A local oscillator circuit for miniaturized ODU transmission channel

Abstract

The present invention discloses a local oscillator circuit for a miniaturized ODU transmission channel, comprising a frequency synthesizer, a frequency multiplier, a local oscillator amplifier and a local oscillator filter connected in series in sequence, wherein the first reference source input end of the frequency synthesizer is electrically connected to an external reference source, the numerical control interface of the frequency synthesizer is electrically connected to a single-chip microcomputer correspondingly, the single-chip microcomputer inputs a frequency control parameter to the frequency synthesizer through the numerical control interface, the frequency multiplier performs a double frequency multiplication on the signal output by the frequency synthesizer to generate a local oscillator signal of a required frequency, and then the local oscillator amplifier performs a power amplification on the local oscillator signal, and then the local oscillator filter suppresses and filters the fundamental wave and the third harmonic in the local oscillator signal. The local oscillator circuit is applied to a satellite communication transmission channel, and can change the required local oscillator signal frequency by parameter configuration, and has the advantages of stability, reliability, power saving, volume reduction, and cost reduction.

Description

Technical Field

[0001] The invention belongs to the technical field of communications, and in particular relates to a local oscillator circuit suitable for a miniaturized ODU transmission channel of satellite communications. Background Art

[0002] In satellite communication equipment, ODU (Out-door Unit) refers to the outdoor unit, which mainly includes frequency conversion and power amplification. It can be divided into transmitting channel and receiving channel. The transmitting channel usually refers to BUC (Block Up-Converter), that is, the up-conversion power amplifier, and the receiving channel mainly refers to LNB (Low Noise Block down-converter), that is, the low noise amplifier and frequency converter.

[0003] In the transmission channel, a local oscillator circuit is usually required as an oscillation signal source. In miniaturized applications, the size and power consumption of the local oscillator circuit must be low, and the output frequency must have good characteristics in the microwave frequency band. For example, various indicators such as working bandwidth, frequency conversion time, phase noise, spurious signals, and frequency resolution must meet design requirements. Summary of the invention

[0004] The main technical problem solved by the present invention is to provide a local oscillator circuit for a miniaturized ODU transmission channel, solving the problems in the prior art of inconvenient frequency regulation, complex circuit composition, many components and high power consumption.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is to provide a local oscillator circuit for a miniaturized ODU transmission channel, including a frequency synthesizer, a frequency multiplier, a local oscillator amplifier and a local oscillator filter connected in series in sequence, the first reference source input end of the frequency synthesizer is used to be electrically connected to an external reference source, the external reference source inputs a reference frequency signal to the frequency synthesizer through the first reference source input end, the digital control interface of the frequency synthesizer is electrically connected to a single-chip microcomputer, the single-chip microcomputer inputs a frequency control parameter to the frequency synthesizer through the digital control interface, the frequency multiplier doubles the signal output by the frequency synthesizer to generate a local oscillator signal of the required frequency, and then the local oscillator amplifier performs power amplification on the local oscillator signal, and then the local oscillator filter suppresses and filters the fundamental wave and the third harmonic in the local oscillator signal.

[0006] In another embodiment of the local oscillator circuit for a miniaturized ODU transmission channel of the present invention, the frequency synthesizer includes a chip ADF4355, the first reference source input terminal of the frequency synthesizer corresponds to the REFINA terminal of the chip ADF4355, the digital control interface of the frequency synthesizer corresponds to the SPI interface of the chip ADF4355, and the SPI interface correspondingly includes an enable terminal, a data terminal and a clock terminal.

[0007] In another embodiment of the local oscillator circuit for a miniaturized ODU transmission channel of the present invention, a loop filter is arranged between the CPOUT terminal and the VTUNE terminal of the chip ADF4355, and the loop filter correspondingly includes a first filter resistor connected in series between the CPOUT terminal and the VTUNE terminal, a first filter capacitor and a second filter capacitor are connected in parallel to the CPOUT terminal, the other end of the first filter capacitor is grounded, the other end of the second filter capacitor is connected in series with a second filter resistor, the other end of the second filter resistor is grounded, a third filter capacitor is connected in parallel to the VTUNE terminal, and the other end of the third filter capacitor is grounded.

