CN101656342B - Hairpin-line bandpass filter and related frequency demultiplier thereof - Google Patents
Hairpin-line bandpass filter and related frequency demultiplier thereof Download PDFInfo
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- CN101656342B CN101656342B CN200810213652A CN200810213652A CN101656342B CN 101656342 B CN101656342 B CN 101656342B CN 200810213652 A CN200810213652 A CN 200810213652A CN 200810213652 A CN200810213652 A CN 200810213652A CN 101656342 B CN101656342 B CN 101656342B
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Abstract
The invention discloses a bandpass filter, which comprises a first microstrip end, a second microstrip end, and a plurality of resonators, wherein the first microstrip end is used for receiving a radio frequency signal; the second microstrip end is used for outputting a radio frequency filtering signal, and at least one resonant cavity is formed in the second microstrip end and is used for improving the rejection effect of the image frequency corresponding to the radio frequency filtering signal; and the plurality of resonators are arranged between the first microstrip end and the second microstrip end, and are used for performing bandpass filtering treatment on the radio frequency signal to generate the radio frequency filtering signal.
Description
[technical field]
The present invention is a kind of band pass filter and related frequency demultiplier thereof, refers to a kind of band pass filter and related frequency demultiplier thereof that promotes image frequency rejection effect especially.
[background technology]
In broadcast system, superheterodyne receiver (Super Heterodyne Receiver) is a kind of the most widely used receiver architecture, and it can simply be carried out carrier frequency tuning (being channel selection), filtering and signal and amplify.In superheterodyne receiver, signal receives through amplification, rf filtering, reduces to intermediate frequency, amplifies and filtering through one or more intermediate frequency from antenna, reduces to fundamental frequency at last and makes the signal demodulation process.Wherein, reduce to by radio frequency in the process of intermediate frequency, tend to receive the influence that image frequency (Image Frequency) is disturbed, cause follow-up signal to handle the generation problem.
Please refer to Fig. 1, Fig. 1 is the existing sketch map that is used for a frequency demultiplier 10 of a superheterodyne receiver.Frequency demultiplier 10 includes low noise amplifier 100,102, a receiving terminal 103, an image cancellation filter (Image RejectFilter) 104, one frequency mixer 106, a local oscillator (Local Oscillator) 108, one intermediate frequency low pass filter 110 and an intermediate frequency amplifier 112.The function mode of frequency demultiplier 10 is that this area tool knows that usually the knowledgeable knows, and below only sketches it.Radiofrequency signal V
RF1Receive the back by antenna and get into frequency demultiplier 10, after two-stage low noise amplifier 100,102 amplifies, become radiofrequency signal V
RF2Then, image cancellation filter 104 is via receiving terminal 103 received RF signal V
RF2, and filtering image frequency signal, to produce rf filtering signal VF
RF, be downconverted to the intermediate frequency frequency range through frequency mixer 106 again, and amplify back output intermediate-freuqncy signal V by 110 filtering of intermediate frequency low pass filter and intermediate frequency amplifier 112
IFWherein, image cancellation filter 104 is to be used for eliminating image frequency to disturb.The reason that image frequency produces is: two incoming frequencies | f
LO± f
IF|, all can produce frequency f in frequency mixer 106 outputs
IFWherein, frequency f
LOBe the oscillation signal frequency of local oscillator 108, and frequency f
IFBe intermediate-freuqncy signal V
IFFrequency.Therefore, in superheterodyne receiver, when being symmetrical in the signal process frequency mixer 106 of local oscillated signal both sides on the frequency spectrum; Can enter into identical frequency band; Form a kind of interference signal, reduced signal to noise ratio (Signal to Interference Ratio, C/I Ratio); And pollute the signal that desire receives, so that influence the reception of superheterodyne receiver.In the face of the problem that image frequency is disturbed, the most frequently used method is before frequency mixer 106, to add a band pass filter, and promptly the image cancellation filter 104, and is in order to get into the interference signal filtering again in the frequency mixer 106 earlier, minimum so that interference is reduced to.
In order to weigh the usefulness of frequency demultiplier 10, have a critical specifications be the image frequency rejection than (ImageFrequency Rejection Ratio), be defined as the gain inequality of receive frequency and image frequency, for example, in satellite frequency demultiplier, general requirements is 40dB.And image cancellation filter 104 then is the most important parameters of the image frequency rejection ratio of decision frequency demultiplier 10 in insertion loss (Insertion Loss) gap of receive frequency and image frequency.
