Broadband signal generator

Abstract

Provided is a broadband signal generator. The broadband signal generator has: one or more digital-to-analog converters (DACs), each of the one or more DACs having one or more pipes and a sampling rate; a multiplexer for receiving the analog output from at least two pipes from the one or more DACs and multiplexing the analog output and zero into an output stream; the band-pass filter is used for receiving the output stream, filtering frequency components outside a target frequency band in the output stream and generating a radio frequency (RF) output signal in the target frequency band; and one or more processors configured to execute the code, the code causing the one or more processors to generate digital samples and transmit the digital samples to the one or more DACs, the generated digital samples being used to generate an analog output that matches the RF output signal to a target RF band.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present disclosure is a non-provisional application of and claims the benefit of U.S. Provisional Application No. 63 / 513,102, filed on July 11, 2023, entitled “WIDEBAND SIGNAL GENERATOR,” the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to test and measurement instruments, and more particularly to wideband signal generators. Background Art

[0004] High-speed signaling continues to evolve to higher speeds for wired and wireless communications. For example, 400Gb (Gigabit) and 800Gb Ethernet are being deployed and developed for data centers and to support wireless communications as "backhaul". 5G wireless is being deployed, and 6G wireless is being developed. Both 5G and 6G are exploring high-frequency bands. For example, 5G wireless explores the millimeter wave bands between 24GHz and 300GHz. Wireless 6G explores both millimeter wave and sub-THz (terahertz). The radio frequency (RF) range of the signal generator needs to reach 100GHz and above.

[0005] like Figure 1 As shown in FIG. 1 , a mobile unit 10 communicates with a base station 12 via an over-the-air wireless channel 14. The base station 12 is connected to a server 16 via a wired channel 18 (e.g., an optical cable). To achieve transmission frequencies of 100 GHz and above, current signal generators typically use mixers to up-convert baseband signals from arbitrary waveform generators (AWGs) to RF bands, such as Figure 2 As shown in Figure 2 In FIG. 1 , the signal generator includes an AWG 20 to generate a baseband signal, and a mixer 22 up-converts it to an RF band. A filter 24 shapes the signal to ensure that the signal in the target RF band is retained and out-of-band signals are removed. The signal generator needs to adjust the mixing signal to different frequencies for different target RF bands. The signal generator usually uses multi-stage mixing to generate a target RF signal at a higher frequency band with a wider instantaneous bandwidth (IBW). BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 A diagram showing wired and wireless systems for 5G / 6G wireless.

[0007] Figure 2 A diagram of a conventional radio frequency (RF) signal generator is shown.

[0008] Figure 3An embodiment of a wideband signal generator (WSG) according to an embodiment of the present disclosure is shown.

[0009] Figure 4 An embodiment of a pipeline sampling time arrangement is shown.

[0010] Figure 5 An embodiment of a bandpass filter bandwidth constraint is shown.

[0011] Figure 6 An example of input and output for the WSG algorithm is shown.

[0012] Figure 7 A diagram showing conditions for a first frequency range of the RF band is shown.

[0013] Figure 8 A diagram showing conditions for a second frequency range of the RF band is shown.

[0014] Fig. 9 A graph showing the frequency spectrum of samples from a first frequency range case.

[0015] Fig.10 A graph showing the frequency spectrum of samples from a second frequency range case.

[0016] Fig.11 A frame showing a simulated WSG showing the high RF frequency range is shown.

[0017] Fig.12 A two tone frame of an analog WSG with tones at a single tone in separate DAC pipes is shown.

[0018] Fig.13 A frame showing a simulated WSG with a tone at DC is shown. DETAILED DESCRIPTION

[0019] The embodiments herein describe a new instrument called a wideband signal generator (WSG) that uses a multiplexer and a bandpass filter along with a pair of digital-to-analog converters (DACs) to generate a wideband RF signal. The traditional mixer approach requires adjusting the frequency of the mixing signal to cover different RF bands. In contrast, the multiplexer in the WSG operates at a fixed rate. The WSG can be built with lower complexity, reducing cost and power consumption, resulting in more RF channels in a single instrument.

