CN102324623B - Dual-band biorthogonal phase output power division feed network - Google Patents

Abstract

The invention discloses a dual-frequency dual-orthogonal phase output power splitting and feeding network, including a dual-frequency Wilkinson power splitter based on a left-hand composite transmission line, a dual-frequency 90-degree phase shifter based on a left-hand composite transmission line, a dielectric substrate and a floor metal layer . The feed network provides equal power at the two output ports, can provide a phase advance of 90 degrees at the uplink frequency of the Beidou satellite navigation system at 1.618 GHz, and provide a dual-orthogonal characteristic with a phase lag of 90 degrees at the downlink frequency of the Beidou satellite navigation system at 2.494 GHz. It has the characteristics of simple structure, easy processing, easy integration and small volume. The dual-frequency dual-orthogonal phase output power distribution feed network of the present invention can well meet the performance requirements of the power distribution feed network at both the uplink frequency and the downlink frequency of the Beidou satellite navigation system and provide a phase lead of 90 degrees and Provides dual-frequency dual-orthogonal characteristics with a phase lag of 90 degrees on the downlink frequency.

Description

A Dual Frequency Dual Quadrature Phase Output Power Divider Feed Network

technical field

The invention relates to a dual-frequency dual-orthogonal-phase output power division feeder network, which can be used as a feeder network for dual-frequency dual circularly polarized antennas in terminal equipment of a Beidou satellite navigation system.

Background technique

The satellite navigation industry is a national strategic high-tech industry. It is a typical technology-intensive and service-oriented IT industry. Its development prospects are very broad. It is the fastest growing information industry in the world after cellular mobile communications and the Internet. Another new growth point of the IT economy. The satellite and positioning GPS application industry represented by the US Global Positioning System GPS has gradually become a global high-tech industry. my country's satellite navigation industry is entering a critical moment of rapid industrialization development, and it is expected that a very large-scale market will be formed in the next five to ten years.

With the development of Beidou satellite navigation system, the demand for Beidou satellite navigation system will increase. Beidou satellite navigation system can provide satellite positioning service and data service at the same time, which is an important difference from other satellite navigation systems. The client of the Beidou satellite navigation system can receive satellite positioning signals through the system and can also send data information through the system, which requires the antenna of the client to have different circular polarization directions at the receiving and sending frequencies to reduce interference. This type of equipment usually uses two pairs of antennas to work at the transmitting frequency point and the receiving frequency point respectively, and uses different feeding networks to feed power to the receiving antenna and the transmitting antenna respectively.

However, the current design of the feed network that can provide different quadrature phases in the receiving and transmitting frequency bands at the same time has the following technical difficulties:

1. Dual-frequency dual-orthogonal technology for single-feed network

，而北斗卫星导航系统的上行频率和下行频率之间并不满足这种关系。所以用这种传输线实现的双频双正交网络不能作为北斗卫星导航系统的馈电网络。 Usually, a dual-feed point circularly polarized antenna working at both the uplink and downlink frequencies of the satellite communication system needs to use two feed networks and two feed ports to feed the antennas working at the uplink frequency and the downlink frequency respectively. This method requires the use of two feed networks. If a single feed network and a single feed port are to be used to feed two dual-feed point circularly polarized antennas operating at uplink frequencies and downlink frequencies, it is necessary to ensure that the feed The phases of the two output ports of the network on the uplink frequency and downlink frequency satisfy an orthogonal relationship. This orthogonal relationship also needs to meet the phase advance of 90 degrees and the phase lag of 90 degrees on the uplink frequency and downlink frequency of the Beidou satellite navigation system, so as to ensure that the circular polarization of the receiving and transmitting antennas is in the uplink of the Beidou satellite navigation system. The frequency is left-handed circular polarization, and the downlink frequency of Beidou satellite navigation system is right-handed circular polarization. In order to achieve this goal, it is assumed that the phase difference between the two output ports of the feeder network is 90 degrees ahead when the Beidou satellite navigation system is operating at the uplink frequency, and the phase difference between the two output ports of the feeder network is at the downlink frequency of the Beidou satellite navigation system. The difference is 90 degrees of lag. Because the traditional transmission line is a weak dispersion transmission line, the relationship between its phase characteristic and frequency is basically linear in a large frequency range. The relationship between the low-frequency and high-frequency operating frequency points of the dual-frequency dual-orthogonal network implemented by traditional transmission lines is generally

, while the uplink frequency and downlink frequency of the Beidou satellite navigation system do not satisfy this relationship. Therefore, the dual-frequency dual-orthogonal network realized by this transmission line cannot be used as the feed network of the Beidou satellite navigation system.

