CN204046524U - Single-stage low noise amplifier - Google Patents

Abstract

The utility model discloses a kind of single-stage low noise amplifier, it is characterized in that: comprise, input high pass impedance matching network, output high pass impedance matching network, input high pass impedance matching network selects band resistance to add varactor high pass filter structure, wherein, input high pass impedance matching network and export high pass impedance matching network and be π type matching network; Input high pass impedance matching network includes to be connected the capacitor combination part formed by variable capacitance diode; Also comprise by 1R99 1R100 1C165 1R104 for grid provide biasing circuit, by 1R94 1L151 1L53 1C163 for drain electrode biasing circuit is provided, described output high pass impedance matching network comprises output stage band pass filter.Single-stage low noise amplifier described in the utility model, this product main feature: modularization, miniaturization, low noise, gain is high, Out-of-band rejection performance is good, low-power consumption, operating voltage is low, reliability is high, the temperature range that conforms wide (-30-+60 DEG C).

Description

Single-stage low noise amplifier

Technical field

The utility model relates to a kind of amplifier, is specifically a kind of single-stage low noise amplifier.

Background technology

Electronics and information industry is still the strategic emphasis of global competition, information hierarchy promotes industrial pattern generation major transformation, industrial repositioning upgrading expedites the emergence of new industry growth point, domestic and international market environment opportunities and challenges depositing.Along with the enforcement that China 12 plans, the development of information-based industry will cause new round information technology revolution and Industrial Revolution, be the commanding elevation of information industry field future competition and the core driver of industrial upgrading.Huge commercial opportunities have been there are in technical field of radio frequency/microwave and information processing high speed, diversification field.In today of the develop rapidly of electronic information industry, the requirement of people to various wireless telecommunications system is also more and more higher.Require that radiation of power is little, operating distance is far away, coverage is large.Become the generally pursuit of each operator and even wireless telecommunications system manufacturer, this just has higher requirement to the receiving sensitivity of system.

In a communications system, the important indicator weighing communication quality is signal to noise ratio, and the key improving signal to noise ratio is just the noise factor reducing receiver.If connect high performance low noise amplifier in the front end of receiving system, when low noise amplifier gain is enough large, the noise of late-class circuit just can be suppressed.A receiver system with low noise amplifier, its total noise of centrifuge coefficient will reduce greatly, thus sensitivity improves greatly.The performance of microwave low-noise amplifier constrains the performance of whole receiving system as can be seen here, for the raising of whole receiving system technical merit, also play conclusive effect.In addition, in a communications system, low power supply, low-power consumption are also very important technical indicators, and reason is in the communications, and when receiver is in wait state, radio-frequency (RF) front-end circuit is always in running order, and low-power consumption is very important.Therefore the research again of microwave low-noise amplifier is had great importance.

In international satellite communication application, the target of low noise amplifier development is that performance improves and cost reduces.It is exactly that the bandwidth sum of broadening low noise amplifier reduces its noise temperature that performance improves, and constantly meets the traffic increasing sharply year after year.Cost lowers can be competed with submarine cable system exactly mutually.And the noise temperature reducing low noise amplifier reduces the most effective method of one of satellite communication system cost, because the diameter of earth station antenna can reduce by improving noise temperature performance.

Utility model content

The purpose of this utility model is to provide a kind of single-stage low noise amplifier at this, low noise amplifier has actual application value widely, be mainly reflected on RF/Microwave parts crucial in the electronic equipments such as radar, communication, satellite, electronic countermeasures, remote measurement, remote control, it is the critical piece of radio-frequency receiver front-end, (be attended by many high reject signals signal to be mixed into from restraint speckle interference while signal sent here by antenna or antenna filter in amplification, outer and the image frequency interference of inhibition zone), raising system sensitivity.Noise factor due to microwave system depends on the noise factor of pre-amplifier substantially, and therefore the quality of microwave low-noise amplifier noise factor directly can affect the quality of whole performance of receiving system.

The utility model realizes like this, construct a kind of single-stage low noise amplifier, it is characterized in that: comprise, input high pass impedance matching network, output high pass impedance matching network, input high pass impedance matching network selects band resistance to add varactor high pass filter structure, wherein, input high pass impedance matching network and export high pass impedance matching network and be π type matching network; Input high pass impedance matching network includes to be connected the capacitor combination part formed by variable capacitance diode; Also comprise by 1R99 1R100 1C165 1R104 for grid provide biasing circuit, by 1R94 1L151 1L53 1C163 for drain electrode biasing circuit is provided, described output high pass impedance matching network comprises output stage band pass filter.

