TWI223495B - Tapped antiparallel hairpin-comb filters for microwave applications - Google Patents

Abstract

Tapped antiparallel hairpin-comb filters utilize two sets of hairpin (i.e., folded) half-wavelength microstrip or stripline resonators arranged side-by-side, but with opposite direction for these two sets. The input/output terminals of the filter are formed by tapped lines, respectively. The coupling regions between resonators extend parallel to the sides of the resonators with the same orientation for each set of hairpin resonators. Two sets of hairpin resonators are arranged in the opposite direction to each other to form an antiparalleled hairpin-comb filter. The coupling effects between these two resonator sets can reduce the couplings between resonators and then produce a compact filter structure having a narrow band filter response. The structure can also produce poles of attenuation adjacent to the passband, especially enhance the cutoff characteristic of a filter at passband edges.

Description

1223495 V. Description of the invention d) [Technical Field] The present invention is a narrow-passband filter suitable for microwave communication. The wavelet device of the present invention has good passband selectivity, that is, it has a high degree of steepness at the edges of the passband, and can filter noise very cleanly. This type of filter is not only made of metal thin film, it is more suitable for high temperature superconducting thin film with high quality factor. The invention is suitable for making high-temperature superconducting filters, and is applied to various microwave communication systems. [Prior technology] For a long time, the filter Is (Filter) is an important component in the microwave communication system. It has the function of filtering noise and making communication signals clear. There are four types of filter _ filter: Low pass filter (High pass filter), High pass filter (High pass filter), Band pass filter (Band pass filter) and Band stop filter (Band Eiimination Filter). The function of the band-pass filter is to allow signals with a fixed bandwidth to pass through, while blocking the signals at the lower and higher frequencies. The band-pass filter is particularly important in the application of limited frequency resources, and is especially suitable for the receiving and transmitting systems of base stations. In recent years, due to the rapid development of wireless communication technology, wireless communication and high-speed data transmission have caused mutual interference between adjacent frequency bands in many areas, leading to communication. The quality of the mouth has deteriorated and the revenue of wireless communication companies has suffered. Regarding this kind of problem, in general, wireless communication companies wish to increase the number of base stations to maintain the quality of communication ’, but because of this, they have increased investment and increased workload, thus reducing revenue. Filters made of high-temperature superconducting thin films in the microwave band (1GHz,-

Page 7 1223495 V. Explanation of the invention (2) 77K) The impedance (〇.〇3πιΩ) is smaller than the traditional metal copper (^ 〇) by 10000 ′ and therefore has a very high quality factor (low impedance). The characteristics of low loss and high selectivity (high-pass-band steepness) make full use of microwave communications with increasing frequency requirements and solve the problem of radio wave interference caused by insufficient frequency resources. Therefore, the United States, Japan and other advanced countries have invested in research and development and began to apply filters made of high-temperature superconducting thin films to the receiving systems of wireless communication base stations. After the base station uses the high-temperature superconducting filter, it can effectively suppress the interference of radio frequency signals outside the frequency, and make full use of the resources of the limited frequency to increase the coverage area of the base station and reduce the interference of noise, and improve the communication mouth, and can reduce The transmission power of mobile phones can greatly reduce the influence of electromagnetic wave radiation on human beings, and meet the requirements of environmental protection. It can effectively solve the problem that the above-mentioned insufficient frequency resources cause the degradation of communication quality. The filters made of high-temperature superconducting thin films are mostly planar structures, and can have different structures. Figure 1 shows a typical comb-line filter with a four-stage (fourth-order) strip line structure. One end of the resonator (11) is grounded (12), and the other end is connected to a capacitor (13, η), and then ground (1 5). The left and right input and output terminals (i 6) are tapped-1 ine and are directly connected to the first and fourth resonators. Figure 2 is a general-purpose band-pass filter for hairpin-resonators. Please refer to e. G. Cristal and S. F ranke 1, M Hairpin-ling and Hybrid Hairpin-Line / Half-Wave Parallel -Coupled-Line Filters', IEEEE Trams. MTT, vol. MTT-20, pp.719-728, (November 1972). In this design, the

