Numerical control attenuator with low insertion loss

Abstract

The invention discloses a digital control attenuator with low insertion loss. The digital control attenuator comprises a radio frequency input port, a radio frequency output port, a switch module and an attenuation module, the switch module comprises first to fifth switch tubes, the other end of the first switch tube is grounded, two ends of the first switch tube are connected in parallel with a first resistor, the other end of the fifth switch tube is grounded, and two ends of the fifth switch tube are connected in parallel with a second resistor; two ends of the third switch tube are connected with a radio frequency input port and a radio frequency output port; one end of the attenuation module is connected to the radio frequency output port through a second switch tube, and the other end of the attenuation module is connected to the radio frequency input port through a fourth switch tube; or the attenuation module is connected to the two ends of the third switch tube in parallel; or the number of the attenuation modules is two, one attenuation module is connected between the first switch tube and the second switch tube in series, and the other attenuation module is connected between the fourth switch tube and the fifth switch tube in series. The numerical control attenuator is small in ground state insertion loss and can be used for large dynamic amplitude regulation and control at the input end of a receiver, and the overall noise of a receiving channel is reduced.

Description

Technical Field

[0001] The invention belongs to the field of radio frequency microwaves and relates to attenuator devices, in particular to a digitally controlled attenuator with low insertion loss. Background Art

[0002] In phased array antennas and beamforming systems, attenuators are used as control elements to precisely change the signal amplitude, and can adjust the sidelobe level and beam width. The main technical indicators of attenuators include: operating frequency band, insertion loss, insertion loss fluctuation, voltage standing wave ratio, power capacity, attenuation, attenuation accuracy, attenuation additional phase shift, attenuator switching time, etc. However, the insertion loss of traditional large-bit attenuators is relatively large, and they will bring greater noise when used at the receiving end. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a low insertion loss digitally controlled attenuator, which has a small base state insertion loss and can be used at the input end of a receiver to perform large dynamic amplitude regulation and reduce the overall noise of the receiving channel.

[0004] Technical solution: A low insertion loss digitally controlled attenuator of the present invention comprises an RF input port, an RF output port, a switch module and an attenuation module; the switch module comprises a first switch tube SW1, a second switch tube SW2, a third switch tube SW3, a fourth switch tube SW4 and a fifth switch tube SW5 which are sequentially connected in series, wherein the other end of the first switch tube SW1 is grounded, a first resistor R1 is connected in parallel at both ends of the first switch tube SW1, the other end of the fifth switch tube SW5 is grounded, and a second resistor R2 is connected in parallel at both ends of the fifth switch tube SW5; both ends of the third switch tube SW3 are connected to the RF input port and the RF output port; one end of the attenuation module is connected to the RF output port through the second switch tube SW2, and the other end thereof is connected to the RF input port through the fourth switch tube SW4; or the attenuation module is connected in parallel at both ends of the third switch tube SW3; or there are two attenuation modules, one of which is connected in series between the first switch tube SW1 and the second switch tube SW2, and the other is connected in series between the fourth switch tube SW4 and the fifth switch tube SW5.

[0005] Further, when one end of the attenuation module is connected to the RF output port through the second switch tube SW2, and the other end thereof is connected to the RF input port through the fourth switch tube SW4, the attenuation module includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6;

[0006] The third resistor R3 and the fourth resistor R4 are connected to each other through a microstrip line TL1, one end of the third resistor R3 is grounded via a fifth resistor R5, and the other end thereof is connected to the RF output port via a second switch tube SW2; one end of the fourth resistor R4 is grounded via a sixth resistor R6, and the other end thereof is connected to the RF input port via a fourth switch tube SW4.

[0007] Furthermore, two ends of the fifth resistor R5 and two ends of the sixth resistor R6 are respectively connected in parallel to a phase compensation structure, which can eliminate the phase imbalance phenomenon caused by the base state and the attenuation state.

[0008] Furthermore, the phase compensation structure uses capacitors or inductors.

[0009] Furthermore, the third resistor R3, the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 together form a Π-type attenuation network.

