Amplitude limiting circuit, radio frequency signal receiving circuit, and electronic device
By incorporating an active amplitude limiting circuit in the radio frequency signal receiving circuit and utilizing multiple amplitude limiting techniques, the problem of low-noise amplifiers easily saturating under high-power signals is solved, thereby improving the receiver's anti-blocking performance and signal quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- HYTERA COMM CORP
- Filing Date
- 2025-07-10
- Publication Date
- 2026-07-07
AI Technical Summary
Existing amplitude limiting circuits are insufficient for limiting high-power, strong signals, causing low-noise amplifiers to easily enter saturation, affecting their linearity and receiver performance.
An active amplitude limiting circuit is set in the radio frequency signal receiving circuit. The signal is limited multiple times by the first limiting unit, the second limiting unit and the third limiting unit to reduce the signal amplitude received by the low noise amplifier and maintain its stable operation.
It improves the anti-saturation capability of the low-noise amplifier, enhances the anti-blocking performance of the RF signal receiving circuit in strong signal environments, and maintains the stable operation and signal quality of the receiver.
Smart Images
Figure CN224473287U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of communication technology, and in particular to amplitude limiting circuits, radio frequency signal receiving circuits, and electronic devices. Background Technology
[0002] An amplitude limiting circuit is a circuit that can flatten the amplitude of a signal voltage within a defined range; it is also called a limiter or clipper. Existing amplitude limiting circuits are usually passive limiter circuits, which can only limit weak signals with low power. They are insufficient in limiting strong signals with high power (including strong interference signals), which affects the performance of low-noise amplifiers. Utility Model Content
[0003] This application provides an amplitude limiting circuit, a radio frequency signal receiving circuit, and an electronic device. By setting an active amplitude limiting circuit between the output terminal of the first bandpass filter and the input terminal of the low noise amplifier, the signal output by the first bandpass filter can be limited by the active amplitude limiting circuit, reducing the possibility that the low noise amplifier will quickly enter saturation due to the excessive amplitude of the signal received by the low noise amplifier, reducing the impact on the linear performance of the low noise amplifier, and maintaining the stable operation of the low noise amplifier.
[0004] To address the aforementioned technical problems, this application provides an amplitude limiting circuit. The amplitude limiting circuit is disposed between the output terminal of a first bandpass filter and the input terminal of a low-noise amplifier in a radio frequency signal receiving circuit. The amplitude limiting circuit includes a first limiting unit, a first terminal of which is coupled to the output terminal of the first bandpass filter, a second terminal of which is coupled to a current source, and a third terminal of which is coupled to the input terminal of the low-noise amplifier. The first limiting unit is used to limit the amplitude of the signal output by the first bandpass filter.
[0005] To address the aforementioned technical problems, this application also provides a radio frequency signal receiving circuit, which includes a first bandpass filter, a low-noise amplifier, and the aforementioned amplitude limiting circuit.
[0006] In order to solve the above-mentioned technical problems, this application provides an electronic device, which includes the above-mentioned amplitude limiting circuit or the above-mentioned radio frequency signal receiving circuit.