[0020] Figure 3A wideband signal generator (WSG) 30 according to an embodiment of the present disclosure is shown. One or more processors (such as 36) generate samples according to an algorithm. Memory 34 can load the samples created by the WSG algorithm into DAC 32, or processor 36 can load them into memory 34 or directly into DAC 32. Processor 36 can include one or more processors, including system processors, specific field programmable gate arrays (FPGAs), other DAC control processors, digital signal processors, among many others. As used herein, the term "one or more processors configured to execute code" includes configuring an FPGA to generate samples. Memory 34 and / or processor 36 need to have the ability to generate digital samples according to the algorithm and send them to the DAC.

[0021] Multiplexer 38 is used as Figure 3 The pattern shown in switches between two different DAC pipelines and zero. The two DAC pipelines can include two pipelines from a single DAC, or they can be from two separate DACs. The pipelines have delays and sampling periods, such as Figure 4 The output of the multiplexer has analog outputs in the following sequence:

[0022] …DAC0,DAC1,0,0,0,…,0,DAC0,DAC1,0,0,0,…,0,DAC0,DAC1,0,0,0,…

[0023] The specific implementation of WSG is designed based on the requirements of RF range and IBW. In WSG, the DAC pipeline delay and pipeline sampling rate are selected based on the following two conditions:

[0024] 1. The inverse of the DAC pipeline delay is more than twice the target RF range of the WSG.

[0025] 2. The DAC pipeline sampling rate is greater than the target IBW of the WSG.

[0026] For example, to obtain an RF range of 110 GHz and an IBW of 12.5 GHz, the pipeline delay is chosen to be 4 picoseconds (ps) and the pipeline sampling rate is f s = 15.625 Gigasamples / second (GS / s). This configuration in the WSG satisfies two conditions: 1 / (4ps) = 250GS / s > 220GHz (2x 110GHz), and 15.625GHz > 12.5GHz. In this case, the DAC pipeline sampling period is 64ps, or 16 times 4ps.

[0027] Figure 3 The filters in typically comprise bandpass (BP) filters and are selected based on the following criteria:

[0028] 1. The BP filter bandwidth is larger than the target bandwidth of the WSG and narrower than the pipeline sampling rate. BP filter passband Frequency band covering the frequencies of interest The frequency constraint is described in equation (1) and is Figure 5 Shown in.

[0029]

[0030] In this example, the BP filter bandwidth is between the bandwidth of the frequency of interest, 12.5 GHz, and the pipeline sampling rate, 15.625 GHz. According to various embodiments of the present disclosure, the BP filter may be fixed or tunable and may consist of a filter bank. A low pass (LP) filter is considered a special BP filter. The BP filter may be built into the instrument or added as an external accessory connected to the instrument output.

[0031] To generate the target RF signal, the WSG algorithm determines the samples of the two DAC pipelines, such as Figure 6 The goal of the WSG algorithm is to calculate the samples of the two DAC pipelines so that when the analog outputs from the two pipelines are multiplexed with 0, and then Figure 3 When filtered by the filter in the RF output, the RF output matches the target RF signal. As discussed above, one or more processors use algorithms to generate digital samples directly or through memory to send to the DAC pipeline. The digital samples are generated to match the RF output to the target RF signal.

[0032] exist Figure 6 Where f1 is the starting frequency that satisfies the BP filter constraints defined in equation (1). The WSG algorithm calculates the spectrum of the two DAC pipelines. The digital samples of the DAC pipelines can be obtained by performing IFFT on the spectrum determined by the WSG algorithm.

[0033] Figure 3 And formula (1) shows that only f1 and f1+f s The frequency components in the frequency band between f1 and f2 pass through the BP filter stage as the final RF output. The BP filter filters out other frequency components in the output of the multiplexer. The WSG algorithm only needs to ensure that f1 and f1+f s The spectrum of the frequency components in the frequency band between the two is matched with the spectrum of the target RF signal in the same frequency band.

