Kiisas badan oo dalab oo ah alaabada soo noqnoqoshada raadiyaha warshadaha, sayniska, iyo caafimaadka (ISM-RF) ayaa muujinaya in guddiga wareegsan oo daabacan qaabeynta badeecooyinkan ayaa u nugul cillado kala duwan.Dadku waxay inta badan ogaadaan in isla IC lagu rakibay laba loox oo wareeg ah oo kala duwan, tilmaamayaasha waxqabadku aad bay u kala duwanaan doonaan. 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. Waraaqdan, fr-4 dielectric, 0.0625in dhumucda PCB lakabka labajibbaaran, tusaale ahaan, guddiga wareegga dhulka. Operating in different frequency bands between 315MHz and 915MHz, Tx and Rx power between -120dbm and +13dBm.

Jihada aan tooska ahayn

Marka laba indheeye (ama xitaa laba khad PCB) ay isu dhow yihiin, isdhaafsi labada dhinac ah ayaa dhici doona. 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:

Halkee, YB waa danab qalad ah oo lagu muday wareegga B, IA waa 1 hadda ku shaqaynaya wareegga A. LM aad bay u xasaasi u tahay kala fogaanshaha wareegga, aagga loop inductance (ie, qulqulka magnetka), iyo jihada loop. 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. Ujeedadaas awgeed, sida ugu badan ee suurtogalka ah ee midba midka kale, fadlan tixraac khariidadda wareegga ee awoodda hoose FSK superheterodyne Receiver Evaluation (EV) (MAX7042EVKIT) (Jaantuska 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.

Jaantuska 2. Laba qaab -dhismeed PCB oo kala duwan ayaa la muujiyey, mid ka mid ah ayaa leh walxaha loo habeeyay jihada khaldan (L1 iyo L3), halka kan kalena uu ku habboon yahay.

Isku soo wada duuboo, mabaadiida soo socota waa in la raaco:

Kala fogeynta inductance waa inay ahaataa sida ugu macquulsan.

Inductors -ka waxaa loo habeeyay xaglo qumman si loo yareeyo waddada u dhexeysa indho -indheeyayaasha.

Hoggaamiya isku xidhka

Sida jihaynta inductors -ku u saameyso isku xirnaanta birlabka, sidaas oo kale isku -xirku haddii hoggaamiyeyaashu aad isugu dhow yihiin. Dhibaatada qaab -dhismeedka noocan oo kale ah waxay kaloo soo saartaa waxa la yiraahdo dareen wadaagga. Mid ka mid ah dhibaatooyinka ugu walaaca badan ee wareegga RF waa xarigga qeybaha xasaasiga ah ee nidaamka, sida shabakadda is -waafajinta soo -gelinta, kanaalka dib -u -qaataha ee qaataha, shabakadda u dhiganta antenna ee gudbiyaha, iwm.

Jidka soo noqoshada hadda waa inuu ahaadaa mid u dhow dariiqa ugu weyn ee hadda jira ee suurtogalka ah si loo yareeyo aagga magnetka shucaaca. This arrangement helps to reduce the current loop area. Jidka iska -caabbinta ugu habboon ee ku -soo -noqoshada badiyaa waa dhulka dhulka ka hooseeya macdanta – si wax -ku -ool ah u xaddidaya aagga loop -ga gobol halkaas oo dhumucda korontada lagu dhufto dhererka hogaanka. Si kastaba ha noqotee, haddii dhulka dhulku kala qaybsamo, aagga wareegga ayaa kordha (Jaantuska 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.

Jaantuska 3. Dhul -balaadhsiga oo dhammaystiran wuxuu caawiyaa hagaajinta waxqabadka nidaamka

Wixii inductor -ka dhabta ah, jihada hogaamintu waxay sidoo kale saamayn weyn ku leedahay isku -xidhka goobta magnetka. Haddii hoggaamiyeyaasha wareegga xasaasiga ahi ay isu dhow yihiin, waxaa habboon in la toosinayo hoggaamiyeyaasha si toos ah si loo yareeyo isku -xidhka (Jaantuska 4). If vertical alignment is not possible, consider using a guard line. Naqshadeynta siligga badbaadinta, fadlan tixraac qeybta daweynta iyo buuxinta qeybta hoose.

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.

Sensitive leads should be arranged vertically.

