CN111092608A - Microwave isolator - Google Patents
Microwave isolator Download PDFInfo
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- CN111092608A CN111092608A CN201911120828.XA CN201911120828A CN111092608A CN 111092608 A CN111092608 A CN 111092608A CN 201911120828 A CN201911120828 A CN 201911120828A CN 111092608 A CN111092608 A CN 111092608A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/38—One-way transmission networks, i.e. unilines
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Abstract
The microwave isolator can solve the technical problems that the conventional ferrite microwave isolator is complex in structure, large in size, low in reliability, narrow in using frequency range and incapable of meeting requirements. The device comprises a front-stage attenuation network, a non-reciprocal semiconductor device and a rear-stage attenuation network; the preceding stage attenuation network is used as an input stage of the isolator and is connected with the preceding stage link; the rear-stage attenuation network is used as an output stage of the isolator and is connected with a rear-stage link; a radio frequency link formed from the input stage to the output stage is a transmission channel; electromagnetic shielding structures are arranged between input/output ends of the non-reciprocal semiconductor device and on two sides of a radio frequency link formed from an input stage to an output stage of the isolator. The invention adopts the semiconductor device, the working frequency range of the product is wide, the relative bandwidth is also wide, and the application range is wider; the operating frequency range of the invention is almost unlimited and can cover DC-terahertz, and as long as the semiconductor chip supports high operating frequency, the invention can be applied to high frequency range.
Description
Technical Field
The invention relates to the field of microwave circuit modules/components, in particular to a microwave isolator.
Background
In the field of microwave circuit module/assembly technology, there is a non-reciprocal device or circuit (microwave isolator for short) with microwave one-way transmission characteristic, which is basically characterized in that: as shown in fig. 1(a), microwave signals are transmitted with only a small loss in a predetermined direction, and with a large loss (isolation) in other directions.
Because of the unique characteristic of the microwave isolator, the microwave isolator is widely applied to various microwave circuit modules/components, subsystems and complete machines and is used for realizing the functions such as interstage isolation, crosstalk prevention, impedance matching, decoupling, transceiving duplex and the like, thereby achieving the purposes of protecting the system and effectively improving the stability and reliability of the system. Common application scenarios are as follows:
1) a microwave isolator is inserted between the front stage and the rear stage in the radio frequency link, so that the impedance matching of the front stage and the rear stage can be improved, the output power generated by the rear stage circuit is prevented from being reversely transmitted to the front stage to influence the normal working state of the front stage, and the front stage circuit is protected;
2) in the microwave transceiving circuit, a microwave isolator is used as a duplexer (as shown in fig. 1(B) below) to directly send a transmission signal to an antenna for transmission; while the received signal from the antenna will also enter the receiver directly. Without allowing the signal to reach the receiver directly from the transmitter, thereby protecting the receiver.
3) In power combining circuits (as shown in fig. 1(C) below), microwave isolators are often used to improve isolation of the combining system, preventing intermodulation caused by crosstalk between the two amplifiers.
In the middle of the last century, a major breakthrough in microwave technology was the discovery of ferrites. Ferrites are a class of ceramic magnetic materials composed of metal oxides. Because the ferrite gyromagnetic material is an anisotropic magnetic substance, the magnetic conductivity of the ferrite gyromagnetic material is changed along with an external magnetic field; under the combined action of an external microwave field and a constant direct-current magnetic field, the material generates gyromagnetic characteristics (also called tensor permeability characteristics). It is this gyromagnetic property that causes rotation of the polarization of the electromagnetic wave propagating in the ferrite (faraday effect) and strong absorption of the electromagnetic wave energy (ferromagnetic resonance). The circulator and the isolator are microwave unions (as shown in figure 2) developed by utilizing gyromagnetic characteristics of the material under the combined action of a direct-current magnetic field and a microwave field.
In which fig. 2(a) is a circulator. The microwave signal can only be transmitted in one direction, i.e. from 1 to 2, from 2 to 3 and from 3 to 1, is conductive. In turn signals from 2 to 1, from 3 to 2 and from 1 to 3 are isolated; when a 50 ohm load is connected to one port of the circulator, an isolator is formed as shown in fig. 2 (B).
