Transmitting circuit with switchable output modes
By designing a transmitter circuit with switchable output modes, and using a Class C amplifier and digitally controlled attenuator to shut off the input signal in high-power mode, the problem of transmitter noise leakage to the receiver was solved, achieving noise-free delay leakage and efficient transmission.
Patent Information
- Application Number
- CN202520044877.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-09
- Publication Date
- 2025-12-26
- Estimated Expiration
- 2035-01-09
AI Technical Summary
In the prior art, during the receiving cycle, the amplifier is still powered on, causing noise to leak to the receiver, affecting the receiver's performance, especially preventing it from working properly at high power output.
Design a transmitter circuit with switchable output mode. Utilize a Class C amplifier to shut off the input signal in high-power mode. Combine this with a digitally controlled attenuator and mode switching control circuit to achieve noise-free delay and leakage in high-power mode. In contrast, use traditional methods to shut off the amplifier drain power supply in low-power mode.
It achieves noise-free delay leakage at high power output, ensuring that the receiver receives information without delay and improving transmission efficiency.
Smart Images
Figure CN223729742U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model belongs to the transmitter technical field, more particularly to a kind of output mode switchable transmitting circuit. BACKGROUND
[0002] In engineering applications, a transmitter needs to be designed, which works in L band, with output bandwidth of 265MHz, input signal power of-13dBm~ -7dBm, and external system requirements that when output signal power is +45dBm, if the transmission period ends, the receiver at the other end can immediately start receiving signal; when output signal power is +25dBm~ +35dBm, if the transmission period ends, the receiver at the other end can start receiving signal after a delay of 1us. In fact, the transmitter and receiver of the system are connected through a circulator, sharing the same antenna, as shown in FIG. 1. When the system works in the receiving period, the transmitter is closed, but the amplifier inside the transmitter is still in the state of power-on, and the static current still exists, and the temperature noise will still be amplified through the transmitter. Therefore, when the noise power is comparable to the sensitivity of the receiver, the useful signal will be submerged by noise, causing the performance of the receiver to decline. Figure 1
[0003] When the output is high power, the minimum gain of the signal is +45dBm-(-7dBm) = 52dB, and the bandwidth of the system is 265MHz, so when the transceiver noise factor is not considered, the system noise floor is -174dBm+10lg(BW) = -174dBm+10lg(265×
[0004] 106) = -89.77dBm (where -174dBm is the thermal noise power at +25℃), which will be amplified by the transmitter, with an output power of not less than -89.77dBm+52dB. After isolation by the circulator, there is still -89.77dBm+32dB of noise leakage to the receiver, which is greater than the receiving noise floor by 32dB, and the receiver cannot work normally.
[0005] When the transmitter outputs low power, the receiver can receive with a delay, so the power supply of the amplifier inside the transmitter can be controlled to prevent the transmission noise from entering the receiver, as shown in FIG. 2. When the drain power supply of the amplifier inside the transmitter is turned off, the amplifier stops working completely, and at this time the transmitter not only has no gain, but also introduces insertion loss, so the noise leaked to the receiver does not affect the receiving sensitivity. But this method is ineffective for high-power transmission, and in fact, turning off the power supply of the amplifier will have a tail phenomenon, as shown in FIG. 3. Figure 2 Figure 3 As shown. This is due to the power amplifier feed loop delay, there is still Δt time in the receiving period of transmission leakage, this time the receiver can not work properly. Utility model content
[0006] The utility model discloses to the transmitter in prior art works in receiving period, transmitter shutdown signal, but due to the amplifier inside transmitter still be in the electrified state, will lead to the problem of useful signal being drowned by noise, make receiver performance decline, provide a kind of output mode switchable transmitting circuit as Figure 4 As shown, the output mode switchable transmitting circuit includes a power supply module, the power supply module supplies power to the transmitting circuit (not shown in the figure), and further includes a radio frequency signal input port, a first attenuator, a first amplifier, a second attenuator, a first filter, a second amplifier, a first digital attenuator, a first digital attenuator control signal input end, a second digital attenuator, a second digital attenuator control signal input end, a temperature compensation attenuator, a third amplifier, a first isolator, a first drain modulator, a second drain modulator, a drain modulator control signal input end, a NOT gate, a control signal input end, a radio frequency signal output port, a seventh resistor, an eighth resistor and a mode switching control circuit.
