Nonlinear transmission line comb spectrum generator and frequency multiplier comprising the same

Abstract

Embodiments of a NLTL comb spectrum generator are disclosed to compress the rise time, fall time, or both rise and fall times of an input signal to produce an output signal containing harmonics of the input signal. The NLTL comb spectrum generator can include a plurality of segments connected in series, and each segment includes a series inductor, a shunt capacitor, and a reverse shunt capacitor to achieve balanced signal compression. The shunt capacitor and reverse shunt capacitor can be varactor diodes or Schottky diodes with voltage dependent capacitance. Ultimately, both the rise time and fall time of the input signal are compressed along the NLTL comb spectrum generator. For a sinusoidal input signal, the output signal approaches a square wave. This square wave output necessarily suppresses all even harmonics, which is beneficial for odd harmonic signal extraction or filtering.

Description

Technical Field

[0001] This invention relates generally to comb spectrum generators, and more specifically to an NLTL comb spectrum generator with even-order harmonic suppression. 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, an NLTL can be a periodically loaded reverse-biased varactor diode or a Schottky diode. NLTLs are currently 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 signal generator whose output signal has a series of harmonic components of the input signal, and each harmonic component has significant signal power. This output signal typically includes a series of evenly spaced spectral components, making the spectrum of the output signal resemble the teeth of a comb.

[0004] In some cases, it is desirable for the output signal power of a comb spectrum generator to be selectively focused on certain specific harmonic frequencies in order to extract or filter harmonics of interest. For NLTL-based multipliers, a high-Q bandpass filter (BPF) is needed to suppress harmonics near the desired passband. When the input oscillator signal of the NLTL-based multiplier has a low-frequency F... OSC At that time, selecting high Nth harmonics will become very difficult or extremely challenging.

[0005] Therefore, it is necessary to improve the NLTL comb spectrum generator to solve the above problems. Summary of the Invention

[0006] This invention provides an NLTL comb spectrum generator with even-order harmonic suppression. The embodiments disclosed in this invention provide better harmonic separation for signal filtering in application.

[0007] This invention discloses several embodiments of an NLTL comb generator for compressing the rise time, fall time, or both rise and fall times of an input signal so that the resulting output signal contains multiple harmonics of the input signal. The NLTL comb generator may include multiple segments connected in series, each segment including a series inductor, a parallel capacitor, and a reverse parallel capacitor to achieve balanced signal compression. The series inductor may be a transmission line inductor or a spiral inductor. The parallel and reverse parallel capacitors may be varactor diodes or Schottky diodes with capacitance varying with voltage, their capacitance decreasing as the reverse PN junction voltage bias increases. The cathode of the parallel varactor diode is coupled to the corresponding series inductor, while the anode of the reverse varactor diode is coupled to the corresponding series inductor. Ultimately, along the NLTL comb generator, both the rise time and fall time of the input signal are simultaneously compressed.

[0008] In one or more embodiments, the reference capacitance values ​​(capacitance values ​​at zero bias voltage) of the parallel and anti-parallel capacitors in multiple segments along the signal propagation path gradually decrease. Similarly, the inductance value of the series inductor gradually decreases along multiple segments along the signal propagation path. In other words, the reference capacitance of the parallel and anti-parallel capacitors in one segment is greater than the reference capacitance of the parallel and anti-parallel capacitors in the next segment along the signal propagation path.

[0009] The greater the time compression of the input signal as it propagates along the NLTL comb spectrum generator, the higher the content of its high-frequency harmonics. Subsequent series inductors, parallel capacitors, and anti-parallel capacitors may have smaller dimensions and inductance / capacitance values ​​to impedance match the gradually increasing harmonic components in the input signal, thereby resulting in a better comb spectrum frequency composition in the output signal.

