Zviitiko zvakawanda zvekushandisa kwemaindasitiri, sainzi, uye zvekurapa radio frequency (ISM-RF) zvigadzirwa zvinoratidza kuti iyo yakadhindwa redunhu bhodhi marongero ezvigadzirwa izvi anotarisana nehurema hwakasiyana.Vanhu vanowanzoona kuti iyo imwechete IC yakaiswa pane maviri akasiyana wedunhu mabhodhi, zviitwa zvekuita zvichave zvakasiyana zvakanyanya. Variations in operating conditions, harmonic radiation, anti-interference ability, and start-up time can explain the importance of circuit board layout in a successful design.

This article lists the various design omissions, discusses the causes of each failure, and provides suggestions on how to avoid these design defects. Mune bepa iri, fr-4 dielectric, 0.0625in ukobvu yakapetwa kaviri pcb semuenzaniso, redunhu bhodhi richisimbisa. Operating in different frequency bands between 315MHz and 915MHz, Tx and Rx power between -120dbm and +13dBm.

Inductance nhungamiro

Kana vaviri inductors (kana kunyange maviri pcb mitsara) ari padhuze nepadhuze, inowirirana inductance ichaitika. The magnetic field generated by the current in the first circuit excites the current in the second circuit (Figure 1). This process is similar to the interaction between the primary and secondary coils of a transformer. When two currents interact through a magnetic field, the voltage generated is determined by mutual inductance LM:

Iko, YB ndiyo yekukanganisa magetsi yakaiswa mudunhu B, IA ndiyo yazvino 1 inoshanda padunhu A. LM inonyanya kutarisisa kutsemuka kwedunhu, inductance loop nharaunda (kureva., Magnetic flux), uye nzira yekutenderera. Therefore, the best balance between compact circuit layout and reduced coupling is the correct alignment of all inductors in the direction.

FIG. 1. It can be seen from magnetic field lines that mutual inductance is related to inductance alignment direction

The direction of circuit B is adjusted so that its current loop is parallel to the magnetic field line of circuit A. Nechinangwa ichi, sekungotaridzika sezvinobvira kune mumwe nemumwe, ndapota tarisa kune iyo dunhu dhizaini yepasi simba FSK superheterodyne Receiver Evaluation (EV) bhodhi (MAX7042EVKIT) (Mufananidzo 2). The three inductors on the board (L3, L1 and L2) are very close to each other, and their orientation at 0°, 45° and 90° helps to reduce mutual inductance.

Mufananidzo 2. Marongero maviri akasiyana ePBB anoratidzwa, imwe yacho ine zvinhu zvakarongedzwa nenzira isiri iyo (L1 neL3), nepo imwe yacho iri yakakodzera.

Kupfupisa, nheyo dzinotevera dzinofanira kuteedzerwa:

Iyo inductance spacing inofanira kunge iri kure sezvinobvira.

Inductors akarongedzwa pamakona akakodzera kudzikisa crosstalk pakati pevanodzora.

Tungamira kubatanidza

Kungofanana nekutarisisa kwema inductors kunokanganisa kubatanidza kwemagineti, saizvozvo kubatana kana iwo mutungamiriri uri padhuze nepadhuze. Rudzi urwu rwematambudziko ehurongwa zvakare runogadzira izvo zvinonzi mutual sensation. Rimwe rematambudziko anonyanya kunetsekana eRF wedunhu ndeye wiring yezvikamu zvine mutsindo zveiyo system, senge yekuisa inowirirana network, resonant chiteshi cheanogamuchira, kanyanga inowirirana network yemutepfenyuri, nezvimwe.

