阅读说明：本技术 高精度低插损超宽带数字衰减器及其补偿方法 (High-precision low-insertion-loss ultra-wideband digital attenuator and compensation method thereof ) 是由 翟英慧 万晶 梁晓新 于 2021-07-07 设计创作，主要内容包括：本发明具体涉及一种高精度低插损超宽带数字衰减器及其补偿方法,属于微波单片机芯片中的衰减器技术领域。包括一个由T型数字衰减器组成的输入单元、一个由简化T型数字衰减器组成的小位补偿电路以及一个由Pi型数字衰减器组成的幅度补偿电路组成的输出单元依次连接构成,所述的输入单元的输出端与Pi型数字衰减器组成的幅度补偿电路的输入端相连,连接处接入一个由简化T型数字衰减器组成的小位补偿电路,所述的幅度补偿电路的衰减电路中接入补偿电容。满足了匹配要求又可以实现16dB衰减位较好的衰减性能,而且简化T型衰减结构可以减小芯片尺寸。对实现更大衰减量的设计提供了更好的思路,可以极大程度提高较大衰减量的衰减位插入损耗、衰减精度等性能。(The invention particularly relates to a high-precision low-insertion-loss ultra-wideband digital attenuator and a compensation method thereof, belonging to the technical field of attenuators in microwave single-chip microcomputer chips. The amplitude compensation circuit comprises an input unit consisting of T-type digital attenuators, a small-bit compensation circuit consisting of simplified T-type digital attenuators and an output unit consisting of an amplitude compensation circuit consisting of Pi-type digital attenuators, which are sequentially connected, wherein the output end of the input unit is connected with the input end of the amplitude compensation circuit consisting of the Pi-type digital attenuators, the connection part is connected with the small-bit compensation circuit consisting of the simplified T-type digital attenuators, and compensation capacitors are connected into the attenuation circuits of the amplitude compensation circuit. The matching requirement is met, the better attenuation performance of 16dB attenuation position can be realized, and the chip size can be reduced by simplifying the T-shaped attenuation structure. The design of realizing larger attenuation amount provides a better idea, and the performances of attenuation bit insertion loss, attenuation precision and the like of larger attenuation amount can be greatly improved.)

1. A compensation method of a high-precision low-insertion-loss ultra-wideband digital attenuator is characterized in that a Pi-type attenuation structure is adopted to realize a large attenuation part in 16dB attenuation, the flatness in a band and the additional phase shift performance are guaranteed, a compensation capacitor is connected into a circuit of the Pi-type attenuation structure, the attenuation performance of different frequency points is compensated by using the amplitude-frequency characteristic of the capacitor, the capacitor parameters are changed according to different attenuation requirements of different frequency bands, a T-type attenuator is adopted to realize small attenuation for compensation, a small-order compensation circuit is added, namely, the simplified design of the T-type attenuation structure is placed in the Pi-type attenuation structure and the T-type attenuation structure to play the functions of a matching circuit and a compensation circuit, the attenuation can be compensated, and meanwhile, good port matching performance is realized.

2. The utility model provides a high accuracy low insertion loss ultra wide band digital attenuator, characterized by includes that an input unit, a little bit compensation circuit and an output unit that the range compensating circuit that constitutes by Pi type digital attenuator of constituteing that constitute by T type digital attenuator constitute by the input unit of T type digital attenuator group one-tenth of simplifying, the output of input unit link to each other with the input of the range compensating circuit that Pi type digital attenuator is constituteed, the junction inserts a little bit compensation circuit that constitutes by simplifying T type digital attenuator, the attenuation circuit of range compensating circuit in insert the compensation electric capacity, utilize the amplitude-frequency characteristic of electric capacity to realize compensating to the attenuation performance of different frequency points, change the electric capacity parameter according to different attenuation requirements of different frequency channels.

3. The digital attenuator of claim 2, wherein the small-order compensation circuit is a controllable switch circuit formed by MOS transistors.

