The solution cent that enlarges these systems to cover range is two kinds: It is meshy network firstly, so as to goes to signal from change trains of a node next node; It is relevant technology secondly, for example blue tooth the error of 5 is corrective and algorithmic, it can restrict bit to be piled up by accident rate (BER) . Nevertheless, meshy network can increase complexity, and blue tooth the limits of 5 is patulous it is cost in order to lower data rate. Refer to “ please compatible blue tooth 4.1, 4.2 with the low power comsumption of 5 blue tooth SoC and tool can answer content couplet net to challenge (the 1st part) ” .

 

 

Replace model limits expands the solution is amplifier of will low noise (LNA) and power amplifier (PA) and combination of radio frequency chip, raise the ” of “ link budget of radio thereby. The module of radio frequency front that chooses to include LNA or LNA + PA (switch of FEM) , radio frequency and assemble enclosed logistic parts of an apparatus or appliance what use course test beforehand, can let magnify the design becomes easy.

 

Nevertheless, this kind of solution also is put in a few defect, include cost and dimension to be able to increase somewhat, power comsumption is taller also. Design personnel still must consider American FCC standard and the other international standard that about frequency of communal radio frequency Duan Zhongchuan loses power.

 

How article introduction RF FEM enlarges the system of short distance radio that is used at IoT application cover range, discuss its and the defect that replacement scheme compares, design circuit through applying give typical examples to explain.

 

2.4The balance of GHz job frequency

The radio engineering such as blue tooth of low power comsumption or Zigbee is based on a series of balance, be these balance created limitative range. Above all, what this technology uses is “2.4 GHz” (it is a center with 2.45 GHz) industry, scientific research and medical treatment (ISM) communal frequency paragraph, this frequency paragraph get the whole world is approbated and can use freely for any one party.

 

The place of the first balance is, although the frequency of support of thousand conspicuous frequency is wide taller, but enclothe limits to be able to narrow into scale. That is to say, in same power output falls, the transmission distance of signal of 2.4 GHz radio is inferior to be in 915 MHz (frequency of ISM of another kind of United States) the transmission distance of the radio signal of next jobs is far.

 

The place of the 2nd balance is, because want as common as a lot of other and wireless power source frequency paragraph, frequency of 2.4 GHz ISM paragraph the restriction that radio is facing emitter power side. Relevant provision is very complex, but basically be such regulations: Jump to lead number again and again little at 75 but achieve 15 at least (blue tooth of low power comsumption has 40) jump frequency system, the peak value that in its aerial input place measures projects power must demarcate is + 21 DBm; If omnidirectional antenna gain is more than 6 DBi, output still must reduce somewhat. Such, the biggest equivalent complete Xiang Fu shoots power (EIRP) is + 27 DBm. 1

 

The place of the 3rd balance is, blue tooth of low power comsumption and the design that Zigbee uses prolong battery life through restricting power comsumption to come to utmost ground. This one character applies to the application that has a lot of node, for example the wireless illume in large office building, because it can decrease,defend the work. The time that limitative radio is in high power to blast off or receives status but managing and much electric energy, but maker of radio frequency chip also can pass blue tooth of will low power comsumption to launch power demarcate to be + 4 DBm comes energy-saving (this is a general reason condition, sometimes also but demarcate is + 8 DBm, all allow under relevant standard far + 21 DBm) .

 

Letter a confusion of voices is compared (SNR) can be measured receiver is extracted correctly from inside environmental noise and the ability of decipher signal. Below threshold value SNR, BER can exceed the norms of radio, cause communication failure. For example, according to the design of receiver of blue tooth of low power comsumption, its are the biggest BER tolerance only 0.1% the left and right sides. According to the following formula, SNR is bit energy and noise density compare than (rate of Eb/No) , data (R) and receive bandwidth (the function of B) :

 

Formulary 1

 

Blue tooth of low now power comsumption and Zigbee are sent and receive implement hold concurrently tall receive sensitivity and adjustable the advantage that outputs power in order to increase link budget, make SNR is achieved thereby the biggest. The contemporary 2.4 GHz SoC such as Nordic Semiconductor NRF52832 and Texas Instruments CC2538 has budget of similar the biggest link, interpose at 100 to 110 DBm between. The radio frequency circuit of basis application circumstance and wireless product and antenna design a level, this kind of chip conduces to implementation below good case 80 to 100 meters cover range, typical residence can absorb radio frequency radiation because of wall and ceiling and put in radio of other 2.4 GHz the interference of the source, enclothe limits to be in so 10 reach 30 meters. In large house, for example wireless illume node can be located in controller collect line very easily implement enclothe limits bounds to go up, weaken reliable function and in the future system but expansibility.