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

Grounding via

Dhibaatada ugu weyn ee khariidadda wareegga RF badiyaa waa is -beddelka astaamaha ugu sarreeya ee wareegga, oo ay ku jiraan qaybaha wareegga iyo isku -xirkooda. Macdanta leh dabool naxaas ah oo khafiif ah waxay u dhigantaa siligga inductance waxayna samaysaa awood qaybin leh tilmaamo kale oo agagaarka ah. Macdanta ayaa sidoo kale soo bandhigaysa indho -indhayn iyo sifooyin karti marka ay dhex marayso daloolka.

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. Saamaynta awoodda dulinka guud ahaan way yar tahay badanaana waxay kaliya ku keentaa kala-duwanaansho cidhif ah oo ku jira calaamadaha dhijitaalka ah ee xawaaraha sare leh (oo aan warqaddan lagaga hadlin).

Saamaynta ugu weyn ee daloolka-daloolka ayaa ah inductance-ka dulin-ka ee uu sababay hab isku-xirnaanta u dhiganta. 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 waa dhexroorka godka daloolka, in inches 2.

Sida looga fogaado cillado kala duwan ee qaabeynta PCB ee looxyada daabacan

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. Awood-siiyaasha ku-meel-gaadhka ah ee habboon waxay bixiyaan wareegyo gaagaaban oo soo noqnoqda oo u dhexeeya aagga sahayda iyo samayska, laakiin daloollada aan habboonayn waxay saamayn ku yeelan karaan waddada xasaasiga ah ee u dhexaysa samaynta iyo aagga sahayda. A typical PCB through hole (d = 10 mil, h = 62.5 mil) is approximately equivalent to a 1.34nH inductor. Marka la eego soo noqnoqoshada hawlgalka gaarka ah ee badeecada ISM-RF, dalooladu waxay si xun u saamayn karaan wareegyada xasaasiga ah sida wareegyada kanaalka soo noqnoqda, shaandhaynta, iyo shabakadaha iswaafajiya.

Dhibaatooyin kale ayaa soo ifbaxa haddii wareegyada xasaasiga ahi ay wadaagaan godadka, sida labada gacmood ee shabakadda nooca π. Tusaale ahaan, iyadoo la dhigayo dalool ku habboon oo u dhigma indho -ku -duubnaan, qaab -dhismeedka u dhigma ayaa aad uga duwan naqshadda wareegga asalka ah (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

Jaantuska 6. Fikradaha ku habboon iyo qaab-dhismeedyada aan ku habboonayn, waxaa jira “dariiqyo calaamad” ah oo ku jira wareegga.

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.

Dhererka hogaanka

Macluumaadka badeecada Maxim ISM-RF badiyaa wuxuu ku taliyaa in la adeegsado soo-gelinta soo noqnoqoshada-soo-noqnoqoshada iyo soo-saarka ugu yar ee suurtogalka ah si loo yareeyo khasaaraha iyo shucaaca. Dhinaca kale, khasaaraha noocan oo kale ah waxaa inta badan sababa xad-gudubyada dulinka ah ee aan habboonayn, sidaa darteed labada indho-indhayn iyo awood-qaadis ayaa saameeya qaab-dhismeedka wareegga, iyo adeegsiga macdanta ugu gaaban ee suurtogalka ah waxay gacan ka geysaneysaa yareynta xuduudaha dulinka. 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. Wareegga LAN/ mixer oo leh 20nH inductor iyo 3pF capacitor, qiimaha qaybta wax ku oolka ah ayaa si weyn u saamayn doonta marka wareegga iyo qaabaynta qaybtu aad u yar yihiin.

Ipc-d-317a4 in ‘Institute for Printed Circuits’ provides an industry standard equation for estimating various impedance parameters of microstrip PCB. Dukumentigan waxaa lagu beddelay 2003 IPC-2251 5, kaas oo siiya hab xisaabeed sax ah oo loogu talagalay hoggaamiyeyaasha PCB kala duwan. 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:

Qaaciddada, εr waa joogtaynta korontada ee dielectric, h waa dhererka leedhka ka imanaya stratum, W waa ballaca rasaasta, Tna waa dhumucda rasaasta (FIG. 7). Marka w/h u dhexeeyo 0.1 iyo 2.0 oo εr u dhexeeyo 1 iyo 15, natiijooyinka xisaabinta ee qaacidadani waa kuwo sax ah.