2. Miniaturization technology

Miniaturization technology is a big problem in the design of dual-frequency dual-orthogonal feeder network, because the dual-frequency dual-orthogonal feeder network realized by the traditional method requires two input ports and two feeder networks, which occupy a large circuit space. It is difficult to realize a dual-frequency dual-orthogonal feeder network with a single port and a single network using ordinary technology and ordinary transmission lines. It is usually necessary to design two different feed networks to feed two antennas with opposite operating frequencies and polarization directions respectively, and this feed method is relatively bulky. Orthogonal feed networks and antennas working at different frequencies complicate the terminal equipment and take up a lot of space.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a dual-frequency dual-orthogonal phase output power distribution feed network, so that the dual-frequency dual-orthogonal phase output power distribution feed network can be used as a satellite navigation system for Beidou satellite navigation. The feeding network of the dual-frequency dual-feed point circularly polarized antenna in the system realizes single-port feeding.

The invention realizes the dual-frequency Wilkinson power splitter based on the left-hand composite transmission line by using the left-hand composite transmission line, and realizes the dual-frequency 90-degree phase shifter based on the left-hand composite transmission line by using the microstrip transmission line and the left-hand composite transmission line, and in the dual-frequency Between the second port and the third port of the dual quadrature phase output power dividing feed network, the phase relationship on the two ports is realized to meet the requirement that the uplink frequency of the Beidou satellite navigation system is 90 degrees ahead and the downlink frequency is 90 degrees behind. Degree of dual frequency dual quadrature phase characteristics. In addition, due to the use of left-handed composite transmission lines with nonlinear phase characteristics, the invention also has the characteristics of miniaturization and easy processing.

The purpose of the present invention is achieved through the following technical solutions:

A dual-frequency dual-orthogonal phase output power division feed network, including a dual-frequency Wilkinson power splitter based on a left-hand composite transmission line, a dual-frequency 90-degree phase shifter based on a left-hand composite transmission line, a dielectric substrate and a floor metal layer; The dual-frequency Wilkinson power divider based on the left-hand composite transmission line and the dual-frequency 90-degree phase shifter based on the left-hand composite transmission line are attached to one side of the dielectric substrate, and the floor metal layer is attached to the other side of the dielectric substrate.

In the above-mentioned dual-frequency dual-orthogonal-phase output power divider feed network, the dual-frequency Wilkinson power divider includes a first microstrip transmission line, a second microstrip transmission line, a third microstrip transmission line, a first left-handed composite transmission line, a second Left and right hand composite transmission lines, the fourth microstrip transmission line, the fifth microstrip transmission line and isolation resistor R; one end of the first microstrip transmission line is used as the first port of the dual-frequency dual-orthogonal phase output power division feed network, the first microstrip The other end of the strip transmission line is connected to one end of the second microstrip transmission line and one end of the third microstrip transmission line; the other end of the second microstrip transmission line is connected to one end of the first left-hand composite transmission line, and the other end of the first left-hand composite transmission line is connected to the fourth One end of the microstrip transmission line, the other end of the fourth microstrip transmission line is used as the second port of the dual-frequency dual-orthogonal phase output power division feed network; the other end of the third microstrip transmission line is connected to one end of the second left-handed composite transmission line , the other end of the second left-hand composite transmission line is connected to one end of the fifth microstrip transmission line, the other end of the fifth microstrip transmission line is connected to one end of the third left-hand composite transmission line, the other end of the third left-hand composite transmission line is connected to the sixth microstrip transmission line, The other end of the six microstrip transmission lines is used as the third port of the dual-frequency dual-orthogonal phase output power dividing and feeding network; the isolation resistor R is connected between the fourth and fifth microstrip transmission lines.

In the above-mentioned dual-frequency dual-orthogonal phase output power-dividing feeder network, the left-hand composite transmission line is composed of one or more π-type units; when more than two π-type units are used to form the left-hand composite transmission line, the two The above π-type units are connected in series.

