A comb spectrum generator and a design method of input power conversion efficiency matching circuit

Abstract

The present application relates to the field of semiconductor, specifically relates to a kind of comb spectrum generator and the design method of input power conversion matching circuit, by setting input power conversion efficiency matching circuit between signal input end and nonlinear transmission circuit, using load pull Load-pull method to realize the best input power conversion efficiency matching under specific input frequency and target output frequency range, and, increase output matching circuit after nonlinear transmission circuit, improve the output power conversion efficiency of comb spectrum generator, so that the harmonic of specific input frequency signal of comb spectrum generator in target output frequency range has greater output power.

Description

Technical Field

[0001] This invention relates to the field of comb spectrum generator technology, and more specifically to a nonlinear transmission line (NLTL) comb spectrum generator that improves harmonic output power through narrowband high-power signal input matching. Background Technology

[0002] Nonlinear transmission lines (NLTLs) are typically inductor-capacitor (LC) ladder networks that include periodically loaded nonlinear elements, such as nonlinear inductors or capacitors. For example, the periodically loaded nonlinear capacitor in an NLTL can be a reverse-biased varactor diode or a Schottky diode. NLTLs are now widely used in device and system applications, including comb spectrum generators, time-domain reflectometers (TDRs), frequency synthesizers, frequency multipliers, high-speed sampling oscilloscopes, pulse generators, and more.

[0003] A comb spectrum generator is a type of harmonic signal generator whose output signal contains a series of harmonic components of the input signal, each with significant signal power. This output signal typically comprises a series of evenly spaced spectral components, making its spectrum resemble the teeth of a comb. Comb spectrum generators based on nonlinear transmission line technology have been shown to improve phase noise and expand the input power range.

[0004] When the input to a comb spectrum generator is a continuous wave signal with frequency f, the spectrum of the output signal is the integer harmonics n*f (n = 1, 2, 3...) of the input frequency f. Generally, as the value of the multiple n increases, the output power at the corresponding harmonic frequency decreases more. Achieving both a flat and high power spectrum in the output signal of a comb spectrum generator is challenging.

[0005] The inventors disclosed an NLTL comb spectrum generator in patent CN115940885A. The inductor-capacitor cascade network of NLTL has broadband characteristics and a wide input frequency range, for example, it has excellent input standing wave characteristics (S11 better than -10dB) in the input frequency range of 0.1 to 5.0 GHz. Therefore, this NLTL comb spectrum generator achieves broadband input and output impedance matching by coupling a bias circuit along the signal propagation path. However, this broadband input matching method is only suitable for impedance matching of small signals with low input power. Under the condition of high-power input signals at specific frequencies (e.g., input signal power higher than 15dBm), the harmonic output power of the output signal is low, and the output power conversion efficiency of existing NLTL comb spectrum generators needs further improvement. Summary of the Invention

[0006] One object of the present invention is to provide a comb spectrum generator that, by connecting an input power conversion efficiency matching circuit to the front end of a nonlinear transmission line (NLTL) circuit, can perform power conversion efficiency matching on high-power signals with large input power within a target input frequency range that is narrower than the frequency range of the NLTL circuit, thereby improving the power conversion efficiency at the target output frequency point or within the target output frequency range and increasing the harmonic output power.

[0007] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0008] A comb spectrum generator includes a nonlinear transmission line circuit connected between a signal input terminal and a signal output terminal, and an input power conversion efficiency matching circuit connected between the signal input terminal and the nonlinear transmission line circuit. The input power conversion efficiency matching circuit is used to modify the broadband matching performance of the nonlinear transmission line circuit, so that the input signal at a preset target input frequency point f0, or the input signal within a target input frequency range (f1, f2) including the frequency point f0, has a higher input power conversion efficiency at the target output frequency point or target output frequency range compared to a nonlinear transmission line circuit without the input power conversion efficiency matching circuit. The input power conversion efficiency refers to the degree to which the energy of the input signal entering the nonlinear transmission line circuit is effectively converted into harmonic output at the target output frequency point or target output frequency range. When the input signal power is constant, the higher the harmonic power output at the target output frequency point or target output frequency range, the higher the input power conversion efficiency.

[0009] Similar to existing technologies, the comb spectrum generator in this technical solution includes a nonlinear transmission line (NLTL) circuit disposed between the signal input terminal and the signal output terminal. The signal input terminal receives a high-power input signal with a power not less than 15 dBm. The NLTL circuit generates an output signal based on the high-power input signal, which is ultimately output through the signal output terminal. This output signal includes multiple harmonics of the high-power input signal. In one or more embodiments, the NLTL circuit can employ existing technologies, such as any of the periodic circuit structures disclosed in patent CN115940885A, which consist of multiple series inductors and parallel variable capacitors. The periodic circuit structure of the NLTL approximates the equivalent model of a transmission line, thus naturally possessing a wide input bandwidth.

[0010] Considering that when performing input matching over a wide frequency range, it is difficult to ensure sufficient harmonic output power for high-power signals input within a narrower target input frequency range, this technical solution, unlike existing technologies, also includes an input power conversion efficiency matching circuit connected between the signal input terminal and the nonlinear transmission circuit. This circuit alters the broadband matching performance of the nonlinear transmission line circuit, ensuring that the input signal at the preset target input frequency point f0, or the input signal within the target input frequency range (f1, f2) including frequency point f0, has a higher input power conversion efficiency at the target output frequency point or target output frequency range compared to a nonlinear transmission line circuit without the input power conversion efficiency matching circuit.

