Frequency multiplication type power synthesis structure and terahertz equipment

Abstract

The invention discloses a frequency multiplication type power synthesis structure and terahertz equipment, which are applied to the technical field of terahertz, and comprise an input E-plane T / Y junction and an output E-plane T / Y junction, the input E-plane T / Y junction is provided with two branches, and the polarities of electric fields of signals in the two branches are opposite; one branch is connected with one input end of the output E-plane T / Y-type junction through a frequency doubling unit, and the other branch is connected with the other input end of the output E-plane T / Y-type junction through another frequency doubling unit; the frequency doubling unit comprises a connecting branch and a microstrip line of an output E-plane T / Y junction input end, and the microstrip line is sequentially connected with a balanced frequency doubling diode pair and a monopole-like antenna in the signal transmission direction of the microstrip line; the monopole-like antenna is used for regulating and controlling the polarity of an electric field of a signal in the connected microstrip line, so that the polarities of the electric fields of the signals transmitted to the two input ends in the output E-plane T / Y-type junction are the same. The polarity of an electric field in each microstrip line is individually regulated and controlled in a targeted manner through the monopole-like antenna, and the frequency doubling synthesis efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of terahertz technology, and in particular to a frequency doubling power synthesis structure and a terahertz device. Background Art

[0002] With its unique advantages, terahertz technology has greatly promoted the development of basic frontier sciences such as earth atmosphere observation, planetary observation and space aerospace in the past decades. It also plays a huge role in human security inspection, environmental monitoring, fault detection, archaeology and medical diagnosis. In recent years, the requirements of imaging technology for resolution and imaging speed have promoted the development of terahertz application systems towards array and high frequency, which in turn has put forward an increasingly higher demand for high-power Schottky frequency doubling sources.

[0003] After decades of development and accumulation, the development of terahertz Schottky diode frequency doubling circuits has become relatively mature internationally, and a large number of high-power and high-efficiency frequency doubling source products have emerged. However, although the frequency doubling efficiency of existing single-channel frequency doubling circuits can be relatively high, the actual output power is limited. The main limiting factors are: (1) The power capacity of GaAs diodes is limited. When the driving power exceeds the optimal operating point, the efficiency decreases and the output power is compressed and saturated; (2) The mutual restriction between the number of diode junctions and the frequency doubling efficiency. At the same frequency, the more diode junctions, the greater the saturation power, but the corresponding efficiency decreases; (3) The thermal effect and reverse breakdown effect under high driving power cause the device to be electrically or thermally broken down. In order to solve the problem of power capacity expansion, the power synthesis frequency doubling circuit structure is called the most direct method. Among them, odd-order frequency doubling is relatively simple to implement due to the consistency of phase, and it has been reported the most and earliest. On the contrary, due to the different phases of odd and even harmonics, even-order frequency doubling requires the use of fixed coupling or other synthesis networks on the synthesis network, which not only limits the synthesis form, but also causes the peripheral circuit size to be large and introduces huge insertion power loss. Therefore, how to provide a high frequency doubling efficiency frequency doubling power synthesis structure is an urgent problem that technicians in this field need to solve. Summary of the invention

[0004] An object of the present invention is to provide a frequency doubling power synthesis structure with high frequency doubling efficiency; another object of the present invention is to provide a terahertz device with high frequency doubling efficiency.

[0005] In order to solve the above technical problems, the present invention provides a frequency doubling power synthesis structure, comprising an input E-plane T / Y-type junction and an output E-plane T / Y-type junction; the input E-plane T / Y-type junction has two branches, and the electric field polarities of the signals in the two branches are opposite;

[0006] One of the branches is connected to one input end of the output E-plane T / Y-type junction through a frequency doubling unit, and the other branch is connected to the other input end of the output E-plane T / Y-type junction through another frequency doubling unit;

[0007] The frequency doubling unit includes a microstrip line connecting the branch and the input end of the output E-plane T / Y-type junction. The microstrip line is along the signal transmission direction, and the microstrip line is sequentially connected with a balanced frequency doubling diode pair and a monopole-like antenna; the monopole-like antenna is used to adjust the electric field polarity of the signal in the connected microstrip line so that the electric field polarity of the signal transmitted to the two input ends of the output E-plane T / Y-type junction is the same.

