Signal generating device and wideband analog signal generating method

Abstract

To generate an analog signal with a wider bandwidth.SOLUTION: A signal generation device 10 includes a digital signal waveform generation unit 12 that generates a digital signal waveform. A low frequency (LF) signal path includes a low pass filter 16 that receives a digital signal waveform and passes a LF component of the digital signal waveform, and an LF DAC 22 that receives the LF component and generates an LF analog signal. A high frequency (HF) signal path includes a high pass filter 26 that receives a digital signal waveform and passes a HF component of the digital signal waveform, and a second DAC that receives the HF component and generates an HF analog signal. A mixing element 40 mixes the LF and HF analog signals to generate a wideband analog signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a signal generating apparatus and a method for generating a signal using multiple signal paths, and more particularly to a signal generating apparatus and a method for generating a wideband signal. [Background technology]

[0002] A wideband signal source generates a signal with spectral content ranging from DC and low frequencies to very high frequencies. High-speed serial standards such as PCIe (Peripheral Component Interface Express) and Ethernet require higher frequencies with each new version of the standard. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-183989 A Summary of the Invention [Problem to be solved by the invention]

[0004] Designing signal path components such as digital-to-analog converters (DACs) and amplifiers that span the full frequency range presents many challenges: components optimized for performance at high frequencies may not have optimal characteristics at low frequencies, and components that support a wide dynamic range at DC and low frequencies can be difficult to extend to also support wide bandwidths.

[0005] SUMMARY OF THE DISCLOSED EMBODIMENTS OF THE DISCLOSURE Embodiments of the disclosed apparatus and methods address shortcomings in the prior art. [Means for solving the problem]

[0006] As described herein, embodiments of the present invention relate to a split signal path for a signal generator. A digital wideband signal generator generates a wideband signal. As used herein, "wideband" refers to a wideband signal ranging from a steady-state (i.e., DC) signal to frequencies in the gigahertz range. of This refers to signals that extend to very high frequencies such as

[0007] This embodiment splits the signal between at least two frequency bands, such as a low frequency band and a high frequency band, where the difference between the low frequency band and the high frequency band depends on the application for which the signal is generated. The system may have more than two frequency bands. In the case of the low frequency band, the low frequency band includes signals that extend to any lower frequency in addition to DC signals. The high frequency band includes signals that are higher in frequency than the signals in the low frequency band. The system may have more than two frequency bands.

[0008] Although the description herein describes the bands in terms of low and high frequency bands, no limitation of the bands to that particular embodiment is intended or necessarily implied. Splitting the signals into low and high frequency signals allows the design of components to be optimized for each signal range. For example, components in the high frequency signal path may be optimized for AC operation at high frequencies and bandwidths, while components in the low frequency signal path may be optimized for low frequency and DC signal content. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 illustrates an embodiment of an apparatus having a split signal path. [Diagram 2] FIG. 2 shows an embodiment of a filter response. [Diagram 3] FIG. 3 shows an embodiment of a filter response. [Figure 4] FIG. 4 shows an embodiment of a passive mixing element. [Diagram 5] FIG. 5 shows an embodiment of a passive mixing element. [Figure 6] FIG. 6 shows an embodiment of a passive mixing element. [Figure 7] FIG. 7 shows an embodiment of a passive mixing element. [Figure 8] Figure 8 shows an embodiment of a split path using a pattern memory. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] FIG. 1 shows a signal generating apparatus 10. As used herein, the term "apparatus" refers to a package that includes the necessary components. The apparatus can be configured in a variety of ways. For example, all of the elements of FIG. 1 may be included on a single digital signal processor. Alternatively, all of the elements of FIG. 1 may be included on a single digital signal processor, except for the signal generating section 12 and the low frequency digital-to-analog converter (DAC) 22. These components may be included in a package, such as an ASIC or DSP. of Similarly, the apparatus may be implemented, at least in part, as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like.

[0011] The signal generator 12 will typically include a digital signal waveform source. Optional channel correction filters 14 may remove signal performance issues to compensate for the characteristics of components in the signal paths common to the high and low frequency signal paths. Separate channel correction filters may be present in the low and high frequency paths. These filters may compensate for the characteristics of components on the signal paths including the high frequency signal path, the low frequency signal path, the common output signal through the output terminal of the signal source, and the desired transmitter equalization response for the channel following the output terminal of the signal source. For example, these filters may be pre-emphasis filters.