[0007] Unlike existing technologies, the amplitude limiting circuit, radio frequency signal receiving circuit, and electronic device provided in some embodiments of this application can limit the amplitude of the signal output by the first bandpass filter by setting an active amplitude limiting circuit coupled between the output terminal of the first bandpass filter and the input terminal of the low noise amplifier. This reduces the possibility that the low noise amplifier will quickly enter saturation due to the excessive amplitude of the signal received by the low noise amplifier, reduces the impact on the linear performance of the low noise amplifier, and maintains the stable operation of the low noise amplifier. Attached Figure Description
[0008] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:
[0009] Figure 1 This is a schematic diagram of an embodiment of the radio frequency signal receiving circuit and amplitude limiting circuit provided in this application;
[0010] Figure 2 This is a schematic diagram of an embodiment of the amplitude limiting circuit provided in this application;
[0011] Figure 3 yes Figure 2 A schematic diagram of the structure of an embodiment of the first limiting unit;
[0012] Figure 4 yes Figure 2 A schematic diagram of the structure of an embodiment of the second limiting unit;
[0013] Figure 5 This is a schematic diagram of an embodiment of the amplitude limiting circuit provided in this application;
[0014] Figure 6 yes Figure 5 A schematic diagram of the structure of an embodiment of the third limiting unit;
[0015] Figure 7 This is a schematic diagram of an embodiment of the amplitude limiting circuit provided in this application;
[0016] Figure 8 This is a schematic diagram of an embodiment of the radio frequency signal receiving circuit provided in this application;
[0017] Figure 9 This is a schematic diagram of an embodiment of the radio frequency signal receiving circuit provided in this application;
[0018] Figure 10 This is a schematic diagram of an embodiment of the radio frequency signal receiving circuit provided in this application;
[0019] Figure 11 yes Figure 10 A schematic diagram of one embodiment of the demodulation circuit;
[0020] Figure 12 This is a schematic diagram of an embodiment of the amplitude limiting circuit and radio frequency signal receiving circuit provided in this application;
[0021] Figure 13 This is a schematic diagram of the receiver provided in this application;
[0022] Figure 14 This is a schematic diagram of the structure of an embodiment of the electronic device provided in this application;
[0023] Figure 15 This is a schematic diagram of the structure of an embodiment of the electronic device provided in this application;
[0024] Figure 16 This is a schematic diagram of the structure of an embodiment of the electronic device provided in this application. Detailed Implementation
[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0026] Common radio frequency (RF) signal transceiver circuits typically include an RF signal receiving circuit and an RF signal transmitting circuit. These two circuits share some components, such as a shared antenna for transmitting and receiving signals.
[0027] Taking the example of using a shared antenna to receive signals from a transmitter and send signals to a receiver, since the antenna is not an ideal component, the energy input from the transmitter to the antenna cannot be completely radiated; some energy will be input to the receiver. When the antenna's standing wave ratio is poor, this reflected energy is very large, even forming total reflection. In this case, the receiver's low-noise amplifier will burn out due to overpower. Furthermore, when receiving strong signals (especially strong interference signals), if the received signal amplitude is too large, the low-noise amplifier will quickly saturate, thus affecting the linearity of the low-noise amplifier and impacting the receiver's performance.
[0028] To address the issue of strong interference signals blocking receiver linearity and even affecting the performance of normal equipment (such as walkie-talkies), this application provides an amplitude limiting circuit, an RF signal receiving circuit, a receiver, and electronic equipment. This circuit can limit the strong signal at the front end of the low-noise amplifier to the maximum extent possible. While maintaining the stable operation of the low-noise amplifier, the amplifier operates normally in the linear region, thus enhancing its anti-blocking performance in strong signal environments.
[0029] According to some embodiments of this application, please refer to Figures 1 to 6 , Figure 1 This is a schematic diagram of an embodiment of the radio frequency signal receiving circuit and amplitude limiting circuit provided in this application; Figure 2 This is a schematic diagram of an embodiment of the amplitude limiting circuit provided in this application; Figure 3 yes Figure 2 A schematic diagram of the structure of an embodiment of the first limiting unit; Figure 4 yes Figure 2 A schematic diagram of the structure of an embodiment of the second limiting unit; Figure 5 This is a schematic diagram of an embodiment of the amplitude limiting circuit provided in this application; Figure 6 yes Figure 5 A schematic diagram of the structure of an embodiment of the third limiting unit; Figure 7 This is a schematic diagram of an embodiment of the amplitude limiting circuit provided in this application.
[0030] According to some embodiments of this application, such as Figures 1 to 7 As shown, the radio frequency signal receiving circuit 200 includes a first bandpass filter 201 and a low noise amplifier 202, and an amplitude limiting circuit 100 is provided between the first bandpass filter 201 and the low noise amplifier 202.