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. Tusaalahan, waxaan ka wada hadalnaa kartida qaldan iyo indha -indheynta. The standard equation of characteristic capacitance for microstrip lines is:

Sidoo kale, inductance -ka dabeecadda waxaa laga xisaabin karaa isla’egta iyadoo la adeegsanayo isla’egta kor ku xusan:

Tusaale ahaan, u qaad dhumucda PCB ee 0.0625in. (h = 62.5 mil), 1 wiqiyadood oo ah naxaas dahaarka leh (t = 1.35 mil), 0.01in. (w = 10 mil), iyo guddiga FR-4. Ogsoonow in ε R ee FR-4 uu caadi ahaan yahay 4.35 farad/m (F/m), laakiin wuxuu u dhexayn karaa 4.0F/m ilaa 4.7F/m. Eigenvalues ​​lagu xisaabiyo tusaalahan waa Z0 = 134 ω, C0 = 1.04pF/gudaha, L0 = 18.7nH/gudaha.

Naqshadda ISM-RF, dhererka qaabeynta 12.7mm (0.5in) ee hogaamiyaasha sabuuradda waxay soo saari kartaa cabbirro dulin ah oo qiyaastii 0.5pF ah iyo 9.3nH (Jaantuska 8). Saamaynta cabbirrada dulinka ah ee heerkan ku jira kanaalka dib -u -qaataha ee soo -dhoweeyaha (kala -duwanaanta alaabta LC) waxay ku dambayn kartaa 315MHz ± 2% ama 433.92mhz ± 3.5% kala duwanaansho. Sababtoo ah kartida dheeraadka ah iyo kicinta ay sababtay saamaynta dulinka ee macdanta, heerka ugu sarreeya ee soo noqnoqoshada 315MHz wuxuu gaaraa 312.17mhz, halka ugu sarreysa 433.92mhz soo noqnoqoshada oscillation -ka ayaa gaartay 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. Xisaabi inta jeer ee oscillation of circuit resonant adigoo isticmaalaya isla’egta:

Qiimaynta wareegga wareegsan ee saxanka waa inay ku jirtaa saamaynta dulinka ee xirmada iyo qaabeynta, iyo cabbirrada dulinka waa 7.3PF iyo 7.5PF siday u kala horreeyaan marka la xisaabinayo inta jeer ee soo noqnoqonaysa 315MHz. Ogsoonow in badeecadda LC ay ka dhigan tahay karti -duuban.

Isku soo wada duuboo, mabaadiida soo socota waa in la raaco:

Ka dhig hogaanka sida ugu macquulsan.

Dhig wareegyada muhiimka ah sida ugu dhow aaladda

Qaybaha muhiimka ah waxaa lagu magdhabaa si waafaqsan dulinka guud.

Daaweynta dhulka iyo buuxinta

The grounding or power layer defines a common reference voltage that supplies power to all parts of the system through a low resistance path. Isbarbar dhigga dhammaan goobaha korontada ayaa sidan u soo saarta farsamo gaashaan oo wanaagsan.

Awoodda tooska ahi had iyo jeer waxay u egtahay inay ku socoto waddo iska caabin hooseysa. Sidaas si la mid ah, hadda soo noqnoqoshada badan ayaa doorbidaya in uu maro waddada leh iska caabbinta ugu hooseysa. 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).

Sida looga fogaado cillado kala duwan ee qaabeynta PCB ee looxyada daabacan

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. Ha isku darin siligga waardiyaha leh leedhka loogu talagalay inuu bixiyo soo noqoshada waddada hadda jirta. Qabanqaabadani waxay soo bandhigi kartaa dariiqa wada -hadalka.

Sida looga fogaado cillado kala duwan ee qaabeynta PCB ee looxyada daabacan

FIG. 10. Naqshadda nidaamka RF waa in ay ka fogaato sabbadaha fiilooyinka xiran ee naxaasta ah, gaar ahaan haddii loo baahdo in la daboolo naxaasta.

Aagga naxaasku xidhan yahay ma aha mid sal leh (sabeynaya) ama aan sal ku lahayn hal dhinac oo keliya, kaas oo xaddidaya waxtarkiisa. 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. Marka la soo koobo, haddii qayb ka mid ah dahaarka naxaas ah (fiilooyinka signaalka aan wareegga ahayn) la dul saaray guddiga wareegga si loo hubiyo dhumucda dahaadhka oo joogto ah. Aagagga naxaasta xiran waa in laga fogaadaa maadaama ay saameynayaan naqshadda wareegga.