Iyo yekudzoka yazvino nzira inofanira kunge iri padhuze neyakanyanya nzira yazvino sezvinobvira kudzikisira iyo radiation magnetic field. This arrangement helps to reduce the current loop area. Iyo yakanaka yakaderera nzira yekudzivirira yazvino kudzoka kazhinji inzvimbo yepasi pazasi pehutobvu – zvinobudirira kudzora chiuno nzvimbo kunharaunda uko ukobvu hwe dielectric inowedzerwa nehurefu hwehutobvu. Nekudaro, kana iyo nzvimbo yepasi yakakamurwa, iyo nzvimbo yekutenderera inowedzera (Mufananidzo 3). For leads passing through the split region, the return current will be forced through the high resistance path, greatly increasing the current loop area. This arrangement also makes circuit leads more susceptible to mutual inductance.

Mufananidzo 3. Zadza nzvimbo yakakura pasi inobatsira kuvandudza mashandiro ehurongwa

Kune chaiyo inductor, lead lead zvakare ine yakakosha mhedzisiro pane magnetic munda kubatanidza. Kana iyo inotungamira yedunhu rinotenderera ichifanira kunge iri padhuze nepadhuze, zviri nani kurongedza zvinongedzo zvichitwasuka kudzikisa kubatanidza (Mufananidzo 4). If vertical alignment is not possible, consider using a guard line. Zvekudzivirira waya dhizaini, ndapota tarisa kune yekumisikidza uye nekuzadza chikamu chekurapa pazasi.

Figure 4. Similar to Figure 1, shows the possible coupling of magnetic field lines.

To sum up, the following principles should be followed when the plate is distributed:

Complete grounding should be ensured below the lead.

Inotungamira inotungamira inofanirwa kurongwa yakatwasuka.

If the leads must be arranged in parallel, ensure adequate spacing or use guard wires.

Grounding via

Dambudziko rakakura neRF redunhu dhizaini inowanzo kuve suboptimal hunhu impedance yedunhu, kusanganisira edunhu zvikamu uye nekubatana kwavo. Iyo inotungamira ine yakapfava yemhangura yekumhara yakaenzana neiyo inductance waya uye inogadzira yakaparadzirwa capacitance nemamwe anotungamira ari padyo. Iyo lead inotaridzawo inductance uye capacitance zvivakwa sezvo ichipfuura nepaburi.

The through-hole capacitance mainly comes from the capacitance formed between the copper cladding on the side of the through-hole pad and the copper cladding on the ground, separated by a fairly small ring. Another influence comes from the cylinder of the metal perforation itself. Mhedzisiro yehutachiona capacitance inowanzo kuve diki uye kazhinji inongokonzeresa kumucheto kusiyanisa mumadhigiramu emadhijitari anomhanya (izvo zvisina kukurukurwa mupepa rino).

Iyo hombe mhedzisiro yeiyo kuburikidza-gomba ndeye chisvetasimba inductance inokonzerwa neiyo inoenderana yekubatana modhi. Because most metal perforations in RF PCB designs are the same size as lumped components, the effect of electrical perforations can be estimated using a simple formula (FIG. 5) :

Where, LVIA is lumped inductance through hole; H is the height of the throughhole, in inches; D ndiyo dhayamita yeiyo inopora, in inches 2.

Maitiro ekudzivirira kukanganisa kwakasiyana-siyana muPCB marongero emabhodhi akadhindwa

FIG. 5. PCB cross section used to estimate parasitic effects on through-hole structures

The parasitic inductance often has a great influence on the connection of bypass capacitors. Yakanaka yekupfuura ma capacitors inopa yakakwira-frequency mapfupi maseketi pakati penzvimbo yekugovera uye kuumbwa, asi isiri-yakanaka kuburikidza-maburi inogona kukanganisa yakaderera-kunzwisisika nzira pakati pekuumbwa nenzvimbo yekugovera. A typical PCB through hole (d = 10 mil, h = 62.5 mil) is approximately equivalent to a 1.34nH inductor. Tichifunga nezve yakatarwa yekushandisa frequency yeiyo ISM-RF chigadzirwa, iyo kuburikidza-maburi inogona kukanganisa zvakashata maseketi akadai se resonant chiteshi maseketi, mafirita, uye anoenderana network.

