Variable attenuation network GaN broadband numerical control attenuator and radio frequency device

Abstract

The invention provides a variable attenuation network GaN broadband numerical control attenuator and a radio frequency device, and belongs to the technical field of microwave attenuators. The variable attenuation module comprises a first reference branch and a first attenuation branch which are connected in parallel. A plurality of resistors are arranged on the series branch and the parallel branch of the first attenuation branch, resistance value adjustment of the series branch and the parallel branch is achieved by controlling connection and short circuit of the resistors, and therefore one attenuation branch can achieve various attenuation amounts. According to the topological structure for realizing the multiple attenuations, the multiple attenuations are realized on the same attenuation branch, only one reference branch is required to be shared, and the number of the reference branches is reduced, so that the insertion loss in a reference state is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave attenuators, and in particular to a variable attenuation network GaN broadband digitally controlled attenuator and a radio frequency device. Background Art

[0002] Digitally controlled attenuators, also known as digitally controlled attenuators, are a crucial component of RF front-end transceiver (T / R) components. They are circuits that introduce predetermined attenuation within a specified frequency range, primarily used to control the amplitude of RF signals. GaAs MMIC (Gallium Arsenide Microwave Monolithic Integrated Circuit) attenuators, with their advantages of small size, light weight, high reproducibility, and reliability, have seen widespread use in T / R components in recent decades. However, GaAs MMIC attenuators no longer meet the higher power requirements of modern electronic devices, which demand high operating times, long operating times, and complex operating environments. With the advancement of wide-bandgap semiconductor materials and processes, the emergence of GaN MMIC attenuators is expected to address the power handling limitations of GaAs MMIC attenuators. Compared to GaAs, GaN has a wider bandgap, a higher breakdown electric field, and a greater electron saturation velocity. GaN HEMT devices offer an order of magnitude improvement in power handling compared to GaAs transistors.

[0003] Traditional multi-mode CNC attenuators typically connect multiple attenuators in series. Each attenuator has two states: a reference state and an attenuation state. The different attenuator state combinations achieve multiple different attenuation levels. For example, a 10dB attenuator and a 20dB attenuator can achieve attenuations of 0dB, 10dB, 20dB, and 30dB. While the reference state theoretically represents zero attenuation, in practice, the reference branch of the reference attenuator also experiences insertion loss. Therefore, when achieving multiple attenuations, the cumulative insertion loss of the reference branches of the multiple reference attenuators in existing multi-mode CNC attenuators is relatively large. Summary of the Invention

[0004] The present invention provides a variable attenuation network GaN broadband digitally controlled attenuator and a radio frequency device to solve the problem of large insertion loss of existing multi-digital controlled attenuators.

[0005] In a first aspect, the present invention provides a variable attenuation network GaN broadband digitally controlled attenuator, comprising: a radio frequency input terminal, a variable attenuation module, and a radio frequency output terminal connected in series;

[0006] The variable attenuation module includes a first reference branch and a first attenuation branch connected in parallel; wherein, in the reference state, the first reference branch is turned on and the first attenuation branch is turned off; in the attenuation state, the first reference branch is turned off and the first attenuation branch is turned on;

[0007] The first attenuation branch includes a first series branch, a first parallel branch, and a second parallel branch; one end of the first series branch is connected to the RF input terminal, and the other end is connected to the RF output terminal;

[0008] One end of the first parallel branch is connected to the RF input terminal, and the other end is grounded; one end of the second parallel branch is connected to the RF output terminal, and the other end is grounded;

[0009] The first series branch, the first parallel branch, and the second parallel branch each include a plurality of resistors connected in series;

[0010] The first attenuation branch is used to control the connection or short circuit of each resistor according to an external control signal in the attenuation state, so as to adjust the resistance values of the first series branch, the first parallel branch and the second parallel branch, thereby adjusting different attenuation states of the first attenuation branch.

[0011] In a possible implementation, the first series branch includes a resistor R11, a resistor R31, a resistor R32, and a resistor R12 connected in series in sequence;

[0012] The first parallel branch includes a resistor R21 and a resistor R41 connected in series;

[0013] The second parallel branch includes a resistor R22 and a resistor R42 connected in series;

[0014] The attenuation state of the first attenuation branch includes a first attenuation state or a second attenuation state;

[0015] In the first attenuation state, the resistors R11, R12, R21, R22, R41, and R42 are in an on state, and the resistors R31 and R32 are in a short-circuit state;

[0016] In the second attenuation state, the resistors R11 , R12 , R21 , R22 , R31 , and R32 are in an on state, and the resistors R41 and R42 are in a short-circuit state.

[0017] In a possible implementation, each of the resistors R31, R32, R41, and R42 is connected in parallel with a switch unit.

[0018] When the switch unit is disconnected, the parallel resistors are in a connected state; when the switch unit is turned on, the parallel resistors are in a short-circuit state.

[0019] In a possible implementation, the variable attenuation module further includes a phase compensation unit;

[0020] The first end of the phase compensation unit is connected between the resistor R31 and the resistor R32 , and the second end is suspended.

[0021] In a possible implementation, the phase compensation unit includes a switch unit and an open line connected in series from the first end to the second end.

[0022] In a possible implementation, the variable attenuation module is further connected in series with a fixed attenuation module.

