TW201445872A - Variable gain low noise amplifier and method thereof, and receiver - Google Patents

Abstract

A variable gain low noise amplifier (LNA) circuit is disclosed. The variable gain LNA circuit includes a LNA, a bypass switch circuit, a first power supply circuit and a second power supply circuit. The LNA receives a RF input signal, and the bypass switch circuit receives a switch signal and accordingly decides a conduction or cut-off state. When the power of the RF input signal is larger than a first power threshold value, the bypass switch circuit is conducted so as to form a first active resistor and the first and the second power supply circuit is turn-off so as to close the LNA according to a first and a second enable signal, so that the RF input signal is slightly decayed via the first active resistor; when the power of the RF input signal is larger than a second power threshold value, voltage level of the switch signal is elevated to make the LNA form a second active resistor, so that the RF input signal is significantly decayed via the first active resistor and second resistor.

Description

Variable gain low noise amplifying circuit and variable gain method and receiver thereof

The present invention relates to a low noise amplifier circuit, and more particularly to a low noise amplifier circuit that adjusts the gain based on the power intensity of the RF input signal.

The wireless communication system continues to grow at an unprecedented rate. Today there are more than one billion mobile wireless devices in the global system. The Global System has multiple frequency bands and communication standards/agreements for mobile networks, wide area networks, regional networks, public safety communications, and military communications that make ubiquitous communications difficult to be the best.

Low Noise Amplifier (LNA) is generally used in communication systems to amplify a weak input signal received via an antenna into a low noise index signal. In addition, low noise amplifiers (LNAs) are often placed at the front end of the communication system. In general, low noise amplifiers can reduce most of the noise and amplify the desired signal near a center frequency. This not only improves the signal-to-noise ratio (SNR) of the communication system, but also improves the quality of the received signal.

In wireless communication systems, the low noise amplifier in the receiver is responsible for amplifying the weak RF input signal and providing it to the back-end demodulation circuit. However, in some cases, if the receiver is very close to the signal source (ie, the base station), an excessively strong transmit signal is likely to cause saturation of the low noise amplifier, which in turn causes degradation of the receiver system.

The embodiment of the invention provides a variable gain low noise amplification circuit, and the variable gain low noise amplification circuit comprises a low noise amplifier, a bypass switch circuit, a first power supply circuit and a second power supply circuit. The low noise amplifier receives the RF input signal. The bypass switch circuit is connected in parallel with the low noise amplifier, and the bypass switch circuit receives the switch signal and determines the on or off state accordingly. The first power supply circuit is coupled to the low noise amplifier and the bypass switch circuit, the first power supply circuit receiving the first enable signal and outputting the first output voltage accordingly. The second power supply circuit is coupled to the low noise amplifier and the bypass switch circuit, the second power supply circuit receiving the second enable signal and outputting the second output voltage accordingly. When the power of the RF input signal is greater than the first power threshold, turning on the bypass switch circuit and forming the first active resistor and the first and second power circuits are respectively turned off according to the first and second enable signals, so that The low noise amplifier is turned off, and the RF input signal is slightly attenuated by the first active resistor; when the power of the RF input signal is greater than the second power threshold, the voltage level of the switching signal is increased to form a second low noise amplifier. The active resistor transmits the RF input signal deeply through the first and second active resistors.

In one embodiment of the invention, the variable gain low noise amplifying circuit further includes a first resistor and a second resistor. One end of the first resistor is coupled to the second power supply circuit to receive the second output voltage. One end of the second resistor is connected to the other end of the first resistor and the low noise amplifier, and the other end is connected to the ground voltage. The first resistor and the second resistor form a voltage dividing circuit, and the second output voltage is divided to output a starting voltage to the low noise amplifier, and the second power threshold is greater than the first power threshold.

In one of the embodiments of the present invention, the first output voltage is one of a system voltage or a ground voltage, and the second output voltage is one of a bias voltage or a ground voltage.

In one embodiment of the invention, the low noise amplifier includes an output transistor. The gate of the output transistor is connected to the RF input signal and the starting voltage, the source thereof is connected to the ground voltage, and the drain is connected to the first power circuit to receive the first output voltage and input The RF output signal is output, wherein the output transistor operating in the saturation region is used to amplify the RF input signal, and the output transistor operating in the linear region is the second active resistor.

