Miniaturized image rejection mixer circuit

Abstract

The utility model discloses a miniaturized image rejection frequency mixing circuit, which comprises two passive double-balanced frequency mixers, a local oscillator bridge, a phase shift circuit and a power divider, the first input ends of the first passive double-balanced mixer and the second passive double-balanced mixer are connected with an external antenna; the second input end of the first passive double-balanced mixer is connected with the first output end of the local oscillator bridge, the second input end of the second passive double-balanced mixer is connected with the second output end of the local oscillator bridge, and the output end of the first passive double-balanced mixer is connected with the input end of the phase shift circuit. The output end of the second passive double-balanced mixer is connected with the second input end of the power divider; the isolation end of the local oscillator bridge is connected with the load resistor, and the input end of the local oscillator bridge is connected with the frequency source; the output end of the phase shift circuit is connected with the first input end of the power divider, and the output end of the power divider is connected with an external circuit. According to the utility model, the size of the image rejection mixer can be obviously reduced, and miniaturization design of a radar receiver is facilitated.

Description

Technical Field

[0001] The utility model relates to the technical field of mixers, and particularly relates to a miniaturized image rejection mixer circuit. Background Art

[0002] The radio frequency / local oscillator frequency is in the range of 14 GHz to 18 GHz, and the intermediate frequency is in the range of 30 MHz to 300 MHz (VHF band). There are two methods to achieve image frequency rejection: one is to use a filter to filter out the image frequency. Since the image frequency is within the radio frequency passband, it is impossible to use a filter to achieve image rejection; the other is to use a traditional mixer with image rejection and an external bridge circuit to achieve image rejection. Since the VHF band has a relatively low frequency, the size of the bridge circuit is large; the traditional mixer with image rejection and an external bridge circuit has a large size, high cost, and is not conducive to the miniaturization design of the radar system. Summary of the Utility Model

[0003] The utility model provides a miniaturized image rejection mixer circuit to overcome the technical problems of the traditional mixer with image rejection and an external bridge circuit, such as large size, high cost, and being not conducive to the miniaturization design of the radar system.

[0004] A miniaturized image rejection mixer circuit includes: two passive double-balanced mixers, a local oscillator bridge, a phase shift circuit, and a power divider;

[0005] The passive double-balanced mixers are respectively the first passive double-balanced mixer MIX 1 and the second passive double-balanced mixer MIX 2 ;

[0006] The local oscillator bridge is used to convert the received external local oscillator signal into two local oscillator signals with a phase difference of 90°, and respectively transmit them to the two passive double-balanced mixers; the two passive double-balanced mixers are used to subtract the received external radio frequency signal and the local oscillator signal input by the local oscillator bridge to obtain two intermediate frequency signals with a phase difference of 90°; the phase shift circuit is used to change the two intermediate frequency signals with a phase difference of 90° into two intermediate frequency signals with a phase difference of 180°; the power divider is used to synthesize the two intermediate frequency signals with a phase difference of 180° to cancel the image frequency;

[0007] The first input end of the first passive double-balanced mixer MIX 1 and the second passive double-balanced mixer MIX 2 is connected to the external antenna; the second input end of the first passive double-balanced mixer MIX 1 is connected to the first output end of the local oscillator bridge, the second input end of the second passive double-balanced mixer MIX 2 is connected to the second output end of the local oscillator bridge, and the first passive double-balanced mixer MIX1 The output end is connected to the input end of the phase shifter circuit, and the output end of the second passive double-balanced mixer MIX 2 is connected to the second input end of the power splitter;

[0008] The isolation end of the local oscillator bridge is connected to the load resistor, and the input end of the local oscillator bridge is connected to the frequency source;

[0009] The output end of the phase shifter circuit is connected to the first input end of the power splitter, and the output end of the power splitter is connected to the intermediate frequency filter and the intermediate frequency amplifier.

[0010] Further, the phase shifter circuit is two types of π-type phase shifter circuits or two types of T-type phase shifter circuits.