[0023] In a possible implementation, the fixed attenuation module includes a second reference branch and a second attenuation branch connected in parallel;

[0024] The second attenuation branch includes a second series branch, a third parallel branch and a fourth parallel branch;

[0025] The second series branch includes a resistor R5; the third parallel branch includes a switch unit and a resistor R61 connected in series in sequence; and the fourth parallel branch includes a switch unit and a resistor R62 connected in series in sequence.

[0026] In a possible implementation, the fixed attenuation module further includes a phase compensation unit;

[0027] The first end of the phase compensation unit is connected between the input end of the fixed attenuation module and the second reference branch, and the second end is suspended.

[0028] In a possible implementation, the switch unit includes a plurality of GaN switch tubes connected in series, wherein the source of a preceding GaN switch tube is connected to the drain of a succeeding GaN switch tube.

[0029] In a second aspect, the present invention provides a radio frequency device comprising a GaN broadband digitally controlled attenuator with a variable attenuation network as described in any one of the possible implementations above.

[0030] The present invention provides a variable attenuation network GaN broadband digitally controlled attenuator and radio frequency device. The variable attenuation module of the present invention includes a first reference branch and a first attenuation branch connected in parallel. Multiple resistors are provided on the series branch and the parallel branch of the first attenuation branch. By controlling the connection and short circuit of each resistor, the resistance value of the series branch and the parallel branch can be adjusted, thereby enabling a single attenuation branch to achieve multiple attenuation values. Since the present invention implements a topological structure with multiple attenuation values, multiple attenuation values are achieved on the same attenuation branch, requiring only a shared reference branch. This reduces the number of reference branches and thus reduces the insertion loss in the reference state. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 1 is a schematic diagram of the structure of a traditional digitally controlled attenuator topology provided by an embodiment of the present invention;

[0033] Figure 2 This is a schematic structural diagram of a GaN broadband digitally controlled attenuator with a variable attenuation network provided by an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of an equivalent circuit of an attenuation network in a first attenuation state provided by an embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of an equivalent circuit of an attenuation network in a second attenuation state provided by an embodiment of the present invention;

[0036] Figure 5 is a structural diagram of a fixed attenuation module provided in an embodiment of the present invention;

[0037] Figure 6 is a schematic diagram of a switch tube provided by an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of the overall structure of another digitally controlled attenuator provided by an embodiment of the present invention;

[0039] Figure 8 This is a schematic structural diagram of a 20dB / 30dB attenuator provided by an embodiment of the present invention;

[0040] Figure 9 This is a diagram showing the insertion loss test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention;

[0041] Figure 10 This is a graph showing the full-state attenuation test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention;

[0042] Figure 11 This is a graph showing the full-state attenuation accuracy test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention;

[0043] Figure 12 This is a graph showing the attenuation accuracy RMS error test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention;

[0044] Figure 13This is a diagram showing additional phase shift test results for the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention;

[0045] Figure 14 This is a test curve diagram of the insertion loss variation of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention in a power withstand test;

[0046] Figure 15 This is a graph showing the input standing wave test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention;

[0047] Figure 16 This is a graph showing the output standing wave test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention;

[0048] Figure 17 This is the layout of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] To help those skilled in the art better understand this solution, the following will clearly describe the technical solutions in the embodiments of this solution in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of this solution, not all of it. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of this solution.

[0050] Throughout the specification, claims, and accompanying figures of this solution, the term "including" and any variations thereof mean "including, but not limited to," and are intended to cover non-exclusive inclusions and are not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish between different objects, not to describe a specific order.

[0051] The following is a detailed description of the implementation of the present invention with reference to the accompanying drawings:

[0052] Multi-channel CNC attenuators offer multiple attenuation settings, enabling a wide range of attenuation levels. To achieve this, multiple attenuators are typically connected in series. When connected in series, the total attenuation is equal to the algebraic sum of the attenuation levels of each individual attenuator. Different combinations of attenuator states can achieve a variety of attenuation levels. The following describes the topology of a traditional attenuator.

[0053] Figure 1 This is a schematic diagram of the structure of the traditional digital controlled attenuator topology provided by an embodiment of the present invention; Figure 1 , the attenuator topology is the traditional π-type attenuator topology. RF in It is the radio frequency input terminal, RF out is the RF output terminal; V P 、V Nis the attenuator control level, for example, V P is the voltage at the same direction terminal, V N is the reverse terminal voltage; M1 and M2 can be HEMT switches; R g This can be an external isolation resistor connected to the gate of the HEMT switch; R1 and R2 are the resistors of the attenuation network. The switching states of M1 and M2 control the reference and attenuation states of the attenuator. For example, for any attenuator, if M1 is on and M2 is off, the attenuator is in the reference state; otherwise, it is in the attenuation state.

[0054] Multiple attenuators can be connected in series to achieve multi-bit attenuation. Figure 1 The left side of the middle is a 10dB attenuator, and the right side is a 20dB attenuator, which can achieve attenuation of 0dB, 10dB, 20dB and 30dB.

[0055] When an attenuator is in the reference state, it theoretically does not produce attenuation, but in practice it will also produce insertion loss. For example, Figure 1 The attenuator on the left is in the reference state, and the attenuation state on the right. The total attenuation is the insertion loss on the left plus the attenuation on the right. When there are many attenuators, the total insertion loss of the reference branches of multiple attenuators can also be very large.