[0012] First the generated signal is split into two signal paths, each with a predetermined frequency range. In FIG. 1, low pass filter 16 isolates the low frequency components of the generated signal, allowing the low frequency path to operate on the low frequency components of the signal. It may also include a decimation filter 18, which down samples the signal so that the sample rate matches the bandwidth of the low frequency DAC 22. Decimation filter 18 may be implemented within low pass filter 16 by discarding samples until the desired sample rate suitable for the low frequency DAC 22 is reached.

[0013] Additionally, other components may be in the low frequency signal path, such as another optional channel correction filter 20. A low frequency DAC 22 then converts the low frequency components of the signal into a low frequency analog signal, which is finally mixed with the high frequency analog signal in a combining element 40 and then provided to an output pin or connector 42. Other components may also be included in the low frequency path, such as an optional amplifier 24.

[0014] Similar to the low frequency path, the high frequency path includes a high pass filter 26 that isolates high frequency signal components. This path may also include an optional channel correction filter 30. A high frequency DAC 32 converts the digital signal to a high frequency analog signal at a sample rate required to cover the frequency range of the high frequency DAC. The resulting high frequency analog signal is then mixed with the low frequency analog signal in a mixing element 40. The high frequency path may also include an optional amplifier 34.

[0015] In this way, each path can be optimized for a narrower band of signals, rather than deploying components that need to cover the entire frequency range in a wide band. For example, the low frequency path and the components in the low frequency path can be optimized for low frequency signals, including DC signals, and the high frequency path and the components in the high frequency path can be optimized for wide bandwidth AC signals.

[0016] The selection of the mixing element 40 may depend on the structure of the filters 16, 26. For example, the low-pass filter 16 and the high-pass filter 26 may be designed to have filter responses as shown in FIG. 2. The low-pass filter response 44 and the high-pass filter response 46 overlap. The crossover frequency 48 serves as a reference point because the cutoff transitions at 52 and 54 must be a certain "distance" from the crossover frequency so as not to affect the combined output frequency response. These responses are also LF (z)+H HF The low-pass and high-pass filters are designed to sum to one, with (z)=1. This eliminates the need for further equalization or analog filtering to compensate for the transition between both bands. In this case, both the low-pass and high-pass filters will have -6dB attenuation at the crossover frequency between the bands.

[0017] In contrast, Figure 3 has a significantly different shape of the filter response compared to the response in Figure 2. The crossover regions of the filters are much wider in Figure 3. In this embodiment, there is more overlap between the bands, and mixing elements or other analog signal path components must reduce the frequency range of the low and high frequency bands in the crossover regions that transition between the bands so that the output signal has a smooth response.

[0018] Figures 4-7 show different types of mixing elements 40: a diplexer (Figure 4); a bias tee (Figure 5); and two different resistive mixers (Figures 6 and 7). The low-pass filter 16 and high-pass filter 26 would typically be implemented in a digital signal processor (DSP) as mentioned above. There may also be analog filters used in the low and high frequency signal paths in combination with the DSP low-pass and high-pass filters.

[0019] Figure 4 shows an embodiment of a diplexer 60. The diplexer 60 has low-pass and high-pass filters inside, 62 and 64. It receives a high frequency analog signal 63 at the high-pass filter 62 and a low frequency analog signal 65 at the low-pass filter 64. These two filtered signals are then sent to a common junction 42. In this example, the filters have a response as shown in Figure 3 for the DSP filters, and the diplexer analog filter attenuates -6 dB at the crossover frequency between the bands to match the sum to 1. Diplexer style mixing elements 40 do not strictly require DSP filters, but their presence can have the effect of allowing the use of lower rate DACs by using DSP low pass filters to decimate and reduce the sample rate of low frequency bands, and DSP high pass filters to eliminate low frequency content in high sample rate DACs, allowing the design to optimize the performance of the output signal with respect to electro-migration, noise and other considerations.

[0020] Figure 5 shows a bias tee, an example of a discrete analog LC filter consisting of a capacitor 66 connected to the high frequency (HF) analog signal and an inductor 68 connected to the low frequency (LF) analog signal. This combiner would typically use DSP low pass and high pass filters with responses like those in Figure 2.