[0034] For the WSG algorithm, there are two cases to consider. Figure 7 Case 1 is shown, where the starting frequency f1 is located at the sampling rate f s Integer multiples of f s Subtract the Nyquist frequency f Nyquist=f s / Between integer multiples of 2:

[0035] The WSG algorithm needs to consider two situations. Figure 7 Case 1 is shown, where the starting frequency f1 is located at the sampling rate f s Integer multiples of f s The integer multiple of the Nyquist frequency f Nyquist =f s / 2:

[0036] n·f s -f Nyquist ≤f1 <n·f s n is an integer (2)

[0037] Figure 8 Case 2 is shown, where the starting frequency f1 is located at the sampling rate f s Multiples of and f s multiples of the Nyquist frequency f Nyquist between:

[0038] n·f s ≤f1 <n·f s +f Nyquist n is an integer (3)

[0039] For Case 1 and Case 2, the DAC pipeline 0 and pipeline 1 digital samples determine the spectral components of the output RF signal. The spectral components of pipeline 0 and pipeline 1 determine Figure 7 and Figure 8 The frequency components shown in the figure are located between DC and f Nyquist Between, respectively Fig. 9 and Fig.10 as shown in .

[0040] For case 1, Figure 7 Around nf s The spectra X2 and X3 are given by Fig. 9 The DAC in pipe 0 and the lower frequency of pipe 1 are X low generate. Figure 7 Around n·f s +f Nyquist The spectrum X0, X1 is given by Fig. 9 The DAC in pipe 0 and pipe 1 have higher frequencies X high generate.

[0041] Using the following notation, you can see how the spectrum of each pipeline can be determined:

[0042] D: Delay from DAC pipeline 0 to pipeline 1.

[0043] P0: Spectrum of DAC pipeline 0 samples generated by the processor based on the target spectrum.

[0044] f DC and n·f s -f1. It is the lower frequency part of P0 between X low The pipeline 0 version.

[0045] n·f s -f1 and f Nyquist The higher frequency part of P0 between . It is X high The pipeline 0 version.

[0046] f low : The frequency of , which is a vector.

[0047] f high : The frequency of , which is a vector.

[0048] P1: Spectrum of DAC pipeline 1 samples generated by the processor based on the target spectrum.

[0049] f DC and n·f s -f1. It is the lower frequency part of P1 between X low The pipeline 1 version of .

[0050] n·f s -f1 and f Nyquist The higher frequency portion of P1 between high The pipeline 1 version of .

[0051] For case 1, Fig.10 The spectrum in and The solution can be derived as follows:

[0052]

[0053]

[0054]

[0055]

[0056] Fig.10 In and Can be exported as follows:

[0057]

[0058]

[0059]

[0060]

[0061] The solution to case 2 can be derived similarly to case 1.

[0062] Figure 11-13 Numerical examples are shown, each of which is a frame of an animated simulation of a two-tone signal sweep covering DC to 110 GHz, with the two tones 12.5 GHz apart. At each frequency setting, the WSG algorithm determines the DAC pipeline 0 and pipeline 1 spectra. The pipeline delay D = 4 ps, each DAC pipeline sampling rate f s =15.625GS / s. With the dual tone signal swept, both Case 1 and Case 2 are covered. The numerical example shows that the WSG supports an RF range from DC to 110 GHz and an IBW of 12.5 GHz.

[0063] Figure 11-13 Three frequency settings from a frequency sweep are shown in .

[0064] The spectrum of the two DAC pipelines is shown in f Nyquist As the boundary, f Nyquist It is shown as a vertical dashed line (such as 58) in the left sub-figure. Fig.11 In the frame shown in , the amplitude spectra of the two pipelines are different and the phases are different. The WSG algorithm determines the digital samples to be generated and sent to the two DAC pipelines. Figure 3 By using the multiplexer 38 and the filter 40 in the embodiment, the spectrum of the generated signal matches the spectrum of the target signal.

[0065] exist Fig.12 In the frequency setting shown in , both the amplitude and phase spectra of the two DAC pipelines are different. The spectrum of the generated signal matches the spectrum of the target RF signal.

[0066] Fig.13 The frequency settings shown in include DC.

[0067] Figure 2 The conventional mixer-based RF signal generator system shown in needs to adjust the frequency of the mixing signal to cover different RF frequency bands. In contrast, Figure 3The multiplexers in the WSG shown in FIG. operate at a fixed rate and fixed multiplexing sequence. The WSG can be built with lower complexity, reducing cost and power consumption, making it possible to support more RF channels in a single instrument. The WSG of an embodiment can be easily adjusted to different frequency bands desired by the user.

