Broadband receiver ADC nonlinear spurious suppression method and device

Abstract

The invention discloses a broadband receiver ADC nonlinear spurious suppression method and device, and relates to the technical field of instruments and meters, and the method comprises the following steps: receiving an intermediate frequency signal, carrying out the analog-to-digital conversion of the intermediate frequency signal, and obtaining a digital intermediate frequency signal, the intermediate frequency signal being obtained through the receiving of a superheterodyne architecture; the method comprises the following steps: reducing the signal bandwidth of a digital intermediate frequency signal by using a CIC extraction mode to obtain different signal bandwidths BW, and performing spectral analysis on the different signal bandwidths BW by using a fixed-point FFT to obtain corresponding resolution bandwidths RBW; on the premise that the cost of the receiver is not increased, spurious signals under the narrow-band instantaneous bandwidth are reduced, and the index of the receiver is improved.

Description

Technical Field

[0001] The invention relates to the technical field of instruments and meters, and in particular to a method and a device for suppressing nonlinear spurious signals of ADC of a broadband receiver. Background Art

[0002] With the advancement of electronic technology, the improvement of processor performance, and the widespread application of FPGA in digital signal processing, receiver instruments have increasingly higher requirements in terms of performance and instantaneous bandwidth.

[0003] In the receiver, there are many factors that affect its bandwidth, mainly determined by the ADC sampling rate (generally, the analog bandwidth of the ADC can reach its maximum sampling rate fs) and the processing power after digitization. The ADC sampling rate determines its maximum bandwidth to be fs / 2. The higher the ADC sampling rate, the higher its cost, and at the same time, the higher the performance requirements for the back-end FPGA.

[0004] In order to obtain the maximum bandwidth, the intermediate frequency f is generally selected. c =N*f s / 4(N=1,2,3,4...), we can get f s / 2 theoretical bandwidth, but due to the nonlinearity of the ADC, the input signal is at the intermediate frequency f c When the sampling clock is close to the sampling clock frequency, its harmonics and the sampling clock harmonics generate spurious signals, and the spurious signal frequency falls within the useful signal bandwidth.

[0005] When the resolution bandwidth (RBW) is large, the noise is large and can drown out the above-mentioned spurious signals; when the RBW is small, the intermodulation signals will be exposed due to the decrease in noise, affecting the measurement results. Summary of the invention

[0006] In order to solve the deficiencies mentioned in the above background technology, the object of the present invention is to provide a method and device for suppressing nonlinear spurious signals of ADC of a broadband receiver.

[0007] In a first aspect, the purpose of the present invention can be achieved by the following technical solution: a method for suppressing nonlinear spurious signals of a broadband receiver ADC, the method comprising the following steps:

[0008] Receiving an intermediate frequency signal, performing analog-to-digital conversion on the intermediate frequency signal, and obtaining a digital intermediate frequency signal, wherein the intermediate frequency signal is received using a superheterodyne architecture;

[0009] The digital intermediate frequency signal is subjected to CIC extraction to reduce the signal bandwidth, and different signal bandwidths BW are obtained. A fixed-point FFT is used to perform spectrum analysis on different signal bandwidths BW to obtain the corresponding resolution bandwidth.

[0010] In combination with the first aspect, in some implementations of the first aspect, the method further includes: under a broadband instantaneous bandwidth, the input signal frequency is f in , the local oscillator frequency is f lo1 , after frequency conversion, the intermediate frequency center frequency is f if1 , the tuning equation is:

[0011] f if1 =f in -f lo1

[0012] f if1 -f nco1 =0

[0013] After the analog-to-digital conversion, the digital down-conversion is performed to move the signal to the baseband. The frequency of the NCO is f nco1 ; At this time, f if1 =f s *3 / 4, f nco1 =f s *1 / 4.

[0014] In combination with the first aspect, in some implementations of the first aspect, the method further includes: the maximum instantaneous bandwidth obtained by the superheterodyne architecture is: BW (max) =f s *1 / 2.

[0015] In combination with the first aspect, in some implementations of the first aspect, the method further includes: adjusting the local oscillator frequency to f under the narrowband instantaneous bandwidth lo2 , where the center frequency is f if2 , the frequency of the NCO in the digital down-conversion is f nco2 , the tuning equation is:

[0016] f if2 =f in -f lo2

[0017] f if2 -f nco2 =0

[0018] In combination with the first aspect, in some implementations of the first aspect, the method further includes: under the narrowband instantaneous bandwidth, the intermediate frequency center frequency offset should meet the following conditions: s / 32≤|f lo2 -f lo1 |=|f if2 -f if1 |=|f nco1 -f nco2 |≤1.8*f s / 32, and the intermediate frequency bandwidth at this time is ≤fs / 32.

