A comb spectrum measurement system

Abstract

The application discloses a comb spectrum measurement system, and relates to the technical field of radio frequency measurement, which comprises a reference clock, first to third phase-locked loops, a first and a second comb spectrum generator, an upconverter, a first and a second downconverter and an analog-to-digital converter, the reference clock provides a homologous clock reference for each phase-locked loop and sampling; a baseband comb spectrum signal is shifted to a target carrier frequency band by the upconverter at the transmitting end; the receiving end is down-converted by two stages, the overall intermediate frequency bandwidth is compressed by using the double-comb spectrum difference frequency principle, and all measurement channels are synchronously collected by a single-channel analog-to-digital converter through a single transmission path. The intermediate frequency architecture is significantly simplified, the amplitude and phase consistency of multi-channel signals is improved, the measurement frequency band, the number and interval of channels are flexibly adjustable, and the application is suitable for multi-channel radio frequency measurement scenes with high integration and low power consumption.

Description

Technical Field

[0001] This invention relates to the field of radio frequency measurement technology, and in particular to a comb spectrum measurement system. Background Technology

[0002] In scenarios such as radio frequency multi-parameter measurement and material electromagnetic property detection, it is often necessary to simultaneously acquire and analyze multiple equally spaced radio frequency signals. Existing comb-spectrum radio frequency measurement systems generally employ a channel-independent processing architecture in their intermediate frequency demodulation stages: the multi-channel measurement signals output by the system are down-converted at the receiver, and each measurement channel is equipped with an independent frequency selection circuit, demodulation circuit, and signal conditioning circuit. After individual processing, each channel signal is connected to a corresponding multi-channel analog-to-digital converter unit for digital acquisition. If an IQ demodulation scheme is used, the required number of signal conditioning and acquisition channels will further double.

[0003] The above-mentioned independent channel processing architecture has inherent defects: as the number of measurement channels increases, the number of intermediate frequency devices required by the system will increase linearly, directly resulting in a complex overall circuit structure, high size and power consumption, making it difficult to meet the requirements of highly integrated and low-power embedded applications; at the same time, the inherent deviations in the performance of devices in multiple independent circuits will cause poor amplitude and phase consistency of signals in each channel, requiring additional complex channel calibration mechanisms and long-term maintenance, resulting in insufficient system reliability. Summary of the Invention

[0004] To address the technical problems of existing multi-channel comb spectrum RF measurement systems that employ a separate intermediate frequency processing architecture for each channel, resulting in complex circuit structures and difficulty in ensuring the consistency of signal amplitude and phase across measurement channels, this invention provides a comb spectrum measurement system.

[0005] The technical solution adopted in this invention is:

[0006] A comb spectrum measurement system includes a reference clock, a first phase-locked loop, a first comb spectrum generator, an up-converter, a measurement signal output port, a measurement signal input port, a first-stage down-converter, a third phase-locked loop, a second phase-locked loop, a second comb spectrum generator, a second-stage down-converter, and an analog-to-digital converter.

[0007] The first output terminal of the reference clock is connected to the clock input terminal of the first phase-locked loop; the radio frequency output terminal of the first phase-locked loop is connected to the input terminal of the first comb spectrum generator; the output terminal of the first comb spectrum generator is connected to the intermediate frequency input terminal of the upconverter; and the radio frequency output terminal of the upconverter is connected to the measurement signal output port.

[0008] The measurement signal input port is connected to the RF input terminal of the first-stage down-converter; the second output terminal of the reference clock is connected to the clock input terminal of the third phase-locked loop; the first RF output terminal of the third phase-locked loop is connected to the local oscillator input terminal of the up-converter.

[0009] The second RF output terminal of the third phase-locked loop is connected to the local oscillator input terminal of the first-stage downconverter; the third output terminal of the reference clock is connected to the clock input terminal of the second phase-locked loop; the RF output terminal of the second phase-locked loop is connected to the input terminal of the second comb spectrum generator.

[0010] The output terminal of the second comb spectrum generator is connected to the local oscillator input terminal of the second-stage downconverter; the intermediate frequency output terminal of the first-stage downconverter is connected to the radio frequency input terminal of the second-stage downconverter; the intermediate frequency output terminal of the second-stage downconverter is connected to the signal input terminal of the analog-to-digital converter.

