Radio frequency (RF) PCB design, what publishing publicly at present is theoretic have a lot of uncertainty, often be described to be ” of art of black of a kind of “ . Normally the circumstance falls, to microwave the following frequency paragraph circuit (include low frequency and circuit of low frequency number) , the careful program that mastering premise of principle of of all kinds design to fall in the round is the assurance of one-time successful design. To microwave above frequency the circuit of word of PC class number of Duan Hegao frequency. Need 2~3 the PCB of version just can assure circuit character. And to microwave above frequency paragraph RF circuit. Often need more version: PCB is designed and perfect ceaselessly, and it is to be in have quite below the premise of experience. From this the difficulty on design of knowable RF circuit.

 

If imitate circuit (radio frequency) work alone with digital circuit, may respective job is good. But, once put both,going up with a circuit board, use same power source works together, whole system is not stabilized probably. Because digital signal is in often,this basically is the ground and positive electricity source (” 3 V) between swing, and cycle is particularly short, often of accept second class. As a result of bigger amplitude and shorter switch time. Make these digital signal are included a large number of and independent the high frequency composition at switch frequency. In imitate part, from wireless tuning loop passes wireless equipment to receive partial signal to be less than LμV commonly. Because the difference between this number signal and radio frequency signal can achieve 120 DB. Apparent. If cannot make,digital signal and radio frequency signal depart well. Faint radio frequency signal may be destroyed, come so, wireless installation character of service can worsen, cannot work completely even.

 

 

Radio frequency circuit is quite sensitive to power source noise, mix to burr voltage especially other and high frequency harmonic. Small controller can be inside cycle of every in-house clock short time sucks electric current of part of National People’s Congress suddenly, because contemporary small controller uses CMOS craft to make,this is. Accordingly. Assume a small controller moves with the in-house clock frequency of LMHz, it will extract electric current from power source with this frequency. If do not take appropriate power supply,go Ou. Be sure to cause the voltage burr on power supply cord. If these voltage burr arrive at the power source of circuit RF part to cite a base, serious when the likelihood brings about working be no longer in force.

 

 

If the ground wire processing of RF circuit is undeserved, the possibility arises a few strange phenomena. To digital circuit design, although do not have ground wire layer, function of most number circuit also is behaved good. And in RF frequency paragraph, although a very short ground wire also is met,be like inductor same function. Calculate roughly, the inductance quantity of every millimeter length is L NH about, the inductance of circuitry of the 10 Toni PCB when 433 MHz makes an appointment with 27Ω . If do not use ground wire layer, most ground wire will longer, circuit will not have the character of the design.

 

In PCB circuit design, board go up to still have other imitate circuit normally. For example, there is a model on a lot of circuit, several changeover (ADC) or converter of several ／ model (DAC) . The high frequency signal that the antenna of radio frequency transmitter issues may arrive at the imitate of ADC to input end. Because any circuit circuitry are likely,be like aerial to be given out euqally or receive RF signal. If the processing of ADC input end is unreasonable, the self-excitation inside the ESD diode that RF signal may input in ADC. Cause ADC error thereby.

 

 

When devising RF overall arrangement, must below preferential full enough a few total principles:

 

An amplifier of as far as possible high power RF (HPA) with low noise amplifier (LNA) segregation leaves come, say simply, let high power RF launch circuit to be far from low power RF to receive circuit namely:

 

Ensure high power division has a whole land at least on PCB board, best above did not cross aperture, of course, copper Foil area has been jumped over greatly more;

 

Circuit and power source go Ou is same very important also;

 

RF output needs to be far from RF input normally;

 

Sensitive imitate signal should be far from signal of high speed number and RF signal as far as possible.

 

Design partition can be decomposed for physical partition and electric partition. Physical partition basically involves layout of yuan of parts of an apparatus, direction and screen to wait; Electric partition can continue to decompose the partition that walks along line, sensitive circuit and signal and ground connection to wait for power source allocation, RF.

 

 

Yuan principle of position of position of parts of an apparatus. Yuan layout of parts of an apparatus is the key that realizes design of an outstanding RF. The most effective technology is to originally to be located in yuan of parts of an apparatus on RF method to adjust its direction surely above all, so that reduce the length of RF method the smallest, make the input is far from output. Depart far as far as possible high power circuit and low power circuit.

