Signal conditioning circuit and communication device
By using at least two stages of low-noise power amplifier in the signal regulation circuit, especially the design of the first stage as an emitter follower, combined with matching and filter, the reverse isolation and power consumption problems are solved, and high isolation and low noise transmission of the signal regulation circuit are achieved.
Patent Information
- Application Number
- CN202422106617.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-28
- Publication Date
- 2025-08-15
- Estimated Expiration
- 2034-08-28
AI Technical Summary
The existing signal regulating circuits have severely deteriorated when the reverse isolation is met, and the power consumption is difficult to optimize and reduce, especially when using a two-stage cascade buffer, the overall power consumption is too high.
A buffer circuit of at least two stages of low-noise power amplifier is adopted, wherein the first stage is an emitter follower, which reduces the reverse signal interference through a multi-stage low-noise power amplifier, and optimizes signal transmission with a matching circuit and filter to reduce the impact of reverse transmission on the voltage-controlled oscillator.
It improves the signal isolation of the signal adjustment circuit, reduces the remote noise and power consumption, and enhances the flexibility of the signal adjustment circuit and the accuracy of signal transmission.
Smart Images
Figure CN223231144U_ABST
Abstract
Description
Technical Field
[0001] The present application is applied to the technical field of electronic communications, and in particular relates to a signal conditioning circuit and a communication device. Background Art
[0002] Signal conditioning circuits are an integral part of electronic systems. Through a series of processing measures, such as conversion, protection, filtering, and isolation, they convert field input status signals into logic signals that can be received by computers or other devices. Buffers are often used during signal transmission to isolate the reverse transmission of the signal from affecting the input signal.
[0003] However, in the commonly used buffer solutions currently available, under certain power consumption and output amplitude requirements, the noise figure of a single-stage high reverse isolation integrated device is large, which can easily lead to severe deterioration of far-end phase noise and is difficult to optimize and reduce power consumption. If a two-stage cascaded buffer is used, the overall power consumption will far exceed that of a single-stage integrated device to meet the saturation working condition required by the final stage. Utility Model Content
[0004] The present application provides a signal conditioning circuit to solve the problem in the prior art that far-end phase noise deteriorates seriously when the buffer meets the reverse isolation requirement.
[0005] To solve the above technical problems, the present application provides a signal conditioning circuit, comprising: a voltage-controlled oscillator; a buffer circuit, the buffer circuit comprising at least two stages of low-noise power amplifiers cascaded with each other; wherein the input end of the first-stage low-noise power amplifier is connected to the output end of the voltage-controlled oscillator, the output end of the first-stage low-noise power amplifier is connected to the input end of the next-stage low-noise power amplifier, and the output end of the last-stage low-noise power amplifier is used to connect to the signal input end; the first-stage low-noise power amplifier is an emitter follower.
[0006] Among them, the emitter follower includes: a first transistor, the base of the first transistor is coupled to the output end of the voltage-controlled oscillator, and the emitter of the first transistor is coupled to the input end of the next-stage low-noise power amplifier; a first bias circuit is coupled to the DC power supply, the collector of the first transistor and the base of the first transistor respectively, and is used to provide a static voltage for the first transistor; a first emitter resistor, one end of which is coupled to the emitter of the first transistor and the other end is grounded.
[0007] The first bias circuit includes: a base bias circuit, one end of which is coupled to the base of the first transistor and the other end is coupled to the collector of the first transistor; a collector resistor, one end of which is coupled to the collector of the first transistor and the other end is coupled to the DC power supply.
[0008] The base bias circuit includes: a first voltage-dividing resistor, one end of which is coupled to the base of the first transistor and the other end is coupled to the collector of the first transistor; a second voltage-dividing resistor, one end of which is coupled to the base of the first transistor and the other end is grounded.