[0011] The fourth output terminal of the reference clock is connected to the sampling clock input terminal of the analog-to-digital converter; the digital output terminal of the analog-to-digital converter is used to output digital measurement data.

[0012] Preferably, the frequencies of the signals input to the local oscillator input terminal of the up-converter and the local oscillator input terminal of the first-stage down-converter are the carrier frequencies;

[0013] The signal output from the intermediate frequency output terminal of the first-stage down-converter is the first intermediate frequency signal, the signal input from the local oscillator input terminal of the second-stage down-converter is the comb spectrum local oscillator signal, and the signal output from the intermediate frequency output terminal of the second-stage down-converter is the second intermediate frequency signal.

[0014] The harmonic frequencies of the signal output by the first comb spectrum generator are integer multiples of the frequency of the signal output by the first phase-locked loop, and the harmonic frequencies of the signal output by the second comb spectrum generator are integer multiples of the frequency of the signal output by the second phase-locked loop.

[0015] The frequency of each channel of the measurement signal output from the measurement signal output port is the sum of the corresponding harmonic frequency of the signal output from the first comb generator and the carrier frequency.

[0016] The difference between the signal frequency output by the first phase-locked loop and the signal frequency output by the second phase-locked loop is the frequency difference; the frequency of each channel of the second intermediate frequency signal is the frequency difference multiplied by the corresponding harmonic order.

[0017] Preferably, the first comb spectrum generator and the second comb spectrum generator each output harmonics from the lowest harmonic order to the highest harmonic order, and the number of channels of the second intermediate frequency signal is the difference between the highest harmonic order and the lowest harmonic order plus one. The lowest harmonic order and the highest harmonic order are both positive integers and the highest harmonic order is not lower than the lowest harmonic order.

[0018] Preferably, the frequency difference constitutes the channel spacing of the second intermediate frequency signal, the lower limit of the frequency band of the second intermediate frequency signal is the frequency difference multiplied by the lowest harmonic number, the upper limit of the frequency band of the second intermediate frequency signal is the frequency difference multiplied by the highest harmonic number, and the frequency band range of the second intermediate frequency signal is within the collectable frequency band range of the analog-to-digital converter.

[0019] Preferably, the reference clock provides a common clock reference for the first phase-locked loop, the third phase-locked loop, and the second phase-locked loop, and the phase of the signals output by the first phase-locked loop, the third phase-locked loop, and the second phase-locked loop is locked to the reference clock.

[0020] Preferably, the carrier frequency is set independently of the signal frequency output by the first phase-locked loop and the signal frequency output by the second phase-locked loop, and the carrier frequency determines the frequency band position of the measurement signal.

[0021] Preferably, the second intermediate frequency signal is a comb spectrum signal, and the second intermediate frequency signal is input to the analog-to-digital converter through a single signal transmission path between the intermediate frequency output terminal of the second-stage downconverter and the signal input terminal of the analog-to-digital converter. The analog-to-digital converter simultaneously acquires all channels of the second intermediate frequency signal using a single acquisition channel.

[0022] Preferably, it further includes a digital signal processing unit, wherein the digital output terminal of the analog-to-digital converter is connected to the input terminal of the digital signal processing unit, and the output terminal of the digital signal processing unit serves as the measurement result output terminal of the comb spectrum measurement system.

[0023] The beneficial effects of the present invention are at least one of the following:

[0024] This invention, through a two-stage frequency conversion architecture combined with a dual-comb spectrum difference frequency design, can compress the bandwidth of multi-channel RF measurement signals to a low-frequency band suitable for single-channel acquisition. This allows all measurement channels to be synchronously acquired via a single-channel analog-to-digital converter through the same transmission path. This eliminates the need for multiple independently configured frequency selection, demodulation, and signal conditioning circuits in traditional multi-channel measurement systems, reducing the number of hardware components required, lowering system hardware costs, power consumption, and size, and making it more suitable for applications with high integration requirements.

[0025] In this invention, all measurement channels share the same transmission path and the same analog-to-digital converter in the receiving link. The relative amplitude and relative phase relationship of each channel signal depends only on the frequency response characteristics of the shared devices on the path and is not affected by the performance differences of multi-channel devices. The amplitude and phase consistency between channels is guaranteed by the system architecture itself, which can reduce the design complexity of multi-channel calibration and reduce the maintenance requirements during system use.

