High-precision gain control circuit

Abstract

The invention belongs to the technical field of integrated circuit design, and provides a high-precision gain control circuit which comprises an adjustable attenuation network and two variable gain amplifiers which are arranged at the input end and the output end of the adjustable attenuation network respectively and are of the same structure. The variable gain amplifier comprises a first adjustable coupling attenuation matching network, a variable gain transistor network and a second adjustable coupling attenuation matching network which are cascaded in sequence; the adjustable attenuation network is used for reducing a parasitic phase generated in a gain control process; m thin metal coupling attenuation coils and N thin metal coupling attenuation coils are respectively arranged in the first adjustable coupling attenuation matching network and the second adjustable coupling attenuation matching network; the two ends of each coupling attenuation coil are grounded, on-off of each coupling attenuation coil is controlled by a transistor, adjustment of different gain gears is achieved by controlling the conduction positions and the conduction number of the coupling attenuation coils, and the gain control precision is further improved.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit design technology, and more specifically to a high-precision gain control circuit. Background Technology

[0002] Gain control circuits are primarily used in phased array systems to achieve amplitude modulation of circuit signals and are a crucial component of microwave and millimeter-wave phased array circuits. Gain control circuits are widely used in various phased array radars, wireless communication systems, and other circuit systems, and their performance significantly impacts the core system indicators. In traditional active gain control circuits, gain control is achieved by active amplifying transistors. A wide range of gain control can be achieved by cascading two active stages, as illustrated in Chinese invention patent CN114024511A, "A Digitally Controlled Wideband High Linearity Variable Gain Amplifier." This amplifier includes two branches: a high-gain, high-linearity mode and a low-gain, high-linearity mode. Switching between these branches is achieved using a switch, resulting in a wideband variable gain amplifier with relatively consistent linearity and noise figure across both high and low gain modes, providing a wider dynamic range and good signal-to-noise ratio at different gains. However, this method suffers from insufficient gain control precision, poor linearity of the active amplifying transistors, and unresolved parasitic phase issues, failing to meet the high precision and high linearity requirements across a wide gain control range. Summary of the Invention

[0003] The technical problem to be solved by this invention is how to further improve the gain control accuracy under wide-range gain control, while reducing parasitic phase.

[0004] The present invention solves the above-mentioned technical problems through the following technical means: This invention provides a high-precision gain control circuit, characterized in that it includes an adjustable attenuation network and two variable gain amplifiers with identical structures respectively disposed at its input and output terminals; the variable gain amplifier includes a first adjustable coupling attenuation matching network, a variable gain transistor network and a second adjustable coupling attenuation matching network cascaded in sequence. The adjustable attenuation network is used to reduce the parasitic phase generated during gain control; The first and second adjustable coupling attenuation matching networks are respectively provided with M and N thin metal coupling attenuation coils; the two ends of each coupling attenuation coil are connected to ground by a transistor, and its on / off state is controlled; by controlling the position and number of coupling attenuation coils that are turned on, different gain levels can be adjusted.

[0005] Preferably, the variable gain transistor network is numerically controlled, comprising a core module of six parallel-connected binary-weighted Gilbert units for differential gain control, with each module corresponding to a control bit VC.i i=0,1,2,3,4,5; through the combination of 6 control bits, the gain state that meets the gain step is selected from 64 valid states; and through the cascading of two stages of variable gain amplifiers, a wide range of gain control is achieved; Preferably, the single-bit structure of the Gilbert unit includes six transistors, M1 to M6; wherein M1 and M4 are polarity commutation transistors, and M2, M3, M5 and M6 are common-source amplifier transistors. VC1 To M VC4 It is a digital control transistor used to switch signal paths; all transistors in the same bit Gilbert unit are the same size, and the sizes of different bit units are allocated according to binary weights.