[0009] The buffer circuit includes two stages of cascaded low-noise power amplifiers, with the final stage of the low-noise power amplifier including: a second transistor, the base of which is coupled to the output of the first-stage low-noise power amplifier, and the emitter of which is connected to the signal input; a second bias circuit, coupled to a DC power supply, the collector of the second transistor, and the base of the second transistor, respectively, for providing a static voltage for the second transistor; and a second emitter resistor, one end of which is coupled to the emitter of the second transistor and the other end of which is grounded. The signal isolation of the second transistor is lower than that of the first transistor.
[0010] Wherein, at least one stage of the low noise power amplifiers in the cascade of the first stage low noise power amplifiers is a buffer.
[0011] The signal conditioning circuit further includes a matching circuit, one end of which is connected to the output of the previous low-noise power amplifier and the other end is connected to the input of the next low-noise power amplifier to match the impedance between adjacent low-noise power amplifiers.
[0012] The matching circuit includes: a first capacitor, the first capacitor is connected to the output end of the previous stage low-noise power amplifier, a second capacitor, the second capacitor is connected to the input end of the next stage low-noise power amplifier, a first matching resistor is connected between the first capacitor and the second capacitor, and both ends of the first matching resistor are connected to a second matching resistor connected to the ground.
[0013] The signal conditioning circuit further includes: a filter, the input end of the filter is coupled to the output end of the last-stage low-noise power amplifier, and the output end of the filter is used to connect to the signal input end; an attenuation circuit, coupled between the first-stage low-noise power amplifier and the voltage-controlled oscillator.
[0014] To solve the above problems, the present application also provides a communication device, which includes any one of the above signal conditioning circuits.
[0015] The beneficial effects of the present application are: different from the existing technology, the present application couples a buffer circuit of at least two stages of low-noise power amplifiers to the output end of the voltage-controlled oscillator, which can reduce the reverse signal and effectively prevent the reverse-transmitted signal from interfering with the signal output by the voltage-controlled oscillator, thereby improving the signal isolation of the signal conditioning circuit, and setting the first-stage low-noise power amplifier as an emitter follower can improve the signal isolation of the signal conditioning circuit while ensuring far-end noise and power consumption. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is a structural block diagram of an embodiment of the signal conditioning circuit of the present application;
[0017] Figure 2 This is a structural block diagram of an embodiment of a buffer of the present application;
[0018] Figure 3 This is a structural block diagram of the connection between the multi-stage low-noise power amplifier and the matching circuit of the present application;
[0019] Figure 4 It is a structural diagram of the matching circuit of the present application;
[0020] Figure 5 This is a structural block diagram of another embodiment of the signal conditioning circuit of the present application. DETAILED DESCRIPTION
[0021] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.
[0022] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.
[0023] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.
[0024] See also Figure 1 , Figure 1 This is a structural block diagram of an embodiment of a signal conditioning circuit provided by the present application.
[0025] The present application provides a signal conditioning circuit, such as Figure 1As shown, a signal conditioning circuit of this embodiment includes: a voltage controlled oscillator 10 and a buffer circuit 20. The buffer circuit 20 includes at least two stages of low noise power amplifiers cascaded with each other. The two stages of low noise power amplifiers are connected in sequence. After the signal conditioning circuit outputs the signal, the signal will be transmitted back to the voltage controlled oscillator 10, thereby interfering with the signal output by the voltage controlled oscillator 10. When the signal is transmitted in reverse, the signal is reduced by the two stages of low noise power amplifiers, thereby preventing the reversely transmitted signal from interfering with the signal output by the voltage controlled oscillator 10. Figure 3 As shown, in this embodiment, the buffer circuit 20 can be provided with multiple stages of low-noise power amplifiers, for example, three or four stages, to reduce the reverse transmission signal to a level that does not interfere with the signal output by the voltage-controlled oscillator 10. This is not specifically limited in this application. The input of the first-stage low-noise power amplifier 30 is connected to the output of the voltage-controlled oscillator 10. The output of the first-stage low-noise power amplifier 30 is connected to the input of the next-stage low-noise power amplifier 80. The output of the last-stage low-noise power amplifier 40 is connected to the signal input. The first-stage low-noise power amplifier 30 is an emitter follower.
