Pi-type resistance attenuation network structure capable of adjusting attenuation

Abstract

The invention belongs to the technical field of radio frequency microwaves, and particularly provides a pi-type resistance attenuation network structure capable of adjusting attenuation, which is used for solving the problem that the attenuation amount of a traditional pi-type resistance attenuation network structure is not adjustable. On the basis of a traditional structure, a switch transistor Q2 is converted into an attenuation switch from a through switch, independent break-over voltage V3 and a bias resistor Rb4 are introduced into a base electrode of the switch transistor Q2, a new attenuation resistor R4 is introduced into a collector electrode of the switch transistor Q2, and through independent regulation and control of an attenuation circuit where the switch transistor Q2 is located, combined use of the attenuation resistor R4 and other attenuation resistors is achieved. The one-bit attenuation network has three attenuation states and straight-through states; in conclusion, attenuation adjustment of the one-bit pi-type resistance attenuation network can be realized, so that the attenuation bits are remarkably reduced in the design of the multi-bit numerical control step attenuator.

Description

Technical Field

[0001] The invention belongs to the field of radio frequency microwave technology, and specifically provides a π-type resistor attenuation network structure with adjustable attenuation, so as to realize adjustable attenuation of the attenuation network structure. Background Art

[0002] CNC step attenuators are used in many systems. By using the attenuator to attenuate the signal differently, the signal size can be changed. In the design of CNC step attenuators, commonly used structures include T-type resistor attenuation network and π-type resistor attenuation network. Taking a 5-bit attenuator as an example, the 5-bit attenuator has 5 attenuation networks, and the attenuation amounts are: 0.5dB, 1dB, 2dB, 4dB, and 8dB, thereby forming an attenuation amount that is any multiple of 0.5dB from 0 to 15.5dB. If an attenuation of 9.5dB is required, the 0.5dB, 1dB, and 8dB bits are turned on, and the remaining attenuation bits are turned off (in a straight-through state).

[0003] In the traditional CNC step attenuator, the π-type resistor attenuation network structure is as follows: Figure 1 As shown, the switching transistors Q1~Q4 and the base resistor R b1 ~R b3 , attenuation resistors R1~R3, V1 and V2 provide conduction voltage to the two pairs of switching transistors, Rfin is the RF signal input, and Rfout is the RF signal output; in the working process, when V1=0 and V2=1, the switching transistors Q3 and Q4 are turned on, and the switching transistors Q1 and Q2 are turned off, and the RF signal cannot pass through the switching transistors Q1 and Q2, and can only pass through the resistance attenuation network composed of resistors R1, R2, and R3, thereby attenuating the signal. This state is the attenuation state; conversely, when V1=1 and V2=0, the switching transistors Q1 and Q2 are turned on, and the switching transistors Q3 and Q4 are turned off. At this time, the switching transistors Q1 and Q2 provide a direct signal path, so that the RF signal does not pass through the π-type resistance attenuation network. This state is the direct-through state.

[0004] However, the above-mentioned π-type resistor attenuation network structure can only have one attenuation state. When the resistance values ​​are determined, the attenuation amount of the attenuation network is uniquely determined, that is, the attenuation amount is not adjustable, and a specific attenuation amount requires the use of different attenuation bits for combination; therefore, in the design of multi-bit CNC step attenuators, the more bits the larger the chip area. Summary of the invention

[0005] The purpose of the present invention is to provide a π-type resistor attenuation network structure with adjustable attenuation in order to solve the problem that the attenuation of a traditional π-type resistor attenuation network structure is not adjustable. On the basis of the traditional structure, the present invention introduces a voltage source, a bias resistor and an attenuation resistor, so that a one-bit attenuation network has four states, namely, three attenuation states and one pass-through state, thereby reducing the number of bits of the attenuation network of a multi-digital controlled step attenuator and reducing the chip layout area.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A π-type resistor attenuation network structure with adjustable attenuation includes: switching transistors Q1-Q4, base resistor R b1 ~R b4 , attenuation resistors R1 to R4; characterized in that:

[0008] The collector of the switching transistor Q1, the emitter of the switching transistor Q2, and the emitter of the switching transistor Q3 are all connected to the RF signal input terminal, the emitter of the switching transistor Q1, the collector of the switching transistor Q2, and the emitter of the switching transistor Q4 are all connected to the RF signal output terminal, the attenuation resistor R1 is connected between the RF signal input terminal and the RF signal output terminal, the attenuation resistor R2 is connected between the collector of the switching transistor Q3 and the signal ground, the attenuation resistor R3 is connected between the collector of the switching transistor Q4 and the signal ground, and the attenuation resistor R2 is connected between the collector of the switching transistor Q2 and the RF signal output terminal; the base of the switching transistor Q1 is connected through the base resistor R b1 Connect the conduction voltage V1, the base of the switching transistor Q2 is connected through the base resistor R b4 Connect the conduction voltage V3, the base of the switching transistor Q3 is connected through the base resistor R b2 Connect the conduction voltage V2, the base of the switching transistor Q4 is connected through the base resistor R b3 Connect the conduction voltage V2.

[0009] Furthermore, when V1=1, V2=0, and V3=0, the switch transistor Q1 is turned on, and the switch transistors Q2, Q3, and Q4 are turned off, and the π-type resistance attenuation network structure works in a through state.

[0010] Furthermore, when V1=0, V2=1, and V3=0, the switch transistors Q3 and Q4 are turned on, the switch transistors Q1 and Q2 are turned off, and the π-type resistance attenuation network structure works in the third attenuation state.

[0011] Furthermore, when V1=0, V2=1, and V3=1, the switch transistors Q2, Q3, and Q4 are turned on, the switch transistor Q1 is turned off, and the π-type resistance attenuation network structure operates in the second attenuation state.

[0012] Furthermore, when V1=1, V2=1, and V3=1, the switch transistors Q1, Q2, Q3, and Q4 are all turned on, and the π-type resistance attenuation network structure operates in the first attenuation state.

[0013] Based on the above technical solution, the beneficial effects of the present invention are:

[0014] The present invention provides a π-type resistor attenuation network structure with adjustable attenuation. Based on the traditional structure, the switch transistor Q2 is transformed from a through switch to an attenuation switch, and an independent on-voltage V3 and a bias resistor R are introduced into the base. b4 , a new attenuation resistor R4 is introduced into its collector, and the attenuation resistor R4 is used in combination with other attenuation resistors through independent regulation of the attenuation path where the switching transistor Q2 is located, so that a one-bit attenuation network has three attenuation states and a through state; in summary, the present invention can realize the attenuation adjustment of a one-bit π-type resistor attenuation network, thereby significantly reducing the number of attenuation bits in the design of a multi-digit CNC step attenuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of the traditional π-type resistance attenuation network structure.

[0016] Figure 2 It is a structural schematic diagram of the π-type resistance attenuation network structure with adjustable attenuation in the present invention.

[0017] Figure 3 This is a simulation result diagram of the through state (0dB) of the π-type resistor attenuation network structure with adjustable attenuation in the present invention.

[0018] Figure 4 This is a simulation result diagram of the first attenuation state (1 dB) of the π-type resistor attenuation network structure with adjustable attenuation in the present invention.

[0019] Figure 5 The simulation result diagram of the second attenuation state (2dB) of the π-type resistor attenuation network structure with adjustable attenuation in the present invention is shown in FIG.