Page 8 1223495 V. Description of the invention (3) The direction of the resonator (2 1) is alternately up and down. This result makes the resonators have a strong coupling effect (Coupling effect), suitable for making broadband filters; if used for making narrow-band filters, the filters will require a considerable amount of space, resulting in thin films ( Th i n-fi 1 m) The size of the substrate is increased, which in turn increases the cooling capacity load of the superconducting filter and the superconducting device. Due to the miniaturization of the size of the microwave communication system, it is particularly important Therefore, the significance of using a superconducting filter is reduced. Figure 3 shows another filter structure for hairpin resonators. Please refer to M. Sagawa, K. Takahashi, and M. Makimoto, M Miniaturized Hairpin Resonator Filters and their Application to Receiver Front-End MIC, sn, IEEE Trams. MTT vol. 37, pp. 199 and 1997 (December 1998). This design is shortened at the front end of the resonator opening (31) and produces a strong capacitive effect (3 2). The resonator exhibits a semilumped nature (33), that is, the upper end (open end) appears Capacitive effect, inductive effect appears at the lower end. The resonance direction of this filter structure is all the same. In order to shorten the length of the entire resonator, the capacitance part of the resonator can be quite large and the inductance part can be quite small; but in this way, its quality factor (Q value) will be reduced, and resonance between the various resonators (34) cannot be generated at the same time. Effect, a pole (ρ ο 1 e) that cannot produce attenuation at the passband edge to increase the out of band rejection effect. Figure 4 shows a Hairpin-Comb filter. The direction of the resonator (41) included in this filter is the same. The total length of the resonator is 1/2 wavelength, and the length of the two turning sides is less than 1. / 4 wavelengths (4 2). Of this structure

Page 9 1223495 V. Description of the invention (4) The chirped wave filter is suitable for making narrow-band filters, that is, the center frequency of the crossover device with a bandwidth less than 1%. Please refer to George L. Matthaei, US Patent Number 5, 888, 942 (Mar. 30,1 999) 〇 [Contents of the Invention] 1 · The technical problem to be solved Although the conventional filter can increase the number of resonance poles, suppress the interference of the pitch ratio outside thunder, the number of poles increases, and the conductor signal is damaged. = 波 = The quality factor of the wave filter is reduced, and the insertion loss (Band ^ 仏 乜) is increased. In view of this, the present invention provides a narrow-passband filter suitable for microwave communication, which has a small size and extremely high passband selectivity, and is easy to be made into a narrowband (bandwidth less than 丨% filter center frequency) filter. And suitable for the use of high-quality factor (Q fact0F) South temperature superconducting thin film. 2. Technical means The structure of the present invention is like a comb-type (51) set of hairpins. The first resonance of the resonator in Fig. 5 is a resonance of the resonator divided by the resonator in Fig. 5 and the resonance between the resonators of the second comb-type resonator. The device is externally connected with 1 and 2 η, 2 and 2 η contact anti-parallel hairpin comb filters. The filter structure of the present invention is composed of two sets of anti-parallel hairpins. The openings of the first set of hairpin comb resonators are upward (5 2). The number of these two vibrators is the same, and the corresponding resonator shapes have the same distance (such as 53 and 54), but the directions are opposite (such as two groups, the interval η -1 and η + 1 (5 5) are resonant with other adjacent ones) The pitch of the device is different (1), and it is connected with a contact input terminal (5 6), and the last one has the same structure and the opposite direction (upside down).

1223495 V. Description of the invention (5) Contact output terminal (57). There are different geometrical notches at the turning points of the hairpin resonator, as shown in (58), (59), (60). The input and output terminals are connected to the first and last resonator parts, and are composed of a special geometric shape (61), which has the function of adjusting the frequency of the filter, which is defined here as the shape of the adjustment # (62); Changes with the electrical specifications of the different filters. 3. Efficacy The present invention has a small size (without increasing the number of resonance poles) and high performance (very high Λ suppresses this force) band-pass filter, which is particularly suitable for wireless communication §fL base station reception that requires high-speed data transmission. Filter write in the system. [Embodiment] In the following, we will specifically explain the preferred embodiments and the accompanying drawings. The touch-type anti-parallel hairpin comb filter has been designed, and a high-temperature superconducting film is used to make a superconducting filter suitable for the third generation (3G) mobile communication base station. The "contact anti-parallel hairpin comb filter of the present invention" is designed using Sorbet electromagnetic simulation software. Sonnet software is a planar full-waveform electromagnetic simulation software. Example 1 is a band-pass filter with 10 poles (po 1 e). The planar structure is shown in Figure 6. The signal of this filter enters the micro-strip (71) at the input end into the 'regulated sheet (7 3). Connected to the first resonator (7 5), the directions of the first to fifth resonators are the same; the sixth resonator (77) to the tenth resonator (7 8) are in the same direction, but are the same as the first One to fifth resonators 1223495