[0019] In a second aspect, in order to achieve the above-mentioned object, the present invention discloses a broadband receiver ADC nonlinear spurious suppression device, comprising:

[0020] A signal receiving module, used for receiving an intermediate frequency signal, performing analog-to-digital conversion on the intermediate frequency signal, and obtaining a digital intermediate frequency signal, wherein the intermediate frequency signal is received by a superheterodyne receiver;

[0021] The spectrum analysis module is used to reduce the signal bandwidth of the digital intermediate frequency signal by using CIC extraction to obtain different signal bandwidths BW, and use fixed-point FFT to perform spectrum analysis on different signal bandwidths BW to obtain the resolution bandwidth.

[0022] In combination with the second aspect, in some implementations of the second aspect, the device further includes: the intermediate frequency signal input signal frequency of the signal receiving module is f in , the local oscillator frequency is f lo1 , after frequency conversion, the intermediate frequency center frequency is f if1 , the tuning equation is:

[0023] f if1 =f in -f lo1

[0024] f if1 -f nco1 =0

[0025] After the analog-to-digital conversion, the digital down-conversion is performed to move the signal to the baseband. The frequency of the NCO is f nco1 ; At this time, f if1 =f s *3 / 4, f nco1 =f s *1 / 4.

[0026] In combination with the second aspect, in some implementations of the second aspect, the device further includes: the maximum instantaneous bandwidth obtained by the superheterodyne architecture is: BW (max) =f s *1 / 2.

[0027] In combination with the second aspect, in some implementations of the second aspect, the device further includes: in a narrow-band instantaneous bandwidth, adjusting the local oscillator frequency to f lo2 , where the center frequency is f if2 , the frequency of the NCO in the digital down-conversion is f nco2 , the tuning equation is:

[0028] f if2 =f in -f lo2

[0029] f if2 -f nco2 =0.

[0030] In combination with the second aspect, in some implementations of the second aspect, the device further includes: under the narrowband instantaneous bandwidth, the intermediate frequency center frequency offset f s / 32≤|f lo2 -f lo1 |=|f if2 -f if1 |=|f nco1 -f nco2 |≤1.8*f s / 32, and the intermediate frequency bandwidth at this time is ≤fs / 32.

[0031] Beneficial effects of the present invention:

[0032] The present invention reduces the spurious signals under the narrow-band instantaneous bandwidth and improves the indicators of the receiver without increasing the cost of the receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 It is a schematic flow chart of the method of the present invention;

[0035] Figure 2 It is a hardware principle block diagram of the present invention;

[0036] Figure 3 It is a schematic diagram of the workflow of the present invention;

[0037] Figure 4 This invention if1 =f s * Schematic diagram of broadband spurious of ADC at 3 / 4;

[0038] Figure 5 This invention if1 =f s * Schematic diagram of narrow-band spurious of ADC at 3 / 4;

[0039] Figure 6 This invention if2 Relative f if1 Schematic diagram of narrowband spurious of ADC after frequency deviation;

[0040] Figure 7It is a schematic diagram of the structure of the device of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Embodiment 1:

[0043] like Figure 1 As shown, a method for suppressing nonlinear spurious signals of a broadband receiver ADC comprises the following steps:

[0044] S101: receiving an intermediate frequency signal, performing analog-to-digital conversion on the intermediate frequency signal, and obtaining a digital intermediate frequency signal, wherein the intermediate frequency signal is received by using a superheterodyne architecture;

[0045] The receiver is a superheterodyne architecture with a large instantaneous bandwidth (BW ≥ fs / 10). The receiver uses CIC extraction to reduce the signal bandwidth to obtain different signal bandwidths BW, and uses a fixed-point FFT for spectrum analysis to obtain the required resolution bandwidth.

[0046] like Figure 2 , a method for suppressing nonlinear spurious signals of a broadband receiver ADC, characterized in that: the receiver is in a default state when it is powered on or the intermediate frequency bandwidth is set by software>f s / 32, in broadband instantaneous bandwidth, input signal frequency is f in , after frequency conversion (one or more times, here we use one down-conversion as an example), the local oscillator frequency is f lo1 The center frequency of the intermediate frequency is f if1 , satisfying the equation:

[0047] f if1 =f in -f lo1

[0048] f if1 -f nco1 =0

[0049] After analog-to-digital conversion, when digital down-conversion is performed to move the signal to baseband, the frequency of the NCO is f nco1 ; At this time, f if1 =f s *3 / 4, f nco1 =f s *1 / 4, at this time the receiver can obtain the theoretical maximum instantaneous bandwidth BW (max)=f s *1 / 2 (the actual bandwidth is smaller than the theoretical value, and the bandwidth is reduced by the existence of the filter BPF);

[0050] S102: using CIC extraction to reduce the signal bandwidth of the digital intermediate frequency signal to obtain different signal bandwidths BW, and using fixed-point FFT to perform spectrum analysis on the different signal bandwidths BW to obtain a resolution bandwidth.

