High spurious suppression mixer circuit

Abstract

The invention discloses a high spurious suppression frequency mixing circuit which comprises a signal separation unit, a first frequency mixing unit, a second frequency mixing unit, a local oscillator separation unit, a signal synthesis unit and a radio frequency filtering unit. The other end of the signal separation unit is connected with one end of the first frequency mixing unit and one end of the second frequency mixing unit. The other end of the first frequency mixing unit and the other end of the second frequency mixing unit are connected with one end of the signal synthesis unit, and the other end of the signal synthesis unit is connected with the radio frequency filtering unit. One end of the local oscillator separation unit is connected with the first frequency mixing unit and the second frequency mixing unit. According to the invention, through the design of the signal separation module, the frequency mixing module, the synthesis module and the like, spurious signals generated in the frequency mixing process can be effectively reduced, through the design of the signal separation unit and the multiple frequency mixing units, the input signals are allowed to be subjected to multi-stage processing, and the system can adapt to signals with different frequencies and modulation modes, so that the clutter suppression level of the system is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave signal processing, and in particular relates to a high spurious suppression mixing circuit. Background Art

[0002] Upconversion technology is a technology that converts low-frequency signals into high-frequency signals. It is widely used in wireless communications, radar, audio and video processing and other fields. The main purpose of upconversion is to improve signal transmission efficiency, reduce interference, improve anti-noise ability, and meet the needs of different frequency spectra. The basic principle of upconversion is to mix the input low-frequency signal with a high-frequency signal (usually called a carrier signal) through a mixer to generate new frequency components. These new frequency components contain the information of the original signal and can be transmitted at a higher frequency band. In the upconversion process, it is often necessary to modulate the signal, such as amplitude modulation (AM), frequency modulation (FM) or phase modulation (PM), so as to transmit more efficiently in the high-frequency channel.

[0003] In the prior art, for example, the technical solution described in the patent with publication number CN114826306A is: a harmonic suppression circuit and a receiver, including a phase deflection circuit, a mixing unit and a phase cancellation circuit. The input signal is phase-deflected to generate a first signal and a second signal. The two deflected signals are mixed using the first and second local oscillator signals, and the mixed third and fourth signals are output. The third and fourth signals are phase-cancelled, and finally a clear signal is output.

[0004] In the prior art, when a low-frequency narrowband intermediate frequency signal is up-converted to a high-frequency broadband RF signal at one time, image frequencies, local oscillator leakage, and mixing intermodulation spurious signals appear in the RF broadband, which makes it impossible for the RF filter to effectively filter out these interferences. As a result, the suppression capability of the mixer itself becomes the only solution, but due to its low suppression efficiency, the spurious signal cannot be suppressed to meet the requirements of use. Summary of the invention

[0005] The purpose of the present invention is to provide a high spurious suppression mixer circuit to solve the problem in the prior art proposed in the background technology that the spurious signal cannot be filtered out and cannot meet the use requirements due to the low suppression efficiency of the suppression capability of the mixer itself.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A high spurious suppression mixing circuit comprises a signal separation unit, a first mixing unit, a second mixing unit, a local oscillator separation unit, a signal synthesis unit and a radio frequency filtering unit;

[0008] One end of the signal separation unit is used for intermediate frequency input; the other end of the signal separation unit is connected to one end of the first mixing unit and the second mixing unit respectively; the other ends of the first mixing unit and the second mixing unit are both connected to one end of the signal synthesis unit, and the other end of the signal synthesis unit is connected to the radio frequency filtering unit; the other end of the radio frequency filtering unit is used for radio frequency output;

[0009] One end of the local oscillator separation unit is connected to the first frequency mixing unit and the second frequency mixing unit respectively; the other end of the local oscillator separation unit is used for local oscillator input.

[0010] According to the above technical solution, the signal separation unit includes a first bridge; wherein one end of the first bridge is used for intermediate frequency input; and the other end of the first bridge is respectively connected to the first mixing unit and the second mixing unit.