[0006] Furthermore, the operating principle of the Gilbert unit is as follows: When the CNC signal is 0, M VC2 and M VC3 On, M VC1 and M VC4 When disconnected, the gate of M4 is connected to the bias signal VB0 of the polarity selection transistor, while the gate of M1 is pulled down to ground; the RF signal is amplified through M5 and M6, and the output signal is positively amplified. When the numerical control signal is 1, M VC1 and M VC4 On, M VC2 and M VC3 When disconnected, the gate of M1 is connected to the bias signal VB0 of the polarity selection transistor, while the gate of M4 is pulled down to ground; the RF signal is amplified through M2 and M3, and the output signal is inverted amplified.

[0007] Preferably, the coupling attenuation coil is located below the transformer coil and does not occupy additional area.

[0008] Furthermore, the operating principle of the coupling attenuation coil is as follows: When all switches are open, the coupling attenuation coil based on the low-layer thin metal operates in a redundant metal state, the coupling coefficient of the transformer remains unchanged, and the signal is transmitted through the normal path of the transformer without being affected by additional attenuation or phase changes. When several switches are closed, the coupling attenuation coil based on the low-layer thin metal forms an inductor to ground, coupling some energy to ground. This reduces the signal energy coupled to the next stage input through the transformer secondary coil, thereby further improving the accuracy of signal gain control.

[0009] Preferably, the adjustable attenuation network includes transistor M. S1 transistor M S1 The control signal is V c By controlling transistor MS1 The switching on and off of the network puts the adjustable attenuation network into the amplitude reference state and the amplitude attenuation state, respectively.

[0010] Preferably, the adjustable attenuation network is based on a π-type attenuation network, and a compensation circuit consisting of a compensation capacitor C0 and a switching transistor M0 connected in series is connected between the series resistors, and the control signal of the transistor M0 is V1.

[0011] Preferably, the adjustable attenuation network is based on a π-type attenuation network, with a parallel compensation capacitor C connected to the branch resistance attenuating to ground. c .

[0012] Furthermore, the operating principle of the adjustable attenuation network is as follows: When the adjustable attenuation network is in the amplitude reference state, the phase control is implemented as follows: when V1=0, the equivalent capacitance C0 is equal to that of transistor M0 in the off state. M0 If they are connected in series, then their series equivalent capacitance is... When V1=1, it is equivalent to the equivalent resistance R of C0 and transistor M0 in the on state. M0 In series, where R M0 If the value is approximately 0, then its equivalent capacitance C 02 It is equal to C0; therefore, it can be seen that the phase compensation capacitor is different in these two states, thus changing the transmission phase value of the amplitude reference state.

[0013] The advantages of this invention are: (1) The high-precision gain control circuit proposed in this invention consists of two stages of active variable gain amplifier and adjustable attenuation network. The variable gain amplifier adopts an active amplification structure based on Gilbert unit. The two stages of active variable gain amplifier can realize a wide range of gain control. On this basis, the matching structure of the variable gain amplifier adopts a differential transformer structure with adjustable coupling attenuation to realize further refined control of the gain.