The existing ferrite microwave isolator has the following defects:
1) the conventional working frequency range is 100 MHz-40 GHz, which can be realized theoretically below 100MHz, but the difficulty is that the magnetic moment of ferrite is required to be low, the requirement of a bias magnetic field is very low, the external dimension is very large, and the realization is difficult or even impossible. Meanwhile, the upper limit working frequency can also reach 100GHz theoretically, but because the working frequency is high, the processing precision of the product is difficult to guarantee, the production and debugging are difficult, and meanwhile, the size of the product is still large relative to the size of other devices in the same system, so that the upper limit working frequency is basically not adopted.
2) The relative working bandwidth of the product is narrow: usually < 50%, not suitable for broadband applications;
3) the ferrite isolator is large in size, cannot be applied to a plurality of systems or equipment with smaller space, and the lower the working frequency band, the larger the size, such as 80X 28 of the size of a 12-55MHz ferrite isolator of a certain company.
4) The structure is complicated, and the reliability is relatively low.
With the development of electronic equipment technology, the requirements on various microwave isolators are increasingly greater, and meanwhile, the index requirements on the isolators are higher and lower, and the size requirements are smaller and smaller, so that the isolators realized by using the traditional oxygen body technology system cannot meet the requirements of many modern systems. The above problems need to be solved.
Disclosure of Invention
The microwave isolator provided by the invention can solve the problems of the conventional ferrite microwave isolator, such as complex structure, large size, relatively low reliability, narrow use frequency range and incapability of meeting the requirements of many occasions.
In order to achieve the purpose, the invention adopts the following technical scheme:
a microwave isolator comprises a nonreciprocal semiconductor device and attenuation networks of front and rear stages;
the preceding stage attenuation network is used as an input stage of the isolator and is connected with the preceding stage link;
the rear-stage attenuation network is used as an output stage of the isolator and is connected with a rear-stage link;
a radio frequency link formed from the input stage to the output stage is a signal transmission channel;
and electromagnetic shielding structures are arranged on two sides of a radio frequency link formed from the input stage to the output stage.
Further, an electromagnetic shielding structure is also arranged between the input/output ends of the nonreciprocal semiconductor device.
Further, the non-reciprocal semiconductor device may be any device having a non-reciprocal property of signal transmission suitable for its application, such as a microwave amplifier, a mixer, an operational amplifier, and the like. .
Furthermore, the number of the transmission channels is n, and n is a natural number greater than or equal to 1;
each transmission channel is connected with a preceding-stage link through a isolator input attenuation network, and the output end of the non-reciprocal semiconductor device is connected with a subsequent-stage circuit through an output attenuation network;
the n transmission channels share a front-stage link as an input end, and then are respectively connected with corresponding rear stages through power dividers.
Further, the number n of the transmission channels is 2.
Further, the attenuation network can be any attenuation circuit with signal attenuation function suitable for the application, such as pi-type or T-type attenuation network formed by discrete resistor network, fixed attenuator chip and the like.
Furthermore, the multistage microwave isolator can be directly applied in a cascade mode to improve the unidirectional transmission characteristic of the system.
Further, the front-stage link and the back-stage link may be any microwave signal circuit suitable for the application, such as an amplifying link, a mixing link, a filter, or the like.
According to the technical scheme, the microwave isolator is designed by utilizing the microwave semiconductor device with the microwave transmission nonreciprocal characteristic.
When the frequency range is higher (such as more than or equal to 100MHz), the microwave unidirectional transmission characteristic can be realized by utilizing semiconductor devices such as a microwave amplifier, a mixer and the like which have microwave transmission nonreciprocal characteristics and matching with simple and proper peripheral circuits;
when the frequency band is low (such as <100MHz), the operational amplifier and its peripheral circuits can be used to realize the non-reciprocity of signal transmission.
When the unidirectional index requirement of the unidirectional circuit is very high, the following modes can be selected:
1) the multilevel microwave semiconductor devices with the microwave transmission nonreciprocal characteristic are used in a cascade mode;
2) proper attenuation networks are connected in series in front and at the back of a microwave semiconductor device with microwave transmission nonreciprocal characteristics;
3) the microwave one-way transmission characteristic can be prevented from being deteriorated due to space coupling and the like by the aid of other electromagnetic shielding structures.
Since the microwave unidirectional circuit design related to the invention does not relate to ferrite materials, the microwave unidirectional circuit design does not have the inherent defects of the ferrite isolator described in the background art.