[0026] In an alternative embodiment, the output of the voltage-controlled oscillator 10 is coupled to two low-noise power amplifiers, namely a first-stage low-noise power amplifier 30 and a final-stage low-noise power amplifier 40. Specifically, the output of the voltage-controlled oscillator 10 is connected to the input of the first-stage low-noise power amplifier 30, the output of the first-stage low-noise power amplifier 30 is connected to the input of the final-stage low-noise power amplifier 40, and the output of the final-stage low-noise power amplifier 40 is connected to the signal input. When the voltage-controlled oscillator 10 outputs a signal, the signal is transmitted to the signal input via the two-stage low-noise power amplifier. After receiving the signal transmitted by the final-stage low-noise power amplifier 40, the signal input transmits the transmitted signal in the reverse direction. The reverse-transmitted signal is attenuated by the two-stage low-noise power amplifier to prevent interference with the signal transmitted by the voltage-controlled oscillator 10. Specifically, during reverse transmission, the reverse signal is attenuated by the final-stage low-noise power amplifier 40 and further attenuated by the first-stage low-noise power amplifier 30, minimizing the impact of the reverse-transmitted signal on the signal transmitted by the voltage-controlled oscillator 10.
[0027] In a specific application scenario, the signal conditioning circuit is applied to a walkie-talkie. When the first user transmits a voice signal, the voice signal is transmitted through the voltage-controlled oscillator 10 and transmitted to the second user through a two-stage low-power amplifier. The transmitted voice signal will be transmitted in reverse to interfere with the voice signal transmitted by the first user, such as when a heavy tone occurs. When the voice signal is transmitted in reverse, the reverse signal is reduced by the two-stage low-noise power amplifier, so that the transmitted voice signal has little impact on the first user when it is transmitted in reverse.
[0028] In this embodiment, the first-stage low-noise power amplifier 30 is an emitter follower. During signal transmission, the phase noise at the far end is reduced, ensuring the accuracy of signal transmission. Similarly, the use of an emitter follower can meet the signal amplitude and power consumption requirements. That is, under the premise of ensuring the far-end noise and power consumption, the first-stage low-noise power amplifier 30 can be set as an emitter follower, and combined with the last-stage low-noise power amplifier 40, the isolation of the signal conditioning circuit can be effectively improved. Under the action of the first-stage low-noise power amplifier 30, the last-stage low-noise power amplifier 40 can only have the function of amplifying the signal. Therefore, when cascading, the last-stage low-noise power amplifier 40 only needs to select a suitable model according to the signal amplitude and power consumption, so that the signal conditioning circuit has more choices and improves the flexibility of the signal conditioning circuit.
[0029] In the above embodiment, by coupling the buffer circuit 20 of at least two stages of low-noise power amplifiers to the output end of the voltage-controlled oscillator 10, the reverse signal can be reduced, effectively preventing the reversely transmitted signal from interfering with the signal output by the voltage-controlled oscillator 10, thereby improving the signal isolation of the signal conditioning circuit, and setting the first-stage low-noise power amplifier 30 as an emitter follower can improve the signal isolation of the signal conditioning circuit while ensuring far-end noise and power consumption. At the same time, the last-stage low-noise power amplifier 40 only needs to select a suitable model according to the signal amplitude and power consumption, thereby improving the flexibility of the signal conditioning circuit.