[0014] (2) Since direct cascading of two variable gain amplifiers will degrade the linearity of the circuit, this invention adds an adjustable attenuation network between the two variable gain amplifiers. By adjusting the attenuation state, the linearity of the circuit can be improved. The proposed adjustable attenuation network is based on a phase-compensated resistor attenuation network, which further reduces parasitic phase. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a high-precision gain control circuit structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the variable gain amplifier circuit structure according to an embodiment of the present invention; Figure 3This is a schematic diagram of the variable gain transistor and single-bit Gilbert cell circuit structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the principle of turning off all coupling attenuation coils in the adjustable coupling attenuation matching network according to an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the principle of partially turning off the coupling attenuation coil in the adjustable coupling attenuation matching network according to an embodiment of the present invention. Figure 6 This is a top view of the adjustable coupling attenuation matching network according to an embodiment of the present invention; Figure 7 This is a hierarchical view of the adjustable coupling attenuation matching network according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the adjustable attenuation network circuit structure according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the phase-shifting reference state of the adjustable attenuation network in the attenuation reference state according to an embodiment of the present invention; Figure 10 This is a schematic diagram of the phase-shift compensation state of the adjustable attenuation network in the attenuation reference state according to an embodiment of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1 This embodiment provides a high-precision gain control circuit. Its basic principle is to integrate active and passive gain control. Active gain control achieves a wide range of gain control, while passive gain control achieves high precision and high linearity. Compared to traditional gain control circuit structures, the gain control circuit proposed in this embodiment has the advantages of a large gain control range, high precision, and high linearity. Specifically, the basic circuit structure is as follows: Figure 1 As shown, it includes an adjustable attenuation network and two variable gain amplifiers with identical structures, respectively located at its input and output terminals; the variable gain amplifier includes a first adjustable coupling attenuation matching network, a variable gain transistor network and a second adjustable coupling attenuation matching network cascaded in sequence. The adjustable attenuation network is used to reduce the parasitic phase generated during gain control; like Figure 2As shown, the first and second adjustable coupling attenuation matching networks are respectively equipped with M and N thin metal coupling attenuation coils; the two ends of each coupling attenuation coil are connected to ground by a transistor, and its on / off state is controlled; by controlling the position and number of coupling attenuation coils that are on, different gain levels can be adjusted. Figure 6 , Figure 7 As shown, the coupling attenuation coil is located below the transformer coil, does not occupy additional area, and can simultaneously achieve impedance matching and attenuation control functions.

[0018] like Figure 3 As shown, the variable gain transistor network is numerically controlled and includes a core module of differential gain control with six parallel binary-weighted Gilbert units. Each module corresponds to a control bit VC. i i=0,1,2,3,4,5; through the combination of 6 control bits, the gain state that meets the gain step is selected from 64 valid states; and through the cascading of two stages of variable gain amplifiers, a wide range of gain control is achieved; in actual design, the variable gain transistor network unit can be set to an integer number of groups as needed, which can be more or less than 6 groups, and the corresponding control bits can also be set adaptively.

[0019] like Figure 3 As shown, the single-bit structure of the Gilbert unit includes six transistors, M1 to M6; where M1 and M4 are polarity commutation transistors, and M2, M3, M5, and M6 are common-source amplifier transistors. VC1 To M VC4 It is a digital control transistor used to switch signal paths; all transistors in the same bit Gilbert unit are the same size, and the sizes of different bit units are allocated according to binary weights.

[0020] The operating principle of the Gilbert unit is as follows: like Figure 3 As shown, when the CNC signal VC0 is 0 (low level), M VC2 and M VC3 On, M VC1 and M VC4 When disconnected, the gate of M4 is connected to the bias signal VB0 of the polarity selection transistor, while the gate of M1 is pulled down to ground; the RF signal is amplified through M5 and M6, and the output signal is positively amplified. When the numerical control signal VC0 is 1, M VC1 and M VC4 On, M VC2 and M VC3When disconnected, the gate of M1 is connected to the bias signal VB0 of the polarity selection transistor, while the gate of M4 is pulled down to ground. The RF signal is amplified through M2 and M3, and the output signal is inverted. Therefore, when the digital control signal switches between "0" and "1", the on and off states of the transistors reverse, and the phase of the output current flips by 180°. This combination of polarity selection and amplification functions allows the Gilbert unit to achieve gain adjustment while maintaining constant input and output impedance, thereby reducing phase fluctuations. In addition, when the digital control signal is "0" and "1", the on and off transistors are symmetrical and identical in size, further ensuring the constant impedance and linearity of gain adjustment. Therefore, the variable gain amplifier in the design achieves gain adjustment through digital gain control combined with the polarity selection and amplification functions of the Gilbert unit.

[0021] While the variable gain transistor network achieves basic gain adjustment, this embodiment further employs a first adjustable coupling attenuation matching network and a second adjustable coupling attenuation matching network connected to the input and output terminals of the variable gain transistor network to achieve more refined control of the signal gain; the core principle lies in the conduction position and number of coupling attenuation coils.

