The noun defines (TRP: Emissive power, TIS: Admit sensitivity)

 

In wireless network, radio frequency module has conduct TRP and conduct TIS two main index, and after module mount antenna, overall need to check TRP and TIS in OTA darkroom, here we are its definition radiation TRP and radiation TIS. Radiation TRP won’t give an issue commonly, and the interference that radiation TIS suffers noise of product interior electromagnetism easily. Do not amount to mark when radiation TIS when, want to consider to conduct TIS to whether amount to mark above all, the parts of an apparatus in conducting TIS and radio frequency circuit (if the segregation of diplexer is spent) , of each circuit match wait for an element to concern. Flow of work of part of radio frequency circuit is as follows:

 

Receive: Aerial → matchs → of circuit → diplexer sound expresses filter (amplifier of SAW) → low noise (LNA) → first detector

 

Blast off: Aerial←Match circuit←Diplexer←Power amplifier (PA)←First detector

 

After conducting TIS to amount to mark, the electromagnetism of interior of our reconditioning product is disturbed. Nowhere is absent electromagnetism interference, frequency of product interior job and its overtone frequency are as high as 1G above, when interference frequency falls when aerial receives frequency range, can affect TIS. Explain through a few case electromagnetism disturbs the influence of pair of radiation TIS below.

 

Case one: Noise of the clock of the DDR in intelligent POS machine, clock of screen and data, ground affects 4G antenna TIS.

 

 

Present a problem:

 

In intelligent POS machine, 4G antenna FDD Ban5/8 checks TIS value to be in OTA darkroom – 78dB, radiation TIS is unqualified (eligible value is – 91dBm) , and radiation TRP and module conduct TRP and TIS to amount to mark.

 

Analytic problem:

 

Conduct TRP and TIS to amount to mark, explain module itself does not have a problem; Radiation TRP amounts to mark, explain aerial also is no problem, and radiation TIS is only – 78dBm, can deciding is disturbing influence of product interior electromagnetism admit sensitivity. Apply spectrum appearance to diagnose interference cause, interference of the clock needing branch of the clock frequency that discovers CPU and DDR and screen, data is very big (pursue as follows) .

 

 

Solve a problem:

 

1.Reduce the drive capacity of DDR clock appropriately through software, TIS is worth from – 78dBm promotion arrived – 80dBm, all round the screen shell that uses stannic general CPU and DDR upper part as good as PCB ground solder, TIS is worth from – 80dBm promotion arrived – 83dBm (build shield solder to absolutely refuse to to accord with a quantity to produce with stannum, change from the back board build screen clincher take out, rim of clincher instead metal, metallic rim and PCB land are good solder, next screen lid card takes metallic draw a frame round, test TIS can be amounted to – 82dBm. )

 

Brief summary: The action that screen covers is screen space radiate, action 2 it is bear ground loop, abate in all modular noise.

 

2.After solder good screen is built, discharge screen wire screen with electric cloth and two end earthed, test TIS value can be amounted to – 86dBm. (change board hind the poor time-sharing bell in screen and data string together a 90Ω to each in all modular inductance, at the same time will original screen FFC discharges line instead FPC to discharge a line, test TIS can be amounted to – 88dbm.

 

Brief summary: Next graphs are 90Ω in all the frequency character graph of modular inductance, what 90Ω points to is frequency when 100MHz in all modular impedance, in all modular impedance changes as the change of frequency, when 800MHz-960MHz in all modular impedance is as high as 600Ω , so in all modular inductance is right of 800MHz-960MHz in all modular noise has very good inhibition the effect; FPC discharges a line to have screen effect, can provide ground return to signal at the same time.

 

 

3.The electric cotton take out that connects the iron plate after screen and PCB ground, withhold aerial to receive electric cotton of the position only, test TIS can be amounted to – 91dBm, final radiate TIS amounts to mark.

 

Brief summary: The form that ground noise transmits is electric current, electric current flows toward the way with small impedance, the ground noise on PCB can flow to rear cover metal through electric cotton, the ground connection that flows to aerial through rear cover next.

 

Case 2: Intermediate frequency of intelligent sound box slants the TIS that affects WIFI antenna.

 

 

Present a problem:

 

Test of antenna of the 2.4G WIFI in intelligent sound box is conducted, radiant TRP and TIS do not amount to mark, the standing wave of aerial is compared, the parameter such as echo loss is normal.

 

Analytic problem:

 

Conduct TRP and TIS unqualified, show issue of module itself existence; Through adjusting of each circuit match, TRP and TIS do not have apparent promotion, examine emissive frequency through spectrum appearance, discover its frequency deflection, frequency slants the problem considers brilliant above all brace up, because of brilliant brace up fiducial frequency error is big, can cause frequency of signal of this locality oscillation to slant, signal of this locality oscillation is the one share that synthesis blasts off and receives frequency.

 

Solve a problem:

 

Pursue as follows, through adjusting brilliant brace up a distribution look CG of both sides and CD, take value 10pF finally, make blast off and receive frequency to be inside standard limits, check TRP and TIS qualification finally.

 

Brief summary: Laden capacitance is brilliant brace up a parameter that produces fiducial frequency, laden capacitance included CG, CD and capacitance of parasitism taking a line and chip to carry equivalent capacitance, capacitance of parasitism taking a line and chip end are equivalent capacitance is bad accuse, so need periphery CG, CD adjusts.  

 

     

 

Case 3: The DC-DC in journey recorder and the reception that photograph the noise that resembles a head to affect GPS antenna sensitivity

 

 

Present a problem:

 

Antenna of the GPS in journey recorder checks radiation TIS not to amount to mark, and TRP and conduct TIS to satisfy a requirement. The standing wave of aerial is compared, the parameter such as echo loss is normal, can deciding so basically is disturbing influence of product interior electromagnetism admit sensitivity.

 

Analytic problem:

 

Apply spectrum appearance to diagnose interference cause, the ripple noise that discovers the DC-DC that be in a poor light is outputted and the harmonic interference that photograph clock resembling a head are very big, in experimental process, adjust the brightness of frequency and shut photograph like the head, search star number and astral value have promotion, decided the TIS that be in a poor light and photographed the noise that resembles a head to disturb GPS antenna.

 

Solve a problem:

 

1. pursues as follows, string together 120Ω magnetism on MCLK and PCLK line respectively bead, the magnetism of MCLK bead near chip end, magnetism bead strings together PCLK on-line in photograph end resembling a head, search star number and astral value have certain promotion.

 

Brief summary: The position that magnetism bead sets is to near source end, such abate the intermediate radiate that takes a line partly and coupling interference. MCLK gives out by chip, and PCLK by photograph hair resembling a head to go out.

 

 

2.Pursue as follows, DC-DC output carries the electric capacity that increases a 10pF, bead filter divides the magnetism that strings together 120Ω after capacitance next ripple, number of star of final GPS search and astral value amount to mark.

 

Brief summary: Pass computation, the frequency effect that the capacitance filter that 10pF controls removes 1.575GHz is too optimal, and the size of magnetism bead and the changeover efficiency that placement position can affect DC-DC, magnetism bead is placed commonly after capacitance.

 

 

Summary: The electromagnetism interference with product common interior has DDR, hold, photograph the harmonic noise that resembles first class clock and DC-DC ripple noise, ground noise to wait. PCB designs initial stage to need to consider EMC design, fine line of cloth good bureau, cloth, design of high frequency line is strung together in all modular inductance or magnetism bead the position, voltage line design is strung together magnetism bead is mixed and capacitance position is waited a moment, avoid to change again board, shorten research and development is periodic.