A quadrature single-sideband mixer based on a passive negative resistance structure

Abstract

The present invention discloses an orthogonal single sideband mixer based on a passive negative resistance structure, belonging to the technical field of semiconductor integrated circuits. The orthogonal single sideband mixer comprises a first single sideband mixer (100), a second single sideband mixer (200), a first buffer (300) and a second buffer (400); wherein the first single sideband mixer (100) comprises a first mixing circuit (101), a second mixing circuit (102), a first adding circuit (103) and a first passive negative resistance (104); the first passive negative resistance (104) presents a normal LC structure in a small signal, has a low Q value and a wide operating frequency range; and presents a negative resistance characteristic in a large signal, increases the equivalent load Q value and enhances the frequency selectivity. The present invention has the advantages of taking both the operating frequency range and the frequency selectivity into consideration.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor integrated circuits, and in particular to an orthogonal single-sideband mixing device based on a passive negative resistance structure. Background Art

[0002] As an important electronic component, frequency synthesizer plays an important role in wireless transceivers. With the increase of communication frequency, more and more wireless protocols have emerged. In order to be compatible with more protocols, wireless transceivers based on software radio have become a research hotspot. This puts forward higher design requirements for frequency synthesizers, requiring frequency synthesizers to work in a wide frequency range while meeting the requirements of phase noise, spurious and frequency switching time.

[0003] In order to design a broadband frequency synthesizer in software radio, a phase-locked loop (PLL) loop is often combined with a post-frequency division circuit. This can reduce the design requirements for the PLL loop and only require a relatively narrow working range loop to avoid the loop working range being too wide, which will cause the loop parameters to change too much and is not conducive to optimization. The post-frequency division circuit mainly mixes and divides the output signal of the PLL loop to obtain a wider output frequency range within a limited input frequency range. At the same time, since general wireless transceivers use I / Q two-way working mode, a frequency synthesizer is required to provide an orthogonal local oscillator signal. Therefore, an orthogonal single-sideband mixer based on a passive negative resistance structure is often required in the post-frequency division circuit.

[0004] The orthogonal single-sideband mixer based on the passive negative resistance structure is generally based on the Gilbert structure of the double-balanced structure. The typical circuit structure is as follows: Figure 1(a) , 1(b) As shown, this structure can effectively suppress the input local oscillator signal.

[0005] In the prior art, there are two schemes for the structural design of the passive load of the orthogonal single-sideband mixer:

[0006] Technical Solution 1: One of the most widely used load structures is the LC load, which uses LC resonance to select frequencies. Only frequencies near the resonance point can be amplified, while other signals such as image signals will be suppressed.

[0007] The defect of this technical solution is that the operating frequency range of the LC load is affected by the Q value. When the Q value is large, the frequency selectivity is good, but the operating frequency range is narrow. When the Q value is small, the operating range is improved, but the frequency selectivity becomes worse.

[0008] Technical Solution 2: Another widely used load technology is LC cross negative resistance. This structure draws on the cross negative resistance in the voltage-controlled oscillator (VCO) structure. It generates negative resistance by crossing pairs of tubes, thereby increasing the load equivalent Q value and improving frequency selectivity.

[0009] The defects of this technical solution are: since this structure is based on the negative resistance structure in VCO, if the negative resistance value is too large, the whole circuit has the risk of oscillation. At the same time, similar to the first technical solution, this structure has the problem of contradiction between the working frequency range and the frequency selectivity. Although the negative resistance is used to improve the Q value, the frequency range in which the whole structure can work is narrowed, which is not suitable for the design of broadband frequency synthesizer circuit. Summary of the invention

[0010] In view of the problem that the existing single-sideband mixer load cannot take into account both the operating frequency range and frequency selectivity, the present invention proposes an orthogonal single-sideband mixer device based on a passive negative resistance structure, which has the advantage of taking into account both the operating frequency range and frequency selectivity.

[0011] The present invention provides an orthogonal single sideband mixer device based on a passive negative resistance structure, comprising a first single sideband mixer, a second single sideband mixer, a first buffer and a second buffer;

[0012] The first single-sideband mixer includes a first mixing circuit, a second mixing circuit, a first adding circuit and a first passive negative resistance;

[0013] The input signals of the first frequency mixing circuit are the first input signal and the third input signal; the input signals of the second frequency mixing circuit are the second input signal and the fourth input signal;

[0014] The first input signal and the third input signal are mixed by the first mixing circuit to obtain a first mixed signal; the second input signal and the fourth input signal are mixed by the second mixing circuit to obtain a second mixed signal;

[0015] The second mixing signal after 180-degree inversion is added to the first input signal by the first adding circuit, flows through the first passive negative resistance, and is output from the first buffer to obtain an output signal.