[0021] In FIG. 6, the mixing element 40 is comprised of a resistive network of resistors 70, 72, and 74. FIG. 7 shows the mixing element 40, referred to herein as a resistive bridge hybrid, and includes resistors 76, 78, and 80. Port P1 is an output port, such as connector 42, and P2 and P3 are either high or low frequency input ports, reversing the traditional approach of using this circuit as a power splitter / divider. Both of these resistive mixers (FIGS. 6 and 7) mix the signals across the entire frequency range. These resistive mixers would typically utilize DSP low pass and high pass filters with a response like FIG. 2. The insertion loss of both of these resistive mixers would be about -6 dB across the entire frequency range if the high and low frequency paths were balanced in power. However, this could be unbalanced, for example, with less insertion loss in the high frequency band path and more loss in the low frequency band path. This extra loss can be overcome by using more amplification before the resistive mixer. An embodiment similar to that shown in Figures 4 and 5 has minimal insertion loss.

[0022] It should be noted that Figure 7 shows an embodiment that utilizes differential signaling. The previous embodiments may all utilize differential signaling, and the embodiment of Figure 7 may also utilize single-ended signaling.

[0023] In addition to having a low-frequency path optimized for low-frequency and DC signals and a high-frequency path optimized for AC and high-frequency signals, the split-path architecture offers several other advantages. For example, the low-frequency signal path can support a larger gain and offset range compared to what the high-frequency path can support. The low-frequency DAC does not need to cover higher sample rates and frequencies, potentially resulting in higher resolution, improved linearity, and improved performance characteristics. The higher signal fidelity performance of the low-frequency signal path compared to what can be realistically implemented in the high-frequency signal path can improve several system performance characteristics of the resulting source output.

[0024] Depending on the mixer and filter selection, this approach may result in more complex circuitry and hardware than is desired. In some embodiments, a pattern memory may be used in place of certain components. For example, returning to FIG. 1, the signal generator 12 may be a pattern memory, which provides a digital output waveform that ultimately becomes the output analog signal. The pattern memory may also be implemented in the form of separate high-frequency and low-frequency pattern memories, one for each path before the filter. However, multiple pattern memories may be used in place of high-pass and low-pass filters if reduced circuit complexity is desired. An example of such an embodiment is shown in FIG. 8.

[0025] In FIG. 8, the waveforms and filters 90 are pre-calculated as data in software, eliminating the need for filters and waveform generation. In this embodiment, the pattern memory becomes the digital signal waveform generator and the high-pass and low-pass filters. The software pre-calculated data for waveform generation and filters is loaded into the low-frequency pattern memory 94 and the high-frequency pattern memory 96. The low-frequency DAC 22 and the high-frequency DAC 32 access the pattern memory according to the synchronization controller 92 to output the final high-frequency and low-frequency analog signals, which are mixed in the mixing element 40 and output at the pin or connector 42.

[0026] The preceding discussion has focused on two signal paths, a high frequency path and a low frequency path. However, as noted above, frequencies may be split into multiple paths. For example, it may be desirable to split the high frequency path described above into two to allow for optimization of components and more finely tuned structures for the "middle" frequency path. A limitation to two frequency bands is not intended, nor is it necessarily implied.

[0027] Working Example Examples of the disclosed technology are provided below. Embodiments of the technology may include one or more of the following examples, and any combination thereof.

[0028] Example 1 is a signal generating device comprising: a digital signal waveform generating unit that generates a digital signal waveform; a first frequency band signal path including a first frequency band filter that receives the digital signal waveform and passes a first frequency band component of the digital signal waveform; a first digital-to-analog converter that receives the first frequency band component of the digital signal waveform and generates a first frequency band analog signal; a second frequency band signal path including a second frequency band filter that receives the digital signal waveform and passes a second frequency band component of the digital signal waveform; a second digital-to-analog converter that receives the second frequency band component of the digital signal waveform and generates a second frequency band analog signal; and a mixing element that mixes the first frequency band analog signal and the second frequency band analog signal to generate a wideband analog signal.

[0029] A second embodiment is the signal generating device according to the first embodiment, further comprising an all-band correction filter between the digital signal waveform generating unit and the first frequency band signal path and the second frequency band signal path.

