Terahertz frequency doubler with variable anodes connected in parallel

Abstract

The invention belongs to the technical field of terahertz devices, and particularly relates to a terahertz frequency doubler with variable anodes connected in parallel. Single-row diodes in a conventional frequency multiplier are connected in parallel in multiple rows, and after being copied, the single-row diodes are translated up and down and connected in parallel along the wide edge of a substrate; energy which is not completely absorbed and utilized by a single row of diode pairs is recycled by other rows of diode pairs, and the correlation between the increase of the number of whole tube cores and the width of the substrate is greatly reduced, so that the signal utilization conversion rate is improved; distances from each row of diodes to a short-circuit surface are different, effects on low-frequency and high-frequency signals are different, and then by adjusting the anode diameter of each row of diodes and the distance between the diodes, the low-frequency and high-frequency output efficiency is maximized, so that the overall output is maximized, and full-band overall flat and efficient output is realized. The terahertz frequency multiplier solves the problem that the output efficiency of an existing terahertz frequency multiplier is reduced along with the increase of the number of diodes.

Description

Technical Field

[0001] The invention belongs to the technical field of terahertz devices, and relates to a high-power single-input and single-output terahertz frequency doubler, in particular to a terahertz frequency doubler with parallel multi-variable anodes. Background Art

[0002] Electromagnetic waves with a frequency range of 0.1-10THz are usually defined as terahertz waves (THz waves), which are between millimeter waves and infrared light, and are in the transition zone from electronics to optics. Terahertz technology has significant advantages over traditional technologies in terms of penetration, safety, spectral resolution characteristics, and high-speed transmission. These advantages make terahertz technology have broad application prospects in many fields such as communications, medical treatment, security inspection, radar, etc. A stable terahertz source is extremely important in the field of terahertz communication. At present, solid-state frequency doubling sources based on semiconductor technology that have developed from microwave frequency bands to terahertz frequency bands occupy the main position of terahertz sources, with obvious advantages such as high reliability, low cost, small size and easy integration.

[0003] Traditional terahertz solid-state frequency multipliers use rectangular waveguide input, and the input signal is fed to the diodes, which are located in the same column. After the second harmonic is generated, it is transitioned to the output probe through multi-section microstrip matching, and then output through a standard rectangular waveguide. Under this structure, the substrate width increases with the number of diodes, which will lead to an increase in signal transmission loss. At the same time, as the number of anodes increases, the frequency multiplication efficiency of each diode decreases inversely, resulting in a decrease in the overall output of the frequency multiplier. Summary of the invention

[0004] In view of the above-mentioned problems or shortcomings, in order to solve the problem that the output efficiency of the existing terahertz frequency doubler decreases as the number of diodes increases, the present invention provides a terahertz doubler with parallel variable anodes. The frequency doubler is input to the diode by multi-stage waveguide matching, and the diode is in the form of multiple rows in parallel, so as to increase the number of tube cores under the premise of unchanged substrate width, thereby improving the power capacity of the device, that is, shortening the substrate width under the premise of increasing the number of tube cores, thereby reducing the parasitic resistance of the diode; the energy not fully absorbed and utilized by the single-row diode is recovered by other rows of diodes, thereby improving the energy utilization rate; the distance from each row of diodes to the short-circuit surface is different, and the effect on low-frequency and high-frequency signals is different. The number of columns of parallel diodes and the anode diameter of each row of diodes are adjusted to achieve the maximum output efficiency of low-frequency and high-frequency, so that the overall output is maximized, and the overall flat and efficient output of the full frequency band is achieved.

[0005] A terahertz frequency doubler with parallel variable anodes comprises an input matching waveguide, an input / output matching microstrip, a parallel diode pair, an output microstrip probe, an output matching waveguide and a CMRC filter.

[0006] The input matching waveguide has a first section that is a standard WR-12 waveguide, and several other sections that are branch matching waveguides. The final stage is a short-circuit surface. By continuously reducing the height of the waveguide, the width of the final stage reduced waveguide is consistent with the width of the substrate and matched with the diode parameters, so that the terahertz energy is evenly fed into the parallel diode pair.

[0007] The input / output matching microstrip, the input matching microstrip enables the input electromagnetic wave to be better coupled to the diode to generate the second harmonic, and the output matching microstrip transmits the second harmonic generated by the diode to the output matching waveguide end and reflects other useless harmonics.