 

PCB pile designs a principle. The most effective circuit board pile method is will advocate ground plane (advocate the ground) the 2nd when arrangement falls in surface layer, arrange RF line as far as possible go up in surface layer. The dimension crossing aperture that gets on RF method is decreased the smallest, this can reduce method inductance not only, and still can decrease advocate the empty solder dot on the ground, can reduce RF energy leak to arrive inside cascade board the opportunity of other area.

 

Radio frequency parts of an apparatus reachs principle of layout of its RF wiring. On physical space, like multistage amplifier normally enough general keeps apart such linear circuit to come each other between many RF area, but ／ first detector always has diplexer, first detector and intermediate frequency amplifier signal of IF of many RF ／ is disturbed each other. Because this must take care,the ground reduces this one effect the smallest. RF and IF trace should as far as possible crossed across, lie between a ground between them as far as possible. Right RF way is very important to making the property of a PCB, this is layout of yuan of parts of an apparatus design in beehive phone PCB normally in the account that takes major time.

 

Reduce tall / the design principle of coupling of interference of low power parts of an apparatus. On beehive phone PCB, can put circuit of low noise amplifier in some one side of PCB normally, and amplifier of will high power is put in other one side, be in them finally through diplexer on same area on the antenna that joins RF end and base band processor are carried. Should ensure with skill via won’t RF energy from board deliver another at the same time, commonly used technology is to be in 2 to use blind opening. Can be in through arranging via 2 area that do not get RF interference come to PCB board reduce the adverse effect of via the smallest.

 

 

Power transmits a principle. The dc electric current of most circuit in beehive phone is quite small, accordingly, wiring width is not a problem normally. Nevertheless. The power source that must be high power amplifier is sole set as far as possible line of broad big electric current, press with will be being transmitted fall decrease lowest. To avoid loss of too much electric current, need uses many via to transmit electricity another from some layer.

 

The power source of high power parts of an apparatus goes Ou. If cannot be in,the power source of high power amplifier brings crural end to undertake going adequately to it Ou, noise of so high power will radiation goes to whole board on, bring diversiform issue. The ground connection of high power amplifier is quite crucial, often need to design cover of screen of a metal for its.

 

RF input, output keeps apart a principle. Below most circumstance, likewise crucial is to ensure RF output is far from RF input. This also applies to amplifier, bumper and filter. Below worst circumstance, if amplifier is mixed the output of bumper with proper phasic input end to theirs with amplitude feedback, so they produce self-oscillation likely. Below best circumstance, their aux will be able to leaves steadily job in any temperature and voltage condition. Actually. They may become not stable, add noise and intermodulation signal to RF signal.

 

Filter input, output keeps apart a principle. If radio frequency line must carry retrace to output end from the input of filter, so, this may damage the belt of filter badly to know character. To make input and output good segregation. Must be above all all round filter decorate circuit ground. Next area of filter lower level also should decorate a ground, and with around filter advocate ground join rises. Be far from the line that needs to cross filter as far as possible filter cites a base also is a good method. In addition, whole board on the ground connection of each places wants very careful, may be in otherwise incognizant in the coupling channel that introduces not to hope to happen.

 

Digital circuit and imitate circuit are kept apart. In all PCB design, be far from digital circuit imitate circuit as far as possible is a total principle, it applies to RF PCB design likewise. Communal imitate ground and be being used at screen and the ground that separate line is coequal and important normally, the design that causes as a result of neglect is changed bring about the likelihood the design that is about to complete to must be overturned again come again. Should make RF line great distance is mixed from imitate circuitry likewise a few very crucial number signal. All RF walk along Pan Heyuan of line, solder all round should fill skin of ground connection copper more as far as possible. And as far as possible with advocate the ground is linked together. If RF walks along a line to must cross line, so walk along a line to decorate along RF between them as far as possible with advocate the ground that the ground is linked together. If impossible, must make sure they are crossed across. This can decrease the coupling that allow a gender the smallest, take a line in every RF as far as possible at the same time all round much cloth a few ground, go to them repeatedly advocate the ground. In addition. Will collateral RF walks along the distance between the line to be decreased the smallest can make perceptual coupling is decreased the smallest.

 

 

The radio frequency integrated circuit that develops quickly offerred capacious prospect to be engaged in the project technology personnel of of all kinds and wireless communication. But at the same time, the design of radio frequency circuit asks the architect has certain practice experience and engineering design capacity. A few experience that the article sums up can help developer of radio frequency integrated circuit shorten development cycle. Avoid needless crooked road, save manpower material resources.