Mamwe matambudziko anomuka kana maseketi anononoka achigovana maburi, senge maoko maviri e π – mhando network. Semuenzaniso, nekuisa gomba rakaringana rakaenzana neiyo lumped inductance, iyo yakaenzana schematic yakatosiyana neyekutanga wedunhu dhizaini (FIG. 6). As with crosstalk of common current path 3, resulting in increased mutual inductance, increased crosstalk and feed-through.

How to avoid PCB design problems

Mufananidzo 6. Yakanakisa vs. isina-akakodzera mapurani, pane angangoita “emasaini nzira” mudunhu.

To sum up, circuit layout should follow the following principles:

Ensure modeling of through-hole inductance in sensitive areas.

The filter or matching network uses independent through-holes.

Note that a thinner PCB copper-clad will reduce the effect of parasitic inductance through the hole.

Kureba kwekutungamira

Maxim ISM-RF chigadzirwa data kazhinji inokurudzira kushandisa ipfupi inokwanisika yepamusoro-frequency yekuisa uye kuburitsa kunotungamira kudzikisa kurasikirwa uye radiation. Kune rimwe divi, kurasikirwa kwakadai kunowanzo kukonzerwa neasina kukwana maparasiti parameter, saka zvese zvipembenene inductance uye capacitance zvinokanganisa maseketi marongero, uye kushandisa ipfupi zvinogoneka kutungamira kunobatsira kudzora maparasita parameter. Typically, a 10 mil wide PCB lead with a distance of 0.0625in… From a FR4 board produces an inductance of approximately 19nH/in and a distributed capacitance of approximately 1pF/in. Kune LAN / musanganisi wedunhu ine 20nH inductor uye 3pF capacitor, iyo inoshanda chikamu kukosha inozokanganiswa zvakanyanya kana dunhu uye chikamu chechimiro chakanyanya kuumbana.

Ipc-d-317a4 in ‘Institute for Printed Circuits’ provides an industry standard equation for estimating various impedance parameters of microstrip PCB. Gwaro iri rakatsiviwa muna2003 neIPC-2251 5, iyo inopa nzira chaiyo yekuverengera nzira dzakasiyana dzePBB inotungamira. Online calculators are available from a variety of sources, most of which are based on equations provided by IPC-2251. The Electromagnetic Compatibility Lab at Missouri Institute of Technology provides a very practical method for calculating PCB lead impedance 6.

The accepted criteria for calculating the impedance of microstrip lines are:

Mune fomula, εr ndiyo dielectric inogara iri dielectric, h ndiko kukwirira kwemutobvu kubva kune stratum, W ndiko kutungamira upamhi, uye T ndiko kukora kwekutungamira (FIG. 7). Kana w / h iri pakati pe0.1 ne2.0 uye εr iri pakati pe1 ne15, mhedzisiro yekuverenga yefomula iyi yakanyatsoita.

Figure 7. This figure is a PCB cross section (similar to Figure 5) and represents the structure used to calculate the impedance of a microstrip line.

In order to evaluate the effect of lead length, it is more practical to determine the detuning effect of ideal circuit by lead parasitical parameters. Mumuenzaniso uyu, tinokurukura dzakarasika capacitance uye inductance. The standard equation of characteristic capacitance for microstrip lines is:

Saizvozvo, hunhu inductance inogona kuverengerwa kubva kuiyo equation nekushandisa iri pamusoro equation:

Semuenzaniso, fungidzira pcb ukobvu hwe0.0625in. (h = 62.5 mil), 1 ounce lead-yakavharwa lead (t = 1.35 mil), 0.01in. (w = 10 mil), uye bhodhi FR-4. Ziva kuti iyo i Eigenvalues ​​akaverengwa mumuenzaniso uyu Z0 = 134 ω, C0 = 1.04pF / in, L0 = 18.7nH / in.