[0011] The high-power input signal refers to an input signal with an input power of not less than 15dBm. In some preferred embodiments, the high-power input signal can be an input signal with a power greater than 18dBm. The high-power input signal has a target input frequency range f∈(f1, f2) that is narrower than the bandwidth of an NLTL circuit, where f1 and f2 are the lowest and highest frequencies containing frequency point f0, respectively.

[0012] Specifically, f1 and f2 are input frequency ranges with higher input power conversion efficiency compared to those without an input power conversion efficiency matching circuit, after input power conversion efficiency matching is performed based on the f0 value.

[0013] In some preferred embodiments, the bandwidth of the target input frequency range satisfies (f2-f1) / f0 ≤ 25%. For example, in one or more embodiments, f0 is any preset or specified frequency value, such as f0 being 850MHz, 1GHz, or 2GHz. In this case, the target input frequency range for inputting high-power signals is a frequency range that includes f0 (e.g., 1GHz) and still has higher input power conversion efficiency compared to NLTL circuits.

[0014] To design an input power conversion efficiency matching circuit, the equivalent input impedance of the nonlinear transmission line circuit needs to be simulated or measured at a preset input frequency f0. This invention plots an equivalent efficiency line cluster at the input end with different impedances to obtain the optimal input power conversion efficiency matching point. Based on this, an input power conversion efficiency matching circuit is configured to match the NLTL circuit to the optimal input power conversion efficiency matching point. This ensures that the input signal at the preset target input frequency f0, or the input signal within the target input frequency range (f1, f2) including frequency f0, has a higher input power conversion efficiency at the target output frequency or target output frequency range compared to a nonlinear transmission line circuit without the aforementioned input power conversion efficiency matching circuit. The design is carried out according to the following steps:

[0015] Step 1: Connect the signal input terminal to the signal source and the variable impedance device, wherein the variable impedance device has an impedance of a+bj, where a and b are variable parameters and j is the imaginary part.

[0016] Step 2: The signal source provides an input signal with a frequency of f0 and a value of not less than 15dBm.

[0017] Step 3: Change the value of a and / or the value of b, and obtain the output spectral power of the nonlinear transmission line circuit at the target output frequency point or the target output frequency range under different values ​​of a and b through actual measurement and / or simulation. Draw an iso-efficiency line cluster on the Smith chart based on the output spectral power.

[0018] Step 4: Select the center of the equal efficiency line cluster to obtain the optimal input power conversion efficiency matching point of the preset target frequency point f0;

[0019] Step 5: Set up an input power conversion efficiency matching circuit according to the optimal input power conversion efficiency matching point. Through the input power conversion efficiency matching circuit, match the equivalent input impedance of the nonlinear transmission line circuit to the optimal input power conversion efficiency matching point.

[0020] The setting of the input power conversion efficiency matching circuit according to the optimal input power conversion efficiency matching point means that the input power conversion efficiency matching circuit is designed according to the a and b values ​​corresponding to the optimal input power conversion efficiency matching point, so that the input power conversion efficiency matching circuit has an equivalent impedance value of a+bj, thereby matching the input conversion efficiency to the maximum value.

[0021] The above design steps draw on the load-pull theory used in traditional RF power amplifier design to explore a matching design method for the input power conversion efficiency matching circuit of the comb spectrum generator, which greatly improves the input power conversion efficiency of the comb spectrum generator.

[0022] In this technical solution, the input power conversion efficiency matching circuit obtained by the above design method is used to match the power conversion efficiency of high-power input signals within the target input frequency range. This reduces the echo reflection generated inside the comb spectrum generator after the high-power input signal is input within the target input frequency range, so that when the input frequency of the high-power input signal is within the target input frequency range, the high-power input signal can enter the nonlinear transmission line circuit with as little loss as possible, thereby effectively converting it into high-order harmonic output and improving the power conversion rate of the high-power input signal. Figure 1The diagram illustrates the S11 echo reflection in the Smith chart within an input frequency range of 100MHz to 5GHz. The blue dashed line represents the case without a power conversion efficiency matching circuit. Since NLTL circuits have a multi-stage LC structure, similar to a transmission line model, they naturally possess good broadband input matching. As shown by the blue dashed line, the frequency points S11 from 0.1 to 5GHz are all around the center of the Smith chart (this center represents the optimal impedance matching point at an input impedance of 50 ohms), meaning that existing comb spectrum generators can support a wider input frequency range. However, for a specific frequency point, its power conversion efficiency is not optimal. The red solid line represents the comb spectrum generator of this invention with the addition of a power conversion efficiency matching circuit. This circuit matches the input impedance of the target input frequency point f0 to the optimal input power conversion efficiency matching point (the center of the iso-efficiency line cluster in the Smith chart, representing the optimal efficiency matching point), thereby achieving the system's optimal power conversion efficiency. Multiple black dashed rings surrounding f0 represent multiple equiefficiency lines. The impedance points corresponding to each equiefficiency line have the same input-output power conversion efficiency. These equiefficiency lines together form an equiefficiency line cluster. The center of this cluster has the optimal input-output power conversion efficiency, with lower efficiency at points farther from the center. This invention introduces an input power conversion efficiency matching circuit to perform large-signal matching on the target input frequency f0 and the input signal within the target input frequency range (f1, f2) containing f0, thereby significantly improving the input-output power conversion efficiency within the target input frequency range f∈(f1, f2); in this example, f0 is 1 GHz. However, when the input frequency is much higher than f2 (e.g., higher than 2*f2) or much lower than f1 (e.g., lower than f1 / 2), due to the broadband characteristics of existing comb spectrum generators, their input-output power conversion efficiency may be superior to that of this invention.