[0010] In one or more embodiments, the reference capacitance values ​​of the parallel capacitors and anti-parallel capacitors in each segment can be different or the same. When the parallel capacitors and anti-parallel capacitors in each segment have the same capacitance value, the rise time and fall time of the input signal can be compressed simultaneously and symmetrically without increasing the size of the NLTL circuit. This characteristic is beneficial for circuit integration. For a sinusoidal input signal, the signal at the Nth node Cn (located in the series inductor of the Nth segment) is close to a square wave. This square wave output will necessarily suppress all even harmonics in the spectrum, which is beneficial for signal extraction or filtering.

[0011] Furthermore, all parallel and anti-parallel capacitors along the signal propagation path can be coupled to a DC bias voltage. The NLTL comb generator may further include a grounded parallel branch coupled to the signal propagation path to set the DC bias voltage of the parallel and anti-parallel capacitors to DC ground. The grounded parallel branch includes a series bias resistor and a series bias inductor to prevent signal propagation along the signal propagation path from leaking to DC ground via the grounded parallel branch. Alternatively, the NLTL comb generator may include a biased parallel branch coupled to a DC bias voltage Vbias, such that the DC bias voltage of the parallel and anti-parallel capacitors is set to the DC bias voltage Vbias, which may be preset or adjustable for harmonic distribution tuning of the NLTL output signal.

[0012] For the purpose of summarizing the invention, certain aspects and novel technical features of the invention have been described herein. Those skilled in the art will recognize that the various embodiments disclosed herein can be implemented through different arrangements, enhancements, equivalences, combinations, and improvements, and all such methods should fall within the protection scope of the invention. Attached Figure Description

[0013] The accompanying drawings illustrate exemplary embodiments of the invention for reference, and these drawings are intended to illustrate rather than limit the invention. While the invention has been generally described in the embodiments, this is not intended to limit the scope of the invention to the specific technical features of the described embodiments.

[0014] Figure 1 The equivalent circuit of NLTL in the prior art is shown;

[0015] Figure 2 The invention describes a low-noise frequency multiplier employing NLTL in one or more embodiments;

[0016] Figure 3 Time compression along the rising edge of the NLTL is described in one or more embodiments of the present invention;

[0017] Figure 4 Time compression along the falling edge of the NLTL comb spectrum generator is described in one or more embodiments of the present invention;

[0018] Figure 5 The invention describes time compression along the rising and falling edges of the NLTL comb spectrum generator in one or more embodiments;

[0019] Figure 6 The spectrum of the output signal of an NLTL comb generator that simultaneously compresses the rising and falling edge times in one or more embodiments of the present invention is shown.

[0020] Figure 7 This invention illustrates another NLTL comb spectrum generator that compresses the rise and fall times in one or more embodiments;

[0021] Figure 8 This invention illustrates yet another NLTL comb spectrum generator that compresses the rise and fall times in one or more embodiments;

[0022] Figure 9 The process of generating radio frequency harmonic signals in one or more embodiments of the present invention is described.

[0023] Those skilled in the art will recognize that various embodiments and examples of the invention can be implemented based on the specification. All such embodiments and examples should be included within the scope of protection of this invention. Detailed Implementation

[0024] 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.

[0025] References to "one embodiment" or "a particular embodiment" in the specification indicate that a specific feature, structure, characteristic, or function related to the embodiment under discussion 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.

[0026] NLTL (Neural Frequency Transmission) technology is now widely used in equipment and systems applications, including comb spectrum generators, time-domain reflectometers (TDRs), frequency synthesizers, frequency multipliers, high-speed sampling oscilloscopes, pulse generators, and more. A comb spectrum generator is a signal generator whose output signal contains a series of harmonic components of the input signal, each with significant signal power. This output signal typically consists of a series of evenly spaced spectral components, making the spectrum of the output signal resemble the teeth of a comb.

