit as claimed in claim 2, wherein this first output voltage be a system voltage or this earthed voltage one of them, and this second output voltage be a bias voltage or this earthed voltage one of them.
4. variable gain low-noise amplifying circuit as claimed in claim 2, wherein this low noise amplifier comprises:
One output transistor, its grid connects this radio-frequency input signals and this starting resistor, its source electrode connects this earthed voltage, its drain electrode connects this first power circuit to receive this first output voltage and output one radio frequency output signal, wherein work in this output transistor of saturation region in order to this radio-frequency input signals is amplified, and this output transistor that works in linear zone is this second resistance initiatively.
5. variable gain low-noise amplifying circuit as claimed in claim 4, wherein this by-pass switch circuit comprises:
One switching transistor, its grid receives this switching signal and determines accordingly conducting or cut-off state, its source electrode connects the grid of this output transistor, its drain electrode connects this first power circuit to receive this first output voltage, wherein this switching transistor is adjusted the resistance value of this first active resistance according to the voltage level of this switching signal
Wherein in the time that the power of radio-frequency input signals is greater than this first power threshold value, this switching transistor can work in linear zone to form this first active resistance according to the voltage level of this switching signal, and this first and this second source circuit respectively according to this first and this second enable signal close so that this output transistor is closed, and then by this first initiatively resistance with shallow degree this radio-frequency input signals of decaying.
6. variable gain low-noise amplifying circuit as claimed in claim 5, wherein in the time that the power of this radio-frequency input signals is greater than one second power threshold value, the voltage level that improves this switching signal makes this switching transistor work in linear zone and has formed this first active resistance, improve by this this starting resistor and open this output transistor and make this output transistor work in linear zone to form this second resistance initiatively, so by this first and this second initiatively resistance with this radio-frequency input signals of depth attenuation.
7. a receiver, is characterized in that, this receiver comprises:
One variable gain low-noise amplifying circuit as claimed in claim 1, in order to receive a radio-frequency input signals and output one radio frequency output signal;
One demodulator circuit, connects this variable gain low-noise amplifying circuit, and this demodulator circuit is in order to this radio frequency output signal of demodulation and export a restituted signal; And
One load, connects this demodulator circuit, and this load receives this restituted signal.
8. receiver as claimed in claim 7, wherein this variable gain low-noise amplifying circuit also comprises one first resistance, its one end connects this second source circuit to receive this second output voltage, and one second resistance, its one end connects the other end and this low noise amplifier of this first resistance, its other end connects an earthed voltage, wherein this first and this second resistance form a bleeder circuit, and this second output voltage is given exporting a starting resistor to this low noise amplifier after dividing potential drop, and this second power threshold value is greater than this first power threshold value, wherein this low noise amplifier comprises an output transistor, its grid connects this radio-frequency input signals and this starting resistor, its source electrode connects this earthed voltage, its drain electrode connects this first power circuit to receive this first output voltage and output one radio frequency output signal, wherein work in this output transistor of saturation region in order to this radio-frequency input signals is amplified, and this output transistor that works in linear zone is this second active resistance, and this by-pass switch circuit comprises a switching transistor, its grid receives this switching signal and determines accordingly conducting or cut-off state, its source electrode connects the grid of this output transistor, its drain electrode connects this first power circuit to receive this first output voltage, wherein this switching transistor is adjusted the resistance value of this first active resistance according to the voltage level of this switching signal, wherein in the time that the power of radio-frequency input signals is greater than this first power threshold value, this switching transistor can work in linear zone to form this first active resistance according to the voltage level of this switching signal, and this first and this second source circuit respectively according to this first and this second enable signal close so that this output transistor is closed, and then by this first initiatively resistance with shallow degree this radio-frequency input signals of decaying.
9. a variable gain method, is characterized in that, this variable gain method comprises:
Detect a radio-frequency input signals;
Whether the power that judges this radio-frequency input signals is greater than one first power threshold value;
If the power of this radio-frequency input signals is greater than this first power threshold value, continue to judge whether the power of this radio-frequency input signals is greater than one second power threshold value;
If the power of this radio-frequency input signals this first and this second power threshold value between, by one first initiatively resistance with shallow degree this radio-frequency input signals of decaying;
If the power of this radio-frequency input signals is greater than this second power threshold value, pass through this first active resistance and one second active resistance with this radio-frequency input signals of depth attenuation,
Wherein this variable gain method is for variable gain low-noise amplifying circuit as claimed in claim 1 or receiver as claimed in claim 7.
10. variable gain method as claimed in claim 9, wherein this variable gain low-noise amplifying circuit also comprises one first resistance, its one end connects this second source circuit to receive this second output voltage, and one second resistance, its one end connects the other end and this low noise amplifier of this first resistance, its other end connects an earthed voltage, wherein this first and this second resistance form a bleeder circuit, and this second output voltage is given exporting a starting resistor to this low noise amplifier after dividing potential drop, and this second power threshold value is greater than this first power threshold value, wherein this low noise amplifier comprises an output transistor, its grid connects this radio-frequency input signals and this starting resistor, its source electrode connects this earthed voltage, its drain electrode connects this first power circuit to receive this first output voltage and output one radio frequency output signal, wherein work in this output transistor of saturation region in order to this radio-frequency input signals is amplified, and this output transistor that works in linear zone is this second active resistance, and this by-pass switch circuit comprises a switching transistor, its grid receives this switching signal and determines accordingly conducting or cut-off state, its source electrode connects the grid of this output transistor, its drain electrode connects this first power circuit to receive this first output voltage, wherein this switching transistor is adjusted the resistance value of this first active resistance according to the voltage level of this switching signal, wherein in the time that the power of radio-frequency input signals is greater than this first power threshold value, this switching transistor can work in linear zone to form this first active resistance according to the voltage level of this switching signal, and this first and this second source circuit respectively according to this first and this second enable signal close so that this output transistor is closed, and then by this first initiatively resistance with shallow degree this radio-frequency input signals of decaying.
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