CN101038977A - Open loop coupling band-pass filter based on microstrip capacitive load - Google Patents
Open loop coupling band-pass filter based on microstrip capacitive load Download PDFInfo
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- CN101038977A CN101038977A CN 200610024741 CN200610024741A CN101038977A CN 101038977 A CN101038977 A CN 101038977A CN 200610024741 CN200610024741 CN 200610024741 CN 200610024741 A CN200610024741 A CN 200610024741A CN 101038977 A CN101038977 A CN 101038977A
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Abstract
The invention disclose an split-ring coupling band-pass filter based on microstrip capacitance load, which includes input feeding line, output feeding line and split-ring coupler, and which is characterized in that the terminal of each split-ring of the split-ring coupler is respectively cascaded connected to a pair of microstrip capacitance load which is disposed inward the split-ring. The invention reduce the area of the filter, by means of the character of slow wave, in a manner of cascaded connecting microstrip capacitance load to the terminal of the split-ring based on traditional split-ring coupling band-pass filter. Meanwhile, for the microstrip capacitance load effect, the bandgap suppression ratio of the filter greatly increases and the harmonic response of the traditional split-ring coupling band-pass filter can be eliminated. The invention can be used in any microwave frequency, and is fit for making substrate material for various microwave circuit.
Description
Technical field
The invention belongs to the technical field of microwave microstrip filter, particularly the structural design of open loop coupling band-pass filter.
Background technology
Filter is very important device in the wireless communication system, and low-cost and high performance various types of filters are indispensable in various radio frequencies and the microwave circuit always.Desirable filter characteristic should be undamped in passband, and big as far as possible decay is arranged in the forbidden band.Have very precipitous transition band filter for some requirement, generally can reach the performance that needs, also increase the outer decay of band simultaneously, but the increase of joint number will cause bigger insertion loss by the filter of cascade more piece.The filter of waveguiding structure, because its high Q value, advantages such as low insertion loss have obtained using widely in some narrow-band filterings, but the filter of waveguiding structure, the difficulty of processing height, machining accuracy is poor, often need follow-up manual debugging, therefore cause cost higher.
The microstrip coupled band pass filter of open circuit ring is to be proposed first in nineteen ninety-five by Jia-Sheng Hong, and has obtained using widely in the plane microwave circuit.The filter of the type has good frequency selectivity, and area is less, just can realize on the common printed circuit board technology, need not advantages such as through hole ground connection.But less at this filter at attenuation outside a channel, the decay about 4dB is particularly only arranged at the second harmonic place, can not satisfy the needs of practical application far away, often need to add low pass filter and suppress harmonic wave.
Fig. 1 has shown that traditional open circuit encircles the structure chart of microstrip coupled band pass filter, and as we can see from the figure, this coupling filter is by two open circuit resonant ring symmetrical coupled, and adopts asymmetrical 50 Ω input and output feeder lines.The microstrip coupled band pass filter of this open circuit ring, the work centre frequency is 1.8GHz, uses the microwave backing material, and relative dielectric constant is 2.65, and thickness is 1mm, and the length of open circuit coupling loop is 56mm, is 1/2nd guide wavelengths of operating frequency.Fig. 2 is the emulation of filter and the frequency response chart of test for this reason.Among the figure, S21 is the transmission characteristic of this filter, leads to in-band insertion loss less than 2.7dB (comprising two SMA connectors); S11 is the stationary wave characteristic of this filter, and all greater than 12.6dB, at the second harmonic place of operating frequency, minimum attenuation outside a channel is 12dB in free transmission range.This shows that the microstrip coupled band pass filter of this open circuit ring has good filtering characteristic in passband.But because the parasitic passband effect of microstrip circuit, it is less to decay at the second harmonic place, can not well satisfy needs and application in the side circuit.
Summary of the invention:
The objective of the invention is to overcome the prior art above shortcomings, a kind of little band open loop coupling band-pass filter with harmonic restraining function is proposed, this open loop coupling band-pass filter is in the open circuit ring, increase microstrip capacitive load, make it under the situation that does not influence the passband internal characteristic, can increase the outer inhibition degree of filter band, simultaneously, the area of this filter also reduces greatly.
The technical scheme of technical solution problem of the present invention is as follows:
A kind of open loop coupling band-pass filter based on microstrip capacitive load, comprise incoming feeder, output feeder and open circuit loop coupling device, it is characterized in that the terminal of each open circuit ring of open circuit loop coupling device is a pair of microstrip capacitive load of cascade respectively, it is inner that described microstrip capacitive load is positioned at the open circuit ring.