[0068] For 5G wireless and 6G wireless testing, it is desirable to have more RF channels in a single signal generator. Multiple-input multiple-output (MIMO) is a key enabling technology for 5G wireless and 6G wireless systems. Multiple RF signals from a single signal generator can be better synchronized than multiple RF signals from multiple independent signal generators. More RF channels also improve test throughput.

[0069] One consideration when choosing whether to use two DAC pipelines from one DAC or from different DACs is that using two DAC pipelines from one DAC can achieve better matching between the pipelines, as well as more accurate calibration and higher SFDR (spurious free dynamic range).

[0070] Embodiments herein describe a WSG that can be used to test wideband high frequency RF applications, such as 5G wireless and 6G wireless. The WSG has a simplified structure that uses multiplexers instead of mixers. The algorithm for the WSG determines the signal of the DAC based on the configuration of the WSG and the target RF signal. Numerical examples demonstrate accurate RF signal generation of the WSG. The WSG can operate at any target frequency band without having to make any adjustments to the mixing signal.

[0071] Aspects of the present disclosure may be operated on specially created hardware, on firmware, digital signal processors, or on a general-purpose computer including a processor that operates according to programming instructions. The term controller or processor as used herein is intended to include a microprocessor, a microcomputer, an application-specific integrated circuit (ASIC), and a dedicated hardware controller. One or more aspects of the present disclosure may be implemented with computer-usable data and computer-executable instructions (such as one or more program modules) executed by one or more computers (including monitoring modules) or other devices. Typically, a program module includes routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types when executed by a processor in a computer or other device. Computer-executable instructions may be stored on a non-temporary computer-readable medium, such as a hard disk, an optical disk, a removable storage medium, a solid-state memory, a random access memory (RAM), etc. As will be understood by those skilled in the art, the functions of the program modules may be combined or distributed as needed in various aspects. In addition, the functions may be implemented in whole or in part with firmware or hardware equivalents (such as integrated circuits, FPGAs, and the like). Certain data structures may be used to more efficiently implement one or more aspects of the present disclosure, and such data structures are considered to be within the scope of the computer-executable instructions and computer-usable data described herein.

[0072] In some cases, the disclosed aspects may be implemented in hardware, firmware, software, or any combination thereof. The disclosed aspects may also be implemented as instructions carried or stored on one or more or non-transitory computer-readable media, which may be read and executed by one or more processors. Such instructions may be referred to as computer program products. Computer-readable media as discussed herein means any medium that can be accessed by a computing device. As an example and not limitation, computer-readable media may include computer storage media and communication media.

[0073] Computer storage media means any medium that can be used to store computer-readable information. By way of example and not limitation, computer storage media may include RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital video disk (DVD) or other optical disk storage, cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, and any other volatile or non-volatile, removable or non-removable media implemented in any technology. Computer storage media excludes the signal itself and the transient form of signal transmission.

[0074] Communication media refers to any medium that can be used for communication of computer-readable information. By way of example and not limitation, communication media may include coaxial cables, fiber optic cables, air, or any other medium suitable for communication of electrical, optical, radio frequency (RF), infrared, acoustic, or other types of signals.

[0075] Example

[0076] Illustrative examples of the disclosed technology are provided below. Embodiments of the technology may include one or more of the examples described below and any combination thereof.

[0077] Example 1 is a broadband signal generator comprising: one or more digital-to-analog converters (DACs), each of the one or more DACs having one or more pipelines and a sampling rate; a multiplexer for receiving analog outputs from at least two pipelines from the one or more DACs and multiplexing the analog outputs and zeros into an output stream; a bandpass filter for receiving the output stream and filtering out frequency components in the output stream that are outside a target frequency band and generating a radio frequency (RF) output signal in the target frequency band; and one or more processors configured to execute code that causes the one or more processors to generate digital samples and transmit the digital samples to the one or more DACs, the generated digital samples being used to generate analog outputs that match the RF output signal to a target RF frequency band.

