A radio frequency front-end system based on an impedance transformation switch network

Abstract

The present invention is applicable to the technical field of millimeter-wave radio frequency front-end architecture research, and provides a radio frequency front-end system based on an impedance transformation switch network, including: a main power amplifier, a secondary power amplifier, a low-noise amplifier, a quarter-wavelength transmission line, an impedance transformation switch network, an antenna, a main power amplifier input interface, a secondary power amplifier input interface, and a low-noise amplifier output interface. Based on the radio frequency front-end system provided by the present invention, using an impedance transformation network instead of a switch in the transmit link can achieve the effects of no additional switch insertion loss and no bandwidth limitation for the transmit link signal, and setting a single-pole single-throw switch in the receive link can improve the isolation between the transmit link and the receive link. This way of changing the radio frequency front-end system architecture can maximize the conversion of the power amplifier efficiency into the transmit link efficiency, thereby reducing the system power consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of millimeter-wave radio frequency front-end architecture research, and particularly relates to a radio frequency front-end system based on an impedance transformation switch network. Background Art

[0002] The radio frequency front-end system is a core module in a wireless communication system. The radio frequency front-end system is composed of key devices such as a power amplifier, a low-noise amplifier, and a switch. Among them, the power amplifier is located in the transmitting link, and the low-noise amplifier is located in the receiving link. The radio frequency front-end system restricts the overall performance of the communication system and will directly affect the user experience. Among them, the power amplifier is the most critical device that limits the bandwidth, linearity, and efficiency of the radio frequency front-end system. Limited by the development of the process, the power and efficiency of the power amplifier in the millimeter-wave band are relatively low. Therefore, it is necessary to find a way to improve the efficiency of the radio frequency front-end system to reduce the system power consumption. Among them, by improving the radio frequency front-end architecture, the efficiency of the power amplifier can be maximally converted into the efficiency of the transmitting link, which is also an important method to reduce the system power consumption. Among them, a very crucial part of the radio frequency front-end system architecture design lies in the selection and design of the switch type.

[0003] The traditional switch uses a single-pole double-throw structure to realize the switching between the receiving mode and the transmitting mode. Among them, the power amplifier of the radio frequency front-end system is in a cascade relationship with the switch. Since the single-pole double-throw switch is directly connected to the antenna, it has an important impact on the performance of the links in both the receiving mode and the transmitting mode. In the receiving mode, the single-pole double-throw switch is located before the low-noise amplifier, and the insertion loss introduced by the single-pole double-throw switch will deteriorate the noise figure of the receiving link; in the transmitting mode, the single-pole double-throw switch is located after the output end of the power amplifier, and the insertion loss introduced by the single-pole double-throw switch will directly reduce the output power and efficiency of the transmitting link. At the same time, the bandwidth of the single-pole double-throw switch will also impose certain restrictions on the overall bandwidth of the radio frequency front-end system.

[0004] Therefore, the design and optimization of the switch have a crucial impact on the working performance of the radio frequency front-end system. Summary of the Invention

[0005] In order to solve the above problems existing in the related technologies, the present invention provides a radio frequency front-end system based on an impedance transformation switch network. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0006] The present invention provides a radio frequency front-end system based on an impedance transformation switch network, characterized in that the radio frequency front-end system comprises: a main power amplifier, a secondary power amplifier, a low-noise amplifier, a quarter-wavelength transmission line, an impedance transformation switch network, an antenna, a main power amplifier input interface, a secondary power amplifier input interface, and a low-noise amplifier output interface; wherein, the main power amplifier, the secondary power amplifier, the quarter-wavelength transmission line, the main power amplifier input interface, and the secondary power amplifier input interface are all located in the transmission link of the radio frequency front-end system, and the low-noise amplifier and the low-noise amplifier output interface are both located in the receiving link of the radio frequency front-end system; the first end of the main power amplifier is connected to the main power amplifier input interface, the first end of the secondary power amplifier is connected to the secondary power amplifier input interface, the second end of the secondary power amplifier is connected to the first end of the quarter-wavelength transmission line, and the second end of the quarter-wavelength transmission line and the second end of the main power amplifier are both connected to the first end of the impedance transformation switch network; the first end of the low-noise amplifier is connected to the low-noise amplifier output interface, and the second end of the low-noise amplifier is connected to the second end of the impedance transformation switch network; the third end of the impedance transformation switch network is connected to the antenna; and the impedance transformation switch network is used to improve the working performance of the radio frequency front-end system in different working modes.