Kune AN ISM-RF dhizaini, iyo 12.7mm (0.5in) dhizaini yekureba kwemitobvu pabhodhi inogona kuburitsa parasitic parameter angangoita 0.5pF uye 9.3nH (Mufananidzo 8). Mhedzisiro yeparasitic parameter padanho iri pane resonant chiteshi cheanogamuchira (kusiana kweLC chigadzirwa) zvinogona kukonzera 315MHz ± 2% kana 433.92mhz ± 3.5% mutsauko. Nekuda kweiyo yekuwedzera capacitance uye inductance inokonzerwa nehutachiona hwehutungamiriri, iyo yepamusoro yeiyo 315MHz oscillation frequency inosvika 312.17mhz, uye iyo yepamusoro ye433.92mhz oscillation frequency inosvika 426.6mhz.

Another example is the resonant channel of Maxim’s superheterodyne receiver (MAX7042). The recommended components are 1.2pF and 30nH at 315MHz; At 433.92MHz, it is 0pF and 16nH. Verengai masekisheni emakesi esonantiki uchishandisa iyo equation:

Kuongororwa kwedenderedzwa reseti yeplate kunofanirwa kusanganisira mhedzisiro yemupaketi uye dhizaini, uye iwo maparasita parameter ari 7.3PF uye 7.5PF zvakateerana kana uchiverenga 315MHz resonant frequency. Ziva kuti iyo LC chigadzirwa inomiririra lumped capacitance.

Kupfupisa, nheyo dzinotevera dzinofanira kuteverwa:

Chengetedza hutungamiri hupfupi sezvinobvira.

Isa maseketi akakosha padhuze nechigadzirwa sezvinobvira.

Makiyi makuru anopihwa muripo zvichienderana neicho chimiro maratidziro.

Kuchengetedza uye kuzadza kurapwa

The grounding or power layer defines a common reference voltage that supplies power to all parts of the system through a low resistance path. Kuenzanisa minda yese yemagetsi nenzira iyi inogadzira yakanaka yekudzivirira michina.

Direct yazvino inowanzo tenderera kuyerera munzira yakaderera yekudzivirira. Nenzira imwecheteyo, yakakwira-frequency yazvino inosarudzika inoyerera kuburikidza nenzira ine yakaderera kuramba. So, for a standard PCB microstrip line above the formation, the return current tries to flow into the ground region directly below the lead. As described in the lead coupling section above, the cut ground area introduces various noises that increase crosstalk either through magnetic field coupling or by converging currents (Figure 9).

Maitiro ekudzivirira kukanganisa kwakasiyana-siyana muPCB marongero emabhodhi akadhindwa

FIG. 9. Keep the formation intact as much as possible, otherwise the return current will cause crosstalk.

Filled ground, also known as guard lines, is commonly used in circuits where continuous grounding is difficult to lay or where shielding sensitive circuits is required (FIG. 10). The shielding effect can be increased by placing grounding holes (i.e. hole arrays) at both ends of the lead or along the lead. 8. Usasanganise waya yekurinda nemutobvu wakagadzirirwa kuti upe nzira yazvino yekudzoka. Iyi gadziriro inogona kuunza crosstalk.

Maitiro ekudzivirira kukanganisa kwakasiyana-siyana muPCB marongero emabhodhi akadhindwa

NGUVA. 10. Iyo RF system dhizaini inofanirwa kudzivirira kuyangarara waya dzakapfeka waya, kunyanya kana sheathing yemhangura ichidikanwa.

Nzvimbo yemhangura-yakavharirwa haina kuvhurwa (kuyangarara) kana kuvakwa pasi pamucheto mumwe chete, izvo zvinotadzisa kushanda kwayo. In some cases, it can cause unwanted effects by forming parasitic capacitance that changes the impedance of the surrounding wiring or creates a “latent” path between circuits. Muchidimbu, kana chidimbu chendarira chakaputirwa (isiri-yedunhu chiratidzo wiring) chakaiswa padunhu redunhu kuti uone kuenderana kwekuputira kwakakora. Nzvimbo dzemhangura-dzakapfeka dzinofanirwa kudzivirirwa sezvo dzichikanganisa dhizaini dhizaini.