[0010] Further, when the attenuation module is connected in parallel at both ends of the third switch tube SW3, the attenuation module includes a third resistor R3 and a fourth resistor R4 connected in series through the microstrip line TL1;

[0011] The other end of the third resistor R3 is connected to the RF output port, and the other end of the fourth resistor R4 is connected to the RF input port.

[0012] Further, when there are two attenuation modules, one of which is connected in series between the first switch tube SW1 and the second switch tube SW2, and the other is connected in series between the fourth switch tube SW4 and the fifth switch tube SW5, the attenuation module includes a third resistor R3 and a fourth resistor R4;

[0013] One end of the third resistor R3 is connected to the first switch tube SW1, and the other end thereof is connected to the second switch tube SW2 and the first resistor R1 respectively;

[0014] One end of the fourth resistor R4 is connected to the fourth switch tube SW4 and the second resistor R2 respectively, and the other end thereof is connected to the fifth switch tube SW5; the third resistor R3 and the fourth resistor R4 are connected via a microstrip line TL1.

[0015] Furthermore, the switch module as a whole constitutes a single-pole single-throw absorptive switch.

[0016] Furthermore, the third switch tube SW3 , the first switch tube SW1 , the fifth switch tube SW5 , the second switch tube SW2 , and the fourth switch tube SW4 are controlled by a pair of complementary TTL levels.

[0017] The digital controlled attenuator is designed based on a gallium arsenide process, a CMOS process or a GeSi process.

[0018] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows:

[0019] By simplifying the traditional single-pole double-throw switch into a single-pole single-throw absorptive switch, there is only the third switch tube SW3 between the RF input port and the RF output port. When turned on, the ground state insertion loss is only caused by the third switch tube SW3, and the insertion loss can be reduced by nearly half compared with the traditional structure; when turned off, the first switch tube SW1 and the first resistor R1, the fifth switch tube SW5 and the second resistor R2 together constitute an absorptive switch, ensuring good input-output matching in the attenuation state.

[0020] When realizing large attenuation positions, the low insertion loss digitally controlled attenuator has small base state insertion loss, simple structure and small area. It can be used at the receiver input for large dynamic amplitude regulation, which can reduce the overall noise of the receiving channel and improve the sensitivity of the receiving system.

[0021] Designed using GaAs technology, it is easy to integrate with GaAs chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A circuit topology diagram of a low insertion loss digitally controlled attenuator disclosed in an embodiment of the present invention;

[0023] Figure 2 A circuit topology diagram of a digitally controlled attenuator with low insertion loss when the attenuation module disclosed in an embodiment of the present invention is added inside a switch module;

[0024] Figure 3 It is a circuit topology diagram of a digitally controlled attenuator with low insertion loss when the attenuation module disclosed in an embodiment of the present invention is added to both ends of the third switch tube S;

[0025] Figure 4 A graph showing the relationship between input standing wave and frequency of a low insertion loss digitally controlled attenuator circuit disclosed in an embodiment of the present invention;

[0026] Figure 5 A diagram showing the relationship between the output standing wave and the frequency of a low insertion loss digitally controlled attenuator circuit disclosed in an embodiment of the present invention;

[0027] Figure 6 A diagram showing the relationship between insertion loss and frequency of a low insertion loss digitally controlled attenuator circuit disclosed in an embodiment of the present invention;

[0028] Figure 7 The diagram is a relationship between attenuation and frequency of a low insertion loss digitally controlled attenuator circuit disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described in detail below in conjunction with specific implementation methods and the accompanying drawings of the specification.

[0030] Example 1

[0031] like Figure 1As shown, the insertion loss digital controlled attenuator of the present invention includes a radio frequency input port, a radio frequency output port, a switch module and an attenuation module. The switch module includes a first switch tube SW1, a second switch tube SW2, a third switch tube SW3, a fourth switch tube SW4, and a fifth switch tube SW5 which are sequentially connected in series; wherein the other end of the first switch tube SW1 is grounded, a first resistor R1 is set in parallel at both ends of the first switch tube SW1, the other end of the fifth switch tube SW5 is grounded, and a second resistor R2 is set in parallel at both ends of the fifth switch tube SW5. The two ends of the third switch tube SW3 are connected to the radio frequency input port and the radio frequency output port. The switch module as a whole constitutes a single-pole single-throw absorptive switch to ensure the input and output matching characteristics of the attenuation state. The attenuation module is connected to the radio frequency input port and the radio frequency output port through the second switch tube SW2 and the fourth switch tube SW4 to realize the circuit attenuation function. The first switch tube SW1 and the first resistor R1, the fifth switch tube SW5 and the second resistor R2 together constitute an absorptive switch to ensure good port matching in the attenuation state.