[0016] Preferably, the structures of the first single sideband mixer and the second single sideband mixer are completely consistent.

[0017] Preferably, the second single-sideband mixer comprises a third mixing circuit, a fourth mixing circuit, a second adding circuit and a second passive negative resistance;

[0018] The input signals of the third frequency mixing circuit are the fifth input signal and the seventh input signal; the input signals of the fourth frequency mixing circuit are the sixth input signal and the eighth input signal;

[0019] The fifth input signal and the seventh input signal are mixed by the third mixing circuit to obtain a third mixed signal; the sixth input signal and the eighth input signal are mixed by the fourth mixing circuit to obtain a fourth mixed signal;

[0020] After being added by the second adding circuit, the third mixing signal and the fourth mixing signal flow through the second passive negative resistance and are output from the second buffer to obtain a Q-channel output signal.

[0021] Preferably, the first input signal and the second input signal are orthogonal to each other;

[0022] The third input signal and the fourth input signal are orthogonal to each other.

[0023] Preferably, the input frequency of the first input signal and the second input signal is twice the input frequency of the third input signal and the fourth input signal.

[0024] Preferably, the output signal of the first buffer and the output signal of the second buffer are orthogonal to each other.

[0025] Preferably, the first buffer and the second buffer are fully differential structures.

[0026] Preferably, the first passive negative resistor includes a first MOS tube, a second MOS tube, a third MOS tube and a fourth MOS tube;

[0027] The first MOS transistor and the second MOS transistor are cross-coupled;

[0028] The source of the third MOS tube is connected to the source of the fourth MOS tube;

[0029] The gate of the third MOS tube is connected to the drain of the first MOS tube and the gate of the second MOS tube;

[0030] The gate of the fourth MOS tube is connected to the drain of the second MOS tube and the gate of the first MOS tube;

[0031] The drain of the third MOS tube is connected to the source of the first MOS tube;

[0032] The drain of the fourth MOS tube is connected to the source of the second MOS tube.

[0033] Preferably, the first single-sideband mixer further comprises a switched capacitor array and an inductor;

[0034] The switched capacitor array and the inductor are connected in parallel;

[0035] The switch capacitor array is controlled by an n-bit switch pair and is used to expand the frequency band of the orthogonal single-sideband mixing device; wherein n is a positive integer greater than 1.

[0036] Preferably, the n-bit switch pair adopts source attenuation to improve the linearity of the orthogonal single sideband mixing device.

[0037] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0038] The present invention adopts an orthogonal single-sideband mixer based on a passive negative resistance structure. The passive negative resistance structure presents normal LC characteristics under the condition of small signal swing, low Q value, and wide operating frequency range; when the signal swing increases, the load circuit enters the deep linear region, the circuit presents negative resistance characteristics, the equivalent load Q value increases, and the frequency selection capability is enhanced. Therefore, by adopting this structure in the orthogonal single-sideband mixer, both the operating frequency range and the frequency selection performance can be taken into account, and a good image suppression rate can be provided in a wide frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0040] FIG. 1( a ) is a schematic diagram of a circuit of a quadrature single sideband mixer I provided by the background technology of the present invention;

[0041] FIG1( b ) is a schematic diagram of a Q-path circuit of a quadrature single sideband mixer provided by the background technology of the present invention;

[0042] Figure 2 The LC load circuit schematic diagram provided as the background technology of the present invention;

[0043] Figure 3 A schematic diagram of a cross negative resistance structure circuit provided as the background technology of the present invention;

[0044] Figure 4 A schematic structural diagram of an orthogonal single sideband mixing device based on a passive negative resistance structure provided by an embodiment of the present invention;

[0045] Figure 5 A circuit schematic diagram of a passive negative resistance provided by an embodiment of the present invention;

[0046] Figure 6 A diagram showing simulation results of voltage, current and transient resistance in a passive negative resistance structure provided by an embodiment of the present invention;

[0047] Figure 7 A schematic diagram of the phasor representation of currents in a passive negative resistance structure provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0049] The embodiment of the present invention provides an orthogonal single sideband mixing device based on a passive negative resistance structure, such as Figure 4 As shown, it includes a first single sideband mixer 100, a second single sideband mixer 200, a first buffer 300 and a second buffer 400. The first buffer 300 and the second buffer 400 are fully differential structures.