[0011] Further, the first π-type phase shifter circuit includes: a first capacitor C 1 , a first inductor L 1 and a second capacitor C 2 ;

[0012] One end of the first capacitor C 1 is respectively connected to the output end of the first passive double-balanced mixer MIX 1 and one end of the first inductor L 1 , and the other end of the first capacitor C 1 is grounded; the other end of the first inductor L 1 is respectively connected to one end of the second capacitor C 2 and the first input end of the power splitter; the other end of the second capacitor C 2 is grounded.

[0013] Further, the second π-type phase shifter circuit includes: a second inductor L 2 , a third inductor L 3 and a third capacitor C 3 ;

[0014] One end of the second inductor L 2 is respectively connected to the output end of the first passive double-balanced mixer MIX 1 and one end of the third capacitor C 3 , and the other end of the second inductor L 2 is grounded; the other end of the third inductor L 3 is respectively connected to one end of the third inductor L 3 and the first input end of the power splitter, and the other end of the third inductor L 3 is grounded.

[0015] Further, the first T-type phase shifter circuit includes: a fourth inductor L 4 , a fourth capacitor C4 and the fifth inductor L 5 ;

[0016] One end of the fourth inductor L 4 is connected to the output end of the first passive double-balanced mixer MIX 1 , and the other end is respectively connected to one end of the fourth capacitor C 4 and one end of the fifth inductor L 5 ; The other end of the fourth capacitor C 4 is grounded; The other end of the fifth inductor L 5 is connected to the first input end of the power divider.

[0017] Furthermore, the second T-type phase shifter circuit includes: a fifth capacitor C 5 , a sixth inductor L 6 and a sixth capacitor C 6 ;

[0018] One end of the fifth capacitor C 5 is connected to the output end of the first passive double-balanced mixer MIX 1 , and the other end is respectively connected to one end of the sixth inductor L 6 and one end of the sixth capacitor C 6 ; The other end of the sixth inductor L 6 is grounded; The other end of the sixth capacitor C 6 is connected to the first input end of the power divider.

[0019] Furthermore, the local oscillator bridge is a 90-degree bridge.

[0020] Beneficial effects: By designing a phase shifter circuit and a power divider to form a bridge replacement circuit to replace the intermediate frequency bridge of the traditional image rejection mixer, the present invention can significantly reduce the size of the image rejection mixer, which is beneficial to the miniaturization design of the radar receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 is a circuit schematic diagram of a miniaturized image rejection mixer circuit of the present invention;

[0023] Figure 2 is a principle block diagram of a conventional image rejection I / Q mixer;

[0024] Figure 3 These are schematic diagrams of bridge replacement circuits composed of two π-type phase-shifting circuits and power divider circuits of the present utility model;

[0025] Figure 4 These are schematic diagrams of bridge replacement circuits composed of two T-type phase-shifting circuits and power divider circuits of the present utility model;

[0026] Figure 5 This is the circuit diagram of a miniaturized image rejection mixer obtained by using a π-type phase-shifting circuit of the present utility model;

[0027] Figure 6 This is the circuit diagram of a miniaturized image rejection mixer obtained by using another π-type phase-shifting circuit of the present utility model;

[0028] Figure 7 This is the circuit diagram of a miniaturized image rejection mixer obtained by using a T-type phase-shifting circuit of the present utility model;

[0029] Figure 8 This is the circuit diagram of a miniaturized image rejection mixer obtained by using another T-type phase-shifting circuit of the present utility model;

[0030] Figure 9 This is the size diagram of the bridge in the VHF band in a conventional image rejection I / Q mixer;

[0031] Figure 10 This is a schematic diagram of the layout size of a miniaturized image rejection mixer circuit of the present utility model. Detailed implementation manners

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0033] This embodiment provides a miniaturized image rejection mixer circuit, as Figure 1 shown, including: two passive double-balanced mixers, a local oscillator bridge, a phase-shifting circuit, and a power divider;