[0026] In this invention, the reference clocks of the three phase-locked loops and the sampling clock of the analog-to-digital converter all originate from the same reference clock. The signals throughout the entire link remain coherent, which reduces the interference of clock drift on the measurement results and keeps the parameters of the intermediate frequency signal stable when there is no target under test, thus improving the reliability of the measurement results. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the system architecture of the present invention.

[0028] Reference numerals in the attached diagram: 1. Reference clock; 2. First phase-locked loop; 3. First comb spectrum generator; 4. Up-converter; 5. Measurement signal output port; 6. Measurement signal input port; 7. First-stage down-converter; 8. Third phase-locked loop; 9. Second phase-locked loop; 10. Second comb spectrum generator; 11. Second-stage down-converter; 12. Analog-to-digital converter; 13. Digital signal processing unit. Detailed Implementation

[0029] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0030] Example 1

[0031] like Figure 1 As shown, this embodiment provides a comb spectrum measurement system, including: a reference clock 1, a first phase-locked loop 2, a first comb spectrum generator 3, an up-converter 4, a measurement signal output port 5, a measurement signal input port 6, a first-stage down-converter 7, a third phase-locked loop 8, a second phase-locked loop 9, a second comb spectrum generator 10, a second-stage down-converter 11, an analog-to-digital converter 12, and a digital signal processing unit 13.

[0032] The reference clock 1 has a first output terminal, a second output terminal, a third output terminal, and a fourth output terminal. In an optional implementation, the clock signal of the reference clock 1 can be split by a power divider to obtain the first to fourth outputs. The reference clock 1 is used to generate a constant frequency signal with low phase noise, providing a unified clock reference for the entire system. The reference clock 1 can be implemented using any of the following devices with stable frequency output capability: a temperature-controlled crystal oscillator, a voltage-controlled crystal oscillator, a temperature-compensated crystal oscillator, a digitally compensated crystal oscillator, a differential crystal oscillator, a timing pulse module, an external clock input, or a clock manager.

[0033] like Figure 1 As shown, the first output terminal of reference clock 1 is connected to the clock input terminal of the first phase-locked loop 2. The first phase-locked loop 2 compares the phase of the clock signal output by reference clock 1 with the phase of reference clock 1, and locks its own output signal frequency to the target frequency through an internal feedback loop. The RF output terminal of the first phase-locked loop 2 outputs a signal at the target frequency. The phase-locked loop can be constructed in hardware as a phase-frequency discriminator, a charge pump, a loop filter, a voltage-controlled oscillator, and a programmable frequency divider.

[0034] The RF output terminal of the first phase-locked loop 2 is connected to the input terminal of the first comb spectrum generator 3. The first comb spectrum generator 3 is used to generate various harmonics of its input signal frequency, and its output signal is a comb spectrum signal containing multiple harmonics. The first comb spectrum generator 3 can be implemented using nonlinear devices such as step recovery diodes or nonlinear transmission lines. Depending on the performance of the devices, it can typically generate several to dozens of harmonics.

[0035] The output of the first comb spectrum generator 3 is connected to the intermediate frequency input of the upconverter 4. The upconverter 4 is used to upconvert the signal input to its intermediate frequency input and the signal input to its local oscillator input, and output the upper difference frequency signal of the two, that is, the sum of the frequencies of the two input signals.

[0036] The RF output terminal of the upconverter 4 is connected to the measurement signal output port 5, which is used to output a measurement signal to the target under test.

[0037] The measurement signal input port 6 is connected to the radio frequency input terminal of the first-stage downconverter 7. The measurement signal input port 6 is used to receive the measurement signal returned after being acted upon by the target under test.

[0038] like Figure 1 As shown, the second output terminal of the reference clock 1 is connected to the clock input terminal of the third phase-locked loop 8. The third phase-locked loop 8 compares the phase of the clock signal output by the reference clock 1 and locks it to generate a carrier signal. The third phase-locked loop 8 has a first radio frequency output terminal and a second radio frequency output terminal. The two output signals have the same frequency. In an optional embodiment, the radio frequency signal of the third phase-locked loop 8 can be split by a power divider to obtain two outputs with the same frequency.