In one of the embodiments of the invention, the bypass switch circuit includes a switching transistor. The gate of the switching transistor receives the switching signal and determines an on or off state according to which the source is connected to the gate of the output transistor, and the drain is connected to the first power circuit to receive the first output voltage, wherein the switching transistor is switched according to the switch The voltage level of the signal is adjusted to adjust the resistance of the first active resistor. When the power of the RF input signal is greater than the first power threshold, the switching transistor operates in the linear region according to the voltage level of the switching signal to form a first active resistor, and the first and second power circuits are respectively according to the first And the second enable signal is turned off to turn off the output transistor, and then the RF input signal is lightly attenuated by the first active resistor.

In one embodiment of the present invention, when the power of the RF input signal is greater than the second power threshold, the voltage level of the switching signal is increased to cause the switching transistor to operate in the linear region to form the first active resistor, thereby improving The startup voltage is turned on to turn on the output transistor and the output transistor operates in the linear region to form a second active resistor, and the first and second active resistors are used to deeply attenuate the RF input signal.

Another embodiment of the present invention provides a receiver including a variable gain low noise amplifying circuit, a demodulation circuit, and a load. The variable gain low noise amplifying circuit is configured to receive the RF input signal and output the RF output signal. The demodulation circuit is connected to a variable gain low noise amplifying circuit for demodulating the radio frequency output signal and outputting the demodulated signal. The load is coupled to a demodulation circuit that receives the demodulated signal.

The embodiment of the present invention further provides a variable gain method. The variable gain method includes the steps of: detecting an RF input signal; determining whether a power of the RF input signal is greater than a first power threshold; and if the power of the RF input signal is greater than the first power The threshold value continues to determine whether the power of the RF input signal is greater than the second power threshold; if the power of the RF input signal is between the first and second power thresholds, the RF input signal is shallowly attenuated by the first active resistor. If the RF input signal is The power is greater than the second power threshold, and the RF input signal is deeply attenuated by the first active resistor and the second active resistor

In summary, the variable gain low noise amplifying circuit and the variable gain method and receiver thereof according to the embodiments of the present invention can determine the normal mode and the shallow state by detecting the power intensity of the RF input signal. One of the degree decay mode and the "depth decay mode", and the RF input signal is attenuated differently by the impedance effect of the on-resistance. Accordingly, the effect of protecting the back-end circuit of the receiver is achieved.

The detailed description of the present invention and the accompanying drawings are to be understood by the claims The scope is subject to any restrictions.

100, 200, 500, 700‧‧‧ variable gain low noise amplifier circuit

110‧‧‧Low noise amplifier

120‧‧‧ Bypass Switch Circuit

130‧‧‧First power circuit

140‧‧‧Second power circuit

150‧‧‧voltage circuit

160‧‧‧Detector

170‧‧‧ Controller

900‧‧‧ Receiver

910‧‧‧Variable gain low noise amplifier circuit

920‧‧‧Demodulation circuit

930‧‧‧load

A, B‧‧‧ signal path

C1‧‧‧first capacitor

C2‧‧‧second capacitor

EN1‧‧‧First enable signal

EN2‧‧‧Secondary enable signal

GND‧‧‧ Grounding voltage

GBS‧‧‧ switch signal

L1‧‧‧first inductance

L2‧‧‧second inductance

M‧‧‧Switching transistor

Q‧‧‧Output transistor

R1‧‧‧first resistance

R2‧‧‧second resistance

RFIN‧‧‧RF input signal

RFOUT‧‧‧RF output signal

RS‧‧‧Detection results

T1, t2‧‧‧ time

TH1‧‧‧first power threshold

TH2‧‧‧second power threshold

VG‧‧‧ start voltage

VH1‧‧‧ first high voltage level

VH2‧‧‧ second high voltage level

VL‧‧‧low voltage level

VOUT1‧‧‧ first output voltage

VOUT2‧‧‧second output voltage

S1010, S1020, S1030, S1040, S1050‧ ‧ steps

1 is a block diagram of a variable gain low noise amplifying circuit in accordance with an embodiment of the present invention.

2 is a circuit diagram of a variable gain low noise amplifying circuit in accordance with an embodiment of the present invention.

3A is a waveform diagram of power intensity of a radio frequency input signal in accordance with an embodiment of the present invention.

3B is a driving waveform diagram of a switching signal according to an embodiment of the present invention.

4 is a simulation graph of a variable gain low noise amplifying circuit in a normal mode according to an embodiment of the present invention.

FIG. 5 is a circuit diagram of a variable gain low noise amplifying circuit in a shallow attenuation mode according to an embodiment of the present invention.

6 is a simulation graph of a variable gain low noise amplifying circuit in a shallow attenuation mode according to an embodiment of the present invention.

7 is a circuit diagram of a variable gain low noise amplifying circuit in a depth decay mode according to an embodiment of the invention.