[0007] The radio frequency signal input port, the first attenuator, the first amplifier, the second attenuator, the first filter and the second amplifier are connected in sequence, the VG port of the second amplifier is connected with one end of the seventh resistor and one end of the eighth resistor respectively, the other end of the seventh resistor is grounded, the other end of the eighth resistor is connected with the power supply module, the VD port of the second amplifier is connected with the first drain modulator, the first drain modulator is connected with the control signal input end and the power supply module respectively, the output end of the second amplifier is connected with the first digital attenuator, the first digital attenuator is connected with the first digital attenuator control signal input end, the NOT gate and the second digital attenuator respectively, the NOT gate is connected with the mode switching control circuit, the second digital attenuator is connected with the second digital attenuator control signal input end and the temperature compensation attenuator, the temperature compensation attenuator is connected with the input end of the third amplifier, the VG port of the third amplifier is connected with the mode switching control circuit, the VD port of the third amplifier is connected with the second drain modulator, the second drain modulator is connected with the control signal input end and the power supply module respectively, the drain modulator control signal input end is connected with the first drain modulator and the second drain modulator respectively (not shown in the figure), the output end of the third amplifier is connected with the first isolator, and the first isolator is connected with the radio frequency signal output port.
[0008] In some embodiments, the mode switching control circuit includes a class-C state control signal input end, a second buffer, a diode, an NMOS tube, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a sixth resistor.
[0009] The class C state control signal input end is connected with the second buffer, the second buffer is connected with one end of the fifth resistor, one end of the sixth resistor and the non gate respectively, the other end of the fifth resistor is grounded, the other end of the sixth resistor is connected with the negative electrode of the diode, the positive electrode of the diode is connected with one end of the fourth resistor and the gate of the NMOS tube respectively, the drain of the NMOS tube is connected with one end of the first resistor, one end of the second resistor and the third amplifier respectively, the other end of the second resistor is grounded, the other end of the first resistor is connected with one end of the third resistor, the other end of the fourth resistor and the power supply module respectively, and the other end of the third resistor is connected with the source of the NMOS tube.
[0010] In some embodiments, the diode is a zener diode.
[0011] In some embodiments, the first digital attenuator has an attenuation of 10dB.
[0012] In some embodiments, the second digital attenuator has an attenuation of 15dB-30dB.
[0013] The output mode switchable transmitting circuit has the advantages that in the low-power output mode, the transmitting circuit output power can be adjusted, the transmitting signal is turned off by using the traditional amplifier drain power-off mode; in the high-power mode, the transmitting circuit output power is fixed, the transmitting signal is turned off by using a non-traditional mode, and the transmitting circuit does not have noise delay leakage, so that the receiver can receive information without delay, and the transmission efficiency is greatly improved. BRIEF DESCRIPTION OF DRAWINGS
[0014] Figure 1 In the background art of the utility model, the public end of the transceiver system is a circulator.
[0015] Figure 2 In the background art of the utility model, the internal amplifier power supply switch of the transmitter.
[0016] Figure 3 In the background art of the utility model, the power amplifier tailing phenomenon.
[0017] Figure 4 In the output mode switchable transmitting circuit structure schematic diagram of the utility model embodiment.
[0018] Figure 5 In the output mode switchable transmitting circuit of the utility model embodiment.
[0019] Figure 6 In the low-power mode equivalent circuit of the utility model embodiment.
[0020] Figure 7 In the high-power mode equivalent circuit of the utility model embodiment.
[0021] Figure 8 The system enters a receiving period equivalent circuit in the embodiment of the utility model.
[0022] Figure 9 The control mode switching circuit in the embodiment of the utility model.
[0023] Figure 10 The equivalent circuit when D0 is low in the embodiment of the utility model.
[0024] Figure 11 The equivalent circuit when D0 is high in the embodiment of the utility model.
[0025] Figure 12 The circuit simulation result in the embodiment of the utility model. DETAILED DESCRIPTION
[0026] In order to make the technical problems, technical schemes and beneficial effects of the present application clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.
[0027] EMBODIMENT
[0028] The power amplifier can be divided into class A, class B, class AB and class C according to the conduction angle. The conduction angle refers to the phase value corresponding to the transistor conduction time in a signal period. For example, the conduction angle of class A amplifier is 360°, which means that the amplifier is in the conduction state throughout the signal period. Class B amplifier and class AB amplifier have two transistors, and only one transistor is in conduction at any time, and the conduction angle of each transistor is 180°, which means that each transistor is in conduction alternately in each half signal period. The conduction angle of class C amplifier is less than 180°, which means that the transistor is in conduction for less than half of the signal period. Since the class AB amplifier is actually in conduction throughout the period, noise is still amplified when the input signal is off. The conduction angle of class C amplifier is very small, and it will not be in conduction in the absence of signal input, so the noise generated is very small. By changing the gate voltage, the switching between class AB working state and class C working state can be realized.