[0007] The present invention has the following beneficial technical effects: Aiming at the problems in the existing radio frequency front-end system that due to the switch insertion loss, the power and efficiency of the power amplifier in the millimeter wave band are relatively low, and the bandwidth of the switch limits the overall bandwidth of the radio frequency front-end system, the radio frequency front-end system based on the impedance transformation switch network provided by the present invention can obtain the effect that there is no additional switch insertion loss for the electrical signal transmitted in the transmission link in the transmission mode, maximize the conversion rate between the power amplifier output power and the antenna output power, and ensure that there is no bandwidth limitation in the transmission link. And in the receiving mode, it can obtain the effect of effectively improving the isolation degree between the transmission link and the receiving link and avoiding the leakage power from damaging the devices in the receiving link. Thus, based on the above method, the system power consumption can be effectively reduced.

[0008] The following will further elaborate on the present invention in detail with reference to the drawings and embodiments. Description of the Drawings

[0009] Figure 1 is the result block diagram of a radio frequency front-end system based on an impedance transformation switch network provided by the present invention;

[0010] Figure 2 is the architecture schematic diagram of an impedance transformation switch network applied to a radio frequency front-end system provided by the present invention;

[0011] Figure 3 is the architecture schematic diagram of the radio frequency front-end system in the transmission mode provided by the present invention;

[0012] Figure 4 It is a schematic diagram of the architecture of the RF front-end system in the receiving mode provided by the present invention;

[0013] Figure 5 It is a schematic diagram of the architecture of the input matching network of the low-noise amplifier provided by the present invention;

[0014] Figure 6 It is an equivalent circuit diagram of the RF front-end system in the transmitting mode provided by the present invention;

[0015] Figure 7 It is an equivalent circuit diagram of the RF front-end system after Norton transformation provided by the present invention;

[0016] Figure 8 It is the equivalent impedance Z of the main power amplifier provided by the present invention 功放 and an equivalent circuit diagram of the RF front-end system after equivalent transformation of the first parasitic capacitance C0;

[0017] Figure 9 It is a schematic diagram of the lossless ideal transformer in the RF front-end system provided by the present invention;

[0018] Figure 10 It is a schematic diagram of the structure of the single-pole single-throw switch provided by the present invention;

[0019] Figure 11 It is an equivalent schematic diagram of the single-pole single-throw switch in the transmitting mode provided by the present invention;

[0020] Figure 12 It is an equivalent schematic diagram of the single-pole single-throw switch in the receiving mode provided by the present invention. Detailed implementation manners

[0021] The following further describes the present invention in detail with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0022] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0023] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0024] Although the present invention has been described in connection with various embodiments herein, however, in the process of implementing the claimed invention, those skilled in the art can understand and realize other variations of the disclosed embodiments by viewing the accompanying drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude a plurality. A single processor or other unit can implement several functions recited in the claims. Certain measures are recited in mutually different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0025] The radio frequency front-end system is a prerequisite for ensuring the normal and stable operation of the communication system. Specifically, when the radio frequency front-end system is in the transmit mode, a baseband modulated signal is acquired, and then the baseband modulated signal is modulated into a radio frequency signal through means such as amplification, filtering, and up-conversion, and the radio frequency signal is radiated through the antenna after reaching a certain power level; when the radio frequency front-end system is in the receive mode, the weak radio frequency signal in space is received through the antenna, and then the baseband modulated signal is obtained through means such as filtering, amplification, and frequency conversion, and finally the baseband modulated signal is sent to the demodulation module for demodulation.

[0026] In the existing radio frequency front-end system, a single-pole double-throw switch is used to achieve the switching between the transmit and receive modes. However, this method will cause the switch and the power amplifier to be in a cascaded relationship. That is to say, if the switch is connected behind the power amplifier, it will introduce additional insertion loss, reduce the power and efficiency of the transmit link, and the bandwidth of the switch will also impose certain limitations on the overall bandwidth of the radio frequency front-end system.