FIG. 8 is a simulation diagram of a variable gain low noise amplifying circuit of a depth attenuation mode according to an embodiment of the present invention.

9 is a block diagram of a receiver in accordance with an embodiment of the present invention.

10 is a flow chart of a variable gain method in accordance with an embodiment of the present invention.

Various illustrative embodiments are described more fully hereinafter with reference to the accompanying drawings. However, the inventive concept may be embodied in many different forms and should not be construed as being limited to the illustrative embodiments set forth herein. Rather, these exemplary embodiments are provided so that this invention will be in the In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Similar numbers always indicate similar components.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, such elements are not limited by the terms. These terms are used to distinguish one element from another. Thus, a first element discussed below could be termed a second element without departing from the teachings of the inventive concept. As used herein, the term "and/or" includes any of the associated listed items and all combinations of one or more.

[Embodiment of Variable Gain Low Noise Amplifying Circuit]

Please refer to FIG. 1. FIG. 1 is a block diagram of a variable gain low noise amplifying circuit according to an embodiment of the invention. As shown in FIG. 1, the variable gain low noise amplifying circuit 100 includes a low noise amplifier 110, a bypass switch circuit 120, a first power supply circuit 130, a second power supply circuit 140, and a voltage dividing circuit 150. The bypass switch circuit 120 is connected in parallel to the low noise amplifier 110. The first power supply circuit 130 is connected to the low noise amplifier 110 and the bypass switch circuit 120. The second power supply circuit 140 is connected to the voltage dividing circuit 150. The voltage dividing circuit 150 is connected to the low noise amplifier 110 and the bypass switch circuit 120. The voltage dividing circuit 150 may be a circuit composed of a resistor. In this embodiment, the low noise amplifier 110 is generally used in a communication system and is configured to receive a radio frequency input signal RFIN, that is, its function is to be connected via an antenna. The weak RF input signal RFIN is amplified to a low noise figure. The bypass switch circuit 120 is configured to receive a switching signal GBS and determine an on or off state accordingly. The first power supply circuit 130 receives a first enable signal EN1 and outputs a first output voltage VOUT1, and the second power supply circuit 140 receives the second enable signal EN2 and outputs a second output voltage VOUT2 according to the first output voltage. VOUT1 is one of a system voltage or a ground voltage, and the second output voltage VOUT1 is one of a bias voltage or a ground voltage. The voltage dividing circuit 150 is configured to divide the second output voltage VOUT2 received by the voltage dividing circuit 150 and output a starting voltage VG to the low noise amplifier 110.

In wireless communication systems, the low noise amplifier in the receiver is responsible for amplifying the weak RF input signal and providing it to the back-end demodulation circuit. However, in some cases, if the receiver is very close to the signal source (ie, the base station), an excessively strong transmit signal is likely to cause saturation of the low noise amplifier, which in turn causes degradation of the receiver system. Accordingly, low noise amplifiers need to be capable of shallow attenuation or deep attenuation of these excessive RF input signals to maintain receiver system stability.

What will be taught next is to further explain the working principle of the variable gain low noise amplifying circuit 100.

Referring to FIG. 1 , in the embodiment, the variable gain low noise amplifying circuit 100 detects the power intensity of the RF input signal RFIN through the detector 160, and the detector 160 transmits the detection result RS to The controller 170, and then the controller 170 respectively transmits the first enable signal EN1, the second enable signal EN2 and the switch signal GBS to the corresponding first power circuit 130, the second power circuit 140 and the side according to the detection result RS. The circuit breaker circuit 120 controls its associated actions, thereby attenuating the RF input signal RFIN of different power intensities to varying degrees. Further, when the detector 160 detects that the power of the RF input signal RFIN is greater than the first power threshold, the variable gain low noise amplifier circuit 100 enters the "light attenuation mode" and the detector 160 will The detection result RS is transmitted to the controller 170, and then the controller 170 respectively transmits the first enable signal EN1, the second enable signal EN2 and the switch signal GBS according to the detection result RS. The first power circuit 130, the second power circuit 140 and the bypass switch circuit 120. The bypass switch circuit 120 is turned on according to the switch signal GBS and forms a first active resistor type, and the first power supply circuit 130 and the second power supply circuit 140 respectively according to the first enable signal EN1 and the second enable signal EN2 The off, that is, the output voltages VOUT1 and VOUT2 of the corresponding outputs are ground voltage or zero voltage, so that the low noise amplifier 110 is turned off. Therefore, when the RF input signal RFIN enters the input end of the variable gain low noise amplifier circuit 100, it will be converted to an RF output signal via the bypass switch circuit 120 to the output of the variable gain low noise amplifier circuit 100. The RFOUT is output to the next-stage circuit block (not shown), that is, the RF input signal RFIN is shallowly attenuated by the first active resistor formed by the bypass switch circuit 120.

