Broadband low-phase noise fine-step frequency combining system

Abstract

The utility model relates to a broadband low-phase noise fine-step frequency combining system, which comprises a crystal oscillator, a first power divider, a controller, a low-noise fine-step source unit and a broadband spread spectrum source unit, and is characterized in that the output end of the crystal oscillator is connected with the output end of the first power divider; two output ends of the first power divider are respectively connected with the low-noise fine inlet source unit and the broadband spread spectrum source unit; the low-noise fine stepping source unit outputs an FDDS signal and a local oscillator signal under the setting of the controller, the FDDS signal and the local oscillator signal are mixed by a first mixer to obtain a low-noise fine stepping signal, and the low-noise fine stepping signal is input to the broadband spread spectrum source unit; the broadband spread spectrum source unit expands the output frequency range through the frequency synthesizer and the second comb spectrum generator. According to the utility model, the advantages of the comb spectrum generator, the frequency synthesizer and the DDS are ingeniously combined, so that the broadband low-phase-noise fine-step frequency synthesizer is realized, and the size and the power consumption are reduced at the same time.

Description

Technical Field

[0001] The utility model relates to the technical field of radio frequency and microwave, and particularly relates to a narrow-width and low-phase-noise fine-step frequency synthesizer system. Background Art

[0002] The frequency synthesizer is one of the key components of microwave radio frequency frequency conversion modules and is widely used in radar, signal interception, wireless monitoring, and communication systems. In recent years, with the deterioration of the electromagnetic environment, the requirements for the sensitivity and resolution of receivers have become higher and higher, and the frequency synthesizer has a direct impact on this index. Therefore, modern communication also puts forward higher requirements for the performance of the frequency synthesizer, such as phase noise, frequency step, etc. At present, broadband frequency synthesizers mainly rely on mixing or frequency multiplication to expand the bandwidth. This method usually requires a large number of filters, resulting in a large volume and high power consumption. The realization of conventional fine steps mainly relies on DDS. However, due to device limitations, DDS usually has a low output frequency and a narrow bandwidth. Low-phase-noise frequency sources usually adopt analog direct synthesis methods such as comb spectrum generators, PDROs, etc., which usually cannot perform fine steps. To perform fine steps, DDS needs to be combined. The conventional implementation of a broadband fine-step frequency synthesizer results in a large volume and high power consumption. Content of the Utility Model

[0003] The purpose of the utility model is to overcome the shortcomings of the prior art and provide a broadband and low-phase-noise fine-step frequency synthesizer system, which solves the deficiencies existing in the prior art.

[0004] The purpose of the utility model is realized through the following technical solutions: a broadband and low-phase-noise fine-step frequency synthesizer system, the system includes a crystal oscillator, a first power splitter, a controller, a low-noise fine-step source unit, and a broadband frequency spreading source unit. The output end of the crystal oscillator is connected to the output end of the first power splitter, and the two output ends of the first power splitter are respectively connected to the low-noise fine-step source unit and the broadband frequency spreading source unit;

[0005] The low-noise fine-step source unit outputs an FDDS signal and a local oscillator signal under the setting of the controller. After being mixed by a first mixer, a low-noise fine-step signal is obtained and input into the broadband frequency spreading source unit; the broadband frequency spreading source unit realizes the expansion of the output frequency range through a frequency synthesizer and a second comb spectrum generator.

[0006] The low-noise fine-step source unit includes a first comb spectrum generator, a second power splitter, a DDS, a first band-pass filter, and a first mixer;

[0007] The output end of the first comb spectrum generator is connected to the input end of the second power splitter. The two output ends of the second power splitter are respectively connected to the input ends of the first mixer and the DDS. The output end of the DDS is connected to the input end of the first band-pass filter, and the output end of the first band-pass filter is connected to the input end of the first mixer.

[0008] The broadband spread-spectrum source unit includes a narrowband amplifier, a second band-pass filter, a third power divider, a second comb spectrum generator, a second mixer, a broadband amplifier, a radio frequency switch, a frequency synthesizer, and a loop filter;

[0009] The narrowband amplifier, the second band-pass filter, and the third power divider are connected in sequence. The two output terminals of the third power divider are respectively connected to the input terminals of the second comb spectrum generator and the broadband amplifier. The output terminal of the second comb spectrum generator is connected to the input terminal of the second mixer. The output terminal of the second mixer is connected to the radio frequency switch. The radio frequency switch is connected to the frequency synthesizer. The output terminal of the frequency synthesizer is connected to the input terminal of the second mixer. The output terminal of the broadband amplifier is connected to the frequency synthesizer, and the loop filter is connected to the frequency synthesizer.

[0010] The radio frequency switch is connected to the REFin port of the frequency synthesizer. The RFOUTB port of the frequency synthesizer is connected to the second mixer. The output terminal of the broadband amplifier is connected to the RFDin port of the frequency synthesizer. The CP port of the frequency synthesizer is connected to the VT port through the loop filter.