[0056] The present invention provides a GaN broadband digitally controlled attenuator with a variable attenuation network. By realizing multiple attenuation values on the same attenuation branch and sharing a reference branch, the reference branch is reduced, thereby reducing the total insertion loss in the reference state, thus solving the problem of high insertion loss in existing multi-digital controlled attenuators.

[0057] Figure 2 This is a schematic diagram of the structure of a variable attenuation network GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. Figure 2 , the attenuator includes: an RF input end, a variable attenuation module and an RF output end connected in series in sequence; the variable attenuation module includes a first reference branch and a first attenuation branch connected in parallel; wherein, in the reference state, the first reference branch is turned on and the first attenuation branch is disconnected; in the attenuation state, the first reference branch is disconnected and the first attenuation branch is turned on; the first attenuation branch includes a first series branch, a first parallel branch and a second parallel branch; one end of the first series branch is connected to the RF input end, and the other end is connected to the RF output end; one end of the first parallel branch is connected to the RF input end, and the other end is grounded; one end of the second parallel branch is connected to the RF output end, and the other end is grounded; the first series branch, the first parallel branch and the second parallel branch all include multiple resistors connected in series; the first attenuation branch is used to control the connection or short circuit of each resistor according to an external control signal in the attenuation state to achieve resistance value adjustment of the first series branch, the first parallel branch and the second parallel branch, thereby achieving different attenuation state adjustment of the first attenuation branch.

[0058] In some embodiments, the attenuator includes: an RF input, a variable attenuation module, and an RF output, connected in series. Exemplarily, the attenuator may also include other attenuation modules, such as other fixed attenuation modules connected in series, or multiple variable attenuation modules. Here, assuming only one variable attenuation module, the internal structure of the variable attenuation module will be described in detail.

[0059] In some embodiments, the variable attenuation module includes a first reference branch and a first attenuation branch connected in parallel.

[0060] Exemplarily, one end of the first reference branch is connected to the RF input terminal, and the other end is connected to the RF output terminal. Exemplarily, one end of the first attenuation branch is connected to the RF input terminal, and the other end is connected to the RF output terminal.

[0061] Furthermore, a switch module is provided at both ends of the first reference branch and the first attenuation branch, thereby controlling the conduction and disconnection of the first reference branch and the first attenuation branch. Exemplarily, in the reference state, the first reference branch is conducted and the first attenuation branch is disconnected; in the attenuation state, the first reference branch is disconnected and the first attenuation branch is conducted. The attenuator switches between the two transmission paths of the reference branch and the attenuation branch. The RF signal is transmitted through the reference branch or through the attenuation branch. The amplitude of the output signals of the two transmission paths changes according to the predetermined attenuation amount, thereby realizing the function of controlling the amplitude of the transmission signal. The specific structure of the attenuation branch is described below.

[0062] In some embodiments, the first attenuation branch includes a first series branch, a first parallel branch, and a second parallel branch; one end of the first series branch is connected to the RF input terminal and the other end is connected to the RF output terminal; one end of the first parallel branch is connected to the RF input terminal and the other end is grounded; one end of the second parallel branch is connected to the RF output terminal and the other end is grounded. It should be noted that the series branch and the two parallel branches form a π-type attenuator topology. The structures of the series branch and the parallel branch are described in detail below.

[0063] In some embodiments, the first series branch, the first parallel branch, and the second parallel branch each include a plurality of resistors connected in series.

[0064] It should be noted that the attenuation branch is usually provided with a resistor to generate attenuation of the signal and achieve a certain attenuation amount. Exemplarily, in the first series branch, the first parallel branch, and the second parallel branch, any branch is provided with multiple resistors. For example, any branch is provided with at least 2 resistors. Further, the multiple resistors of any branch are connected in series with each other. Further, the parallel branch is provided with 2 resistors, and the series branch is provided with 4 resistors. Exemplarily, in order to ensure impedance matching between the input end and the output end, the resistance values of the two parallel branches are the same. Further, the number of resistors in the two parallel branches is the same. The following describes the role of providing multiple resistors.

[0065] In some embodiments, the first attenuation branch is used to control the connection or short circuit of each resistor according to an external control signal in the attenuation state, thereby adjusting the resistance values of the first series branch, the first parallel branch, and the second parallel branch, and thereby adjusting different attenuation states of the first attenuation branch.

[0066] It should be noted that to control the connection or short-circuiting of resistors, switches can be connected in parallel to some of the resistors. External control signals can be applied to the switches connecting the resistors in parallel, thereby controlling the connection or short-circuiting of each resistor. The reason some resistors are controllable here is that to achieve a certain amount of attenuation, the resistance values in each branch do not need to be completely zero. Therefore, to ensure a certain resistance value, some resistors are always connected and do not need to be short-circuited. It should also be noted that connecting a resistor refers to connecting the resistor in series with the branch, which attenuates the signal; short-circuiting a resistor refers to short-circuiting the two ends of the resistor, preventing the signal from passing through the resistor and thus ignoring the signal attenuation. Controlling the connection or short-circuiting of each resistor is to adjust the resistance value of each branch. Adjusting the resistance value of each branch can change the attenuation of the first attenuation branch, thereby giving the first attenuation branch different attenuation states, that is, having multiple attenuation levels. For example, each attenuation level of the first attenuation branch is selectable. For example, there can be two attenuation levels: 20dB or 30dB.

