CN214851225U - Trap circuit for suppressing local oscillator leakage of frequency mixer - Google Patents
Trap circuit for suppressing local oscillator leakage of frequency mixer Download PDFInfo
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- CN214851225U CN214851225U CN202121449169.7U CN202121449169U CN214851225U CN 214851225 U CN214851225 U CN 214851225U CN 202121449169 U CN202121449169 U CN 202121449169U CN 214851225 U CN214851225 U CN 214851225U
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- 239000013078 crystal Substances 0.000 claims abstract description 25
- 239000010453 quartz Substances 0.000 claims abstract description 25
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 25
- 230000009466 transformation Effects 0.000 claims abstract description 4
- 238000004804 winding Methods 0.000 claims description 6
- 230000005611 electricity Effects 0.000 claims description 4
- 230000000694 effects Effects 0.000 abstract description 5
- 230000002401 inhibitory effect Effects 0.000 abstract description 3
- 230000010355 oscillation Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000000452 restraining effect Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
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Abstract
The utility model belongs to the field of radio frequency signal processing circuit, in particular to a trap circuit for inhibiting the leakage of a mixer local oscillator, which comprises a radio frequency input transformer and a radio frequency output transformer, and is characterized by also comprising a plurality of resonance circuits and LC network circuits, wherein the number of the resonance circuits and the LC network circuits is n, the resonance circuits comprise a plurality of quartz crystals connected in parallel, the frequency of the quartz crystals is consistent with the local oscillator frequency, the LC network circuit is an 1/4-wavelength impedance transformation circuit, the LC network circuits are connected with the resonance circuits in series at intervals, the output end of the radio frequency input transformer is electrically connected with the input end of the first resonance circuit, the electrical input end of the radio frequency output transformer is electrically connected with the output end of the last LC network circuit, and the trap circuit reaches a very high trap attenuation value through a plurality of iterations of the structure of the quartz crystals and the LC networks, the effect of inhibiting the local oscillation signals in the radio frequency signals input by the transformer is good.
Description
Technical Field
The utility model belongs to radio frequency signal processing circuit field, concretely relates to be used for restraining mixer local oscillator leakage trapper circuit.
Background
The mixer is an important component in rf technology, and the local oscillator signal driving level of the conventional passive or active mixer is large, which easily causes the problem of undesired local oscillator leakage, i.e. the coupled local oscillator signal appears at the output of the mixer. When the mixing working frequency of the mixer is far away from the local oscillator frequency, the leaked local oscillator signal can be filtered out easily through the filter network, but when the mixing working frequency of the system is close to the local oscillator signal frequency, the traditional filter network cannot.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a simple structure, effectual be used for suppressing mixer local oscillator leakage trapper circuit.
The technical solution to achieve the above object includes the following contents,
the utility model provides a trapper circuit for suppressing mixer local oscillator leaks, includes radio frequency input transformer and radio frequency output transformer, still includes several resonance circuit and LC network circuit, and resonance circuit and LC network circuit's quantity is the same for n, resonance circuit includes a plurality of parallelly connected quartz crystal, and quartz crystal's series resonance frequency is unanimous with local oscillator frequency, LC network circuit is 1/4 wavelength impedance transformation circuit, and LC network circuit and resonance circuit interval are established ties, and radio frequency input transformer's output is connected with first resonance circuit's input electricity, and radio frequency output transformer electric input is connected with last LC network circuit's output electricity.
Further, said n is equal to 3; the larger n is, the better the trap effect is, but the more complex the circuit structure is, and the proper iteration times are beneficial to ensuring the working stability of the circuit and the controllable volume of the device.
Further, the winding ratio of the radio frequency input transformer is 1:4, and the winding ratio of the radio frequency input transformer is 4: 1.
Further, the number of quartz crystals in the resonant circuit is 2-3.
The trap circuit forms an attenuation network through the quartz crystal, the series resonance characteristic of the quartz crystal is utilized, the quartz crystal can reach an extremely high Q value, the attenuation bandwidth can be extremely narrow, and the trap circuit can reach a very high trap attenuation value through repeated iteration of the structure of the quartz crystal and the LC network, and has a good effect of inhibiting local oscillation signals in radio frequency signals input by the transformer.
Drawings
FIG. 1 is a schematic diagram of an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of an embodiment of the present invention;
fig. 3 is a schematic diagram of the frequency response of the embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to examples.