The method has the advantages that:
1) the semiconductor device is adopted, and the ferrite technology is not adopted, so that the system integration level and the product reliability are improved;
2) by adopting the semiconductor device, the product has wide working frequency range, wide relative bandwidth and wider application range. To some extent, the operating frequency range of the microwave unidirectional circuit is almost unlimited, and the microwave unidirectional circuit can cover DC-terahertz, and can be applied to any high frequency range as long as the semiconductor chip supports any high operating frequency.
3) By adopting the semiconductor device, the degree of freedom of a design scheme is high, and the design scheme is easier to realize;
therefore, the microwave one-way circuit has the advantages of wide working frequency range, wide relative working bandwidth, small volume, simple structure, convenient application and the like. Can well meet the development requirement of miniaturized electronic devices.
Drawings
FIG. 1 is a schematic diagram of the existing features of a conventional microwave isolator;
FIG. 2 is a schematic structural diagram of a circulator and an isolator in the prior art;
FIG. 3 is a schematic structural view of the present invention;
FIG. 4 is a schematic structural diagram of a first embodiment of the present invention;
FIG. 5 is a schematic structural diagram of a second embodiment of the present invention;
FIG. 6 is a schematic diagram of a pi-type or T-type resistor network according to an embodiment of the invention;
fig. 7 is a signal transmission characteristic graph of an amplifier according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention.
As shown in fig. 1, the microwave isolator according to this embodiment includes a non-reciprocal semiconductor device and attenuation networks at front and rear stages;
the preceding stage attenuation network is used as an input stage of the isolator and is connected with the preceding stage link;
the rear-stage attenuation network is used as an output stage of the isolator and is connected with a rear-stage link;
a radio frequency link formed from the input stage to the output stage is a signal transmission channel;
electromagnetic shielding structures are arranged on two sides of a radio frequency link formed from the input stage to the output stage of the isolator;
an electromagnetic shielding structure is also arranged between the input/output ends of the nonreciprocal semiconductor device.
The non-reciprocal semiconductor device can be a microwave amplifier, a mixer, an operational amplifier and other semiconductor devices with non-reciprocal transmission characteristics.
The attenuation network can be a pi-type or T-type attenuation network formed by a discrete resistor network, can also be a fixed attenuator chip, or other circuits or networks with attenuation function.
The following is described in connection with specific applications:
example 1:
the schematic structural design of example 1 is shown in fig. 1. The embodiment is used for improving the reverse isolation from output to input in the radio frequency link on the premise of not changing other link characteristic indexes.
① is the front stage circuit in the RF link, ②④ is the optional attenuation network, ③ is the microwave amplifier circuit or the operational amplifier circuit (including the peripheral circuit), ⑤ is the back stage circuit in the RF link, ⑥ is the electromagnetic shielding structure on both sides of the RF link, ⑦ crosses the electromagnetic shielding structure of the microwave isolator.
Wherein the optional attenuator network shown at ②④ and the microwave amplifier circuit or operational amplifier circuit (including peripheral circuits) shown at ③ form a microwave isolator in this configuration.
Wherein, according to the working frequency of the microwave isolator, a microwave amplifier or an operational amplifier can be selected and adopted. When the working frequency is more than or equal to 100MHz, a microwave amplifier is selected; when the operating frequency is less than 100MHz, an operational amplifier is selected.
The optional attenuator network shown at ②④ has three functions, 1) impedance matching of the front and back stages, 2) adjusting the power level or dynamics of the rf link to prevent the circuits in the rf link from operating in a non-linear state, and 3) although the attenuator network does not have a unidirectional transmission characteristic, it does provide additional reverse isolation for the inverter.
The attenuation of the attenuation network shown in ②④ and the microwave amplifier circuit shown in ③ are designed according to the required electrical performance index requirements and by integrating various factors such as the unidirectional transmission characteristic requirements of the whole link, the dynamic ranges of front and rear active devices, the reverse transmission characteristics of the amplifier and the like.
The electromagnetic shielding structures on both sides of the rf link shown in ⑥ and the electromagnetic shielding structure across the microwave isolator shown in ⑦ are all for preventing the unidirectional transmission characteristics of the link from being deteriorated due to spatial coupling.
