Broadband low-phase-noise and low-spurious-frequency synthesis circuit

Abstract

The invention discloses a broadband low-phase-noise and low-spurious frequency synthesis circuit which comprises a reference power division amplification unit, a comb spectrum frequency multiplication filtering unit and a phase-locked loop, and the output end of the reference power division amplification unit is connected with one input end of the phase-locked loop and the input end of the comb spectrum frequency multiplication filtering unit. The output end of the comb spectrum frequency multiplication filtering unit is connected with the other input end of the phase-locked loop, the output end of the phase-locked loop outputs a synthesized signal, a signal generated by cascade frequency multiplication of a two-stage comb spectrum generator is used as an interpolation radio frequency signal for frequency mixing in the phase-locked loop, the interpolation radio frequency signal is configured by the filter and the switch filter group, and the phase-locked loop is used for outputting a frequency-modulated signal. Broadband low-phase noise frequency synthesis is completed by combining a voltage-controlled oscillator, a functional circuit in the frequency synthesis circuit is arranged in a three-dimensional stacked self-shielding cavity structure, and a shielding cavity is used for placing devices in the functional circuit, so that the problem that output signals are easily interfered by comb spectrum frequency multiplication, filtering, frequency mixing and other circuits under the condition of small volume is solved, and stray level is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency synthesis, and in particular to a broadband low phase noise and low spurious frequency synthesis circuit. Background Art

[0002] As the signal source of various electronic information systems, frequency synthesizers are the core of modern electronic information systems. Their performance directly determines the performance of the system. With the rapid development of various electronic systems, various electronic systems have put forward comprehensive requirements for frequency synthesizers in terms of broadband, miniaturization, low spurious and low phase noise.

[0003] Frequency synthesis technologies in related technologies mainly include direct frequency synthesis, direct digital frequency synthesis and indirect frequency synthesis (also called phase-locked loop). The above three synthesis technologies all have their own advantages and disadvantages, and a single technology cannot meet the comprehensive requirements of the system for frequency synthesizers.

[0004] In view of the comprehensive requirements of broadband, miniaturization, low spurious and low phase noise frequency synthesizers, it is difficult to provide a good solution based on circuit solutions alone. Summary of the invention

[0005] In view of the above problems, the present application provides a broadband low phase noise, low spurious frequency synthesis circuit to at least solve the problem that some of the multiple comprehensive requirements of frequency synthesizers in the related art cannot be met.

[0006] In a first aspect, the present invention provides a broadband low phase noise, low spurious frequency synthesis circuit, characterized in that it comprises: a reference power division amplifier unit, a comb spectrum frequency multiplication filter unit and a phase-locked loop, wherein:

[0007] The output end of the reference power division amplifier unit is respectively connected to an input end of the phase-locked loop and an input end of the comb spectrum frequency multiplication filter unit;

[0008] The output end of the comb spectrum frequency multiplication filter unit is connected to another input end of the phase-locked loop, and the output end of the phase-locked loop outputs a synthetic signal;

[0009] The comb spectrum frequency multiplication filter unit uses the signal generated by the cascade multiplication of a two-stage comb spectrum generator as the interpolated RF signal for mixing within the phase-locked loop. The filter and switch filter group in the comb spectrum frequency multiplication filter unit configure the interpolated RF signal, and combine with the voltage-controlled oscillator in the phase-locked loop to complete broadband low phase noise frequency synthesis.

[0010] In one embodiment, the reference power division amplification unit comprises a first amplifier, a first power divider and a second amplifier connected in sequence, wherein:

[0011] The first amplifier amplifies the input reference signal to obtain a first reference signal, which is then passed through the first power divider to obtain a second reference signal, which are then output to the phase-locked loop and the second amplifier respectively;

[0012] The second amplifier is used to amplify the second reference signal to obtain a third reference signal and output the third reference signal to the input end of the comb spectrum frequency multiplication filter unit.

[0013] In one embodiment, the comb spectrum frequency doubling filter unit comprises a first comb spectrum generator, a filter, a third amplifier, a second comb spectrum generator and a switch filter group connected in sequence, wherein;

[0014] The first comb spectrum generator receives the third reference signal, performs comb spectrum frequency multiplication on the third reference signal to generate a fourth reference signal and outputs the fourth reference signal to the filter, and the filter performs filtering on the fourth reference signal to obtain a fifth reference signal and outputs the fifth reference signal to the third amplifier;

[0015] The third amplifier amplifies the fifth reference signal to obtain a sixth reference signal, and outputs it to the second comb spectrum generator for comb spectrum frequency doubling output processing to obtain a seventh reference signal. The switching filter group filters and extracts the seventh reference signal to obtain an eighth reference signal, and outputs it to another input end of the phase-locked loop.