[0008] The parallel diode pairs are single-column diode pairs that are replicated and then translated up and down along the wide side of the substrate for parallel connection. After the translation, the length and width of the microstrips between diodes on different sides of the same column and the length and width of the microstrips between diode pairs in different columns are adjusted, and the anode diameters of diodes in different columns are adjusted at the same time to achieve the best output effect.

[0009] Furthermore, in order to increase the output power, the number of diodes needs to be increased. If the traditional linear structure of diodes located in a straight line is adopted, the substrate width increases and the efficiency decreases. The form of connecting multiple rows of diodes in parallel solves this problem. While using a larger number of diodes, the width of the substrate is reduced, thereby increasing the power capacity and output power of the frequency multiplier.

[0010] The output microstrip probe converts the second harmonic generated by the parallel diode pair into a quasi-TEM mode in the output matching microstrip and outputs it from the output matching waveguide.

[0011] The output matching waveguide is a multi-section height-reducing waveguide that eventually transitions to a standard WR-6 waveguide output; the final stage of the output matching (height-reducing) waveguide is a short-circuit surface.

[0012] The main purpose of the CMRC filter is to perform DC feeding and prevent the generated second harmonic energy from leaking through the DC end, so that the energy passes through the output microstrip probe and then to the output matching waveguide output.

[0013] Furthermore, the parallel diode pairs can achieve maximum output efficiency in all frequency bands by adjusting the distance between each column of diode pairs and the short-circuit board.

[0014] Furthermore, when the number of parallel diode pairs is greater than 2, the total length of a single row of diode pairs in the width direction of the substrate (adjusting the inter-tube spacing of a single row of diodes) is gradient. By introducing a gradient linear structure, reflection and loss caused by step discontinuity are reduced; at the same time, the gradient microstrip line can provide more matching levels, making the field transmission more natural and efficient.

[0015] In summary, in the present invention, by cleverly connecting multiple rows of linear doubled frequency structures in parallel, the number of diodes is increased while the substrate width can be controlled, and the anode diameters of diodes in different columns are adjusted to achieve the best output effect, thereby achieving higher output and higher efficiency in the full frequency band. This structure may be of great significance to future terahertz communication devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is an overall structural diagram of an embodiment device;

[0017] Figure 2 A detailed diagram of a double row of parallel diode pairs of an embodiment device;

[0018] Figure 3 is an input efficiency curve diagram of the device of the embodiment;

[0019] Figure 4 Graph showing output power and efficiency of the device of the embodiment. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0021] In this embodiment, HFSS simulation software is used to input terahertz fundamental waves through a standard rectangular waveguide, and input matching is performed by optimizing the length and width of the waveguide at each level, and the distance from the end short-circuit surface to the diode, so that energy can be better fed into the parallel diode pair; the parallel diode pair in this embodiment adopts a double-row parallel form to achieve efficient use of energy.

[0022] like Figure 1 As shown in the figure, the overall structure of the device of this embodiment is shown. The energy is fed into the double-row parallel diode pair through the input matching waveguide. The details of the double-row parallel diode pair are shown in Figure 2 As shown in the figure, 6 diodes are used in a single row, and a total of 12 Schottky diodes are used; compared with the two rows of parallel diode pairs, one row of diodes has a large anode diameter, and the other row of diodes has a small anode diameter, which realizes efficient use of the input low-frequency and high-frequency signals. Then, through the microstrip and output matching transition, the second harmonic is output well.

[0023] For the frequency multiplier, the nonlinear effect of the current and voltage at both ends of the diode is used to achieve the frequency multiplication of the input signal. The nonlinear IV characteristic curve is expanded into a Taylor series at a fixed bias point V, and the output current i o for

[0024] i o =f(V+v)=a0+a1v+a2v 2 +a3v 3 +...+an v n

[0025] Among them, a0 represents the DC component of the output; a1 represents the fundamental component of the output; a n Represents the nth harmonic component.

[0026] For the frequency multiplier, the input is generally a single-tone signal. Assume that the input signal is a sinusoidal signal v in =V0 cosω0t, where V0 represents the signal amplitude, ω0 represents the signal frequency, and t represents time. Output current i out for:

[0027]

[0028] It can be seen from the above formula that due to the nonlinear effect of the diode, a large number of harmonic components will be generated after a sinusoidal signal is input. The power of each component is different. Through multi-section microstrip matching filtering with different impedances, the required second harmonic signal is selected and the output is extracted as much as possible to obtain the double frequency of the input signal.