[0039] In an optional implementation, when the required carrier frequency is high, a frequency multiplier and a drive amplifier can be added to the output of the third phase-locked loop 8 to multiply the base frequency signal output by the phase-locked loop to the target carrier frequency.

[0040] like Figure 1 As shown, the first RF output terminal of the third phase-locked loop 8 is connected to the local oscillator input terminal of the up-converter 4, and the second RF output terminal of the third phase-locked loop 8 is connected to the local oscillator input terminal of the first-stage down-converter 7.

[0041] Among them, the first-stage downconverter 7 is used to downconvert the signal input to its radio frequency input terminal and the signal input to its local oscillator input terminal, and output the down-difference frequency signal between the two, that is, the frequency of the radio frequency input terminal signal minus the frequency of the local oscillator input terminal signal.

[0042] like Figure 1 As shown, the third output terminal of reference clock 1 is connected to the clock input terminal of the second phase-locked loop 9. The second phase-locked loop 9 compares the phase of the clock signal output by reference clock 1 and locks with it, outputting a signal at the target frequency. The RF output terminal of the second phase-locked loop 9 is connected to the input terminal of the second comb spectrum generator 10.

[0043] The second comb spectrum generator 10 is used to generate higher harmonics of its input signal frequency and output comb spectrum signals, and its implementation is the same as that of the first comb spectrum generator 3.

[0044] like Figure 1 As shown, the output terminal of the second comb spectrum generator 10 is connected to the local oscillator input terminal of the second-stage downconverter 11, and the intermediate frequency output terminal of the first-stage downconverter 7 is connected to the radio frequency input terminal of the second-stage downconverter 11.

[0045] The secondary downconverter 11 is used to downconvert the signal input at its RF input terminal to the signal input at its local oscillator input terminal, and output the lower difference frequency signal between the two.

[0046] The intermediate frequency output terminal of the secondary downconverter 11 is connected to the signal input terminal of the analog-to-digital converter 12, which is used to convert the input analog signal into a digital signal.

[0047] The fourth output terminal of reference clock 1 is connected to the sampling clock input terminal of analog-to-digital converter 12. The sampling clock of analog-to-digital converter 12 is from the same source as reference clock 1. The digital output terminal of analog-to-digital converter 12 is used to output digital measurement data.

[0048] In this embodiment, the signals input to the local oscillator input terminal of the up-converter 4 and the local oscillator input terminal of the first-stage down-converter 7 both originate from the third phase-locked loop 8. The frequencies of the two signals are consistent and are collectively denoted as the carrier frequency. .

[0049] The signal output from the intermediate frequency output terminal of the first-stage downconverter 7 is called the first intermediate frequency signal. The first intermediate frequency signal contains measurement information and is denoted as... The signal output from the second comb spectrum generator 10 and input to the local oscillator input terminal of the second-stage down-converter 11 is called the comb spectrum local oscillator signal, and its corresponding system equivalent local oscillator frequency is denoted as the local oscillator signal frequency. .

[0050] The signal output from the intermediate frequency output terminal of the secondary downconverter 11 is called the second intermediate frequency signal, and its frequency is denoted as the system intermediate frequency. The second intermediate frequency signal is a baseband signal containing measurement information.

[0051] Let the frequency of the signal output by the first phase-locked loop 2 be... The frequency of the signal output by the second phase-locked loop 9 is Because the first comb spectrum generator 3 uses a frequency of The signal is used as the fundamental frequency to generate harmonics. Therefore, in the comb spectrum signal output by the first comb spectrum generator 3, the frequency of the corresponding subharmonic is an integer multiple of the fundamental frequency.

[0052] Similarly, the second comb spectrum generator 10 uses a frequency of The signal is used as the fundamental frequency to generate harmonics. In the comb-spectrum local oscillator signal of its output, the frequency of the corresponding subharmonic is an integer multiple of the fundamental frequency.