[0008] Optionally, the two diodes in the balanced frequency doubling diode pair have the same direction, one end is connected to the microstrip line and the other end is grounded.

[0009] Optionally, an impedance matching network is provided on the microstrip line between the balanced frequency doubling diode pair and the monopole-like antenna.

[0010] Optionally, the monopole-like antenna is connected to a low-pass filtering circuit.

[0011] Optionally, at least one of the monopole-like antennas is used to reverse the electric field polarity of a signal in the connected microstrip line.

[0012] Optionally, the two frequency multiplication units have the same structure.

[0013] Optionally, the microstrip line is a microstrip line processed on the surface of a substrate.

[0014] Optionally, the diodes in the balanced frequency-doubling diode pair are connected to the microstrip line by a conductive adhesive bonding process or a welding process.

[0015] Optionally, the input E-plane T / Y-type junction is a metal input E-plane T / Y-type junction with a gold-plated surface, and the output E-plane T / Y-type junction is a metal output E-plane T / Y-type junction with a gold-plated surface.

[0016] The present invention also provides a terahertz device, comprising the frequency doubling power synthesis structure as described in any one of the above items.

[0017] The invention provides a frequency doubling power synthesis structure, comprising an input E-plane T / Y-type junction and an output E-plane T / Y-type junction; the input E-plane T / Y-type junction has two branches, and the electric field polarities of the signals in the two branches are opposite; one branch is connected to an input end of the output E-plane T / Y-type junction through a frequency doubling unit, and the other branch is connected to the other input end of the output E-plane T / Y-type junction through another frequency doubling unit; the frequency doubling unit comprises a microstrip line connecting the branch and the input end of the output E-plane T / Y-type junction, and along the signal transmission direction of the microstrip line, the microstrip line is sequentially connected with a balanced frequency doubling diode pair and a quasi-monopole antenna; the quasi-monopole antenna is used for adjusting the electric field polarity of the signal in the connected microstrip line, so that the electric field polarities of the signal transmitted to the two input ends of the output E-plane T / Y-type junction are the same.

[0018] The signal is frequency-doubled by a balanced frequency-doubling diode, and the electric field polarity in each microstrip line is specifically and individually adjusted through a quasi-monopole antenna, so that the differential signal can be synthesized in phase at the output E-plane T / Y-junction, freeing the traditional frequency-doubling power synthesis circuit from the high constraint on the phase difference of the input drive signal, thereby achieving a replacement for the directional coupler, reducing the insertion loss introduced by such functional components, and improving the efficiency of frequency-doubling synthesis.

[0019] The present invention also provides a terahertz device, which also has the above-mentioned beneficial effects, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] FIG1 is a schematic structural diagram of a frequency doubling power synthesis structure provided by an embodiment of the present invention;

[0022] FIG. 2 is a schematic diagram showing that the polarity of the output electric field of the two frequency doubling units in FIG. 1 is adjustable.

[0023] In the figure: 1. Input E-plane T / Y-type junction, 2. Output E-plane T / Y-type junction, 3. Frequency doubling unit, 31. Balanced frequency doubling diode pair, 32. Quasi-monopole antenna, 33. Low-pass filter circuit. DETAILED DESCRIPTION