[0067] The variable attenuation module of the present invention includes a first reference branch and a first attenuation branch connected in parallel. Multiple resistors are provided in both the series and parallel branches of the first attenuation branch. By controlling the connection and short-circuiting of each resistor, the resistance values of the series and parallel branches can be adjusted, thereby enabling a single attenuation branch to achieve multiple attenuation levels. Because the present invention implements a topological structure that achieves multiple attenuation levels on the same attenuation branch, only a single reference branch is required. This reduces the number of reference branches and thus reduces insertion loss in the reference state.

[0068] The following is a specific embodiment, referring to Figure 2 , explain the specific structure of the first attenuation branch.

[0069] In one possible implementation, the first series branch includes a resistor R11, a resistor R31, a resistor R32, and a resistor R12 connected in series in sequence; the first parallel branch includes a resistor R21 and a resistor R41 connected in series in sequence; the second parallel branch includes a resistor R22 and a resistor R42 connected in series in sequence; the attenuation state of the first attenuation branch includes a first attenuation state or a second attenuation state; in the first attenuation state, the resistors R11, R12, R21, R22, R41, and R42 are in a connected state, and the resistors R31 and R32 are in a short-circuit state; in the second attenuation state, the resistors R11, R12, R21, R22, R31, and R32 are in a connected state, and the resistors R41 and R42 are in a short-circuit state.

[0070] Exemplarily, in the direction from the input end to the output end, the first series branch includes resistors R11, R31, R32, and R12 connected in series. Exemplarily, in the direction toward ground, the first parallel branch includes resistors R21 and R41 connected in series, and the second parallel branch includes resistors R22 and R42 connected in series.

[0071] Figure 3 is a schematic diagram of an equivalent circuit of an attenuation network in the first attenuation state provided by an embodiment of the present invention; Figure 3 In the first attenuation state, the resistor R11, the resistor R12, the resistor R21, the resistor R22, the resistor R41 and the resistor R42 are in the connected state to achieve attenuation together.

[0072] Figure 4 is a schematic diagram of an equivalent circuit of an attenuation network in the second attenuation state provided by an embodiment of the present invention; Figure 4 In the second attenuation state, the resistor R11, the resistor R12, the resistor R21, the resistor R22, the resistor R31 and the resistor R32 are in the connected state to achieve attenuation together.

[0073] This embodiment of the present invention implements switching between attenuation states by providing resistors R11, R12, R21, and R22 with fixed connection states. Furthermore, two pairs of resistors with adjustable connection states are provided: R31 and R32, and R41 and R42. Selecting one of these two pairs allows for switching between attenuation states. Furthermore, because the resistance changes are symmetrical between the two parallel branches and between the input and output sides of the series branch, impedance matching between the input and output sides is ensured. The following describes the resistor switching process.

[0074] In a possible implementation, resistors R31, R32, R41, and R42 are each connected in parallel with a switch unit; when the switch unit is disconnected, the parallel resistors are in a connected state; when the switch unit is turned on, the parallel resistors are in a short-circuit state.

[0075] In the embodiment of the present invention, some resistors in the attenuation branch are connected in parallel with the switch unit, and the switching state of the resistors is switched by controlling the switch state of the switch unit.

[0076] In a possible implementation, the variable attenuation module further includes a phase compensation unit; a first end of the phase compensation unit is connected between the resistor R31 and the resistor R32, and a second end is suspended.

[0077] In a possible implementation, the phase compensation unit includes a switch unit and an open line connected in series from the first end to the second end.

[0078] The embodiment of the present invention improves the additional phase shift index by providing an open-circuit phase compensation unit in the variable attenuation module.

[0079] The variable attenuation module is described above. The digitally controlled attenuator in the embodiment of the present invention may include various attenuation modules, which are described in detail below.

[0080] In a possible implementation, the variable attenuation module is further connected in series with a fixed attenuation module.

[0081] It should be noted that the variable attenuation module is connected in series with the fixed attenuation module to cooperate with each other to achieve various attenuation amounts, which will be illustrated in the subsequent comprehensive embodiments.

[0082] Figure 5 Schematic diagram of the structure of the fixed attenuation module provided by the embodiment of the present invention. Figure 5 In one possible implementation, the fixed attenuation module includes a second reference branch and a second attenuation branch connected in parallel; the second attenuation branch includes a second series branch, a third parallel branch, and a fourth parallel branch; the second series branch includes a resistor R5; the third parallel branch includes a switch unit and a resistor R61 connected in series in sequence; and the fourth parallel branch includes a switch unit and a resistor R62 connected in series in sequence.

[0083] In a possible implementation, the fixed attenuation module further includes a phase compensation unit; a first end of the phase compensation unit is connected between the input end of the fixed attenuation module and the second reference branch, and a second end of the phase compensation unit is suspended.

[0084] The embodiment of the present invention improves the additional phase shift index by providing an open-circuit phase compensation unit in the fixed attenuation module.