[0016] In one embodiment, the phase-locked loop includes a phase detector, a loop filter, a voltage-controlled oscillator, a second power divider, a mixer and a low-pass filter connected in sequence in a ring shape, wherein:

[0017] After the ninth reference signal generated by the voltage-controlled oscillator is processed by the second power divider, one output terminal of the second power divider outputs a synthesized signal, another output terminal of the second power divider outputs the ninth reference signal to a local oscillator terminal of the mixer, and the RF terminal of the mixer inputs the eighth reference signal;

[0018] The mixer mixes the eighth reference signal and the ninth reference signal to output the tenth reference signal, which is then processed by the low-pass filter to obtain the eleventh reference signal;

[0019] The reference input terminal of the phase detector inputs the second reference signal output by the first power divider, the RF input terminal of the phase detector inputs the eleventh reference signal, and the phase detector compares the input second reference signal with the eleventh reference signal to obtain a twelfth reference signal;

[0020] The loop filter is used for controlling the voltage-controlled oscillator to output a required ninth reference signal according to the twelfth reference signal.

[0021] In one embodiment, the synthesized signal is calculated using a first calculation formula, wherein the first calculation formula is:

[0022]

[0023] In the formula, f ref is the second reference signal, R is the reference division ratio of the phase detector, N is the feedback signal division ratio of the phase detector, m and n are the two-stage comb spectrum multiplication coefficients of the filter and the first filter respectively, and m and n can be configured by the filter and the first filter.

[0024] In one embodiment, the switch filter bank comprises: a first switch, a first filters and a second switch, wherein a is a positive integer;

[0025] The input end of the first switch is connected to the second comb spectrum generator, the output end of the first switch is respectively connected to the input end of each of the first filters, the output end of each of the first filters is connected to the input end of the second switch, and the output end of the second switch is connected to another input end of the phase-locked loop.

[0026] In one embodiment, a broadband low phase noise, low spurious frequency synthesis circuit is applied to a shielding cavity structure, the shielding cavity structure comprising: an upper PCB board, a lower PCB board and solder balls, wherein:

[0027] The upper PCB board is connected to the lower PCB board through the solder ball stack, and the solder balls surround the upper PCB board and the lower PCB board to form a shielding ring, and the functional circuit of the broadband low phase noise and low spurious frequency synthesis circuit is arranged in the shielding ring;

[0028] The lower PCB board is provided with a ground hole, and the shielding ring, the bottom layer of the upper PCB board, the bottom layer of the lower PCB board and the ground hole form a shielding cavity, and the shielding cavity is used to place the devices in the functional circuit.

[0029] In one embodiment, a solder pad is provided on the surface layer of the lower PCB board, and the solder pad is provided in the shielding cavity. A connecting wire is provided between the solder pad and the functional circuit in the same shielding cavity. The solder pad is connected to the solder pads in different shielding cavities through the middle layer strip line of the shielding cavity structure, and the strip line surrounds the staggered ground holes.

[0030] In one embodiment, the first amplifier, the first power divider, the second amplifier, the first comb spectrum generator, the filter, the phase detector and the loop filter in the broadband low phase noise, low spurious frequency synthesis circuit are distributed on the upper PCB board; the third amplifier, the second comb spectrum generator, the switch filter group, the mixer, the low-pass filter, the voltage-controlled oscillator and the second power divider in the broadband low phase noise, low spurious frequency synthesis circuit are distributed on the lower PCB board.

[0031] In one embodiment, the shielding cavity includes a first shielding cavity, a second shielding cavity, a third shielding cavity and a fourth shielding cavity; the third-party amplifier and the second comb spectrum generator in the comb spectrum frequency doubling filter unit are arranged in the first shielding cavity, the switching filter group in the comb spectrum frequency doubling filter unit is arranged in the second shielding cavity, the mixer and the low-pass filter in the phase-locked loop are arranged in the third shielding cavity, and the voltage-controlled oscillator and the second power divider in the phase-locked loop are arranged in the four shielding cavities.