[0027] The phase velocity of a wave signal propagating in a nonlinear transmission line is:

[0028]

[0029] Where L is the inductance of the line, and C(V) is the nonlinear voltage-dependent capacitance affected by voltage. The nonlinear capacitance can be a varactor diode, a Schottky diode, or any type of PN junction diode, characterized by a decrease in junction capacitance as the reverse bias voltage of the PN junction increases. When the reverse voltage increases and the capacitance decreases, the propagation speed along the transmission line increases. As a result, the higher voltage components of the wave signal, such as peaks, will propagate faster and attempt to overtake the lower voltage components, thus forming a steep forward shock wave, the steepness of which is ultimately limited by the nonlinear transmission line dispersion rate.

[0030] The reduction in edge switching time of the NLTL signal can be calculated using the following formula:

[0031]

[0032] Where C0 is the zero-bias capacitor, C(V max Let C(V) be the capacitance under the peak bias of the reverse wave signal amplitude, and n be the number of segments in the NLTL. Among many different types of nonlinear capacitors, varactor diodes based on NLTLs are widely used because of their high C(V) capacitance. max The ratio of ) / C0 will significantly reduce the edge switching time of the wave signal.

[0033] US Patent 8,878,575B1 discloses an equivalent circuit for an NLTL 10, which has a periodic structure consisting of a series inductor 12 and a variable parallel capacitor 14, such as... Figure 1 As shown. The capacitance of the parallel capacitor 14 is voltage-dependent; for example, the capacitance under low reverse bias is significantly larger than that under high reverse bias. The propagation speed of the input signal 16 propagating on the equivalent transmission line is voltage-dependent. Since the initial low-voltage portion of the signal propagates along the transmission line more slowly than the subsequent high-voltage portion, the signal transitioning from low to high voltage is instantaneously compressed. Therefore, the high-voltage portion of the waveform "catches up" with the step-low voltage portion, resulting in an increased edge switching speed from low to high, i.e., an increased slew rate. This sharper rising-edge waveform produces an output signal 18 with a spectrum rich in signal harmonic components.

[0034]

Example 1

[0035] Figure 2 A low-noise frequency multiplier using NLTL is described. Oscillator 210 operates at a clock frequency F. OSCThe output signal is sent to the NLTL220, and the output signal generated by the NLTL220 includes a frequency of clock frequency F. OSC The bandpass filter (BPF) 230 receives the output signal from the NLTL 220 and outputs a harmonic signal of the desired frequency, such as the Nth harmonic. When the input oscillator signal of the NLTL-based multiplier has a low frequency F... OSC At a frequency of 100MHz, achieving higher harmonics, such as the 25th harmonic (2.5GHz), becomes difficult. The BPF would require a high Q-factor to suppress nearby harmonics; for example, the BPF's suppression level would need to exceed 40dB to suppress the 2.4GHz and 2.6GHz harmonics. Implementing such narrow-bandwidth (100MHz) suppression at a high center frequency (e.g., 2.5GHz) is extremely challenging.

[0036]

Example 2

[0037] Figure 3 Rising-edge time compression along the NLTL is described in one or more embodiments of the present invention. The NLTL 310 includes multiple segments in series, such as 321, 322, etc., each segment including a series inductor L and a parallel capacitor D with variable capacitance. Figure 3 As shown, the first segment 321 includes a first series inductor L1 and a first parallel capacitor D1 coupled to the first series inductor L1 at the first node A1; the second segment 322 includes a second series inductor L2 and a second parallel capacitor D2 coupled to the second series inductor L2 at the second node A2; ..., the Nth segment includes an Nth series inductor Ln and an Nth parallel capacitor Dn coupled to the Nth series inductor Ln at the Nth node An.

[0038] The input signal RFI of the NLTL 310 passes through multiple segments connected in series and is compressed in the signal propagation direction. The parallel capacitors D1, D2, ..., Dn can be varactor diodes (also called variable capacitor diodes or varactor tubes), which have voltage-dependent capacitance, decreasing as the reverse voltage increases. For example... Figure 3 In the illustrated embodiment, the cathode of the varactor diode is coupled to the corresponding series inductor. Therefore, as shown by the rising slope waveforms at nodes A1, A2, ..., An, the rise time or rise edge of the input signal RFI is compressed along the direction of the NLTL 310.