 

Enlarge limits
 

Expand in blue tooth of low power comsumption or Zigbee application enclothe limits to have a few replacement scheme. One kind is to use meshy network, so as to is between node change trains signal, what ensure the system is outward thereby is outspread won’t exceed absolutely cover range. Meshy network still is had inside buy is redundant (breakdown node won’t bring about a system to break down, because change signal course easily) and shrink put simple dominant position. Its defect is complexity and project cost raise considerably.

 

Another kind of solution is inside buy seals packet of transmission error corrective function, so that can be flooded normally in signal,BER is reduced below the circumstance in noise. This is newest version (the 5th edition) low power comsumption is used at enlarging the technology that covers range in blue tooth technology. Its defect is corrective the systematic expense with the bigger need sealing a bag after, because of bandwidth of this meeting sacrifice.

 

The 3rd kind of plan is to raise SNR, increase link budget then and expand cover range. Design personnel to had used correct radio frequency circuit to design a principle to realize the optimum behavior of SoC of standard radio frequency or module suppose, so be about to use RF FEM next. Refer to “ please compatible blue tooth 4.1, 4.2 with the low power comsumption of 5 blue tooth SoC and tool can answer content couplet net to challenge (the 2nd part) ” .

 

Send and receive implement noise coefficient (the capacity that NF) uses at quantifying its to process signal in noise environment, it is going up somehow decided to send and receive implement the sensitivity that receives signal. Will send and receive implement cooperate to use with LNA can reduce NF and heighten sensitivity.

 

Use conformity what had been assembled and pass test and attestation is LNA, modular RF FEM is most the law of set prescription of simple circuit collect of effective. The RF FEM that suits this task has a lot of choices. For example, skyworks offers the SKY66113-11 that applies to blue tooth of low power comsumption, IEEE 802.15.4 and Zigbee application (graph 1) . This chip is compositive route of tall gain LNA, emissive bypass and digital control function. Gain is 12 DB normally, NF is 2 DB.

 

The SKY66113-11 sketch map of Skyworks

 

Graph 1: The SKY66113-11 of Skyworks controls LNA and number compositive. This parts of an apparatus still used by-pass switch, make a system OK do not have the job below the circumstance of LNA according to needing to be in. (picture origin: Skyworks)

 

The system that includes Nordic Semiconductor NRF52832 and SKY66113-11 with is exemple. According to norms, when link budget is 100 DB, the greatest sensitivity of chip of this radio frequency is – 96 DB, power of the biggest output is 4 DB. The norms of Nordic does not include NF data in the book, but the typical cost of this kind of chip is 8 DB about.

 

Accordingly, the NF of this system is:

 

Equality 2

 

Such raising will expand significantly cover range. Compare to facilitate, in similar application, sensitivity raises 6 DB to be able to expand of nearly one times cover range.

 

Heighten sensitivity besides use LNA outside, still can carry use PA to expand in emitter at the same time cover range. Current, offer on market at the same time compositive the RF FEM of LNA and PA. For example, the 2.4 GHz radio frequency that TI uses at blue tooth of low power comsumption and Zigbee for its is sent and receive implement offer CC2592 to add Cheng implement. Outside dividing LNA and PA, CC2592 FEM still includes radio frequency switch, radio frequency to match with Pianshangping judge lopsided converter, use at be being sent and receive with CC2538 Zigbee/6LoWPAN (IEEE 802.15.4) implement wait for parts of an apparatus to cooperate to use (graph 2) .

 

 

The Texas Instruments CC2592 that cooperates to use with SoC of CC2538 radio frequency adds Cheng implement sketch map

 

Graph 2: Add CC2592 Cheng implement cooperate to use with SoC of CC2538 radio frequency very simple. In this kind of layout, aerial and match circuit to join directly add Cheng implement SoC of radio frequency of and rather than. (use Digi-Key Scheme-it? The principle of scale pursues. Picture origin: Texas Instruments)