[0032] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0033] The invention provides a broadband low phase noise and low spurious frequency synthesis circuit, comprising: a reference power division amplifier unit, a comb spectrum frequency multiplication filter unit and a phase-locked loop, wherein: the output end of the reference power division amplifier unit is respectively connected to an input end of the phase-locked loop and an input end of the comb spectrum frequency multiplication filter unit, the output end of the comb spectrum frequency multiplication filter unit is connected to another input end of the phase-locked loop, and the output end of the phase-locked loop outputs a synthesis signal; the comb spectrum frequency multiplication filter unit uses a signal generated by cascading frequency multiplication of a two-stage comb spectrum generator as an interpolated radio frequency signal for mixing in the phase-locked loop to improve the frequency multiplication efficiency of a single signal; at the same time, the interpolated radio frequency signal is flexibly configured in combination with a filter and a switch filter group in the comb spectrum frequency multiplication filter unit; the broadband low phase noise frequency synthesis is completed in combination with a voltage-controlled oscillator in the phase-locked loop; by reasonably segmenting the output broadband signal and reasonably configuring the interpolated radio frequency signal, the feedback frequency in the phase-locked loop is always maintained at a relatively low frequency, thereby reducing the phase noise of the output frequency. A broadband low phase noise and low stray frequency synthesis circuit is applied in a shielding cavity structure, comprising: an upper PCB board, a lower PCB board and solder balls, wherein: the upper PCB board is connected to the lower PCB board through solder ball stacking, the solder balls surround the upper PCB board and the lower PCB board to form a shielding ring, and the functional circuit in the frequency synthesis circuit is arranged in the shielding ring; the lower PCB board is penetrated with a ground hole, and the shielding ring and the bottom layer of the upper PCB board, the bottom layer of the lower PCB board and the ground hole form a shielding cavity, and the shielding cavity is used to place devices in the functional circuit, which solves the problem that the output signal of the frequency synthesis circuit in a small volume is easily interfered by circuits such as comb spectrum frequency multiplication, filtering and mixing, and effectively reduces the stray level of the frequency synthesis circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The scope of the present disclosure may be better understood by reading the following detailed description of exemplary embodiments in conjunction with the accompanying drawings. The drawings included are:

[0035] Figure 1 A principle block diagram of a broadband low phase noise and low spurious frequency synthesis circuit provided by an embodiment of the present invention is shown;

[0036] Figure 2 A structural distribution diagram of a broadband low phase noise and low spurious frequency synthesis circuit provided by an embodiment of the present invention is shown;

[0037] Figure 3 A schematic cross-sectional view of a three-dimensional structure of a three-dimensional stacked self-shielding cavity structure provided by an embodiment of the present invention is shown;

[0038] Figure 4 A schematic diagram of the planar structure of a three-dimensional stacked self-shielding cavity structure provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present invention. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0040] In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0041] If similar descriptions of "first / second / third" appear in the application documents, the following description is added. In the following description, the terms "first / second / third" are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It is understandable that "first / second / third" can be interchanged in a specific order or sequence where permitted, so that the embodiments of the invention described herein can be implemented in an order other than that illustrated or described herein.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

[0043] Among the related technologies, the current mainstream frequency synthesis technologies mainly include direct frequency synthesis, direct digital frequency synthesis and indirect frequency synthesis (also called phase-locked loop). The above three synthesis technologies all have their own advantages and disadvantages, and a single technology cannot meet the system's comprehensive requirements for frequency synthesizers.

[0044] Therefore, it has become an inevitable trend to use a variety of synthesis methods to meet the comprehensive needs of frequency synthesizers. For example, the method of using a phase-locked loop plus direct frequency synthesis can achieve broadband and miniaturization, the method of using a phase-locked loop plus mixing can achieve broadband and low phase noise, and the method of using a phase-locked loop plus mixing plus direct digital frequency synthesis can achieve broadband, low phase noise, and small steps.

[0045] Based on the problems existing in the related art, the applicant comprehensively meets the comprehensive needs of broadband, miniaturized, low-spurious and low-phase noise frequency synthesizers by providing a frequency synthesis circuit and a shielded cavity structure (application environment) suitable for the functional circuits in the frequency synthesis circuit.

