In high-frequency PCB ọkọ, a diẹ pataki iru ti kikọlu ni agbara ipese ariwo. Nipa ṣiṣe itupalẹ awọn abuda ati awọn idi ti ariwo agbara lori awọn igbimọ PCB igbohunsafẹfẹ giga-giga, onkọwe gbe siwaju diẹ ninu awọn solusan ti o munadoko pupọ ati irọrun ni apapọ pẹlu awọn ohun elo imọ-ẹrọ.

Analysis of power supply noise

Ariwo ipese agbara n tọka si ariwo ti ipilẹṣẹ nipasẹ ipese agbara funrararẹ tabi ti o fa idamu. Idaamu naa han ni awọn aaye wọnyi:

1) Distributed noise caused by the inherent impedance of the power supply itself. In high-frequency circuits, power supply noise has a greater impact on high-frequency signals. Therefore, a low-noise power supply is first required. A clean ground is as important as a clean power source. The power characteristic is shown as in Fig. 1.

Agbara igbi fọọmu

Gẹgẹbi a ti le rii lati Nọmba 1, ipese agbara labẹ awọn ipo to dara ko ni idiwọ, nitorina ko si ariwo. Bibẹẹkọ, ipese agbara gangan ni ikọlu kan, ati pe a pin kaakiri lori gbogbo ipese agbara, nitorinaa, ariwo yoo tun gbe lori ipese agbara. Nitorina, idiwọ ti ipese agbara yẹ ki o dinku bi o ti ṣee ṣe, ati pe o dara julọ lati ni ipilẹ agbara ti o ni igbẹhin ati ipilẹ ilẹ. Ni apẹrẹ iyika igbohunsafẹfẹ giga-giga, o dara julọ lati ṣe apẹrẹ ipese agbara ni irisi Layer ju ni irisi ọkọ akero, ki lupu le tẹle ọna nigbagbogbo pẹlu ikọlu ti o kere ju. Ni afikun, igbimọ agbara gbọdọ tun pese ifihan ifihan agbara fun gbogbo awọn ifihan agbara ti ipilẹṣẹ ati ti o gba lori PCB, ki aami ifihan le dinku, nitorinaa dinku ariwo.

2) Common mode field interference. Refers to the noise between the power supply and the ground. It is the interference caused by the common mode voltage caused by the loop formed by the interfered circuit and the common reference surface of a certain power supply. Its value depends on the relative electric field and magnetic field. The strength depends on the strength. As shown in Figure 2.

Common mode interference

On this channel, a drop in Ic will cause a common-mode voltage in the series current loop, which will affect the receiving part. If the magnetic field is dominant, the value of the common mode voltage generated in the series ground loop is:

Wọpọ mode foliteji

Ninu agbekalẹ (1), ΔB jẹ iyipada ninu iwuwo ṣiṣan oofa, Wb/m2; S ni agbegbe, m2.

If it is an electromagnetic field, when its electric field value is known, its induced voltage is

Inductive foliteji

Idogba (2) ni gbogbo igba kan L=150/F tabi kere si, nibiti F jẹ igbohunsafẹfẹ ti awọn igbi itanna ni MHz.

The author’s experience is: If this limit is exceeded, the calculation of the maximum induced voltage can be simplified to:

O pọju induced foliteji

3) Differential mode field interference. Refers to the interference between the power supply and the input and output power lines. In the actual PCB design, the author found that its proportion in the power supply noise is very small, so it is not necessary to discuss it here.

4) Inter-ila kikọlu. Ntọkasi kikọlu laarin awọn laini agbara. Nigbati agbara ibaramu C ati inductance ibaramu M1-2 wa laarin awọn iyika afiwera meji ti o yatọ, ti o ba wa foliteji VC ati lọwọlọwọ IC ni iyika orisun kikọlu, Circuit kikọlu yoo han:

A. The voltage coupled through capacitive impedance is

Foliteji pelu nipasẹ capacitive impedance

Ni agbekalẹ (4), RV jẹ iye ti o jọra ti resistance opin-isunmọ ati resistance opin-opin ti iyika idasi.

B. Series resistance through inductive coupling

Jara resistance nipasẹ inductive sisopọ

Ti ariwo ipo ti o wọpọ ba wa ni orisun kikọlu, kikọlu laini-si-ila ni gbogbogbo gba irisi ipo ti o wọpọ ati ipo iyatọ.

5) Isopọ ila agbara. O tọka si lasan pe lẹhin okun agbara AC tabi DC ti wa labẹ kikọlu itanna, okun agbara ntan kikọlu naa si awọn ẹrọ miiran. Eyi ni kikọlu aiṣe-taara ti ariwo ipese agbara si Circuit igbohunsafẹfẹ-giga. O yẹ ki o ṣe akiyesi pe ariwo ti ipese agbara ko jẹ ipilẹṣẹ nipasẹ ararẹ, ṣugbọn o tun le jẹ ariwo ti o fa nipasẹ kikọlu ita, ati lẹhinna fi ariwo yii pọ si pẹlu ariwo ti o ṣẹda funrararẹ (radiation tabi idari) lati dabaru pẹlu awọn iyika miiran. tabi awọn ẹrọ.