[0031] Specifically, the amplitude limiting circuit 100 is disposed between the output terminal of the first bandpass filter 201 and the input terminal of the low noise amplifier 202 in the radio frequency signal receiving circuit 200, and one end of the amplitude limiting circuit 100 is coupled to the current source 10.
[0032] The amplitude limiting circuit 100 includes a first limiting unit 101, wherein a first end of the first limiting unit 101 is coupled to the output end of the first bandpass filter 201, a second end of the first limiting unit 101 is coupled to the current source 10, and a third end of the first limiting unit 101 is coupled to the input end of the low noise amplifier 202. The first limiting unit 101 is used to limit the signal output by the first bandpass filter 201.
[0033] The current source 10 can supply power to the amplitude limiting circuit 100, specifically to the first limiting unit 101. The voltage values output by the current source 10 include, but are not limited to, 3.3V, 4.5V, and 5V.
[0034] The frequency band filtered by the first bandpass filter 201 is determined according to the actual situation.
[0035] The low-noise amplifier 202 can be a small-signal linear amplifier. It amplifies the received signal and outputs the amplified signal. The amplification factor of the low-noise amplifier 202 can be dynamically adjusted according to actual conditions.
[0036] The signal output by the first bandpass filter 201 includes a main signal and an interference signal. The main signal is the signal transmitted during communication, and the interference signal is generated during the transmission of the main signal. It may be generated due to component performance loss or due to interference from other signals.
[0037] In some embodiments, the limiting capability of the amplitude limiting circuit 100 is positively correlated with the power of the interference signal, as shown in the table below:
[0038] Interference signal power (dBm) Limiting capability (dBm) X+3Y WT X+2Y W-2T X+Y W-3T X W-4T
[0039] Where Y > T, and Y is uncorrelated with T.
[0040] Taking X as 20dBm, Y as 10dBm, T as 12dBm, and W as 100dBm as an example, when the power of the interference signal is 20, the limiting capability of the amplitude limiting circuit 100 is 52dBm; when the power of the interference signal is 30, the limiting capability of the amplitude limiting circuit 100 is 64dBm; when the power of the interference signal is 40, the limiting capability of the amplitude limiting circuit 100 is 76dBm; and when the power of the interference signal is 50, the limiting capability of the amplitude limiting circuit 100 is 88dBm.
[0041] In some embodiments, the limiting capability of the amplitude limiting circuit 100 is positively correlated with its resistance to signal blocking. The better the limiting capability of the amplitude limiting circuit 100, the better its resistance to signal blocking.
[0042] The amplitude limiting circuit 100 provided in this embodiment is disposed between the output terminal of the first bandpass filter 201 and the input terminal of the low noise amplifier 202 in the radio frequency signal receiving circuit 200. The active amplitude limiting circuit 100 can limit the signal output by the first bandpass filter 201, reduce the possibility that the low noise amplifier 202 will quickly enter the saturation state due to the excessive amplitude of the signal received by the low noise amplifier 202, reduce the impact on the linear performance of the low noise amplifier 202, and maintain the stable operation of the low noise amplifier 202.
[0043] The amplitude limiting circuit 100 provided in this embodiment is disposed between the output terminal of the first bandpass filter 201 and the input terminal of the low noise amplifier 202. It can enhance the amplitude limiting capability of the front-end component of the low noise amplifier 202 in the radio frequency signal receiving circuit 200, thereby improving the anti-strong signal blocking interference performance of the low noise amplifier 202 and the back-end component. It can solve the problem of insufficient margin of anti-strong signal blocking performance of the radio frequency signal receiving circuit 200 under strong signal interference environment.
[0044] According to some embodiments of this application, such as Figure 2 and Figure 7 As shown, the amplitude limiting circuit 100 includes a first limiting unit 101 and a second limiting unit 102.