[0020] Figure 6 The simulation result diagram of the third attenuation state (3dB) of the π-type resistor attenuation network structure with adjustable attenuation in the present invention is shown in FIG. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0022] This embodiment provides a π-type resistor attenuation network structure with adjustable attenuation, such as Figure 2 As shown, it includes: switching transistors Q1~Q4, base resistor R b1 ~Rb4 , attenuation resistors R1~R4, V1~V3 are on-state voltages, Rfin is the RF signal input, and Rfout is the RF signal output; wherein, the collector of the switching transistor Q1, the emitter of the switching transistor Q2, and the emitter of the switching transistor Q3 are all connected to the RF signal input terminal, the emitter of the switching transistor Q1, the collector of the switching transistor Q2, and the emitter of the switching transistor Q4 are all connected to the RF signal output terminal, the attenuation resistor R1 is connected between the RF signal input terminal and the RF signal output terminal, the attenuation resistor R2 is connected between the collector of the switching transistor Q3 and the signal ground, the attenuation resistor R3 is connected between the collector of the switching transistor Q4 and the signal ground, and the attenuation resistor R2 is connected between the collector of the switching transistor Q2 and the RF signal output terminal; the base of the switching transistor Q1 is connected through the base resistor R b1 Connect the conduction voltage V1, the base of the switching transistor Q2 is connected through the base resistor R b4 Connect the conduction voltage V3, the base of the switching transistor Q3 is connected through the base resistor R b2 Connect the conduction voltage V2, the base of the switching transistor Q4 is connected through the base resistor R b3 Connect the conduction voltage V2.

[0023] In terms of working principle:

[0024] When V1=1, V2=0, V3=0, the switch transistor Q1 is turned on, and the switch transistors Q2, Q3, and Q4 are turned off. The switch transistor Q1 provides a direct signal path, and the signal does not pass through the π-type resistor attenuation network. At this time, it is in a direct state and the signal is not attenuated (0dB);

[0025] When V1=0, V2=1, V3=0, the switch transistors Q3 and Q4 are turned on, and the switch transistors Q1 and Q2 are turned off. The signal cannot pass through the direct path where the switch transistor Q1 is located and the attenuation path where the switch transistor Q2 is located, and can only pass through the π-type resistance attenuation network composed of attenuation resistors R1, R2, and R3. At this time, it is the third attenuation state, and the signal is attenuated by 3dB.

[0026] When V1=0, V2=1, V3=1, the switch transistors Q2, Q3, and Q4 are turned on, and the switch transistor Q1 is turned off. The signal cannot pass through the direct path where the switch transistor Q1 is located, and the switch transistor Q2 is turned on, so that the attenuation resistor R4 is connected in parallel with R1 and then forms a new π-type resistance attenuation network with the attenuation resistors R2 and R3. Because the resistance of the attenuation resistor R4 after being connected in parallel with R1 is smaller than that of the attenuation resistor R1, the attenuation amount at this time will be smaller than that of the π-type resistance attenuation network directly formed by the attenuation resistors R1, R2, and R3. This is the second attenuation state, and the signal is attenuated by 2dB.

[0027] When V1=1, V2=1, V3=1, the switching transistors Q1, Q2, Q3, and Q4 are all turned on, and the switching transistor Q1 provides a direct signal path, so most of the signal passes through the direct path where the switching transistor Q1 is located, and a small part of the signal passes through the π-type resistance attenuation network composed of attenuation resistors R1, R2, R3, and R4, and the signal is slightly attenuated. This is the first attenuation state, and the signal is attenuated by 1dB;

[0028] It can be seen that the present invention can use a one-bit attenuation network to achieve a total of four states, including three attenuation states and one pass-through state. If a traditional π-type resistor attenuation network circuit requires a two-bit resistor attenuation network to achieve 1dB, 2dB, and 3dB attenuation, it can be seen that for the design of a digitally controlled step attenuator, the present invention can effectively reduce the number of attenuation bits.