Referring to fig. 1 and 2, a trap circuit for suppressing the local oscillator leakage of a mixer includes a radio frequency input transformer T1 and a radio frequency output transformer T2, and further includes 3 resonance circuits and 3 LC network circuits, where the resonance circuit includes 2 parallel quartz crystals Y, the series resonance frequency of the quartz crystals is consistent with the local oscillator frequency, the LC network circuit is a 1/4 wavelength impedance transformation circuit, the LC network circuit is connected in series with the resonance circuits at intervals, the output terminal of the radio frequency input transformer T1 is electrically connected to the input terminal of the first resonance circuit, and the input terminal of the radio frequency output transformer T2 is electrically connected to the output terminal of the last LC network circuit;
in this embodiment, the winding ratio of the radio frequency input transformer T1 is 1:4, and the winding ratio of the radio frequency input transformer T2 is 4: 1;
in the embodiment, the input impedance and the output impedance are all unified to be 50 ohms, the impedance of the radio frequency input impedance of 50 ohms is converted to be 200 ohms through a 4:1 transformer T1, so that the resistance of 200 ohms is connected with the quartz crystal Y1 in series, and the series resonance frequency of the quartz crystal is equivalent to pure resistance (the typical value of the series resonance of the quartz crystal is 20 ohms); according to the principle of resistance voltage division, a local oscillation signal generates 10-time attenuation on 200 ohms and a first quartz crystal Y1, the more quartz crystals Y are connected in parallel, the smaller the series resonance resistance formed by the quartz crystals Y is, the final result is that the attenuation value obtained by resistance voltage division is larger, but the attenuation quantity obtained by connecting a plurality of quartz crystals in parallel is limited, in order to improve the attenuation intensity of the trap filter, the impedance after resistance voltage division can be improved to more than 200 ohms again by using an equivalent 1/4 wavelength line circuit formed by an LC network, the series resonance resistance effect of the quartz crystals is repeatedly used for resistance voltage division, the structure of the quartz crystals and the LC network can be repeatedly iterated for many times to achieve a very high trap attenuation value, and finally, the radio frequency signal impedance is restored to 50 ohms by a 4:1 transformer at the output end of the trap filter;
in this embodiment, a standard 50MHz (actually measured series resonant frequency is 49.49224 MHz) is selected as the quartz crystal Y in the trap circuit, referring to fig. 3, when the trap circuit is used, the 3dB bandwidth of the circuit is 7.2KHz, the attenuation at its center frequency of 49.49224MHz is-60 dB, taking a passive mixer SLB-1 of typical Mini-circuit company as an example, the local oscillator leakage is-38 dBm, after-60 dB attenuation by the trap of this embodiment, the local oscillator signal leakage with only-98 dBm is finally output, and this can completely neglect the influence on the system after the whole mixing. It can be seen that the utility model discloses a trapper can obtain the effect of very good suppression local oscillator leakage.
Claims (4)
1. The utility model provides a trapper circuit for suppressing mixer local oscillator leaks, includes radio frequency input transformer and radio frequency output transformer, characterized by, still includes several resonance circuit and LC network circuit, and resonance circuit and LC network circuit's quantity is the same for n, resonance circuit includes a plurality of parallelly connected quartz crystal, and quartz crystal's frequency is unanimous with local oscillator frequency, LC network circuit is 1/4 wavelength impedance transformation circuit, and LC network circuit and resonance circuit interval are established ties, and radio frequency input transformer's output is connected with first resonance circuit's input electricity, and radio frequency output transformer electrical input is connected with last LC network circuit's output electricity.
2. The trap circuit for suppressing local oscillator leakage of a mixer of claim 1, wherein n is equal to 3.
3. A trap circuit for suppressing local oscillator leakage in a mixer as claimed in claim 1 or 2, wherein the number of quartz crystals in said resonant circuit is 2-3.
4. The trap circuit according to claim 1 or 2, wherein the winding ratio of the rf input transformer is 1:4, and the winding ratio of the rf input transformer is 4: 1.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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CN202121449169.7U CN214851225U (en) | 2021-06-29 | 2021-06-29 | Trap circuit for suppressing local oscillator leakage of frequency mixer |
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CN202121449169.7U CN214851225U (en) | 2021-06-29 | 2021-06-29 | Trap circuit for suppressing local oscillator leakage of frequency mixer |
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CN214851225U true CN214851225U (en) | 2021-11-23 |
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CN202121449169.7U Expired - Fee Related CN214851225U (en) | 2021-06-29 | 2021-06-29 | Trap circuit for suppressing local oscillator leakage of frequency mixer |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN113315539A (en) * | 2021-06-29 | 2021-08-27 | 桂林航天工业学院 | Trap circuit for suppressing local oscillator leakage of frequency mixer |
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2021
- 2021-06-29 CN CN202121449169.7U patent/CN214851225U/en not_active Expired - Fee Related
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN113315539A (en) * | 2021-06-29 | 2021-08-27 | 桂林航天工业学院 | Trap circuit for suppressing local oscillator leakage of frequency mixer |
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