[0011] According to the above technical solution, the first frequency mixing unit includes a first balun, a second bridge, a third bridge, a first mixer and a second mixer; wherein one end of the first balun is connected to the first bridge of the signal separation unit; the other end of the first balun is respectively connected to one end of the first mixer and one end of the second mixer; the other end of the first mixer is respectively connected to one end of the second bridge and one end of the third bridge, and the other end of the second mixer is respectively connected to one end of the second bridge and one end of the third bridge;

[0012] The other end of the second bridge is connected to the local oscillator separation unit; the other end of the third bridge is connected to the signal synthesis unit.

[0013] According to the above technical solution, the second mixing unit includes a second balun, a fourth bridge, a fifth bridge, a third mixer and a fourth mixer; wherein one end of the second balun is connected to the first bridge of the signal separation unit; the other end of the second balun is respectively connected to one end of the third mixer and the fourth mixer; the other end of the third mixer is respectively connected to one end of the fourth bridge and the fifth bridge, and the other end of the fourth mixer is respectively connected to one end of the fourth bridge and the fifth bridge;

[0014] The other end of the fourth bridge is connected to the local oscillator separation unit; the other end of the fifth bridge is connected to the signal synthesis unit.

[0015] According to the above technical solution, the signal synthesis unit includes a sixth bridge; one end of the sixth bridge is respectively connected to the third bridge of the first mixing unit and the fifth bridge of the second mixing unit, and the other end of the sixth bridge is connected to the RF filtering unit.

[0016] According to the above technical solution, the RF filtering unit includes a RF filter, one end of the RF filter is used to output the RF signal, and the other end of the RF filter is connected to the sixth bridge of the signal synthesis unit.

[0017] According to the above technical solution, the local oscillator separation unit includes a power divider, one end of which is used for inputting the local oscillator signal; the other end of the power divider is respectively connected to the second bridge of the first mixing unit and the fourth bridge of the second mixing unit.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] In the present invention, through the design of signal separation, mixing and synthesis modules, the stray signals generated in the mixing process can be effectively reduced. The design of the signal separation unit and multiple mixing units allows multi-level processing of the input signal, which can adapt to signals of different frequencies and modulation modes, thereby improving the dynamic range and sensitivity of the system. This enables the circuit to extract the required signal more accurately when facing strong signal interference; the design of the radio frequency filtering unit can effectively filter out unnecessary spectrum components, thereby improving the signal-to-noise ratio of the output signal and ensuring the quality of the final output signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a principle block diagram of the high spurious suppression mixer circuit of the present invention;

[0021] Figure 2 It is a schematic diagram of a high spurious suppression mixer circuit of the present invention;

[0022] Figure 3 This is a typical spurious suppression result diagram of the S-band double-balanced mixer of the present invention.

[0023] Markings in the figure: 100-signal separation unit, 101-first bridge, 200-first mixing unit, 201-first balun, 202-second bridge, 203-third bridge, 204-first mixer, 205-second mixer, 300-second mixing unit, 301-second balun, 302-fourth bridge, 303-fifth bridge, 304-third mixer, 305-fourth mixer, 400-local oscillator separation unit, 401-power divider, 500-signal synthesis unit, 501-sixth bridge, 600-RF filtering unit, 601-RF filter. DETAILED DESCRIPTION

[0024] 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 creative work are within the scope of protection of the present invention.

[0025] Embodiment 1

[0026] like Figure 1As shown, a high spurious suppression mixing circuit includes a signal separation unit 100, a first mixing unit 200, a second mixing unit 300, a local oscillator separation unit 400, a signal synthesis unit 500 and a radio frequency filtering unit 600;

[0027] One end of the signal separation unit 100 is used for intermediate frequency input; the other end of the signal separation unit 100 is connected to one end of the first mixing unit 200 and the second mixing unit 300 respectively; the other ends of the first mixing unit 200 and the second mixing unit 300 are both connected to one end of the signal synthesis unit 500, and the other end of the signal synthesis unit 500 is connected to the radio frequency filtering unit 600; the other end of the radio frequency filtering unit 600 is used for radio frequency output;

[0028] One end of the local oscillator separation unit 400 is connected to the first frequency mixing unit 200 and the second frequency mixing unit 300 respectively; the other end of the local oscillator separation unit 400 is used for local oscillator input.