The utility model has the advantage of: single-stage low noise amplifier described in the utility model, this product main feature: modularization, miniaturization, low noise, gain is high, Out-of-band rejection performance is good, low-power consumption, operating voltage is low, reliability is high, the temperature range that conforms wide (-30---+60 DEG C).This project is succeeded in developing, for solid foundation has been established in the development of application electric technology, radiotechnics, communication technology specialty, the cultivation of the RF/Microwave aspect talent, Students ' Professional skills training, university student's Skill Competition, Course Exercise, graduation project, simultaneously for the design of follow-up development multi-level radio-frequency/integrated and micro-bandization of microwave low-noise amplifier microwave provides deposit on the talent and technical support.

Accompanying drawing explanation

Fig. 1 receiver radio frequency front end schematic diagram

Fig. 2 is amplifying circuit block diagram

Fig. 3 is amplifier circuit figure

Wherein: input high pass impedance matching network 1, by variable capacitance diode connect is formed capacitor combination part 2, by 1R99 1R100 1C165 1R104 for grid provide biasing circuit 3, by 1R94 1L151 1L53 1C163 provide biasing circuit 4, output high pass impedance matching network 5, output stage band pass filter 6 for draining.

Embodiment

Below in conjunction with accompanying drawing 1-

3 pairs of the utility model are described in detail, and are clearly and completely described the technical scheme in the utility model embodiment, and obviously, described embodiment is only the utility model part embodiment, instead of whole embodiments.Based on the embodiment in the utility model, those of ordinary skill in the art are not making the every other embodiment obtained under creative work prerequisite, all belong to the scope of the utility model protection.

The utility model provides a kind of single-stage low noise amplifier at this, comprise, input high pass impedance matching network 1, output high pass impedance matching network 5, input high pass impedance matching network 1 selects band resistance to add varactor high pass filter structure, wherein, input high pass impedance matching network 1 and export high pass impedance matching network 5 and be π type matching network; Input high pass impedance matching network 1 includes to be connected the capacitor combination part 2 formed by variable capacitance diode; Also comprise by 1R99 1R100 1C165 1R104 for grid provide biasing circuit 3, by 1R94 1L151 1L53 1C163 for drain electrode biasing circuit 4 is provided, described output high pass impedance matching network (5) comprises output stage band pass filter 6.

As shown in Figure 3, input high pass impedance matching network, for π type matching network, band resistance is selected to add varactor high pass filter structure, object is to obtain steeper bandpass characteristics, larger Out-of-band rejection, thus improves antijamming capability, to reduce voltage fluctuation, bandpass characteristics is affected, suppress image frequency interference.The combination of the different electric capacity of connecting with variable capacitance diode at different levels can be finely tuned and is with logical shape.1R99 1R100 1C165 1R104 provide biased, 1C165 low frequency decoupling capacitor for grid.Electric capacity 1C120,1C178 in coupling play the effect of capacitance.1R94 1L151 1L53 1C163 for leak provide extremely biased, 1C163 low frequency decoupling capacitor.Exporting high pass impedance matching network, is π type matching network.Effectively return loss be can reduce, gain and stability improved.Output stage band pass filter increase one-level is the degree of suppression of leading to the right in order to increase band to the series resonance band pass filter on ground.

The leading indicator of product

Detailed schematic explanation is carried out to amplifier described in the utility model below:

1. low noise amplifier general introduction: the theory diagram shown in Fig. 1 being RF/Microwave receiver front end.As seen from Figure 1, the Main Function of low noise amplifier is the small-signal that amplifying antenna receives from air interface, reduces noise jamming, recalls required information data for For Solutions of Systems, so the design of low noise amplifier is vital concerning whole receiver.

Low noise amplifier forms: be made up of the part such as amplifying device (microwave transistor or microwave FET), input matching network, output matching network.

2. the scheme that circuit design is total

This project low noise amplifier Amplifier Design block diagram as shown in Figure 2, totally comprises three parts, microwave amplifier tube, input matching network, output matching network.