[0078] Example 2 is the broadband signal generator of Example 1, wherein the one or more DACs include one DAC, and the at least two pipelines are from the one DAC.

[0079] Example 3 is a broadband signal generator as in either of Example 1 or Example 2, wherein the one or more DACs include at least two DACs, and the at least two pipes include at least one pipe from each of the at least two DACs.

[0080] Example 4 is the broadband signal generator of any of Examples 1 to 3, wherein the one or more processors are configured to transmit the digital samples directly to the one or more DACs.

[0081] Example 5 is the broadband signal generator of any one of Examples 1 to 4, further comprising a memory.

[0082] Example 6 is the broadband signal generator of Example 5, wherein the one or more processors are configured to transfer the digital samples to a memory, and the memory transfers the digital samples to the one or more DACs.

[0083] Example 7 is the broadband signal generator of any one of Examples 1 to 6, wherein the bandpass filter has a bandwidth greater than a target bandwidth of the RF output signal and narrower than a sampling rate.

[0084] Example 8 is the broadband signal generator of any of Examples 1 to 7, wherein the code causing the one or more processors to generate the digital samples causes the one or more processors to use a starting frequency and a frequency spectrum of a target frequency band.

[0085] Example 9 is the broadband signal generator of Example 8, wherein the one or more processors are further configured to execute code that causes the one or more processors to set a pipeline delay in one or more DACs to be greater than twice the target RF frequency band and to set a sampling rate greater than an instantaneous bandwidth target of the broadband signal generator.

[0086] Example 10 is the broadband signal generator of Example 8, wherein the starting frequency is between a multiple of the sampling rate and a multiple of the sampling rate minus the Nyquist frequency.

[0087] Example 11 is the broadband signal generator of Example 8, wherein the starting frequency is between the sampling rate and a multiple of the sampling rate plus the Nyquist frequency.

[0088] Example 12 is a method for generating a broadband signal, comprising: using at least two pipelines from one or more digital-to-analog converters (DACs), each of the one or more DACs having one or more pipelines and a sampling rate to generate an analog output; multiplexing the analog outputs from the at least two pipelines and zeros to produce an output stream; filtering the output stream to remove frequency components in the output stream that are outside a target frequency band and produce a radio frequency (RF) output signal in the target frequency band; and generating digital samples, the generated digital samples matching the RF output signal to the target RF frequency band.

[0089] Example 13 is the method of Example 12, wherein filtering the output stream comprises filtering the output stream using a bandpass filter having a bandwidth greater than a target bandwidth of the RF output signal and narrower than a sampling rate.

[0090] Example 14 is the method of any of Examples 12 or 13, generating the digital samples comprises determining a frequency spectrum of the digital samples using the starting frequency and the frequency spectrum of the target frequency band.

[0091] Example 15 is the method of Example 14, further comprising setting a pipeline delay in one or more DACs to be greater than twice the target RF frequency band and setting a sampling rate to be greater than an instantaneous bandwidth target of the wideband signal generator.

[0092] Example 16 is the method of Example 14, wherein the starting frequency is between a multiple of the sampling rate and a multiple of the sampling rate minus the Nyquist frequency.

[0093] Example 17 is the method of Example 14, wherein the starting frequency is between the sampling rate and a multiple of the sampling rate plus the Nyquist frequency.

[0094] Example 18 is the method of any of Examples 12 to 17, wherein using at least two pipes comprises using at least two pipes from one DAC.

[0095] Example 19 is the method of any of Examples 12 to 17, wherein using at least two pipes comprises using one pipe from each of at least two DACs.

[0096] In addition, this written description refers to specific features. It is to be understood that the disclosure in this specification includes all possible combinations of those specific features. Where a specific feature is disclosed in the context of a particular aspect or example, the feature may also be used in the context of other aspects and examples to the extent possible.

[0097] Furthermore, when reference is made in the present application to a method having two or more defined steps or operations, the defined steps or operations may be performed in any order or simultaneously, unless the context excludes those possibilities.