[0032] The third switch tube SW3 , the first switch tube SW1 , the fifth switch tube SW5 , the second switch tube SW2 , and the fourth switch tube SW4 are controlled by a pair of complementary TTL levels.

[0033] The first switch tube SW1, the third switch tube SW3, and the fifth switch tube SW5 are turned on, and the second switch tube SW2 and the fourth switch tube SW4 are turned off, which is the base state; the first switch tube SW1, the third switch tube SW3, and the fifth switch tube SW5 are turned off, and the second switch tube SW2 and the fourth switch tube SW4 are turned on, which is the attenuation state.

[0034] In the attenuation state, since the first resistor R1 and the second resistor R2 are grounded, the matching characteristics of the RF output port and the RF input port can be ensured.

[0035] One end of the attenuation module is connected to the RF output port through the second switch tube SW2, and the other end thereof is connected to the RF input port through the fourth switch tube SW4. In this case, the attenuation module includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6. The third resistor R3 and the fourth resistor R4 are interconnected through a microstrip line TL1, one end of the third resistor R3 is grounded through the fifth resistor R5, and the other end thereof is connected to the RF output port through the second switch tube SW2. One end of the fourth resistor R4 is grounded through the sixth resistor R6, and the other end thereof is connected to the RF input port through the fourth switch tube SW4.

[0036] The third resistor R3, the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 together constitute a Π-type attenuation network, that is, the attenuation module is composed of a Π-type attenuation network. The off-state capacitance of the third resistor R3 in the off state is equivalent to a high-pass filter, resulting in a phase imbalance between the base state and the attenuation state. In order to eliminate this imbalance, a capacitive phase compensation structure is added in the attenuation state. In this embodiment, a phase compensation structure is connected in parallel at both ends of the fifth resistor R5 and the sixth resistor R6. The phase compensation structure can be a capacitive phase compensation structure, which is composed of a capacitor, or it can be an inductive phase compensation structure, which is composed of an inductor; in this embodiment, both phase compensation structures are composed of capacitors, including a first capacitor C1 and a second capacitor C2, and the two ends of the first capacitor C1 are connected to the two ends of the fifth resistor R5, and the two ends of the second capacitor C2 are connected to the two ends of the sixth resistor R6. In this embodiment, there is only one third switch tube SW3 on the series common branch, and compared with the attenuation structure of the traditional single-pole double-throw switch, the base state insertion loss can be reduced to half of the original.

[0037] The digital controlled attenuator of the present invention can be designed based on a gallium arsenide process, and can also be designed based on a CMOS process or a GeSi process.

[0038] The structure of using a single-pole single-throw absorptive switch to control the switching of the base state and attenuation state paths overcomes the problem of using a single-pole double-throw switch as a control switch in the prior art, which occupies a large chip area and introduces large insertion loss and additional phase shift in the signal path, thereby optimizing the insertion loss and additional phase shift. Compared with the traditional digital attenuator structure using two switching tubes, the structure significantly reduces the insertion loss while ensuring key indicators such as additional phase shift and attenuation accuracy.

[0039] The path switching between the base state and the attenuation state is realized by a single-pole single-throw absorptive switch. The on-resistance on the series path can be significantly reduced by using a single switch tube (the third switch tube SW3). While maintaining the commonly used digital attenuator topology and not increasing the complexity of the control module, the proposed attenuator structure has a conduction characteristic with low insertion loss in a large attenuation range, and does not increase the chip area, which is easy to implement. It is creative and feasible in radio frequency microwave integrated circuits.