[0008] In another embodiment of the local oscillator circuit for a miniaturized ODU transmission channel of the present invention, the single-chip microcomputer is a chip ATTINY9, and the enable terminal, data terminal and clock terminal of the SPI interface of the chip ADF4355 correspond to the LE terminal, DATA terminal and CLK terminal, and the LE pin, DATA pin and CLK pin corresponding to the chip ATTINY9 are electrically connected respectively through serial interface resistors.

[0009] In another embodiment of the local oscillator circuit for miniaturized ODU transmission channel of the present invention, the frequency multiplier includes a chip HMC369, and a matching attenuator is further provided between the RFOUTA+ terminal of the chip ADF4355 and the RFin terminal of the chip HMC369.

[0010] In another embodiment of the local oscillator circuit for a miniaturized ODU transmission channel of the present invention, the local oscillator amplifier includes a chip CHA3666.

[0011] In another embodiment of the local oscillator circuit for a miniaturized ODU transmission channel of the present invention, the RF input end of the chip CHA3666 is electrically connected to the output end of the matching attenuation chip TGL4201, the input end of the matching attenuation chip TGL4201 is connected to the output port of the chip HMC369 through a gold ribbon, and the RF output end of the chip CHA3666 is connected to the input end of the local oscillator filter through another gold ribbon.

[0012] In another embodiment of the local oscillator circuit for a miniaturized ODU transmission channel of the present invention, the local oscillator filter is a microstrip filter.

[0013] In another embodiment of the local oscillator circuit for a miniaturized ODU transmission channel of the present invention, the microstrip filter includes 7 U-shaped microwave metal strips arranged on a ceramic substrate, the microwave metal strips are arranged in sequence and are centrally symmetrically distributed, wherein the first microwave metal strip opens upward and is located at the center of symmetry, the second microwave metal strip and the third microwave metal strip both open downward and are respectively located on the left and right sides of the first microwave metal strip, the fourth microwave metal strip opens upward and is located on the left side of the second microwave metal strip, the fifth microwave metal strip opens upward and is located on the right side of the third microwave metal strip, the sixth microwave metal strip opens downward and is located on the left side of the fourth microwave metal strip, the left branch of the sixth microwave metal strip extends laterally to form a first port, the seventh microwave metal strip opens downward and is located on the right side of the fifth microwave metal strip, and the right branch of the seventh microwave metal strip extends laterally to form a second port.

[0014] In another embodiment of the local oscillator circuit for miniaturized ODU transmission channel of the present invention, the reference frequency signal input by the external reference source to the chip ADF4355 is a 10 MHz signal, the output frequency of the chip ADF4355 is 6.4 GHz, and the output frequency of the chip HMC369 is 12.8 GHz.

[0015] The beneficial effects of the present invention are as follows: the present invention discloses a local oscillator circuit for a miniaturized ODU transmission channel, characterized in that it comprises a frequency synthesizer, a frequency multiplier, a local oscillator amplifier and a local oscillator filter connected in series in sequence, the first reference source input end of the frequency synthesizer is used to be electrically connected to an external reference source, the external reference source inputs a reference frequency signal to the frequency synthesizer through the first reference source input end, the digital control interface of the frequency synthesizer is electrically connected to a single-chip microcomputer correspondingly, the single-chip microcomputer inputs a frequency control parameter to the frequency synthesizer through the digital control interface, the frequency multiplier performs a double frequency multiplication on the signal output by the frequency synthesizer to generate a local oscillator signal of the required frequency, and then the local oscillator amplifier performs a power amplification on the local oscillator signal, and then the local oscillator filter suppresses and filters the fundamental wave and the third harmonic in the local oscillator signal. The local oscillator circuit is applied to a satellite communication transmission channel, and can change the required local oscillator signal frequency by parameter configuration, and has the advantages of stability, reliability, power saving, volume reduction, and cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a block diagram of a local oscillator circuit for a miniaturized ODU transmission channel according to an embodiment of the present invention;