Described input and output feeder line live width is 50 Ω characteristic line breadths, adopts asymmetric feeder line, also can adopt symmetrical feeder line.
Microstrip capacitive load size in each open circuit ring is identical, and the size of described microstrip capacitive load adapts with the inner area of ring of opening a way.
The live width of described open circuit ring is 50 Ω characteristic line breadths, and resonator length is because the load capacitance effect of little band is reduced to about 1/4th of band pass filter centre frequency wavelength.And the open circuit ring total length of the logical coupler of tradition open circuit endless belt is 1/2nd of an operating frequency.
Described open circuit ring terminal coupling gap and two coupling gaps of opening a way between the ring with microstrip capacitive load are decided on concrete filter center frequency and substrate.
By above disclosed technical scheme as can be known, beneficial effect of the present invention is as follows: band is outer to be suppressed and reduces the filter area.
The present invention is based on the open loop coupling band-pass filter of microstrip capacitive load, on the basis of traditional open loop coupling band-pass filter,, rely on the characteristic of its slow wave to reach the effect that reduces the filter area at open circuit ring terminal cascade microstrip capacitive load.Meanwhile, eliminated the harmonic response that traditional open circuit loop coupling Datong District filter has because the load capacitance effect of little band makes the forbidden band inhibition degree of this filter increase greatly.The present invention can be applicable to any microwave frequency, and the backing material that is fit to various microwave circuits is made.
Description of drawings
Fig. 1 is traditional open loop coupling band-pass filter topology layout schematic diagram;
Fig. 2 is traditional open loop coupling band-pass filter frequency response chart of 900MHz for centre frequency;
Fig. 3 is the open loop coupling band-pass filter topology layout schematic diagram based on microstrip capacitive load of the present invention;
Fig. 4 is the open loop coupling band-pass filter frequency response chart based on microstrip capacitive load of 900MHz for centre frequency of the present invention;
More than in each frequency response chart, S21 represents the transfer curve of this filter of drawing according to the analogue value, the transfer curve of this filter that S21 ' expression is drawn according to measured value.
Embodiment
The present invention design based on the open loop coupling band-pass filter embodiment of microstrip capacitive load and be described in detail as follows, it is 2.65 that described embodiment is produced on dielectric constant, thickness is on the microwave substrate of 1mm, the centre frequency of band pass filter is 900MHz.
As shown in Figure 3, the open loop coupling band-pass filter based on microstrip capacitive load of the present invention's design comprises incoming feeder 31 and output feeder 34, based on the open circuit loop coupling device 32 and 33 of microstrip capacitive load.The present invention is on the basis of as shown in Figure 1 traditional open loop coupling band-pass filter, respectively in the terminal of loop coupling device 12,13 of opening a way, each cascade two microstrip capacitive loads, microstrip capacitive load is positioned at the inside of open circuit loop coupling device, does not influence the coupling between the open circuit loop coupling device.Because the slow wave effect that little bringing onto load has can make the area of this filter reduce greatly, embodiment shown in the present is an example, and area is half of traditional open loop coupling band-pass filter.Because the microstrip capacitive load effect has been eliminated harmonic wave spurious response, increased the inhibition degree in forbidden band simultaneously.Fig. 4 has shown the frequency response chart based on the open loop coupling band-pass filter of microstrip capacitive load of emulation and test, compare with the frequency response chart of traditional open loop coupling band-pass filter shown in Figure 2: traditional open loop coupling band-pass filter, at 2 order harmonics 1800MHz places, because the influence of ghost effect, only there is the harmonic wave inhibition degree of 4dB at this place, can not satisfy the requirement of actual use far away, and improved the forbidden decay of 24dB all greater than 28dB based on open loop coupling band-pass filter decay in the frequency range from 1GHz to 3GHz in last forbidden band of microstrip capacitive load; Insertion loss in the passband is 2.8dB, than the insertion loss of traditional open loop coupling band-pass filter big 1.4dB, this mainly is because the loss of microstrip capacitive load causes.
The present invention is based on the open loop coupling band-pass filter of microstrip capacitive load as shown in Figure 3, the live width of input, output 31,34 is 2.7mm, is 50 Ω characteristic line breadths.The live width of open circuit ring 32,33 is 50 Ω characteristic line breadth 2.7mm too.The size of microstrip capacitive load is 10.5mm * 9.9mm, and the microstrip capacitive load coupling gap is 0.3mm, and the coupling gap between the open circuit ring 32 and 33 is 0.3mm.The size of whole open loop coupling band-pass filter based on microstrip capacitive load is 26mm * 33.1mm, the size of tradition open loop coupling band-pass filter is 36.5mm * 53.2mm, and filter area of the present invention only is 45% of traditional open loop coupling band-pass filter area.