[0050] Specifically, the first single-sideband mixer 100 includes a first mixing circuit 101, a second mixing circuit 102, a first adding circuit 103 and a first passive negative resistor 104; the input signal of the first mixing circuit 101 is a first input signal S In1 and the third input signal S In3 The input signal of the second mixer circuit 102 is the second input signal S In2 and the fourth input signal S In4 ; The first input signal S In1 and the third input signal S In3 After the mixing process by the first mixing circuit 101, the first mixing signal S Mix1 ; The second input signal S In2 and the fourth input signal S In4 After the mixing process by the second mixing circuit 102, the second mixing signal S Mix2 ; The second mixed signal S after 180 degrees inversion Mix2 With the first mixing signal S Mix1 After being added by the first adding circuit 103, the signals flow through the first passive negative resistor 104 and are output from the first buffer 300 to obtain an output signal S OutI .

[0051] The second single-sideband mixer 200 includes a third mixing circuit 201, a fourth mixing circuit 202, a second adding circuit 203 and a second passive negative resistor 204; the input signal of the third mixing circuit 201 is the fifth input signal S In5 and the seventh input signal S In7 The input signal of the fourth mixing circuit 202 is the sixth input signal S In6 and the eighth input signal S In8 ; The fifth input signal S In1 and the seventh input signal S In7 After the third mixing circuit 201 performs mixing processing, a third mixing signal S is obtained. Mix3 ; The sixth input signal S In6 and the eighth input signal S In8 After the mixing process by the fourth mixing circuit 202, a fourth mixing signal S is obtained. Mix4 ; The third mixing signal S Mix3 and the fourth mixing signal S Mix4 After being added by the second adding circuit 203, the signals flow through the second passive negative resistor 204 and are output from the second buffer 400 to obtain a Q-channel output signal S OutQ .

[0052] I-channel output signal S OutI And Q output signal S OutQ Mutually orthogonal.

[0053] Among them, the first input signal S In1 and the second input signal S In2 Mutually orthogonal; the third input signal S In3 and the fourth input signal S In4 mutually orthogonal; the fifth input signal S In5 and the sixth input signal S In6 mutually orthogonal; the seventh input signal S In7 and the eighth input signal S In8 Mutually orthogonal; the first input signal S In1 , the second input signal S In2 The input frequency is the third input signal S In3 , the fourth input signal S In4 The fifth input signal S In5 , the sixth input signal S In6 The input frequency is the seventh input signal S In7 , the eighth input signal S In8 The first input signal S In1 and the fifth input signal S In5 Exactly the same; the second input signal S In2 and the sixth input signal S In6Exactly the same; the third input signal S In3 and the eighth input signal S In8 Exactly the same; the fourth input signal S In4 and the seventh input signal S In7 Exactly the same.

[0054] For example, when the first input signal S In1 = cos(wt), the second input signal S In2 = sin(wt), the third input signal S In3 =cos(wt / 2), the fourth input signal S In4 = sin(wt / 2), the fifth input signal S In5 =cos(wt), the sixth input signal S In6 = sin(wt), the seventh input signal S In7 = sin(wt / 2), the eighth input signal S In8 =cos(wt / 2), so:

[0055] The first mixing signal S Mix1 =S In1 *S In3 =cos(wt)cos(wt / 2);

[0056] The first mixing signal S Mix2 =S In2 *S In4 = sin(wt)sin(wt / 2);

[0057] It follows that:

[0058] I-channel output signal S OutI =S Mix1 -S Mix2 =cos(wt)cos(wt / 2)-sin(wt)sin(wt / 2)=cos(3wt / 2);

[0059] Similarly, we get the Q output signal S OutQ =S Mix3 +S Mix4 =cos(wt)sin(wt / 2)+sin(wt)cos(wt / 2)=sin(3wt / 2).

[0060] Therefore, the output signal S OutI And Q output signal S OutQ Mutually orthogonal.

[0061] Furthermore, if Figure 5As shown, the first passive negative resistance 104 in the present invention includes a first MOS tube M1, a second MOS tube M2, a third MOS tube M3 and a fourth MOS tube M4; the first MOS tube M1 and the second MOS tube M2 are cross-coupled; the source of the third MOS tube M3 is connected to the source of the fourth MOS tube M4; the gate of the third MOS tube M3 is connected to the drain of the first MOS tube M1 and the gate of the second MOS tube M2; the gate of the fourth MOS tube M4 is connected to the drain of the second MOS tube M2 and the gate of the first MOS tube M1; the drain of the third MOS tube M3 is connected to the source of the first MOS tube M1; the drain of the fourth MOS tube M4 is connected to the source of the second MOS tube M2. In a specific embodiment, the first passive negative resistance 104 is also connected to the switch capacitor array 105 and the inductor L. Among them, one end of the switch capacitor array is connected to the drain of the first MOS tube M1, and the other end is connected to the drain of the second MOS tube M2; one end of the inductor L is connected to the drain of the first MOS tube M1, and the other end is connected to the drain of the second MOS tube M2.