[0027] In view of the above problems, the present invention provides a radio frequency front-end system based on an impedance transformation switch network, which can solve the problems that the power and efficiency of the power amplifier are relatively low in the millimeter wave band due to the insertion loss of the switch, and the bandwidth of the switch limits the overall bandwidth of the radio frequency front-end system.

[0028] Figure 1It is the result block diagram of a radio frequency front-end system based on an impedance transformation switch network provided by the present invention. As Figure 1 shown, the radio frequency front-end system includes: a main power amplifier, a secondary power amplifier, a low-noise amplifier, a quarter-wavelength transmission line (denoted by ), an impedance transformation switch network, an antenna, a main power amplifier input interface, a secondary power amplifier input interface, and a low-noise amplifier output interface; among them, the main power amplifier, the secondary power amplifier, the quarter-wavelength transmission line, the main power amplifier input interface, and the secondary power amplifier input interface are all located in the transmitting link of the radio frequency front-end system, and the low-noise amplifier and the low-noise amplifier output interface are both located in the receiving link of the radio frequency front-end system; the first end of the main power amplifier is connected to the main power amplifier input interface, the first end of the secondary power amplifier is connected to the secondary power amplifier input interface, the second end of the secondary power amplifier is connected to the first end of the quarter-wavelength transmission line, and the second ends of the quarter-wavelength transmission line and the main power amplifier are both connected to the first end of the impedance transformation switch network; the first end of the low-noise amplifier is connected to the low-noise amplifier output interface, and the second end of the low-noise amplifier is connected to the second end of the impedance transformation switch network; the third end of the impedance transformation switch network is connected to the antenna; the impedance transformation switch network is used to improve the working performance of the radio frequency front-end system in different working modes.

[0029] Here, the power amplifier refers to a power amplifier, and the low-noise amplifier refers to a low-noise amplifier. Among them, the power amplifier is a Doherty power amplifier. The Doherty power amplifier includes a main power amplifier and a secondary power amplifier. The Doherty power amplifier divides the input signal into two branches, amplifies them separately, and finally combines the signals of the two branches and outputs them. The working principle of the Doherty power amplifier can be divided into two stages: the modulation stage and the amplification stage. In the modulation stage, the signal in the main power amplifier is amplified to the maximum power, and the signal in the secondary power amplifier is amplified to the minimum power; in the amplification stage, the signals in the main power amplifier and the secondary power amplifier are combined together to form a high-efficiency power amplifier output signal, so that the input signal can reach a farther distance. In addition, the main power amplifier and the secondary power amplifier can also be used for signal conditioning of the input signal, such as filtering, gain control, and frequency control, etc. The low-noise amplifier, that is, an amplifier with a very low noise figure, can be used to amplify the electrical signal received by the antenna, and at the same time, reduce the interference of the amplifier itself to the signal as much as possible, and improve the signal-to-noise ratio of the output signal. The quarter-wavelength transmission line is used to resonate at a specific frequency to obtain better waveguide characteristics. The main power amplifier input interface and the secondary power amplifier input interface are respectively used to receive the electrical signals input by the signal source, and the low-noise output interface is used to output the signal processed by the low-noise amplifier, and this signal is used to input the demodulation circuit for demodulation. The antenna is used to transmit and receive electrical signals, and the electrical signals include radio frequency signals.

[0030] To specifically illustrate the composition of the radio frequency front-end system, Figure 2 It is the schematic diagram of the architecture of the impedance transformation switch network applied to the radio frequency front-end system provided by the present invention. AsFigure 2 As shown, the impedance switch transformation network includes: an impedance transformation network and a single-pole single-throw switch; the impedance transformation network includes: an on-chip transformer (with a turns ratio of 1:n, where n is the total number of turns of the coil), a first post-matching capacitor C series and a second post-matching capacitor C pad ; the impedance transformation network is located in the transmitting link, and the single-pole single-throw switch is located in the receiving link; the second end of the main power amplifier is connected to the first end of the on-chip transformer, and the second end of the quarter-wavelength transmission line is connected to the second end of the on-chip transformer; the third end of the on-chip transformer is connected to the first end of the first post-matching capacitor, and the fourth end of the on-chip transformer is grounded; the second end of the first post-matching capacitor and the first end of the second post-matching capacitor are both connected to the antenna; the second end of the second post-matching capacitor is grounded; the first end of the single-pole single-throw switch is connected to the second end of the low-noise amplifier, and the second end of the single-pole single-throw switch is connected to the antenna.