[0023] In other words, by introducing an input power conversion efficiency matching circuit, this technical solution, despite sacrificing the wider input frequency bandwidth of the NLTL circuit, improves the "input-output" power conversion efficiency of the input high-power signal within a narrower target input frequency range, significantly improving the power conversion efficiency at the target output frequency point or within the target output frequency range.

[0024] In a preferred embodiment of the input power conversion efficiency matching circuit of the present invention, the input power conversion efficiency matching circuit includes an input series matching circuit, the input terminal of which is connected to the signal input terminal, and the output terminal of which is connected to a nonlinear transmission line circuit. The input series matching circuit includes at least one first inductor and at least one first capacitor connected in series with the first inductor.

[0025] In this technical solution, the input power conversion efficiency matching circuit includes an input series matching circuit, which is connected in series between the signal input terminal and the nonlinear transmission line circuit. The input series matching circuit includes at least a first inductor and a first capacitor, which are connected in series. In some embodiments, the input series matching circuit includes a first inductor and a first capacitor, wherein one end of the first capacitor is connected to the signal input terminal, the other end of the first capacitor is connected to the first inductor, and the first inductor is connected to the nonlinear transmission line circuit.

[0026] Furthermore, the bond wires at the input terminals should also be considered as equivalent inductance in the circuit. In one or more embodiments, the input series matching circuit includes more than one inductor to achieve power conversion efficiency matching for a specific target input frequency range.

[0027] As another preferred embodiment of the input power conversion efficiency matching circuit in this invention, the input power conversion efficiency matching circuit further includes an input parallel matching circuit. One end of the input parallel matching circuit is connected in parallel between the input series matching circuit and the nonlinear transmission line circuit, and the other end of the input parallel matching circuit is grounded. The input parallel matching circuit includes at least one second capacitor.

[0028] In this technical solution, the input power conversion efficiency matching circuit includes an input series matching circuit and an input parallel matching circuit. The input terminal of the input series matching circuit is connected to the signal input terminal, and the output terminal of the input series matching circuit is connected to the nonlinear transmission line circuit. One end of the input parallel matching circuit is connected in parallel between the series matching circuit and the nonlinear transmission line circuit, and the other end of the input parallel matching circuit is grounded.

[0029] In this technical solution, the input parallel matching circuit includes at least one second capacitor, which can be a variable capacitor, such as a varactor diode, or a combination of a fixed capacitor and a variable capacitor. In some preferred embodiments, the input parallel matching circuit includes one second capacitor. In one or more embodiments, the input parallel matching circuit may include multiple capacitors to achieve power conversion efficiency matching for a specific target input frequency range.

[0030] Another objective of this invention is to provide a comb spectrum generator, which connects an input power conversion efficiency matching circuit to the front end of an NLTL circuit to improve the input power conversion efficiency by matching the power conversion efficiency of a high-power input signal within a target input frequency range that is narrower than the input frequency bandwidth of the NLTL circuit. Simultaneously, it connects an output matching circuit to the rear end of the NLTL circuit to optimize the matching of the target output frequency range, reduce output return loss, and enable better output of harmonics within the target output frequency range, thereby further improving the harmonic output power.

[0031] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0032] An output matching circuit is provided between the nonlinear transmission line circuit and the signal output terminal. The output matching circuit is used for impedance matching of harmonics within the target output frequency range. Preferably, the target output frequency range is an output frequency specification set for the comb spectrum generator, which includes two or more consecutive harmonics of the input signal frequency.

[0033] In this technical solution, the input terminal of the output matching circuit is connected to the nonlinear transmission line circuit, and the output terminal of the output matching circuit is connected to the signal output terminal. The output matching circuit is used to optimize the matching of the target output frequency range, reduce output return loss, and enable harmonics within this frequency range to be output better, thereby further improving the harmonic output power. For example, when the input signal frequency of the comb spectrum generator is 1 GHz and the target output frequency range is 8–20 GHz (i.e., the 8th to 20th harmonics of 1 GHz), the output matching circuit is used to ensure that the harmonics within this target output frequency range are output with as little loss as possible.

[0034] In a preferred embodiment of the output matching circuit of the present invention, the output matching circuit includes an output series matching circuit and an output series-parallel matching circuit. One end of the output series-parallel matching circuit is connected between the nonlinear transmission line circuit and the output series matching circuit, and the other end of the output series-parallel matching circuit is grounded. The output series matching circuit includes at least one third inductor and at least one third capacitor, with the third capacitor connected in series with the third inductor. The output series-parallel matching circuit includes at least one fourth inductor and at least one fourth capacitor, with the fourth capacitor connected in parallel with the fourth inductor.

[0035] In this technical solution, the output series matching circuit and the output series-parallel matching circuit constitute a bandpass filter network, and the target output frequency range falls within the passband of this bandpass filter network. The output series matching circuit includes at least one third inductor and one third capacitor, with the third inductor and third capacitor connected in series. In some preferred embodiments, the output series matching circuit includes a third inductor and a third capacitor connected in series with the third inductor. One end of the third capacitor is connected to the output terminal of the output series-parallel matching circuit, and the other end of the third capacitor is connected to the third inductor. The third inductor is connected to the signal output terminal, wherein the third inductor is the bond wire equivalent inductance.

[0036] In this technical solution, the output series-parallel matching circuit includes at least a fourth inductor and a fourth capacitor. The fourth inductor is connected in series between the nonlinear transmission line circuit and the output series matching circuit. One end of the fourth capacitor is connected in parallel between the fourth inductor and the output series matching circuit, and the other end of the fourth capacitor is grounded. In some preferred embodiments, the output series-parallel matching circuit includes a fourth inductor and a fourth capacitor. In one or more embodiments, the fourth capacitor can be a variable capacitor, such as a varactor diode, or a combination of a fixed capacitor and a variable capacitor.