[0029] Based on the above principle, the present example designs a transmitting circuit with switchable output mode. In the small power output mode, the output power of the transmitting circuit can be adjusted, and the transmitting signal is off by using the traditional amplifier drain power-off method, and the transmitting circuit has noise delay leakage. In the large power mode, the output power of the transmitting circuit is fixed, and the transmitting signal is off by using a non-traditional method, and the transmitting circuit has no noise delay leakage.
[0030] The output mode switchable transmitting circuit of the present example comprises three amplifiers, as shown in Figure 5 two digitally controlled attenuators between the second amplifier and the third amplifier, the first digitally controlled attenuator has an attenuation of 10 dB and can be controlled by one signal, and the second digitally controlled attenuator has an attenuation of 15 dB to 30 dB and can be controlled by five signals, namely, D1, D2, D3, D4 and D5. The first drain modulator and the second drain modulator are controlled by one PTT transmitting switch. The third amplifier can work in AB class or C class amplification state, which can be realized by changing the gate voltage. The mode switching control circuit can switch the working mode of the transmitting circuit, i.e., the small power output mode and the large power output mode. The connection mode of some power supply modules is given in the circuit, which is not completely connected, but it is well known in the art that the power supply for the circuit devices is not described herein.
[0031] The working principle of the small power mode is analyzed as follows: the equivalent circuit in the small power mode is shown in Figure 6 From the output power values of the circuits at various stages shown in the figure, it can be seen that the power reaches saturation after the signal passes through the second stage amplifier. The purpose of the design here is to ensure that the same output power can be obtained when the input signal is in the range of -13 dBm to -7 dBm. The first digitally controlled attenuator is not used, only having an insertion loss of 1 dB, and the second digitally controlled attenuator is used to control the output power, with an adjustable attenuation of 20 dB to 30 dB. Since the signal power input to the final stage amplifier is very small, the final stage amplifier works in the linear interval, so that the power of the final output signal is controllable between 25 dBm and 35 dBm. At this time, the gate control voltage of the final stage amplifier is about -2 V, and the amplifier is in AB class amplification state.
[0032] The working principle of the large power mode is analyzed as follows: the equivalent circuit in the large power mode is shown in Figure 7 The drain modulator of the third stage amplifier does not work in the large power mode. The output power of the second stage amplifier at this time is the same as that in the small power mode, which is 34.5 dBm, and the attenuation of the first attenuator is controlled to be 10 dB, and the second attenuator does not attenuate. At this time, the signal power input to the third stage amplifier is 19.5 dBm, and the gate voltage of the third stage amplifier is -4 V, and the power amplifier works in C class amplification state, and only when there is a large input signal excitation, the power amplifier will be turned on. It is tested that only when the signal power is greater than or equal to 10 dBm, the power amplifier has signal output, and the gain increases with the increase of the input power. When the input power is 19.5 dBm, the gain reaches 26 dB, and the final output signal power is 45 dBm.
[0033] When the system enters the receiving period, there is no signal at the input end of the transmitter, only noise. The equivalent circuit at this time is shown in Figure 8The input temperature noise is -89.77dBm. Since the noise is the bottom noise, the first fixed attenuator is invalid, the noise entering the first amplifier is still -89.77dBm. After a series of amplification and attenuation of the subsequent link, it can be seen that the noise power entering the third amplifier is -61.77dBm. At this time, the third amplifier works in class C amplification state, and the noise power is very small, which cannot excite the amplifier to turn on, and the amplifier is in the off state. Since the amplifier is not an ideal switch, it cannot completely isolate the input and output ports, and its isolation is only 20dB. Therefore, the noise at the output end of the third amplifier is -81.77dBm, and the final output noise is -82.77dBm, which is 7.5dB higher than the bottom noise. Since the isolator at the transceiver end also has an isolation of 20dB, the transmitter noise and the bottom noise leaked to the receiving end are the same, which will not affect the receiver.
[0034] The working principle of the mode switching control circuit is analyzed as follows: Figure 9 As shown in the figure, the control signal input end of the class C state control signal inputs the control signal D0, which is sent to the mode switching control circuit after being driven by the buffer. The circuit is mainly composed of a voltage stabilizing diode and an N-channel field effect transistor. The voltage stabilizing diode has a voltage stabilizing value of +3.3V, and the threshold voltage of the field effect transistor T1 is 2.2V. When D0 is high, the buffer outputs 3.3V high level, so the attenuator control signal at point A is 3.3V high level. At this time, the negative electrode of the voltage stabilizing diode is 3.3V, so the positive electrode voltage is 3.3V-3.3V=0V. The gate of the field effect transistor is connected to the positive electrode of the voltage stabilizing diode, so the voltage is also 0V. The source of the field effect transistor is connected to the negative voltage source -5V through a 100Ω resistor R3, so the gate-source voltage drop VGS=0V-(-5V)=5V>2.2V threshold, and the field effect transistor should be turned on. The equivalent circuit is shown in the figure. Figure 10 At this time, the output voltage at point B is the resistance after R1 and R4 are connected in parallel, and then R2 is divided by -5V. The calculated voltage value is -3.95V. At this time, the gate-source voltage VGS of the field effect transistor decreases from 5V to 3.95V and remains unchanged.
