CN108493530A - A kind of novel limit is with adjustable ultra wide band bandpass filter - Google Patents

Abstract

The invention discloses a novel band-limiting adjustable ultra-wideband band-pass filter. The filter uses the inherent zero point of the multimode resonator to form a band limit in the ultra-wideband bandpass filter, and combines the step impedance resonance structure with the stub loading resonance structure to form a new T-shaped multimode resonator. Capacitors are connected in parallel at the impedance transformation of the resonant structure to increase the number of resonant modes, and a varactor is loaded at the resonator terminal, and the varactor is used to adjust the zero point position in the band to form an adjustable band-limiting characteristic, mainly including the upper microstrip structure, the middle layer The dielectric plate and the lower ground metal have the characteristics of simple structure, miniaturization, and good characteristics, which can overcome the shortcomings of insufficient selectivity of filters based on multimode resonator design, achieve good selectivity and harmonic suppression, and are easy to implement Circuit integration and system packaging.

Description

A Novel Band-Limited Tunable Ultra-Wideband Bandpass Filter

technical field

The invention relates to the field of adjustable circuit theory, in particular to a novel band-limited adjustable ultra-wideband band-pass filter.

Background technique

Since the U.S. Federal Communications Commission (FCC) issued the application license of ultra-wideband (Ultra-wideband, UWB) technology in the field of short-distance wireless communication on February 1, 2002, it has promoted the marketization process of broadband/ultra-wideband technology products, This makes the research of broadband/ultra-wideband system and its devices get more attention. Ultra-wideband (3.1GHz-10.6GHz) covers a very wide range and overlaps with the range of other wireless services (such as 4.2-4.4GHz for aviation radio navigation (ARNS), 5.8GHz for wireless area local area network (WLAN), and 8.5 -10.68GHz radar frequency band (ITU) of the International Telecommunication Union. These wireless service frequency bands may interfere with ultra-wideband signals, resulting in signal distortion and desensitization. In order to better use this frequency band, it is necessary to use filters to contain these interferences Indispensable. An effective solution to solve this problem is to realize a notch characteristic in the passband of the ultra-wideband bandpass filter to accurately filter out unwanted frequency bands. In recent years, many scholars have been working on In the study of ultra-wideband bandpass filters with adjustable band limit, such as literature 1 (SongK, Xue Q. Inductance-Loaded Y-Shaped Resonators and Their Applications to Filters[J]. IEEE Transactions on Microwave Theory&Techniques, 2010, 58(4) :978-984) and literature 2 (Xu J, Wu W, Kang W, et al.Compact UWB Bandpass Filter With a Notched Band Using Radial Stub Loaded Resonator[J].IEEE Microwave and Wireless Components Letters,2012,22(7): 351-353) have introduced the structures of several band-limited tunable filters in detail. The disadvantages of the previously designed band-limited tunable filter structures are: (1) the bandwidth adjustment range is limited; (2) the adjustment In the process, the performance of the filter is unstable; (3) The varactor diode introduces parasitic parameters, causing unnecessary resonance, and the power supply increases the circuit volume.

Contents of the invention

The purpose of the present invention is to provide a novel band-limiting adjustable ultra-wideband band-pass filter, so as to achieve good selectivity and harmonic suppression effect, and is easy to realize circuit integration and system packaging.

The technical solution to realize the object of the present invention is: a novel band-limiting adjustable ultra-wideband bandpass filter, comprising an upper microstrip structure, a middle layer dielectric plate and a lower ground metal; the upper layer microstrip structure is attached to the middle layer dielectric substrate surface, the ground metal is attached to the lower surface of the intermediate layer dielectric substrate; the reconfigurable first port and the second port are located on the upper layer of the dielectric substrate, the first port is located on the side of the dielectric substrate, and the second port is located on the dielectric substrate On the other side of the substrate; two 50-ohm microstrip lines are respectively connected to the corresponding two ports. These two 50-ohm microstrip lines are respectively the first microstrip line and the second microstrip line. The two The microstrip lines are parallel to each other.

The first port is connected to one end of the first parallel coupled line through the first microstrip line, the other end of the first parallel coupled line is connected to the second parallel coupled line, and the second port is connected to the first parallel coupled line through the second microstrip line. The other ends of the two parallel coupling lines are connected; the junction of the first parallel coupling line and the second parallel coupling line is connected to the fourth microstrip line through the third microstrip line; the first capacitor is connected to the fourth microstrip line and the third microstrip line One end connected to the strip line, the other end of the first capacitor is grounded; the second capacitor is connected to one end connected to the fourth microstrip line and the third microstrip line, and the other end of the first capacitor is grounded; the first varactor is connected to the fourth microstrip line One end of the stripline away from the third microstrip line. The first DC blocking capacitor is embedded in the first microstrip line, and the second DC blocking capacitor is embedded in the second microstrip line.