[0024] The core of the present invention is to provide a frequency doubling power synthesis structure. In the prior art, the actual output power of a single-channel frequency multiplier circuit is limited. The main limiting factors are: (1) The power capacity of GaAs diodes is limited. When the driving power exceeds the optimal operating point, the efficiency decreases and the output power is compressed and saturated; (2) The mutual restriction between the number of diode junctions and the frequency doubling efficiency. The more diode junctions there are at the same frequency, the greater the saturation power, but the corresponding efficiency decreases; (3) The thermal effect and reverse breakdown effect under high driving power cause the device to be electrically or thermally broken down. In order to solve the problem of power capacity expansion, the power synthesis frequency multiplication circuit structure is called the most direct method. Among them, odd-order frequency multiplication is relatively simple to implement due to the consistency of phase, and the reports are the most and earliest. On the contrary, due to the different phases of odd and even harmonics, even-order frequency multiplication requires the use of fixed coupling or other synthesis networks on the synthesis network, which not only limits the synthesis form, but also causes the peripheral circuit size to be large and introduces huge insertion power loss.

[0025] The present invention provides a frequency doubling power synthesis structure, which includes an input E-plane T / Y-type junction and an output E-plane T / Y-type junction; the input E-plane T / Y-type junction has two branches, and the electric field polarities of the signals in the two branches are opposite; one branch is connected to an input end of the output E-plane T / Y-type junction through a frequency doubling unit, and the other branch is connected to the other input end of the output E-plane T / Y-type junction through another frequency doubling unit; the frequency doubling unit includes a microstrip line connecting the branch and the input end of the output E-plane T / Y-type junction, and the microstrip line is connected to a balanced frequency doubling diode pair and a quasi-monopole antenna in sequence along the signal transmission direction; the quasi-monopole antenna is used to adjust the electric field polarity of the signal in the connected microstrip line, so that the electric field polarities of the signals transmitted to the two input ends of the output E-plane T / Y-type junction are the same.

[0026] The signal is frequency-doubled by a balanced frequency-doubling diode, and the electric field polarity in each microstrip line is specifically and individually adjusted through a quasi-monopole antenna, so that the differential signal can be synthesized in phase at the output E-plane T / Y-junction, freeing the traditional frequency-doubling power synthesis circuit from the high constraint on the phase difference of the input drive signal, thereby achieving a replacement for the directional coupler, reducing the insertion loss introduced by such functional components, and improving the efficiency of frequency-doubling synthesis.

[0027] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] Embodiment 1

[0029] Please refer to FIG. 1 and FIG. 2 , FIG. 1 is a schematic diagram of a frequency doubling power synthesis structure provided in an embodiment of the present invention; FIG. 2 is a schematic diagram of adjustable output electric field polarity of two frequency doubling units in FIG. 1 .

[0030] Referring to Figures 1 and 2, in the embodiment of the present invention, the frequency doubling power synthesis structure includes an input E-plane T / Y-type junction 1 and an output E-plane T / Y-type junction 2; the input E-plane T / Y-type junction 1 has two branches, and the electric field polarities of the signals in the two branches are opposite; one of the branches is connected to an input end of the output E-plane T / Y-type junction 2 through a frequency doubling unit 3, and the other branch is connected to the other input end of the output E-plane T / Y-type junction 2 through another frequency doubling unit 3; the frequency doubling unit 3 includes a microstrip line connecting the branch and the input end of the output E-plane T / Y-type junction 2, and the microstrip line is along the signal transmission direction, and the microstrip line is sequentially connected with a balanced frequency doubling diode pair 31 and a monopole-like antenna 32; the monopole-like antenna 32 is used to adjust the electric field polarity of the signal in the connected microstrip line, so that the electric field polarity of the signal transmitted to the two input ends of the output E-plane T / Y-type junction 2 is the same.

[0031] In this embodiment, the input E-plane T / Y-type junction 1 is used to convert the received signal into a differential signal, which usually has an input end and two output ends, the two output ends are located in two branches, and the two branches are used to transmit signals with opposite electric field polarities to form a differential signal. The above-mentioned output E-plane T / Y-type junction 2 has two input ends and two output ends. In this embodiment, the two signals of the input E-plane T / Y-type junction 1 will be transmitted to the two input ends of the output E-plane T / Y-type junction 2 after processing, and will be synthesized in the output E-plane T / Y-type junction 2, and finally transmitted from the output end of the output E-plane T / Y-type junction 2 to the output waveguide. The specific structure of the input E-plane T / Y-type junction 1 and the output E-plane T / Y-type junction 2 can refer to the prior art, and will not be repeated here. The above-mentioned input E-plane T / Y-type junction 1 is mainly used to generate a differential signal, and its two branches are used to transmit one signal in the differential signal respectively.