[0034] The passive double-balanced mixers are respectively the first passive double-balanced mixer MIX 1 and the second passive double-balanced mixer MIX 2 ;

[0035] The local oscillator bridge is used to convert the received external local oscillator signal into two local oscillator signals with a 90° phase difference, and respectively transmit them to two passive double-balanced mixers; the two passive double-balanced mixers are used to subtract the received external radio frequency signal and the local oscillator signal input by the local oscillator bridge to obtain two intermediate frequency signals with a 90° phase difference; the phase shifter circuit is used to change the two intermediate frequency signals with a 90° phase difference into two intermediate frequency signals with a 180° phase difference; the power divider is used to synthesize the two intermediate frequency signals with a 180° phase difference to cancel the image frequency;

[0036] The first passive double-balanced mixer MIX 1 and the second passive double-balanced mixer MIX 2 have their first input terminals connected to an external antenna; the second input terminal of the first passive double-balanced mixer MIX 1 is connected to the first output terminal of the local oscillator bridge, the second input terminal of the second passive double-balanced mixer MIX 2 is connected to the second output terminal of the local oscillator bridge, the output terminal of the first passive double-balanced mixer MIX 1 is connected to the input terminal of the phase shifter circuit, and the output terminal of the second passive double-balanced mixer MIX 2 is connected to the second input terminal of the power divider;

[0037] The isolation terminal of the local oscillator bridge is connected to a load resistor, and the input terminal of the local oscillator bridge is connected to a frequency source;

[0038] The output terminal of the phase shifter circuit is connected to the first input terminal of the power divider, and the output terminal of the power divider is connected to an intermediate frequency filter and an intermediate frequency amplifier.

[0039] Specifically, the principle block diagram of a common image rejection I / Q mixer is as shown in Figure 2As shown, it consists of two passive double-balanced mixers, a local oscillator bridge, and an intermediate frequency bridge; the local oscillator bridge used in this embodiment is a 90-degree bridge; when the intermediate frequency is output in the VHF band, the intermediate frequency is relatively low, the size of the bridge is large, and it is difficult for the image rejection mixer to integrate a 90° bridge at the output. A phase shift circuit and a power divider are designed to form a bridge replacement circuit, which can replace the intermediate frequency bridge and reduce the size at the same time. The two passive double-balanced mixers receive the radio frequency signal transmitted from the outside and the two local oscillator signals with a 90° phase difference transmitted from the 90-degree local oscillator bridge, and subtract the local oscillator signal from the radio frequency signal to obtain the intermediate frequency signal with a 90° phase difference for realizing the image rejection function; the phase shift circuit includes two types of π-type phase shift circuits and T-type phase shift circuits, which are composed of different numbers of inductors and capacitors respectively, and can use the phase characteristics of the filter and the synthesis of the intermediate frequency power divider to replace the function of the bridge, realizing the function of equal amplitude and a 90° phase difference; at the same time, according to the project requirements, the phase and insertion loss of the phase shift circuit can be flexibly adjusted by adjusting the capacitance value and the inductance value.

[0040] In a specific embodiment, the phase shift circuit is a π-type phase shift circuit, including two types of π-type phase shift circuits, as Figure 3 shown;

[0041] The first type of π-type phase shift circuit is as Figure 5 shown, and includes: a first capacitor C 1 , a first inductor L 1 and a second capacitor C 2 ;

[0042] One end of the first capacitor C 1 is respectively connected to the output end of the first passive double-balanced mixer MIX 1 and one end of the first inductor L 1 , and the other end of the first capacitor C 1 is grounded; the other end of the first inductor L 1 is respectively connected to one end of the second capacitor C 2 and the first input end of the power divider; the other end of the second capacitor C 2 is grounded;

[0043] The second type of π-type phase shift circuit is as Figure 6 shown, and includes: a second inductor L 2 , a third inductor L 3 and a third capacitor C 3 ;

[0044] One end of the second inductor L 2 is respectively connected to the output end of the first passive double-balanced mixer MIX 1 and one end of the third capacitor C 3 , and the other end of the second inductor L 2The other end is grounded; the third inductor L 3 The other ends are respectively connected to the third inductor L 3 One end and the first input end of the power divider, and the other end of the third inductor L 3 Is grounded.