[0045] The input terminal of the second limiting unit 102 is coupled to the third terminal of the first limiting unit 101, and the output terminal of the second limiting unit 102 is coupled to the input terminal of the low noise amplifier 202. The second limiting unit 102 is used to limit the signal output by the first limiting unit 101.
[0046] The current source 10 is coupled to the first limiting unit 101, and the first limiting unit 101 is coupled to the second limiting unit 102. The current source 10 can supply power not only to the first limiting unit 101, but also to the second limiting unit 102.
[0047] In this embodiment, the first limiting unit 101 can perform a first limiting on the signal output by the first bandpass filter 201 under the power supply of the current source 10, and the second limiting unit 102 can perform a second limiting on the signal output by the first limiting unit 101 under the power supply of the current source 10. The two limiting operations reduce the amplitude of the signal received by the low-noise amplifier 202, reducing the possibility that the low-noise amplifier 202 may quickly enter saturation due to excessively large received signal amplitude, thus minimizing the impact on the linear performance of the low-noise amplifier 202 and ensuring its continuous and stable operation.
[0048] According to some embodiments of this application, such as Figure 3 and Figure 7 As shown, the first limiting unit 101 includes a first capacitor 1011 and a first resistor 1012.
[0049] The first terminal of the first capacitor 1011 is coupled to the output terminal of the first bandpass filter 201, and the second terminal of the first capacitor 1011 is coupled to the input terminal of the second limiting unit 102. The first terminal of the first resistor 1012 is coupled to the current source 10, and the second terminal of the first resistor 1012 is coupled to the second terminal of the first capacitor 1011.
[0050] The first resistor 1012 serves as an isolation element. The resistance value of the first resistor 1012 includes, but is not limited to, 500Ω, 600Ω, 800Ω, and 1000Ω.
[0051] The capacitance of the first capacitor 1011 can be determined based on actual conditions, and is not limited here.
[0052] According to some embodiments of this application, such as Figure 4 and Figure 7 As shown, the second limiting unit 102 includes a first diode 1021, a second diode 1022, a second resistor 1023, and a second capacitor 1024.
[0053] In this configuration, the anode of the first diode 1021 is coupled to the second terminal of the first capacitor 1011. The cathode of the second diode 1022 is coupled to the cathode of the first diode 1021, and the anode of the second diode 1022 is grounded. The first terminal of the second resistor 1023 is coupled to the cathode of the first diode 1021, and the second terminal of the second resistor 1023 is grounded. The first terminal of the second capacitor 1024 is coupled to the cathode of the first diode 1021, and the second terminal of the second capacitor 1024 is coupled to the input terminal of the low-noise amplifier 202.
[0054] The second resistor 1023 serves as an isolation element. The resistance value of the second resistor 1023 includes, but is not limited to, 500Ω, 600Ω, 800Ω, and 1000Ω.
[0055] In some embodiments, the resistance value of the first resistor 1012 is the same as the resistance value of the second resistor 1023.
[0056] In some embodiments, such as Figure 4 and Figure 7 As shown, the first diode 1021 and the second diode 1022 are rectifier diodes.
[0057] According to some embodiments of this application, such as Figure 5 and Figure 7 As shown, the amplitude limiting circuit 100 also includes a first limiting unit 101, a second limiting unit 102, and a third limiting unit 103.
[0058] The structures of the first limiting unit 101 and the second limiting unit 102 can be found in [reference needed]. Figures 3 to 4 This will not be elaborated upon here.
[0059] The third limiting unit 103 is disposed between the output end of the first bandpass filter 201 and the first limiting unit 101, and the third limiting unit 103 is used to limit the signal output by the first bandpass filter 201.
[0060] The third limiting unit 103 can limit the amplitude of small and medium power interference signals to improve the blocking interference performance of strong signals.