[0032] In this embodiment, the frequency doubling power synthesis structure is provided with two frequency doubling units 3, and each of the above branches is provided with a frequency doubling unit 3, that is, one branch is connected to one input end of the output E-plane T / Y-type junction 2 through one frequency doubling unit 3, and the other branch is connected to the other input end of the output E-plane T / Y-type junction 2 through another frequency doubling unit 3. It should be emphasized that in this embodiment, in order to ensure that the signal can be completely synthesized in the end, the symmetry of the two branches needs to be ensured, so the structures of the above two frequency doubling units 3 usually need to be consistent.

[0033] In this embodiment, the frequency multiplication unit 3 includes a microstrip line connecting the branch and the input end of the output E-plane T / Y-type junction 2. Along the signal transmission direction of the microstrip line, the microstrip line is sequentially connected with a balanced frequency multiplication diode pair 31 and a quasi-monopole antenna 32. In this embodiment, a total of two microstrip lines are provided, one microstrip line connects the output end of the input E-plane T / Y-type junction 1 and the input end of the output E-plane T / Y-type junction 2 corresponding to one path, and is used to transmit signals between the two. At this time, the microstrip line has a signal transmission direction, that is, the direction from the output end of the input E-plane T / Y-type junction 1 to the input end of the output E-plane T / Y-type junction 2.

[0034] The above-mentioned microstrip line is sequentially provided with a balanced frequency doubling diode pair 31 and a monopole-like antenna 32 along the signal transmission direction, that is, the signal transmitted to the microstrip line will first pass through the balanced frequency doubling diode pair 31 for frequency doubling, and then pass through the monopole-like antenna 32 for adjusting the electric field polarity. In this embodiment, the balanced frequency doubling diode pair 31 usually has two diodes. In this structure, the directions of the two diodes in the balanced frequency doubling diode pair 31 are usually the same, one end is connected to the microstrip line, and the other end is grounded, forming a balanced frequency doubling diode pair 31 to double the signal. In this embodiment, the balanced frequency doubling diode pair 31 is usually a balanced double frequency Schottky diode pair, which can convert the second harmonic under the excitation of the polar electric field of the input waveguide, so that it can achieve balanced output of the second harmonic, and intrinsically suppress the adjacent odd harmonic components, and achieve intrinsic suppression of the third harmonic. Of course, other balanced frequency doubling diode pairs 31 can also be provided in this embodiment, which is not specifically limited here.

[0035] The above-mentioned monopole-like antenna 32 is used to adjust the electric field polarity of the signal in the connected microstrip line. In this embodiment, the microstrip line is provided with an impedance matching network between the balanced frequency doubling diode pair 31 and the monopole-like antenna 32. One of the main functions of the impedance matching network is to ensure that the harmonics generated by the balanced frequency doubling diode pair 31 can be well transmitted backward in the microstrip line. Furthermore, in this embodiment, the impedance matching network can have a low-pass filtering structure, for example, a microstrip line structure of "narrow→wide→narrow" exists along the signal transmission direction, forming a low-pass filtering structure to filter the signal.

[0036] Referring to Figure 2, in this embodiment, the monopole-like antenna 32 can be connected to a low-pass filter circuit 33. At this time, based on the monopole-like antenna 32 and the loaded low-pass filter circuit 33, DC feeding of the above-mentioned balanced frequency doubling diode pair 31 is realized, forming a DC feeding channel from the monopole-like antenna 32 to the balanced frequency doubling diode pair 31.