[0039] In one or more embodiments, the parallel capacitors of each segment may have the same reference capacitance (capacitance at zero bias), and the inductors of each segment may have the same inductance. Alternatively, along the signal propagation direction, the series inductance and parallel capacitor of each segment may have successively decreasing inductance and reference capacitance, respectively. The greater the time compression of the input signal as it propagates along the NLTL, the richer the high-frequency harmonic components contained in the input signal. Subsequent segments of series inductance and parallel capacitor may have smaller dimensions and inductance / capacitance values ​​to impedance match the gradually increasing harmonic components in the input signal, thereby giving the output signal RFout a better comb spectrum frequency component.

[0040]

Example 3

[0041] In some cases, it is necessary to compress the falling edge time of the input signal rather than the rising edge time. Figure 4 Time compression along the falling edge of an NLTL comb spectrum generator is described in one or more embodiments of the present invention. The NLTL comb spectrum generator 410 includes multiple segments connected in series, such as 421, 422, etc., each segment including a series inductor L and a parallel capacitor D with variable capacitance. Figure 4 As shown, the first segment 421 includes a first series inductor L1 and a first parallel capacitor D1 coupled to the first series inductor L1 at the first node B1; the second segment 422 includes a second series inductor L2 and a second parallel 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 capacitor Dn coupled to the Nth series inductor Ln at the Nth node Bn.

[0042] The parallel capacitors D1, D2, ..., Dn can be varactor diodes with voltage-dependent capacitance, whose capacitance decreases as the reverse voltage increases. For example... Figure 4 In the illustrated embodiment, the anode of the varactor diode is coupled to the corresponding series inductor. Therefore, as shown by the falling slope waveforms at nodes B1, B2, ..., Bn, the falling edge time or falling edge of the input signal RFI is compressed along the direction of the NLTL comb spectrum generator 410. In one or more embodiments, the series inductance and parallel capacitance of each segment have progressively decreasing inductance and reference capacitance along the signal propagation direction. The greater the time compression of the input signal as it propagates along the NLTL, the richer the high-frequency harmonic components contained in the input signal. Subsequent segments of series inductance and parallel capacitance may have smaller dimensions and inductance / capacitance values ​​to impedance match the progressively increasing frequency components of the input signal, thereby giving the output signal RFout better comb spectrum frequency components.

[0043]

Example 4

[0044] For balanced signal compression, it is necessary to compress both the rise time and fall time of the input signal simultaneously, rather than compressing the rise time or fall time separately. Figure 5 Compression along the rising and falling edges of an NLTL comb generator is illustrated in one or more embodiments of the present invention. The NLTL comb generator 510 includes multiple segments 521, 522, etc., connected in series. Each segment includes a series inductor L, a parallel capacitor D coupled to the series inductor, and a reverse parallel capacitor D'. The parallel capacitor D is coupled to the series inductor with a first polarity, and the reverse parallel capacitor D' is coupled to the series inductor with a second polarity opposite to the first polarity. The parallel capacitor and the reverse parallel capacitor may be varactor diodes with voltage-dependent capacitance, whose capacitance decreases as the reverse voltage increases. The series inductors in the multiple segments collectively form a signal propagation path 512 located between the input signal RFin and the output signal RFout.

[0045] like Figure 5 As shown, the first segment 521 includes a first series inductor L1, a first parallel capacitor D1 coupled to the first series inductor L1 at the first node C1, and a first anti-parallel capacitor D1' coupled to the first series inductor L1 at the first node C1; the second segment 522 includes a second series inductor L2, a second parallel capacitor D2 coupled to the second series inductor L2 at the second node C2, and a second anti-parallel capacitor D2' coupled to the second series inductor L2 at the second node C2; ​​..., the Nth segment includes an Nth series inductor Ln, an Nth parallel capacitor Dn coupled to the Nth series inductor Ln at the Nth node Cn, and an Nth anti-parallel capacitor Dn' coupled to the Nth series inductor Ln at the Nth node Cn. The cathodes of the parallel varactor diodes D1, D2, ..., Dn are coupled to the corresponding series inductors, while the anodes of the anti-varactor diodes D1', D2', ..., Dn' are coupled to the corresponding series inductors. Therefore, as shown by the rising and falling slope waveforms at nodes C1, C2, ..., Cn, the rising and falling times of the input signal RFI are compressed along the direction of the NLTL comb generator 510.