[0037] In this technical solution, the output matching circuit is used to ensure that the comb spectrum generator outputs within a wider target output frequency range, and that all harmonics within the wider target output frequency range have higher output power. In one or more embodiments, the output series matching circuit and / or the output series-parallel matching circuit may also include multiple capacitors and inductors to achieve output matching for the broadband target output frequency range.

[0038] Furthermore, the nonlinear transmission line circuit includes multiple nonlinear transmission line units connected in series. Each nonlinear transmission line unit includes a series inductor and a parallel variable capacitor connected in parallel to the series inductor. In some embodiments, all parallel variable capacitors in each nonlinear transmission line unit are coupled to the corresponding series inductor with the same polarity, for example, all of them are cathodes or all of them are anodes. In some embodiments, the parallel variable capacitors in adjacent nonlinear transmission line units are coupled to the corresponding series inductors with different polarities. For example, if the parallel variable capacitor in the preceding nonlinear transmission line unit is coupled to the series inductor with a cathode, then the parallel variable capacitor in the following nonlinear transmission line unit is coupled to the series inductor with an anode.

[0039] In some embodiments, the parallel variable capacitor is a varactor diode, a Schottky diode, or any type of PN junction diode.

[0040] Furthermore, in the direction from the signal input terminal to the signal output terminal, the inductance value of the series inductor of the preceding nonlinear transmission line unit is greater than or equal to the inductance value of the series inductor of the following nonlinear transmission line unit; and / or the reference capacitance value of the parallel variable capacitor of the preceding nonlinear transmission line unit is greater than or equal to the reference capacitance value of the parallel variable capacitor of the following nonlinear transmission line unit. The reference capacitance value of the variable capacitor is defined as the capacitance value of the variable capacitor under zero bias conditions.

[0041] In this technical solution, the greater the time compression of the input signal as it propagates along the nonlinear transmission line circuit, the richer the high-frequency harmonic components contained in the input signal. The series inductors and parallel variable capacitors of subsequent nonlinear transmission line units can have smaller inductance / capacitance values ​​to impedance match the gradually increasing harmonic components in the input signal, thereby giving the output signal better comb spectrum frequency components.

[0042] In a preferred embodiment of the nonlinear transmission line circuit of this invention, the number of stages of the nonlinear transmission line unit is configured such that when the number of stages of the nonlinear transmission line unit increases to N+1, the rate of increase of harmonic power within the target output frequency range is less than a preset value, then the number of stages of the nonlinear transmission line unit is determined to be N, where N is a positive integer greater than or equal to 2. The measurement of harmonic power includes, but is not limited to, summing, averaging, or weighting the power of multiple harmonics within the target input frequency range.

[0043] Generally, increasing the number of stages in a nonlinear transmission line can be more beneficial for the generation of high-frequency harmonic components; however, increasing the number of stages also leads to greater insertion loss. Therefore, the determination of the number of stages in the nonlinear transmission line of this invention is based on the target output frequency range of the output signal, which determines the number of nonlinear transmission line units in the NLTL circuit. This effectively balances the benefit of increasing the number of stages for generating high-frequency harmonic components with the losses caused by the increased number of stages, thus further improving the harmonic output power.

[0044] Specifically, after each increase in the number of stages of the nonlinear transmission line unit, the growth rate of the harmonic power in the target output frequency range compared to the harmonic power before the increase in stages can be obtained. If the growth rate is less than a preset value, the previous stage is used. Conversely, if the growth rate is greater than or equal to the preset value, it indicates that the current stage is effective, and the number of stages of the nonlinear transmission line unit can be increased again until the growth rate is less than the preset value.

[0045] Furthermore, the preset value of the growth rate is preferably 1% to 5%.

[0046] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0047] 1. This invention reduces the echo reflection generated inside the comb spectrum generator after a high-power signal is input within the target input frequency range by setting an input power conversion efficiency matching circuit at the front end of the nonlinear transmission line circuit. This allows the high-power input signal to enter the nonlinear transmission line circuit with as little loss as possible when the frequency of the high-power input signal is within the target input frequency range, thereby effectively converting it into higher harmonic output and improving the power conversion efficiency of the high-power input signal.

[0048] 2. By introducing an input power conversion efficiency matching circuit, this invention, although sacrificing the wider frequency bandwidth of the NLTL circuit, improves the "input-output" power conversion efficiency of the input high-power signal within a narrower target input frequency range, significantly improving the power conversion efficiency at the target output frequency point or within the target output frequency range.

[0049] 3. The present invention has an output matching circuit connected to the back end of the nonlinear transmission line circuit to optimize the matching of the target output frequency range, reduce the output return loss, and enable the harmonics in the target output frequency range to be output better, thereby further improving the harmonic output power.

[0050] 4. This invention determines the number of nonlinear transmission line units in the NLTL circuit based on the target output frequency range of the output signal, effectively balancing the influence of the number of unit stages on the benefits and losses of high-frequency harmonic components, which is beneficial to further improving the harmonic output power. Attached Figure Description

[0051] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0052] Figure 1 This is a comparison of S11 of the existing comb spectrum generator and S11 of the comb spectrum generator of the present invention in the Smith chart, and also includes a schematic diagram of the iso-efficiency line clusters.