[0037] In this embodiment, at least one of the monopole-like antennas 32 is used to reverse the electric field polarity of the signal in the connected microstrip line. The above-mentioned monopole-like antenna 32 is used to adjust the electric field polarity of the signal in the connected microstrip line, so that the electric field polarity of the signal transmitted to the two input ends of the output E-plane T / Y-type junction 2 is the same, thereby realizing the synthesis of the signal in the output E-plane T / Y-type junction 2, and realizing the power synthesis function. Since the entire frequency doubling power synthesis structure is provided with two monopole-like antennas 32 in this embodiment, the two single-machine sub-antennas can adjust the electric field polarity of the signal in their respective microstrip lines, so that the final signal can be synthesized in the same direction. It can also be that only one monopole-like antenna 32 adjusts the electric field polarity of the signal in its microstrip line, so that the electric field polarity of the signal in the microstrip line to which it is connected is reversed, ensuring that the electric field polarity of the two signals is the same. At this time, although only one monopole-like antenna 32 is working, it is also necessary to provide a monopole-like antenna 32 in both frequency doubling units 3 to ensure the symmetry of the two branches. That is, in this embodiment, the two frequency multiplication units 3 have the same structure.

[0038] As shown in FIG1 , the input E-plane T / Y-type junction 1 can be used to input the TE of the standard rectangular waveguide. 10 The mode signal is divided into a pair of equal-amplitude signals S1 and S2. With respect to the second plane as the reference plane, the electric field polarities of the equal-amplitude signals S1 and S2 are opposite. Therefore, the two frequency multiplication units 3 will be driven by a pair of equal-amplitude anti-phase signals. Since the two frequency multiplication units 3 both include a balanced frequency multiplication diode pair 31, which belongs to a balanced double frequency multiplication structure, it can only output the second harmonic to the output end, so ideally, the second harmonics output by the two frequency multiplication units 3 need to be equal in amplitude and in phase. Therefore, in this embodiment, by regulating the polarity of the monopole-like antenna 32, it is possible to construct an in-phase synthesis of the second harmonic signal. In this way, the amplitude-phase imbalance and huge insertion loss between units caused by the redundant directional coupler structure can be eliminated, and the power synthesis efficiency and frequency multiplication efficiency can be improved. In the figure of this embodiment, the first plane is a plane opposite to the second plane, and the second plane can be defined as a reference plane. In this embodiment, the signal frequency input to the input E-plane T / Y-type junction 1 is ω0, and the signal frequency output from the output E-plane T / Y-type junction 2 can be 2ω0.

[0039] In the present embodiment, the cavity of the frequency doubling circuit can be processed by materials such as aluminum and copper, and the surface can be gold-plated, that is, in the present embodiment, the input E-surface T / Y-type junction 1 can be a metal input E-surface T / Y-type junction 1 with a gold-plated surface, and the output E-surface T / Y-type junction 2 can be a metal output E-surface T / Y-type junction 2 with a gold-plated surface. The microstrip line of the frequency doubling unit 3 can be a microstrip line processed on the surface of a substrate, and the substrate can be a thin-film substrate such as quartz, alumina ceramic, aluminum nitride ceramic, etc., and the above-mentioned microstrip line is formed by processing. The installation of the diodes constituting the balanced frequency doubling diode pair 31 can be achieved by a conventional conductive adhesive bonding process or a welding process, that is, the diodes in the balanced frequency doubling diode pair 31 can be connected to the microstrip line by a conductive adhesive bonding process or a welding process.

[0040] In a frequency doubling power synthesis structure provided by an embodiment of the present invention, the frequency doubling unit 3 can adjust the polarity of the electric field coupled to the output waveguide by adjusting the polarity of the monopole-like antenna 32, thereby ensuring that no matter whether the phase difference of the second harmonic signal generated by the frequency doubling is 0° or 180°, it can be matched with the in-phase synthesis condition of the output E-plane T / Y-type junction 2. In this way, the high constraint on the phase difference of the input end driving signal in the traditional frequency doubling power synthesis circuit is liberated, and the directional coupler is replaced in the circuit, which can reduce the insertion loss introduced by such functional components and improve the efficiency of frequency doubling synthesis.