[0029] The frequency doubler is input to the diode by multi-stage waveguide matching. The diodes are in the form of multiple rows in parallel. The increase in the number of tube cores increases the power capacity of the device, shortens the substrate width and reduces the parasitic resistance of the diode; the energy that is not fully absorbed and utilized by a row of diodes is recovered by other rows of diodes, and the efficiency remains unchanged while the number of tube cores increases; the distance from each row of diodes to the short-circuit surface is different, and the effect on low-frequency and high-frequency signals is different. The anode diameter of each row of diodes is adjusted to achieve the maximum output efficiency of low-frequency and high-frequency signals, thereby maximizing the overall output and achieving overall flat and efficient output over the entire frequency band.

[0030] like Figure 3 As shown, this figure is an input efficiency diagram of the device of this embodiment. The structure has good input matching, and the energy of the terahertz fundamental wave can be used by the diode as much as possible to generate the second harmonic.

[0031] like Figure 4 As shown, this figure is the output power and efficiency diagram of the device of this embodiment. It can be found that the structure has a high power output in the full frequency band, and the output efficiency is mostly above 8%, achieving a high conversion efficiency while achieving a large working bandwidth.

[0032] It can be seen from the above embodiments that the present invention uses a single-row diode in a conventional frequency multiplier in the form of multiple rows in parallel, and then replicates the single-row diode pair and moves it up and down along the wide side of the substrate for parallel connection; the energy that is not fully absorbed and utilized by the single-row diode pair is recovered by other rows of diode pairs, and the correlation between the increase in the number of overall tube cores and the width of the substrate is greatly reduced, thereby improving the utilization conversion rate of the signal; and each row of diode pairs has a different distance to the short-circuit surface, and has different effects on low-frequency and high-frequency signals, and then by adjusting the anode diameter of each row of diodes and the spacing between diodes, the low-frequency and high-frequency output efficiency is maximized, so that the overall output is maximized, and the overall flat and efficient output of the full band is achieved. The present invention solves the problem that the output efficiency of the existing terahertz frequency multiplier decreases with the increase in the number of diodes, which is of great significance to future terahertz communication devices.

Claims

1. A terahertz frequency doubler with multiple variable anodes in parallel, characterized in that: Includes input matching waveguide, input / output matching microstrip, parallel diode pair, output microstrip probe, output matching waveguide and CMRC filter; The input matching waveguide has a first section that is a standard WR-12 waveguide, and several other sections that are branch matching waveguides. The final stage is a short-circuit surface. By continuously reducing the height of the waveguide, the width of the final stage reduced waveguide is consistent with the width of the substrate and matched with the diode parameters, so that the terahertz energy is uniformly fed into the parallel diode pair. The input / output matching microstrip, the input matching microstrip couples the input electromagnetic wave to the parallel diode pair to generate the second harmonic, the output matching microstrip transmits the second harmonic generated by the parallel diode pair to the output matching waveguide end, and reflects other useless harmonics; The parallel diode pairs are single-column diode pairs that are replicated and then translated up and down along the wide side of the substrate before being connected in parallel. After the translation, the length and width of the microstrips between the diodes on different sides of the same column and the length and width of the microstrips between the diode pairs in different columns are adjusted, and the anode diameters of the diodes in different columns are adjusted at the same time, so that the output efficiency of the diode pairs in each column in the corresponding frequency band is maximized; The output microstrip probe converts the second harmonic generated by the parallel diode pair into a quasi-TEM mode in the output matching microstrip and outputs it from the output matching waveguide; The output matching waveguide is a multi-section height-reducing waveguide that eventually transitions to a standard WR-6 waveguide output, and the final stage is a short-circuit waveguide. The CMRC filter performs direct current feeding and prevents the generated second harmonic energy from leaking through the direct current end, so that the energy passes through the output microstrip probe and then outputs to the output matching waveguide.

2. The terahertz frequency doubler with parallel variable anodes as claimed in claim 1, characterized in that: The parallel diode pairs increase the number of parallel-connected single-row diodes without changing the width of the substrate, thereby increasing the number of overall tube cores and improving the power capacity of the overall device.

3. The terahertz frequency doubler with parallel variable anodes as claimed in claim 1, characterized in that: The parallel diode pairs can achieve maximum output efficiency in all frequency bands by adjusting the distance between each column of diode pairs and the short-circuit board.

4. The terahertz frequency doubler with parallel variable anodes as claimed in claim 1, characterized in that: The number of parallel diode pairs connected in parallel is equal to 2.

5. The terahertz frequency doubler with parallel variable anodes as claimed in claim 1, characterized in that: When the number of parallel diode pairs is greater than 2, the total length of a single row of diode pairs in the width direction of the substrate changes gradually.

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