[0040] Example 2

[0041] In addition to the attenuation module disclosed in Embodiment 1 being connected to both ends of the second switch tube SW2 and the fourth switch tube SW4 in the switch module, the attenuation module can also be arranged inside the switch module. The basic principle is the same as that of Embodiment 1. Figure 2As shown, there are two attenuation modules, one of which is connected in series between the first switch tube SW1 and the second switch tube SW2, and the other is connected in series between the fourth switch tube SW4 and the fifth switch tube SW5. The attenuation module includes a third resistor R3 and a fourth resistor R4. One end of the third resistor R3 is connected to the first switch tube SW1, and the other end thereof is connected to the second switch tube SW2 and the first resistor R1 respectively; one end of the fourth resistor R4 is connected to the fourth switch tube SW4 and the second resistor R2 respectively, and the other end thereof is connected to the fifth switch tube SW5. The third resistor R3 and the fourth resistor R4 are connected via a microstrip line TL1.

[0042] The third switch tube SW3, the first switch tube SW1, the fifth switch tube SW5 and the second switch tube SW2, the fourth switch tube SW4 are controlled by a pair of complementary TTL levels. The first switch tube SW1, the third switch tube SW3, the fifth switch tube SW5 are turned on, and the second switch tube SW2, the fourth switch tube SW4 are turned off, which is the base state; the first switch tube SW1, the third switch tube SW3, the fifth switch tube SW5 are turned off, and the second switch tube SW2, the fourth switch tube SW4 are turned on, which is the attenuation state. In the attenuation state, the first resistor R1 and the second resistor R2 are connected to the ground to ensure the matching characteristics of the RF output and RF input ports, and the third resistor R3 and the fourth resistor R4 together constitute an attenuation module to ensure the required attenuation.

[0043] Example 3

[0044] The basic principle of the digital controlled attenuator in this embodiment is the same as that in Embodiment 1. The difference between this embodiment and Embodiment 1 is that: Figure 3 As shown, the attenuation module is connected in parallel at both ends of the third switch tube SW3. The attenuation module includes a third resistor R3 and a fourth resistor R4 connected in series through a microstrip line TL1. The other end of the third resistor R3 is connected to the RF output port, and the other end of the fourth resistor R4 is connected to the RF input port. The base state and the attenuation state are selected by the switch tube, and the attenuation or signal absorption is achieved by using the resistor element, so as to achieve the amplitude and phase requirements of the attenuation state and the base state.

[0045] The attenuation module in the low insertion loss digitally controlled attenuator proposed by the present invention can be connected not only to the two ends of the two parallel switch tubes SW2 and SW4 in the switch module, but also between other switch tubes in the switch module, or inside the switch module. This article provides some but not all examples, these circuits use switching switches and resistor elements to achieve attenuation or signal absorption, and achieve the amplitude and phase requirements of the attenuation state and the base state.

[0046] In this embodiment, the attenuation module is composed of a single Π-type attenuation network. In addition, the attenuation module can also be composed of two Π-type attenuation networks. The attenuation module can be composed not only of a Π-type attenuation network, but also of a T-type attenuation network.

[0047] In the structure with large attenuation, the low insertion loss digitally controlled attenuator of the present invention reduces the insertion loss while having a simpler structure and occupies a smaller area compared to the traditional digitally controlled attenuator structure, and can be applied in large-position attenuator topology structures.

[0048] like Figure 4 As shown, the input standing wave of the low insertion loss digitally controlled attenuator circuit of the embodiment of the invention is similar to that of the traditional structure, and shows good matching characteristics within the working frequency band; Figure 5 As shown, the output standing wave of the low insertion loss digitally controlled attenuator circuit of the embodiment of the invention is similar to that of the traditional structure, and shows good matching characteristics within the working frequency band; Figure 6 As shown, the ground state insertion loss of the low insertion loss digitally controlled attenuator circuit of the embodiment of the present invention is nearly half of that of the traditional structure; Figure 7 As shown, the attenuation accuracy of the low insertion loss digitally controlled attenuator circuit in the embodiment of the present invention is closer to that of the traditional structure, and has a higher attenuation accuracy within the entire bandwidth; therefore, compared with the traditional structure, the biggest advantage of the low insertion loss digitally controlled attenuator in the embodiment of the present invention is that it effectively reduces the base state insertion loss, and can be used in the front end of the receiver for large dynamic amplitude regulation to greatly reduce the overall noise of the receiving channel.