[0031] The different operating modes of the RF front-end system include a transmitting mode and a receiving mode; when the RF front-end system is in the transmitting mode, the single-pole single-throw switch is in the off state, and the auxiliary power amplifier is grounded; through the impedance transformation network, the main power amplifier transmits the power amplifier output signal without additional switch insertion loss to the antenna, and the power amplifier output signal is obtained by processing the signal transmitted through the main power amplifier input interface by the main power amplifier; when the RF front-end system is in the receiving mode, the main power amplifier and the auxiliary power amplifier are in the power amplifier off state, and the single-pole single-throw switch is in the on state; the low-noise amplifier sends the received electrical signal to the low-noise amplifier output interface. Here, the electrical signal includes the RF signal in space.

[0032] Here, in the transmitting mode, the power amplifier is divided into a back-off region and a saturation region according to the magnitude of the transmitting power. Among them, the back-off region refers to the power amplifier back-off region. Power amplifier back-off means that due to the excessive signal power input to the main power amplifier and the insufficient gain of the auxiliary power amplifier, it cannot withstand the signal peak, resulting in a reduction in the output power of the transmitting link. In other words, when the power amplifier is in the adjustment stage, the transmitting power of the power amplifier is relatively small and is in the back-off region. At this time, the main power amplifier works and the auxiliary power amplifier does not work; when the power amplifier is in the amplification stage, the transmitting power of the power amplifier is relatively high and is in the saturation region. At this time, both the main power amplifier and the auxiliary power amplifier are in the working mode. That is to say, when the RF front-end system is in the transmitting mode and the power amplifier works in the back-off region, the auxiliary power amplifier is grounded. And, when only the main power amplifier works, the power amplifier output signal is provided by the main power amplifier; while when both the main power amplifier and the auxiliary power amplifier are in the working mode, the power amplifier input signal includes both the electrical signal obtained by processing the signal transmitted through the main power amplifier input interface by the main power amplifier and the electrical signal obtained by processing the signal transmitted through the auxiliary power amplifier input interface by the auxiliary power amplifier.

[0033] The following will take Figure 3 and Figure 4Take it as an example to illustrate the operating states of each link under different operating modes of the RF front-end system. It should be noted that Figure 3 and Figure 4 combine the main power amplifier and the auxiliary power amplifier into one power amplifier, and do not specifically show the operating states of the main power amplifier and the auxiliary power amplifier.

[0034] Figure 3 is a schematic diagram of the architecture of the RF front-end system in the transmission mode provided by the present invention. As Figure 3 shown, in the transmission mode, the single-pole single-throw switch is turned off and the receiving link is turned off; the impedance transformation network on the transmitting link plays a role of impedance matching. After passing through the impedance transformation network, the power amplifier amplifies the received weak electrical signal and then sends it to the antenna.

[0035] Figure 4 is a schematic diagram of the architecture of the RF front-end system in the receiving mode provided by the present invention. As Figure 4 shown, the power amplifier is in the power-off state, and the high-impedance state at the root of the power amplifier is transmitted to the antenna port through the impedance transformation network, so that the transmitting link is disconnected; the single-pole single-throw switch is turned on. Specifically, in the receiving mode, the impedance at the root of the power amplifier is the off-impedance Z BJT_off , and the impedance Z BJT_off at the root of the power amplifier is transformed to Z PA_off on the antenna side through the impedance transformation network, so that Z PA_off exhibits a high-impedance characteristic, so that the power amplifier is in the power-off state. In addition, in the receiving mode, the RF front-end system further includes a low-noise amplifier input matching network. The low-noise amplifier input matching network is on the receiving link. The first end of the low-noise amplifier input matching network is connected to the second end of the low-noise amplifier, and the second end of the low-noise amplifier input matching network is connected to the first end of the single-pole single-throw switch. Among them, the low-noise amplifier input matching network is used to obtain the desired noise figure.