Ugu dambayntii, hubso inaad tixgeliso saamaynta aag kasta oo dhulka u dhow anteenada. Anteeno kasta oo monopole ah waxay lahaan doontaa dhulka dhulka, fiilooyinka iyo daloolada oo qayb ka ah isu-dheellitirka nidaamka, iyo fiilooyinka dheelitirka aan habboonayn waxay saamayn ku yeelan doontaa shucaaca iyo jihada anteenada (template shucaaca). Therefore, the ground area should not be placed directly below the monopole PCB lead antenna.

Isku soo wada duuboo, mabaadiida soo socota waa in la raaco:

Sii aagag dhulka hoostiisa ah oo joogto ah oo iska caabin hooseeya intii suurtogal ah.

Labada daraf ee xariiqda buuxinta ayaa saldhig u ah, oo dalool dalool ayaa loo adeegsadaa sida ugu macquulsan.

Ha dul sabayn siligga dahaarka leh ee naxaasiga ah ee u dhow wareegga RF, ha dhigin naxa ku wareegsan wareegga RF.

Haddii boodhka wareegga uu ka kooban yahay lakabyo badan, waxaa fiican inaad dhulka dhigto daloolka marka fiilada signalada ay dhinac ka gudubto.

Capitance crystal xad -dhaaf ah

Awoodda dulinka ayaa sababi doonta soo noqnoqoshada garaaca inay ka weecato qiimaha bartilmaameedka 9. Sidaa darteed, qaar ka mid ah tilmaamaha guud waa in la raaco si loo yareeyo awoodda baadi ee biinanka macmacaanka ah, suufka, fiilooyinka, ama ku xirnaanta aaladaha RF.

Mabaadiida soo socota waa in la raaco:

Xiriirka ka dhexeeya qalabka crystal iyo RF waa inuu ahaadaa mid gaaban intii suurtogal ah.

Ka ilaali xargaha midba midka kale intii suurtogal ah.

Haddii awoodda dulinka dulinka ahi aad u weyn tahay, ka saar dhulka dhulka hoostiisa ka hooseeya bahalka.

Indha -indhaynta taararka qorshaysan

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. Sidaa darteed, inta badan inductors -ka Q ee la kontoroolo iyo kuwa sarreeya waa nooca nabarrada. Marka labaad, waxaad dooran kartaa inductor dhoobada dhoobada badan leh, soosaarayaasha kaarboon -kariska jibbaarada badan ayaa sidoo kale bixiya badeecadan. Si kastaba ha noqotee, naqshadeeyayaasha qaarkood waxay doortaan inductors spiral markay tahay inay sameeyaan. The standard formula for calculating planar spiral inductance is usually Wheeler’s formula 10:

Halkee, a waa celceliska gacan -ka -qabadka ee gariiradda, in inches; N waa tirada wareegyada; C waa ballaca xuddunta gariiradda (router-rinner), in inches. Marka gariiradda c “0.2a 11, saxnaanta habka xisaabintu waxay ku jirtaa 5%.

Indho-indheeyayaasha hal-lakabka ah ee laba jibbaaran, laba-geesle, ama qaabab kale ayaa la isticmaali karaa. Qiyaaso aad u wanaagsan ayaa laga heli karaa in lagu daydo inductance planar on wafer circuit oo isku dhafan. Si loo gaaro hadafkan, qaaciddada caadiga ah ee Wheeler ayaa wax laga beddelay si loo helo hab lagu qiyaaso inductance diyaarad ku habboon cabbir yar iyo cabbir laba jibbaaran 12.

Halkee, ρ waa saamiga buuxinta :; N waa tirada wareegyada, iyo dAVG waa dhexroorka celceliska:. Helicoparrada laba jibbaaran, K1 = 2.36, K2 = 2.75.

Waxaa jira sababo badan oo looga fogaado adeegsiga inductor -ka noocan ah, taas oo inta badan keenta in la yareeyo qiimayaasha indho -indhaynta sababtuna tahay xaddidnaanta booska. The main reasons for avoiding planar inductors are limited geometry and poor control of critical dimensions, which makes it impossible to predict inductor values. Intaa waxaa dheer, qiimayaasha inductance dhabta ah way adag tahay in la xakameeyo inta lagu guda jiro wax soo saarka PCB, iyo inductance sidoo kale waxay u egtahay inay qaylada qaylada qaybaha kale ee wareegga.