4. A high accuracy low insertion loss ultra-wideband digital attenuator as claimed in claim 2, wherein said compensating capacitor is connected across the input and output of the amplitude compensation circuit comprising said Pi-type digital attenuator.

Technical Field

The invention particularly relates to a high-precision low-insertion-loss ultra-wideband digital attenuator and a compensation method thereof, belonging to the technical field of attenuators in microwave single-chip microcomputer chips.

Background

The digital attenuator is used as an important ring in a phased array radar system, the attenuation capable of improving the gain range is required to be provided for the whole system, meanwhile, the precision of the attenuation is required to be higher, and in addition, when the digital attenuator realizes the function of changing the gain of the system, the introduced additional phase is kept unchanged as much as possible, so that the situation of positioning error is avoided, and a phase calibration module is not required to be added; meanwhile, the smaller insertion loss avoids the deterioration of the gain performance of the system module caused by the attenuator module; in addition, the linearity of the attenuator is also an important index for judging the performance of the attenuator. The digital attenuator has the advantages of relatively simple control mode, obvious advantages, low relative phase shift amount and good linearity, and is widely applied to the phased array radar.

At present, the high-precision low-insertion-loss ultra-wideband digital attenuator cannot improve the attenuation performance of the numerical control attenuator under different frequencies, has small influence on the performance of the attenuator such as additional phase shift amount, input/output return loss, linearity and the like, and can reduce the area of a chip.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the high-precision low-insertion-loss ultra-wideband digital attenuator and the compensation method thereof, which can compensate the attenuation performance of the digital controlled attenuator under different frequencies, have small influence on the performance of the attenuator such as additional phase shift amount, input/output return loss, linearity and the like, and reduce the chip area.

The digital attenuator mainly has three structural topologies: and selecting proper attenuation topological structures according to the index requirements of different attenuators to realize the design index.

Parasitic parameters of a system in a high-frequency circuit are obviously reflected in circuit performance, in a digital attenuator, both parasitic between capacitance resistors and parasitic capacitance resistors of an MOS tube have influence on attenuation, in an ultra-wideband digital attenuator, the influence at different frequencies is different, so that the high-frequency characteristic and the low-frequency characteristic of the attenuator in a working frequency band have large fluctuation, the flatness in the band is poor, and the influence is more obviously reflected in an attenuation position with larger attenuation, so that in a Pi-type attenuation structure, an amplitude compensation circuit is provided, namely, compensation is performed in an attenuation network by adopting a parallel capacitance mode, and the attenuation precision change caused by the frequency change further realizes better flatness in the attenuation precision band in the working frequency band.

In the Pi-type attenuation structure, a large loss is introduced by the parasitic capacitance and the parasitic resistance of the MOS transistor at high frequency, resulting in a large attenuation of the attenuator at high frequency. Therefore, the compensation circuit adopts a mode of parallel capacitance to reduce the relative influence of a high-frequency part and improve the flatness in a band.

An equivalent circuit of a Pi-type attenuation structure. The Z matrix is known from the equivalent circuit as follows:

（4.1）

the relational expression of the S parameter and the Z matrix can be obtained according to the definitions of the Z matrix and the scattering parameter S parameter as follows:

（3.16）

（3.17）

（3.18）

（3.19）

if the attenuation of the attenuator is X, we can obtain the attenuation according to the relation between the Z matrix and the S parameter to satisfy the attenuationThe expression of (a) is as follows:

（4.2）

byAs can be seen from the expression, whenParallel capacitorThen, according to the capacitive reactance expression of the capacitorThen, thenTotal resistance value ofThus attenuating the network as the frequency f increasesThe total resistance of the branch is reduced, the attenuation of the attenuator is increased, and the in-band flatness of the attenuator is further improved. In terms of capacitance value, the influence of the parallel capacitance on the whole attenuation amount and the introduced additional phase shift need to be considered, so that the additional phase shift needs to be introduced into the attenuation networkThe value of (A) is reasonably selected, and the capacitance reactance value of a common capacitor isThe resistance value is 8-10 times.