[0053] Figure 2 In a specific embodiment of the present invention, a comb spectrum generator with an input series matching circuit is provided at the front end of the nonlinear transmission line circuit;

[0054] Figure 3 This refers to a nonlinear transmission line circuit in the prior art;

[0055] Figure 4 In a specific embodiment of the present invention, a comb spectrum generator is provided at the front end of the nonlinear transmission line circuit with an input series matching circuit and an input parallel matching circuit;

[0056] Figure 5 In a specific embodiment of the present invention, a comb spectrum generator is provided with an input power conversion efficiency matching circuit and an output matching circuit;

[0057] Figure 6 The following are the harmonic power test results of the output spectrum of the comb spectrum generator without input power conversion efficiency matching circuit and output matching circuit in specific embodiments of the present invention, and (b) the harmonic power test results of the output spectrum of the comb spectrum generator shown in Embodiment 4.

[0058] Figure 7This is a schematic diagram illustrating the implementation of input matching design based on load-pull theory in a specific embodiment of the present invention. Detailed Implementation

[0059] In the following description, specific details of the invention will be set forth to facilitate understanding of the invention. However, the invention may be practiced even without some or all of the specific details described. The embodiments of the invention described below may be incorporated into many different electrical components, circuits, devices, and systems. The structures and devices shown in the block diagrams of the accompanying drawings are used to illustrate exemplary embodiments of the invention, but are not intended to obscure the broad guidance of the invention. The connections between elements shown in the drawings are not limited to direct connections. Rather, the connections between elements can be modified, reconfigured, or otherwise altered through intermediate components.

[0060] In this invention, references to "one embodiment" or "a particular embodiment" indicate that a specific feature, structure, characteristic, or function related to the embodiment being discussed is included in at least one contemplated embodiment of the invention. Therefore, the phrase "in one embodiment" appearing in different places in the specification does not constitute multiple references to a single embodiment of the invention. Each reference or document mentioned in this patent document is incorporated herein by reference in its entirety. It should be noted that any examples provided herein are provided by way of illustration and are carried out under specific conditions using one or more specific embodiments; therefore, none of these examples should be used to limit the scope of disclosure of this patent document.

[0061] The terms "first," "second," etc., used in this invention (e.g., first capacitor, second capacitor, first inductor, second inductor, etc.) are merely for clarity of description and are not intended to restrict any order or emphasize importance. Furthermore, the term "connection" used in this invention, unless otherwise specified, can refer to a direct connection or an indirect connection via other components.

[0062]

Example 1

[0063] like Figure 2 The comb spectrum generator 20 shown includes a nonlinear transmission line circuit NLTL 22 connected between a signal input terminal RFin and a signal output terminal RFout, and an input power conversion efficiency matching circuit 21 connected between the signal input terminal and the nonlinear transmission line circuit. The input power conversion efficiency matching circuit 21 includes an input series matching circuit 211, which includes an inductor L4 connected to the signal input terminal, a first inductor L1 connected to the NLTL, and a first capacitor C1 connected between the two inductors.

[0064] In some embodiments, inductor L4 is the bonding wire equivalent inductance.

[0065] The input power conversion efficiency matching circuit matches the high-power input signal within the target input frequency range, reducing the echo reflection generated inside the comb spectrum generator after the high-power input signal is within the target input frequency range. This allows the high-power input signal to enter the nonlinear transmission line circuit with as little loss as possible when the frequency of the high-power input signal is within the target input frequency range, thereby effectively converting it into higher harmonic output and improving the power conversion efficiency of the high-power input signal.

[0066] In one or more embodiments, a specified frequency f0 within the target input frequency range is the input frequency of the high-power signal received by the signal input terminal. Here, f0 can be any frequency value specified according to actual needs, for example, f0 is 850MHz, 1GHz, or 2GHz. (f1, f2) is the target input frequency range including frequency point f0. In some preferred embodiments, f0, the lowest frequency f1 of the target input frequency range, and the highest frequency f2 of the target input frequency range satisfy (f2-f1) / f0 ≤ 25%.

[0067] In some embodiments, when f0 is 1 GHz, the first capacitor C1 in the series matching circuit 211 can be 15 pF.

[0068] In one or more embodiments, the input series matching circuit 211 includes one or more inductors and capacitors to achieve power conversion efficiency matching for a specific frequency point or a specific narrowband frequency range.

[0069] In this embodiment, the NLTL 22 can employ any existing nonlinear transmission line circuit. In one or more embodiments, the NLTL 22 employs the periodic structure described in patent CN115940885A. Specifically, as Figure 3 As shown, the nonlinear transmission line circuit 310 includes multiple nonlinear transmission line units connected in series, such as 321, 322, etc., each unit including a series inductor L and a parallel variable capacitor D. Figure 3 As shown, the first segment 321 includes a first series inductor L1 and a first parallel variable capacitor D1 coupled to the first series inductor L1 at the first node B1; the second segment 322 includes a second series inductor L2 and a second parallel variable capacitor D2 coupled to the second series inductor L2 at the second node B2; ..., the Nth segment includes an Nth series inductor Ln and an Nth parallel variable capacitor Dn coupled to the Nth series inductor Ln at the Nth node Bn.

[0070] In some preferred embodiments, from the signal input terminal to the signal output terminal, the inductance value of the series inductor of the preceding nonlinear transmission line unit is greater than the inductance value of the series inductor of the following nonlinear transmission line unit; and / or the reference capacitance value of the parallel variable capacitor of the preceding nonlinear transmission line unit is greater than the reference capacitance value of the parallel variable capacitor of the following nonlinear transmission line unit. For example, the inductance value of the first series inductor L1 is greater than the inductance value of the second series inductor L2, and as another example, the reference capacitance value of the first parallel variable capacitor D1 is greater than the reference capacitance value of the second parallel variable capacitor D2.