[0046] After integrating the above embodiments, the present invention can use a two-stage comb spectrum generator cascade as an interpolated RF signal for in-loop mixing to achieve efficient frequency doubling while combining filters and switches to achieve flexible configuration of the interpolated RF signal; the flexible configuration of the interpolated RF signal is combined with a broadband voltage-controlled oscillator (VCO) to achieve broadband frequency synthesis while reducing the feedback frequency in the phase-locked loop, thereby reducing the phase noise of the output frequency; the shielded cavity structure using a three-dimensional stacking process is miniaturized to solve the problem of signal crosstalk in the comb spectrum doubling, filtering and mixing circuits in a small volume, and effectively reduce the spurious of the frequency synthesis circuit.

[0047] See also Figure 1 , Figure 1 A circuit principle block diagram of a broadband low phase noise, low spurious frequency synthesis circuit provided in an embodiment, a broadband low phase noise, low spurious frequency synthesis circuit, comprising: a reference power division amplifier unit, a comb spectrum frequency multiplication filter unit and a phase-locked loop, wherein:

[0048] The output end of the reference power division amplifier unit is respectively connected to an input end of a phase-locked loop and an input end of a comb spectrum frequency multiplication filter unit;

[0049] The output end of the comb spectrum frequency multiplication filter unit is connected to another input end of the phase-locked loop, and the output end of the phase-locked loop outputs a synthetic signal;

[0050] The comb spectrum frequency doubling filter unit uses the signal generated by the cascaded frequency doubling of a two-stage comb spectrum generator as the interpolated RF signal for mixing in the phase-locked loop. The filter and switch filter group in the comb spectrum frequency doubling filter unit configure the interpolated RF signal and complete the broadband low phase noise frequency synthesis in combination with the voltage-controlled oscillator in the phase-locked loop.

[0051] In this embodiment, the comb spectrum frequency doubling filter unit uses the signal generated by the cascaded frequency doubling of a two-stage comb spectrum generator as the interpolated RF signal for the in-loop mixing, thereby improving the frequency doubling efficiency of a single signal and combining filters and switches to realize flexible configuration of the interpolated RF signal in the in-loop mixing; it combines with a broadband voltage-controlled oscillator (VCO) to realize broadband frequency synthesis, and by reasonably segmenting the output broadband signal and reasonably configuring the interpolated RF signal, the feedback frequency in the phase-locked loop is always maintained at a relatively low frequency, thereby reducing the phase noise of the output frequency.

[0052] In some embodiments, the reference power division amplification unit includes a first amplifier, a first power divider, and a second amplifier connected in sequence, wherein:

[0053] The first amplifier amplifies the input reference signal to obtain a first reference signal, which is then passed through a first power divider to obtain a second reference signal, which are then output to a phase-locked loop and a second amplifier respectively;

[0054] The second amplifier is used to amplify the second reference signal to obtain a third reference signal and output the third reference signal to the input end of the comb spectrum frequency doubling filter unit.

[0055] In this embodiment, a low phase noise reference signal enters the first amplifier, and the first amplifier amplifies it with low additional phase noise; the first power divider is cascaded with the first amplifier to split the reference signal into two paths, one of which is output to the phase-locked loop as a reference signal for the phase detector, and the other is output to the second amplifier; the second amplifier amplifies the reference signal with low additional phase noise to ensure that the signal power can excite the first comb spectrum generator in the subsequent stage, and the amplified reference signal is output to the comb spectrum multiplication filter unit.

[0056] In some embodiments, the comb spectrum frequency doubling filter unit comprises a first comb spectrum generator, a filter, a third amplifier, a second comb spectrum generator and a switch filter group connected in sequence, wherein:

[0057] The first comb spectrum generator receives the third reference signal, performs comb spectrum frequency multiplication on the third reference signal to generate a fourth reference signal and outputs it to the filter, and the filter filters the fourth reference signal to obtain a fifth reference signal and outputs it to the third amplifier;

[0058] The third amplifier amplifies the fifth reference signal to obtain a sixth reference signal, and outputs it to the second comb spectrum generator for comb spectrum frequency doubling output processing to obtain a seventh reference signal. The switching filter group filters and extracts the seventh reference signal to obtain an eighth reference signal, and outputs it to another input end of the phase-locked loop.

