CN201523059U

CN201523059U - Double-ring cascade type dual-mode band-pass filter of stepped impedance resonator

Info

Publication number: CN201523059U
Application number: CN2009202314968U
Authority: CN
Inventors: 张雷; 洪伟; 周健义
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2009-08-31
Filing date: 2009-08-31
Publication date: 2010-07-07
Anticipated expiration: 2019-08-31

Abstract

A double-ring cascade type dual-mode band-pass filter of a stepped impedance resonator is manufactured on the basis of a microwave dielectric substrate, an L-shaped coupling structure (2) of an input port and an L-shaped coupling structure (4) of an output port are respectively arranged on the outer sides of diagonal lines of a square stepped impedance resonator SIR (1), and two ends of a microstrip connecting wire (3) are respectively connected to the L-shaped coupling structure (2) of the input port on the outer side of one adjacent square stepped impedance resonator SIR (1) and the L-shaped coupling structure of the output port on the outer side of one nonadjacent square stepped impedance resonator SIR (1). The L-shaped coupling structure (2) of the input port and the L-shaped coupling structure (4) of the output port of the nonadjacent square stepped impedance resonator SIR (1) are respectively connected with input and output 50-ohm feeder lines (6), and perturbation elements (5) are arranged at inner corners of each square stepped impedance resonator SIR (1). The double-ring cascade type dual-mode band-pass filter can obtain higher port coupling compared with the conventional microstrip so as to reduce insert loss, and is provided with a steep transitional belt and a wide spurious-free stop band simultaneously.

Description

Step electric impedance resonator dicyclo cascade connection type bimodule band-pass filter

Technical field

The utility model can be applicable to the radio-frequency front-end of mobile communication system, and can significantly increase the outer spuious inhibition degree of band and the resistance band of system, and in passband, keep low insertion loss, be a kind of high performance microwave band-pass filter.

Background technology

The present mobile communication technology system has proposed more and more higher requirement to the performance of radio-frequency front-end, and is positioned at transmitting power and the signal to noise ratio that radio frequency filter foremost has influence on system to a great extent.Micro-strip dual-mode filter with its low cost, be easy to processing and implementation is flexible etc. that advantage gets most of the attention.Because the double tunning characteristic that himself has, the filter of the identical exponent number of volume ratio reduces by half.But it is bigger that common micro-strip dual-mode filter inserts loss, and its intrinsic second harmonic can worsen the spuious suppression characteristic of filter, and cause the asymmetric of near side (ns) band response.Above-mentioned drawbacks limit the application of common micro-strip dual-mode filter.

In order to suppress the spurious response of circuited microstrip loop filter, adopt slow wave structure usually, have the resonator of mode suppression such as trap structures such as DGS and spurline and employing.But first kind of technology can reduce the bandwidth of filter, then then can introduce additional structure for two kinds, not only makes circuit scale become big, and worsens the transmission characteristic in the passband, increases and inserts loss.The technology that also has forms higher order filter with two two film resonators with the microstrip line cascade, but this microstrip line can cause additional spurious response with the coupled structure that is attached thereto, and worsens the inside and outside frequency response characteristic of passband.

Summary of the invention

Technical problem: the utility model proposes a kind of step electric impedance resonator dicyclo cascade connection type bimodule band-pass filter, this structure has the characteristics such as loss low, spuious inhibition degree height and resistance band are big of inserting.Simple in structure, be easy to make processing and integrated with planar circuit, be applicable to various radio frequency front.

Technical scheme: the utility model has proposed a kind of novel cascade micro-strip dual-mode filter on the basis of dual-mode resonator.This filter can obtain the port coupling amount bigger than the little band of tradition, inserts loss thereby reduce.Simultaneously, the distinctive coupled structure of this filter can the parasitic spurious response of very effective inhibition, increases resistance band.In addition, this filter construction is simple, is easy to extensive manufacturing, is particularly useful for the design of radio frequency front.