In the above-mentioned dual-frequency dual-orthogonal phase output power-dividing feed network, the first unit port of the π-type unit is at one end of the interdigitated capacitor, and the other end of the interdigitated capacitor is used as the second unit port of the π-type unit; the first One end of the short-circuit metal line is connected to the edge of the first unit port, the other end of the first short-circuit metal line is a metal via connected to the back of the medium, one end of the second short-circuit metal line is connected to the edge of the second unit port, and the second short-circuit metal line The other end of the line is a metal via that connects to the back of the dielectric.

；第一微带传输线、第四微带传输线、第五微带传输线、第六微带传输线和第三左右手复合传输线的特征阻抗为

；第二微带传输线、第三微带传输线、第一左右手复合传输线和第二左右手复合传输线的特征阻抗为

。 In the above-mentioned dual-frequency dual-orthogonal phase output power-dividing feeder network, the output impedances of the first to third ports of the dual-frequency dual-orthogonal phase output power-divider feeder network are:

; The characteristic impedance of the first microstrip transmission line, the fourth microstrip transmission line, the fifth microstrip transmission line, the sixth microstrip transmission line and the third left-handed composite transmission line is

; The characteristic impedances of the second microstrip transmission line, the third microstrip transmission line, the first left-hand composite transmission line and the second left-hand composite transmission line are

.

In the above-mentioned dual frequency dual quadrature phase output power distribution feed network, the phase relationship between the second port and the third port of the dual frequency dual quadrature phase output power distribution feed network satisfies the uplink frequency of the Beidou satellite navigation system The two frequency points of 1.618GHz and the downlink frequency of 2.492GHz are respectively 90 degrees ahead and 90 degrees behind.

In the above-mentioned dual-frequency dual-orthogonal phase output power division feed network, the transmission coefficient from the first port to the second port and the transmission coefficient from the first port to the third port of the dual-frequency dual-orthogonal phase output power division feed network The magnitude difference between the transmission coefficients is less than 0.3 dB at the two frequency points of 1.618GHz and 2.492GHz.

Compared with the prior art, the present invention has the following advantages and technical effects:

(1) The phase relationship between the second port and the third port of the dual-frequency dual-orthogonal phase output power distribution feed network of the present invention satisfies the two frequency points of the uplink frequency of 1.618GHz and the downlink frequency of 2.492GHz in the Beidou satellite navigation system They are 90 degrees ahead and 90 degrees behind.

(2) The dual-frequency dual-orthogonal phase output power division feed network achieves good power distribution and amplitude balance, and the dual-frequency dual-orthogonal phase output power division The magnitude difference between the transmission coefficient between the first port and the second port and the transmission coefficient between the first port and the third port of the feed network is less than 0.3 dB at both frequency points of 1.618GHz and 2.492GHz.

(3) The dual-frequency dual-orthogonal phase output power divider feed network achieves a smaller frequency ratio, that is, the average power distribution can be realized at two frequencies of 1.618 GHz and 2.492 GHz, and its operating frequency ratio It is 2.492/1.618.

(4) The phase difference between the second port and the third port of the dual-frequency dual-orthogonal phase output power distribution feed network realizes different orthogonal characteristics on the uplink frequency and downlink frequency of the Beidou satellite navigation system. Therefore, the feed network can be used as a dual-frequency dual-feed point antenna. The feed network can enable the dual-frequency dual-feed point antenna to achieve different circular polarizations at different operating frequencies.

(5) The dual-frequency dual-orthogonal phase output power division feeder network adopts the left-handed composite transmission line design, which realizes the miniaturization of the feeder network.

(6) The left and right hand composite transmission lines in the dual-frequency dual-orthogonal phase output power division feed network use interdigitated capacitors and short-circuit metal wires, which have the characteristics of integration, processing and low cost.

Description of drawings

Fig. 1a is a schematic structural diagram of a dual frequency dual quadrature phase output power division feed network in an embodiment.

Fig. 1b is a schematic diagram of the π-type unit structure of the left-handed composite transmission line in the embodiment.

Figure 2a is a graph of the return loss results of each port in the implementation.

Fig. 2b is a graph showing the results of insertion loss between the input port and the output port in the embodiment.

Figure 2c is a graph showing the isolation between output ports in the implementation.

Fig. 2d is a graph of the phase difference between the output ports in the embodiment.