[0036] Figure 5 is a schematic diagram of the architecture of the low-noise amplifier input matching network provided by the present invention. As Figure 5 shown, the low-noise amplifier input matching network includes: a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first inductor L1, and a second inductor L2. Among them, the first capacitor C1, the second capacitor C2, and the third capacitor C3 are connected in parallel and then connected in series with the first inductor L1; the second inductor L2 and the fourth capacitor C4 are connected in parallel and also connected in series with the first inductor L1.

[0037] Here, when the RF front-end system is in the transmission mode and the power amplifier is in the back-off region, the auxiliary power amplifier in the back-off region is in the off state. After being equivalently transformed by a quarter-wavelength transmission line, at Figure 2It is reflected in the grounding of the auxiliary power amplifier. When the RF front-end system is in the transmit mode, the single-pole single-throw switch is in the off state, and the auxiliary power amplifier is grounded, the power amplifier output signal without additional switch insertion loss is transmitted from the main power amplifier to the antenna in the following manner: Obtain the parasitic parameters of the main power amplifier and the equivalent inductance of the impedance transformation network; use the parasitic parameters of the main power amplifier and the equivalent inductance of the impedance transformation network to determine the impedance transformation ratio of the impedance change network; determine the coupling coefficient through the impedance transformation ratio; use the ratio of the coupling coefficient and the number of turns of the on-chip transformer to adjust the number of turns of the on-chip transformer connected to the transmit link, and obtain the result that the impedance of the main power amplifier is equal to the impedance of the antenna; based on the result that the impedance of the main power amplifier is equal to the impedance of the antenna, the main power amplifier transmits the power amplifier output signal without additional switch insertion loss to the antenna.

[0038] Among them, the equivalent inductance of the impedance transformation network includes: a first equivalent inductance and a second equivalent inductance, and the parasitic parameters of the main power amplifier include: a first parasitic capacitance and a first parasitic inductance. Therefore, using the parasitic parameters of the main power amplifier and the equivalent inductance of the impedance transformation network to determine the impedance transformation ratio of the impedance change network includes: equivalently combining the first parasitic inductance and the first equivalent inductance to obtain a first combined inductance; performing Norton transformation on the first combined inductance and the second equivalent inductance to obtain the impedance transformation ratio of the impedance change network.

[0039] Here, insertion loss refers to insertion loss. Usually, inserting an element between the power amplifier and the antenna will cause signal loss or signal attenuation, that is, insertion loss is generated. The insertion loss introduced by the switch is the main reason for the low transmit power and efficiency of the transmit link. To avoid the additional insertion loss introduced by the switch, an impedance transformation network can be used to replace the original switch, where the impedance on the antenna side is made consistent with the impedance required on the main power amplifier side by adjusting the number of turns of the coil of the on-chip transformer connected to the circuit; and since no switch is provided in the transmit link, there will also be no problem that the bandwidth of the transmit link is limited by the bandwidth of the switch. And how to determine the specific number of turns of the coil connected to the transmit link needs to be calculated in combination with the main power amplifier, the impedance transformation network, and the impedance on the antenna side.

[0040] To illustrate in detail how the impedance transformation switch network provided by the present invention avoids generating additional switch insertion loss in the transmit link, the following will be combined with Figures 6 - 9 to illustrate how to transmit the power amplifier output signal without additional switch insertion loss from the main power amplifier to the antenna through the impedance transformation network. Figure 6 is the equivalent circuit diagram of the RF front-end system in the transmit mode provided by the present invention. As Figure 6 shown, in the RF front-end system in the transmit mode, the transmit link is in the working state, where the auxiliary power amplifier is grounded. The equivalent impedance of the main power amplifier is represented by Z 功放 , where Z 功放 = 2R opt , Ropt refers to the optimal load value of the power amplifier, and the equivalent impedance on the antenna side is R 天线 . Figure 6 includes a parasitic parameter network, an on-chip transformer equivalent network, and a post-matching network.