[0029] In the present invention, through the design of signal separation, mixing and synthesis modules, the stray signals generated in the mixing process can be effectively reduced. The design of the signal separation unit 100 and multiple mixing units allows multi-level processing of the input signal, which can adapt to signals of different frequencies and modulation modes, thereby improving the system's clutter suppression level. This enables the circuit to more accurately extract the required signal when facing strong signal interference; the design of the RF filter unit 600 can effectively filter out unnecessary spectral components, thereby improving the signal-to-noise ratio of the output signal and ensuring the quality of the final output signal.

[0030] Embodiment 2

[0031] This embodiment is a further refinement of the first embodiment.

[0032] like Figure 2 As shown, the signal separation unit 100 includes a first bridge 101 ; one end of the first bridge 101 is used for intermediate frequency input; the other end of the first bridge 101 is connected to the first mixing unit 200 and the second mixing unit 300 respectively.

[0033] Furthermore, the first bridge 101 is a 0 / 90° bridge.

[0034] The first frequency mixing unit 200 includes a first balun 201, a second bridge 202, a third bridge 203, a first mixer 204 and a second mixer 205; wherein one end of the first balun 201 is connected to the first bridge 101 of the signal separation unit 100; the other end of the first balun 201 is connected to one end of the first mixer 204 and one end of the second mixer 205 respectively; the other end of the first mixer 204 is connected to one end of the first bridge 202 and one end of the third bridge 203 respectively, and the other end of the second mixer 205 is connected to one end of the second bridge 202 and one end of the third bridge 203 respectively;

[0035] The other end of the second bridge 202 is connected to the local oscillator separation unit 400 ; the other end of the third bridge 203 is connected to the signal synthesis unit 500 .

[0036] Furthermore, the first balun 201 is a 0 / 180° balun, and the second bridge 202 and the third bridge 203 are both 0 / 90° bridges.

[0037] The second frequency mixing unit 300 includes a second balun 301, a fourth bridge 302, a fifth bridge 303, a third mixer 304 and a fourth mixer 305; wherein one end of the second balun 301 is connected to the first bridge 101 of the signal separation unit 100; the other end of the second balun 301 is connected to one end of the third mixer 304 and the fourth mixer 305 respectively; the other end of the third mixer 304 is connected to one end of the fourth bridge 302 and the fifth bridge 303 respectively, and the other end of the fourth mixer 305 is connected to one end of the fourth bridge 302 and the fifth bridge 303 respectively;

[0038] The other end of the fourth bridge 302 is connected to the local oscillator separation unit 400 ; the other end of the fifth bridge 303 is connected to the signal synthesis unit 500 .

[0039] Furthermore, the second balun 301 is a 0 / 180° balun; the fourth bridge 302 and the fifth bridge 303 are both 0 / 90° bridges.

[0040] The signal synthesis unit 500 includes a sixth bridge 501 ; one end of the sixth bridge 501 is respectively connected to the third bridge 203 of the first mixing unit 200 and the fifth bridge 303 of the second mixing unit 300 , and the other end of the sixth bridge 501 is connected to the RF filtering unit 600 .

[0041] Furthermore, the sixth bridge 501 is a 0 / 90° bridge.

[0042] The RF filtering unit 600 includes a RF filter 601 , one end of the RF filter 601 is used to output a RF signal, and the other end of the RF filter 601 is connected to the sixth bridge 501 of the signal synthesis unit 500 .

[0043] The local oscillator separation unit 400 includes a power divider 401 , one end of which is used for inputting the local oscillator signal; the other end of the power divider 401 is connected to the second bridge 202 of the first frequency mixing unit 200 and the fourth bridge 302 of the second frequency mixing unit 300 .

[0044] Furthermore, the power divider 401 adopts an equal amplitude and equal phase power divider 401 .