Awọn ọna wiwọn lati yọkuro kikọlu ariwo ipese agbara

Ni wiwo awọn ifarahan oriṣiriṣi ati awọn idi ti kikọlu ariwo ipese agbara ti a ṣe atupale loke, awọn ipo labẹ eyiti o waye le parun ni ọna ti a fojusi, ati kikọlu ti ariwo ipese agbara le ni imunadoko. Awọn ojutu ni o wa bi wọnyi: 1) San ifojusi si awọn nipasẹ ihò lori awọn ọkọ. Awọn nipasẹ iho nbeere ohun šiši lori awọn agbara Layer lati wa ni etched lati fi aaye fun awọn nipasẹ iho lati kọja nipasẹ. Ti šiši ti Layer agbara ba tobi ju, yoo ni ipa lori lupu ifihan agbara, ifihan agbara yoo fi agbara mu lati fori, agbegbe lupu yoo pọ sii, ati ariwo yoo pọ si. Ni akoko kanna, ti diẹ ninu awọn laini ifihan ba wa ni idojukọ nitosi ṣiṣi ati pin lupu yii, ikọlu ti o wọpọ yoo fa crosstalk. Wo aworan 3.

Fori awọn wọpọ ona ti awọn ifihan agbara Circuit

2) Awọn okun waya ilẹ ti o to ni a nilo fun awọn okun asopọ. Ifihan agbara kọọkan nilo lati ni lupu ami iyasọtọ ti ara rẹ, ati agbegbe lupu ti ifihan ati lupu jẹ kekere bi o ti ṣee, iyẹn ni pe, ifihan ati lupu gbọdọ jẹ afiwe.

3) Gbe a àlẹmọ ariwo ipese agbara. O le ṣe imunadoko ariwo ni inu ipese agbara ati mu imudara kikọlu ati aabo ti eto naa. Ati pe o jẹ àlẹmọ igbohunsafẹfẹ redio ọna meji, eyiti ko le ṣe àlẹmọ kikọlu ariwo nikan ti a ṣe lati laini agbara (lati ṣe idiwọ kikọlu lati awọn ohun elo miiran), ṣugbọn tun ṣe àlẹmọ ariwo ti ipilẹṣẹ funrararẹ (lati yago fun kikọlu pẹlu awọn ohun elo miiran). ), ati dabaru pẹlu ipo ni tẹlentẹle ipo ti o wọpọ. Mejeji ni ipa inhibitory.

4) Power isolation transformer. Separate the power loop or the common mode ground loop of the signal cable, it can effectively isolate the common mode loop current generated in the high frequency.

5) Olutọsọna ipese agbara. Gbigba ipese agbara mimọ le dinku ipele ariwo ti ipese agbara pupọ.

6) Asopọmọra. Awọn titẹ sii ati awọn laini iṣelọpọ ti ipese agbara ko yẹ ki o gbe si eti igbimọ dielectric, bibẹẹkọ o rọrun lati ṣe ina itankalẹ ati dabaru pẹlu awọn iyika tabi ẹrọ miiran.

7) Afọwọṣe ati ipese agbara oni-nọmba yẹ ki o yapa. Awọn ẹrọ igbohunsafẹfẹ giga ni gbogbogbo jẹ ifarabalẹ pupọ si ariwo oni-nọmba, nitorinaa awọn mejeeji yẹ ki o pinya ati sopọ papọ ni ẹnu-ọna ipese agbara. Ti ifihan naa ba nilo lati tan mejeeji afọwọṣe ati awọn ẹya oni-nọmba, a le gbe lupu si akoko ifihan lati dinku agbegbe lupu naa. Bi o ṣe han ni aworan 4.

Place a loop at the signal crossing to reduce the loop area

8) Yago fun agbekọja ti awọn ipese agbara lọtọ laarin awọn ipele oriṣiriṣi. Mu wọn pọ si bi o ti ṣee ṣe, bibẹẹkọ ariwo ipese agbara jẹ irọrun pọ nipasẹ agbara parasitic.

9) Isolate sensitive components. Some components, such as phase-locked loops (PLL), are very sensitive to power supply noise. Keep them as far away from the power supply as possible.

10) Gbe okun agbara. Lati le dinku lupu ifihan agbara, ariwo le dinku nipa gbigbe laini agbara si eti laini ifihan, bi o ṣe han ni Nọmba 5.

Gbe okun agbara lẹgbẹẹ laini ifihan

11) Lati yago fun ariwo ipese agbara lati dabaru pẹlu igbimọ Circuit ati ariwo ikojọpọ ti o ṣẹlẹ nipasẹ kikọlu ita si ipese agbara, a le sopọ capacitor fori si ilẹ ni ọna kikọlu (ayafi fun itankalẹ), nitorinaa. ariwo le ti wa ni fori si ilẹ lati yago fun Idalọwọduro pẹlu awọn ẹrọ miiran ati awọn ẹrọ.

Ariwo ipese agbara ti wa ni taara tabi fi ogbon ekoro ti ipilẹṣẹ lati ipese agbara ati ki o dabaru pẹlu awọn Circuit. Nigbati o ba dinku ipa rẹ lori Circuit, ilana gbogbogbo yẹ ki o tẹle. Ni apa kan, ariwo ipese agbara yẹ ki o ni idaabobo bi o ti ṣee ṣe. Ipa ti Circuit, ni apa keji, yẹ ki o tun dinku ipa ti ita tabi iyika lori ipese agbara, ki o má ba buru ariwo ti ipese agbara.