[0071]

Example 2

[0072] Based on Example 1, such as Figure 4 The comb spectrum generator 40 shown includes a nonlinear transmission line circuit NLTL 42 connected between the signal input terminal RFin and the signal output terminal RFout. The NLTL 42 can be any nonlinear transmission circuit in the prior art. It also includes an input power conversion efficiency matching circuit 41 connected between the signal input terminal and the nonlinear transmission circuit. The input power conversion efficiency matching circuit 41 includes an input series matching circuit 411 and an input parallel matching circuit 412.

[0073] The input series matching circuit 411 includes a first inductor L1, an inductor L4, and a first capacitor C1. The inductor L4 is connected to the signal input terminal, the first end of the first capacitor C1 is connected to the inductor L4, the second end of the first capacitor C1 is connected to the first inductor L1, and the first inductor L1 is connected in series to the NLTL.

[0074] The input parallel matching circuit 412 includes a second capacitor C2, with one end of the second capacitor C2 connected to the input series matching circuit 411 and the other end of the second capacitor C2 grounded. In some preferred embodiments, the second capacitor C2 can be replaced by a variable capacitor, or a combination of a fixed capacitor and a variable capacitor.

[0075] In some embodiments, the input parallel matching circuit 412 may also be equipped with multiple capacitors to achieve power conversion efficiency matching for a specific frequency point or a specific narrowband frequency range.

[0076]

Example 3

[0077] Based on the above embodiments, such as Figure 5The comb spectrum generator 50 shown includes a nonlinear transmission line circuit NLTL 52 connected between the signal input terminal RFin and the signal output terminal RFout. The NLTL 52 can be any nonlinear transmission circuit in the prior art. It also includes an input power conversion efficiency matching circuit 51 connected between the signal input terminal and the nonlinear transmission circuit. The input power conversion efficiency matching circuit 51 includes an input series matching circuit 511 and an input parallel matching circuit 512.

[0078] The input series matching circuit 511 includes a first inductor L1, an inductor L4, and a first capacitor C1. The inductor L4 is connected to the signal input terminal, the first end of the first capacitor C1 is connected to the inductor L4, the second end of the first capacitor C1 is connected to the first inductor L1, and the first inductor L1 is connected in series to the NLTL.

[0079] The input parallel matching circuit 512 includes a second capacitor C2, with one end of the second capacitor C2 connected to the input series matching circuit 511 and the other end of the second capacitor C2 grounded. In some preferred embodiments, the second capacitor C2 can be replaced by a variable capacitor, or a combination of a fixed capacitor and a variable capacitor.

[0080] An output matching circuit 53 is further provided between the nonlinear transmission line circuit and the signal output terminal. The output matching circuit 53 includes an output series matching circuit 531 and an output series matching circuit 532, which together form a bandpass filter network. The output series matching circuit 531 includes a third inductor L3 and a third capacitor C3 connected in series. One end of the third capacitor C3 is connected to the output terminal of the output series-parallel matching circuit, and the other end is connected to the third inductor L3, which is connected to the signal output terminal RFout. The third inductor L3 is the equivalent inductance of the bond wire. In one or more embodiments, the positions of the third inductor L3 and the third capacitor C3 can be interchanged. The output series-parallel matching circuit 532 includes a fourth inductor L2 and a fourth capacitor C4. The fourth inductor L2 is connected in series between the nonlinear transmission line circuit NLTL and the output series matching circuit 531. One end of the fourth capacitor C4 is connected in parallel between the fourth inductor L2 and the output series matching circuit, and the other end of the fourth capacitor C4 is grounded. In one or more embodiments, the fourth capacitor C4 may be a variable capacitor, such as a varactor diode, or a combination of a fixed capacitor and a variable capacitor.

[0081] In this embodiment, the output matching circuit 53 is used to ensure that the comb spectrum generator outputs within a wider target output frequency range, which falls within the passband of the bandpass filter network, and that all harmonics within the wider target output frequency range have higher output power. In one or more embodiments, the output series matching circuit and / or the output series-parallel matching circuit may also include multiple capacitors and inductors to achieve output matching for the wideband target output frequency range.

[0082]

Example 4

[0083] Based on the above embodiments, the number of stages of NLTL is further optimized, and the number of nonlinear transmission line units in the NLTL circuit is determined according to the target output frequency range of the output signal.

[0084] Specifically, the number of stages of the nonlinear transmission line unit is configured such that when the number of stages of the nonlinear transmission line unit increases to N+1, the rate of increase of harmonic power in the target output frequency range is less than a preset value. The number of stages of the nonlinear transmission line unit is N, where N is a positive integer greater than or equal to 2.

[0085] For example, when the number of stages in the nonlinear transmission line unit is increased to 5, the harmonic power within the target output frequency range of the comb spectrum generator with a stage of 5 is obtained and compared with the harmonic power when the number of stages is 4. If the growth rate is greater than or equal to a preset value, the number of stages in the nonlinear transmission line unit can be increased to 6, and further judgment is made until the growth rate after increasing the number of stages is less than the preset value. By balancing the benefits of increasing the number of stages to high-frequency harmonic components and the losses caused by increasing the number of stages, it is beneficial to further improve the harmonic output power.

[0086] In some preferred embodiments, the preset value is 1% to 5%.

[0087]

Example 5

[0088] like Figure 6 (a) and Figure 6 (b) The harmonic power test results of the output spectrum of the comb spectrum generator 310 based on the prior art and the comb spectrum generator in Example 4 are shown respectively under the condition of a high-power signal with an input frequency of 1 GHz and an input power of 18 dBm. The comparison shows that the solution of the present invention has achieved a significant improvement in the harmonic power of the output spectrum, especially in the target output frequency range of 8 to 20 GHz, where the output power is improved by 8 to 10 dB.