[0062] Specifically, the switch capacitor array unit 105 includes one or at least two parallel capacitor branches, each switch capacitor branch is provided with a switch Ki (i=1, 2, 3, 4...n, n is a positive integer greater than 1) and two capacitors Ci (i=1, 2, 3, 4...n, n is a positive integer greater than 1) with equal capacitance, and the switch Ki is arranged between the two capacitors. For example, a switch K1 and two capacitors C1 with equal capacitance are arranged on the first switch capacitor branch, and the structure of other switch capacitor source branches is the same or similar to that of the first switch capacitor source branch, which will not be described one by one here. Multiple parallel switch capacitor branches are disconnected and controlled by digital control bits to adjust the capacitance value of the switch capacitor, so as to expand the frequency band of the orthogonal single-sideband mixer based on the passive negative resistance structure designed by the present invention. In addition, the n-bit switch pair adopts source attenuation to improve the linearity of the orthogonal single-sideband mixer of the present invention.

[0063] In this embodiment, Figure 5 The parameters involved are defined as follows:

[0064] i1: source-drain current of the third MOS tube M3;

[0065] i2: input current of the switched capacitor array;

[0066] i p : P-path input current of the current source;

[0067] i n : n-way input current of current source;

[0068] v a : The drain voltage of the third MOS tube M3;

[0069] v sg : The voltage between the power supply and the drain of the first MOS tube M1;

[0070] vout p : Output voltage at point m;

[0071] vout n : Output voltage at point n.

[0072] The working principle of passive negative resistance is: when vout p and vout n The swing is large, and M3 and M4 may enter the linear region. p When it decreases, vout n Increase, v a Increase; while vout p decrease, which means that the v sg increases, but at this time, the v of M3 sd If M3 works in the deep linear region, the source-drain current i1 of M3 is reduced. p The voltage between the power supply and the drain of M1 decreases. sg is increasing, but i1 is decreasing at this time, so negative resistance appears. The passive negative resistance simulation results are as follows Figure 6 As shown, in the area between the dotted line a and the dotted line b, v sg increases, but the current i1 decreases, so it presents a negative resistance.

[0073] Passive negative resistance will only appear when the swing reaches a certain level and forces M3 / M4 to enter the deep linear region. It will not appear actively when the swing is small. Therefore, compared with the traditional negative resistance structure, it will not form positive feedback under the influence of noise, which means that the risk of oscillation is reduced.

[0074] When the passive negative resistance is triggered, the Q value of the overall load will be increased. When the input current is constant, the larger the Q value, the larger the passive load impedance, resulting in a larger output swing. The increased output swing will cause M3 / M4 to enter the deep linear region for a longer time, further increasing the Q value and forming positive feedback. On the other hand, due to the current i p Fixed, there is a vector relationship between currents i1 and i2, such as Figure 7 As shown: When passive negative resistance appears, the current i p When the current i1 decreases, in order to satisfy this vector relationship, the current i2 will also decrease, thus reducing the swing amplitude at both ends of the resonant cavity, and then reducing the time for M3 / M4 to enter the linear region, forming a negative feedback. When these two mechanisms are balanced with each other, the circuit reaches a stable state.

[0075] The present invention mainly addresses the problem that the existing single-sideband mixer load cannot take into account both the operating frequency range and the frequency selectivity, and proposes an orthogonal single-sideband mixing device based on a passive load structure. The passive load structure in the present invention exhibits normal LC characteristics under the condition of small signal swing, with a low Q value and a wide operating frequency range. When the signal swing increases, the load circuit enters the deep linear region, the circuit exhibits a negative resistance characteristic, the equivalent load Q value increases, and the frequency selection capability is enhanced. Therefore, by adopting this structure in the orthogonal single-sideband mixing device, the present invention can take into account the advantages of the operating frequency range and frequency selectivity at the same time; in addition, within a very wide frequency range, the present invention can provide a larger image suppression rate.