[0030] In an optional embodiment, if Figure 2As shown, the emitter follower includes: a first transistor 301, the base of the first transistor 301 is coupled to the output end of the voltage-controlled oscillator 10, and the emitter of the first transistor 301 is coupled to the next-stage low-noise power amplifier 80. The first bias circuit 302 is coupled to the DC power supply, the collector of the first transistor 301 and the base of the first transistor 301, respectively, for providing a static voltage for the first transistor 301. The first emitter resistor 303 has one end coupled to the emitter of the first transistor 301 and the other end grounded. The first bias circuit 302 also includes a base bias circuit 304, one end coupled to the base of the first transistor 301 and the other end coupled to the collector of the first transistor 301. The collector resistor 305 has one end coupled to the collector of the first transistor 301 and the other end coupled to the DC power supply. As shown, Figure 2 As shown, the base bias circuit 304 includes a first voltage-dividing resistor 306 and a second voltage-dividing resistor 307. The first voltage-dividing resistor 306 has one end coupled to the base of the first transistor 301 and the other end coupled to the collector of the first transistor 301. The second voltage-dividing resistor 307 has one end coupled to the base of the first transistor 301 and the other end grounded. In other words, the common end of the first voltage-dividing resistor 306 and the second voltage-dividing resistor 307 is coupled to the base of the first transistor 301.
[0031] In this embodiment, the first stage low noise power amplifier 30 is an emitter follower, that is, the input resistance R i for:
[0032] R i =r be +(1+β)R E
[0033] Among them, r be is the base resistance, β is the amplification factor of the transistor, R E is the emitter resistor.
[0034] In practical applications, the bias resistor R B and load R L The input resistance R i At this time, the input resistance R i for:
[0035] R i =R B ‖[r be +(1+β)(R E ‖R L )]
[0036] The input resistance of the common emitter single tube amplifier circuit is: R i =R B ‖r beIt can be seen that the input resistance of the emitter follower is much higher than the input resistance of the common-emitter single-tube amplifier circuit, that is, the input resistance of the emitter follower is high. In practical applications, when the input end of the emitter follower is coupled to the output end of the voltage-controlled oscillator 10, the current flowing through the emitter follower from the output signal source of the voltage-controlled oscillator 10 is small, so that the loss of the emitter follower to the signal source output by the voltage-controlled oscillator 10 is reduced.
[0037] Furthermore, the output resistance R O for:
[0038]
[0039] Among them, U O is the output voltage of the emitter follower when no load is applied, U L The connected load R L The output voltage of the emitter follower.
[0040] If we consider the internal resistance of the signal source R S , the output resistance R of the emitter follower O The output resistance R of the common emitter single tube amplifier is O ≈R C Much lower. That is, the higher the amplification factor of the transistor, the lower the output resistance R O The smaller.
[0041] In this embodiment, the collector of the transistor is used as a common terminal for input and output, the base serves as the input terminal, and the emitter serves as the output terminal. When the voltage-controlled oscillator 10 outputs a signal to the base of the transistor, the emitter of the transistor outputs the signal, and the collector also outputs the signal. Since the phase of the output signal is the same as the input signal, the output voltage is in phase with the input voltage. Furthermore, since the collector of the transistor is a common terminal, the current of the input signal flows through the collector of the transistor, and the current of the output signal flows through the emitter of the transistor, that is, the emitter follower has the characteristics of high input resistance and low output resistance.