[0011] One of the output terminals of the first power divider is connected to the radio frequency switch. The output terminal of the first mixer is connected to the input terminal of the narrowband amplifier.

[0012] The present utility model has the following advantages: A broadband low-phase-noise fine-step frequency synthesizer system combines the advantages of a comb spectrum generator, a frequency synthesizer, and a DDS to achieve a broadband low-phase-noise fine-step frequency synthesizer, while reducing the volume and power consumption. It does not require a large number of band-pass filters, makes full use of the filtering characteristics of the frequency synthesizer itself to control spurs, and combines the excellent noise performance of the comb spectrum generator, so that the present invention has better performance, lower cost, and higher reliability compared with traditional methods, and can further reduce the size of the device. Therefore, it has the advantage of small size. Since the present invention reduces the multiplication factor of the traditional PLL by mixing the output frequencies of the comb spectrum generator and the frequency synthesizer, it has very low phase noise. It changes the traditional method of presetting the ADC voltage or presetting the frequency of the sub-loop to reading and storing the working frequency point parameters of the frequency synthesizer itself. When working normally, the controller simultaneously sets the pre-stored parameter values of the frequency and the new register values, so as to achieve the output of a low-phase-noise signal. It adopts a two-stage mixed insertion loop phase-locked method to achieve a broadband low-phase-noise fine-step signal, and innovatively utilizes the multi-port frequency output characteristics of the frequency synthesizer to reduce the traditional phase-locked loop output signal coupling and amplification circuit, reducing the system size and power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic structural diagram of the present utility model;

[0014] In the figure: 1 - crystal oscillator, 2 - first power splitter, 3 - first comb spectrum generator, 4 - second power splitter, 5 - DDS (Direct Digital Synthesizer), 6 - first band-pass filter, 7 - first mixer, 8 - narrow-band amplifier, 9 - second band-pass filter, 10 - third power splitter, 11 - second comb spectrum generator, 12 - second mixer, 13 - wide-band amplifier, 14 - RF switch, 15 - frequency synthesizer, 16 - loop filter, 17 - controller, 18 - CP port, 19 - RFDin port, 20 - RFOUTB port, 21 - REFin port, 22 - RFOUTA port, 23 - VT port. Detailed implementation manners

[0015] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part rather than all of the embodiments of the present application. Components of the embodiments of the present application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application provided below with reference to the accompanying drawings is not intended to limit the protection scope of the claimed present application, but merely represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts fall within the protection scope of the present application. The following further describes the present invention with reference to the accompanying drawings.

[0016] As Figure 1 shown, the present invention specifically relates to a wide-band low-phase-noise fine-step frequency synthesizer system, which includes a crystal oscillator 1, a first power splitter 2, a first comb spectrum generator 3, a second power splitter 4, a DDS (Direct Digital Synthesizer) 5, a first band-pass filter 6, a first mixer 7, a narrow-band amplifier 8, a second band-pass filter 9, a third power splitter 10, a second comb spectrum generator 11, a second mixer 12, a wide-band amplifier 13, an RF switch 14, a frequency synthesizer 15, a loop filter 16, and a controller 17, wherein the controller 17 can be an FPGA or other logic control devices.

[0017] Among them, in the process of reading and storing the preset parameter of the operating frequency of the frequency synthesizer 15, when the system is powered on and initialized, the controller 17 sets the RF switch 14 to switch to the output port of the first power splitter 2, and at the same time sequentially sets all the operating frequencies of the frequency synthesizer 15 to output, and reads and stores the parameter information corresponding to the operating frequency points through the controller 17.

[0018] Low-noise and fine-stepping source solution: The first comb spectrum generator 3 generates an output signal NF0 under the excitation of the reference F0 output by the crystal oscillator 1. This signal is divided into two signals by the second power splitter 4. One signal is input to the DDS 5 as its reference clock signal, and outputs the FDDS signal under the setting of the controller 17. The other signal is input to the first mixer 7 as its local oscillator signal, and is mixed with the FDDS signal to obtain a low-noise and fine-stepping signal.