[0017] Figure 2 It is an input interface circuit diagram of another embodiment of the local oscillator circuit for miniaturized ODU transmission channel of the present invention;

[0018] Figure 3It is a circuit diagram of a loop filter in another embodiment of a local oscillator circuit for a miniaturized ODU transmission channel of the present invention;

[0019] Figure 4 It is a power supply circuit diagram of another embodiment of the local oscillator circuit used for a miniaturized ODU transmission channel of the present invention;

[0020] Figure 5 It is a circuit diagram of the electrical connection between the frequency synthesizer and the frequency multiplier in another embodiment of the local oscillator circuit for the miniaturized ODU transmission channel of the present invention;

[0021] Figure 6 It is a circuit diagram of a local oscillator amplifier in another embodiment of a local oscillator circuit for a miniaturized ODU transmission channel of the present invention;

[0022] Figure 7 It is a circuit diagram of a local oscillator microstrip filter in another embodiment of a local oscillator circuit for a miniaturized ODU transmission channel of the present invention. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings and specific embodiments. Preferred embodiments of the present invention are provided in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0024] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0025] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. Figure 1 FIG. 1 is a schematic diagram of an embodiment of a local oscillator circuit for a miniaturized ODU transmission channel according to the present invention. Figure 1As shown, the local oscillator circuit 10 includes a frequency synthesizer 13, a frequency multiplier 14, a local oscillator amplifier 15 and a local oscillator filter 16 connected in series in sequence. The first reference source input terminal 131 of the frequency synthesizer 13 is used to be electrically connected to an external reference source 11. The external reference source 11 inputs a reference frequency signal to the frequency synthesizer 13 through the first reference source input terminal 131. The numerical control interface 132 of the frequency synthesizer 13 is electrically connected to the single-chip microcomputer 12. The single-chip microcomputer 12 inputs a frequency control parameter to the frequency synthesizer 13 through the numerical control interface 132. The frequency multiplier 14 doubles the signal output by the frequency synthesizer 13 to generate a local oscillator signal of the required frequency. Then the local oscillator amplifier 15 performs power amplification on the local oscillator signal. Then the local oscillator filter 16 performs suppression filtering on the fundamental wave and the third harmonic in the local oscillator signal.

[0026] for Figure 1 In the illustrated embodiment, the external reference source 11 inputs a reference frequency signal to the frequency synthesizer 13 via the first reference source input terminal 131 , and the single chip microcomputer 12 can input a frequency control parameter to the frequency synthesizer 13 via a numerical control interface 132 .

[0027] use Figure 1 The local oscillator circuit shown, on the one hand, can make the frequency output of the frequency synthesizer changeable by writing the frequency control parameters to the frequency synthesizer through the single chip microcomputer, so the local oscillator circuit can be applied to various frequency applications. On the other hand, the frequency output of the frequency synthesizer can be increased by 2 times by frequency doubling, so that when the output frequency of the frequency synthesizer is not high, the output frequency of the local oscillator circuit can be increased by doubling the frequency. After further amplification, it passes through a filter to filter out various clutters generated previously and obtain a clean local oscillator frequency.

[0028] Preferably, Figure 2 As shown, the frequency synthesizer includes a chip ADF4355, the first reference source input end of the frequency synthesizer corresponds to the REFINA end of the chip ADF4355, the first reference source input end includes a capacitor C3, a capacitor C4 and a capacitor C5 connected in series, and a resistor R7 is electrically connected between the capacitors C3 and C4 to ground, and the RC network composed of the resistor R7 and the capacitors C3 to C5 is a filter network, which can filter the input reference frequency signal. Preferably, the capacitance value of the capacitor C3 is 1nF, the capacitance value of the capacitor C4 is 1nF, the capacitance value of the capacitor C5 is 1nF, and the resistance value of the resistor R7 is 51Ω.

