1, introduce

 

The architect of broadband amplifier needs to satisfy a variety of design requirement, for example, to a lot of application, broadband amplifier needs enough linear, and be total reflection is in in overtone frequency. In addition, to radar, the catapult of for military use application that is not broadcasting television will tell, amplifier is returned must can bear output end is broken tremendously match, these are the character of join antenna normally, terminal load, wait for the reason such as the reflex that measures equipment itself to cause. To these application, the able-bodied sex of amplifier, damage not easily that is to say become be of exceptional importance. What as a result of amplifier attaint brings about is immeasurable, mean project meeting to face serious and costly incur loss through delay, even the accrual of the lab also can get the loss.

 

Will tell from commercial angle, it is initiative investment no matter the following still moving cost is very important. Accordingly, high reliability and Yi Wei protect a gender to achieve the crucial factor of these targets namely. In addition, for the broadband amplifier to exceeding high-power, to reduce locomotive cost, still need as far as possible improve power efficiency. The 2nd part of the article will undertake bat around to this.

 

When for certain specific application searchs amplifier, the most important is each parameter that can explain clear-cut data table is medium, the way that different result puts manufacturer definition result to put parameter is different. How the 3rd part understands the proposal this parameter and contrast.

 

2, the challenge that amplifier of high power broadband designs

 

When designing amplifier of high power broadband, the engineer needs pair of bandwidth, gain, output power and the conduct character that match is broken below all sorts of extent and phasic condition, degree of linearity, harmonic is characteristic, power efficiency have integrated consideration, locate the target of the most serious first consideration from which.

 

These index are mutual influence mostly, to given for transistor type, the bandwidth of the design increases, the output power that can get can be reduced. What have challenge sex more is, to achieve greater output power, match network and corresponding result cent circuit, power synthesizes circuit to be able to become more difficult. In the meantime, result the service life that puts a valve special rely on amplifier medicinal powder the protective circuit that hot design and result put tubal periphery.

 

To A kind amplifier, transistor slants normally buy is on a bigger static electric current, the enlarge that can get a special linear so is characteristic, but bear poor power efficiency, bring to transistor very big medicinal powder hot pressing force. AB kind amplifier photograph compares A kind amplifier has small static state to slant buy electric current, can get very good linear character likewise, and good much power efficiency, of transistor medicinal powder hot pressing force gets reducing. Use push-pull structure to undertake circuit is designed normally.

 

For the influence of better understanding thermal stress to transistor service life, we are OK with the knot of typical LDMOS transistor lukewarm conduct character explains, if pursue,1 is shown. Say according to experience place, the knot is lukewarm reduce 10 degrees, transistor life can increase one times. If use GaN transistor, the knot reduces pair of life lukewarmly to have bigger gain. Present result puts a canal to be able to provide bigger RF power thickness, can realize the amplifier with more compact smaller size, the key of the design became how to design more efficient heat to sink a large number of heat energy that processing result puts tubal dissipation to come out. To A kind for amplifier, this comes true hard normally, need more transistor, reduce every transistor most high-power output, will handle medicinal powder hot difficult problem. Although such, a kind amplifier falls in the circumstance that inputs without radio frequency, still have very tall tie lukewarm, the reason depends on them having very big static state to slant buy electric current, should come loose when hot design processing is bad, service life can decrease greatly.

 

Graph 1, LDMOS transistor life follows leakage pole electric current to be in different knot is lukewarm the relation curve below, curve 1 written guarantee to 11 delegates lukewarm arrive from 100 °C 200 °C, the pace enters 10 °C

 

To a few application, not be to always need broadband amplifier to offer the greatest power to output, undertake EMS checks for example. Graph 2 those who show is in a 200 bend over / in the EMS system of rice, the power that amplifier increases to EMS antenna follows the calibration curve that frequency changes. Can see, the power output with different need will achieve corresponding field strong. If pursue 2 in of the description, be in 100MHz place, of need the biggest forward power is 1050 tile left and right sides, and be in in 200MHz and above frequency, what what need is the biggest forward power falls to be controlled to 600 tile, to certain frequency the dot can reduce 400 tile to control even. Accordingly, between these EMS application, AB kind amplifier photograph compares A kind amplifier has better efficiency, the knot with smaller transistor is lukewarm can bring longer service life.

 

Graph 2, in EMS test, to obtain 200 hot season / the field of rice is strong, what amplifier is outputted and aerial input end needs to achieve in different frequency location is forward power

 

Take no account of the type of amplifier of high power broadband, tall standing wave brings additional pressure to transistor than also be being met. Because reflex the radio frequency power that come back to also be met abreaction in amplifier circuit, the tie that this increased transistor further again is lukewarm. Compare attaint amplifier to prevent tall standing wave, must design efficient power dissipation circuit, this can heat up the distribution with equitable system to come true through coming loose, include to decorate hot sensor in relevant heat, the relevant voltage that also can pass monitoring transistor and electric current come true. Additional, result put stylist and products plan personnel to decide to whether add enough semiconductor power unit even, still can offer in order to make sure amplifier can be compared in very poor standing wave below the circumstance enough forward power, perhaps allow amplifier to compare next beginning that answer to retreat in certain standing wave. More semiconductor power unit mean the amplifier with higher cost, a higher price needs on the market.

 

3, the broadband amplifier with right choice

 

As an user, they do not care the design challenge that stylist place should face, need to ensure only the application that chooses an appropriate amplifier to satisfy his. And when choosing amplifier, can discovering a lot of target describe amplifier performance, if output power,the user needs a consideration not only, the technical index such as harmonic character, still need to consider to build the many main factors that maintain system of amplifier of whole high power. Bat around will undertake to this below.