[0019] Wideband spread-spectrum source solution: The low-noise and fine-stepping signal output by the first mixer 7 passes through the narrowband amplifier 8 and the second band-pass filter 9 and then enters the third power splitter 10, which is divided into two signals. One signal enters the RFDin port 19 of the frequency synthesizer 15 after being amplified by the wideband amplifier 13 as its loop phase discrimination signal. The other signal enters the second comb spectrum generator 11, which generates a series of output signals MFin (M = 3, 4, 5, 6, 7...) under excitation as the radio frequency signal of the third mixer 12. It is down-converted with the local oscillator signal at the RFOUTB port 20 of the frequency synthesizer 15 to obtain an intermediate frequency signal FIF = Fout - MFin. This signal enters the REFin port 21 of the frequency synthesizer 15 through the radio frequency switch 14 as its reference clock signal, and is phase discriminated with the feedback phase discrimination signal input at the RFDin port 19. A DC voltage is generated by the CP port 18 of the frequency synthesizer 15. This voltage filters out high-frequency components through the loop filter 16 to obtain the VCO frequency voltage control voltage, which is input to the VT port 23 of the frequency synthesizer 15, thereby tuning the output frequency signal. Finally, it is output through the RFOUTA port 22 of the frequency synthesizer 15. By selecting different M values (M = 3, 4, 5, 6, 7...) of the second comb spectrum generator 11, the output frequency range is expanded.

[0020] The present invention realizes the generation of the frequency signal by setting the output frequency of the DDS 5, selecting different M values of the second comb spectrum generator 11, setting the REFin parameter value R of the frequency synthesizer 15, and the RFDin parameter value N. When the entire system is locked, the output frequency is F out =(M - R / N)(nF0 - FDDS). Where (n: the multiplication factor of the reference clock F0; FDDS: the output frequency of the DDS ⑤; M: the multiplication factor of the second comb spectrum generator 11; R: the REFin parameter value of the frequency synthesizer 15; N: the RFDin parameter value of the frequency synthesizer 15).

[0021] The above are only the preferred embodiments of the present utility model. It should be understood that the present utility model is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments. Instead, it can be used in various other combinations, modifications, and improvements, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in the relevant field. Any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present utility model shall fall within the protection scope of the appended claims of the present utility model.

Claims

1. A broadband low-phase-noise fine-step frequency synthesizer system, characterized in that: The system includes a crystal oscillator (1), a first power splitter (2), a controller (17), a low-noise fine-in source unit, and a broadband spread-spectrum source unit. The output end of the crystal oscillator (1) is connected to the output end of the first power splitter (2), and the two output ends of the first power splitter (2) are respectively connected to the low-noise fine-in source unit and the broadband spread-spectrum source unit; The low-noise fine-in source unit outputs an FDDS signal and a local oscillator signal under the setting of the controller (17). After being mixed by the first mixer (7), a low-noise fine-step signal is obtained and input into the broadband spread-spectrum source unit; the broadband spread-spectrum source unit realizes the expansion of the output frequency range through a frequency synthesizer (15) and a second comb spectrum generator (11).

2. A broadband low-phase-noise fine-step frequency synthesizer system according to claim 1, wherein: The low-noise fine-step source unit includes a first comb spectrum generator (3), a second power splitter (4), a DDS (5), a first band-pass filter (6), and a first mixer (7); The output end of the first comb spectrum generator (3) is connected to the input end of the second power splitter (4). The two output ends of the second power splitter (4) are respectively connected to the input ends of the first mixer (7) and the DDS (5). The output end of the DDS (5) is connected to the input end of the first band-pass filter (6), and the output end of the first band-pass filter (6) is connected to the input end of the first mixer (7).

3. A broadband low-phase-noise fine-step frequency synthesizer system according to claim 1, characterized in that: The broadband spread-spectrum source unit includes a narrow-band amplifier (8), a second band-pass filter (9), a third power splitter (10), a second comb spectrum generator (11), a second mixer (12), a broadband amplifier (13), a radio frequency switch (14), a frequency synthesizer (15), and a loop filter (16); The narrow-band amplifier (8), the second band-pass filter (9), and the third power splitter (10) are connected in sequence. The two output ends of the third power splitter (10) are respectively connected to the input ends of the second comb spectrum generator (11) and the broadband amplifier (13); the output end of the second comb spectrum generator (11) is connected to the input end of the second mixer (12), the output end of the second mixer (12) is connected to the radio frequency switch (14), the radio frequency switch (14) is connected to the frequency synthesizer (15), and the output end of the frequency synthesizer (15) is connected to the input end of the second mixer (12); the output end of the broadband amplifier (13) is connected to the frequency synthesizer (15), and the loop filter is connected to the frequency synthesizer (15).

4. A broadband low-phase-noise fine-step frequency synthesizer system according to claim 3, characterized in that: The radio frequency switch (14) is connected to the REFin port (21) of the frequency synthesizer (15). The RFOUTB port of the frequency synthesizer (15) is connected to the second mixer (12). The output end of the broadband amplifier (13) is connected to the RFDin port (19) of the frequency synthesizer (15). The CP port (18) of the frequency synthesizer (15) is connected to the VT port (23) through the loop filter (16).

5. A broadband low-phase-noise fine-step frequency synthesizer system according to claim 3, wherein: One of the output ends of the first power splitter (2) is connected to the radio frequency switch (14), and the output end of the first mixer (7) is connected to the input end of the narrow-band amplifier (8).

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