Claims

1. A digitally controlled attenuator with low insertion loss, characterized in that: It includes a radio frequency input port, a radio frequency output port, a switch module and an attenuation module; The switch module comprises a first switch tube SW1, a second switch tube SW2, a third switch tube SW3, a fourth switch tube SW4, and a fifth switch tube SW5 which are sequentially connected in series, wherein the other end of the first switch tube SW1 is grounded, a first resistor R1 is connected in parallel to both ends of the first switch tube SW1, the other end of the fifth switch tube SW5 is grounded, and a second resistor R2 is connected in parallel to both ends of the fifth switch tube SW5; both ends of the third switch tube SW3 are connected to the RF input port and the RF output port; One end of the attenuation module is connected to the RF output port through the second switch tube SW2, and the other end thereof is connected to the RF input port through the fourth switch tube SW4; or the attenuation module is connected in parallel at both ends of the third switch tube SW3; or there are two attenuation modules, one of which is connected in series between the first switch tube SW1 and the second switch tube SW2, and the other is connected in series between the fourth switch tube SW4 and the fifth switch tube SW5.

2. The low insertion loss digitally controlled attenuator according to claim 1, characterized in that: When one end of the attenuation module is connected to the RF output port through the second switch tube SW2, and the other end thereof is connected to the RF input port through the fourth switch tube SW4, the attenuation module includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6; The third resistor R3 and the fourth resistor R4 are connected to each other through a microstrip line TL1, one end of the third resistor R3 is grounded via a fifth resistor R5, and the other end thereof is connected to the RF output port via a second switch tube SW2; one end of the fourth resistor R4 is grounded via a sixth resistor R6, and the other end thereof is connected to the RF input port via a fourth switch tube SW4.

3. The low insertion loss digitally controlled attenuator according to claim 2, characterized in that: Two ends of the fifth resistor R5 and two ends of the sixth resistor R6 are respectively connected in parallel to a phase compensation structure.

4. The low insertion loss digitally controlled attenuator according to claim 3, characterized in that: The phase compensation structure adopts capacitors or inductors.

5. The low insertion loss digitally controlled attenuator according to claim 2, characterized in that: The third resistor R3, the fourth resistor R4, the fifth resistor R5 and the sixth resistor R6 together form a Π-type attenuation network.

6. The low insertion loss digitally controlled attenuator according to claim 1, characterized in that: When the attenuation module is connected in parallel to both ends of the third switch tube SW3, the attenuation module includes a third resistor R3 and a fourth resistor R4 connected in series through a microstrip line TL1; The other end of the third resistor R3 is connected to the RF output port, and the other end of the fourth resistor R4 is connected to the RF input port.

7. The low insertion loss digitally controlled attenuator according to claim 1, characterized in that: When there are two attenuation modules, one of which is connected in series between the first switch tube SW1 and the second switch tube SW2, and the other is connected in series between the fourth switch tube SW4 and the fifth switch tube SW5, the attenuation module includes a third resistor R3 and a fourth resistor R4; One end of the third resistor R3 is connected to the first switch tube SW1, and the other end thereof is connected to the second switch tube SW2 and the first resistor R1 respectively; One end of the fourth resistor R4 is connected to the fourth switch tube SW4 and the second resistor R2 respectively, and the other end thereof is connected to the fifth switch tube SW5; The third resistor R3 and the fourth resistor R4 are connected via a microstrip line TL1.

8. The low insertion loss digitally controlled attenuator according to claim 1, characterized in that: The switch module as a whole constitutes a single-pole single-throw absorptive switch.

9. The low insertion loss digitally controlled attenuator according to claim 1, characterized in that: The third switch tube SW3 , the first switch tube SW1 , the fifth switch tube SW5 , the second switch tube SW2 , and the fourth switch tube SW4 are controlled by a pair of complementary TTL levels.

10. The low insertion loss digitally controlled attenuator according to any one of claims 1 to 9, characterized in that: The digital controlled attenuator is designed based on a gallium arsenide process, a CMOS process or a GeSi process.

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