[0042] In an optional embodiment, if Figure 1 and Figure 2As shown, the buffer circuit 20 includes two cascaded low-noise power amplifiers. The final low-noise power amplifier 40 includes a second transistor 801, the base of which is coupled to the output of the first low-noise power amplifier 30, and the emitter of which is connected to the signal input. Specifically, the base of the second transistor 801 is coupled to the emitter of the first transistor 301. A second bias circuit 802 is coupled to a DC power supply, the collector of the second transistor 801, and the base of the second transistor 801, respectively, to provide a static voltage for the second transistor 801. A second emitter resistor 803 has one end coupled to the emitter of the second transistor 801 and the other end grounded. In this embodiment, the final low-noise power amplifier 40 is the next-stage low-noise power amplifier 80 of the first low-noise power amplifier 30, which amplifies the signal from the voltage-controlled oscillator 10. The output signal of the voltage-controlled oscillator 10 passes through the first-stage low-noise power amplifier 30 and is output by the next-stage low-noise power amplifier 80, transmitting the signal to the signal input terminal. During reverse signal transmission, since the first-stage low-noise power amplifier 30 is an emitter follower, it cannot meet the high isolation requirement. The next-stage low-noise power amplifier 80 and the first-stage low-noise power amplifier 30 work together to isolate the reverse signal, thereby meeting the reverse isolation requirement and preventing the reverse signal from interfering with the output signal of the voltage-controlled oscillator 10. Among them, the first-stage low-noise power amplifier 30 can use 2SC3356 as an emitter follower, or other common-collector emitter followers, such as 2SC3355. The next-stage low-noise power amplifier 80 can use BFU760 as an amplifier, or other signal amplifiers, which are not specifically limited in this application. In this embodiment, the second bias circuit 802 also includes a second base bias circuit 804 and a second collector resistor 805. One end of the second base bias circuit 804 is coupled to the base of the second transistor 801, and the other end is coupled to the collector of the second transistor 801. One end of the second collector resistor 805 is coupled to the collector of the second transistor 801, and the other end is coupled to a DC power supply. The second base bias circuit 804 also includes a voltage divider resistor, similar to the base bias circuit 304 described above, and will not be further described here.
[0043] In an optional embodiment, at least one of the cascaded low-noise power amplifiers of the first-stage low-noise power amplifier 30 serves as a buffer. That is, one of the cascaded low-noise power amplifiers at the output of the first-stage low-noise power amplifier 30 serves as a buffer. Taking a three-stage low-noise power amplifier as the buffer circuit 20 as an example, for example, the low-noise power amplifier between the first-stage low-noise power amplifier 30 and the final-stage low-noise power amplifier 40 serves as a buffer, or the final-stage low-noise power amplifier 40 serves as a buffer. When the final-stage low-noise power amplifier 40 serves as a buffer, the previous low-noise power amplifier of the final-stage low-noise power amplifier 40 serves as a signal amplifier. Similarly, when the buffer is provided between the first-stage low-noise power amplifier 30 and the final-stage low-noise power amplifier 40, the final-stage low-noise power amplifier 40 serves as a signal amplifier. Specifically, when the voltage-controlled oscillator 10 outputs a signal and transmits it to the signal input terminal through multiple low-noise power amplifiers, the signal will propagate in the reverse direction. The multi-stage low-noise power amplifiers and the buffer attenuate the reverse signal, thereby preventing the reverse signal from interfering with the signal transmitted by the voltage-controlled oscillator 10. By configuring at least one stage of the cascaded low-noise power amplifiers of the first-stage low-noise power amplifier 30 as a buffer, the isolation of the signal conditioning circuit can be effectively improved.
[0044] In other embodiments, due to the relatively high power consumption of the buffer, the cascaded low-noise power amplifier of the first-stage low-noise power amplifier 30 may not be provided with a buffer. Specifically, in practical applications, low power consumption is also an indicator that cannot be ignored while satisfying the signal reverse isolation. That is, a low-noise power amplifier is cascaded after the first-stage low-noise power amplifier. When the transmitted signal is transmitted in the reverse direction, the cascaded low-noise power amplifier can effectively reduce the reversely transmitted signal. That is, while ensuring the reverse isolation, the power consumption of the signal conditioning circuit can be effectively reduced. Preferably, a two-stage low-noise power amplifier is provided in the buffer circuit. The first-stage low-noise power amplifier 30 is provided as an emitter follower, and the second-stage low-noise power amplifier has the function of amplifying the signal. The combined effect of the two-stage low-noise power amplifier can effectively meet the reverse isolation requirement. The second-stage low-noise power amplifier can be selected according to user needs and power consumption, thereby reducing the power consumption of the signal conditioning circuit while satisfying the reverse isolation.