[0046] In one or more embodiments, the reference capacitance (capacitance at zero bias) of the parallel and anti-parallel capacitors in multiple segments along the signal propagation direction gradually decreases. Similarly, the inductance value of the series inductor decreases sequentially along multiple segments along the signal propagation direction. In other words, the reference capacitance of the parallel and anti-parallel capacitors in one segment is greater than the reference capacitance of the parallel and anti-parallel capacitors in the next segment along the signal propagation direction. For example, the reference capacitance of varactor diodes D1 and D1' in the first segment 521 is greater than the reference capacitance of varactor diodes D2 and D2' in the second segment 522.

[0047] The greater the time compression of the input signal as it propagates along the NLTL, the more higher-frequency harmonics the input signal will contain. Subsequent series inductors, parallel capacitors, and anti-parallel capacitors may have smaller dimensions and inductance / capacitance values ​​to impedance match the progressively higher frequency components of the input signal, thereby giving the output signal RFout a better comb spectrum frequency component.

[0048] In one or more embodiments, the reference capacitances of the parallel capacitors and anti-parallel capacitors of each segment can be different or the same. When the parallel capacitors and anti-parallel capacitors of each segment have the same capacitance, the rise time and fall time of the RF signal can be compressed simultaneously and symmetrically without increasing the size of the NLTL circuit. This characteristic is beneficial for circuit integration. Figure 5 As shown, for a sinusoidal input signal, the signal at the Nth node Cn is close to a square wave. This output signal, which is close to a square wave, will necessarily suppress all even harmonics in the spectrum.

[0049] Figure 6 The spectrum of the output signal of an NLTL comb generator that simultaneously compresses the rise and fall times is shown in one or more embodiments of the present invention. When the input signal RFin is 100MHz and the power is 20dBm, the output signal RFout has multiple harmonics. Figure 6 As shown, even harmonics are suppressed, and the power level is 20dB lower than that of adjacent odd harmonics.

[0050] The inherent suppression of even harmonics facilitates the extraction or filtering of odd harmonic signals. When the NLTL comb spectrum generator is used as a frequency multiplier, filtering by the BPF becomes easier because nearby even harmonics are necessarily suppressed. Therefore, a BPF with a moderate Q value can be used for signal filtering. For example, to extract a 2.5 GHz harmonic signal, a BPF with a moderate Q value and a center frequency of 2.5 GHz can be used to suppress or neutralize nearby harmonics; for instance, a suppression level of only 20 dB, rather than 40 dB, is sufficient to suppress the 2.4 GHz and 2.6 GHz harmonics. This reduction in BPF suppression requirements significantly lowers the cost and complexity of signal filtering.

[0051]

Example 5

[0052] Figure 7This illustration shows another NLTL comb spectrum generator with compressed rise and fall times, according to one or more embodiments of the present invention. Similar to NLTL 510, the NLTL comb spectrum generator 710 includes multiple segments 721, 722, etc., connected in series. The Nth segment includes an Nth series inductor Ln, an Nth parallel capacitor Dena, and an Nth anti-parallel capacitor Dnb. The Nth parallel capacitor Dena and the Nth anti-parallel capacitor Dnb can be varactor diodes with voltage-dependent capacitance, whose capacitance decreases as the reverse voltage increases.