[0059] In this embodiment, the input end of the comb spectrum frequency multiplication filter unit is connected to the reference power division amplifier unit, and the output end is connected to the phase-locked loop. The first comb generator performs comb spectrum frequency multiplication output on the reference signal from the reference power division amplifier unit, generates multiple harmonics of the reference signal and outputs them to the filter. The filter filters out multiple harmonics except the mth harmonic to obtain a signal mf ref And output to the third amplifier; the third amplifier mf ref The signal is amplified to ensure that the signal power output to the second comb spectrum generator can excite the second comb spectrum generator;

[0060] The second comb spectrum generator is used for mf ref The signal is comb spectrum multiplied and output to generate mf ref The multiple harmonics of the signal are output to the switched filter bank.

[0061] In some embodiments, the switch filter bank comprises: a first switch, a first filters, and a second switch, where a is a positive integer;

[0062] The input end of the first switch is connected to the second comb spectrum generator, the output end of the first switch is respectively connected to the input end of each first filter, the output end of each first filter is connected to the input end of the second switch, and the output end of the second switch is connected to another input end of the phase-locked loop.

[0063] In this embodiment, the branch ends of the first switch are respectively connected to one end of the first filter to the first filter a, and the other end of the first filter to the filter a is respectively connected to the branch ends of the second switch, thereby forming a switch filter group. The switch filter group is connected to mf ref The multiple harmonics of the signal are filtered and extracted, and the a point frequencies obtained by filtering are output to the mixer as the RF signal of the mixer in the phase-locked loop.

[0064] In some embodiments, the phase-locked loop includes a phase detector, a loop filter, a voltage-controlled oscillator, a second power divider, a mixer, and a low-pass filter connected in sequence in a ring, wherein:

[0065] After the ninth reference signal generated by the voltage-controlled oscillator is processed by the second power divider, one output terminal of the second power divider outputs a synthesized signal, another output terminal of the second power divider outputs the ninth reference signal to the local oscillator input terminal of the mixer, and the RF input terminal of the mixer inputs the eighth reference signal;

[0066] The mixer mixes the eighth reference signal and the ninth reference signal to output a tenth reference signal to a low-pass filter for processing to obtain an eleventh reference signal;

[0067] The reference input terminal of the phase detector inputs the second reference signal output by the first power divider, the RF input terminal of the phase detector inputs the eleventh reference signal, and the phase detector compares the input second reference signal with the eleventh reference signal to obtain a twelfth reference signal;

[0068] The loop filter is used for controlling the voltage controlled oscillator to output a required ninth reference signal according to the twelfth reference signal.

[0069] In this embodiment, the two input ends of the phase-locked loop are respectively connected to the reference power divider amplifier unit and the comb spectrum frequency multiplication filter unit, and the output end is the output of the frequency synthesis circuit. The signal generated by the voltage-controlled oscillator is divided by the second power divider, one way is output to the outside, and the other way is output to the mixer as the local oscillator signal; the output end of the mixer is connected to a low-pass filter, and the output intermediate frequency signal f IF (f IF =f LO -f RF ) passes through a low-pass filter and is then combined with the reference signal f in the phase detector. ref Real-time comparison; the error information output by the phase detector passes through the loop filter to control the voltage-controlled oscillator to lock the output frequency f vco .

[0070] In some embodiments, the synthesized signal is calculated using a first calculation formula, wherein the first calculation formula is:

[0071]

[0072] In the formula, f ref is the second reference signal, R is the reference division ratio of the phase detector, N is the feedback signal division ratio of the phase detector, m and n are the two-stage comb spectrum multiplication coefficients of the filter and the first filter respectively, and m and n can be flexibly configured through the filter and the first filter.

[0073] In this embodiment, the broadband low phase noise synthesis circuit has the following characteristics: output signal; f ref External reference signal, R is the reference division ratio of the phase detector (usually 1), and N is the feedback signal division ratio of the phase detector.

[0074] Among them, the two-stage comb spectrum multiplication coefficients m and n can be flexibly configured through filters, first filters 1 to first filters a, and combined with broadband VCO to achieve broadband frequency synthesis, while reducing the feedback frequency, thereby reducing the phase noise of the output frequency of the synthesis circuit.

[0075] In one embodiment, the VCO is a broadband VCO, which can realize broadband frequency synthesis. During the synthesis process, the broadband VCO signal is divided into a segment of narrowband signals, each of which has a bandwidth of mf ref , na mf ref is a point frequency and a segment f LO One-to-one correspondence, choose n value as f LO For mf ref We can round off to make f IF (f IF =f LO -nmf ref ) is always less than or equal to mf ref .