For above block diagram, the total design major design of circuit comprises: the design of the choosing of amplifier pipe, input and output matching circuit.First, the design principle of input matching circuit is: under the prerequisite preferentially meeting minimal noise, improves circuit gain.Namely according to the gain circle such as input with etc. noise circle choose.Secondly, the basic task of output matching circuit is that the output impedance of microwave tube plural number is matched load real number impedance 50 Ω.Output matching circuit object improves gain.Moreover Amplifier Design must make designed amplifier be stable, namely demand fulfillment stability condition (K > 1).Finally, while meeting index, emphasis considers technique and structural realizability.Technique should be selected loss is little, to be easy to processing, stable in properties, the physics (thickness) of material and electric property (dielectric constant) even, surface smoothness reaches necessarily required printed board simultaneously.For baseplate material aspect RF-

4 (between dielectric constants 4 ~ 5) and aluminium oxide ceramics are conventional microwave base plates.The impact considering contiguous interlock circuit is also needed when PCB fabric swatch.In addition EMC Design principle in filtering, ground connection and external circuit design should be noted.

3. the calculating of design parameter

(1) selection principle of low noise amplification pipe

High-gain and low noise and enough dynamic ranges to the major requirement of low noise amplification pipe, the operating frequency of current ambipolar low-noise tube can reach a few gigabit, noise factor is several decibel, and the operating frequency of the field effect transistor of GaAs small-signal is higher, noise factor can below 1 decibel.Choose low noise amplification organ pipe usually from two in consider: on the one hand the enough little working frequency range of noise factor of Microwave Low-Noise pipe is enough high, the f of transistor _tgenerally high than operating frequency more than 4 times.Microwave Low-Noise pipe will have sufficiently high gain and high dynamic range on the other hand, and the gain of General Requirements amplifier operation is greater than more than 10dB,

The intermodulation product caused by amplifier nonlinearity when input signal reaches system maximum is less than system noise floor.According to the requirement of technical indicator, comprehensive above two aspect factors we have chosen 3SK318YB field effect transistor, the feature of this pipe:

Low noise feature, maximum 2.2dB, representative value is 1.4dB;

Outstanding cross modulation characteristic;

Power gain is minimum is 18dB, and representative value is 21dB;

Low-power consumption, low voltage operating ability;

OIP3 is about 30dBm.

According to designed circuit engineering index request, select microwave FET 3SK318YB.This pipe is as follows in the S parameter of 400MHz:

S ₁₁＝0.972∠–24.1 S ₂₁＝2.28∠147.6

S ₁₂＝0.00533∠78.0 S ₂₂＝0.980∠-17.4

(2) judgement of amplifier stability: in low noise amplifier design, have a major issue, that is exactly amplifier stability.Stable factor K utilizes field effect transistor S parameter to give the direct instruction of stability, and is determined by following formula:

$K=\frac{1-{\left|S_{11}\right|}^2-{\left|S\right|}^2+{\left|\mathrm{\Δ}\right|}^2}{2\left|S_{12}{S}_{21}\right|}---\left(3\right)$

Wherein: Δ=S ₁₁s ₂₂-S ₁₂s ₂₁

If 1. K > 1, then transistor unconditional stability;

If 2. K < 1, then the stability of transistor depends on the position of source and the relatively stable circle of load impedance.

S parameter is substituted into formula above, can be calculated K ≈ 1.45>1, (K is now result when not mating) is so amplifier is stable.

Amplifier is made to avoid potential instability zone when actual design in order to ensure that low noise amplifier steady operation is also noted that.Simultaneously

For improving the self stability of microwave tube in engineering design, during design, consider following two kinds of modes:

1. be connected in series impedance negative feedback: between the source electrode and ground of 3SK318YB, be connected in series an impedance component resistance and electric capacity, thus form negative-feedback circuit.

2. stabilising decay device

: be connected to two-stage Π type resistive attenuator at the delivery outlet of 3SK318YB, and Π type resistive attenuator is a kind of measure of improvement amplifier stability of simple and feasible.In many situations, amplifier delivery outlet potential instability zone is comparatively large, adds Π type resistive attenuator at output, quite effective to improving stability.

(3) amplifier gain calculates: suppose S ₁₂=0 carries out simple gain calculating.