[0045] Embodiment 3

[0046] This embodiment provides a specific signal transmission process: Figure 2 As shown, the intermediate frequency signal V1 generates two intermediate frequency signals V2 and V3 with equal amplitude and phase difference of 90° through the signal separation unit 100;

[0047] The intermediate frequency signal V2 is passed through the first balun 201 in the first mixing unit 200 to generate two intermediate frequency signals V4 and V5 with equal amplitude and a phase difference of 180°.

[0048] The intermediate frequency signal V3 is passed through the second balun 301 in the second mixing unit 300 to generate two intermediate frequency signals V6 and V7 with equal amplitude and a phase difference of 180°.

[0049] The local oscillator signal L0 generates two local oscillator signals with equal amplitude and phase difference of 0° through the local oscillator separation unit 400, one of which generates two local oscillator signals LO_1 and LO_2 with equal amplitude and phase difference of 90° through the second bridge 202 of the first frequency mixing unit 200. Similarly, the other generates two local oscillator signals LO_3 and LO_4 with equal amplitude and phase difference of 90° through the fourth bridge 302 of the second frequency mixing unit 300.

[0050] The intermediate frequency signal V4 is mixed with the local oscillator signal LO_1 by the first mixer 204 to generate a radio frequency signal R1 .

[0051] The intermediate frequency signal V5 is mixed with the local oscillation signal LO_2 by the second mixer 205 to generate a radio frequency signal R2.

[0052] The intermediate frequency signal V6 is mixed with the local oscillation signal LO_3 by the third mixer 304 to generate a radio frequency signal R3.

[0053] The intermediate frequency signal V7 is mixed with the local oscillation signal LO_4 by the fourth mixer 305 to generate a radio frequency signal R4.

[0054] The RF signals R1 and R2 are synthesized into a signal R5 through the third bridge 203 in the first frequency mixing unit 200 . Similarly, the RF signals R3 and R4 are synthesized into a signal R6 through the fourth bridge 302 in the second frequency mixing unit 300 .

[0055] The RF signals R5 and R6 are synthesized into a signal R7 by the sixth bridge 501 in the signal synthesis unit 500, and finally filtered by the RF filter unit 600 before being outputted externally.

[0056] The calculation for each signal is as follows:

[0057] Set the input intermediate frequency signal and local oscillator signal to:

[0058] V1=Acosω1t, L0=Bcosω2t;

[0059] According to the working principle of the mixer, the mixing intermodulation spurious frequency is m*I F+n*LO;

[0060] V2 = Acos(ω1t+90°);

[0061] V3=Acos(ω1t);

[0062] V4=V2+180°=Acos(ω1t+270°);

[0063] V5=V2+0°=Acos(ω1t+90°);

[0064] V6=V3+180°=Acos(ω1t+180°);

[0065] V7=V3+0°=Acos(ω1t);

[0066] LO_1=L0+0°+0°=Bcosω2t;

[0067] LO_2=L0+0°+90°=Bcos(ω2t+90°);

[0068] LO_3=L0+0°+0°=Bcosω2t;

[0069] LO_4=L0+0°+90°=Bcos(ω2t+90°);

[0070] The selected mixer models are the same, and the signal power and phase generated by the mixing are consistent, that is, the RF signal synthesized by the mixing:

[0071] R1=m*V4+n*LO_1=D1 cos{m*[ω1t+270°]+n*[ω2t+0°]};

[0072] R2=m*V5+n*LO_2=D1 cos{m*[ω1t+90°]+n*[ω2t+90°]};

[0073] R3=m*V6+n*LO_3=D1 cos{m*[ω1t+180°]+n*[ω2t+0°]};

[0074] R4=m*V7+n*LO_4=D1 cos{m*[ω1t]+n*[ω2t+90°]};

[0075] R5=R1+0°+R2+90°=D1 cos{m*[ω1t+270°]+n*[ω

[0076] 2t+0°]}+D1 cos{m*[ω1t+90°]+n*[ω2t+90°]+90°};