Chekupedzisira, ita shuwa yekutarisa mhedzisiro yechero nzvimbo yepasi padyo neiyo antenna. Chero ipi monopole antenna ichave nenzvimbo yepasi, wiring nemaburi sechikamu cheiyo system equilibrium, uye isiri-yakanaka equilibrium wiring inochinja kugona kwemwaranzi uye kutungamira kweiyo antenna (radiation template). Therefore, the ground area should not be placed directly below the monopole PCB lead antenna.

Kupfupisa, nheyo dzinotevera dzinofanira kuteedzerwa:

Ipa inoenderera uye yakaderera-yekumisikidza nzvimbo dzekumusoro sezvazvinogona.

Ose maviri magumo emutsetse wekuzadza akaiswa pasi, uye iyo-kuburikidza-gomba rondedzero inoshandiswa sezvinobvira.

Usatenderedza waya wakapfeka waya padhuze neRF wedunhu, usaise mhangura kutenderedza RF redunhu.

Kana bhodhi redunhu riine zvidimbu zvakati wandei, zvakanaka kuti uise pasi nepaburi apo tambo yechiratidzo inopfuura kubva kudivi kuenda kune rimwe.

Kunyanyisa kristall capacitance

Parasitic capacitance inokonzeresa iyo kristaro frequency kutsauka kubva pane yakakosha kukosha 9. Naizvozvo, mamwe marongero akajairwa anofanirwa kuteverwa kudzikamisa kudzikiswa kwemagetsi emakristini pini, mapedhi, waya, kana kubatana kune zvishandiso zveRF.

Iyi misimboti inotevera inofanira kuteverwa:

Iko kubatana pakati pekristaro neRF chishandiso kunofanirwa kuve kupfupi sezvinobvira.

Chengetedza wiring kubva kune mumwe nemumwe sezvazvinogona.

Kana iyo shunt parasitic capacitance yakakura kwazvo, bvisa nzvimbo yekumisikidza pazasi pekristaro.

Planar wiring inductance

Planar wiring or PCB spiral inductors are not recommended. Typical PCB manufacturing processes have certain inaccuracies, such as width and space tolerances, which greatly affect the accuracy of component values. Naizvozvo, mazhinji anodzorwa uye akakwirira Q inductors rudzi rwevanga. Kechipiri, iwe unogona kusarudza multilayer ceramic inductor, multilayer chip capacitor vagadziri vanopawo chigadzirwa ichi. Zvakangodaro, vamwe vagadziri vanosarudza vanonaya inductors pavanofanirwa. The standard formula for calculating planar spiral inductance is usually Wheeler’s formula 10:

Iko, a iri avhareji nharaunda yeiyoiri, in inches; N ndiyo nhamba yekutendeuka; C ndiyo hupamhi hwecoil core (router-rinner), in inches. Kana coil c “0.2a 11, iko kurongeka kwenzira yekuverenga iri mukati me5%.

Imwe-yakatenderera inonamira inductors yekwere, hexagonal, kana mamwe maumbirwo anogona kushandiswa. Kufungidzira kwakanaka kwazvo kunogona kuwanikwa kuenzanisira planar inductance pane yakasanganiswa mafuru wedunhu. Kuti uwane icho chinangwa, iyo yakajairwa Wheeler fomati inoshandurwa kuti iwane iyo ndege inductance yekufungidzira nzira yakakodzera kune diki saizi uye saizi saizi 12.

Iko, ρ chiyero chekuzadza :; N ndiyo nhamba yekutendeuka, uye dAVG ndiyo yepakati dhayamita:. Nezve square helices, K1 = 2.36, K2 = 2.75.

Kune zvikonzero zvakawanda zvekudzivisa kushandisa iyi mhando ye inductor, iyo inowanzo gonesa kudzikiswa inductance tsika nekuda kwenzvimbo nzvimbo. The main reasons for avoiding planar inductors are limited geometry and poor control of critical dimensions, which makes it impossible to predict inductor values. Uye zvakare, chaiyo inductance tsika yakaoma kudzora panguva yePBB kugadzirwa, uye inductance zvakare inowanzoita vaviri vaviri ruzha kune mamwe matunhu edunhu.