[0089]

Example 6

[0090] This invention explores a design method that can significantly improve the input power conversion efficiency of a comb spectrum generator from the load-pull method used in traditional RF power amplifier design, and realizes the matching design of the input power conversion efficiency matching circuit.

[0091] As another embodiment of the present invention, drawing on the load-pull theory used in traditional RF power amplifier design, a design method for an input power conversion efficiency matching circuit of a comb spectrum generator is proposed. The comb spectrum generator includes a nonlinear transmission line circuit and an input power conversion efficiency matching circuit disposed between the signal input terminal and the nonlinear transmission line circuit. The input power conversion efficiency matching circuit is used to change the broadband matching performance of the nonlinear transmission line circuit, so that the input signal at a preset target input frequency point f0 or the input signal within a target input frequency range (f1, f2) including frequency point f0 has a higher input-output power conversion efficiency at the target output frequency point or target output frequency range compared to the nonlinear transmission line circuit without the input power conversion efficiency matching circuit. The design is carried out according to the following steps:

[0092] Step 1: Connect the signal input terminal to the signal source and the variable impedance device, wherein the variable impedance device has an impedance of a+bj, where a and b are variable parameters and j is the imaginary part.

[0093] Step 2: The signal source provides an input signal with a frequency of f0 and a value of not less than 15dBm.

[0094] Step 3: Change the value of a and / or the value of b, and obtain the output spectral power of the nonlinear transmission line circuit at the target output frequency point or the target output frequency range under different values ​​of a and b through simulation and / or actual measurement. Draw an iso-efficiency line cluster on the Smith chart based on the output spectral power.

[0095] Step 4: Select the center of the equal efficiency line cluster based on the equal efficiency line cluster to obtain the optimal input power conversion efficiency matching point of the preset target frequency point f0;

[0096] Step 5: Set up an input power conversion efficiency matching circuit according to the optimal input power conversion efficiency matching point. Through the input power conversion efficiency matching circuit, match the equivalent input impedance of the nonlinear transmission line circuit to the optimal input power conversion efficiency matching point.

[0097] Furthermore, the target input frequency range refers to the frequency range (f1, f2) that includes the target input frequency point f0, where f0 is any preset or specified frequency value, f1 is the lowest frequency in the target input frequency range, and f2 is the highest frequency in the target input frequency range.

[0098] like Figure 7 As shown, signal source 701 is connected to variable impedance device 702 (e.g., impedance tuner), variable impedance device is connected to nonlinear transmission line (NLTL) circuit 703, and the output terminal of NLTL circuit is connected to spectrum power measurement device 704. Equivalence line clusters are plotted based on the impedance of variable impedance device and the power of the output spectrum of nonlinear transmission line (NLTL).

[0099] In the specific implementation process, firstly, the input signal frequency f0 is specified, and a constant input signal power is set, for example, 20dBm input power. The impedance of the variable impedance device a+bj is continuously changed, and the values ​​of a and b are changed sequentially. For example, a is taken in a predetermined step between (0, 100), and b is taken in a predetermined step between (-100, 100). At this time, the spectrum of the nonlinear transmission line circuit output is observed and recorded using a spectrum power measurement device. Since the output spectrum of the NLTL is the nth harmonic of f0 (n is a positive integer greater than or equal to 1), the output power value is observed based on the target output frequency or target output frequency range. For example, if the input signal frequency f0 = 1GHz and the target output frequency is 10 times f0, i.e., 10GHz, the input efficiency conversion efficiency is evaluated using the power of the 10GHz spectrum. When the target output is a frequency range, for example, the frequency range of 8f0 to 20f0, certain spectrum lines within that frequency range are selected to observe the output power value. Alternatively, the average power value or weighted summation power value of the spectral lines within the target output frequency range can be calculated. In this case, the power value P corresponding to a+bj of the variable impedance device can be obtained. Groups of a and b with the same power value P are connected by a black dashed line on the Smith chart (e.g., ...). Figure 1 As shown, isoefficiency lines with the same P value can be obtained. This process is repeated until a cluster of isoefficiency lines is finally drawn.

[0100] Next, the center of the equiefficiency line cluster is selected based on the equiefficiency line cluster to obtain the optimal input power conversion efficiency matching point at the preset target frequency f0. Based on the a and b values ​​corresponding to the optimal input power conversion efficiency matching point, an input power conversion efficiency matching circuit is designed so that the input power conversion efficiency matching circuit has equivalent a and b values, thereby matching the equivalent input impedance of the nonlinear transmission line circuit to the optimal input power conversion efficiency matching point. Specifically, the input power conversion efficiency matching circuit is designed based on the a and b values ​​corresponding to the optimal input power conversion efficiency matching point to obtain the optimal input-output power conversion efficiency.

[0101] This innovative approach incorporates the load-pull theory, traditionally used in RF power amplifier design, into a design method for improving the input power conversion efficiency of comb spectrum generators, resulting in significant performance improvements.

[0102] Although matching at f0 yields the optimal conversion efficiency matching point, the target input frequency range (f1, f2) including frequency point f0 may still exhibit better input power conversion efficiency compared to the case without an input power conversion efficiency matching circuit. In this case, by appropriately extending f0 to the target input frequency range (f1, f2) including frequency point f0, better input power conversion efficiency can still be achieved within the target input frequency range (f1, f2).

[0103] The foregoing embodiments have described the invention to provide clarity and understanding, but are not intended to limit the invention to the precise forms disclosed. Various modifications within the scope of the appended claims and their equivalents are also possible.