[0061] In this embodiment, the third limiting unit 103 can perform a first limiting on the signal output by the first bandpass filter 201. Under the power supply of the current source 10, the first limiting unit 101 can perform a second limiting on the signal output by the first bandpass filter 201. Under the power supply of the current source 10, the second limiting unit 102 can perform a third limiting on the signal output by the first limiting unit 101. This three-stage limiting reduces the amplitude of the signal received by the low-noise amplifier 202, reducing the possibility that the low-noise amplifier 202 might quickly enter saturation due to excessively large received signal amplitude, thus minimizing the impact on the linear performance of the low-noise amplifier 202 and ensuring its continuous and stable operation.
[0062] According to some embodiments of this application, such as Figure 6 and Figure 7 As shown, the third limiting unit 103 includes a third diode 1031 and a fourth diode 1032.
[0063] The negative terminal of the third diode 1031 is coupled to the output terminal of the first bandpass filter 201, and the positive terminal of the third diode 1031 is grounded. The positive terminal of the fourth diode 1032 is coupled to the output terminal of the first bandpass filter 201, and the negative terminal of the fourth diode 1032 is grounded.
[0064] In some embodiments, such as Figure 6 and Figure 7 As shown, the third diode 1031 and the fourth diode 1032 are Zener diodes.
[0065] It is understood that the current source 10 can supply power to the first limiting unit 101 and the second limiting unit 102, while the third limiting unit 103 is a passive limiting unit, which has the limiting function without the need for the current source 10 to supply power.
[0066] The amplitude limiting circuit 100 of this embodiment includes a first limiting unit 101, a second limiting unit 102, and a third limiting unit 103. When the amplitude limiting circuit 100 filters the signal output from the first bandpass filter 201, the passive third limiting unit 103 performs the first limiting, which can limit weak signals (including interference signals) of medium and low power to improve the strong signal blocking interference performance. Then, the signal is further limited by the first limiting unit 101 and the second limiting unit 102, which can limit the amplitude of strong signals (including strong interference signals) of high power, thereby improving the linearity of the low noise amplifier 202 and the components connected to the output terminal of the low noise amplifier 202, reducing the possibility of increased noise floor, and ensuring that the low noise amplifier 202 and the components connected to the output terminal of the low noise amplifier 202 maintain normal operation.
[0067] It is understandable that since the third limiting unit 103 has already limited the amplitude of the low-to-medium power interference signal, the first limiting unit 101 and the second limiting unit 102 will not limit the amplitude of the low-to-medium power interference signal, but will limit the amplitude of the high-power, high-amplitude strong interference signal.
[0068] For example, the third limiting unit 103 limits weak signals (including main signals and interference signals) with an amplitude of less than 5dBm, while the first limiting unit 101 and the second limiting unit 102 can limit strong signals (including main signals and interference signals) with an amplitude of more than 10dBm.
[0069] According to some embodiments of this application, please refer to Figures 8 to 12 , Figure 8 This is a schematic diagram of an embodiment of the radio frequency signal receiving circuit provided in this application; Figure 9 This is a schematic diagram of an embodiment of the radio frequency signal receiving circuit provided in this application; Figure 10 This is a schematic diagram of an embodiment of the radio frequency signal receiving circuit provided in this application; Figure 11 yes Figure 10 A schematic diagram of one embodiment of the demodulation circuit; Figure 12 This is a schematic diagram of an embodiment of the amplitude limiting circuit and radio frequency signal receiving circuit provided in this application.
[0070] According to some embodiments of this application, such as Figure 8 As shown, the radio frequency signal receiving circuit 200 includes a first bandpass filter 201, a low noise amplifier 202, and an amplitude limiting circuit 100 of any of the above embodiments.
[0071] According to some embodiments of this application, such as Figure 9 and Figure 12As shown, the radio frequency signal receiving circuit 200 also includes a low-pass filter 203 and a switching circuit 204.
[0072] The low-pass filter 203 is coupled to the antenna 20 and is used to filter the radio frequency signal received by the antenna 20.