[0053] In the transmission link, the upconverter 4 converts the baseband comb spectrum signal output by the first comb spectrum generator 3 with a frequency of... The carrier signal is up-converted to produce an upper difference frequency signal. Therefore, the frequency of the measurement signal output from measurement signal output port 5 is... satisfy:

[0054]

[0055] That is, the measurement signal is a multi-channel comb spectrum signal, and the frequency of each channel is the corresponding harmonic frequency output by the first comb spectrum generator 3 and the carrier frequency. The sum of, among which and The harmonic order is the output of the comb spectrum generator. For the lowest harmonic order, The highest harmonic order, , All are positive integers, and .

[0056] In the receiving link, the measurement signal enters the RF input terminal of the first-stage downconverter 7 via the measurement signal input port 6, and is synchronized with the frequency of... The carrier signal is down-converted to produce a lower difference frequency signal, which is then used to obtain the first intermediate frequency signal. :

[0057]

[0058] The first intermediate frequency (IF) signal is restored to the frequency composition of the baseband comb spectrum signal in the transmission link, while also carrying the power, frequency, and phase change information introduced by the target under test. The first IF signal enters the RF input of the second-stage downconverter 11 and is downconverted with the comb spectrum local oscillator signal output from the second comb spectrum generator 10. In the normal operating mode of this system, the harmonics of the first and second comb spectrum generators 3 and 10 are mixed in the second downconverter 11. Through frequency parameter design, only the difference frequency component of the same harmonic falls into the second IF target frequency band, while the remaining mixed components are out of band. At this time, the overall local oscillator signal frequency of the system is... With the second intermediate frequency signal frequency satisfy:

[0059]

[0060]

[0061] The output frequency of the first phase-locked loop 2 With the output frequency of the second phase-locked loop 9 The difference between them is denoted as the frequency difference. ,Right now Then the frequencies of each channel of the second intermediate frequency signal can be simplified as follows: .

[0062] Therefore, the second intermediate frequency signal is a baseband signal in the form of a comb spectrum, and the frequency of each channel is equal to the frequency difference. Multiply by the corresponding harmonic order.

[0063] Furthermore, in this embodiment, the first comb spectrum generator 3 and the second comb spectrum generator 10 each output from the lowest harmonic order. Up to the highest harmonic order The harmonics of each frequency. Correspondingly, the number of channels in the second intermediate frequency signal is... indivual.

[0064] In the frequency configuration of this embodiment, the frequency difference The channel spacing that constitutes the interval between adjacent channels in the second intermediate frequency (IF) signal, and the lower limit of the bandwidth of the second IF signal are... The upper limit of the frequency band is The entire frequency band range is to .

[0065] In practical design, the frequency band of the second intermediate frequency signal should be within the collectable frequency band of the analog-to-digital converter 12, that is, the Nyquist sampling frequency of the analog-to-digital converter 12, which is half of the sampling rate, is greater than the upper limit of the frequency band, so as to ensure that the sampled digital signal does not undergo spectral aliasing.

[0066] In this embodiment, reference clock 1 provides a common clock reference for the first phase-locked loop 2, the third phase-locked loop 8, and the second phase-locked loop 9. The phases of the signals output by the first phase-locked loop 2, the third phase-locked loop 8, and the second phase-locked loop 9 are all locked to reference clock 1. Simultaneously, the sampling clock of the analog-to-digital converter 12 is also provided by the same reference clock 1, ensuring that the entire system maintains a coherent relationship across the entire link of transmission, reception, and acquisition signals.

[0067] Therefore, without considering the influence of the target being measured, the power, frequency, and phase of each channel in the intermediate frequency signal remain stable and will not drift; any power, frequency, or phase changes measured by the system can be attributed to the effect of the target being measured.

[0068] In this embodiment, the carrier frequency With the output frequency of the first phase-locked loop 2 The output frequency of the second phase-locked loop 9 Each is set independently and without dependency on the others; carrier frequency It mainly determines the frequency band location of the measured signal, while The channel spacing for measuring the comb spectrum is determined, and the following is introduced: This determines the frequency range of the second intermediate frequency signal.

[0069] In an optional implementation, by replacing the third phase-locked loop 8 and the corresponding up-converter 4 and first-level down-converter 7, the system architecture can be directly applied to different frequency bands such as microwave, millimeter wave, or terahertz without redesigning the comb spectrum generation part of the transmit link and the intermediate frequency demodulation part of the receive link. The output frequency of each phase-locked loop can be modified by programming, and frequency switching can be performed without shutting down the system.