On the other hand, when the detector 160 detects that the power of the RF input signal RFIN is greater than the second power threshold (the second power threshold is greater than the first power threshold), the variable gain low noise amplifier circuit 100 The "Deep Attenuation Mode" is entered and the detector 160 transmits the detection result RS to the controller 170. The controller 170 then transmits the first enable signal EN1 and the second enable signal according to the detection result RS. EN2 and the switching signal GBS correspond to the first power supply circuit 130, the second power circuit 140 and the bypass switch circuit 120, wherein the output voltages VOUT1 and VOUT2 output by the first power circuit 130 and the second power circuit 140 are still grounded . It should be noted that, at this time, the voltage level of the switching signal GBS transmitted by the controller 170 to the bypass switch circuit 120 is greater than the voltage level of the switching signal GBS in the "shallow attenuation mode", by increasing the voltage of the switching signal GBS. The level is used to slightly pull up the voltage level of the startup voltage VG to cause the low noise amplifier 110 to form a second active resistor. Therefore, when the RF input signal RFIN enters the input end of the variable gain low noise amplifier circuit 100, the RF input signal RFIN is formed by the first active resistor and the low noise amplifier 110 formed by the bypass switch circuit 120. The second active resistor is deeply attenuated, and outputs an RF output signal RFOUT to the next-stage circuit block (not shown) at the output of the variable-gain low-noise amplifier circuit 100.

In order to explain in more detail the operational flow of the variable gain low noise amplifying circuit 100 of the present invention, at least one of the following embodiments will be further developed. The description will be made in order for the three modes of the variable gain low noise amplifier circuit, "normal mode", "shallow attenuation mode" and "depth decay mode".

In the following various embodiments, portions different from the above-described embodiment of Fig. 1 will be described, and the remaining omitted portions are the same as those of the above-described embodiment of Fig. 1. In addition, for the sake of convenience, like reference numerals or numerals indicate similar elements.

[Another embodiment of variable gain low noise amplifying circuit]

Please refer to FIG. 2. FIG. 2 is a schematic circuit diagram of a variable gain low noise amplifying circuit according to an embodiment of the invention. The embodiment of FIG. 2 is to disclose the related operation of the variable gain low noise amplifier circuit in the "normal mode". Unlike the above embodiment of FIG. 1, the voltage dividing circuit 150 includes a first resistor R1 and a second resistor R2. The low noise amplifier 110 includes an output transistor Q. The bypass switch circuit 120 includes a switching transistor M. The variable gain low noise amplifier circuit 200 further includes a first inductor L1, a first capacitor C1, a second inductor L2, and a second capacitor C2. One end of the first resistor R1 is connected to the second power supply circuit 140. One end of the second resistor R2 is connected to the other end of the first resistor R1, and the other end of the second resistor R2 is connected to the ground voltage GND. The gate of the output transistor Q is connected to one end of the second resistor R2, and the source of the output transistor Q is connected to the ground voltage GND. One end of the first inductor L1 is connected to the RF input signal RFIN, and the other end of the first inductor L1 is connected to one end of the first capacitor C1, and the other end of the first capacitor C1 is connected to the gate of the output transistor Q. The gate of the switching transistor M receives the switching signal GBS and determines the on or off state according to this, and the source of the switching transistor M is connected to the gate of the output transistor Q. The drain of the switching transistor M is connected to one end of the second capacitor C2. The other end of the second capacitor C2 is connected to one end of the second inductor L2, and the other end of the second inductor L2 is connected to the first power source circuit 130.

What follows is to further explain the working principle of the variable gain low noise amplifying circuit 200 of the "normal mode".