Step electric impedance resonator dicyclo cascade connection type bimodule band-pass filter of the present utility model is produced on the microwave-medium substrate, the SIR square annular resonance device that comprises two symmetries, each SIR square annular resonance device comprise L shaped coupled structure, perturbation element and 50 ohm of input/output port feeder lines of a L shaped coupled structure of input port, an output port; The L shaped coupled structure of L shaped coupled structure of input port and output port lays respectively at the diagonal outside of SIR square annular resonance device, the two ends of little band connecting line connect the L shaped coupled structure of input port in an adjacent SIR square annular resonance device outside and the L shaped coupled structure of the output port outside another SIR square annular resonance device respectively, and the L shaped coupled structure of non-conterminous L shaped coupled structure of SIR square annular resonance device input port and output port links to each other with 50 ohm of input and output feeder lines respectively; The perturbation element is positioned on the SIR square annular resonance device interior angle.

The square annular resonance chamber is that girth is the sealing microstrip line of a wavelength on the centre frequency.

The L shaped coupled structure of input port is made of the microstrip line of terminal open circuit, and its bending direction is consistent with the outer of square annular resonance device.

The perturbation element is made of square microband paste.

Beneficial effect:

1. improve the port coupling amount of band pass filter, reduce in-band insertion loss.Need the occasion of close coupling, can overcome the restriction on the too small manufacturing process of bringing in coupling slit.

2. utilize the second harmonic of the complete rejects trap of coupled structure, thereby improve the response symmetry of near side (ns) band.

3. have precipitous excessive band and very wide no spuious resistance band.

4. simple in structure, adopt the common plane printed circuit technology to make, good reproducibility is fit to standardized production and integrated with various planar circuits.

Description of drawings

Fig. 1 is a L type coupled structure bimodulus microstrip bandpass filter schematic diagram.

L shaped coupled structure 4,

perturbed structure

5 and 50 ohm of input and output port feeder lines 6 of comprising the L shaped coupled structure 2 of SIR square annular resonance chamber 1, input port, little band connecting line 3, output port among the figure.

Fig. 2 is the near side (ns) band transmission coefficient measurement result of embodiment 1,

Fig. 3 is the near side (ns) band measurement of reflection-factor result of embodiment 1.

Embodiment

The utility model connects microstrip line based on cascade connection type bimodulus microstrip filter by the annular bimodulus micro-strip resonantor in SIR (step electric impedance resonator) side, L shaped microstrip coupled structure resonator and constitutes.

SIR side's annular micro-strip resonantor is made of the closed ring microstrip line.The micro belt line width at this resonator middle part is different with four jiaos micro belt line width, thereby constitutes the SIR resonator.On the diagonal of this structure, place square patch as the perturbation element, make to produce coupling between the above-mentioned a pair of degenerate mode.Adjust the big or small resonator of perturbation paster and the gap width between the coupling arm, can constitute the second order filter that satisfies certain performance requirement, make circuit scale dwindle.50 ohm microstrip input and output feeder lines directly are connected with L shaped coupled structure, and this coupled structure is done parallel coupling with SIR side's annular micro-strip resonantor.SIR side's annular micro-strip resonantor of two cascades then is connected with one section microstrip transmission line by L shaped coupled structure.

Regulate the microstrip line at resonator middle part and four jiaos micro belt line width ratio, can change the impedance ratio of SIR side's annular micro-strip resonantor, thereby change the frequency ratio of this resonator second harmonic and first-harmonic.When this frequency ratio was lower than common square annular resonance device, L shaped coupled structure can have bigger length satisfying under the condition that fully suppresses second harmonic.Like this, adopt L shaped coupled structure, SIR side's annular micro-strip resonantor just can obtain the coupling amount bigger than common square annular resonance device, lower insertion loss and wideer frequency band.Need can obtain the frequency response characteristic that needs by the length big or small and L shaped coupled structure that changes impedance ratio, perturbation element than the occasion of narrow-band.