[0051] When the receiver software sets the IF bandwidth ≤ f s / 32, in the narrow instantaneous bandwidth, adjust the local oscillator frequency to f lo2 , where the center frequency is f if2 , the frequency of the NCO in the digital down-conversion is f nco2 , the tuning equation is:

[0052] f if2 =f in -f lo2

[0053] f if2 -f nco2 =0

[0054] Under narrow instantaneous bandwidth, the above intermediate frequency offset satisfies the following condition f s / 32≤|f lo2 -f lo1 |=|f if2 -f if1 |=|f nco1 -f nco2 |≤1.8*f s / 32, and the intermediate frequency bandwidth is ≤fs / 32, so a relatively clean spectrum can be obtained (see Figure 6 ), to achieve the purpose of ADC nonlinear spurious suppression.

[0055] Second, as Figure 7 As shown, in order to achieve the above-mentioned purpose, the present invention discloses a broadband receiver ADC nonlinear spurious suppression device, comprising:

[0056] The signal receiving module 11 is used to receive an intermediate frequency signal and perform analog-to-digital conversion on the intermediate frequency signal to obtain a digital intermediate frequency signal, wherein the intermediate frequency signal is received by a superheterodyne receiver;

[0057] The spectrum analysis module 12 is used to reduce the signal bandwidth of the digital intermediate frequency signal by using CIC extraction to obtain different signal bandwidths BW, and to perform spectrum analysis on different signal bandwidths BW by using fixed-point FFT to obtain resolution bandwidth.

[0058] In combination with the second aspect, in some implementations of the second aspect, the device further includes: the intermediate frequency signal input signal frequency of the signal receiving module is f in , the local oscillator frequency is f lo1 , after frequency conversion, the intermediate frequency center frequency is f if1 , the tuning equation is:

[0059] f if1 =f in -f lo1

[0060] f if1 -f nco1 =0

[0061] After the analog-to-digital conversion, the digital down-conversion is performed to move the signal to the baseband. The frequency of the NCO is f nco1 ; At this time, f if1 =f s *3 / 4, f nco1 =f s *1 / 4.

[0062] In combination with the second aspect, in some implementations of the second aspect, the device further includes: the maximum instantaneous bandwidth obtained by the superheterodyne architecture is: BW (max) =f s *1 / 2.

[0063] In combination with the second aspect, in some implementations of the second aspect, the device further includes: in a narrow-band instantaneous bandwidth, adjusting the local oscillator frequency to f lo2 , where the center frequency is f if2 , the frequency of the NCO in the digital down-conversion is f nco2 , the tuning equation is:

[0064] f if2 =f in -f lo2

[0065] f if2 -f nco2 =0.

[0066] In combination with the second aspect, in some implementations of the second aspect, the device further includes: under the narrowband instantaneous bandwidth, the intermediate frequency center frequency offset f s / 32≤|f lo2 -f lo1 |=|f if2 -f if1 |=|f nco1 -f nco2 |≤1.8*f s / 32, and the intermediate frequency bandwidth at this time is ≤fs / 32.

[0067] Embodiment 3: In a third aspect, in order to achieve the above-mentioned object, the present invention discloses a broadband receiver ADC nonlinear spurious suppression device, comprising:

[0068] The RF front end adopts a superheterodyne receiver architecture to output a broadband analog intermediate frequency signal;

[0069] High-speed analog-to-digital conversion circuit to realize the digitization of broadband analog intermediate frequency signals;

[0070] The signal analysis module uses CIC extraction to reduce the signal bandwidth of the digital intermediate frequency signal to obtain different signal bandwidths BW, and uses fixed-point FFT to perform spectrum analysis on different signal bandwidths BW to obtain the corresponding resolution bandwidth RBW.

[0071] In combination with the second aspect, in some implementations of the second aspect, the device further includes: the frequency of the intermediate frequency signal input signal of the RF front-end module is f in , the local oscillator frequency is f lo , after frequency conversion, the intermediate frequency center frequency is f if , the tuning equation is:

[0072] f if =f in -f lo

[0073] The ADC sampling rate in the high-speed analog-to-digital conversion circuit is f s ; In the signal analysis module, the frequency of the digital down-conversion NCO is f nco . And satisfy the following tuning equation:

[0074] f if -f nco =0

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0076] The above shows and describes the basic principles, main features and advantages of the present disclosure. Those skilled in the art should understand that the present disclosure is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present disclosure. Without departing from the spirit and scope of the present disclosure, the present disclosure may have various changes and improvements, and these changes and improvements fall within the scope of the present disclosure to be protected.