Claims (4)
1. open loop coupling band-pass filter based on microstrip capacitive load, comprise incoming feeder, output feeder and open circuit loop coupling device, it is characterized in that, the terminal of each open circuit ring of open circuit loop coupling device is a pair of microstrip capacitive load of cascade respectively, and it is inner that described microstrip capacitive load is positioned at the open circuit ring.
2. open loop coupling band-pass filter according to claim 1 is characterized in that, the microstrip capacitive load size in each open circuit ring is identical, and the size of described microstrip capacitive load adapts with the inner area of ring of opening a way.
3. open loop coupling band-pass filter according to claim 1 is characterized in that, described input and output feeder line live width is 50 Ω characteristic line breadths, is asymmetric feeder line or symmetrical feeder line.
4. open loop coupling band-pass filter according to claim 1 is characterized in that, the live width of described open circuit ring is 50 Ω characteristic line breadths, and total length is 1/4th of a band pass filter centre frequency guide wavelength.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN 200610024741 CN101038977A (en) | 2006-03-16 | 2006-03-16 | Open loop coupling band-pass filter based on microstrip capacitive load |
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| Application Number | Priority Date | Filing Date | Title |
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| CN 200610024741 CN101038977A (en) | 2006-03-16 | 2006-03-16 | Open loop coupling band-pass filter based on microstrip capacitive load |
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| CN101038977A true CN101038977A (en) | 2007-09-19 |
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| CN 200610024741 Pending CN101038977A (en) | 2006-03-16 | 2006-03-16 | Open loop coupling band-pass filter based on microstrip capacitive load |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101894995A (en) * | 2010-05-19 | 2010-11-24 | 华南理工大学 | Radio frequency electrically adjusted band-pass filter with constant absolute bandwidth |
| CN101894992A (en) * | 2010-07-26 | 2010-11-24 | 天津职业技术师范大学 | Microstrip meander line open loop coupling dual-mode band-pass filter |
| CN101667671B (en) * | 2009-08-31 | 2012-07-04 | 东南大学 | Microstrip dual-mode filter with features of wide stop band and low spurious |
| CN101777688B (en) * | 2010-01-11 | 2013-04-17 | 南通大学 | Microwave terminal short circuit half-wavelength tunable resonator and microwave tunable filter manufactured by same |
| CN103647121A (en) * | 2013-12-09 | 2014-03-19 | 中国电子科技集团公司第四十一研究所 | Broadband matching narrowband filter circuit |
| CN103779638A (en) * | 2014-01-15 | 2014-05-07 | 中国计量学院 | Magnetoelectric double-adjustable-ultra-wide-band band-pass filter of symmetrical C-type microstrip structure and method |
-
2006
- 2006-03-16 CN CN 200610024741 patent/CN101038977A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101667671B (en) * | 2009-08-31 | 2012-07-04 | 东南大学 | Microstrip dual-mode filter with features of wide stop band and low spurious |
| CN101777688B (en) * | 2010-01-11 | 2013-04-17 | 南通大学 | Microwave terminal short circuit half-wavelength tunable resonator and microwave tunable filter manufactured by same |
| CN101894995A (en) * | 2010-05-19 | 2010-11-24 | 华南理工大学 | Radio frequency electrically adjusted band-pass filter with constant absolute bandwidth |
| CN101894995B (en) * | 2010-05-19 | 2013-07-24 | 华南理工大学 | Radio frequency electrically adjusted band-pass filter with constant absolute bandwidth |
| CN101894992A (en) * | 2010-07-26 | 2010-11-24 | 天津职业技术师范大学 | Microstrip meander line open loop coupling dual-mode band-pass filter |
| CN103647121A (en) * | 2013-12-09 | 2014-03-19 | 中国电子科技集团公司第四十一研究所 | Broadband matching narrowband filter circuit |
| CN103647121B (en) * | 2013-12-09 | 2015-10-28 | 中国电子科技集团公司第四十一研究所 | A kind of narrow-band filtering circuit of Broadband Matching |
| CN103779638A (en) * | 2014-01-15 | 2014-05-07 | 中国计量学院 | Magnetoelectric double-adjustable-ultra-wide-band band-pass filter of symmetrical C-type microstrip structure and method |
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Open date: 20070919 |