Please refer to FIG. 2, FIG. 3A and FIG. 3B simultaneously. FIG. 3A is a waveform diagram of the power intensity of the radio frequency input signal according to an embodiment of the invention. 3B is a driving waveform diagram of a switching signal according to an embodiment of the present invention. Before time t1, when the detector 160 detects that the power intensity of the RF input signal RFIN is within a normal range, that is, the RF input signal RFIN If the power intensity is less than the first power threshold TH1, the variable gain low noise amplifier circuit 200 enters the "normal mode" and the detector 160 similarly transmits the detection result RS to the controller 170, and then the controller 170 The first enable signal EN1, the second enable signal EN2, and the switch signal GBS are respectively transmitted according to the detection result RS to the corresponding first power supply circuit 130, the second power supply circuit 140, and the switch transistor M. Accordingly, the switching transistor M is turned off or turned off according to the switching signal GBS of the low voltage level VL, and the first power supply circuit 130 outputs the system voltage as the first output voltage VOUT1 according to the first enabling signal EN1. The second power supply circuit 140 outputs the bias voltage as the second output voltage VOUT2 to the voltage dividing circuit 150 according to the second enable signal EN2, wherein the voltage dividing circuit 150 is formed by the first resistor R1 and the second resistor R2. The voltage dividing ratio further divides the bias voltage and outputs a starting voltage VG to the gate of the output transistor Q. At this time, the output transistor Q operates in the saturation region. Therefore, when the RF input signal RFIN enters the input end of the variable gain low noise amplifier circuit 200, the RF input signal RFIN is amplified by the output transistor Q of the low noise amplifier 110 to a low noise index RF output signal. RFOUT, to improve the communication system's signal-to-noise ratio (SNR), where the RF input signal RFIN is amplified along the signal path A and converted to the RF input signal RFOUT. Next, please refer to FIG. 4 at the same time. FIG. 4 is a simulation graph of a variable gain low noise amplifier circuit in a normal mode according to an embodiment of the present invention, wherein the horizontal axis represents the frequency (in GHz) and the vertical axis represents Gain (in dB). As can be seen from FIG. 4, the variable gain low noise amplifier circuit 200 in "normal mode" has a gain of about 18.157 dB at 2.45 GHz, which is very compatible with the communication standard of the low noise amplifier.

The next step is to further explain the working principle of the variable gain low noise amplifier circuit in the "light attenuation mode".

[Further embodiment of variable gain low noise amplifying circuit]

Please refer to FIG. 3A, FIG. 3B and FIG. 5 simultaneously. FIG. 5 is a circuit diagram of a variable gain low noise amplifying circuit in a shallow attenuation mode according to an embodiment of the invention. The embodiment of FIG. 5 discloses the related operation of the variable gain low noise amplifying circuit 500 in the "slight attenuation mode". Between time t1 and time t2, when the detector 160 detects the RF input signal RFIN When the power intensity is greater than the first power threshold TH1, that is, the power intensity of the RF input signal RFIN is between the first power threshold and the second power threshold TH2, the variable gain low noise amplifier circuit 500 enters The shallow attenuation mode and the detector 160 will also transmit the detection result RS to the controller 170, and then the controller 170 will respectively transmit the first enable signal EN1 and the second enable signal EN2 according to the detection result RS. The first power supply circuit 130, the second power supply circuit 140, and the switching transistor M corresponding to the switching signal GBS. The switching transistor M is turned on according to the switching signal GBS of the first high voltage level VH1 and enters the linear region to form a first active resistor (that is, the on-resistance of the switching transistor M), and the first power circuit 130 according to the first The coincidence signal EN1 outputs the ground voltage as the first output voltage VOUT1, and the second power supply circuit 140 outputs the ground voltage as the second output voltage VOUT2 to the voltage dividing circuit 150 according to the second enable signal EN2. The voltage circuit 150 further divides the ground voltage by a voltage dividing ratio formed by the first resistor R1 and the second resistor R2, and outputs a starting voltage VG to the gate of the output transistor Q. At this time, the output transistor Q is Work in the cut-off area. Therefore, when the RF input signal RFIN enters the input end of the variable gain low noise amplifier circuit 500, the RF input signal RFIN follows the signal path B and passes through the first active resistor (the switch transistor M entering the linear region) Forming) and the second capacitor C2 to the output of the variable gain low noise amplifier circuit 500, that is, the impedance effect of the first active resistor is shallowly attenuated by the impedance effect of the first active resistor to avoid the receiver system It is unstable due to excessive RF signal. Please refer to FIG. 6. FIG. 6 is a simulation diagram of a variable gain low noise amplifying circuit in a shallow attenuation mode according to an embodiment of the present invention, wherein the horizontal axis represents the frequency (in GHz) and the vertical axis represents Gain (in dB). As can be seen from Fig. 6, the gain of the variable gain low noise amplifier circuit 500 in the "slight attenuation mode" at 2.45 GHz is about - 3.056 dB.