The direction is opposite; the tenth resonator is externally connected with an adjustment piece (4), and finally connected to the output terminal (72). '80, 81,8 2,83,84,85'86,87,88,89 for each hairpin resonator: = Appropriate structural modification to make the frequency response of the filter (Figure 7) meet the required specifications . / The second example of the present invention is a high-temperature superconducting filter manufactured by using a high-temperature superconducting film suitable for a 3G base station. This filter is 22 poles (composed of 22 resonators). The actual measured frequency response (nitrogen temperature) is shown in Figure 8. The waveform (frequency response) of this filter is not Tuning, and Out of band rejection> 90dB. As can be seen from the above description, the contact type anti-parallel hairpin comb filter made of the high-temperature superconducting film used in the present invention. It can increase the steepness of the passband edge (reducing the interference of radio waves outside the use frequency and increasing the effective use of frequency resources) ’to increase the industrial use value. Therefore, compared with the conventional band-pass filter, the miniaturization (not increasing the number of resonance poles) and high performance (high noise suppression capability) of the present invention are particularly suitable for wireless communication requiring high-speed data transmission. Filter in base station receiving system. The present invention has brought the performance manufacturing technology of the band-pass filter into a new realm.

Page 12 1223495 Simple description of the diagram [Simplified description of the diagram] Figure 1: The output and input ends of a four-pole linear structure filter are known as the connection type wiring structure diagram. Figure 2: A filter structure diagram of a typical typical hairpin resonator; the directions of the hairpin resonator alternately show opposite directions. Figure 3: A filter structure diagram of a conventional half-block (s e mi i 1 u m p) hairpin resonator. Figure 4 · Know the structure of a four-pole hairpin comb filter; the directions of its hairpin resonators are the same. Figure 5: Structure diagram of a contact anti-parallel hairpin comb filter according to the present invention; an adjustment piece is attached to the output and input ends and directly connected to the left and right resonators. The turning point of the cool resonance has different geometric structures. Figure 6: Structural design diagram of a 10-pole contact anti-parallel hairpin comb filter according to the present invention. Figure 7: The frequency response diagram of the filter of the computer analog simulation of the present invention; this figure is calculated based on the structure of Figure 6 using S ο η n e t software. Figure 8: Measured frequency response of a 22-pole contact anti-parallel hairpin comb filter according to the present invention; this filter is made of a high-temperature superconducting film, with out-of-band rejection > 90 dB; Sll, S22 are shown in the figure And S21 and other graphics. [Description of component symbols] 11 Resonator 71 Microstrip at the input end 12 Ground 7 2 Output end

1223495 Brief description of the diagram 13 Capacitor 73 tuned Ar / r ie chip 14 Capacitance 74 tuned / r / r ie chip 15 Ground 75 First resonator 16 Left and right ends 76 21 Resonator 77 Sixth resonator 31 Resonator Open π 78 Tenth resonator 32 Capacitance effect 33 Half block 80 Fold-back area of hairpin resonator 34 Resonator 81 Fold-out area of hairpin resonator 41 Resonator 82 Fold-out area of hairpin resonator 42 1/4 wavelength 83 Fold-back area of hairpin resonator 51 open π up 84 Fold-out area of hairpin resonator 52 open D down 85 Fold-back area of hairpin resonator 53 Same distance between resonators 86 hairpin type Folded area of resonators 54 Same distance between resonators 87 Folded area of hairpin resonators 55 Split pitch of resonators 88 Flush resonance Turn-back area of the device 56 input end 89 Turn-back area of the hairpin resonator Oscillator 57 output end 60 turn geometric shape σ 58 turn geometric shape D 61 special geometry shape 59 turn geometric shape V 62 tuning segment

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Claims (1)

1223495 VI. Scope of patent application [Scope of patent application] 1. A contact anti-parallel hairpin comb filter structure for microwave communication, consisting of: two sets of filter resonators, with two sets of opposite directions and a length of It consists of a half-wavelength hairpin resonator; a filter microstrip at the input end of the filter; a microstrip at the output of the filter; an input adjustment piece with one end connected to the input microstrip at the input and one end connected To the first resonator; An output adjustment piece, one end of which is connected to the micro-strip of the output end, and one end of which is connected to the last resonator. 2. If the filter structure of the first patent application scope, the number of resonators in the resonator group is at least 2 resonators. 3. For the filter structure of the first patent application scope, the resonators can be larger than two groups, but the directions of the adjacent two groups of resonators must be opposite. 4. For the filter structure in the scope of patent application No. 3, the heights of the adjacent groups of resonators can be adjusted as needed. 5. For the filter structure of the first patent application, the plane structure of the input adjustment piece and output adjustment piece is not fixed, and can be adjusted as needed. 6. If the filter structure of the scope of application for the first item of the patent, the turning point of the hairpin resonator can be designed with different geometric structures as required. 7. For the filter structure in the scope of patent application No. 1, the distance between the resonators in the two resonators with opposite directions may be different. 8. For the filter structure of the third scope of the patent application, in each resonator group Page 15 1223495 VI. The patent application scope of resonators can be different. Page 16