The value ranges of the widths of the first microstrip line, the second microstrip line, the first parallel coupled line, the second parallel coupled line, the third microstrip line and the fourth microstrip line are all 0.15-15 mm; The coupling distances of the first parallel coupling lines and the second parallel coupling lines both range from 0.15 mm to 0.6 mm.

The first microstrip line and the second microstrip line have the same length l ₁ and width w ₁ .

The first parallel coupled lines and the second parallel coupled lines have the same coupling spacing Δl, and the first parallel coupled lines and the second parallel coupled lines have the same length l ₂ and width w ₂ .

The length _l2 of the first parallel coupled line and the second parallel coupled line is a quarter of the wavelength of the center frequency of the tunable filter; the width _w2 of the first parallel coupled line and the second parallel coupled line is 0.41 mm; the width w ₃ of the third transmission line is 4.48 mm; the width w ₄ of the fourth transmission line is 0.84 mm; the coupling distance Δl between the first parallel coupling line and the second parallel coupling line is 0.15 mm.

The capacitance values of the first DC blocking capacitor and the second DC blocking capacitor are the same, and the value range is 20pF to 150pF; the capacitance values of the first capacitor and the second capacitor are the same, and the value range is 0.5pF ~1pF.

The dielectric constant of the intermediate layer dielectric plate ranges from 2 to 16, and the height of the dielectric substrate ranges from 0.1 to 4 mm.

Compared with the prior art, the present invention has the following advantages: 1) there is no need to introduce additional resonators for band limiting, it is independent of the size of the passband bandwidth, and keeps the constancy of the passband bandwidth, thereby simplifying the ultra-wideband bandpass filter structure, Realize miniaturization; 2) The introduction of a pair of 1/4 parallel coupled transmission lines as the feeder part of the filter successfully introduces two transmission zeros outside the band, improving the shortcoming of insufficient selectivity of the filter based on the multimode resonator design, and realizing Good selectivity and harmonic suppression effect.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is a schematic diagram of the band-limited adjustable ultra-wideband band-pass filter of the present invention.

Fig. 2 is an equivalent circuit diagram of a band-limited adjustable ultra-wideband band-pass filter.

Fig. 3 is a graph showing transmission characteristics and return loss of the present invention.

Fig. 4 is a graph of the group delay characteristic of the present invention.

Detailed ways

In conjunction with the accompanying drawings, the present invention discloses an ultra-wideband bandpass filter with adjustable band limitation, which comprises an upper layer microstrip structure, an intermediate layer dielectric plate and a lower layer grounded metal; the upper layer microstrip structure is attached to the upper surface of the intermediate layer dielectric substrate, The ground metal is attached to the lower surface of the interlayer dielectric substrate;

The first port P1 and the second port P2 of the filter are located on the upper layer of the dielectric substrate, the first port is located on one side of the dielectric substrate, and the second port is located on the other side of the dielectric substrate; two 50-ohm microstrips The lines are respectively connected to the corresponding two ports, and the two 50-ohm microstrip lines are respectively the first microstrip line 1 and the second microstrip line 2, and the two microstrip lines are parallel to each other;

The first port P1 is connected to one end of the first parallel coupled line 3 through the first microstrip line 1, the other end of the first parallel coupled line 3 is connected to the second parallel coupled line 4, and the second port P2 is connected to the second microstrip line through the second microstrip line. The strip line 2 is connected to the other end of the second parallel coupled line 4; the junction of the first parallel coupled line 3 and the second parallel coupled line 4 is connected to the fourth microstrip line 6 through the third microstrip line 5;

The first capacitor 9 is connected to one end of the fourth microstrip line 6 connected to the third microstrip line 5, and the other end of the first capacitor 9 is grounded; the second capacitor 10 is connected to the fourth microstrip line 6 and the third microstrip line 5 One end connected, the other end of the second capacitor 10 is grounded; the first varactor 11 is connected to the end of the fourth microstrip line away from the third microstrip line. The first DC blocking capacitor 7 is embedded in the first microstrip line 1 , and the second DC blocking capacitor 8 is embedded in the second microstrip line 2 .

Two 50-ohm microstrip lines have the same length and width, the first parallel coupled line 3 and the second parallel coupled line 4 have the same coupling spacing, and the first parallel coupled line 3 and the second parallel coupled line 4 have the same length and width.