[0029] like Figure 2As shown, the digital control interface 132 of the frequency synthesizer 13 corresponds to the SPI interface of the chip ADF4355, and the SPI interface includes an enable terminal, a data terminal and a clock terminal. Among them, the enable terminal corresponds to the LE terminal of the chip, the data terminal corresponds to the DATA terminal of the chip, and the clock terminal corresponds to the CLK terminal of the chip. Similarly, the single-chip microcomputer corresponds to the chip ATTNY9, and the three pins of the chip, namely the CLK pin, the DATA pin and the LE pin, are respectively electrically connected to the CLK terminal, the DATA terminal and the LE terminal of the chip ADF4355, and are respectively connected in series with interface resistors R8, R9 and R10. Here, the chip selected for the frequency synthesizer is ADF4355, the output frequency of the chip ADF4355 is 54MHz-6800MHz, the reference input range is 10MHz-250MHz, the chip ADF4355 adopts an SPI control interface, the operating voltage is 3.3V, the supply voltage of the internal phase detector and voltage-controlled oscillator is 5V, the operating current is 180mA, a passive loop filter is used, the peripheral circuit is simple, and the use of this chip reduces the complexity of the entire local oscillator circuit.

[0030] Preferably, Figure 3 As shown, a loop filter is arranged between the CPOUT terminal and the VTUNE terminal of the chip ADF4355, and the loop filter correspondingly includes a first filter resistor R12 connected in series between the CPOUT terminal and the VTUNE terminal, and a first filter capacitor C19 and a second filter capacitor C20 are connected in parallel at the CPOUT terminal, the other end of the first filter capacitor C19 is grounded, the other end of the second filter capacitor C20 is connected in series with a second filter resistor R11, and the other end of the second filter resistor R11 is grounded, and a third filter capacitor C21 is connected in parallel to the VTUNE terminal, and the other end of the third filter capacitor C21 is grounded.

[0031] Further preferably, the resistance value of the second filter resistor R11 is 16KΩ, the resistance value of the first filter resistor R12 is 33KΩ, the capacitance value of the first filter capacitor C19 is 68pF, the capacitance value of the second filter capacitor C20 is 820pF, and the capacitance value of the third filter capacitor C21 is 18pF.

[0032] By setting a loop filter, a loop filter is established between the CPOUT and VTUNE terminals of the chip ADF4355. The function is to filter the phase-locked signal output from the CPOUT terminal and turn it into a control voltage signal for regulating the internal voltage-controlled oscillator of the chip ADF4355. The voltage of the internal voltage-controlled oscillator is controlled through the VTUNE terminal, so that the output frequency meets the requirements. Therefore, the chip ADF4355 integrates a voltage-controlled oscillator, so there is no need to use a separate voltage-controlled oscillator, which can reduce the components in the local oscillator circuit and reduce the space occupied.

[0033] As mentioned above, since the chip ADF4355 uses dual voltage power supply, including 3.3V and 5V power supply, it is necessary to transform the input 5V, which is mainly achieved by the chip LP5907. Figure 4 As shown, for the input 5V voltage, one branch is electrically connected to the VVCO terminal and VREGVCO terminal of the chip ADF4355 through the inductor L1. For the input 5V voltage, another branch is electrically connected to the VIN terminal and EN terminal of the chip LP5907 through the inductor L2. The VOUT terminal of the chip outputs 3.3V, one branch passes through the inductor L3 to supply power to the VRF terminal, AVDD terminal, DVDD terminal, PDBRF terminal, and CE terminal of the chip ADF4355, and the other branch supplies power to the 3.3V power supply terminal of the microcontroller chip ATTNY9 through the inductor L4.

[0034] Preferably, Figure 5 As shown, the frequency multiplier 14 includes a chip HMC369, and a matching attenuator is also provided between the RFOUTA+ terminal of the chip ADF4355 and the RFin terminal of the chip HMC369. The matching attenuator includes a capacitor C30, a capacitor C31 and a resistor R18 connected in series, wherein a resistor R19 is electrically connected between the capacitor C30 and the resistor R18 and grounded, wherein a resistor R20 is electrically connected between the resistor R18 and the capacitor C31 and grounded. The capacitor C30 is electrically connected to the RFOUTA+ terminal, and the capacitor C31 is electrically connected to the RFin terminal.