Two SIR sides annular bimodulus micro-strip resonantors are connected through separately L shaped microstrip coupled structure and by one section microstrip transmission line, can constitute higher order filter.This microstrip line and the coupled structure that is attached thereto can cause additional spurious response.Adjust the relative position of L shaped microstrip coupled structure and SIR side annular bimodulus micro-strip resonantor, can change the position of near side (ns) band transmission zero in the frequency response separately of bimodulus micro-strip resonantor, offset spurious response, obtain very big no spuious resistance band.

This Filter Design is based on plane electric circuit technology, and little band edge mouth feed does not have any adjunct circuit, and volume is small and exquisite, and is simple in structure, is easy to produce.

This New type of S IR dicyclo cascade connection type bimodule band-pass filter is made up of L shaped coupled structure 4,

perturbed structure

5 and 50 ohm of input and output port feeder lines 6 of the L shaped coupled structure 2 of SIR square annular resonance chamber 1, input port, little band connecting line 3, output port.When design, should do following consideration:

1) bending direction of L shaped coupling arm should be consistent with the outer of square annular resonance device, thereby guarantee stiffness of coupling.

2) girth of the annular micro-strip resonantor in side should equal a wavelength of equal wide microstrip transmission line on the centre frequency.

3) length of L shaped coupling arm should be approximately equal to 1/8 wavelength of equal wide microstrip transmission line on the centre frequency, thereby guarantees that the transmission characteristic on the second harmonic frequency of square ring resonator has enough big inhibition.(4) by adjusting the length of the microstrip line that connects two L shaped coupled structures, can obtain the interior frequency transmission characteristic (5) of desirable passband by regulating the position that the relative position between L shaped coupling arm and the square annular resonance chamber, the gap size that is coupled and perturbation element area can change the bandwidth and the near side (ns) band transmission zero of filter, obtain the outer frequency transmission characteristic of desirable band.

Embodiment: based on the bimodulus microstrip bandpass filter of novel L type coupled structure, centre frequency is at 3.5GHz, and the 3dB relative bandwidth is 20%, and minimum insertion loss is 1.52dB in the passband.

Filter construction as shown in Figure 1.The dielectric substrate material that the median filter of this embodiment adopts is a TLX-8-0310 sheet material, and dielectric constant is 2.55, and the tangent angle loss is 0.002, and thickness is 0.7874mm.The broadband transmission coefficient of embodiment 1 and broadband measurement of reflection-factor result are respectively as Fig. 2～shown in Figure 3.

Claims

1. step electric impedance resonator dicyclo cascade connection type bimodule band-pass filter, it is characterized in that this filter is produced on the microwave-medium substrate, the SIR square annular resonance device (1) that comprises two symmetries, each SIR square annular resonance device (1) comprise L shaped coupled structure (4), perturbation element (5) and 50 ohm of input/output port feeder lines (6) of a L shaped coupled structure of input port (2), an output port; The L shaped coupled structure (4) of L shaped coupled structure of input port (2) and output port lays respectively at the diagonal outside of SIR square annular resonance device (1), the two ends of little band connecting line (3) connect the L shaped coupled structure of input port (2) in an adjacent SIR square annular resonance device (1) outside and the L shaped coupled structure (4) of the output port outside another SIR square annular resonance device (1) respectively, and the L shaped coupled structure (4) of L shaped coupled structure of non-conterminous SIR square annular resonance device (1) input port (2) and output port links to each other with 50 ohm of input and output feeder lines (6) respectively; Perturbation element (5) is positioned on SIR square annular resonance device (1) interior angle.

2. step electric impedance resonator dicyclo cascade connection type bimodule band-pass filter according to claim 1 is characterized by: square annular resonance chamber (1) is that girth is the sealing microstrip line of a wavelength on the centre frequency.

3. step electric impedance resonator dicyclo cascade connection type bimodule band-pass filter according to claim 2 is characterized by: the L shaped coupled structure of input port (2) is made of the microstrip line of terminal open circuit, and its bending direction is consistent with the outer of square annular resonance device (1).

4. step electric impedance resonator dicyclo cascade connection type bimodule band-pass filter according to claim 1, it is characterized by: perturbation element (3) is made of square microband paste.