[0073] The first terminal of the switch switching circuit 204 is coupled to the output terminal of the low-pass filter 203, and the second and third terminals of the switch switching circuit 204 are coupled to the first band-pass filter 201. The first band-pass filter 201 is used to filter the signal sent by the low-pass filter 203 when the first and second terminals of the switch switching circuit 204 are turned on.
[0074] The antenna 20 is used to receive the radio frequency signal transmitted by the transmitter, which is a modulated signal.
[0075] The switching circuit 204 is used to select different paths according to the power of the filtered RF signal output by the low-pass filter 203, so as to control the power of the filtered RF signal.
[0076] In some embodiments, when the power of the signal output by the low-pass filter 203 is less than or equal to a preset power, the first and second terminals of the switch switching circuit 204 are turned on. When the power of the signal output by the low-pass filter 203 is greater than the preset power, the first and second terminals of the switch switching circuit 204 are turned off. The preset power can be determined according to actual conditions and is not limited here.
[0077] In some embodiments, the switch switching circuit 204 is a transmit / receive switch. Specifically, the switch switching circuit 204 includes three terminals. When the first and second terminals of the switch switching circuit 204 are turned on, the switch switching circuit 204 is used to turn on the antenna 20 to receive the radio frequency signal transmitted by the transmitter, and at this time the switch switching circuit 204 is used as a receive switch; when the first and third terminals of the switch switching circuit 204 are turned on, the switch switching circuit 204 is used to turn on the signal transmitted to the receiver via the antenna 20, and at this time the switch switching circuit 204 is used as a transmit switch.
[0078] In some embodiments, the switch switching circuit 204 includes a first switch and a second switch. A first terminal of the first switch is coupled to the output terminal of a low-pass filter 203, and a second terminal of the first switch is coupled to the input terminal of a first band-pass filter 201. A first terminal of the second switch is coupled to the output terminal of the low-pass filter 203, and a second terminal of the second switch is coupled to the input terminal of the first band-pass filter 201. When the first and second terminals of the first switch are on and the first and second terminals of the second switch are off, the switch switching circuit 204 is used to enable the antenna 20 to receive the radio frequency signal transmitted by the transmitter, i.e., to enable the signal transmitted by the low-pass filter 203. When the first and second terminals of the second switch are on and the first and second terminals of the first switch are off, the switch switching circuit 204 is used to enable the signal transmitted to the receiver via the antenna 20.
[0079] According to some embodiments of this application, such as Figure 10 and Figure 12 As shown, the radio frequency signal receiving circuit 200 also includes a second bandpass filter 205, a mixer 206, and a demodulation circuit 207.
[0080] The second bandpass filter 205 is coupled to the output of the low-noise amplifier 202, and is used to filter the signal output by the low-noise amplifier 202.
[0081] Mixer 206 is coupled to second bandpass filter 205 and is used to mix the signal output from second bandpass filter 205 with local oscillation signal.
[0082] The demodulation circuit 207 is coupled to the mixer 206. The demodulation circuit 207 is used to demodulate the signal output by the mixer 206 to obtain the baseband signal.
[0083] The mixer 206 mixes the signal output from the second bandpass filter 205 with the local oscillation signal to obtain a down-converted signal.
[0084] The local oscillation signal input to mixer 206 can be generated by an oscillator, and the power of the local oscillation signal is equal to the power of the radio frequency signal. The two input terminals of mixer 206 are connected to the oscillator and the second bandpass filter 205, respectively. Mixer 206 can multiply the signal output from the second bandpass filter 205 and the local oscillation signal to obtain the mixed signal.
[0085] The demodulation circuit 207 is coupled to the mixer 206. The demodulation circuit 207 can demodulate the down-converted signal after mixing to obtain the baseband signal, so that the power of the interference signal in the output signal of the demodulation circuit 207 is less than the power of the noise floor. The noise floor includes, but is not limited to, white noise.
[0086] According to some embodiments of this application, such as Figure 11 and Figure 12 As shown, the demodulation circuit 207 includes an intermediate frequency filter 301 and an intermediate frequency amplifier 302.