[0085] In the above, the switch unit is mentioned in both the variable attenuation module and the fixed attenuation module. The switch unit is described below. Figure 6The diagram is a schematic diagram of a switch tube provided by an embodiment of the present invention. The left diagram is a schematic diagram of the structure of the switch tube, and the right diagram is a schematic diagram of the switch equivalent circuit. For example, the switch tube can be a GaN HEMT switch. The following is an example of a HEMT tube. The source (S electrode) and drain (D electrode) of the HEMT tube serve as the RF terminal, the gate (G electrode) serves as the control terminal, and the gate resistor R g Play the role of isolating the signal (R g The resistance is usually greater than 1.5KΩ. The HEMT switch can be equivalent to a variable resistor (R ds ) and a variable capacitor (C g ) in parallel. When the gate-source voltage V gs When it is zero, the HEMT switch can be regarded as the on state, R ds Very small, C g Large, the HEMT switch can be equivalent to the on-state resistance R ds ; When the gate-source voltage is reverse biased to exceed the pinch-off voltage V p (|V gs |>|V p |), the HEMT switch can be regarded as the off state, R ds Very big, C g Small, the HEMT switch can be equivalent to the off-state capacitance C g .

[0086] The power handling capability of the digital controlled attenuator is mainly determined by the GaN HEMT switch device. The larger the gate width of the HEMT switch, the stronger the power handling capability. When the gate width of the HEMT switch is larger, the equivalent resistance R ds The smaller the equivalent capacitance C g The bigger.

[0087] The circuit design of digital controlled attenuator needs to optimize the insertion loss, attenuation accuracy, standing wave, additional phase shift and other indicators at the same time. g It has a great influence on the phase of the attenuator. In order to obtain a better additional phase shift index, C g The capacitance value cannot be too large. Because the C g Larger, C g The larger the gate width, the greater the impact on the phase. Therefore, the gate width of the GaN HEMT device designed using the traditional attenuator topology is limited, thereby limiting the power handling capability of the digitally controlled attenuator.

[0088] In a possible implementation, the switch unit includes a plurality of GaN switch tubes connected in series, wherein the source of a preceding GaN switch tube is connected to the drain of a succeeding GaN switch tube.

[0089] The present invention can cascade GaN HEMT tubes multiple times, that is, the source and drain of two or more GaN HEMT tubes are connected in series. When in the open state, it is equivalent to the R of multiple HEMT switches. ds The HEMT switch in series (conducting) is equivalent to R ds ), the on-state resistance R ds ’ Enlarge (R ds ’ >R ds ); in the off state, it is equivalent to the C of multiple HEMT switches g The series (off HEMT switch is equivalent to C g ), the off-state capacitance C after series connection g ’ Smaller (C g ’ <C g In this way, the gate width of a single GaN HEMT tube can be increased, and the total off-state capacitance C of the series HEMT tubes can be increased. g ’ It will not get bigger, and the power handling capability of the digital controlled attenuator can be improved without deteriorating the performance such as insertion loss, attenuation accuracy, standing wave, and additional phase shift.

[0090] The technical concept of the present invention is described below using a comprehensive specific embodiment.

[0091] Due to the unique operating environments of modern electronic equipment, high-power, low-loss, compact, broadband digitally controlled attenuators are required to ensure the proper operation of T / R components. Currently, research on GaN high-power, low-loss, broadband digitally controlled attenuators by universities, research institutions, and semiconductor manufacturers at home and abroad is relatively limited. Publicly reported GaN digitally controlled attenuators struggle to simultaneously meet the requirements for high power handling, wide attenuation range, low insertion loss, compact size, high attenuation accuracy, and wide bandwidth.

[0092] Purpose of the present invention: The present invention aims to provide a broadband digitally controlled attenuator based on a GaN microwave monolithic integrated circuit (MMIC) process with high power handling capability, low insertion loss, compact size, and high attenuation accuracy. The GaN digitally controlled attenuator fabricated based on this invention primarily controls the amplitude of RF signals, i.e., amplitude modulation. It is widely applicable in systems such as communications and navigation, and is particularly well-suited for applications with high input power.

[0093] Problems to be solved by the embodiments of the present invention:

[0094] 1) The power handling capability of GaAs digitally controlled attenuators is usually less than 30dBm, and the power handling capability of GaN broadband digitally controlled attenuators that can be used in engineering is not high enough.

[0095] 2) The insertion loss of a one-bit GaN digitally controlled attenuator is about 4dB@18GHz, and the insertion loss of a six-bit GaN digitally controlled attenuator is about 5.5dB@18GHz. The insertion loss of GaN broadband digitally controlled attenuator products is relatively large.

[0096] The solution of the embodiment of the present invention is as follows:

[0097] 1) Multiple cascading of high-power devices: By cascading GaN HEMT tubes in the GaN attenuator topology, the power handling capability of the GaN HEMT tubes is improved while ensuring the main electrical properties of the attenuator remain unchanged. GaN HEMT devices are selected to improve the power handling capability of the MMIC digitally controlled attenuator.

[0098] 2) Variable attenuation network attenuator topology: By changing the resistance value of the attenuation network in the traditional switch-type attenuator topology, two different basic bit attenuations can be achieved in one attenuator topology to reduce the number of cascaded bits of the attenuator, thereby reducing the insertion loss and chip size of the digitally controlled attenuator.

[0099] The above technical solution reduces the number of bits of a traditional digitally controlled attenuator and realizes two different basic bit attenuation amounts in one attenuator topology.