[0030] Example 3 is the signal generating device of any of Examples 1 or 2, further comprising a first frequency band channel correction filter between the first frequency band filter and the first digital-to-analog converter.

[0031] A fourth embodiment is the signal generating device according to any one of the first to third embodiments, further comprising a second frequency band channel correction filter between the second frequency band filter and the second digital-to-analog converter.

[0032] Example 5 is a signal generating device according to any one of Examples 1 to 4, wherein the first frequency band filter and the second frequency band filter have overlapping passbands and are implemented in a digital signal processor, and the mixing element is composed of a diplexer.

[0033] Example 6 is a signal generating device according to any one of Examples 1 to 5, wherein the first frequency band filter and the second frequency band filter include matched filters in a digital signal processor having a sum response of 1, and the mixing element is composed of a discrete analog filter.

[0034] Example 7 is a signal generating device according to any one of Examples 1 to 6, wherein the first frequency band filter and the second frequency band filter include matched filters in a digital signal processor whose combined response is 1, and the mixing element is composed of a bias tee.

[0035] Example 8 is a signal generating device according to any one of Examples 1 to 7, wherein the first frequency band filter and the second frequency band filter include matched filters in a digital signal processor having a sum response of 1, and the mixing element is composed of a resistive mixer or a bridge.

[0036] A ninth embodiment is the signal generating device according to any one of the first to eighth embodiments, wherein the first frequency band signal path is the first digital-to-analog converter. converter and the mixing element.

[0037] A tenth embodiment is the signal generating device according to any one of the first to ninth embodiments, wherein the second frequency band signal path is the second digital-to-analog converter. converter and the mixing element, an amplifier is provided.

[0038] An eleventh embodiment is a signal generating device according to any one of the first to tenth embodiments, wherein the first frequency Bandwidth The signal path is Digital to Analog Converter It has a down-sampling filter with the sampling rate set to support the bandwidth.

[0039] Example 12 is the signal generating device of Example 11, in which the first frequency band filter and the down-sampling filter are implemented in the same filter.

[0040] A thirteenth embodiment is the signal generating device according to any one of the first to eleventh embodiments, further comprising a third frequency band signal path.

[0041] Example 1 4 A signal generating device according to any one of the first to eleventh and thirteenth embodiments, wherein the first frequency band filter is constituted by a first pattern memory, and the second frequency band filter is constituted by a second pattern memory.

[0042] Example 15 is a method for generating a wideband analog signal, the method including: generating a digital waveform; dividing the digital waveform into at least a first frequency band signal and a second frequency band signal; converting the first frequency band signal into a first frequency band analog signal; and converting the second frequency band signal into a second frequency band analog signal. Bandwidth and mixing the first frequency band analog signal with the second frequency band analog signal to generate the wideband analog signal.

[0043] Example 16 is the method of example 15, further comprising: converting the digital waveform into the first frequency band signal and the above second frequency band signal the process of dividing the digital waveform into two components includes applying a first frequency band filter to the digital waveform to generate the first frequency band signal, and applying a second frequency band filter to the digital waveform to generate the second frequency band signal.

[0044] Example 17 is the method of example 15 or example 16, wherein the step of generating the digital waveform includes a step of accessing a pattern memory to read out the digital waveform.

[0045] Example 18 is a method according to any one of Examples 15 to 17, wherein the process of generating a digital waveform and the process of converting the first frequency band signal into a first frequency band analog signal include a process of accessing a first pattern memory to obtain the first frequency band analog signal, and the process of converting the second frequency band signal into a second frequency band analog signal includes a process of accessing a second pattern memory to obtain the second frequency band analog signal.

[0046] Example 19 is the method of example 18, further comprising synchronizing the process of accessing the first pattern memory and the process of accessing the second pattern memory.

[0047] Example 20 is the method of any of Examples 15 to 18, wherein the process of dividing the digital waveform into at least a first frequency band signal and a second frequency band signal includes a process of dividing the digital waveform into at least a third frequency band signal.

[0048] The above-described versions of the disclosed subject matter have many advantages that have been described or will be apparent to those of skill in the art. Nevertheless, not all of these advantages or features are required in every version of a disclosed device, system or method.