$G_{\mathrm{TUMAX}}=G_{1\mathrm{UMAX}}{G}_0{G}_{2\mathrm{UMAX}}=\frac{1}{(1-{\left|S_{11}\right|}^2)}{\left|S_{21}\right|}^2\frac{1}{(1-{\left|S_{22}\right|}^2)}$

In 50 Ω system transfers gains be:

G _0dB＝10lg(S ₂₁ ²)＝10lg(2.28) ²＝7.16dB

By coupling, the available maximum gain of input/output port is:

$G_{1\mathrm{UMAX}}=10\lg \left[\frac{1}{(1-{\left|S_{11}\right|}^2)}\right]=10\lg \left[\frac{1}{(1-{\left|0.972\right|}^2)}\right]=12.58\mathrm{dB}$

$G_{2\mathrm{UMAX}}=10\lg \left[\frac{1}{(1-{\left|S_{22}\right|}^2)}\right]=10\lg \left[\frac{1}{(1-{\left|0.980\right|}^2)}\right]=0.175\mathrm{dB}$

Therefore, maximum gain is:

G _TUMAX＝G _1UMAX+G _0dB+G _2UMAX＝(7.16+12.58+0.175)＝19.915dB

From theory calculate, maximum gain reaches 19.915dB, and meeting single-stage technical indicator is completely 13dB requirement.

(4) impedance transformer network matched design: the object realizing impedance matching has two: to be reflected wave between erasure signal source (or power supply) and load, and ensure the transmission quality of signal transmission, this impedance matching is called that areflexia is mated; Two is make power supply (or signal source) Maximum Power Output, and this impedance matching is called that peak power output is mated.

The source impedance that the gain that transistor provides depends on input consumingly, output port loads and load impedance.Due to inverter transfer coefficient S ₁₂existence, mean load reflection coefficient Γ _lcan affect the input impedance of transistor, input reflection coefficient is expressed as:

${\mathrm{\&Gamma;}}_{\mathrm{in}}=S_{11}+\frac{S_{21}{S}_{12}{\mathrm{\&Gamma;}}_L}{1-S_{22}{\mathrm{\&Gamma;}}_L}$

According to source reflection coefficient Γ _s, output reflection coefficient is expressed as:

${\mathrm{\&Gamma;}}_{\mathrm{out}}=S_{22}+\frac{S_{21}{S}_{12}{\mathrm{\&Gamma;}}_s}{1-S_{11}{\mathrm{\&Gamma;}}_s}$

Therefore, consider the impact that amplifier tube feeds back, adopt biconjugate matching method to mate, namely establish clocking requirement Γ _inwith Γ _outmeet simultaneously, can accomplish that signal source and load reflection coefficient mate so simultaneously, guarantee have high power gain and power gain flatness, take into account input and output standing-wave ratio simultaneously, radio circuit carries out match and regulate on the whole again.From actual production angle, input and output all will match 50 Europe, and the requirement that so not only can meet index also can reduce design size.

(5) noise factor NF

Noise figure of amplifier generally represents with NF, and it is used to the noiseproof feature weighing the system of making an uproar.Be defined as: amplifier input power signal-to-noise ratio (SNR) _i=S _in _iwith output power signal-to-noise ratio (SNR) ₀=S ₀n ₀ratio:

$F=\frac{{\left(\mathrm{SNR}\right)}_i}{{\left(\mathrm{SNR}\right)}_0}=\frac{S/N_i}{S/N_0}$

In engineering design with utilization, noise factor generally represents with decibel.Expression formula is as follows:

NF＝10lgF(dB)

For single-stage low noise amplifier, its noise factor is:

$\mathrm{NF}={\mathrm{NF}}_{\min }+{4R}_n\frac{{|{\mathrm{\&Gamma;}}_s-{\mathrm{\&Gamma;}}_{\mathrm{opt}}|}^2}{(1-{\left|{\mathrm{\&Gamma;}}_s\right|}^2){|1-{\mathrm{\&Gamma;}}_{\mathrm{opt}}|}^2}$

Wherein NF _minfor transistor Minimum noises coefficients, determined by the pipe of amplifier, Γ _out, R _nand Γ _sbe respectively and obtain F _mintime the source reflection coefficient of best reflection coefficient, transistor equivalent noise resistance and transistor input.Noise factor≤4.5db. is drawn by calculating this circuit design, by network analyzer test