[0100] Figure 7 This is a schematic diagram of the overall structure of another digital controlled attenuator provided by an embodiment of the present invention. Figure 7 The digital controlled attenuator includes 20dB / 30dB position attenuator (corresponding to variable attenuation module) and 10dB position attenuator (corresponding to fixed attenuation module).

[0101] For example, the operating frequency range of the digital controlled attenuator is 0.3 GHz to 18 GHz; the control voltage (V T1 ~V T6 )0V / -28V. In the RF transmission direction, the attenuation bits are cascaded from left to right in the order of 20dB / 30dB bit, 10dB bit. The control voltage corresponding to the 10dB bit is V T1 、V T2 , the control voltage corresponding to the 20dB / 30dB position is V T3 、V T4 、V T5 、V T6 The control logic truth table is shown in the following table, where "0" represents a low level of -28V and "1" represents a high level of 0V. The 0dB state is the reference state.

[0102] Attenuation <![CDATA[V T1 ]]> <![CDATA[V T2 ]]> <![CDATA[V T3 ]]> <![CDATA[V T4 ]]> <![CDATA[V T5 ]]> <![CDATA[V T6 ]]> 0dB 1 0 1 0 1 0 10dB 0 1 1 0 1 0 20dB 1 0 0 1 1 0 30dB 1 0 0 1 0 1 40dB 0 1 0 1 0 1

[0103] In this embodiment of the present invention, a 10dB attenuator and a 20dB / 30dB attenuator are designed separately and then cascaded. Each attenuation position has a control line connected to it. By applying a control voltage to these lines according to the truth table above, the attenuation of a particular position can be increased or decreased, thereby achieving attenuation in steps of 10dB within the range of 0 to 40dB.

[0104] For example, each attenuator may be composed of a GaN HEMT switch device and an attenuation network.

[0105] The following first describes the 10dB attenuator. Figure 5 In some embodiments, the 10dB attenuator of the present invention is a novel π-type attenuator topology. in It is the radio frequency input terminal, RF out is the RF output terminal; V P 、V N is the attenuator control level, V P is the voltage at the same direction terminal, V N is the reverse terminal voltage; M1, M2, and M3 are HEMT switches; TLO1 is an open circuit; R g The external isolation resistor for the HEMT switch gate is R1, while R2 represents the attenuation network resistors. M1 and M3 are cascaded in a 2x fashion, while M2 is cascaded in a 6x fashion. Multiple cascades are used to improve the attenuator's power handling capability. M3 and open-circuit TLO1 form a phase compensation circuit to improve the additive phase shift.

[0106] The following describes the 20dB / 30dB attenuator. Figure 8 Schematic diagram of the structure of the 20dB / 30dB attenuator provided by the embodiment of the present invention. Figure 8 In some embodiments, RF in It is the radio frequency input terminal, RF out is the RF output terminal; V P1 、V N1 、V P2 、V N2 is the attenuator control level, V P1 、V P2 is the voltage at the same direction terminal, V N1 、V N2 is the reverse terminal voltage; M1, M2, M3, M4, M5, M6, and M7 are HEMT switches; TL1 is a microstrip line; TLO1 is an open line; R gis the external isolation resistor of the HEMT switch gate; R1, R2, R3, and R4 are the resistors of the attenuation network. Among them, M1, M2, M3, M4, M5, and M6 tubes are cascaded twice to improve the power handling capability of the attenuator. The M6 tube and the open line TLO1 form a phase compensation circuit to improve the additional phase shift index. The M1 to M4 tubes form two groups of single-pole double-throw switches to select different paths. The M5 to M7 tubes act on the attenuation network to change the impedance of the attenuation network. When the M5 tube is turned on and the M6 and M7 tubes are turned off, we get Figure 3 The attenuation network shown in the figure; when the M5 tube is turned off and the M6 and M7 tubes are turned on, we get Figure 4 The attenuation network is shown.

[0107] The following describes the control method of each switch tube.

[0108] When V P1 =-28V, V N1 =0V, M1 and M4 are turned on, M3 and M2 are turned off, and the 20dB / 30dB attenuation position is at the reference state.

[0109] When V P1 =0V, V N1 =-28V, M1 and M4 are turned off, M3 and M2 are turned on, and the 20dB / 30dB attenuation position selects the attenuation branch. At this time, when V P2 =-28V, V N2 =0V, M5 is turned on, M6 and M7 are turned off, and the 20dB / 30dB attenuation position is at the 20dB attenuation state. The equivalent circuit diagram of the attenuation network is as follows: Figure 3 As shown; when V P2 =0V, V N2 =-28V, M5 is turned off, M6 and M7 are turned on, and the 20dB / 30dB attenuation position is at the 30dB attenuation state. The equivalent circuit diagram of the attenuation network is as follows: Figure 4 shown.

[0110] Figure 3 The impedance ratio of the attenuation network shown is Figure 4 The impedance of the attenuation network shown is small, and the insertion loss generated by the attenuation network is also small. Figure 3 The attenuation network can be designed to produce a 20dB attenuator. Figure 4 The attenuation network can be designed to create a 30dB bit attenuator, achieving two different basic bit attenuation amounts in one attenuator topology, combining two attenuation bits into one. The shared reference branch effectively reduces the insertion loss of the digitally controlled attenuator, and the reduced number of attenuator bits reduces the chip size.