[0076] Considering that in order to improve the phase noise, integer phase detection is preferred for the phase detector, and the frequency output step is f ref ;

[0077] Considering the small step size and acceptable phase noise degradation, fractional phase detection can be used, and the mixing frequency has the following characteristics: f IF =f LO -f RF , f LO >f RF ; Interpolated RF signal f RF The phase noise is better than the phase noise of the phase detector feedback signal; the maximum center signal frequency f IFmax It cannot be too high, otherwise the purpose of optimizing phase noise will be lost. LO Usually it is a broadband signal, which needs to be divided into a segment of narrowband signal, f RF is a point frequency and a segment f LO One-to-one correspondence; the low-pass filter band should cover the intermediate frequency signal f IF Maximum value of (including circuit unlocked state).

[0078] Preferably, the first amplifier and the second amplifier are amplifiers with low added phase noise.

[0079] The broadband low phase noise and low spurious frequency synthesis circuit provided in the above embodiment is applicable to Figure 3 and Figure 4 , Figure 3 A schematic cross-sectional view of a three-dimensional stacked self-shielding cavity structure provided in an embodiment of the present application. Figure 4 A schematic diagram of the planar structure of a three-dimensional stacked self-shielding cavity structure provided in an embodiment of the present application is shown.

[0080] Figure 3 In the present invention, the shielding cavity structure may include a three-dimensional stacked self-shielding cavity structure, including: an upper PCB board, a lower PCB board and solder balls, wherein:

[0081] The upper PCB board is connected to the lower PCB board through solder ball stacking, and the solder balls surround the upper PCB board and the lower PCB board to form a shielding circle, and the functional circuit of the broadband low phase noise and low spurious frequency synthesis circuit is arranged in the shielding circle;

[0082] The lower PCB board is provided with a ground hole, and the shielding ring and the bottom layer of the upper PCB board, the bottom layer of the lower PCB board and the ground hole form a shielding cavity, and the shielding cavity is used to place devices in the functional circuit.

[0083] In this embodiment, the upper PCB is stacked on the lower PCB through solder balls, and the solder balls surround certain functional circuits in the composite circuit to form a shielding ring. The bottom layer of the upper PCB and the bottom layer of the lower PCB are preferably provided with copper foil. The shielding ring and the bottom layer copper foil of the upper PCB, the bottom layer copper foil of the lower PCB, and the ground hole of the lower PCB form a shielding cavity in a three-dimensional space.

[0084] In some embodiments, the first amplifier, the first power divider, the second amplifier, the first comb spectrum generator, the filter, the phase detector and the loop filter in the broadband low phase noise, low spurious frequency frequency synthesis circuit are distributed on the upper PCB board; the third amplifier, the second comb spectrum generator, the switching filter group, the mixer, the low-pass filter, the voltage-controlled oscillator and the second power divider in the broadband low phase noise, low spurious frequency frequency synthesis circuit are distributed on the lower PCB board.

[0085] Among them, the functional circuits in the broadband low phase noise, low spurious frequency synthesis circuit include: having the characteristics of easily interfering with other circuits or being easily interfered by other circuits, such as the functional circuit composed of the first comb spectrum generator, the filter, and the third amplifier, the circuit composed of the second comb spectrum generator and the switching filter group, the mixer circuit, etc.

[0086] In some embodiments, a solder pad is disposed on the surface of the lower PCB board, and the solder pad is disposed in a shielding cavity. A connecting wire is provided between the solder pad and the functional circuit in the same shielding cavity. The solder pad is connected to the solder pads in different shielding cavities through an intermediate layer strip line of the shielding cavity structure.

[0087] In the embodiment of the present application, Figure 3 and Figure 4 In each shielding cavity (such as Figure 4 The RF signal transmission between the middle shielding cavity 1 and the shielding cavity 2) is transmitted to the middle layer through the surface pad of the lower PCB through the via hole, and then transmitted to the middle layer of the target shielding cavity by the strip line of the middle layer, and then transmitted from the middle layer of the target shield to the surface layer through the via hole to the target shielding cavity.