[0035] The chip HMC369 has an input frequency of 4.95GHz-6.35GHz, an output frequency of 9.9GHz-12.7GHz, an output power of up to 4dBm, a fundamental wave and third harmonic suppression of 30dBc, a +5V operating voltage, and a static operating current of 46mA. Further preferably, the capacitance value of the capacitor C30 is 1nF, and the capacitance value of the capacitor C31 is 30pF.

[0036] Further, such as Figure 6 As shown, Figure 6The circuit composition of the local oscillator amplifier is shown in FIG. It includes a chip CHA3666, wherein the RF input end (IN end in the figure) of the chip is electrically connected to the output end of the matching attenuation chip TGL4201 through a gold tape JD4, and the input end of the matching attenuation chip TGL4201 is connected to the output port 104 of the chip HMC369 through a gold tape JD5. The RF output end (OUT end in the figure) of the chip CHA3666 is connected to the first port 105 of the local oscillator filter, i.e., the input port of the local oscillator filter, through a gold tape JD6, and the port P1 of the chip CHA3666 is grounded through a gold wire JS3, and the port P2 of the chip CHA3666 is grounded through a gold wire JS4. The port D1 of the chip CHA3666 is electrically connected to the first capacitor DR1 through the gold wire JS5, and the first capacitor DR1 is electrically connected to the third capacitor DR3 through two gold wires JS6. Correspondingly, the port D2 of the chip CHA3666 is electrically connected to the second capacitor DR2 through the gold wire JS7, and the second capacitor DR2 is electrically connected to the third capacitor DR3 through two gold wires JS8. The third capacitor DR3 is electrically connected to the DC 4V power supply terminal 106 through two gold wires JS9.

[0037] Preferably, the diameter of the gold wire is 25um, and the width of the gold tape is 75um. Electrical connection through the gold wire and the gold tape in the RF circuit can improve the conductivity of the RF signal and reduce transmission loss. Although it will increase the cost, it is helpful to ensure the RF characteristics of the RF channel circuit.

[0038] It can be seen that Figure 6 The chip CHA3666 is used as the core of the gain amplifier. In addition to the chip, it also includes the above-mentioned chip capacitors. These capacitors occupy a smaller volume, so the volume of the entire gain amplifier is also smaller, which meets the needs of miniaturization. In addition, the chip CHA3666 is connected to these capacitors through gold wires and gold tapes, and the capacitors are also electrically connected through gold wires and gold tapes, which can enhance the RF conductivity of the electrical connection between the chip and these capacitors, and ensure the RF characteristics of the gain amplification. In addition, the operating frequency band of the amplifier chip CHA3666 is 6-17GHz, the gain is about 21dB at 14GHz, the output 1dB compression point power is about 17dBm, the input and output return loss is better than 15dB, the operating voltage is +4V to +4.5V, and the current is 60mA-100mA.

[0039] Furthermore, Figure 7It is a preferred embodiment of the local oscillator filter. The local oscillator filter is a microstrip filter, which can suppress the fundamental wave and the third harmonic component. In order to achieve the miniaturization and high suppression degree of the millimeter wave bandpass filter, the dielectric substrate adopts a 0.254mm ceramic substrate material. The microstrip filter includes 7 U-shaped microwave metal strips arranged on the ceramic substrate. The microwave metal strips are arranged in sequence and are centrally symmetrically distributed. The first microwave metal strip 161 opens upward and is located at the symmetry center. The second microwave metal strip 162 and the third microwave metal strip 163 are both opened downward and are respectively located at the first microwave metal strip. On the left and right sides of the belt 161, the fourth microwave metal belt 164 opens upward and is located on the left side of the second microwave metal belt 162, the fifth microwave metal belt 165 opens upward and is located on the right side of the third microwave metal belt 163, the sixth microwave metal belt 166 opens downward and is located on the left side of the fourth microwave metal belt 164, and the left branch of the sixth microwave metal belt 166 extends laterally to form a first port 168, the seventh microwave metal belt 167 opens downward and is located on the right side of the fifth microwave metal belt 165, and the right branch of the seventh microwave metal belt 167 extends laterally to form a second port 169.