[More Embodiment of Variable Gain Low-Noise Amplifying Circuit]

Please refer to FIG. 3A, FIG. 3B and FIG. 7. FIG. 7 is a schematic circuit diagram of a variable gain low noise amplifying circuit in a deep attenuation mode according to an embodiment of the invention. The embodiment of FIG. 7 is related to the disclosure of the variable gain low noise amplifier circuit 700 in the "depth decay mode". move. After the time t2, when the detector 160 detects that the power intensity of the RF input signal RFIN is greater than the second power threshold TH2, the variable gain low noise amplifier circuit 700 enters the "depth decay mode" and the detector 160 will also transmit the detection result RS to the controller 170, and then the controller 170 respectively transmits the first enable signal EN1, the second enable signal EN2 and the switch signal GBS to the corresponding first according to the detection result RS. The power circuit 130 has a second power circuit 140 and a switching transistor M. The switching transistor M continues to conduct according to the switching signal GBS of the second high voltage level VH2 and remains in the linear region to form a higher impedance first active resistor (ie, the on-resistance of the switching transistor M), wherein The second high voltage level VH2 is slightly larger than the first high voltage level VH1, which causes the switching transistor M to be turned on and enters the linear region, that is, the first active use of different voltage levels to achieve different resistance values. resistance. The first power supply circuit 130 continues to output the ground voltage as the first output voltage VOUT1 according to the first enable signal EN1, and the second power supply circuit 140 continues to use the bias voltage as the second output voltage VOUT2 according to the second enable signal EN2. And outputting to the voltage dividing circuit 150, wherein the voltage dividing circuit 150 further divides the ground voltage by a voltage dividing ratio formed by the first resistor R1 and the second resistor R2 and outputs a starting voltage VG to the output transistor Q. The gate. It is worth noting that because the gate of the switching transistor receives the switching signal GBS of the second high voltage level VH2, the gate voltage of the output transistor Q is raised, that is, the starting voltage VG is not The zero voltage and the voltage value of the startup voltage are such that the output transistor Q enters the linear region, thereby causing the output transistor Q to form a second active resistor (ie, the on-resistance of the output transistor Q). Briefly, in this embodiment, the attenuation amplitude of the RF input signal RFIN is deepened by the first active resistor and the second active resistor. Therefore, when the RF input signal RFIN enters the input end of the variable gain low noise amplifier circuit 700, the RF input signal RFIN follows the signal path C and passes through the first active resistor (the switch transistor M entering the linear region) The second capacitor C2 is formed to the output of the variable gain low noise amplifier circuit 700, and the RF input signal RFIN is subjected to the impedance effect of the first active resistor and the second active resistor and thus is greatly attenuated. Please refer to FIG. 8 at the same time, FIG. 8 is a depth according to an embodiment of the present invention. The analog curve of the variable gain low noise amplifier circuit in the decay mode, the horizontal axis represents the frequency (in GHz), and the vertical axis represents the gain (in dB). As can be seen from FIG. 8, the gain of the variable gain low noise amplifier circuit 700 in the "depth decay mode" at 2.45 GHz is about -13.188 dB.

In summary, the disclosure determines one of the "normal mode", "shallow attenuation mode" and "depth attenuation mode" by detecting the power intensity of the RF input signal, and attenuating the RF input signal through the impedance effect of the on-resistance. . It is worth mentioning that the disclosure not only has a "shallow attenuation mode" for attenuating the RF input signal by the first active resistor, but also has a first active resistor and a second active resistor to deepen the attenuation amplitude of the RF input signal. Depth attenuation mode".

[An embodiment of a receiver having a variable gain low noise amplifying circuit]

Please refer to FIG. 9. FIG. 9 is a block diagram of a receiver according to an embodiment of the present invention. The receiver 900 includes a variable gain low noise amplification circuit 910, a demodulation circuit 920, and a load 930. The demodulation circuit 920 is connected to the variable gain low noise amplification circuit 910, and the load 930 is connected to the demodulation circuit 920. The demodulation circuit 920 is configured to demodulate the RF output signal RFOUT and output the demodulation signal OUT to the load 930. The variable gain low noise amplifying circuit 910 may be one of the variable gain low noise amplifying circuits 100, 200, 500 and 700 in the above embodiment, and receive the RF input signal RFIN transmitted by the base station through the antenna. By detecting the power intensity of the RF input signal RFIN, it is determined to enter the "normal mode", "shallow attenuation mode" and "depth decay mode", and the RF input signal RFIN is attenuated by the impedance effect of the on-resistance.

[An embodiment of the variable gain method]

Please refer to FIG. 10. FIG. 10 is a flowchart of a variable gain method according to an embodiment of the present invention. The method in this example can be implemented in the portable electronic device of the variable gain low noise amplifying circuit shown in FIG. 1, FIG. 2, FIG. 5 or FIG. 7, so please refer to FIG. 1, FIG. 2 and FIG. 5 or Figure 7 to understand. The variable gain method includes the steps of: detecting an RF input signal (step S1010). It is determined whether the power of the radio frequency input signal is greater than the first power threshold (step S1020). If the power of the RF input signal is greater than the first power threshold The value continues to determine whether the power of the RF input signal is greater than the second power threshold (step S1030). If the power of the RF input signal is between the first and second power thresholds, the RF input signal is slightly attenuated by the first active resistor (step S1040). If the power of the RF input signal is greater than the second power threshold, the RF input signal is deeply attenuated by the first active resistor and the second active resistor (step S1050).