Example 2:
the schematic structural design of example 2 is shown in fig. 2. This embodiment is used to improve the mutual isolation between any output to input and two output ports (output I and output II) without changing other link characteristic indexes.
Compared with embodiment 1, embodiment 1 can only improve the one-way isolation degree from the output to the input in embodiment 2; while embodiment 2 can improve the unidirectional isolation from the output to the input, it can also improve the bidirectional isolation between the two output ports.
① shows a front-stage link of a radio frequency link, ② shows a power divider, ③ shows a front-stage attenuation network of two microwave isolators, ④ shows a non-reciprocal semiconductor device of the two microwave isolators, ⑤ shows a rear-stage attenuation network of the two microwave isolators, ⑥ shows a rear-stage link of the radio frequency link, ⑦ shows electromagnetic shielding structures on two sides of the radio frequency link, and ⑧ shows an electromagnetic shielding structure spanning the two microwave isolators.
Wherein the design principle of each microwave isolator circuit is the same as in example 1.
Assuming that the attenuation of the attenuator network ③⑤ is 10dB, the reverse isolation of the non-reciprocal semiconductor device ④ of each microwave isolator circuit is 20 dB.
The attenuation network can be realized by a resistor network of type or T-type under the condition that the working frequency is not too high, for example, the attenuation network with 10dB attenuation can be realized by the resistor network of type or T-type as shown in fig. 6.
In the non-reciprocal semiconductor device, an amplifier is used in embodiment 1, and SBB-5089 of Qorvo in usa is selected as a product, and signal transmission characteristics thereof are shown in fig. 7. The left graph S21 represents the forward transmission gain; s12 denotes reverse isolation. Therefore, the reverse isolation degree which can be realized by applying the device in the DC-4GHz range is more than or equal to 22.5 dB.
In some cases, it is necessary to use other devices having non-reciprocal transmission characteristics, such as a mixer.
The former stage circuit in the embodiment may be an amplifying chain or a mixing chain, and the latter stage circuit may be an amplifying chain, or a filter, etc. The circuit form is finally determined according to the actual application requirement.
The reverse isolation of each output to input of this example is increased by 40dB over the original link without the microwave isolator. The mutual isolation between the two outputs is also increased by 40 dB.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A microwave isolator is characterized in that: the attenuator comprises a non-reciprocal semiconductor device and attenuation networks of front and rear stages;
the preceding stage attenuation network is used as an input stage of the isolator and is connected with the preceding stage link;
the rear-stage attenuation network is used as an output stage of the isolator and is connected with a rear-stage link;
a radio frequency link formed from the input stage to the output stage is a signal transmission channel;
and electromagnetic shielding structures are arranged on two sides of a radio frequency link formed from the input stage to the output stage.
2. The microwave isolator according to claim 1, wherein: an electromagnetic shielding structure is also arranged between the input end and the output end of the nonreciprocal semiconductor device.
3. The microwave isolator of claim 2, wherein: the non-reciprocal semiconductor device is one of a microwave amplifier, a mixer, and an operational amplifier.
4. The microwave isolator according to claim 1, wherein: the number of the transmission channels is n, and n is a natural number which is more than or equal to 1;
each transmission channel is connected with a preceding-stage link through a isolator input attenuation network, and the output end of the non-reciprocal semiconductor device is connected with a subsequent-stage circuit through an output attenuation network;
the n transmission channels share a front-stage link as an input end, and then are respectively connected with corresponding rear stages through power dividers.
5. The microwave isolator of claim 4, wherein: the number of the transmission channels n = 2.
6. A microwave isolator as claimed in any one of claims 1 to 5, wherein: the attenuation network is one of a pi-type or T-type attenuation network formed by a discrete resistance network or a fixed attenuator chip.
7. The microwave isolator of claim 6, wherein: the pre-stage link and the post-stage link are one of an amplifying link, a mixing link or a filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911120828.XA CN111092608A (en) | 2019-11-15 | 2019-11-15 | Microwave isolator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911120828.XA CN111092608A (en) | 2019-11-15 | 2019-11-15 | Microwave isolator |
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| Publication Number | Publication Date |
|---|---|
| CN111092608A true CN111092608A (en) | 2020-05-01 |
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| CN201911120828.XA Pending CN111092608A (en) | 2019-11-15 | 2019-11-15 | Microwave isolator |
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