[0111] Figure 3 and Figure 4The comparison shows that changes in the attenuation network alter the insertion loss of the attenuator's attenuation branch. The attenuation is determined by comparing the insertion loss of the attenuation branch with the insertion loss of the reference branch. Since they share the same reference branch, the variable attenuation network attenuator can achieve two different attenuation levels.

[0112] Because the reference state of 20dB and 30dB attenuation bits is shared Figure 8 The insertion loss in the reference state is the same for the M1 and M2 transistors and the microstrip line TL1. If the traditional design method is used—designing 20dB and 30dB attenuation stages separately and then cascading them together—the insertion loss and circuit size will both be roughly doubled.

[0113] It can be seen that by designing a digitally controlled attenuator using the novel variable attenuation network attenuator topology of the present invention, two different basic bit attenuations can be achieved in one attenuator topology, which can effectively reduce the insertion loss and chip size of the digitally controlled attenuator.

[0114] The variable attenuation network high-power low-loss GaN broadband digitally controlled attenuator manufactured by the present invention has five attenuation states (0 / 10 / 20 / 30 / 40dB), a minimum attenuation step of 10dB, a maximum attenuation of 40dB, and a power handling capability of 10W (40dBm). Test results within the frequency range of 0.3GHz to 18GHz show: insertion loss of 3.3dB, attenuation accuracy of -1.0dB to 1.9dB, attenuation accuracy RMS error of less than 1.5dB, additional phase shift of -9° to 13°, and input and output standing waves of less than 1.5. The control level is 0V / -28V, and the chip size is 2.30mm×1.20mm×0.08mm. The main electrical performance test curves are shown in the figure. Figures 9 to 16 .

[0115] Figure 9 This is a graph showing the insertion loss test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. Insertion loss refers to the loss when the attenuator is placed in the reference state (0dB state) according to the truth table. In the frequency range of 0.3GHz to 18GHz, the insertion loss of the GaN digitally controlled attenuator is less than 3.3dB, achieving low loss. Compared with the publicly reported GaN one-bit attenuator, its insertion loss is smaller, and the GaN broadband digitally controlled attenuator of the present invention has more attenuation states and more complex functions; compared with the publicly reported GaN six-bit attenuator, the insertion loss of the GaN digitally controlled attenuator of the present invention is smaller. Although the number of attenuation bits is not as many as the GaN six-bit attenuator, the attenuation of the basic bit is large, the topological structure is complex, and the design of the insertion loss index is difficult.

[0116] Figure 10This is a graph showing the full-state attenuation test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. The full state includes: 0dB, 10dB, 20dB, 30dB, and 40dB. The attenuation is the difference between the insertion loss of the attenuated state and the insertion loss of the reference state. Within the frequency range of 0.3GHz to 18GHz, the attenuator of the present invention can achieve amplitude adjustment with a minimum step of 10dB and a maximum attenuation of 40dB. The full-state attenuation is relatively flat, indicating that the GaN broadband digitally controlled attenuator has good broadband amplitude modulation performance.

[0117] Figure 11 This figure shows the full-state attenuation accuracy test results for the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. Attenuation accuracy refers to the difference between the attenuation in each attenuation state of the attenuator and the corresponding nominal value. Within the frequency range of 0.3 GHz to 18 GHz, the attenuation accuracy for all attenuation states ranges from -1.0 dB to 1.9 dB, with a small deviation from the nominal value, indicating that the present invention achieves broadband amplitude modulation performance.

[0118] Figure 12 This figure shows the attenuation accuracy RMS error test results for the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. The attenuation accuracy RMS error is the root mean square error (RMS) of the attenuation accuracy. Within the 0.3 GHz to 18 GHz frequency range, the attenuation accuracy RMS error is less than 1.5 dB, demonstrating the high attenuation accuracy of the GaN broadband digitally controlled attenuator.

[0119] Figure 13 This figure shows the test results for the additive phase shift of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. The additive phase shift refers to the difference between the phase of each attenuation state of the attenuator and the phase of the reference state. Within the frequency range of 0.3 GHz to 18 GHz, the additive phase shift ranges from -9° to 13°, indicating that the attenuator of the present invention achieves a small additive phase shift across a wide frequency band.

[0120] Figure 14 This is a test curve of the insertion loss variation of the GaN broadband digitally controlled attenuator provided by the embodiment of the present invention. The GaN broadband digitally controlled attenuator is boxed and tested. A =25℃,V T1 ~V T6 Power on according to the truth table. Before the test, the insertion loss of the attenuator was tested under the condition of input power 0dBm; a power resistance test was carried out with an input power of 40dBm (10W) and working for 30 minutes. After the test was completed, an endpoint electrical test was carried out to measure the insertion loss of the attenuator. The absolute value of the difference in insertion loss before and after the test is the change in insertion loss. In the frequency range of 0.3GHz to 18GHz, the change in insertion loss before and after the power resistance test is less than 1dB. This means that the GaN broadband digitally controlled attenuator of the present invention is not damaged after working for a long time at high input power, and the power resistance performance reaches 10W.

[0121] Figure 15 This is a graph showing the input standing wave test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. Figure 16 This is a graph showing the output standing wave test results of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. Both the input and output standing waves are less than 1.5, indicating that the broadband matching performance of the GaN broadband digitally controlled attenuator of the present invention is good.