The first parallel coupled line 3, the length of the second parallel coupled line 4 is a quarter of the wavelength of the center frequency of the adjustable filter, the first parallel coupled line 3, the second parallel coupled line 4, the first transmission line 1 The widths of the second transmission line 2, the third transmission line 5, and the fourth transmission line 6 are all 0.15-15 mm, and the coupling distances of the first parallel coupling lines 3 and the second parallel coupling lines 4 are all 0.15-0.6 mm.

The width of the first parallel coupling line 3 and the second parallel coupling line 4 is 0.41mm, the width of the third transmission line 5 is 4.48mm, the width of the fourth transmission line 6 is 0.84mm, the first parallel coupling line The coupling pitches of the line 3 and the fourth parallel coupling line 4 are both 0.15 mm.

The two DC blocking capacitors have the same capacitance value of 20pF-150pF, and the first capacitor 9 and the second capacitor 10 have the same capacitance value of 0.5pF-1pF.

The dielectric constant of the dielectric substrate is 2-16, and the height of the dielectric substrate is 0.1-4mm.

Specifically, the width of the first microstrip line 1, the second microstrip line 2, the first parallel coupled line 3, the second parallel coupled line 4, the third microstrip line 5 and the fourth microstrip line 6 The value ranges are 0.15-15mm; the coupling distances of the first parallel coupling line 3 and the second parallel coupling line 4 are all in the range of 0.15-0.6mm. The first microstrip line 1 and the second microstrip line 2 have the same length l ₁ and width w ₁ . The first parallel coupled lines 3 and the second parallel coupled lines 4 have the same coupling spacing Δl, and the first parallel coupled lines 3 and the second parallel coupled lines 4 have the same length l ₂ and width w ₂ . The length ₁₂ of the first parallel coupling line 3 and the second parallel coupling line 4 is 1/4 of the wavelength of the center frequency of the tunable filter; the first parallel coupling line 3 and the second parallel coupling line 4 The width w ₂ is 0.41 mm; the width w ₃ of the third transmission line 5 is 4.48 mm; the width w ₄ of the fourth transmission line 6 is 0.84 mm; the first parallel coupling line 3 and the second parallel coupling line 4 The coupling distance Δl is 0.15mm. The capacitance values of the first DC blocking capacitor 7 and the second DC blocking capacitor 8 are the same, and the value range is 20pF to 150pF; the capacitance values of the first capacitor 9 and the second capacitor 10 are the same, and the value range is Both are 0.5pF ~ 1pF. The dielectric constant of the intermediate layer dielectric plate ranges from 2 to 16, and the height of the dielectric substrate ranges from 0.1 to 4 mm.

The present invention does not need to introduce additional resonators for band limitation, is independent of the bandwidth of the passband, and maintains the constancy of the bandwidth of the passband, thereby simplifying the structure of the ultra-wideband bandpass filter and realizing miniaturization.

Below in conjunction with embodiment the present invention is described in further detail.

Example

The present invention utilizes the inherent zero point of the multimode resonator to form a band-limiting method in an ultra-wideband bandpass filter, and combines a step impedance structure with a branch loading structure to form a novel T-shaped multimode resonator with a step impedance structure Capacitors are connected in parallel at the impedance transformation of the resonator to increase the number of resonance modes, and a varactor is loaded at the resonator terminal, and the varactor is used to adjust the zero position in the band to form an adjustable band-limiting characteristic. The introduction of a pair of quarter parallel coupled transmission lines as the feeder part of the filter successfully introduces two transmission zeros outside the band, improving the shortcoming of insufficient selectivity of the filter based on the multimode resonator design, and realizing the miniaturization of the filter , and good selectivity and harmonic suppression effects. The size of the entire dielectric substrate is 79.3mm*30mm*1mm, and the dielectric constant of the dielectric substrate is 2.2. In Fig. 1, the length of the first transmission line 1 and the second transmission line 2 is 17 mm, and the width is 3.03 mm. The third transmission line 5 has a width of 4.48 mm and a length of 26.6 mm, and the fourth transmission line 6 has a width of 0.84 mm and a length of 13.4 mm. The two DC-blocking capacitors 1 and 2 have the same capacitance value of 100pF, the first capacitor 9 and the second capacitor 10 have the same capacitance value of 0.6pF, and the first varactor 11 is SMV2019- 079LF.

Fig. 1 is the principle diagram of described band-limiting adjustable ultra-wideband band-pass filter, and equivalent circuit is as shown in Fig. 2, and the transmission line matrix of known one end loading capacitance and the transmission line matrix of parallel capacitance is:

Suppose the impedance seen from point B in Figure 2 to the loaded branch is Z _ins,B , then

Let the impedance seen from point A to the loaded branch be Z _{ins, A}

Therefore, if the input impedance Z _ins,A of the stub is set to 0, then the resonance zero point f _tz of the stub can be obtained, and the relational expression it satisfies is:

Fig. 3 is the transmission characteristic curve of the tunable filter, and Fig. 4 is the group delay characteristic curve of the tunable filter. Bandlimiting can be adjusted from 2.32GHz to 3.00GHz (22%) while maintaining a 3-dB absolute bandwidth between 2.45GHz and 2.5GHz and a relative bandwidth between 89.2% and 98%. The out-of-band harmonic suppression is greater than 15dB, and the in-band group delay is less than 5ns.