[0035] Similarly, when D0 input is low, the buffer output level is 0V, point A is low output, the negative electrode of the voltage stabilizing diode is 0V, so the positive electrode voltage is 0V-3.3V=-3.3V, that is, the gate voltage of the field effect transistor is -3.3V, and the source voltage of the field effect transistor is -5V, so VG-VS=-3.3V-(-5V)=1.7V<2.2V threshold, and the field effect transistor is cut off. The equivalent circuit is shown in the figure. Figure 11 At this time, the voltage at point B is the voltage value obtained by dividing R1 and R2 by -5V. The calculated voltage value is -2.17V, and the gate-source voltage of the field effect transistor remains unchanged at 1.7V.
[0036] The circuit simulation result is shown in the figure. Figure 12As shown, the output voltages of A and B points are consistent with the above calculation. It should be noted that the switching time of the two modes is not required, because the transmitting circuit will not frequently switch the working mode, and when in one mode, it will not change for a long time, so it will not affect the work of the receiving system.
[0037] In summary, the circuit in this example uses one TTL control signal to generate the gate voltage required when the amplifier class changes, and to generate the control signal of the digital attenuator to switch the working mode of the circuit. In the low-power working mode, all amplifiers are in AB state, and the off mode is to turn off the amplifier power supply by using the drain modulation switch; in the high-power mode, the final amplifier is in C state, and the off method of the final amplifier is not to turn off the drain power supply, but to turn off the input excitation signal. Thus, the delay-free reception is realized, and by using the feature that the output of the class C amplifier is controlled by the input excitation signal, when there is no signal input, the class C amplifier itself can be completely turned off without generating noise tailing.
[0038] The technical features of the above embodiments can be combined arbitrarily, and to make the description concise, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.
[0039] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.
Claims
1. A transmitting circuit with switchable output mode, comprising a power supply module, which supplies the transmitting circuit with power, characterized in that, The mode switching control circuit comprises a class C state control signal input end, a second buffer, a diode, an NMOS tube, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a sixth resistor. The radio frequency signal input port, the first attenuator, the first amplifier, the second attenuator, the first filter and the second amplifier are sequentially connected, the VG port of the second amplifier is connected with one end of the seventh resistor and one end of the eighth resistor respectively, the other end of the seventh resistor is grounded, the other end of the eighth resistor is connected with a power supply module, the VD port of the second amplifier is connected with the first drain modulator, the first drain modulator is connected with the control signal input end and the power supply module respectively, the output end of the second amplifier is connected with the first digital attenuator, the first digital attenuator is connected with the first digital attenuator control signal input end, the NOT gate and the second digital attenuator respectively, the NOT gate is connected with the mode switching control circuit, the second digital attenuator is connected with the second digital attenuator control signal input end and the temperature compensation attenuator, the temperature compensation attenuator is connected with the input end of the third amplifier, the VG port of the third amplifier is connected with the mode switching control circuit, the VD port of the third amplifier is connected with the second drain modulator, the second drain modulator is connected with the control signal input end and the power supply module respectively, the drain modulator control signal input end is connected with the first drain modulator and the second drain modulator respectively, the output end of the third amplifier is connected with the first isolator, and the first isolator is connected with the radio frequency signal output port.
2. The output mode switchable transmit circuit of claim 1, wherein, The mode switching control circuit comprises a class C state control signal input end, a second buffer, a diode, an NMOS tube, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and a sixth resistor. The C class state control signal input end is connected with the second buffer, one end of the fifth resistor, one end of the sixth resistor and the NOT gate respectively, the other end of the fifth resistor is grounded, the other end of the sixth resistor is connected with the negative electrode of the diode, the positive electrode of the diode is connected with one end of the fourth resistor and the gate of the NMOS tube respectively, the drain of the NMOS tube is connected with the third amplifier, one end of the first resistor and one end of the second resistor respectively, the other end of the second resistor is grounded, the other end of the first resistor is connected with one end of the third resistor, the other end of the fourth resistor and the power supply module respectively, and the other end of the third resistor is connected with the source of the NMOS tube.
3. The output mode switchable transmit circuit of claim 2, wherein, The diode is a voltage stabilizing diode.
4. The output mode switchable transmit circuit of claim 3, wherein, The attenuation of the first digital attenuator is 10 dB.
5. The output mode switchable transmit circuit of claim 4, wherein, The attenuation of the second digital attenuator is 15 dB to 30 dB.