[0122] Figure 17 This is the layout of the GaN broadband digitally controlled attenuator provided by an embodiment of the present invention. This GaN broadband digitally controlled attenuator, fabricated in accordance with the present invention, utilizes a variable attenuation network topology and multiple cascades of high-power-stable devices, achieving a power handling capability of 10W. Within the 0.3GHz to 18GHz frequency range, the measured insertion loss is less than 3.3dB, demonstrating low loss. Furthermore, it achieves high attenuation accuracy, minimal additional phase shift, and a compact size, meeting the requirements of engineering applications.

[0123] The following table shows the test results and performance statistics of more GaN broadband digitally controlled attenuators:

[0124]

[0125] Statistics of power withstand test results of GaN broadband digitally controlled attenuators:

[0126]

[0127] Through the analysis of test and experimental data, the GaN broadband digitally controlled attenuator of the present invention can effectively improve the power resistance performance of the digitally controlled attenuator and has a smaller insertion loss, thereby effectively enhancing the system's higher requirements for high-power and long-term operation of the chip.

[0128] The novel π-type attenuator topology and the novel variable attenuation network attenuator topology of the present invention can be applied to other compound semiconductor processes such as GaAs. The high-power, low-loss GaN broadband digitally controlled attenuator produced using the present invention has broad application prospects in modern communications, navigation, and other systems.

[0129] In a second aspect, the present invention provides a radio frequency device, comprising a variable attenuation network GaN broadband digitally controlled attenuator as in any possible implementation described above.

[0130] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A variable attenuation network GaN broadband digitally controlled attenuator, characterized in that: include: A radio frequency input terminal, a variable attenuation module, and a radio frequency output terminal connected in series; The variable attenuation module includes a first reference branch and a first attenuation branch connected in parallel; wherein, in the reference state, the first reference branch is turned on and the first attenuation branch is turned off; in the attenuation state, the first reference branch is turned off and the first attenuation branch is turned on; The first attenuation branch includes a first series branch, a first parallel branch, and a second parallel branch; one end of the first series branch is connected to the RF input terminal, and the other end is connected to the RF output terminal; One end of the first parallel branch is connected to the RF input terminal, and the other end is grounded; one end of the second parallel branch is connected to the RF output terminal, and the other end is grounded; The first series branch, the first parallel branch, and the second parallel branch each include a plurality of resistors connected in series; The first attenuation branch is used to control the connection or short circuit of each resistor according to an external control signal in the attenuation state, so as to adjust the resistance values of the first series branch, the first parallel branch and the second parallel branch, thereby adjusting different attenuation states of the first attenuation branch.

2. The variable attenuation network GaN broadband digitally controlled attenuator according to claim 1, characterized in that: The first series branch includes a resistor R11, a resistor R31, a resistor R32 and a resistor R12 connected in series in sequence; The first parallel branch includes a resistor R21 and a resistor R41 connected in series; The second parallel branch includes a resistor R22 and a resistor R42 connected in series; The attenuation state of the first attenuation branch includes a first attenuation state or a second attenuation state; In the first attenuation state, the resistors R11, R12, R21, R22, R41, and R42 are in an on state, and the resistors R31 and R32 are in a short-circuit state; In the second attenuation state, the resistors R11 , R12 , R21 , R22 , R31 , and R32 are in an on state, and the resistors R41 and R42 are in a short-circuit state.

3. The variable attenuation network GaN broadband digitally controlled attenuator according to claim 2, characterized in that: The resistor R31, the resistor R32, the resistor R41 and the resistor R42 are each connected in parallel with a switch unit; When the switch unit is disconnected, the parallel resistors are in a connected state; when the switch unit is turned on, the parallel resistors are in a short-circuit state.

4. The variable attenuation network GaN broadband digitally controlled attenuator according to claim 2, characterized in that: The variable attenuation module further includes a phase compensation unit; The first end of the phase compensation unit is connected between the resistor R31 and the resistor R32 , and the second end is suspended.

5. The variable attenuation network GaN broadband digitally controlled attenuator according to claim 4, characterized in that: The phase compensation unit includes a switch unit and an open line connected in series from the first end to the second end.

6. The variable attenuation network GaN broadband digitally controlled attenuator according to claim 1, characterized in that: The variable attenuation module is further connected in series with a fixed attenuation module.

7. The variable attenuation network GaN broadband digitally controlled attenuator according to claim 6, characterized in that: The fixed attenuation module includes a second reference branch and a second attenuation branch connected in parallel; The second attenuation branch includes a second series branch, a third parallel branch and a fourth parallel branch; The second series branch includes a resistor R5; the third parallel branch includes a switch unit and a resistor R61 connected in series in sequence; and the fourth parallel branch includes a switch unit and a resistor R62 connected in series in sequence.

8. The variable attenuation network GaN broadband digitally controlled attenuator according to claim 6, characterized in that: The fixed attenuation module further includes a phase compensation unit; The first end of the phase compensation unit is connected between the input end of the fixed attenuation module and the second reference branch, and the second end is suspended.

9. The variable attenuation network GaN broadband digitally controlled attenuator according to any one of claims 3, 5 or 7, characterized in that: The switch unit includes a plurality of GaN switch tubes connected in series, wherein the source of a preceding GaN switch tube is connected to the drain of a succeeding GaN switch tube.

10. A radio frequency device, characterized in that: A GaN broadband digitally controlled attenuator comprising a variable attenuation network according to any one of claims 1 to 9.

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