[0040] Preferably, the width of the first microwave metal strip 161 is 0.19 mm, the lengths of the left branch and the right branch are the same, both 1.99 mm, the length of the lower connecting branch is 0.82 mm, and the intervals between the first microwave metal strip 161 and the second microwave metal strip 162 and the third microwave metal strip 163 are all 0.17 mm.

[0041] Further preferably, the second microwave metal strip 162 and the third microwave metal strip 163 have the same structure, wherein the left branch of the second microwave metal strip 162 and the left branch of the third microwave metal strip 163 are the same length (the upper and lower starting and ending positions of the length are the same as those of the first microwave metal strip, and are no longer marked in the figure, and other microwave metal strips hereinafter are similar thereto and will not be repeated), both of which are 1.99 mm, the right branch of the second microwave metal strip 162 and the right branch of the third microwave metal strip 163 are the same length, both of which are 1.99 mm, and the upper connecting branch of the second microwave metal strip 162 and the upper connecting branch of the third microwave metal strip 163 are the same length (the left and right starting and ending positions of the length are the same as those of the first microwave metal strip, and are no longer marked in the figure, and other microwave metal strips hereinafter are similar thereto and will not be repeated), both of which are 0.82 mm.

[0042] Preferably, the right branch of the second microwave metal strip 162 is flush with the left branch of the first microwave metal strip 161, that is, the upper edge of the left branch of the first microwave metal strip 161 is flush with the upper edge of the connecting branch corresponding to the upper end of the right branch of the second microwave metal strip 162, and the lower edge of the right branch of the second microwave metal strip 162 is flush with the lower edge of the connecting branch corresponding to the lower end of the left branch of the first microwave metal strip 161. Similarly, the left branch of the third microwave metal strip 163 is flush with the right branch of the first microwave metal strip 161.

[0043] The interval between the second microwave metal strip 162 and the fourth microwave metal strip 164 is 0.14 mm, and the interval between the third microwave metal strip 163 and the fifth microwave metal strip 165 is 0.14 mm.

[0044] Further preferably, the fourth microwave metal strip 164 and the fifth microwave metal strip 165 have the same structure, wherein the lengths of the left branch of the fourth microwave metal strip 164 and the left branch of the fifth microwave metal strip 165 are the same, both being 1.99 mm, the lengths of the right branch of the fourth microwave metal strip 164 and the right branch of the fifth microwave metal strip 165 are the same, both being 1.99 mm, and the lengths of the lower connecting branch of the fourth microwave metal strip 164 and the lower connecting branch of the fifth microwave metal strip 165 are the same, both being 0.82 mm.

[0045] The right branch of the fourth microwave metal strip 164 is flush with the left branch of the second microwave metal strip 162 , and the left branch of the fifth microwave metal strip 165 is flush with the right branch of the third microwave metal strip 163 .

[0046] The interval between the fourth microwave metal strip 164 and the sixth microwave metal strip 166 is 0.07 mm, and the interval between the fifth microwave metal strip 165 and the seventh microwave metal strip 167 is 0.07 mm.

[0047] Further preferably, the length of the right branch of the sixth microwave metal strip 166 is 1.95 mm, the width is 0.19 mm, the length of the left branch is 1.75 mm, the width is 0.24 mm, the upper end connecting branch is divided into two sections, wherein the length of the first connecting section on the left side is 0.5 mm, the width is 0.24 mm, the length of the second connecting section on the right side is 0.3 mm, the width is 0.19 mm. The length of the first port 168 is 0.97 mm, the width is 0.24 mm, and the distance from the upper edge of the first port 8 to the upper edge of the first connecting section of the upper end connecting branch is 0.91 mm.