[0070] In this embodiment, the intermediate frequency signal is a comb spectrum signal, and all its channels share the same transmission link, that is, a single signal transmission path between the intermediate frequency output terminal of the second-stage downconverter 11 and the signal input terminal of the analog-to-digital converter 12, and is input to the analog-to-digital converter 12.

[0071] The analog-to-digital converter 12 simultaneously acquires all channels of the second intermediate frequency signal with a single signal input terminal and a single acquisition channel. Compared with the traditional multi-channel system where each channel needs to be independently set for frequency selection, demodulation, conditioning and acquisition channels, this embodiment eliminates a large number of independent channel devices, greatly simplifies the system structure and reduces hardware cost, power consumption, size and weight.

[0072] Meanwhile, since all channels share the same transmission path and the same analog-to-digital converter 12, the relative amplitude and relative phase relationship between channels in the second intermediate frequency signal depends only on the frequency response characteristics of the shared device and is not affected by the differences in multi-channel devices. Therefore, the amplitude and phase consistency of each channel signal is guaranteed by the system structure itself, without the need for additional multi-channel calibration and maintenance.

[0073] In this embodiment, as Figure 1 As shown, the comb spectrum measurement system also includes a digital signal processing unit 13. The digital output terminal of the analog-to-digital converter 12 is connected to the input terminal of the digital signal processing unit 13, and the output terminal of the digital signal processing unit 13 serves as the measurement result output terminal of the entire comb spectrum measurement system.

[0074] The digital signal processing unit 13 can be implemented using a field-programmable gate array (FPGA), a digital signal processor (DSP), or a combination of both. The digital signal processing unit 13 is used to analyze and calculate the digital measurement data output by the analog-to-digital converter 12. The processing performed by the digital signal processing unit 13 includes: separating the channel signals in the second intermediate frequency signal in the frequency domain by using a fast Fourier transform (FFT); extracting the amplitude and phase information of each channel signal; and inverting the physical parameters of the target under test based on the amplitude and phase changes of each channel signal.

[0075] To further illustrate the feasibility and flexible parameter adaptation of this embodiment, two specific frequency parameter configuration examples are given below.

[0076] Example 2

[0077] In this embodiment, the first set of parameters is exemplified as follows:

[0078] Take the output frequency of the first phase-locked loop 2 MHz, the output frequency of the second phase-locked loop 9 MHz, then the frequency difference MHz.

[0079] The first comb spectrum generator 3 and the second comb spectrum generator 10 each output... to Second harmonic, i.e. , There are 5 channels.

[0080] Take carrier frequency GHz, this frequency can be achieved by adding a frequency multiplier and a drive amplifier at the output of the third phase-locked loop 8.

[0081] In the transmission link, as shown in Table 1, the baseband comb spectrum signal output by the first comb spectrum generator 3 has frequencies of 1GHz, 2GHz, 3GHz, 4GHz, and 5GHz; after upconversion by the upconverter 4 and the 40GHz carrier signal, the five channels of the transmitted measurement signal are 41GHz, 42GHz, 43GHz, 44GHz, and 45GHz, with a channel spacing of 1GHz. The values ​​are equal.

[0082] Table 1. Correspondence of signal frequencies for each stage under the first set of frequency parameters.

[0083] Frequency parameter items Baseband value (GHz) Signal name First harmonic Second harmonic Third harmonic 4th harmonic 5th harmonic First phase-locked loop 1 Baseband comb spectrum signal (GHz) 1 2 3 4 5 Third phase-locked loop 40 Transmit measurement signal (GHz) 41 42 43 44 45 Third phase-locked loop 40 First intermediate frequency signal (GHz) 1 2 3 4 5 Second phase-locked loop 0.999 Comb-shaped spectrum local oscillator signal (GHz) 0.999 1.998 2.997 3.996 4.995 — — Second intermediate frequency signal (MHz) 1 2 3 4 5

[0084] As shown in Table 1, in the receiving link, after downconversion of the 40GHz carrier signal by the first-stage downconverter 7, the first intermediate frequency (IF) signal is restored to a 5-channel signal ranging from 1GHz to 5GHz, with an adjacent channel spacing of 1GHz. The first IF signal and the comb spectrum local oscillator signal output by the second comb spectrum generator 10 are then mixed by corresponding harmonic pairing by the second-stage downconverter 11. The five channels of the second IF signal are 1MHz, 2MHz, 3MHz, 4MHz, and 5MHz, with a channel spacing of 1MHz. The values ​​are equal, and the frequency band ranges from 1MHz to 5MHz.