The details of the steps of the variable gain method of the variable gain low noise amplifying circuit have been described in detail in the above embodiments of FIGS. 1 to 8 and will not be described herein.

It should be noted that the steps of the embodiment of FIG. 10 are merely for convenience of description, and the embodiments of the present invention do not use the steps of the steps as a limitation of the embodiments of the present invention.

[Possible effects of the examples]

In summary, the variable gain low noise amplifying circuit and the variable gain method and receiver thereof according to the embodiments of the present invention can determine the normal mode and the shallow state by detecting the power intensity of the RF input signal. One of the degree decay mode and the "depth decay mode", and the RF input signal is attenuated differently by the impedance effect of the on-resistance. Accordingly, the effect of protecting the back-end circuit of the receiver is achieved.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

200‧‧‧Variable Gain Low Noise Amplifier Circuit

110‧‧‧Low noise amplifier

120‧‧‧ Bypass Switch Circuit

130‧‧‧First power circuit

140‧‧‧Second power circuit

150‧‧‧voltage circuit

160‧‧‧Detector

170‧‧‧ Controller

A‧‧‧Signal Path

C1‧‧‧first capacitor

C2‧‧‧second capacitor

EN1‧‧‧First enable signal

EN2‧‧‧Secondary enable signal

GND‧‧‧ Grounding voltage

GBS‧‧‧ switch signal

L1‧‧‧first inductance

L2‧‧‧second inductance

M‧‧‧Switching transistor

Q‧‧‧Output transistor

R1‧‧‧first resistance

R2‧‧‧second resistance

RFIN‧‧‧RF input signal

RFOUT‧‧‧RF output signal

RS‧‧‧Detection results

VG‧‧‧ start voltage

VOUT1‧‧‧ first output voltage

VOUT2‧‧‧second output voltage

Claims (10)