[0048] Preferably, the sixth microwave metal strip 166 and the seventh microwave metal strip 167 have the same structure, and the two are symmetrical about the center of the microstrip. The length of the left branch of the seventh microwave metal strip 167 is 1.95mm, and the width is 0.19mm. The length of the right branch is 1.75mm, and the width is 0.24mm. The upper end connecting branch is divided into two sections, wherein the length of the first connecting section on the right is 0.5mm, and the width is 0.24mm, and the length of the second connecting section on the left is 0.3mm, and the width is 0.19mm. The first port 168 and the second port 169 have the same structure, and the two are symmetrically distributed about the center of the microstrip. The length of the second port 169 is 0.97mm, and the width is 0.24mm. The distance from the upper edge of the second port 169 to the upper edge of the first connecting section of the upper end connecting branch is 0.91mm. The distance between the first port 168 and the second port 169, that is, the length of the microstrip filter is 8.36mm.

[0049] Further preferably, the bandpass filtering range of the local oscillator microstrip filter is 12.5GHz-14.2GHz, the passband insertion loss is ≤3dB, the VSWR is ≤1.3, and the out-of-band suppression is: in the range of 6.4GHz-6.5GHz, the out-of-band suppression ratio is ≥55dBc, in the range of 19.2GHz-19.575GHz, the out-of-band suppression ratio is ≥55dBc.

[0050] It can be seen that since the frequency synthesizer chip ADF4355 can change and adjust the generated local oscillator frequency through the single-chip microcomputer, and in the channel of the entire local oscillator circuit, such as the input frequency of the frequency multiplier chip HMC369 is 4.95GHz-6.35GHz, the output frequency is 9.9GHz-12.7GHz, the working frequency band of the local oscillator power amplifier chip amplifier chip CHA3666 is 6-17GHz, and the bandpass filtering range of the microstrip filter is 12.5GHz-14.2GHz. Therefore, these local oscillator channel circuits can meet the frequency adjustment requirements of the frequency synthesizer chip ADF4355, and can provide corresponding frequency multiplication, amplification and filtering functions within its adjustment range, so that the local oscillator circuit can work within a frequency band to select the local oscillator frequency, rather than being limited to a fixed frequency, so it has good versatility.

[0051] Based on the above embodiments, the present invention discloses a local oscillator circuit for a miniaturized ODU transmission channel, characterized in that it includes a frequency synthesizer, a frequency multiplier, a local oscillator amplifier and a local oscillator filter connected in series in sequence, the first reference source input end of the frequency synthesizer is used to be electrically connected to an external reference source, the external reference source inputs a reference frequency signal to the frequency synthesizer through the first reference source input end, the digital control interface of the frequency synthesizer is electrically connected to a single-chip microcomputer, the single-chip microcomputer inputs a frequency control parameter to the frequency synthesizer through the digital control interface, the frequency multiplier performs a double frequency multiplication on the signal output by the frequency synthesizer to generate a local oscillator signal of the required frequency, and then the local oscillator amplifier performs power amplification on the local oscillator signal, and then the local oscillator filter suppresses and filters the fundamental wave and the third harmonic in the local oscillator signal. The local oscillator circuit is applied to the satellite communication transmission channel, and can change the required local oscillator signal frequency by parameter configuration, and has the advantages of stability, reliability, power saving, volume reduction, and cost reduction.