[0053] In one or more embodiments, the NLTL comb spectrum generator 710 further includes a series input capacitor Cin 712 and a series output capacitor Cout 714, both of which are coupled to the signal propagation path as DC blockers to prevent DC components in the input signal RFin and the output signal RFout from entering the NLTL 710 and to prevent any DC signal in the NLTL 710 from leaking into the input signal RFin and the output signal RFout.

[0054] In one or more embodiments, the NLTL comb spectrum generator 710 further includes a grounded parallel branch 730 coupled to the signal propagation path 702 to set the DC bias of the parallel capacitor and the anti-parallel capacitor to DC ground. The grounded parallel branch 730 includes a series bias resistor 732 and a series bias inductor 734 to prevent radio frequency signals propagating along the signal propagation path from leaking to DC ground via the grounded parallel branch 730. Although Figure 7 Only one parallel bias branch is shown, but those skilled in the art will understand that multiple parallel bias branches can be set up to provide multiple DC grounding points for the signal propagation path.

[0055]

Example 6

[0056] Figure 8 This illustration shows yet another NLTL comb spectrum generator with rise time and fall time compression, according to one or more embodiments of the present invention. Similar to... Figure 7 The NLTL comb spectrum generator 710 shown in the figure includes multiple segments 821, 822, etc. connected in series. The Nth segment includes an Nth series inductor Ln, an Nth parallel capacitor Dena, and an Nth anti-parallel capacitor Dnb. The Nth parallel capacitor Dena and the Nth anti-parallel capacitor Dnb can be varactor diodes with voltage-dependent capacitance, whose capacitance decreases as the reverse voltage increases.

[0057] The NLTL comb spectrum generator 810 also includes a bias parallel branch 830 coupled between the signal propagation path 812 and the DC bias voltage Vbias, such that the DC bias voltage of the parallel capacitor and the anti-parallel capacitor is set to the DC bias voltage Vbias. The bias parallel branch 830 includes a bias resistor 832, a bias series inductor 834, and a parallel bias capacitor 836 as a decoupling capacitor. The DC bias voltage can be preset or adjustable for harmonic distribution tuning of the NLTL output signal.

[0058] although Figure 8 The bias parallel branch 830 is shown coupled to the DC bias voltage Vbias, but those skilled in the art will understand that the bias parallel branch 830 can be coupled to a low-frequency signal source that outputs a low-frequency signal so that the output signal RFout can be modulated by the low-frequency signal.

[0059]

Example 7

[0060] Figure 9 The process of generating harmonic signals in one or more embodiments of the present invention is illustrated. In step 905, the oscillator outputs a clock signal with a clock frequency of Fosc. In step 910, an NLTL comb generator generates an output signal that includes multiple harmonics of the clock signal, with some harmonics suppressed. The NLTL comb generator can employ the above embodiments or combinations thereof to achieve signal rise and fall time compression, DC ground bias, DC voltage Vbias, etc. In step 915, the output signal is filtered using a BPF to obtain one or more desired harmonics.

[0061] The invention has been described above to make it clear and understandable, but it is 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.

[0062] 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.

[0063] 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 nonlinear transmission line comb spectrum generator, characterized in that, include: The nonlinear transmission line comb spectrum generator generates an output signal that includes multiple harmonics of the input clock signal, comprising multiple segments connected in series. Each segment includes: Series inductor; A parallel capacitor, one end of which is coupled to the series inductor with a first polarity, and the other end of which is grounded; and A reverse parallel capacitor, one end of which is coupled to the series inductor with a second polarity opposite to the first polarity, and the other end of which is grounded. The parallel capacitor and the reverse parallel capacitor have voltage-dependent capacitance, which decreases as the reverse bias voltage increases.

2. The nonlinear transmission line comb spectrum generator according to claim 1, characterized in that, The parallel capacitor and the anti-parallel capacitor are varactor diodes or Schottky diodes. The cathode of the parallel capacitor is coupled to the series inductor, and the anode of the anti-parallel capacitor is coupled to the series inductor.