[0029] Specifically, this embodiment is based on Huahong BSC180 process, and uses software Cadence to simulate the above-mentioned π-type resistor attenuation network structure, and obtains three attenuation states and one direct-through state. The simulation frequency range is set to 90-100GHz, and the frequency scanning step is set to 500MHz. Through simulation, the attenuation and direct-through loss of the circuit structure can be obtained. The direct-through loss represents the magnitude of the signal loss when the circuit is in the direct-through state. The attenuation is obtained by subtracting the direct-through loss from the loss when the circuit is in the attenuation state. During the simulation process, the voltages V1, V2, and V3 are respectively 0V or 1V according to the actual application needs. The resistance values ​​of all base bias resistors are 1KΩ, providing the transistor with a suitable base current and conduction voltage. The resistance value of the attenuation resistor R1 is 150Ω, the resistance values ​​of R2 and R3 are 8Ω, and the resistance value of R4 is 70Ω. The collector length of the switching transistor Q1 is 2um, the collector length of Q2 is 5um, and the collector lengths of Q3 and Q4 are 4um; when the attenuation network is in the direct-through state, the attenuation and direct-through loss are as follows: Figure 3 As shown, it can be seen that the attenuation network has a 1.1ndB attenuation, which is close to 0dB, and the direct loss of the attenuation network is 7.7dB; when the attenuation network is in the first attenuation state, the attenuation and direct loss are as follows Figure 4 As shown, it can be seen that the attenuation is 933mdB, close to 1dB; when the attenuation network is in the second attenuation state, the attenuation and direct loss are as follows Figure 5 As shown, it can be seen that the attenuation is 2dB; when the circuit is in the third attenuation state, the attenuation and direct loss are as follows Figure 3 As shown, it can be seen that the attenuation is 3 dB; thus, the present invention provides a π-type resistor attenuation network structure with adjustable attenuation, which can achieve adjustable attenuation, thereby reducing the number of bits in the design of a multi-digital controlled step attenuator.

[0030] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A π-type resistor attenuation network structure with adjustable attenuation, include: Switching transistor Q 1 ~Q 4 , base resistance R b1 ~R b4 , attenuation resistance R 1 ~R 4 ; It is characterized in that, Switching transistor Q 1 The collector of the switching transistor Q 2 The emitter of the switching transistor Q 3 The emitters of the switch transistors Q 1 The emitter of the switching transistor Q 2 The collector of the switching transistor Q 4 The emitters are connected to the RF signal output terminal, and the attenuation resistor R 1 Connected between the RF signal input terminal and the RF signal output terminal, the attenuation resistor R 2 Connected to the switching transistor Q 3 Between the collector and the signal ground, the attenuation resistor R 3 Connected to the switching transistor Q 4 Between the collector and the signal ground, the attenuation resistor R 2 Connected to the switching transistor Q 2 Between the collector and the RF signal output terminal; the switching transistor Q 1 The base of the b1 Connect the conduction voltage V 1 , the switching transistor Q 2 The base of the b4 Connect the conduction voltage V 3 , the switching transistor Q 3 The base of the b2 Connect the conduction voltage V 2 , the switching transistor Q 4 The base of the b3 Connect the conduction voltage V 2 .

2. According to the π-type resistor attenuation network structure with adjustable attenuation according to claim 1, It is characterized in that When V 1 =1, V 2 =0, V 3 = 0, the switching transistor Q 1 Turn on, the switching transistor Q 2 , Q 3 , Q 4 When the resistor is closed, the π-type resistor attenuation network structure works in the through state.

3. According to the π-type resistor attenuation network structure with adjustable attenuation as claimed in claim 1, It is characterized in that When V 1 =0, V 2 =1, V 3 =0, the switch transistors Q3 and Q4 are turned on, the switch transistors Q1 and Q2 are turned off, and the π-type resistance attenuation network structure works in the third attenuation state.

4. According to the π-type resistor attenuation network structure with adjustable attenuation as claimed in claim 1, It is characterized in that When V 1 =0, V 2 =1, V 3 =1, the switching transistor Q 2 , Q 3 , Q 4 Turn on, the switching transistor Q 1 When the resistor is turned off, the π-type resistance attenuation network structure works in the second attenuation state.

5. According to the π-type resistor attenuation network structure with adjustable attenuation as claimed in claim 1, It is characterized in that When V 1 =1, V 2 =1, V 3 =1, the switching transistor Q 1 , Q 2 , Q 3 , Q 4 All are turned on, and the π-type resistance attenuation network structure works in the first attenuation state.

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