In the prior art, the implementation of image cancellation filter 104 has many kinds, for example hairpin-line bandpass filter (Hairpin Band Pass Filter) or parallel coupled line filter (parallel-coupledlinefilter) etc.Please refer to Fig. 2, Fig. 2 is the sketch map of an existing hairpin-line bandpass filter 20.Hairpin-line bandpass filter 20 is to be lateral symmetry formula (transverse symmetry) framework, and it includes microstrip line (Micro-strip Line) connector IO_a, IO_b and resonator RSN_1～RSN_n.Microstrip line end IO_a, IO_b are connected in forward and backward level circuit, in order to receive and the output signal.The length overall of each resonator of resonator RSN_1～RSN_n is approximately the half the of signal wavelength that desire receives, and the number n of resonator RSN_1～RSN_n is represented the exponent number (Order) of hairpin-line bandpass filter 20, and the designer can be according to the size of different Demand Design n.The frequency response sketch map of hairpin-line bandpass filter 20 when for example, Fig. 3 is n=5.In Fig. 3; Curve a1, b1, c1 correspond respectively to scattering parameter S11, S21, S22, and related definition is that industry is known, and does not give unnecessary details at this; Like " Microelectronic Circuits " 2004 the 5th edition, the author is Adel S.Sedra and Kenneth C.Smith; " Feedback Control of Dynamic Systems " third edition in 1994, the author is Gene F.Franklin, J.David Powell and Abbas Emami-Naeini; " Nonlinear Microwave Circuit " 1998, the author is Stephen A.Maas.Can know that by Fig. 3 the insertion loss that desire receives low-limit frequency 18.3GHz is 5dB, and the minimum insertion loss of image frequency frequency range 17.3 ~ 17.8GHz is 40.3dB, so image frequency rejection ratio is merely 40.3-5=35.3dB.
Generally speaking, the exponent number of hairpin-line bandpass filter 20 is high more, and promptly n is big more, and then to image frequency rejection effect better, but its shared board area is also bigger, cost also with increase; Otherwise the exponent number that limits hairpin-line bandpass filter 20 if will reduce apparent size is big or small, then possibly have not foot phenomenon of image frequency rejection, influences signal receiving quality.
[summary of the invention]
Therefore, main purpose of the present invention promptly is to provide a kind of band pass filter and related frequency demultiplier thereof.
The present invention discloses a kind of band pass filter, includes one first microstrip line end, is used for receiving a radiofrequency signal; One second microstrip line end is used for exporting a rf filtering signal, is formed with at least one resonant cavity in this second microstrip line end, is used for promoting the rejection effect corresponding to the image frequency of this rf filtering signal; And a plurality of resonators, be arranged between this first microstrip line end and this second microstrip line end, be used for this radiofrequency signal is carried out bandpass filtering treatment, to produce this rf filtering signal.
The present invention discloses a kind of frequency demultiplier that promotes the rejection effect of image frequency in addition, includes a receiving terminal, is used for receiving a radiofrequency signal; One frequency mixer is used for according to a local oscillated signal frequency of one rf filtering signal being reduced to a predeterminated frequency, to export an intermediate-freuqncy signal; One band pass filter is coupled between this receiving terminal and this frequency mixer, and it includes one first microstrip line end, is coupled to this receiving terminal, is used for receiving this radiofrequency signal; One second microstrip line end is coupled to this frequency mixer, is used for exporting this rf filtering signal, is formed with at least one resonant cavity in this second microstrip line end, is used for promoting the rejection effect corresponding to the image frequency of this rf filtering signal; And a plurality of resonators, be arranged between this first microstrip line end and this second microstrip line end, be used for this radiofrequency signal is carried out bandpass filtering treatment, to produce this rf filtering signal.
[description of drawings]
Fig. 1 is the existing sketch map that is used for a frequency demultiplier of a superheterodyne receiver.
Fig. 2 is the sketch map of an existing hairpin-line bandpass filter.
Frequency response sketch map when the hairpin-line bandpass filter of Fig. 3 Fig. 2 is five rank.
Fig. 4 is the sketch map of the embodiment of the invention one hairpin-line bandpass filter.
The hairpin-line bandpass filter of Fig. 5 Fig. 4 is five rank and the frequency response sketch map when comprising two resonant cavities.