[0077] R6=R3+0°+R4+90°=D1 cos{m*[ω1t+180°]+n*[ω

[0078] 2t+0°]}+D1 cos{m*[ω1t]+n*[ω2t+90°]+90°};

[0079] R7=R5+0°+R6+90°=D1 cos{m*[ω1t+270°]+n*[ω

[0080] 2t+0°]}+D1 cos{m*[ω1t+90°]+n*[ω2t+90°]+90°}+D1 cos{m*[ω1t+180°]+n*[ω2t+0°]+90°}+D1 cos{m*[ω1t]+n*[ω2t+90°]+180°};

[0081] Calculate based on the mixed useful signal (1*LO+1*IF) and spurious signal (1*LO, 1*LO-1*IF, 1*LO+2*IF, 1*LO+3*IF):

[0082] 1) When m=1, n=1 (useful signal):

[0083] R7=D1 cos[ω1t+ω2t+270°]+D1 cos[ω1t+ω2t+270°]+D1 cos[ω

[0084] 1t+ω2t+270°]+D1 cos[ω1t+ω2t+270°]=4*D1*cos[ω1t+ω2t+270°];

[0085] 2) When m = 0, n = 1 (LO leakage spurious signal):

[0086] R7=D1 cos[ω2t]+D1cos[ω2t+180°]+D1 cos[ω

[0087] 2t+90°]+D1cos[ω2t+270°]=D1 cos[ω2t]-D1cos[ω2t]+D1 cos[ω2t+90°]-D1cos[ω2t+90°]=0;

[0088] 3) When m = -1, n = 1 (image frequency spurious signal): R7 = D1 cos [-ω1t + ω2t - 270°]} + D1cos {-ω1t + ω2t + 90°] + D1 cos [-ω1t + ω2t - 90°] + D1cos [-ω1t + ω2t + 270°] = 0;

[0089] 4) When m=2, n=1 (intermodulation signal): R7=D1 cos[2*ω1t+ω2t+540°]+D1 cos[2*ω1t+ω2t+360°]+D1cos[2*ω1t+ω2t+450°]+D1 cos{2*ω1t]+ω2t+270°}=-D1cos[2*ω1t+ω2t]+D1 cos[2*ω1t+ω2t]-D1cos[2*ω1t+ω2t+270°]+D1 cos[2*ω1t+ω2t+270°]=0;

[0090] 5) When m=3, n=1 (intermodulation signal): R7=D1cos[3ω1t+ω2t+810°]+D1 cos[3ω1t+ω2t+450°]+D1cos[3ω1t+ω2t+630°]+D1 cos[3ω1t+ω2t+270°]=2*D1 cos[3ω1t+ω2t+90°]+2*D1cos[3ω1t+ω2t-90°]=0.

[0091] In summary, the spurious signals such as the local oscillator leakage signal, the image signal, the intermediate frequency secondary and tertiary intermodulation signals and the local oscillator primary intermodulation signals cancel each other out, and the mixed useful signal is output normally.

[0092] This embodiment also provides a specific implementation method:

[0093] Now take the above 70MHz intermediate frequency signal as an example of up-converting to S-band signal, the intermediate frequency is 70MHz, the local oscillator frequency is 2130MHz~2330MHz, and the radio frequency is 2200MHz~2400MHz. The mixer output result is as follows Figure 3As shown, the spurious suppression for 1*LO, 1*LO-1*IF, 1*LO+2*IF, and 1*LO+3*IF are 0dBc, 30dBc, 46dBc, and 45dBc, respectively.

[0094] According to the comparison of actual test data, the local oscillator leakage signal and image signal suppression of the above circuit are increased by about 40dBc, and the suppression of the secondary and tertiary intermodulation signals of the intermediate frequency and the primary of the local oscillator is increased by about 20dBc; that is, the spurious suppression of 1*LO, 1*LO-1*IF, 1*LO+2*IF, and 1*LO+3*IF are 40dBc, 70dBc, 66dBc, and 65dBc respectively, which can meet the requirements of the whole machine.