[0076] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0077] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An orthogonal single sideband mixing device based on a passive negative resistance structure, characterized in that: The orthogonal single sideband mixing device comprises a first single sideband mixer (100), a second single sideband mixer (200), a first buffer (300) and a second buffer (400); The first single-sideband mixer (100) comprises a first mixing circuit (101), a second mixing circuit (102), a first adding circuit (103) and a first passive negative resistance (104); The input signal of the first mixer circuit (101) is a first input signal (S In1 ) and the third input signal (S In3 ); the input signal of the second mixing circuit (102) is the second input signal (S In2 ) and the fourth input signal (S In4 ); The first input signal (S In1 ) and the third input signal (S In3 ) is mixed by the first mixing circuit (101) to obtain a first mixed signal (S Mix1 ); the second input signal (S In2 ) and the fourth input signal (S In4 ) is mixed by the second mixing circuit (102) to obtain a second mixed signal (S Mix2 ); The second mixed signal (S Mix2 ) and the first input signal (S In1 ) are added by the first adding circuit (103), flow through the first passive negative resistor (104), and are output from the first buffer (300) to obtain an output signal (S OutI ); The second single-sideband mixer (200) comprises: a third mixing circuit (201), a fourth mixing circuit (202), a second adding circuit (203) and a second passive negative resistance (204); The input signal of the third mixer circuit (201) is the fifth input signal (S In5 ) and the seventh input signal (S In7 ); the input signal of the fourth mixer circuit (202) is the sixth input signal (S In6 ) and the eighth input signal (S In8 ); The fifth input signal (S In5 ) and the seventh input signal (S In7 ) is mixed by the third mixing circuit (201) to obtain a third mixed signal (S Mix3 ); the sixth input signal (S In6 ) and the eighth input signal (S In8 ) is mixed by the fourth mixing circuit (202) to obtain a fourth mixed signal (S Mix4 ); The third mixing signal (S Mix3 ) and the fourth mixing signal (S Mix4 ) are added by the second adding circuit (203), flow through the second passive negative resistor (204), and are output from the second buffer (400) to obtain a Q-channel output signal (S OutQ ); The first passive negative resistor (104) comprises: a first MOS tube (M1), a second MOS tube (M2), a third MOS tube (M3) and a fourth MOS tube (M4); The first MOS transistor (M1) and the second MOS transistor (M2) are cross-coupled; The source electrode of the third MOS tube (M3) is connected to the source electrode of the fourth MOS tube (M4); The gate of the third MOS tube (M3) is connected to the drain of the first MOS tube (M1) and the gate of the second MOS tube (M2); The gate of the fourth MOS transistor (M4) is connected to the drain of the second MOS transistor (M2) and the gate of the first MOS transistor (M1); The drain of the third MOS tube (M3) is connected to the source of the first MOS tube (M1); The drain of the fourth MOS transistor (M4) is connected to the source of the second MOS transistor (M2); The second passive negative resistance (204) structure is the same as the first passive negative resistance (104) structure.

2. The orthogonal single sideband mixer based on a passive negative resistance structure according to claim 1, characterized in that: The structures of the first single-sideband mixer (100) and the second single-sideband mixer (200) are completely consistent.

3. The orthogonal single sideband mixer based on a passive negative resistance structure according to claim 1, characterized in that: The first input signal (S In1 ) and the second input signal (S In2 ) are mutually orthogonal; The third input signal (S In3 ) and the fourth input signal (S In4 ) are mutually orthogonal.

4. The orthogonal single sideband mixer based on a passive negative resistance structure according to claim 1, characterized in that: The first input signal (S In1 ), the second input signal (S In2 ) is the input frequency of the third input signal (S In3 ), the fourth input signal (S In4 ) is twice the input frequency.

5. The orthogonal single sideband mixer based on a passive negative resistance structure according to claim 1, characterized in that: The output signal of the first buffer (300) and the output signal of the second buffer (400) are orthogonal to each other.

6. The orthogonal single sideband mixer based on a passive negative resistance structure according to claim 1, characterized in that: The first buffer (300) and the second buffer (400) are fully differential structures.

7. The orthogonal single sideband mixer based on a passive negative resistance structure according to claim 1, characterized in that: The first single-sideband mixer (100) further comprises a switched capacitor array (105) and an inductor (L); The switch capacitor array (105) and the inductor (L) are connected in parallel; The switch capacitor array (105) is controlled by an n-bit switch pair and is used to expand the frequency band of the orthogonal single-sideband mixing device; wherein n is a positive integer greater than 1.

8. The orthogonal single sideband mixer based on a passive negative resistance structure according to claim 7, characterized in that: The n-bit switch pair uses source attenuation to improve the linearity of the orthogonal single-sideband mixing device.

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