[0088] In some embodiments, see Figure 2 , Figure 2This is a structural distribution diagram of a broadband low phase noise, low spurious frequency synthesis circuit provided in an embodiment of the present application, refer to Figure 2 and Figure 4 In the invention, the shielding cavity comprises a first shielding cavity (shielded cavity 1), a second shielding cavity (shielded cavity 2), a third shielding cavity (shielded cavity 3) and a fourth shielding cavity (shielded cavity 4); a third-party amplifier and a second comb spectrum generator in a comb spectrum frequency doubling filter unit are arranged in the first shielding cavity (shielded cavity 1), a switching filter group in the comb spectrum frequency doubling filter unit is arranged in the second shielding cavity (shielded cavity 2), a mixer and a low-pass filter in a phase-locked loop are arranged in the third shielding cavity (shielded cavity 3), and a voltage-controlled oscillator and a second power divider in the phase-locked loop are arranged in the fourth shielding cavity (shielded cavity 4).

[0089] In some embodiments, the stripline is surrounded by staggered ground vias.

[0090] In this embodiment, Figure 3 As shown in FIG. 1 , the shielding ring is composed of two interlaced layers of solder balls, wherein the solder ball spacing is as small as possible while ensuring that there is no short circuit between the solder balls after soldering. Figure 4 As shown, the stripline has two circles of ground holes that are staggered around it.

[0091] In some embodiments, the connecting wire is a gold wire.

[0092] In this embodiment, the chip in the functional circuit can be connected by gold wire, and then connected to other functional circuits in other shielding cavities through pads and strip lines.

[0093] In the three-dimensional stacked self-shielding cavity structure of this embodiment, the miniaturization of the frequency synthesis circuit is achieved by adopting a three-dimensional stacking process, which solves the problem of signal crosstalk in the comb spectrum multiplication, filtering and mixing circuits in a small volume, and effectively reduces the spurious of the frequency synthesis circuit.

[0094] The present application adopts a broadband low phase noise, low spurious frequency synthesis circuit and a shielded cavity structure to realize a broadband miniaturized low spurious and low phase noise frequency synthesizer with an output frequency covering the Ku band in a volume of 22.5mm*15mm*3.5mm. The phase noise of the frequency synthesizer at the Ku band frequency is better than -110dBc / Hz@1kHz, and the spurious suppression is better than 60dBc, achieving good results.

[0095] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

[0096] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A broadband low phase noise, low spurious frequency synthesis circuit, characterized in that: include: Reference power division amplifier unit, comb spectrum frequency multiplication filter unit and phase-locked loop, wherein: The output end of the reference power division amplifier unit is respectively connected to an input end of the phase-locked loop and an input end of the comb spectrum frequency multiplication filter unit; The output end of the comb spectrum frequency multiplication filter unit is connected to another input end of the phase-locked loop, and the output end of the phase-locked loop outputs a synthetic signal; The comb spectrum frequency multiplication filter unit uses the signal generated by the cascade multiplication of a two-stage comb spectrum generator as the interpolated RF signal for mixing within the phase-locked loop. The filter and switch filter group in the comb spectrum frequency multiplication filter unit configure the interpolated RF signal, and combine with the voltage-controlled oscillator in the phase-locked loop to complete broadband low phase noise frequency synthesis.

2. A broadband low phase noise, low spurious frequency synthesis circuit according to claim 1, characterized in that: The reference power division amplification unit comprises a first amplifier, a first power divider and a second amplifier connected in sequence, wherein: The first amplifier amplifies the input reference signal to obtain a first reference signal, which is then passed through the first power divider to obtain a second reference signal, which are then output to the phase-locked loop and the second amplifier respectively; The second amplifier is used to amplify the second reference signal to obtain a third reference signal and output the third reference signal to the input end of the comb spectrum frequency multiplication filter unit.

3. A broadband low phase noise, low spurious frequency synthesis circuit according to claim 2, characterized in that: The comb spectrum frequency doubling filter unit comprises a first comb spectrum generator, a filter, a third amplifier, a second comb spectrum generator and a switch filter group connected in sequence, wherein: The first comb spectrum generator receives the third reference signal, performs comb spectrum frequency multiplication on the third reference signal to generate a fourth reference signal and outputs the fourth reference signal to the filter, and the filter performs filtering on the fourth reference signal to obtain a fifth reference signal and outputs the fifth reference signal to the third amplifier; The third amplifier amplifies the fifth reference signal to obtain a sixth reference signal, and outputs it to the second comb spectrum generator for comb spectrum frequency doubling output processing to obtain a seventh reference signal. The switching filter group filters and extracts the seventh reference signal to obtain an eighth reference signal, and outputs it to another input end of the phase-locked loop.