Claims

1. A method for suppressing nonlinear spurious signals in a broadband receiver ADC, characterized in that: The method comprises the following steps: Receiving an intermediate frequency signal, performing analog-to-digital conversion on the intermediate frequency signal, and obtaining a digital intermediate frequency signal, wherein the intermediate frequency signal is received using a superheterodyne architecture; The digital intermediate frequency signal is subjected to CIC extraction to reduce the signal bandwidth, and different signal bandwidths BW are obtained. A fixed-point FFT is used to perform spectrum analysis on different signal bandwidths BW to obtain the corresponding resolution bandwidth.

2. A method for suppressing nonlinear spurious signals in a broadband receiver ADC according to claim 1, characterized in that: The intermediate frequency signal has a broadband instantaneous bandwidth and an input signal frequency of f in , the local oscillator frequency is f lo1 , after frequency conversion, the intermediate frequency center frequency is f if1 , the tuning equation is: f if1 =f in -f lo1 f if1 -f nco1 =0 After the analog-to-digital conversion, the digital down-conversion is performed to move the signal to the baseband. The frequency of the NCO is f nco1 ; At this time, f if1 =f s *3 / 4, f nco1 =f s *1 / 4.

3. The method for suppressing nonlinear spurious signals of a broadband receiver ADC according to claim 1, wherein: The maximum instantaneous bandwidth obtained by the superheterodyne architecture is: BW (max) =f s *1 / 2.

4. The method for suppressing nonlinear spurious signals of a broadband receiver ADC according to claim 2, wherein: In the narrow instantaneous bandwidth, adjust the local oscillator frequency to f lo2 , where the center frequency is f if2 , the frequency of the NCO in the digital down-conversion is f nco2 , the tuning equation is: f if2 =f in -f lo2 f if2 -f nco2 =0。 5. A method for suppressing nonlinear spurious signals of a broadband receiver ADC according to claim 4, characterized in that: Under the narrowband instantaneous bandwidth, the intermediate frequency center frequency offset f s / 32≤|f lo2 -f lo1 |=|f if2 -f if1 |=|f nco1 -f nco2 |≤1.8*f s / 32, and the intermediate frequency bandwidth at this time is ≤fs / 32.

6. A broadband receiver ADC nonlinear spurious suppression device, characterized in that: include: A signal receiving module is used to receive an intermediate frequency signal, perform analog-to-digital conversion on the intermediate frequency signal, and obtain a digital intermediate frequency signal, wherein the intermediate frequency signal is received using a superheterodyne architecture; The spectrum analysis module is used to reduce the signal bandwidth of the digital intermediate frequency signal by using CIC extraction to obtain different signal bandwidths BW, and use fixed-point FFT to perform spectrum analysis on different signal bandwidths BW to obtain corresponding resolution bandwidths.

7. The broadband receiver ADC nonlinear spurious suppression device according to claim 6, characterized in that: The intermediate frequency signal input signal frequency of the signal receiving module is f in , the local oscillator frequency is f lo1 , after frequency conversion, the intermediate frequency center frequency is f if1 , the tuning equation is: f if1 =f in -f lo1 f if1 -f nco1 =0 After the analog-to-digital conversion, the digital down-conversion is performed to move the signal to the baseband. The frequency of the NCO is f nco1 ; At this time, f if1 =f s *3 / 4, f nco1 =f s *1 / 4.

8. The broadband receiver ADC nonlinear spurious suppression device according to claim 6, characterized in that: The maximum instantaneous bandwidth obtained by the superheterodyne architecture is: BW (max) =f s *1 / 2.

9. The broadband receiver ADC nonlinear spurious suppression device according to claim 7, characterized in that: In the narrow instantaneous bandwidth, adjust the local oscillator frequency to f lo2 , where the center frequency is f if2 , the frequency of the NCO in the digital down-conversion is f nco2 , the tuning equation is: f if2 =f in -f lo2 f if2 -f nco2 =0。 10. The broadband receiver ADC nonlinear spurious suppression device according to claim 9, characterized in that: Under the narrowband instantaneous bandwidth, the intermediate frequency center frequency offset f s / 32≤|f lo2 -f lo1 |=|f if2 -f if1 |=|f nco1 -f nco2 |≤1.8*f s / 32, and the intermediate frequency bandwidth at this time is ≤fs / 32.

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