[0045] In an optional embodiment, the signal conditioning circuit further includes a matching circuit 50, one end of which is connected to the output of the previous stage low noise power amplifier, and the other end is connected to the input of the next stage low noise power amplifier 80, so as to match the impedance between adjacent low noise power amplifiers. Figure 4As shown, the matching circuit 50 includes: a first capacitor 501, a second capacitor 502, a first matching resistor 503 and a second matching resistor 504, the first capacitor 501 is connected to the output end of the previous stage low noise power amplifier, the second capacitor 502 is connected to the input end of the next stage low noise power amplifier 80, the first matching resistor 503 is arranged between the first capacitor 501 and the second capacitor 502, and both ends of the first matching resistor 503 are connected to the second matching resistor 504 connected to the ground, wherein the first matching resistor 503 and the second matching resistor 504 can be set as an inductor, or one of them is set as an inductor, which is not specifically limited in this application. In this embodiment, the inter-stage matching circuit 50 is used to enable the circuit to transmit the output signal of the previous stage low noise power amplifier to the next stage low noise power amplifier 80, that is, the output impedance of the previous stage low noise power amplifier is made the same as the output impedance of the next stage low noise power amplifier 80 through the matching circuit 50, thereby reducing the signal transmission loss between the two stages of low noise power amplifiers.
[0046] In an optional embodiment, if Figure 5 As shown, the signal conditioning circuit also includes: a filter 60, the input end of the filter 60 is coupled to the output end of the last-stage low-noise power amplifier 40, and the output end of the filter 60 is used to connect to the input end of the signal. The filter 60 is connected to the output end of the last-stage low-noise power amplifier 40. After the voltage-controlled oscillator circuit outputs the signal, it is transmitted to the filter 60 through multiple stages of low-noise power amplifiers, further reducing the phase noise of the signal. Furthermore, an attenuation circuit 70 is coupled between the first-stage low-noise power amplifier 30 and the voltage-controlled oscillator 10. The signal output by the voltage-controlled oscillator 10 is amplified and the noise in the signal is reduced. This allows the subsequent multiple stages of low-noise power amplifiers to process the signal.
[0047] In a specific application scenario, the signal conditioning circuit further includes a feedback circuit (not shown), which includes a chip (not shown). The feedback circuit is connected to the output end of the voltage-controlled oscillator 10 to transmit the feedback signal to the chip. The chip can be a PLL (phase-locked loop) chip. That is, the output signal of the voltage-controlled oscillator 10 is divided into two paths. One path is the feedback signal, which is input into the chip through the feedback circuit. The other path is the output signal, which is input into the first-stage low-noise power amplifier 30 as an oscillation signal.
[0048] Through the above-mentioned method, the present application can reduce the reverse signal by coupling at least two stages of low-noise power amplifier buffer circuits 20 to the output end of the voltage-controlled oscillator 10, effectively preventing the reverse-transmitted signal from interfering with the signal output by the voltage-controlled oscillator 10. By providing the first bias circuit 302, the first transistor 301, and the first emitter resistor 303 in the first-stage low-noise power amplifier 30, the current flowing through the emitter follower of the output signal source of the voltage-controlled oscillator 10 is small, thereby reducing the loss of the emitter follower to the signal source output by the voltage-controlled oscillator 10. By providing the last-stage low-noise power amplifier 40 as an amplifier, combined with the first-stage low-noise power amplifier 30, the reverse signal can be isolated, thereby improving the isolation of the signal conditioning circuit. By providing at least one stage as a buffer in the low-noise power amplifier cascaded with the first-stage low-noise power amplifier 30, the isolation of the signal conditioning circuit can be effectively improved. By providing a matching circuit 50 between the two low-noise power amplifier stages, the output impedance of the previous low-noise power amplifier can be made equal to the output impedance of the next low-noise power amplifier 80, thereby reducing signal transmission losses between the two low-noise power amplifier stages. By coupling a filter 60 to the output of the final low-noise power amplifier 40, noise in the signal can be eliminated. By coupling an attenuation circuit 70 between the first low-noise power amplifier 30 and the voltage-controlled oscillator 10, the signal output by the voltage-controlled oscillator 10 can be amplified and noise in the signal reduced.