[0052] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A local oscillator circuit for a miniaturized ODU transmission channel, characterized in that: It comprises a frequency synthesizer, a frequency multiplier, a local oscillator amplifier and a local oscillator filter connected in series in sequence, wherein the first reference source input end of the frequency synthesizer is used to be electrically connected to an external reference source, the external reference source inputs a reference frequency signal to the frequency synthesizer through the first reference source input end, the digital control interface of the frequency synthesizer is correspondingly electrically connected to a single-chip microcomputer, the single-chip microcomputer inputs a frequency control parameter to the frequency synthesizer through the digital control interface, the frequency multiplier performs double frequency multiplication on the signal output by the frequency synthesizer to generate a local oscillator signal of a required frequency, the local oscillator amplifier performs power amplification on the local oscillator signal, and the local oscillator filter performs suppression filtering on the fundamental wave and the third harmonic in the local oscillator signal; The frequency synthesizer includes chip ADF4355, the single-chip microcomputer is chip ATTINY9, the local oscillator amplifier includes chip CHA3666, the frequency multiplier includes chip HMC369, the input frequency of chip HMC369 is 4.95GHz-6.35GHz, and the output frequency is 9.9GHz-12.7GHz; the bandpass filtering range of the local oscillator filter is 12.5GHz-14.2GHz, the passband insertion loss is ≤3dB, the VSWR is ≤1.3, and the out-of-band suppression is: in the range of 6.4GHz-6.5GHz, the out-of-band suppression ratio is ≥55dBc, and in the range of 19.2GHz-19.575GHz, the out-of-band suppression ratio is ≥55dBc; The local oscillator filter is a microstrip filter, which includes 7 U-shaped microwave metal strips arranged on a ceramic substrate, the ceramic substrate has a thickness of 0.254 mm, the microwave metal strips are arranged in sequence and are symmetrically distributed in the center, wherein the first microwave metal strip opens upward and is located at the symmetry center, the second microwave metal strip and the third microwave metal strip both open downward and are respectively located on the left and right sides of the first microwave metal strip, the fourth microwave metal strip opens upward and is located on the left side of the second microwave metal strip, the fifth microwave metal strip opens upward and is located on the right side of the third microwave metal strip, the sixth microwave metal strip opens downward and is located on the left side of the fourth microwave metal strip, the left branch of the sixth microwave metal strip extends laterally to form a first port, the seventh microwave metal strip opens downward and is located on the right side of the fifth microwave metal strip, the right branch of the seventh microwave metal strip extends laterally to form a second port, the first port and the second port have the same structure, and the two are symmetrically distributed about the center of the microstrip.

2. The local oscillator circuit for miniaturized ODU transmission channel according to claim 1, characterized in that: The first reference source input terminal of the frequency synthesizer corresponds to the REFINA terminal of the chip ADF4355, the digital control interface of the frequency synthesizer corresponds to the SPI interface of the chip ADF4355, and the SPI interface correspondingly includes an enable terminal, a data terminal and a clock terminal.

3. The local oscillator circuit for miniaturized ODU transmission channel according to claim 2, characterized in that: A loop filter is arranged between the CPOUT terminal and the VTUNE terminal of the chip ADF4355, and the loop filter correspondingly includes a first filter resistor connected in series between the CPOUT terminal and the VTUNE terminal, a first filter capacitor and a second filter capacitor are connected in parallel to the CPOUT terminal, the other end of the first filter capacitor is grounded, the other end of the second filter capacitor is connected in series with the second filter resistor, the other end of the second filter resistor is grounded, a third filter capacitor is connected in parallel to the VTUNE terminal, and the other end of the third filter capacitor is grounded.

4. The local oscillator circuit for miniaturized ODU transmission channel according to claim 3, characterized in that: The enable terminal, data terminal and clock terminal of the SPI interface of the chip ADF4355 correspond to the LE terminal, DATA terminal and CLK terminal, and the corresponding LE pin, DATA pin and CLK pin of the chip ATTINY9 are electrically connected respectively through serial interface resistors.

5. The local oscillator circuit for miniaturized ODU transmission channel according to claim 4, characterized in that: A matching attenuator is also provided between the RFOUTA+ terminal of the chip ADF4355 and the RFin terminal of the chip HMC369.

6. The local oscillator circuit for miniaturized ODU transmission channel according to claim 5, characterized in that: The RF input end of the chip CHA3666 is electrically connected to the output end of the matching attenuation chip TGL4201, the input end of the matching attenuation chip TGL4201 is connected to the output port of the chip HMC369 through a gold ribbon, and the RF output end of the chip CHA3666 is connected to the input end of the local oscillator filter through another gold ribbon.

7. The local oscillator circuit for miniaturized ODU transmission channel according to claim 6, characterized in that: The reference frequency signal input by the external reference source to the chip ADF4355 is a 10 MHz signal, the output frequency of the chip ADF4355 is 6.4 GHz, and the output frequency of the chip HMC369 is 12.8 GHz.

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