[0104] Those skilled in the art should understand that the embodiments and examples described above are exemplary and not intended to limit the scope of protection of the present invention. All substitutions, enhancements, equivalents, combinations, and modifications that are obvious to those skilled in the art after reading the present invention specification and studying the accompanying drawings should fall within the true spirit and scope of protection of the present invention.

[0105] It should also be noted that the elements in each claim can be arranged in different ways, including various dependencies, structures, and combinations. For example, in some embodiments, the subject matter of each claim can be combined with other claims.

Claims

1. A comb spectrum generator, comprising a nonlinear transmission line circuit connected between a signal input terminal and a signal output terminal, characterized in that, It also includes an input power conversion efficiency matching circuit connected between the signal input terminal and the nonlinear transmission circuit. The input power conversion efficiency matching circuit is used to change the broadband matching performance of the nonlinear transmission line circuit, so that the input signal at the preset target input frequency point f0 or the input signal in the target input frequency range (f1, f2) including the frequency point f0 has a higher input power conversion efficiency at the target output frequency point or target output frequency range compared with the nonlinear transmission line circuit without the input power conversion efficiency matching circuit.

2. The comb spectrum generator according to claim 1, characterized in that, The input power conversion efficiency matching circuit includes an input series matching circuit, the input terminal of which is connected to the signal input terminal, and the output terminal of which is connected to a nonlinear transmission line circuit. The input series matching circuit includes at least one first inductor and at least one first capacitor connected in series with the first inductor.

3. The comb spectrum generator according to claim 2, characterized in that, The input power conversion efficiency matching circuit further includes an input parallel matching circuit. One end of the input parallel matching circuit is connected in parallel between the input series matching circuit and the nonlinear transmission line circuit, and the other end of the input parallel matching circuit is grounded. The input parallel matching circuit includes at least one second capacitor.

4. The comb spectrum generator according to claim 1, characterized in that, The input signal is a high-power signal with an input power of not less than 15dBm.

5. The comb spectrum generator according to any one of claims 1 to 4, characterized in that, An output matching circuit is provided between the nonlinear transmission line circuit and the signal output terminal. The output matching circuit is used to impedance match harmonics within the target output frequency range.

6. The comb spectrum generator according to claim 5, characterized in that, The target output frequency range includes two or more consecutive harmonics.

7. The comb spectrum generator according to claim 5, characterized in that, The output matching circuit includes an output series matching circuit and an output series-parallel matching circuit. One end of the output series-parallel matching circuit is connected between the nonlinear transmission line circuit and the output series matching circuit, and the other end of the output series-parallel matching circuit is grounded. The output series matching circuit includes at least one third inductor and at least one third capacitor, wherein the third capacitor is connected in series with the third inductor. The output serial-parallel matching circuit includes at least one fourth inductor and at least one fourth capacitor, with the fourth capacitor connected in parallel to the fourth inductor.

8. The comb spectrum generator according to claim 5, characterized in that, The nonlinear transmission line circuit includes multiple nonlinear transmission line units connected in series. Each nonlinear transmission line unit includes a series inductor and a parallel variable capacitor connected in parallel to the series inductor.

9. The comb spectrum generator according to claim 8, characterized in that, From the signal input terminal to the signal output terminal, the inductance value of the series inductor of the preceding nonlinear transmission line unit is greater than or equal to the inductance value of the series inductor of the following nonlinear transmission line unit; and / or the reference capacitance value of the parallel variable capacitor of the preceding nonlinear transmission line unit is greater than or equal to the reference capacitance value of the parallel variable capacitor of the following nonlinear transmission line unit.

10. The comb spectrum generator according to claim 8, characterized in that, The number of stages of the nonlinear transmission line unit is configured such that when the number of stages of the nonlinear transmission line unit increases to N+1, the rate of increase of harmonic power in the target output frequency range is less than a preset value, then the number of stages of the nonlinear transmission line unit is determined to be N, where N is a positive integer greater than or equal to 2.

11. A design method for an input power conversion efficiency matching circuit for a comb spectrum generator, characterized in that, The comb spectrum generator includes a nonlinear transmission line circuit and an input power conversion efficiency matching circuit disposed between the signal input terminal and the nonlinear transmission line circuit. The input power conversion efficiency matching circuit is used to change the broadband matching performance of the nonlinear transmission line circuit, so that the input signal at a preset target input frequency point f0 or the input signal within a target input frequency range (f1, f2) including the frequency point f0 has a higher input power conversion efficiency at the target output frequency point or target output frequency range compared to the nonlinear transmission line circuit without the input power conversion efficiency matching circuit. The design method includes the following steps: Step 1: Connect the signal input terminal to the signal source and the variable impedance device, wherein the variable impedance device has an impedance of a+bj, where a and b are variable parameters and j is the imaginary part. Step 2: The signal source provides an input signal with a frequency of f0 and a value of not less than 15dBm. Step 3: Change the value of a and / or the value of b, and obtain the output spectral power of the nonlinear transmission line circuit at the target output frequency point or the target output frequency range under different values ​​of a and b through actual measurement and / or simulation. Draw an iso-efficiency line cluster on the Smith chart based on the output spectral power. Step 4: Select the center of the equal efficiency line cluster to obtain the optimal input power conversion efficiency matching point of the preset target frequency point f0; Step 5: Set up an input power conversion efficiency matching circuit according to the optimal input power conversion efficiency matching point. Through the input power conversion efficiency matching circuit, match the equivalent input impedance of the nonlinear transmission line circuit to the optimal input power conversion efficiency matching point.

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