The present invention has the characteristics of simple structure, miniaturization, good characteristics, etc., can overcome the shortcoming of insufficient selectivity of the filter based on multimode resonator design, realize good selectivity and harmonic suppression effect, and is easy to realize circuit integration and system packaging .

Claims (7)

1. a novel band-limiting adjustable ultra-wideband band-pass filter, is characterized in that, comprises upper strata microstrip structure, middle layer dielectric board and lower ground metal; Described upper strata microstrip structure is attached to the bottom of described middle layer dielectric board On the upper surface, the lower ground metal is attached to the lower surface of the intermediate dielectric board; The first port (P1) and the second port (P2) of the filter are all located on the upper layer of the intermediate layer dielectric board, the first port (P1) is located on one side of the dielectric board, and the second port (P2) Located on the other side of the dielectric board; two 50-ohm microstrip lines are respectively connected to the corresponding two ports, and these two 50-ohm microstrip lines are respectively the first microstrip line (1) and the second microstrip line (2), and the two microstrip lines are parallel to each other; the first port (P1) is connected to one end of the first parallel coupling line (3) through the first microstrip line (1), and the first parallel coupling line (3) ) is connected to one end of the second parallel coupled line (4), and the second port (P2) is connected to the other end of the second parallel coupled line (4) through the second microstrip line (2); the first The junction of the parallel coupling line (3) and the second parallel coupling line (4) is connected to the fourth microstrip line (6) through the third microstrip line (5); One end of the first capacitor (9) is connected to the joint of the fourth microstrip line (6) and the third microstrip line (5), and the other end of the first capacitor (9) is grounded; one end of the second capacitor (10) Connected to the junction of the fourth microstrip line (6) and the third microstrip line (5), the other end of the second capacitor (10) is grounded; the first varactor (11) is connected to the fourth microstrip line One end away from the third microstrip line; the first DC blocking capacitor (7) is embedded in the first microstrip line (1), and the second DC blocking capacitor (8) is embedded in the second microstrip line (2). 2. novel band-limiting adjustable ultra-wideband band-pass filter according to claim 1, is characterized in that, described first microstrip line (1), the second microstrip line (2), the first parallel coupling line (3), the value range of the width of the second parallel coupling line (4), the third microstrip line (5) and the fourth microstrip line (6) is 0.15～15mm; the first parallel coupling line ( 3) and the coupling distance of the second parallel coupling line (4) both range from 0.15 to 0.6 mm. 3. novel band-limiting adjustable ultra wideband band-pass filter according to claim 1, is characterized in that, described first microstrip line (1) and the second microstrip line (2) have identical length l ₁ and width w ₁ . 4. novel band-limiting adjustable ultra-wideband band-pass filter according to claim 1, is characterized in that, described first parallel coupling line (3) and second parallel coupling line (4) have identical coupling distance Δl , and the first parallel coupling line (3) and the second parallel coupling line (4) have the same length l ₂ and width w ₂ . 5. according to claim 2,3 or 4 described novel band-limiting adjustable ultra-wideband band-pass filter, it is characterized in that, described first parallel coupling line (3) and the second parallel coupling line (4) The length _l2 is a quarter of the wavelength of the center frequency of the tunable filter; the width _w2 of the first parallel coupling line (3) and the second parallel coupling line (4) is 0.41mm; the third transmission line The width w ₃ of (5) is 4.48mm; the width w ₄ of the fourth transmission line (6) is 0.84mm; the coupling spacing Δl of the first parallel coupling line (3) and the second parallel coupling line (4) 0.15mm. 6. according to the novel band-limiting adjustable ultra-wideband band-pass filter described in claim 1, it is characterized in that, the capacity value of the first DC blocking capacitor (7), the second DC blocking capacitor (8) is identical, And the value range is 20pF-150pF; the capacitance value of the first capacitor (9) and the second capacitor (10) are the same, and the value range is 0.5pF-1pF. 7. According to the novel band-limiting adjustable ultra-wideband band-pass filter described in claim 1, it is characterized in that, the value range of the dielectric constant of the intermediate layer dielectric plate is 2～16, and the value range of the height of the dielectric substrate The range is 0.1 ~ 4mm.