Taking a 4dB attenuation bit as an example, in an in-band flatness comparison graph of 4dB attenuation bit attenuation precision of a traditional Pi-type attenuator and a Pi-type attenuator with an amplitude compensation circuit, it can be obviously seen that the absolute attenuation of the 4dB attenuator designed by a Pi-type attenuation structure with the amplitude compensation circuit is larger at high frequency, so that the fluctuation of the relative attenuation in an operating frequency band of 8-12 GHz is smaller, the in-band flatness of the attenuator can be obviously improved by the compensation circuit, and the attenuation precision change in the whole operating frequency band is smaller.

In the design process of 8dB and 16dB attenuation bits, because the Pi type attenuation structure has more parasitic parameters, the insertion loss and the additional phase shift performance of the Pi type attenuation structure have larger influence in the design of the attenuation bits with larger attenuation amount, and the effect is not obvious after the amplitude compensation and phase compensation circuit is adopted, the 8dB attenuation bits in the digital attenuator are realized by adopting a structure of cascading two 4dB Pi type attenuation structures, but if the 16dB attenuation amount is realized by adopting the cascading mode of 4 Pi type attenuation structures, the chip area is overlarge. Therefore, a small bit compensation circuit design is proposed to design 16dB attenuation bits.

A compensation method of a high-precision low-insertion-loss ultra-wideband digital attenuator is characterized in that a Pi-type attenuation structure is adopted to realize a large attenuation part in 16dB attenuation, the flatness in a band and the additional phase shift performance are guaranteed, a compensation capacitor is connected into a circuit of the Pi-type attenuation structure, the attenuation performance of different frequency points is compensated by using the amplitude-frequency characteristic of the capacitor, the capacitor parameters are changed according to different attenuation requirements of different frequency bands, a T-type attenuator is adopted to realize small attenuation for compensation, a small-order compensation circuit is added, namely, the simplified design of the T-type attenuation structure is placed in the Pi-type attenuation structure and the T-type attenuation structure to play the functions of a matching circuit and a compensation circuit, the attenuation can be compensated, and meanwhile, good port matching performance is realized.

Because the area of the attenuator chip is overlarge due to the continuous cascade connection of the T-shaped attenuation structures, the simplified T-shaped attenuation structure is proposed, namely the simplified design of the T-shaped attenuation structure is put into the Pi-shaped attenuation structure and the T-shaped attenuation structure to play the functions of a matching circuit and a compensating circuit.

The utility model provides a high accuracy low insertion loss ultra wide band digital attenuator, characterized by includes that an input unit, a little bit compensation circuit and an output unit that the range compensating circuit that constitutes by Pi type digital attenuator of constituteing that constitute by T type digital attenuator constitute by the input unit of T type digital attenuator group one-tenth of simplifying, the output of input unit link to each other with the input of the range compensating circuit that Pi type digital attenuator is constituteed, the junction inserts a little bit compensation circuit that constitutes by simplifying T type digital attenuator, the attenuation circuit of range compensating circuit in insert the compensation electric capacity, utilize the amplitude-frequency characteristic of electric capacity to realize compensating to the attenuation performance of different frequency points, change the electric capacity parameter according to different attenuation requirements of different frequency channels.

The small position compensation circuit is composed of a controllable switch circuit composed of MOS tubes.

The compensation capacitor is bridged between the input end and the output end of the amplitude compensation circuit consisting of the Pi type digital attenuator.

The invention not only meets the matching requirement, but also can realize the better attenuation performance of 16dB attenuation position, and simplifies the T-shaped attenuation structure and can reduce the chip size. The compensation circuit provides a better idea for realizing the design of larger attenuation amount, and can greatly improve the performances of insertion loss, attenuation precision and the like of attenuation bits with larger attenuation amount.