[0022] like Figure 4 , Figure 5 As shown, the operating principle of the coupling attenuation coil is as follows: When all switches are open, the operating state of the coupling attenuation coil based on the low-layer thin metal is redundant metal, which has very little impact on the performance of the transformer itself. The coupling coefficient of the transformer remains unchanged, and the signal is transmitted through the normal path of the transformer without being affected by additional attenuation or phase change. When several switches are closed, the coupling attenuation coil based on the low-layer thin metal forms an inductor to ground. This structure acts like a current discharge path, coupling some energy to ground, which reduces the signal energy coupled to the next stage input through the transformer secondary coil, thereby further improving the accuracy of signal gain control.

[0023] Therefore, under different combinations of switching conditions (different positions of the conducting coupling attenuation coils from the primary side of the transformer and different numbers of conducting coupling attenuation coils), different degrees of energy reduction can be achieved, which ultimately further fine-tunes the output of the variable gain amplifier and realizes the adjustment of different gain levels.

[0024] like Figure 8 As shown, the adjustable attenuation network includes transistor M. S1 transistor M S1 The control signal is V c By controlling transistor M S1The switching on and off of the network puts the adjustable attenuation network into the amplitude reference state and the amplitude attenuation state, respectively.

[0025] like Figure 8 As shown, the adjustable attenuation network is based on a π-type attenuation network. The resistor connection method of the π-type attenuation network is existing technology and will not be described further in this embodiment. In this embodiment, it is improved by connecting a compensation circuit consisting of a compensation capacitor C0 and a switching transistor M0 connected in series between the series resistors. The control signal for transistor M0 is V. 1。 A parallel compensation capacitor C is connected across the branch resistance that attenuates to ground. c The attenuation function in the adjustable attenuation network is controlled by bit V. c The phase compensation function is implemented through control bit V1. The adjustable attenuation network amplitude control function can further expand the gain control range and improve linearity. The phase compensation function can reduce phase changes during the adjustable attenuation network amplitude control process, thus reducing parasitic phase.

[0026] like Figure 9 , Figure 10 As shown, the operating principle takes the amplitude reference state as an example, that is, when V C When =1: When the adjustable attenuation network is in the amplitude reference state, the phase control is implemented as follows: when V1=0, the equivalent capacitance C0 is equal to that of transistor M0 in the off state. M0 If they are connected in series, then their series equivalent capacitance is... When V1=1, it is equivalent to the equivalent resistance R of C0 and transistor M0 in the on state. M0 In series, where R M0 If the value is approximately 0, then its equivalent capacitance C 02 It equals C0; thus, it can be seen that the phase compensation capacitor is different in these two states, thereby compensating for the phase change in the entire link gain control process.

[0027] Additionally, in the amplitude decay state, i.e. when V C When =0, the phase compensation process is the same as described above.

[0028] In the adjustable attenuation network circuit structure, the parasitic capacitance of the switching MOS leads to an increase in additional phase shift. Therefore, a compensation capacitor C is introduced in parallel to compensate for this. c This method reduces the additional phase shift and also introduces zeros to extend the bandwidth. Compensation capacitor C c The size is mainly determined by the attenuation and the attenuation structure of the parallel transistor M. S2 With M S3 The size of the capacitor determines the appropriate compensation capacitor, which is selected through simulation optimization with different values.

[0029] Therefore, by using a gain phase compensation capacitor and a compensation control switch, phase compensation during the attenuation process can be achieved, further reducing the parasitic phase in the overall circuit amplitude control process.

[0030] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-precision gain control circuit, characterized in that, It includes an adjustable attenuation network and two variable gain amplifiers with identical structures, respectively located at its input and output terminals; the variable gain amplifier includes a first adjustable coupling attenuation matching network, a variable gain transistor network and a second adjustable coupling attenuation matching network cascaded in sequence. The adjustable attenuation network is used to reduce the parasitic phase generated during gain control; The first adjustable coupling attenuation matching network and the second adjustable coupling attenuation matching network are respectively provided with M and N thin metal coupling attenuation coils; the two ends of each coupling attenuation coil are connected to ground by a transistor, and its on and off are controlled. Different gain levels can be adjusted by controlling the position and number of coupling attenuation coils that are turned on.