 

3.1 amplifier output power

 

The meritorious service that puts manufacturer for comparative and different result puts output power index, compress output power to serve as referenced value with 1dB normally. This index defined amplifier gain to drop than small signal gain the corresponding output power when 1dB. Most manufacturer is with a certain frequency Duan Fan surrounds the output power inside to come the output power of nominal and whole amplifier, not be actually in all job frequency paragraph go up to be able to achieve nominal 1dB to reduce output power, the 1dB that the data of a few manufacturer offers on the watch compresses output power is on the low side. Accordingly, must contrast carefully the data that data expresses, and clear up curve of whole output power.

 

To application of catapult of a few high power, need considers the budget of whole system, normally the circumstance falls, aerial is in high frequency Duan Ke in order to provide bigger gain, the field that because this amplifier provides lesser output power,can achieve place need is strong. Such, to systematic frequency paragraph above the part is bought use smaller amplifier.

 

3.2 harmonic are characteristic

 

The harmonic of amplifier restrains what normally use DBc is described. Very important is, should affirm manufacturer evaluates harmonic to check data on what output power. It is usually power point is reduced in 1dB, but also having a few manufacturer is evaluated on low output power, because reduce output power, can get better harmonic character. Below this kind of circumstance, the harmonic when knowing amplifier reduces a point in 1dB very hard is characteristic. It is A no matter kind or it is AB kind amplifier, once drive reduces a point to 1dB over, baud sex meets humorous to worsen with nonlinear means.

 

What need a consideration additionally is, whether does the application that must be clear about oneself have a demand to harmonic character. E.g. , the harmonic of general amplifier is restrained nominal the value is to be in – 20dBc left and right sides, and actually – 15dBc was used quite, can get on amplifier drive to higher power so, same if need better harmonic character, be about to reduce output power appropriately, or the amplifier with choice greater power.

 

3.3 systems are designed

 

When searching appropriate amplifier, very crucial is to want to decide according to systematic environment the choice is compositive why to plant amplifier. Many more compositive to need frequency paragraph, choose radio frequency switch even, can be to be in result put input end, or it is output end, it is even in power sampling port. A few manufacturer can be offerred inside embedded switch, can avoid exterior switch so, reduce the difficulty that the system designs, also can be long-range control becomes more simple at the same time.

 

To a few application that receive or launch a system, be like radar and interference machine, amplifier can sudden mourn in silence is very useful. Normally the switch between requirement become silent and output is in a few delicate left and right sides, and the output power when become silent wants enough low, more adjacent – be restricted to had been jumped over by the thermal noise of 174dBm/Hz, this needs very high design skill, not all manufacturer can come true, because this needs more strict choice amplifier manufacturer.

 

When undertaking the system is designed, find different frequency paragraph the best combination of amplifier also is very important, according to long-term the customary practice since will come true often is not best method. Best is the requirement that understands a system deep, know every frequency paragraph needs exact power order and degree, especially the applied demand according to the system, make clear which frequency paragraph or be child frequency paragraph need by enlarge module is enclothed. Only such, ability gets already the plan that economy has superior technology index again

 

Expenses of 3.4 systems operation

 

The operation expenses of amplifier system basically has a system normal run time, the cost place that use and safeguards decides. This charge is the mainest project that cost has inside amplifier lifecycle, because this must try when choosing amplifier,consider.

 

Normal run time of the system is to depend on the able-bodied sex of amplifier, also can work normally below abominable condition for example not breakdown, it is the maintenance time after malfunctioning moreover, if amplifier cannot be used normally, crucial task may be critical, after the plan of the project can be delayed, it is to bring about battalion to receive an effect directly even.

 

The use cost of amplifier basically depends on power efficiency, tall power efficiency is representing low power to use up, fewer dissipation quantity of heat, and fewer processing comes loose hot cost, anyhow, it is fewer use cost. Accordingly, to including the great majority application of EMC of for military use, the proposal buys efficient amplifier, when needing freeboard to output power especially.

 

The run time to keep long and low maintenance cost, had better be the amplifier manufacturer that chooses to there are very good support and maintenance service in place. Present amplifier has long-range control function, can receive through LAN mouth undertake original breakdown fixed position and wrong analysis, this function can let safeguard become more simple.

 

And amplifier itself is designed also more safeguard easily, the BBA150 e.g. Lord and Shiwaci is modular amplifier, can let him user change inside very short time amplifier module. Final proposal is to choose to have industrialized productivity and the amplifier manufacturer that provide a service to support documentation to record, very good service still can get after only such ability make sure amplifier has been being used a few years.

 

4, summary

 

This paper described the challenge that stylist of broadband power amplifier faces when research and development, must undertake between the design index of many mutual influences eclectic ability gets best result iteration. Discussed A kind with AB kind the difference between amplifier, and the thermal stress influence to amplifier service life, offerred the proposal that makes ability of amplifier standing wave more able-bodied.

 

Discussed the factor that the consideration wants when choosing appropriate amplifier to specific applying, the data manual that must read different manufacturer product carefully will undertake function contrasts, make systematic requirement must consider when amplifier is compositive, often can get through optimizing a system to design more economic plan.

 

When consideration amplifier system has cost always, want to consider to purchase cost at first not only, the able-bodied sex that considers amplifier even and Yi Wei protect a gender, so OK the biggest spend total run time and life, reduce totle drilling cost.

 

Author: Lord and Shiwaci (China) Yang Hongwen of limited company of science and technology