[0041] Among them, the parasitic parameter network is used to represent the parasitic parameters output by the main power amplifier. The impedance of the main power amplifier is equivalent to a first parasitic capacitor C0 and a first parasitic inductor L0; the first end of the equivalent impedance of the main power amplifier is grounded, and the second end of the equivalent impedance Z 功放 of the main power amplifier is connected to the second end of the first parasitic capacitor C0. The first end of the first parasitic capacitor C0 is grounded, and the second end of the first parasitic capacitor C0 is also connected to the first end of the first parasitic inductor L0. The on-chip transformer equivalent network includes an on-chip transformer and its equivalent impedance. Among them, the equivalent impedance of the on-chip transformer is expressed as a first equivalent inductor L1 and a second equivalent inductor L2. The first end of the first equivalent inductor L1 is connected to the second end of the first parasitic inductor L0. The second end of the first equivalent inductor L1 is respectively connected to the second end of the second equivalent inductor L2 and the first end of the on-chip transformer. The first end of the second equivalent inductor L2 is grounded. The post-matching network includes a first post-matching capacitor C series and a second post-matching capacitor C pad .

[0042] Here, the first equivalent inductor L1 can be expressed as L1 = (1 - k 2 )L P ; the second equivalent inductor L2 can be expressed as L2 = k 2 L P ; the turns ratio of the on-chip transformer can be expressed as 1:n / k. Among them, L P refers to the self-inductance of the primary coil of the transformer, k represents the coupling coefficient between the primary coil and the secondary coil of the on-chip transformer, and the value of k is related to the impedance transformation ratio r of the impedance transformation network.

[0043] Figure 7 is the equivalent circuit diagram of the radio frequency front-end system after Norton transformation provided by the present invention. As Figure 7 shown, the solving process of the impedance transformation ratio r is as follows: L0 and L1 are equivalently combined into L3, L3 = L0 + L1; then L3 and L2 are subjected to Norton transformation to obtain the impedance transformation ratio r, r = (L3 + L2) / L2 ≈ 1 / k 2 . The two inductors after exchange are respectively expressed as L'2 and L'3, L'2 = L2 / r, L'3 = L3 / r.

[0044] To facilitate the description of the working principle that the impedance transformation network makes the impedance on the antenna side consistent with the optimal impedance required on the main power amplifier side, here the equivalent impedance Z 功放 of the main power amplifier and the first parasitic capacitor C0 are further equivalent. Figure 8is the equivalent impedance Z of the main power amplifier provided by the present invention 功放 and the equivalent circuit diagram of the RF front-end system after equivalent transformation of the first parasitic capacitance C0. Refer to Figure 8 , and use the impedance transformation ratio to perform equivalent transformation on the equivalent impedance Z of the main power amplifier 功放 and the first parasitic capacitance C0 to obtain the equivalent impedance Z' 功放 and the first parasitic capacitance C'0, where Z' 功放 = 2R opt / r 2 , C'0 = r 2 C0.

[0045] Furthermore, the first post-matching capacitor C in the post-matching network series and the second post-matching capacitor C pad are equivalently migrated to the left side of the on-chip transformer to obtain C' series and C' pad , where C' series = n 2 / (k 2 C series ), C' pad = n 2 / (k 2 C pad ). By designing parameters, L'3 and C' series can form a series resonance in the required millimeter-wave frequency band, and at the same time, C'0, L'2 and C' pad can form a parallel resonance in the required millimeter-wave frequency band. The series resonance will cause L'3 and C' series to be short-circuited, and the parallel resonance will cause C'0, L'2 and C' pad to be open-circuited. Among them, the design parameters include the size of the on-chip transformer and the size of the first post-matching capacitor. Through the resonance of each component, an ideal transformer with a coupling coefficient of 1 and no loss can be obtained.

[0046] Figure 9 is a schematic diagram of the ideal transformer without loss in the RF front-end system provided by the present invention. As Figure 9 shown, the impedance transformation network can undergo a series of equivalent transformations to make the impedance on the antenna side consistent with the optimal impedance required on the main power amplifier side, so that based on the impedance transformation network, the effect of transmitting the power amplifier output signal without additional switch insertion loss between the main power amplifier and the antenna can be achieved.

[0047] In the present invention, when the RF front-end system is in the receiving mode, the main power amplifier and the auxiliary power amplifier of the transmitting link are in the power amplifier off state. The power amplifier off means that the impedance at the root of the power amplifier is in a high-impedance state and the power amplifier is in a non-operating mode. And, the single-pole single-throw switch of the receiving link is in the conducting state.