A variable gain low noise amplifying circuit comprising: a low noise amplifier receiving an RF input signal; a bypass switching circuit connected in parallel to the low noise amplifier, the bypass switch circuit receiving a switching signal and determining accordingly Turning on or off; a first power circuit connected to the low noise amplifier and the bypass switch circuit, the first power circuit receiving a first enable signal and outputting a first output voltage according to the same; a second power circuit connected to the low noise amplifier and the bypass switch circuit, the second power circuit receiving a second enable signal and outputting a second output voltage according to the power output signal, wherein the power of the RF input signal is greater than one When the first power threshold is set, the bypass switch circuit is turned on and formed into a first active resistor, and the first and second power circuits are respectively turned off according to the first and second enable signals to enable the The low noise amplifier is turned off, and the RF input signal is lightly attenuated by the first active resistor; when the power of the RF input signal is greater than a second power threshold, Voltage level of the switching signal so that the LNA is formed a second active resistance, depth attenuate the RF input signal through the first and the second active resistance. The variable gain low noise amplifying circuit of claim 1, further comprising: a first resistor connected to the second power supply circuit at one end to receive the second output voltage; and a second resistor One end of the first resistor is connected to the low noise amplifier, and the other end is connected to a ground voltage. The first and the second resistors form a voltage dividing circuit, and the second output voltage is divided. The startup voltage is then output to the low noise amplifier, and the second power threshold is greater than the first power threshold. The variable gain low noise amplifying circuit of claim 2, wherein the first output voltage is one of a system voltage or the ground voltage, and the second output voltage is a bias voltage or the One of the grounding voltages. The variable gain low noise amplifier circuit of claim 2, wherein the low noise amplifier comprises: an output transistor, the gate is connected to the RF input signal and the startup voltage, and the source is connected to the source a grounding voltage, the drain is connected to the first power circuit to receive the first output voltage and output an RF output signal, wherein the output transistor operating in the saturation region is used to amplify the RF input signal and operates in a linear The output transistor of the region is the second active resistor. The variable gain low noise amplifying circuit of claim 4, wherein the bypass switch circuit comprises: a switching transistor, wherein the gate receives the switching signal and determines an on or off state according to the source thereof a pole connected to the gate of the output transistor, the drain is connected to the first power circuit to receive the first output voltage, wherein the switch transistor adjusts the resistance of the first active resistor according to the voltage level of the switch signal When the power of the RF input signal is greater than the first power threshold, the switch transistor operates in the linear region according to the voltage level of the switch signal to form the first active resistor, and the first and the first The second power circuit is respectively turned off according to the first and the second enable signals to turn off the output transistor, and then the RF input signal is lightly attenuated by the first active resistor. The variable gain low noise amplifier circuit of claim 5, wherein when the power of the RF input signal is greater than a second power threshold, the voltage level of the switch signal is increased to make the switch The first active resistor is formed by the crystal operating in the linear region, thereby increasing the startup voltage to turn on the output transistor and operating the output transistor in the linear region to form the second active resistor, thereby transmitting the first and the second The second active resistor attenuates the RF input signal in depth. A receiver comprising: a variable gain low noise amplifying circuit as claimed in claim 1 for receiving an RF input signal and outputting a RF output signal; and a demodulation circuit connecting the variable gain a low noise amplifying circuit for demodulating the RF output signal and outputting a demodulated signal; and a load connected to the demodulation circuit, the load receiving the demodulated signal. The receiver of claim 7, wherein the variable gain low noise amplifying circuit further comprises a first resistor, one end of which is connected to the second power circuit to receive the second output voltage; and a second a resistor, one end of which is connected to the other end of the first resistor and the low noise amplifier, and the other end of which is connected to a ground voltage, wherein the first and the second resistors form a voltage dividing circuit, and the second output voltage is And dividing a voltage to output a starting voltage to the low noise amplifier, and the second power threshold is greater than the first power threshold, wherein the low noise amplifier comprises an output transistor, and the gate is connected to the RF input signal And the starting voltage, the source is connected to the ground voltage, the drain is connected to the first power circuit to receive the first output voltage and output an RF output signal, wherein the output transistor operating in the saturation region is used to The RF input signal is amplified, and the output transistor operating in the linear region is the second active resistor, and the bypass switch circuit includes a switching transistor, and the gate is connected Receiving the switch signal and determining an on or off state according to which the source is connected to the gate of the output transistor, and the drain is connected to the first power circuit to receive the first output voltage, wherein the switch transistor is according to the switch The voltage level of the signal is adjusted to the resistance value of the first active resistor. When the power of the RF input signal is greater than the first power threshold, the switching transistor operates in a linear manner according to the voltage level of the switching signal. Forming the first active resistor, and the first and second power supply circuits are respectively turned off according to the first and second enable signals to turn off the output transistor, and then pass through the first active resistor to be shallow Attenuates the RF input signal. A variable gain method comprising: Detecting an RF input signal; determining whether the power of the RF input signal is greater than a first power threshold; if the power of the RF input signal is greater than the first power threshold, determining whether the power of the RF input signal is greater than one a second power threshold; if the power of the RF input signal is between the first and second power thresholds, the RF input signal is shallowly attenuated by a first active resistor; if the power of the RF input signal And greater than the second power threshold value, the RF input signal is deeply attenuated by the first active resistor and a second active resistor, wherein the variable gain method is used for the variable gain as described in claim 1 A low noise amplifying circuit or a receiver as described in claim 7 of the patent application. The variable gain method of claim 9, wherein the variable gain low noise amplifying circuit further comprises a first resistor connected to the second power supply circuit at one end to receive the second output voltage; a second resistor, one end of which is connected to the other end of the first resistor and the low noise amplifier, and the other end of which is connected to a ground voltage, wherein the first and the second resistors form a voltage dividing circuit, and the second The output voltage is divided to output a starting voltage to the low noise amplifier, and the second power threshold is greater than the first power threshold, wherein the low noise amplifier comprises an output transistor, and the gate is connected to the RF The input signal and the starting voltage are connected to the ground voltage of the source, and the drain is connected to the first power circuit to receive the first output voltage and output an RF output signal, wherein the output transistor operating in the saturation region is used for Amplifying the radio frequency input signal, and the output transistor operating in the linear region is the second active resistor, and the bypass switch circuit includes a switching transistor, The gate receives the switch signal and determines an on or off state according to which the source is connected to the gate of the output transistor, and the drain is connected to the first power circuit to receive the first output voltage, wherein the switch transistor is The voltage level of the switch signal adjusts the resistance value of the first active resistor, When the power of the RF input signal is greater than the first power threshold, the switch transistor operates in the linear region according to the voltage level of the switch signal to form the first active resistor, and the first and the first The two power supply circuits are respectively turned off according to the first and the second enable signals to turn off the output transistor, and then the RF input signal is lightly attenuated by the first active resistor.