[0049] The present application also provides a communication device, which includes: a signal conditioning circuit, which is arranged in the communication device, and the signal conditioning circuit is the signal conditioning circuit of any of the above embodiments.
[0050] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.
Claims
1. A signal conditioning circuit, characterized in that: The signal conditioning circuit comprises: Voltage controlled oscillator; A buffer circuit, the buffer circuit comprising at least two stages of cascaded low-noise power amplifiers; wherein the input end of the first-stage low-noise power amplifier is connected to the output end of the voltage-controlled oscillator, the output end of the first-stage low-noise power amplifier is connected to the input end of the next-stage low-noise power amplifier, and the output end of the last-stage low-noise power amplifier is connected to the signal input end; The first-stage low-noise power amplifier is an emitter follower.
2. The signal conditioning circuit according to claim 1, wherein: The emitter follower comprises: a first transistor, wherein a base of the first transistor is coupled to the output end of the voltage-controlled oscillator, and an emitter of the first transistor is coupled to the input end of the next-stage low-noise power amplifier; a first bias circuit, coupled to a DC power supply, a collector of the first transistor, and a base of the first transistor, respectively, for providing a static voltage for the first transistor; A first emitter resistor has one end coupled to the emitter of the first transistor and the other end grounded.
3. The signal conditioning circuit according to claim 2, wherein: The first bias circuit comprises: a base bias circuit, one end of which is coupled to the base of the first transistor, and the other end of which is coupled to the collector of the first transistor; A collector resistor has one end coupled to the collector of the first transistor and the other end coupled to a DC power supply.
4. The signal conditioning circuit according to claim 3, wherein: The base bias circuit comprises: a first voltage-dividing resistor, one end of which is coupled to the base of the first transistor, and the other end of which is coupled to the collector of the first transistor; A second voltage-dividing resistor has one end coupled to the base of the first transistor and the other end grounded.
5. The signal conditioning circuit according to any one of claims 2 to 4, characterized in that: The buffer circuit includes two stages of cascaded low-noise power amplifiers, and the last stage of the low-noise power amplifier includes: a second transistor, wherein a base of the second transistor is coupled to the output end of the first-stage low-noise power amplifier, and an emitter of the second transistor is connected to the signal input end; a second bias circuit, coupled to the DC power supply, the collector of the second transistor, and the base of the second transistor, respectively, for providing a static voltage for the second transistor; a second emitter resistor, one end of which is coupled to the emitter of the second transistor and the other end of which is grounded; The signal isolation of the second transistor is smaller than the signal isolation of the first transistor.
6. The signal conditioning circuit according to any one of claims 1 to 4, characterized in that: At least one stage of the low-noise power amplifiers in the cascade of the first-stage low-noise power amplifiers is a buffer.
7. The signal conditioning circuit according to claim 1, wherein: The signal conditioning circuit further includes a matching circuit, one end of which is connected to the output of the previous stage low noise power amplifier and the other end is connected to the input of the next stage low noise power amplifier to match the impedance between adjacent low noise power amplifiers.
8. The signal conditioning circuit according to claim 7, wherein: The matching circuit includes: a first capacitor, the first capacitor is connected to the output end of the previous stage low-noise power amplifier, a second capacitor, the second capacitor is connected to the input end of the next stage low-noise power amplifier, a first matching resistor is connected between the first capacitor and the second capacitor, and both ends of the first matching resistor are connected to a second matching resistor connected to the ground.
9. The signal conditioning circuit according to claim 1, wherein: The signal conditioning circuit further includes: A filter, wherein the input end of the filter is coupled to the output end of the last-stage low-noise power amplifier, and the output end of the filter is used to connect to the signal input end; The attenuation circuit is coupled between the first-stage low-noise power amplifier and the voltage-controlled oscillator.
10. A communication device, characterized in that: The communication device comprises the signal conditioning circuit according to any one of claims 1 to 9.