2. The high-precision gain control circuit according to claim 1, characterized in that, The variable gain transistor network is numerically controlled and includes a core module of differential gain control with six parallel binary-weighted Gilbert units, each module corresponding to a control bit VC. i i=0,1,2,3,4,5; through the combination of 6 control bits, the gain state that meets the gain step is selected from 64 valid states; and through the cascading of two stages of variable gain amplifiers, a wide range of gain control is achieved.

3. The high-precision gain control circuit according to claim 2, characterized in that, The single-bit structure of the Gilbert unit includes six transistors, M1 to M6; where M1 and M4 are polarity commutation transistors, and M2, M3, M5, and M6 are common-source amplifier transistors. VC1 To M VC4 It is a digital control transistor used to switch signal paths; all transistors in the same bit Gilbert unit are the same size, and the size of different bit units is allocated according to binary weights.

4. The high-precision gain control circuit according to claim 3, characterized in that, The operating principle of the Gilbert unit is as follows: When the CNC signal is 0, M VC2 and M VC3 On, M VC1 and M VC4 When disconnected, the gate of M4 is connected to the bias signal VB0 of the polarity selection transistor, while the gate of M1 is pulled down to ground; the RF signal is amplified through M5 and M6, and the output signal is positively amplified. When the numerical control signal is 1, M VC1 and M VC4 On, M VC2 and M VC3 When disconnected, the gate of M1 is connected to the bias signal VB0 of the polarity selection transistor, while the gate of M4 is pulled down to ground; the RF signal is amplified through M2 and M3, and the output signal is inverted amplified.

5. The high-precision gain control circuit according to claim 1, characterized in that, The coupling attenuation coil is located below the transformer coil and does not occupy additional area.

6. The high-precision gain control circuit according to claim 1, characterized in that, The operating principle of the coupling attenuation coil is as follows: When all switches are open, the coupling attenuation coil based on the low-layer thin metal operates in a redundant metal state, the coupling coefficient of the transformer remains unchanged, and the signal is transmitted through the normal path of the transformer without being affected by additional attenuation or phase changes. When several switches are closed, the coupling attenuation coil based on the low-layer thin metal forms an inductor to ground, coupling some energy to ground. This reduces the signal energy coupled to the next stage input through the transformer secondary coil, thereby further improving the accuracy of signal gain control.

7. The high-precision gain control circuit according to claim 1, characterized in that, The adjustable attenuation network includes transistor M S1 transistor M S1 The control signal is V c By controlling transistor M S1 The switching on and off of the network puts the adjustable attenuation network into the amplitude reference state and the amplitude attenuation state, respectively.

8. A high-precision gain control circuit according to claim 7, characterized in that, The adjustable attenuation network is based on a π-type attenuation network. A compensation circuit consisting of a compensation capacitor C0 and a switching transistor M0 connected in series is connected between the series resistors. The control signal for transistor M0 is V1.

9. A high-precision gain control circuit according to claim 7, characterized in that, The adjustable attenuation network is based on a π-type attenuation network, with a parallel compensation capacitor C connected to the branch resistance attenuating to ground. c .

10. A high-precision gain control circuit according to claim 9, characterized in that, The operating principle of the adjustable attenuation network is as follows: When the adjustable attenuation network is in the amplitude reference state, the phase control is implemented as follows: when V1=0, the equivalent capacitance C0 is equal to that of transistor M0 in the off state. M0 If they are connected in series, then their series equivalent capacitance is... When V1=1, it is equivalent to the equivalent resistance R of C0 and transistor M0 in the on state. M0 In series, where R M0 If it is approximately 0, then its equivalent capacitance C 02 It is equal to C0; therefore, it can be seen that the phase compensation capacitor is different in these two states, thus changing the transmission phase value of the amplitude reference state.

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