[0098] All features disclosed in the specification including claims, abstract and drawings, and all steps in any method or process disclosed, may be combined in any combination except combinations in which at least some of such features and / or steps are mutually exclusive. Unless expressly stated otherwise, each feature disclosed in the specification including claims, abstract and drawings may be replaced by an alternative feature serving the same, equivalent or similar purpose.

[0099] Although specific examples of the present invention have been illustrated and described for purposes of illustration, it will be appreciated that various modifications may be made without departing from the spirit and scope of the present invention.Accordingly, the present invention should not be limited, except as by the appended claims.

Claims

1. A broadband signal generator, comprising: one or more digital-to-analog converters (DACs), each of the one or more DACs having one or more pipelines and a sampling rate; a multiplexer for receiving analog outputs from at least two pipelines from one or more DACs and multiplexing the analog outputs and zeros into an output stream; a bandpass filter for receiving the output stream and filtering out frequency components in the output stream that are outside a target frequency band, and generating a radio frequency (RF) output signal in the target frequency band; as well as One or more processors configured to execute code that causes the one or more processors to generate digital samples and transmit the digital samples to one or more DACs, the generated digital samples being used to produce analog outputs that match an RF output signal to a target RF frequency band.

2. The broadband signal generator of claim 1, wherein the one or more DACs include one DAC, and the at least two pipelines are from one DAC.

3. The broadband signal generator of claim 1, wherein the one or more DACs include at least two DACs, and the at least two pipes include at least one pipe from each of the at least two DACs.

4. The broadband signal generator of claim 1, wherein the one or more processors are configured to transmit digital samples directly to one or more DACs.

5. The broadband signal generator as claimed in claim 1, further comprising a memory.

6. The broadband signal generator of claim 5, wherein the one or more processors are configured to transfer the digital samples to a memory, and the memory transfers the digital samples to the one or more DACs.

7. The broadband signal generator as claimed in claim 1, wherein the bandpass filter has a bandwidth greater than a target bandwidth of the RF output signal and narrower than a sampling rate.

8. The wideband signal generator of claim 1, wherein the code that causes the one or more processors to generate the digital samples causes the one or more processors to use a starting frequency and a frequency spectrum of a target frequency band.

9. The wideband signal generator of claim 8, wherein the one or more processors are further configured to execute code that causes the one or more processors to set pipeline delays in the one or more DACs to be greater than twice the target RF frequency band and to set the sampling rate to be greater than the instantaneous bandwidth target of the wideband signal generator.

10. The broadband signal generator of claim 8, wherein the start frequency is between a multiple of the sampling rate and a multiple of the sampling rate minus the Nyquist frequency.

11. The broadband signal generator of claim 8, wherein the start frequency is between the sampling rate and a multiple of the sampling rate plus the Nyquist frequency.

12. A method for generating a broadband signal, comprising: using at least two pipelines from one or more digital-to-analog converters (DACs), each of the one or more DACs having one or more pipelines and a sampling rate to generate an analog output; multiplexing analog outputs and zeros from at least two pipelines to produce an output stream; filtering the output stream to remove frequency components in the output stream that are outside a target frequency band and to generate a radio frequency (RF) output signal in the target frequency band; as well as Digital samples are generated that match the RF output signal to a target RF frequency band.

13. The method of claim 12, wherein filtering the output stream comprises filtering the output stream using a bandpass filter having a bandwidth greater than a target bandwidth of the RF output signal and narrower than a sampling rate.

14. The method of claim 12, generating the digital samples comprises determining a frequency spectrum of the digital samples using a starting frequency and a frequency spectrum of a target frequency band.

15. The method of claim 14, further comprising setting a pipeline delay in one or more DACs to be greater than twice a target RF frequency band and setting a sampling rate to be greater than an instantaneous bandwidth target of a wideband signal generator.

16. The method of claim 14, wherein the starting frequency is between a multiple of the sampling rate and a multiple of the sampling rate minus the Nyquist frequency.

17. The method of claim 14, wherein the starting frequency is between the sampling rate and a multiple of the sampling rate plus the Nyquist frequency.

18. The method of claim 12, wherein using at least two pipes comprises using at least two pipes from one DAC.

19. The method of claim 12, wherein using at least two pipes comprises using one pipe from each of at least two DACs.

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