[0048] To facilitate the description of the working principle of the single-pole single-throw switch, Figure 10 is a schematic structural diagram of the single-pole single-throw switch provided by the present invention. As Figure 10 shown, the single-pole single-throw switch includes a first transistor Q1, a second transistor Q2, and a third transistor Q3; the first transistor Q1 and the second transistor Q2 are connected in series, and the third transistor Q3 is connected in parallel with the first transistor Q1 and the second transistor Q2. When the single-pole single-throw switch is in the off state, the first transistor Q1 and the second transistor Q2 are turned off, and the third transistor Q3 is turned on; when the single-pole single-throw switch is in the on state, the first transistor Q1 and the second transistor Q2 are turned on, and the third transistor Q3 is turned off. By setting the single-pole single-throw switch on the receiving link, the isolation between the transmitting link and the receiving link can be improved, preventing the power leaked to the receiving link from being too large and causing damage to the devices on the receiving link. Moreover, even if some power leaks to the receiving link, based on the single-pole single-throw switch, it can also ensure that the devices will not be damaged.

[0049] Figure 11 is an equivalent schematic diagram of the single-pole single-throw switch in the transmitting mode provided by the present invention. As Figure 11 shown, when the single-pole single-throw switch is in the off state, the single-pole single-throw switch is equivalent to: a first off-capacitance C off1 , a second off-capacitance C off2 , and a first on-resistance R on1 , where the first off-capacitance C off1 is connected in series with the second off-capacitance C off2 , and the first on-resistance R on1 is connected in parallel with the first off-capacitance C off1 , the second off-capacitance C off2 .

[0050] Figure 12 is an equivalent schematic diagram of the single-pole single-throw switch in the receiving mode provided by the present invention. As Figure 12 shown, when the single-pole single-throw switch is in the on state, the single-pole single-throw switch is equivalent to: a second on-resistance R on2 , a third on-resistance R on3 , and a third off-capacitance C off3 , where the second on-resistance R on2 and the third on-resistance R on3 are connected in series, and the third off-capacitance C off3 is connected in parallel with the second on-resistance R on2 , the third on-resistance R on3 .

[0051] Here, in the transmission mode, based on the impedance transformation network in the impedance transformation switch network, the impedance on the antenna side is made equal to the impedance on the main power amplifier side, realizing no power loss in the process of transmitting the output signal of the power amplifier and improving the conversion rate between the power on the main power amplifier side and the power on the antenna side; in the reception mode, based on the single-pole single-throw switch in the impedance transformation switch network, the isolation degree between the transmission link and the reception link can be improved, avoiding damage to the devices in the reception link caused by the leaked power. That is to say, in different operating modes, the working performance of the RF front-end system in different operating modes is improved through the impedance transformation switch network.

[0052] Aiming at the problems in the existing RF front-end system that the power and efficiency of the power amplifier in the millimeter-wave band are relatively low due to the switch insertion loss, and the overall bandwidth of the RF front-end system is limited by the bandwidth of the switch, the RF front-end system based on the impedance transformation switch network provided by the present invention uses the impedance transformation network instead of the switch in the transmission link to achieve the effects of no additional switch insertion loss and no bandwidth limitation for the signals in the transmission link, and sets a single-pole single-throw switch in the reception link to improve the isolation degree between the transmission link and the reception link. This way of changing the architecture of the RF front-end system can make the efficiency of the power amplifier be converted into the efficiency of the transmission link to the greatest extent, thereby reducing the system power consumption.