[0085] According to the Nyquist sampling theorem, the analog-to-digital converter 12 can synchronously acquire data from the five channels with a sampling rate of at least 10 MSa / s, making it suitable for applications where the bandwidth required for each channel is less than ± Application scenarios.

[0086] Example 3

[0087] In this embodiment, the second set of parameters is exemplified as follows:

[0088] Set the output frequency of the first phase-locked loop 2 MHz, the output frequency of the second phase-locked loop 9 MHz, then the frequency difference MHz.

[0089] The first comb spectrum generator 3 and the second comb spectrum generator 10 each output... to Second harmonic, i.e. , The number of channels is 8, and the carrier frequency is used. GHz.

[0090] The frequency correspondence of signals in each stage is shown in Table 2. In the transmission link, the baseband comb spectrum signal output by the first comb spectrum generator 3 has a frequency range of 0.5 GHz to 4 GHz; after upconversion with the 60 GHz carrier signal by the upconverter 4, the frequency range of the eight channels of the transmitted measurement signal is 60.5 GHz to 64 GHz, with an adjacent channel spacing of 0.5 GHz. The values ​​are equal.

[0091] As shown in Table 2, in the receiving link, after downconversion of the 60GHz carrier signal by the first-stage downconverter 7, the first intermediate frequency signal is restored to an 8-channel signal ranging from 0.5GHz to 4GHz, with adjacent channel spacing of [missing information]. The first intermediate frequency (IF) signal and the comb spectrum local oscillator signal output from the second comb spectrum generator 10 are mixed by corresponding harmonic pairing in a two-stage down-converter 11. The eight channels of the second IF signal have a frequency range of 2MHz to 16MHz, with a channel spacing of 2MHz. The values ​​are equal.

[0092] Table 2. Correspondence of signal frequencies for each stage under the second set of frequency parameters.

[0093] Frequency parameter items Baseband value (GHz) Signal name First harmonic Second harmonic Third harmonic 4th harmonic 5th harmonic 6th harmonic 7th harmonic 8th harmonic First phase-locked loop 0.5 Baseband comb spectrum signal (GHz) 0.5 1 1.5 2 2.5 3 3.5 4 Third phase-locked loop 60 Transmit measurement signal (GHz) 60.5 61 61.5 62 62.5 63 63.5 64 Third phase-locked loop 60 First intermediate frequency signal (GHz) 0.5 1 1.5 2 2.5 3 3.5 4 Second phase-locked loop 0.498 Comb-shaped spectrum local oscillator signal (GHz) 0.498 0.996 1.494 1.992 2.49 2.988 3.486 3.984 — — Second intermediate frequency signal (MHz) 2 4 6 8 10 12 14 16

[0094] According to the Nyquist sampling theorem, the analog-to-digital converter 12 can synchronously acquire data from the eight channels with a sampling rate of at least 32 MSa / s, making it suitable for applications where the bandwidth required for each channel is less than [specified value]. Application scenarios for MHz.

[0095] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, particularly regarding the filtering and amplification of local signals; these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A comb spectrum measurement system, characterized in that, It includes a reference clock, a first phase-locked loop, a first comb spectrum generator, an up-converter, a measurement signal output port, a measurement signal input port, a first-stage down-converter, a third phase-locked loop, a second phase-locked loop, a second comb spectrum generator, a second-stage down-converter, and an analog-to-digital converter; The first output terminal of the reference clock is connected to the clock input terminal of the first phase-locked loop; the radio frequency output terminal of the first phase-locked loop is connected to the input terminal of the first comb spectrum generator. The output of the first comb spectrum generator is connected to the intermediate frequency input of the upconverter; The radio frequency output terminal of the upconverter is connected to the measurement signal output port; The measurement signal input port is connected to the radio frequency input terminal of the first-stage downconverter; The second output terminal of the reference clock is connected to the clock input terminal of the third phase-locked loop; The first radio frequency output terminal of the third phase-locked loop is connected to the local oscillator input terminal of the upconverter; The second RF output terminal of the third phase-locked loop is connected to the local oscillator input terminal of the first-stage downconverter; the third output terminal of the reference clock is connected to the clock input terminal of the second phase-locked loop. The radio frequency output terminal of the second phase-locked loop is connected to the input terminal of the second comb spectrum generator; The output terminal of the second comb spectrum generator is connected to the local oscillator input terminal of the second-stage downconverter; the intermediate frequency output terminal of the first-stage downconverter is connected to the radio frequency input terminal of the second-stage downconverter. The intermediate frequency output terminal of the secondary downconverter is connected to the signal input terminal of the analog-to-digital converter. The fourth output terminal of the reference clock is connected to the sampling clock input terminal of the analog-to-digital converter; the digital output terminal of the analog-to-digital converter is used to output digital measurement data.