[embodiment]
Please refer to Fig. 4, Fig. 4 is the sketch map of the embodiment of the invention one hairpin-line bandpass filter 40.Hairpin-line bandpass filter 40 preferably is to be applicable in the frequency demultiplier shown in Figure 1 10, and in order to realizing image cancellation filter 104, it includes one first microstrip line end 400, one second microstrip line end 402 and resonator IRSN_1～IRSN_n.The first microstrip line end 400 and the second microstrip line end 402 be in order to connect forward and backward level circuit, i.e. low noise amplifier among Fig. 1 102 (through receiving terminal 103) and frequency mixer 106 are with received RF signal V
RF2And frequency wave signal VF is penetrated in generation
RFResonator IRSN_1～IRSN_n then is arranged between the first microstrip line end 400 and the second microstrip line end 402, and each resonator is that U type and total length approximate rf filtering signal VF
RFWavelength 1/2nd.In addition, in the second microstrip line end 402, be formed with resonant cavity RSLT_1～RSLT_m, in order to promote corresponding to penetrating frequency wave signal VF
RFThe rejection effect of image frequency.
Comparison diagram 4 can know that with Fig. 2 the framework of hairpin-line bandpass filter 40 is similar with the framework of hairpin-line bandpass filter 20, different be in, be formed with resonant cavity RSLT_1～RSLT_m in the second microstrip line end 402.In simple terms, the present invention lies in the second microstrip line end 402 and to form resonant cavity RSLT_1～RSLT_m, and to wavelength be the signal generation rejection effect of each resonant cavity length overall twice, that is the length overall of each resonant cavity is about and penetrates frequency wave signal VF
RFWavelength 1/2nd.The number that thus, need not increase resonator IRSN_1～IRSN_n can promote image frequency rejection effect.
In Fig. 4, resonant cavity RSLT_1～RSLT_m is all the U type, and the total length of each resonant cavity approximates and penetrates frequency wave signal VF
RFWavelength 1/2nd, with correlation frequency wave signal VF
RFNear the formation rejection effect of frequency.Certainly, on circuit design, this area tool is known the knowledgeable suitably length, groove interval, groove width, number, interval etc. of selective reaonance chamber RSLT_1～RSLT_m usually, is adjusted at image frequency rejection effect, to reach specification requirement.
For instance, when Fig. 5 is n=5, m=2, the frequency response sketch map of hairpin-line bandpass filter 40.In Fig. 5, curve a2, b2, c2 correspond respectively to scattering parameter S11, S21, S22, and related definition is that industry is known, and does not give unnecessary details at this.Can know by Fig. 5; The insertion loss that desire receives low-limit frequency 18.3GHz is 5.9dB; And the minimum insertion loss of image frequency frequency range 17.3 ~ 17.8GHz is 52.4dB, so the image frequency rejection has improved 11dB than for 42.4-5.9=46.5dB than prior art (with reference to figure 3); Thereby can reach specification requirement not increasing under the circuit area.
What pay special attention to is that the sketch map that is merely hairpin-line bandpass filter 40 shown in Figure 4, this area tool know that usually the knowledgeable is not limited thereto when doing different modifications according to this.For example, except forming resonant cavity RSLT_1～RSLT_m, also can form resonant cavity at the first microstrip line end 400 at the second microstrip line end 402.In addition, the mode that forms resonant cavity RSLT_1～RSLT_m also is not limited to particular process, for example, can see through etching mode and be formed in the second microstrip line end 402.Except that this, with the image cancellation filter 104 that hairpin-line bandpass filter 40 replaces among Fig. 1, can promote the image frequency rejection effect of frequency demultiplier 10, relevant mode of connection should be this area tool and knows that usually the knowledgeable can accomplish with reference to above stated specification, does not give unnecessary details at this.Again; Though the present invention is at this image cancellation filter 104 that replaces among Fig. 1 with hairpin-line bandpass filter 40; Yet do not represent the present invention only to be confined to the application of hairpin-line bandpass filter, know this technological art, when learning that the present invention can also be applicable to other band pass filter; For example parallel coupled line filter promptly is, its mode of ameliorating is with hairpin-line bandpass filter shown in Figure 4 40.
In sum, the present invention lies in and forms the chamber that shakes at least altogether in the microstrip line, in order to the insertion loss of lifting image frequency frequency range, thus the rejection effect of increase image frequency.In other words, the number that the present invention need not increase resonator can promote image frequency rejection effect, but except the holding circuit area, also can effectively promote signal receiving quality.
The above is merely preferred embodiment of the present invention, and all equalizations of doing according to claim of the present invention change and modify, and all should belong to covering scope of the present invention.