[0041] At the same time, the frequency doubling unit 3 can also realize DC feeding of the diode pair by loading a low-pass filtering structure at the monopole-like antenna 32 terminal at the output end, thereby ensuring that the double frequency unit 3 operates at a bias voltage with stronger nonlinearity, so that the frequency doubling power synthesis structure proposed in this embodiment has the advantage of adjustable output electric field polarity, ensuring that the frequency doubling power synthesis structure has the characteristics of high amplitude and phase balance, high integration, high efficiency and broadband, and is suitable for frequency multiplier design and power capacity expansion in the entire terahertz frequency band.

[0042] Embodiment 2

[0043] A terahertz device provided by an embodiment of the present invention is introduced below. The terahertz device described below and the frequency doubling power synthesis structure described above can be referred to each other.

[0044] In this embodiment, the terahertz device includes a frequency doubling power synthesis structure provided by any of the above-mentioned invention embodiments. The specific structure of the frequency doubling power synthesis structure has been described in detail in the above-mentioned invention embodiments, and will not be described in detail here. The remaining structures of the terahertz device, such as the antenna, the housing, etc., can refer to the prior art, and will not be described in detail here.

[0045] Since the terahertz device provided in this embodiment specifically uses the frequency doubling power synthesis structure provided in the above embodiments, the terahertz device can have a higher frequency doubling synthesis efficiency and thus has better performance.

[0046] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0047] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0048] The above is a detailed introduction to a frequency doubling power synthesis structure and a terahertz device provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A frequency doubling power synthesis structure, characterized in that: It includes an input E-plane T / Y-type junction and an output E-plane T / Y-type junction; the input E-plane T / Y-type junction has two branches, and the electric field polarities of the signals in the two branches are opposite; One of the branches is connected to one input end of the output E-plane T / Y-type junction through a frequency doubling unit, and the other branch is connected to the other input end of the output E-plane T / Y-type junction through another frequency doubling unit; The frequency doubling unit includes a microstrip line connecting the branch and the input end of the output E-plane T / Y-type junction. The microstrip line is along the signal transmission direction, and the microstrip line is sequentially connected with a balanced frequency doubling diode pair and a monopole-like antenna; the monopole-like antenna is used to adjust the electric field polarity of the signal in the connected microstrip line so that the electric field polarity of the signal transmitted to the two input ends of the output E-plane T / Y-type junction is the same.

2. The frequency doubling power synthesis structure according to claim 1, characterized in that: The two diodes in the balanced frequency doubling diode pair have the same direction, one end of the two diodes is connected to the microstrip line and the other end is grounded.

3. The frequency doubling power synthesis structure according to claim 1, characterized in that: The microstrip line is located between the balanced frequency doubling diode pair and the monopole-like antenna and is provided with an impedance matching network.

4. The frequency doubling power synthesis structure according to claim 1, characterized in that: The monopole-like antenna is connected to a low-pass filter circuit.

5. The frequency doubling power synthesis structure according to claim 1, characterized in that: At least one of the monopole-like antennas is used to reverse the electric field polarity of the signal in the connected microstrip line.

6. The frequency-doubling power synthesis structure according to claim 5, characterized in that: The two frequency multiplication units have the same structure.

7. The frequency doubling power synthesis structure according to claim 1, characterized in that: The microstrip line is a microstrip line processed on the surface of the substrate.

8. The frequency doubling power synthesis structure according to claim 2, characterized in that: The diodes in the balanced frequency doubling diode pair are connected to the microstrip line through a conductive adhesive bonding process or a welding process.

9. The frequency doubling power synthesis structure according to claim 1, characterized in that: The input E-surface T / Y-type junction is a metal input E-surface T / Y-type junction with a gold-plated surface, and the output E-surface T / Y-type junction is a metal output E-surface T / Y-type junction with a gold-plated surface.

10. A terahertz device, characterized in that: It comprises a frequency doubling power synthesis structure as described in any one of claims 1 to 9.

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