4. A broadband low phase noise, low spurious frequency synthesis circuit according to claim 3, characterized in that: The phase-locked loop comprises a phase detector, a loop filter, a voltage-controlled oscillator, a second power divider, a mixer and a low-pass filter which are connected in sequence in a ring shape, wherein: After the ninth reference signal generated by the voltage-controlled oscillator is processed by the second power divider, one output end of the second power divider outputs a synthesized signal, another output end of the second power divider outputs the ninth reference signal to the local oscillator input end of the mixer, and the RF input end of the mixer inputs the eighth reference signal; The mixer mixes the eighth reference signal and the ninth reference signal to output a tenth reference signal to the low-pass filter for processing to obtain an eleventh reference signal; The reference input terminal of the phase detector inputs the second reference signal output by the first power divider, the RF input terminal of the phase detector inputs the eleventh reference signal, and the phase detector compares the input second reference signal with the eleventh reference signal to obtain a twelfth reference signal; The loop filter is used for controlling the voltage-controlled oscillator to output a required ninth reference signal according to the twelfth reference signal.

5. A broadband low phase noise, low spurious frequency synthesis circuit according to any one of claims 1 to 4, characterized in that: The synthesized signal is calculated using a first calculation formula, wherein the first calculation formula is: In the formula, f ref is the second reference signal, R is the reference frequency division ratio of the phase detector, N is the feedback signal frequency division ratio of the phase detector, m and n are the two-stage comb spectrum multiplication coefficients respectively, and m and n can be configured by the filter and the first filter.

6. A broadband low phase noise, low spurious frequency synthesis circuit according to claim 1, characterized in that: The switch filter bank comprises: a first switch, a first filters and a second switch, wherein a is a positive integer; The input end of the first switch is connected to the second comb spectrum generator, the output end of the first switch is respectively connected to the input end of each of the first filters, the output end of each of the first filters is connected to the input end of the second switch, and the output end of the second switch is connected to another input end of the phase-locked loop.

7. A broadband low phase noise, low spurious frequency synthesis circuit according to any one of claims 1 to 6, characterized in that: Applied to a shielding cavity structure, the shielding cavity structure includes: an upper PCB board, a lower PCB board and solder balls, wherein: The upper PCB board is connected to the lower PCB board through the solder ball stack, and the solder balls surround the upper PCB board and the lower PCB board to form a shielding ring, and the functional circuit of the broadband low phase noise and low spurious frequency synthesis circuit is arranged in the shielding ring; The lower PCB board is provided with a ground hole, and the shielding ring, the bottom layer of the upper PCB board, the bottom layer of the lower PCB board and the ground hole form a shielding cavity, and the shielding cavity is used to place the devices in the functional circuit.

8. A broadband low phase noise, low spurious frequency synthesis circuit according to claim 7, characterized in that: The surface layer of the lower PCB board is provided with a soldering pad, and the soldering pad is arranged in the shielding cavity. A connecting wire is provided between the soldering pad and the functional circuit in the same shielding cavity. The soldering pad is connected to the soldering pads in different shielding cavities through the middle layer strip line of the shielding cavity structure, and the strip line surrounds the staggered ground holes.

9. A broadband low phase noise, low spurious frequency synthesis circuit according to claim 7, characterized in that: The first amplifier, the first power divider, the second amplifier, the first comb spectrum generator, the filter, the phase detector and the loop filter in the broadband low phase noise and low spurious frequency synthesis circuit are distributed on the upper PCB board; the third amplifier, the second comb spectrum generator, the switch filter group, the mixer, the low-pass filter, the voltage-controlled oscillator and the second power divider in the broadband low phase noise and low spurious frequency synthesis circuit are distributed on the lower PCB board.

10. A broadband low phase noise, low spurious frequency synthesis circuit according to claim 7, characterized in that: The shielding cavity includes a first shielding cavity, a second shielding cavity, a third shielding cavity and a fourth shielding cavity; the third-party amplifier and the second comb spectrum generator in the comb spectrum frequency doubling filter unit are arranged in the first shielding cavity, the switching filter group in the comb spectrum frequency doubling filter unit is arranged in the second shielding cavity, the mixer and the low-pass filter in the phase-locked loop are arranged in the third shielding cavity, and the voltage-controlled oscillator and the second power divider in the phase-locked loop are arranged in the four shielding cavities.

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