[0049] In addition, the description of this application refers to specific features. It should be understood that the disclosure herein includes all possible combinations of those specific features. When a particular feature is disclosed in the context of a particular aspect or embodiment, that feature can also be used in the context of other aspects and embodiments, to the extent possible.

[0050] Furthermore, when the application refers to a method having two or more defined steps or processes, those defined steps or processes may be performed in any order or simultaneously, unless the context precludes such a possibility.

[0051] Furthermore, the term "comprises" and its grammatical equivalents are used herein to indicate the optional presence of other components, features, steps, processes, operations, etc. For example, "comprising" components A, B, and C or "something which comprises" components A, B, and C may include only components A, B, and C, or may include components A, B, and C as well as one or more other components.

[0052] Although for convenience of illustration, specific embodiments of the invention have been illustrated and described, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, the invention should not be limited except as by the appended claims. [Explanation of symbols]

[0053] 10 Signal generation device 12 Signal Generation Unit 14 Optional Channel Correction Filters 16 Low-pass Filter 18 Decimation Filter 20 Optional Channel Correction Filters 22 Low frequency DAC 24 Optional Amplifiers 26 High Pass Filter 30 optional channel correction filters 32 High Frequency DAC 34 Optional Amplifier 40 Mixing element 42 Output pin or connector 60 Diplexer 62 Low-pass filter 63 High Frequency Analog Signals 64 High Pass Filter 65 Low Frequency Analog Signal 66 High Frequency Analog Signal Capacitor 68 Coil for low frequency analog signals 70 resistor 72 Resistor 74 Resistor 76 Resistor 78 Resistor 80 resistor 90 Software Waveform and Filter Data Generation Unit 92 Synchronous Controller 94 Low Frequency Memory 96 High Frequency Memory P1 output port P2 input port P3 input port

Claims

1. a digital signal waveform generating unit for generating a digital signal waveform; a first frequency band signal path including a first frequency band filter receiving the digital signal waveform and passing a first frequency band component of the digital signal waveform; a first digital-to-analog converter that receives the first frequency band components of the digital signal waveform and generates a first frequency band analog signal; a second frequency band signal path including a second frequency band filter receiving the digital signal waveform and passing a second frequency band component of the digital signal waveform; a second digital-to-analog converter that receives the second frequency band component of the digital signal waveform and produces a second frequency band analog signal; a mixing element for mixing the first frequency band analog signal and the second frequency band analog signal to generate a wideband analog signal; Equipped with A signal generating apparatus in which the mixing element is selected based on the frequency response of a crossover region of the first and second frequency band filters.

2. 2. The signal generating apparatus of claim 1, wherein the first frequency band filter and the second frequency band filter are implemented in a digital signal processor, and the mixing element includes a diplexer.

3. 2. The signal generating apparatus of claim 1, wherein the first frequency band filter and the second frequency band filter comprise matched filters having a sum response of unity in a digital signal processor, and the mixing element comprises a discrete analog filter.

4. 2. The signal generating apparatus of claim 1, wherein the first frequency band signal path includes a down-sampling filter having a sampling rate set to support a bandwidth of the first digital-to-analog converter.

5. 2. The signal generating apparatus of claim 1, wherein said first frequency band filter comprises a first pattern memory and said second frequency band filter comprises a second pattern memory.

6. 1. A method for generating a wideband analog signal, comprising: A process for generating a digital waveform; splitting the digital waveform into at least a first frequency band signal and a second frequency band signal; converting the first frequency band signal into a first frequency band analog signal; converting the second frequency band signal into a second frequency band analog signal; mixing said first frequency band analog signal with said second frequency band analog signal to generate said wideband analog signal; Equipped with splitting the digital waveform into the first frequency band signal and the second frequency band signal comprises applying a first frequency band filter to the digital waveform to generate the first frequency band signal, and applying a second frequency band filter to the digital waveform to generate the second frequency band signal; 13. A method for generating a wideband analog signal, wherein mixing the first frequency band analog signal with the second frequency band analog signal is performed by a mixing element selected based on the frequency responses of a crossover region of the first frequency band filter and the second frequency band filter.

7. 7. The method of claim 6, wherein generating the digital waveform comprises accessing a pattern memory to read out the digital waveform.

Images