[0045] In this solution, two capacitors and one inductor are connected in series to form the first type of π-shaped phase-shifting circuit, which belongs to the low-pass filter circuit. Two inductors and one capacitor are connected in series to form the second type of π-shaped phase-shifting circuit, which belongs to the high-pass filter circuit. The phase characteristic of the filter and the synthesis of the intermediate-frequency power divider can be used to replace the function of the bridge, realizing the functions of equal amplitude and a phase difference of 90°; at the same time, according to the project requirements, the phase and insertion loss of the phase-shifting circuit can be flexibly adjusted by adjusting the capacitance value and the inductance value.

[0046] In a specific embodiment, the phase-shifting circuit is a T-shaped phase-shifting circuit, including two types of T-shaped phase-shifting circuits, as Figure 4 Shown;

[0047] The first type of T-shaped phase-shifting circuit is as Figure 7 Shown, including: the fourth inductor L 4 , the fourth capacitor C 4 And the fifth inductor L 5 ;

[0048] One end of the fourth inductor L 4 Is connected to the output end of the first passive double-balanced mixer MIX 1 , and the other end is respectively connected to one end of the fourth capacitor C 4 And one end of the fifth inductor L 5 ; The other end of the fourth capacitor C 4 Is grounded; the other end of the fifth inductor L 5 Is connected to the first input end of the power divider;

[0049] The second type of T-shaped phase-shifting circuit is as Figure 8 Shown, including: the fifth capacitor C 5 , the sixth inductor L 6 And the sixth capacitor C 6 ;

[0050] One end of the fifth capacitor C 5 Is connected to the output end of the first passive double-balanced mixer MIX 1 , and the other end is respectively connected to one end of the sixth inductor L 6 And one end of the sixth capacitor C 6 ; The other end of the sixth inductor L 6 Is grounded; the other end of the sixth capacitor C 6 Is connected to the first input end of the power divider.

[0051] In this solution, a T-type phase-shifting circuit composed of one capacitor and two inductors in series belongs to a low-pass filter circuit; a T-type phase-shifting circuit composed of one inductor and two capacitors in series belongs to a high-pass filter circuit; when the T-type circuit uses its phase-shifting characteristic, it has the same effect as a π-type phase-shifting circuit; when using its filtering characteristic, the frequency will produce different responses according to the sizes of the inductor and capacitor.

[0052] In this solution, the capacitors and inductors in the π-type phase-shifting circuit and the T-type phase-shifting circuit both adopt the 0201 package size;

[0053] In this embodiment, two passive image rejection mixers and one local oscillator bridge are integrated inside a single image rejection mixer, with a size of 1.65 mm × 1.05 mm; the size of a traditional VHF-band bridge is 25.4 mm × 12.7 mm; as Figure 9 shown, the capacitors and inductors in the phase-shifting circuit both adopt the 0201 package size of 2.5 mm × 1 mm; the size of the VHF-band power divider is 1.43 mm × 1.22 mm; the size of a traditional image rejection mixer is larger than 25.4 mm × 12.7 mm, and the layout size of the image rejection mixer of the present utility model is as Figure 10 shown, and the size can be reduced to 3.5 mm × 2.8 mm. Therefore, by using 0201 package capacitors and 0201 package wire-wound inductors and adopting a bare core for the power divider, the size can be greatly reduced, and while realizing image rejection, the size is reduced, which is beneficial to the miniaturized design of the radar receiver.

[0054] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present utility model, rather than to limit it; although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present utility model.