Drawings

FIG. 1 is a structural topology of the digital attenuator of the present invention.

FIG. 2 is a structural topology diagram of a T-shaped digital attenuator.

FIG. 3 is a topological diagram of the structure of the bridge-T type digital attenuator.

FIG. 4 is a topological diagram of the structure of a Pi-type digital attenuator.

FIG. 5 is an equivalent circuit of the attenuation structure of the Pi type digital attenuator.

FIG. 6 is a graph of absolute attenuation versus 4dB attenuation bit.

FIG. 7 is a graph of 4dB attenuation bit versus attenuation.

Detailed Description

Example one

The invention is further disclosed below with the aid of fig. 1.

A compensation method of a high-precision low-insertion-loss ultra-wideband digital attenuator is characterized in that a Pi-type attenuation structure is adopted to realize a large attenuation part in 16dB attenuation, the flatness in a band and the performance of additional phase shift are guaranteed, a compensation capacitor C2 is connected into a circuit of the Pi-type attenuation structure, the attenuation performance of different frequency points is compensated by using the amplitude-frequency characteristic of a capacitor C2, the capacitance parameters are changed according to different attenuation requirements of different frequency bands, a T-type attenuator is adopted to realize small attenuation for compensation, a small-order compensation circuit is added, namely, the simplified design of the T-type attenuation structure is placed in the Pi-type attenuation structure and the T-type attenuation structure to play the functions of a matching circuit and a compensation circuit, the attenuation can be compensated, and meanwhile, good port matching performance is realized.

A high-precision low-insertion-loss ultra-wideband digital attenuator is characterized by comprising an input unit consisting of T-type digital attenuators, a small-bit compensation circuit consisting of simplified T-type digital attenuators and an output unit consisting of an amplitude compensation circuit consisting of a Pi-type digital attenuator, wherein the output end of the input unit is connected with the input end of the amplitude compensation circuit consisting of the Pi-type digital attenuators, the small-bit compensation circuit consisting of the simplified T-type digital attenuators is connected to the joint, a compensation capacitor C2 is connected into the attenuation circuit of the amplitude compensation circuit, the attenuation performance of different frequency points is compensated by using the amplitude-frequency characteristic of a capacitor C2, and the capacitance parameters are changed according to different attenuation requirements of different frequency bands.

The small position compensation circuit is composed of a controllable switch circuit composed of a MOS transistor M2, the drain electrode of the small position compensation circuit is connected with the output end of the input unit, the source electrode of the small position compensation circuit is connected with a resistor R3 in series and is connected with the ground, and the grid electrode of the small position compensation circuit is a control electrode.

The compensation capacitor C2 is connected across the input end and the output end of the amplitude compensation circuit composed of the Pi type digital attenuator.

The large attenuation part in 16dB attenuation is realized by adopting a Pi type attenuation structure, so that the in-band flatness and the additional phase shift performance are better ensured, and then the small attenuation is compensated by adopting a T type attenuator, but the port matching performance of the T type attenuation structure is deteriorated along with the increase of the attenuation, and the deterioration of the attenuation performance is easily caused in the cascade process, so that the attenuation can be compensated and the good port matching performance can be realized by considering the increase of a small-position compensation circuit. Because the area of an attenuator chip is overlarge due to the continuous cascade connection of the T-shaped attenuation structures, the simplified T-shaped attenuation structure is provided, namely the simplified design of the T-shaped attenuation structure is placed in the Pi-shaped attenuation structure and the T-shaped attenuation structure to play the functions of a matching circuit and a compensating circuit, the design not only meets the matching requirement, but also can realize the better attenuation performance of 16dB attenuation bits, and the chip size can be reduced due to the simplified T-shaped attenuation structure. The compensation circuit provides a better idea for realizing the design of larger attenuation amount, and can greatly improve the performances of insertion loss, attenuation precision and the like of attenuation bits with larger attenuation amount.