Detailed ways

The implementation of the present invention will be described in detail below in conjunction with the accompanying drawings, but the scope of protection required by the present invention is not limited to the following embodiments.

As shown in Figure 1, the dual-frequency dual-orthogonal phase output power division feed network is implemented in the form of a microstrip circuit, including a first microstrip transmission line 1, a second microstrip transmission line 2, and a third microstrip transmission line 3 , the first left and right hand composite transmission line 4, the second left and right hand composite transmission line 5, the fourth microstrip transmission line 6, the fifth microstrip transmission line 7, the isolation resistor R connected across the fourth and fifth microstrip transmission lines, the third left and right hand composite transmission line 8 , the sixth microstrip transmission line 9; one end of the first microstrip transmission line 1 is used as the first port of the dual-frequency dual-orthogonal phase output power division feed network, and the other end of the first microstrip transmission line 1 is connected to the second microstrip One end of transmission line 2 and one end of third microstrip transmission line 3; One end, the other end of the fourth microstrip transmission line 6 is used as the second port of the dual-frequency dual-orthogonal phase output power division feed network; the other end of the third microstrip transmission line 3 is connected to one end of the second left and right hand composite transmission line 5, The other end of the second left and right hands composite transmission line 5 is connected to one end of the fifth microstrip transmission line 7, the other end of the fifth microstrip transmission line 7 is connected to one end of the third left and right hands composite transmission line 8, and the other end of the third left and right hands composite transmission line 8 is connected to the sixth microstrip transmission line. Take one end of the transmission line 9, and the other end of the sixth microstrip transmission line 9 is used as the third port of the dual-frequency dual-orthogonal phase output power division feed network; the isolation resistor R is connected across the fourth microstrip transmission line 6 and the fifth Between microstrip transmission lines 7.

；双频双正交相位输出功分馈电网络中的第二微带传输线2、第三微带传输线3的特征阻抗为

；第一左右手复合传输线4、第二左右手复合传输线5的特征阻抗为

；第三左右手复合传输线8的特征阻抗为

；隔离电阻R的阻抗值为2

； The characteristic impedance of the first microstrip transmission line 1, the fourth microstrip transmission line 6, and the fifth microstrip transmission line 7 of the dual-frequency dual-orthogonal phase output power division feed network is

; The characteristic impedance of the second microstrip transmission line 2 and the third microstrip transmission line 3 in the dual frequency dual quadrature phase output power division feed network is

; The characteristic impedance of the first left-hand composite transmission line 4 and the second left-hand composite transmission line 5 is

; The characteristic impedance of the third left and right hand composite transmission line 8 is

; The resistance value of the isolation resistor R is 2

;

The first to third left-hand composite transmission lines are composed of one or more π-type units in FIG. Refers to the two short-circuit metal wires at both ends of the capacitor; when more than two π-type units are used to form a left-handed composite transmission line, the two or more π-type units are connected in series; the interdigitated fingers in the two or more π-type units The capacitance parameters are consistent, and the parameters of the short-circuit metal wires in the two or more π-type units are consistent; the characteristic impedance and phase relationship of the left-hand composite transmission line are controlled by the parameters of one or more π-type units in the transmission line; The composite transmission line is exactly the same as the second left-hand composite transmission line. When two to four π-type units are used to form the first left-hand composite transmission line 4 or the second left-hand composite transmission line 5, the capacity of the interdigitated capacitance in the π-type unit is 0.6pF to 1.3pF, the inductance provided by the short-circuit metal lines 11 and 12 in the π-type unit is 6nH to 13 nH; when two to four π-type units are used to form the third left-hand composite transmission line 8, the interdigitated capacitance The capacity is 0.9pF to 2pF, and the inductance provided by the short-circuit metal lines 11 and 12 in the π-type unit is 4.4nH to 8.8nH.

The lengths of the fourth microstrip transmission line 6 and the fifth microstrip transmission line 7 are the same, and can be arbitrarily selected according to the circuit conditions connected to the feeding network. The length of the first microstrip transmission line 1 can be arbitrarily selected.