2. The comb spectrum measurement system according to claim 1, characterized in that, The frequencies of the signals input to the local oscillator input terminal of the up-converter and the signals input to the local oscillator input terminal of the first-stage down-converter are the carrier frequencies. The signal output from the intermediate frequency output terminal of the first-stage down-converter is the first intermediate frequency signal, the signal input from the local oscillator input terminal of the second-stage down-converter is the comb spectrum local oscillator signal, and the signal output from the intermediate frequency output terminal of the second-stage down-converter is the second intermediate frequency signal. The harmonic frequencies of the signal output by the first comb spectrum generator are integer multiples of the frequency of the signal output by the first phase-locked loop, and the harmonic frequencies of the signal output by the second comb spectrum generator are integer multiples of the frequency of the signal output by the second phase-locked loop. The frequency of each channel of the measurement signal output from the measurement signal output port is the sum of the corresponding harmonic frequency of the signal output from the first comb generator and the carrier frequency. The difference between the signal frequency output by the first phase-locked loop and the signal frequency output by the second phase-locked loop is the frequency difference; the frequency of each channel of the second intermediate frequency signal is the frequency difference multiplied by the corresponding harmonic order.

3. The comb spectrum measurement system according to claim 2, characterized in that, The first comb spectrum generator and the second comb spectrum generator each output harmonics from the lowest harmonic order to the highest harmonic order. The number of channels of the second intermediate frequency signal is the difference between the highest harmonic order and the lowest harmonic order plus one. The lowest harmonic order and the highest harmonic order are both positive integers, and the highest harmonic order is not lower than the lowest harmonic order.

4. The comb spectrum measurement system according to claim 3, characterized in that, The frequency difference constitutes the channel spacing of the second intermediate frequency signal. The lower limit of the frequency band of the second intermediate frequency signal is the frequency difference multiplied by the lowest harmonic order, and the upper limit of the frequency band of the second intermediate frequency signal is the frequency difference multiplied by the highest harmonic order. The frequency band range of the second intermediate frequency signal is within the collectable frequency band range of the analog-to-digital converter.

5. The comb spectrum measurement system according to claim 1, characterized in that, The reference clock provides a common clock reference for the first phase-locked loop, the third phase-locked loop, and the second phase-locked loop, and the phase of the signals output by the first phase-locked loop, the third phase-locked loop, and the second phase-locked loop is locked to the reference clock.

6. The comb spectrum measurement system according to claim 2, characterized in that, The carrier frequency is set independently of the signal frequency output by the first phase-locked loop and the signal frequency output by the second phase-locked loop, and the carrier frequency determines the frequency band position of the measurement signal.

7. The comb spectrum measurement system according to claim 2, characterized in that, The second intermediate frequency signal is a comb spectrum signal. The second intermediate frequency signal is input to the analog-to-digital converter through a single signal transmission path between the intermediate frequency output terminal of the second-stage downconverter and the signal input terminal of the analog-to-digital converter. The analog-to-digital converter simultaneously acquires all channels of the second intermediate frequency signal through a single acquisition channel.

8. The comb spectrum measurement system according to claim 1, characterized in that, It also includes a digital signal processing unit, wherein the digital output terminal of the analog-to-digital converter is connected to the input terminal of the digital signal processing unit, and the output terminal of the digital signal processing unit serves as the measurement result output terminal of the comb spectrum measurement system.

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