[0087] The intermediate frequency filter 301 is coupled to the mixer 206 and is used to filter the signal output by the mixer 206.
[0088] Intermediate frequency amplifier 302 is coupled to intermediate frequency filter 301. Intermediate frequency amplifier 302 is used to amplify the signal output by intermediate frequency filter 301 to obtain baseband signal.
[0089] The intermediate frequency filter 301 is coupled to the mixer 206, and the intermediate frequency filter 301 can filter out multiple interference signals mixed in the signal output by the mixer 206.
[0090] The amplitude limiting circuit 100 provided in this embodiment is disposed between the output terminal of the first bandpass filter 201 and the input terminal of the low noise amplifier 202 in the radio frequency signal receiving circuit 200. It can enhance the limiting capability of the front end of the low noise amplifier 202 in the radio frequency signal receiving circuit 200, thereby improving the anti-strong signal blocking interference performance of the low noise amplifier 202 and the back-end components (such as the second bandpass filter 205, mixer 206 and demodulation circuit 207). It can solve the problem of insufficient margin of anti-strong signal blocking performance of the radio frequency signal receiving circuit 200 in the strong signal interference environment.
[0091] In one application scenario, the amplitude limiting circuit 100 and the RF signal receiving circuit 200 limit the amplitude process as follows: the antenna 20 receives the RF signal, the RF signal passes through the low-pass filter 203, the low-pass filter 203 filters out out-of-band interference signals higher than the first frequency range, the signal output by the low-pass filter 203 passes through the switching circuit 204 and is then input to the first band-pass filter 201, the first band-pass filter 201 further narrows the signal, at this time most of the out-of-band interference signals have been filtered out in the signal output by the first band-pass filter 201, but if some signals with frequencies close to the main signal are not filtered out and are directly input into the low-noise amplifier 202, the low-noise amplifier 202 will saturate, which will cause the signal to be compressed and distorted, and the signal quality received by the receiver will be poor. Therefore, an amplitude limiting circuit 100 is provided between the output of the first bandpass filter 201 and the input of the low-noise amplifier 202, so that the signal output from the first bandpass filter 201 is further limited by the passive third limiting unit 103, and then further limited by the first limiting unit 101 and the second limiting unit 102, so that the amplitudes of the signal input to the low-noise amplifier 202 and the signal output from the low-noise amplifier 202 are low, thereby avoiding linear saturation of the low-noise amplifier 202, thus ensuring the quality of the signal received by the receiver and improving the receiver's anti-large signal blocking interference performance.
[0092] According to some embodiments of this application, such as Figure 13 As shown, Figure 13 This is a schematic diagram of the receiver provided in this application. The receiver 300 includes the radio frequency signal receiving circuit 200 of any of the above embodiments, which will not be described in detail here.
[0093] In some embodiments, receiver 300 is a superheterodyne receiver or a zero-IF receiver.
[0094] According to some embodiments of this application, such as Figures 14 to 16 As shown, Figures 14 to 16 These are schematic diagrams of an embodiment of the electronic device provided in this application.
[0095] like Figure 14 As shown, the electronic device 400 includes the amplitude limiting circuit 100 of any of the above embodiments.
[0096] like Figure 15 As shown, the electronic device 400 includes the radio frequency signal receiving circuit 200 of any of the above embodiments.
[0097] like Figure 16 As shown, the electronic device 400 includes the receiver 300 of any of the above embodiments.
[0098] In some embodiments, the electronic device 400 further includes a transmitter for generating and transmitting radio frequency signals so that the antenna 20 can receive them.
[0099] In some embodiments, the electronic device 400 includes a processor and a memory. The processor involved in this application may be referred to as a CPU (Central Processing Unit), which may be an integrated circuit chip, or a general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component.
[0100] In some embodiments, the electronic device 400 includes, but is not limited to, a walkie-talkie or a mobile phone.