[0053] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A radio frequency front-end system based on an impedance transformation switch network, characterized in that, The radio frequency front-end system includes: a main power amplifier, a secondary power amplifier, a low-noise amplifier, a quarter-wavelength transmission line, an impedance transformation switch network, an antenna, a main power amplifier input interface, a secondary power amplifier input interface, and a low-noise amplifier output interface; Among them, the main power amplifier, the secondary power amplifier, the quarter-wavelength transmission line, the main power amplifier input interface, and the secondary power amplifier input interface are all located in the transmission link of the radio frequency front-end system, and the low-noise amplifier and the low-noise amplifier output interface are both located in the receiving link of the radio frequency front-end system; The first end of the main power amplifier is connected to the main power amplifier input interface, the first end of the secondary power amplifier is connected to the secondary power amplifier input interface, the second end of the secondary power amplifier is connected to the first end of the quarter-wavelength transmission line, and the second ends of the quarter-wavelength transmission line and the main power amplifier are both connected to the first end of the impedance transformation switch network; The first end of the low-noise amplifier is connected to the low-noise amplifier output interface, and the second end of the low-noise amplifier is connected to the second end of the impedance transformation switch network; The third end of the impedance transformation switch network is connected to the antenna; The impedance transformation switch network is used to improve the working performance of the radio frequency front-end system in different working modes; The impedance transformation switch network includes: an impedance transformation network and a single-pole single-throw switch; the impedance transformation network includes: an on-chip transformer, a first post-matching capacitor, and a second post-matching capacitor; the impedance transformation network is located in the transmission link, and the single-pole single-throw switch is located in the receiving link; The second end of the main power amplifier is connected to the first end of the on-chip transformer, and the second end of the quarter-wavelength transmission line is connected to the second end of the on-chip transformer; the third end of the on-chip transformer is connected to the first end of the first post-matching capacitor, and the fourth end of the on-chip transformer is grounded; the second ends of the first post-matching capacitor and the second post-matching capacitor are both connected to the antenna; the second end of the second post-matching capacitor is grounded; The first end of the single-pole single-throw switch is connected to the second end of the low-noise amplifier, and the second end of the single-pole single-throw switch is connected to the antenna; The different working modes of the radio frequency front-end system include a transmission mode and a receiving mode; When the radio frequency front-end system is in the transmission mode, the single-pole single-throw switch is in the off state, and the secondary power amplifier is grounded; through the impedance transformation network, the main power amplifier transmits a power amplifier output signal without additional switch insertion loss to the antenna, and the power amplifier output signal is obtained by processing the signal transmitted by the main power amplifier through the main power amplifier input interface; When the radio frequency front-end system is in the receiving mode, the main power amplifier and the secondary power amplifier are in the power amplifier off state, and the single-pole single-throw switch is in the on state; the low-noise amplifier sends the received electrical signal to the low-noise amplifier output interface.

2. The RF front-end system based on an impedance transformation switch network according to claim 1, characterized in that, When the radio frequency front-end system is in the transmission mode, the single-pole single-throw switch is in the off state, and the secondary power amplifier is grounded, the main power amplifier transmits a power amplifier output signal without additional switch insertion loss to the antenna in the following manner: Obtain the parasitic parameters of the main power amplifier and the equivalent inductance of the impedance transformation network; Utilize the parasitic parameters of the main power amplifier and the equivalent inductance of the impedance transformation network to determine the impedance transformation ratio of the impedance change network; Determine the coupling coefficient through the impedance transformation ratio; Utilize the ratio of the coupling coefficient and the number of turns of the on-chip transformer to adjust the number of turns of the on-chip transformer connected to the transmission link, and obtain the result that the impedance of the main power amplifier is equal to the impedance of the antenna; Based on the result that the impedance of the main power amplifier is equal to the impedance of the antenna, the main power amplifier transmits a power amplifier output signal without additional switching insertion loss to the antenna.

3. The RF front-end system based on an impedance transformation switch network according to claim 2, wherein The equivalent inductance of the impedance transformation network includes a first equivalent inductance and a second equivalent inductance, and the parasitic parameters of the main power amplifier include a first parasitic capacitance and a first parasitic inductance.

4. The RF front-end system based on the impedance transformation switch network according to claim 3, wherein, The step of utilizing the parasitic parameters of the main power amplifier and the equivalent inductance of the impedance transformation network to determine the impedance transformation ratio of the impedance change network includes: Equivalently combine the first parasitic inductance and the first equivalent inductance to obtain a first combined inductance; Perform Norton transformation on the first combined inductance and the second equivalent inductance to obtain the impedance transformation ratio of the impedance change network.

5. The RF front-end system based on an impedance transformation switch network according to claim 1, characterized in that, The single-pole single-throw switch includes a first transistor, a second transistor, and a third transistor; the first transistor and the second transistor are connected in series, and the third transistor is connected in parallel with the first transistor and the second transistor.

6. The RF front-end system based on the impedance transformation switch network according to claim 5, wherein When the single-pole single-throw switch is in the off state, the first transistor and the second transistor are off, and the third transistor is on; when the single-pole single-throw switch is in the on state, the first transistor and the second transistor are on, and the third transistor is off.

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