[0095] In summary, the 70MHz intermediate frequency signal is up-converted to 2200MHz~2400MHz "once". Except for the image frequency spurious of 40dBc, the worst of the other spurious is 65dBc, which can meet the requirements of the whole machine.

[0096] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0097] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high spurious suppression mixer circuit, characterized in that: It comprises a signal separation unit (100), a first frequency mixing unit (200), a second frequency mixing unit (300), a local oscillator separation unit (400), a signal synthesis unit (500) and a radio frequency filtering unit (600); One end of the signal separation unit (100) is used for intermediate frequency input; the other end of the signal separation unit (100) is respectively connected to one end of the first frequency mixing unit (200) and the second frequency mixing unit (300); the other end of the first frequency mixing unit (200) and the second frequency mixing unit (300) are both connected to one end of the signal synthesis unit (500), and the other end of the signal synthesis unit (500) is connected to the radio frequency filtering unit (600); the other end of the radio frequency filtering unit (600) is used for radio frequency output; One end of the local oscillator separation unit (400) is respectively connected to the first frequency mixing unit (200) and the second frequency mixing unit (300); the other end of the local oscillator separation unit (400) is used for local oscillator input.

2. The high spurious suppression mixer circuit according to claim 2, characterized in that: The signal separation unit (100) comprises a first bridge (101); wherein one end of the first bridge (101) is used for intermediate frequency input; and the other end of the first bridge (101) is respectively connected to a first mixing unit (200) and a second mixing unit (300).

3. The high spurious suppression mixer circuit according to claim 2, characterized in that: The first frequency mixing unit (200) comprises a first balun (201), a second bridge (202), a third bridge (203), a first mixer (204) and a second mixer (205); wherein one end of the first balun (201) is connected to the first bridge (101) of the signal separation unit (100); the other end of the first balun (201) is respectively connected to one end of the first mixer (204) and one end of the second mixer (205); the other end of the first mixer (204) is respectively connected to one end of the second bridge (202) and one end of the third bridge (203); and the other end of the second mixer (205) is respectively connected to one end of the second bridge (202) and one end of the third bridge (203); The other end of the second bridge (202) is connected to the local oscillator separation unit (400); the other end of the third bridge (203) is connected to the signal synthesis unit (500).

4. The high spurious suppression mixer circuit according to claim 3, characterized in that: The second frequency mixing unit (300) comprises a second balun (301), a fourth bridge (302), a fifth bridge (303, a third mixer (304) and a fourth mixer (305); wherein one end of the second balun (301) is connected to the first bridge (101) of the signal separation unit (100); the other end of the second balun (301) is respectively connected to one end of the third mixer (304) and one end of the fourth mixer (305); the other end of the third mixer (304) is respectively connected to one end of the fourth bridge (302) and one end of the fifth bridge (303); and the other end of the fourth mixer (305) is respectively connected to one end of the fourth bridge (302) and one end of the fifth bridge (303); The other end of the fourth bridge (302) is connected to the local oscillator separation unit (400); and the other end of the fifth bridge (303) is connected to the signal synthesis unit (500).

5. The high spurious suppression mixer circuit according to claim 4, characterized in that: The signal synthesis unit (500) comprises a sixth bridge (501); one end of the sixth bridge (501) is respectively connected to the third bridge (203) of the first frequency mixing unit (200) and the fifth bridge (303) of the second frequency mixing unit (300), and the other end of the sixth bridge (501) is connected to the radio frequency filtering unit (600).

6. The high spurious suppression mixer circuit according to claim 5, characterized in that: The radio frequency filtering unit (600) comprises a radio frequency filter (601), one end of the radio frequency filter (601) is used to output a radio frequency signal, and the other end of the radio frequency filter (601) is connected to the sixth bridge (501) of the signal synthesis unit (500).

7. The high spurious suppression mixer circuit according to claim 6, characterized in that: The local oscillator separation unit (400) comprises a power divider (401), one end of the power divider (401) is used for inputting a local oscillator signal; the other end of the power divider (401) is respectively connected to the second bridge (202) of the first frequency mixing unit (200) and the fourth bridge (302) of the second frequency mixing unit (300).

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