Claims (17)
1. band pass filter includes:
One first microstrip line end is used for receiving a radiofrequency signal;
One second microstrip line end is used for exporting a rf filtering signal, is formed with at least one resonant cavity in this second microstrip line end, is used for promoting the rejection effect corresponding to the image frequency of this rf filtering signal; And
A plurality of resonators are arranged between this first microstrip line end and this second microstrip line end, are used for this radiofrequency signal is carried out bandpass filtering treatment, to produce this rf filtering signal.
2. band pass filter according to claim 1 is characterized in that, each resonant cavity of this at least one resonant cavity is the U type.
3. band pass filter according to claim 1 is characterized in that, the total length of each resonant cavity of this at least one resonant cavity equal this rf filtering signal wavelength 1/2nd.
4. band pass filter according to claim 1 is characterized in that, this at least one resonant cavity is to be formed in this second microstrip line end with etching mode.
5. band pass filter according to claim 1 is characterized in that, each resonator of these a plurality of resonators is the U type.
6. band pass filter according to claim 1 is characterized in that, the total length of each resonator of these a plurality of resonators equal this rf filtering signal wavelength 1/2nd.
7. band pass filter according to claim 1 is characterized in that, this band pass filter is a hairpin-line bandpass filter.
8. band pass filter according to claim 1 is characterized in that, this band pass filter is a parallel coupled line filter.
9. frequency demultiplier that can promote the rejection effect of image frequency includes:
One receiving terminal is used for receiving a radiofrequency signal;
One frequency mixer is used for according to a local oscillated signal frequency of one rf filtering signal being reduced to a predeterminated frequency, to export an intermediate-freuqncy signal;
One band pass filter is coupled between this receiving terminal and this frequency mixer, and it includes:
One first microstrip line end is coupled to this receiving terminal, is used for receiving this radiofrequency signal;
One second microstrip line end is coupled to this frequency mixer, is used for exporting this rf filtering signal, is formed with at least one resonant cavity in this second microstrip line end, is used for promoting the rejection effect corresponding to the image frequency of this rf filtering signal; And
A plurality of resonators are arranged between this first microstrip line end and this second microstrip line end, are used for this radiofrequency signal is carried out bandpass filtering treatment, to produce this rf filtering signal.
10. frequency demultiplier according to claim 9 is characterized in that, each resonant cavity of this at least one resonant cavity is the U type.
11. frequency demultiplier according to claim 9 is characterized in that, the total length of each resonant cavity of this at least one resonant cavity equal this rf filtering signal wavelength 1/2nd.
12. frequency demultiplier according to claim 9 is characterized in that, this at least one resonant cavity is formed in this second microstrip line end with etching mode.
13. frequency demultiplier according to claim 9 is characterized in that, each resonator of these a plurality of resonators is the U type.
14. frequency demultiplier according to claim 9 is characterized in that, the total length of each resonator of these a plurality of resonators equal this rf filtering signal wavelength 1/2nd.
15. frequency demultiplier according to claim 9, it is used for a superheterodyne receiver.
16. frequency demultiplier according to claim 9 is characterized in that, this band pass filter is a hairpin-line bandpass filter.
17. frequency demultiplier according to claim 9 is characterized in that, this band pass filter is a parallel coupled line filter.
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| CN101656342B true CN101656342B (en) | 2012-09-05 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US9042847B2 (en) | 2012-11-08 | 2015-05-26 | Hauwei Technologies Co., Ltd. | Filter, receiver, transmitter and transceiver |
| CN103811832B (en) * | 2012-11-08 | 2016-03-09 | 华为技术有限公司 | Filter, receiver, transmitter and transceiver |
| CN104378126A (en) * | 2013-08-16 | 2015-02-25 | 国基电子（上海）有限公司 | Wireless radio frequency receiving circuit |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1549387A (en) * | 2003-05-21 | 2004-11-24 | 海泰超导通讯科技（天津）有限公司 | Contact type anti-parallel hair-pin comb type wave filter for microwave communication |
| CN2881985Y (en) * | 2006-01-20 | 2007-03-21 | 百一电子股份有限公司 | LNB high frequency filter |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1549387A (en) * | 2003-05-21 | 2004-11-24 | 海泰超导通讯科技（天津）有限公司 | Contact type anti-parallel hair-pin comb type wave filter for microwave communication |
| CN2881985Y (en) * | 2006-01-20 | 2007-03-21 | 百一电子股份有限公司 | LNB high frequency filter |
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