3. The nonlinear transmission line comb spectrum generator according to claim 1, characterized in that, The parallel capacitors and the anti-parallel capacitors in each segment have the same reference capacitor, which is a capacitor under zero bias voltage.

4. The nonlinear transmission line comb spectrum generator according to claim 3, characterized in that, Along the signal propagation path, the reference capacitance of the parallel capacitor and the anti-parallel capacitor in one segment is greater than the reference capacitance of the parallel capacitor and the anti-parallel capacitor in the next segment.

5. The nonlinear transmission line comb spectrum generator according to claim 1, characterized in that, Also includes: A grounded parallel branch, which is coupled to the signal propagation path, includes a series bias circuit. Set the resistor and series bias inductor.

6. The nonlinear transmission line comb spectrum generator according to claim 1, characterized in that, Also includes: A bias parallel branch, coupled between the DC bias voltage and the signal propagation path, wherein the bias... The parallel branch includes a series bias resistor, a series bias inductor, and a parallel bias capacitor.

7. The nonlinear transmission line comb spectrum generator according to claim 6, characterized in that, The DC bias voltage has a fixed or adjustable voltage.

8. The nonlinear transmission line comb spectrum generator according to claim 1, characterized in that, Also includes: An input capacitor, which is coupled in series to the signal propagation path for DC blocking of the input; and An output capacitor, which is connected in series to the signal propagation path for DC blocking and output impedance matching of the output.

9. A frequency multiplier, characterized in that, include: An oscillator is used to output a clock signal with a clock frequency. A nonlinear transmission line comb spectrum generator is used to receive the clock signal and generate an output signal, the output signal including... The nonlinear transmission line comb spectrum generator includes multiple segments containing multiple harmonics of the clock signal. The series connection forms the signal propagation path, and each segment includes: Series inductor; A parallel capacitor, one end of which is coupled to the series inductor with a first polarity, and the other end of which is grounded; and A reverse parallel capacitor, one end of which is coupled to the series inductor with a second polarity opposite to the first polarity, and the other end of which is grounded; the parallel capacitor and the reverse parallel capacitor have variable capacitance; and A bandpass filter is used to filter the output signal and output a frequency-multiplied signal, the frequency of which is the clock frequency. Integer multiples of the signal frequency.

10. A frequency multiplier according to claim 9, characterized in that, The parallel capacitor and the anti-parallel capacitor are varactor diodes or Schottky diodes. The parallel capacitor and the anti-parallel capacitor have voltage-dependent capacitance, which decreases as the reverse bias voltage increases. The cathode of the parallel capacitor is coupled to the series inductor, and the anode of the anti-parallel capacitor is coupled to the series inductor.

11. A frequency multiplier according to claim 10, characterized in that, The parallel capacitors and the anti-parallel capacitors in each segment have the same reference capacitor, which is a capacitor under zero bias voltage.

12. A frequency multiplier according to claim 11, characterized in that, Along the signal propagation path, the reference capacitance of the parallel capacitor and the anti-parallel capacitor in one segment is greater than the reference capacitance of the parallel capacitor and the anti-parallel capacitor in the next segment.

13. A frequency multiplier according to claim 9, characterized in that, The nonlinear transmission line comb spectrum generator also includes: A grounded parallel branch, which is coupled to the signal propagation path, includes a series bias circuit. Set the resistor and series bias inductor; or A bias parallel branch, coupled between the DC bias voltage and the signal propagation path, wherein the bias... The parallel branch includes a series bias resistor, a series bias inductor, and a parallel bias capacitor.

14. A frequency multiplier according to claim 9, characterized in that, The nonlinear transmission line comb spectrum generator also includes: An input capacitor, the input capacitor being coupled in series to the signal propagation path for DC blocking of the input; and An output capacitor, which is connected in series to the signal propagation path for DC blocking and output impedance matching of the output.

15. A frequency multiplier according to claim 9, characterized in that, The frequency of the frequency multiplier signal is an odd multiple of the frequency of the clock signal.

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