Example

The above description is clear to those skilled in the art, and the following content is only an embodiment, and is not intended to limit the protection scope of the present invention. The thickness of the dielectric substrate is 1.524mm, and the relative dielectric constant is 3.55. The ground of the dielectric substrate is a metal floor, and the other side is the dual-frequency dual-orthogonal phase output power divider feed network; the dual-frequency dual-orthogonal phase output power divider The output impedances of the first port, the second port, and the third port of the feed network are all 50 ohms; the characteristic impedances of the first microstrip transmission line 1, the fourth microstrip transmission line 6 and the fifth microstrip transmission line 7 are 50 ohms , with a width of 3.38mm. The characteristic impedance of the second microstrip transmission line 2 and the third microstrip transmission line 3 is 70.7 ohms, and the width is 1.875 mm. The characteristic impedance of the first left-hand composite transmission line 4 and the second left-hand composite transmission line 5 is 70.7 ohms. The first left-hand composite transmission line 4 and the second left-hand composite transmission line 5 are exactly the same, including three π-type units respectively. The total width of the interdigitated capacitance in each π-type unit is 1.875mm, and the length is 6.492mm. In each π-type unit, The finger width of the interdigitated capacitor is 0.125mm, and there are 4 pairs and 8 fingers in total, and the distance between the fingers is 0.125mm; the parameters of the short-circuit metal wire 11 and the short-circuit metal strip 12 in each π-type unit are exactly the same. The ends of metal strip 11 and short-circuit metal 12 are connected to the floor on the back of the substrate with metallized via holes. 12 has a length of 8.062mm.

The third left and right hand composite transmission line 8 has a characteristic impedance of 50 ohms, including three π-type units, the total width of the interdigitated capacitors in each π-type unit is 3.38mm, and the length is 5.386mm. The fingers of the interdigitated capacitors in each π-type unit The width is 0.125mm, there are 7 pairs and 14 fingers in total, and the distance between the fingers is 0.125mm; the parameters of the short-circuit metal wire 11 and the short-circuit metal strip 12 in each π-type unit are exactly the same, and the short-circuit metal strip 11 and the short-circuit metal strip 12 have the same parameters. The end of the metal strip 12 is connected to the floor on the back of the substrate with a metallized via hole. The diameter of the via hole is 0.5 mm. is 5.956mm.

The results obtained by using the parameters in the examples are shown in FIG. 2 .

It can be seen from Fig. 2a that the return loss of the first to third ports of the dual-frequency dual-orthogonal phase output power division feed network at the uplink and downlink operating frequency points of the Beidou satellite navigation system is less than -15dB, so in each The ports are well matched; Figure 2b shows the transmission coefficients from the first port to the second port and the first port to the third port, and it can be known from Figure 2b that the transmission coefficient amplitude value from the first port to the second port is between The uplink frequency of Beidou satellite is 1.618GHz, which is -3.36 dB, and the downlink frequency of Beidou satellite is 2.494 GHz, which is -3.30dB; similarly, it can be seen from Figure 2b that the amplitude value of the transmission coefficient from the first port to the third port is at the uplink frequency of the Beidou satellite navigation system. 1.618GHz is -3.75dB, and the downlink frequency 2.494GHz of the Beidou satellite navigation system is -3.49dB; The balance degree is 0.29dB at the uplink frequency of 1.618GHz of the Beidou satellite navigation system, and 0.19dB at the downlink frequency of 2.494GHz of the Beidou satellite navigation system, which shows that the feed network has achieved a good amplitude balance; Figure 2c draws the The isolation between the second port and the third port of the dual frequency dual quadrature phase output power division feed network. From Figure 2c, the isolation between the second port and the third port is 22.86dB at the uplink frequency of Beidou satellite navigation system 1.618GHz, and 22.25dB at the downlink frequency of Beidou satellite navigation system 2.494GHz, which shows that dual-frequency double-orthogonal Good isolation is achieved between the second port and the third port of the phase output power division feed network; Figure 2d shows the phase between the second port and the third port of the dual frequency dual quadrature phase output power division feed network Relationship, as shown in Figure 2d, the phase difference between the second port and the third port of the Beidou satellite navigation system with an uplink frequency of 1.618GHz is -90 degrees, and the phase difference between the second port and the third port of the Beidou satellite navigation system with a downlink frequency of 2.494GHz The phase difference between them is +90 degrees; this shows that the phase relationship between the second port and the third port of the dual-frequency dual-orthogonal phase output power distribution feed network on the uplink frequency and downlink frequency of the Beidou satellite navigation system is Orthogonal relationship; the above results illustrate that the present invention has realized the average distribution of power at the uplink frequency 1.618GHz of the Beidou satellite navigation system and the downlink frequency 2.494GHz of the Beidou satellite navigation system, and output power sharing in the dual-frequency dual-orthogonal phase On the second port and the third port of the electrical network, a bi-orthogonal phase relationship with a phase lead of 90 degrees and a phase lag of 90 degrees is formed respectively on the uplink frequency and the downlink frequency.