[0101] In summary, the amplitude limiting circuit 100, radio frequency signal receiving circuit 200, receiver 300, and electronic device 400 provided in some embodiments of this application improve the terminal's anti-strong signal jamming interference performance by enhancing the radio frequency front-end's amplitude limiting capability. This solves the problem of insufficient margin in the anti-strong signal jamming performance of superheterodyne / zero IF receivers under strong signal interference environments, thereby improving the anti-jamming interference performance of superheterodyne / zero IF receivers.
[0102] Furthermore, the amplitude limiting circuit 100 and the radio frequency signal receiving circuit 200 have simple circuit structures, small size, and low cost. Compared with the radio frequency switch attenuator scheme in related technologies, the technical solution of this application can save costs.
[0103] Furthermore, the amplitude limiting circuit 100 and the radio frequency signal receiving circuit 200 of this application can not only maintain the sensitivity under weak signals, but also fill the gap in the improvement measures for strong signal anti-blocking interference, and improve the terminal's extreme near-end receiving sensitivity, thereby improving the user's actual experience of the terminal and enhancing the product's competitiveness in the market.
[0104] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.
Claims
1. An amplitude limiting circuit, characterized in that, The amplitude limiting circuit is disposed between the output terminal of the first bandpass filter and the input terminal of the low-noise amplifier in the radio frequency signal receiving circuit, and the amplitude limiting circuit includes: The first limiting unit has a first terminal coupled to the output terminal of the first bandpass filter, a second terminal coupled to a current source, and a third terminal coupled to the input terminal of the low-noise amplifier. The first limiting unit is used to limit the signal output by the first bandpass filter.
2. The amplitude limiting circuit according to claim 1, characterized in that, The amplitude limiting circuit also includes: The second limiting unit has its input terminal coupled to the third terminal of the first limiting unit and its output terminal coupled to the input terminal of the low-noise amplifier. The second limiting unit is used to limit the signal output by the first limiting unit.
3. The amplitude limiting circuit according to claim 2, characterized in that, The first limiting unit includes: A first capacitor, the first terminal of which is coupled to the output terminal of the first bandpass filter, and the second terminal of which is coupled to the input terminal of the second limiting unit; A first resistor, the first end of which is coupled to the current source, and the second end of which is coupled to the second terminal of the first capacitor.
4. The amplitude limiting circuit according to claim 3, characterized in that, The second limiting unit includes: The first diode, the positive terminal of the first diode being coupled to the second terminal of the first capacitor; The second diode has its cathode coupled to the cathode of the first diode, and its anode grounded. The second resistor has its first end coupled to the negative terminal of the first diode and its second end grounded. The second capacitor has its first terminal coupled to the negative terminal of the first diode, and its second terminal coupled to the input terminal of the low-noise amplifier.
5. The amplitude limiting circuit according to claim 4, characterized in that, The first diode and the second diode are rectifier diodes.
6. The amplitude limiting circuit according to claim 1, characterized in that, The amplitude limiting circuit also includes: A third limiting unit is disposed between the output of the first bandpass filter and the first limiting unit, and the third limiting unit is used to limit the signal output by the first bandpass filter.
7. The amplitude limiting circuit according to claim 6, characterized in that, The third limiting unit includes: The third diode, the negative terminal of which is coupled to the output terminal of the first bandpass filter, and the positive terminal of which is grounded; The fourth diode has its positive terminal coupled to the output terminal of the first bandpass filter, and its negative terminal grounded.
8. The amplitude limiting circuit according to claim 7, characterized in that, The third diode and the fourth diode are Zener diodes.
9. A radio frequency signal receiving circuit, characterized in that, It includes a first bandpass filter, a low-noise amplifier, and an amplitude limiting circuit as described in any one of claims 1-8.
10. An electronic device, characterized in that, It includes the amplitude limiting circuit as described in any one of claims 1-8, or the radio frequency signal receiving circuit as described in claim 9.