Claims

1. A miniaturized image rejection mixer circuit, characterized in that: include: Two passive double-balanced mixers, local oscillator bridge, phase shift circuit and power divider; The passive double-balanced mixers are respectively a first passive double-balanced mixer MIX1 and a second passive double-balanced mixer MIX2; The local oscillator bridge is used to convert the received external local oscillator signal into two local oscillator signals with a phase difference of 90°, and transmit them to two passive double-balanced mixers respectively; the two passive double-balanced mixers are used to subtract the received external radio frequency signal from the local oscillator signal input by the local oscillator bridge to obtain two intermediate frequency signals with a phase difference of 90°; the phase shift circuit is used to change the two intermediate frequency signals with a phase difference of 90° into two intermediate frequency signals with a phase difference of 180°; the power divider is used to synthesize the two intermediate frequency signals with a phase difference of 180° to offset the mirror frequency; The first input end of the first passive double balanced mixer MIX1 and the second passive double balanced mixer MIX2 are connected to an external antenna; the second input end of the first passive double balanced mixer MIX1 is connected to the first output end of the local oscillator bridge, the second input end of the second passive double balanced mixer MIX2 is connected to the second output end of the local oscillator bridge, the output end of the first passive double balanced mixer MIX1 is connected to the input end of the phase shift circuit, and the output end of the second passive double balanced mixer MIX2 is connected to the second input end of the power divider; The isolation end of the local oscillator bridge is connected to the load resistor, and the input end of the local oscillator bridge is connected to the frequency source; The output end of the phase shift circuit is connected to the first input end of the power divider, and the output end of the power divider is connected to the intermediate frequency filter and the intermediate frequency amplifier.

2. The miniaturized image rejection mixer circuit according to claim 1, characterized in that: The phase shift circuits are two π-type phase shift circuits or two T-type phase shift circuits.

3. The miniaturized image rejection mixer circuit according to claim 2, characterized in that: The first π-type phase shift circuit includes: a first capacitor C1, a first inductor L1 and a second capacitor C2; One end of the first capacitor C1 is respectively connected to the output end of the first passive double-balanced mixer MIX1 and one end of the first inductor L1, and the other end of the first capacitor C1 is grounded; the other end of the first inductor L1 is respectively connected to one end of the second capacitor C2 and the first input end of the power divider; the other end of the second capacitor C2 is grounded.

4. The miniaturized image rejection mixer circuit according to claim 2, characterized in that: The second π-type phase shift circuit includes: a second inductor L2, a third inductor L3 and a third capacitor C3; One end of the second inductor L2 is respectively connected to the output end of the first passive double-balanced mixer MIX1 and one end of the third capacitor C3, and the other end of the second inductor L2 is grounded; the other end of the third inductor L3 is respectively connected to one end of the third inductor L3 and the first input end of the power divider, and the other end of the third inductor L3 is grounded.

5. The miniaturized image rejection mixer circuit according to claim 2, characterized in that: The first T-type phase shift circuit includes: a fourth inductor L4, a fourth capacitor C4 and a fifth inductor L5; One end of the fourth inductor L4 is connected to the output end of the first passive double-balanced mixer MIX1, and the other end is respectively connected to one end of the fourth capacitor C4 and one end of the fifth inductor L5; the other end of the fourth capacitor C4 is grounded; the other end of the fifth inductor L5 is connected to the first input end of the power divider.

6. The miniaturized image rejection mixer circuit according to claim 2, characterized in that: The second T-type phase shift circuit includes: a fifth capacitor C5, a sixth inductor L6 and a sixth capacitor C6; One end of the fifth capacitor C5 is connected to the output end of the first passive double-balanced mixer MIX1, and the other end is respectively connected to one end of the sixth inductor L6 and one end of the sixth capacitor C6; the other end of the sixth inductor L6 is grounded; the other end of the sixth capacitor C6 is connected to the first input end of the power divider.

7. The miniaturized image rejection mixer circuit according to claim 1, characterized in that: The local oscillator bridge is a 90-degree bridge.

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