Claims (5)

1. A dual-frequency dual-orthogonal phase output power splitting and feeding network, including a dual-frequency Wilkinson power splitter based on a left-hand composite transmission line, a dual-frequency 90-degree phase shifter based on a left-hand composite transmission line, a dielectric substrate, and a floor metal layer; The dual-frequency Wilkinson power divider based on the left-hand composite transmission line and the dual-frequency 90-degree phase shifter based on the left-hand composite transmission line are attached to one side of the dielectric substrate, and the floor metal layer is attached to the other side of the dielectric substrate; the dual-frequency The Wilkinson power divider includes the first microstrip transmission line, the second microstrip transmission line, the third microstrip transmission line, the first left and right hand composite transmission line, the second left and right hand composite transmission line, the fourth microstrip transmission line, the fifth microstrip transmission line and the isolation resistor R ; One end of the first microstrip transmission line is used as the first port of the dual-frequency dual-orthogonal phase output power division feed network, and the other end of the first microstrip transmission line is connected to one end of the second microstrip transmission line and the third microstrip transmission line one end of the second microstrip transmission line; the other end of the second microstrip transmission line is connected to one end of the first left and right hand composite transmission line, and the other end of the first left and right hands composite transmission line is connected to one end of the fourth microstrip transmission line, and the other end of the fourth microstrip transmission line is used as the dual frequency The second port of the double quadrature phase output power division feed network; the other end of the third microstrip transmission line is connected to one end of the second left and right hand composite transmission line, and the other end of the second left and right hand composite transmission line is connected to one end of the fifth microstrip transmission line, the fifth The other end of the microstrip transmission line is connected to one end of the third left-hand composite transmission line, the other end of the third left-hand composite transmission line is connected to the sixth microstrip transmission line, and the other end of the sixth microstrip transmission line is used as the dual-frequency dual quadrature phase output power divider The third port of the feed network; the isolation resistor R is connected between the fourth and fifth microstrip transmission lines; the transmission coefficient from the first port to the second port is between the transmission coefficient from the first port to the third port The amplitude value difference of 1.618GHz and 2.492GHz are both less than 0.3 dB. 2. The dual-frequency dual-orthogonal phase output power distribution feed network according to claim 1 is characterized in that the left and right hand composite transmission line is composed of one or more π-type units; more than two π-type units are used to form the When the left-handed composite transmission line is described, the two or more π-type units are connected in series. 3. The dual frequency dual quadrature phase output power distribution feed network according to claim 2, characterized in that the first unit port of the π-type unit is at one end of the interdigitated capacitor, and the other end of the interdigitated capacitor is used as π The second unit port of the type unit; one end of the first short-circuit metal line is connected to the edge of the first unit port, the other end of the first short-circuit metal line is connected to the metal via on the back of the medium, and one end of the second short-circuit metal line is connected to the On the edge of the port of the second unit, the other end of the second short-circuit metal line is a metal via hole connected to the back of the medium. 4. according to the described dual-frequency dual-orthogonal phase output power distribution feed network of claim 1, it is characterized in that the output impedance of the first to the third port of the dual-frequency dual-orthogonal phase output power distribution feed network is

; The characteristic impedance of the first microstrip transmission line, the fourth microstrip transmission line, the fifth microstrip transmission line, the sixth microstrip transmission line and the third left-handed composite transmission line is

; The characteristic impedances of the second microstrip transmission line, the third microstrip transmission line, the first left-hand composite transmission line and the second left-hand composite transmission line are

. 5. The dual frequency dual quadrature phase output power distribution feed network according to claim 1, characterized in that the phase between the second port and the third port of the dual frequency dual quadrature phase output power distribution feed network The relationship satisfies the relationship that the two frequency points of the Beidou satellite navigation system, the uplink frequency 1.618GHz and the downlink frequency 2.492GHz, are 90 degrees ahead and 90 degrees behind.

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