(6) standing-wave ratio of input and output

The input and output standing-wave ratio of low noise amplifier characterizes the match condition in its input and output loop, we are when the match circuit of Design Low Noise Amplifier, input matching network is generally and obtains minimal noise and be designed to close to optimum noise matching network instead of best power matching network, and output matching network is generally design for obtaining maximum power and minimum standing-wave ratio, so always there is certain mismatch in the input of low noise amplifier.This mismatch can make system unstable in some cases, and generally, in order to reduce the impact of the port reflects caused by amplifier in mismatch on system, other measures such as the isolator that available Insertion Loss is very little solve.By showing that standing-wave ratio is 1.1 to the calculating of this circuit design and test.

(7) reflection coefficient

From theory analysis above: as Γ s=Γ opt, the noise factor of amplifier is minimum, NF=NFmin, but now from the angle of power delivery, input is mismatch, so the power gain of amplifier can reduce, but sometimes in order to obtain minimal noise, some gains of suitable sacrifice are also a kind of ways often adopted in low noise amplifier design.

(8) dynamic range (IIP3) of amplifier

In the design of low noise amplifier, the dynamic range of whole receiver should be taken into full account, in order to avoid cause serious nonlinear distortion in receiver rear class, the input third order intermodulation point IIP3 of low noise amplifier generally should be selected higher, the design is than maximum input signal height 30dB, in order to avoid generation nonlinear distortion during large-signal input.

(9) bandwidth of operation

Frequency is: 398 –

435MHz, is ensured by circuit design, and meets or exceeds this index completely by test.(10) gain flatness

Gain flatness refers to the fluctuating of working band internal power gain, and the difference of conventional highest-gain and least gain, namely △ G (dB) represents.From the test of circuit design result, gain flatness is≤0.6.

Electric power bias circuit: when forming amplifying circuit by field effect transistor, also will set up suitable quiescent point Q, and field effect transistor is voltage control device, therefore needs suitable grid source bias voltage.Direct current biasing determines the quiescent point of field effect transistor, thus also just determines the various performances of amplifier.But these performance parameters usually conflicting, restrict each other.Therefore, when considering direct current biasing point, usually will at various specific indexes, as made compromise selection between gain, the linearity, noise factor and power consumption etc.Although big current can improve the linearity and gain, also bring the increase of noise factor, therefore circuit design adopts biasing circuit of divided voltage simultaneously.Biasing circuit is simple and practical, and provides the negative feedback of right quantity for compensating the change due to DC current gain β in the discreteness of device and whole wide temperature (-40 DEG C ~+85 DEG C) working range.Its feedback principle is: if variations in temperature or device discreteness make DC current gain β change and cause device current to increase, then resistance R3 pressure drop can increase, and such base voltage VB can reduce, thus device current reduces, because herein is provided direct current negative feedback, the quiescent point of device is stablized.

5. board design: the RF/Microwave Integrated Circuits plate design phase will carry out carefully analyzing, careful planning, and the progress of each design procedure is carried out to the assessment that comprehensively continues.RF board design, as electromagnetic interference (EMI) problem, is the part of the most difficult control of engineers always, or even nightmare.Once just design successfully if want, must careful planning in advance and paying attention to detail just can prove effective.Radio frequency (RF) board design is a lot of uncertain owing to also having in theory, is therefore often described as a kind of " black art ".But this is a kind of partially to cover full viewpoint, and RF board design still has many rules that can follow.But, when actual design, real practical skill is when these rules cannot be implemented because of various restriction, how to carry out compromise to them.Important RF designs problem and comprises: impedance and impedance matching, insulating layer material and plywood, wavelength and harmonic wave etc., for this project, we take following several respects technology to board design.Micro-via hole: on circuit board, circuit of different nature must be separated, but connect under the optimal cases not producing electromagnetic interference again, and this just needs to use micro-via hole.Usual micro-via diameter is 0.05mm to 0.20mm.(2) subregion skill is adopted: when this board design, should as far as possible high power RF amplifier (HPA) and low noise amplifier (LNA) be kept apart.Briefly, allow high power RF radiating circuit away from low power RF receiving circuit exactly.Specific practice can be divided into entity subregion and electrical partitioning.

1. entity subregion mainly considers the problems such as spare part layout, orientation and shielding.

2. power distribution, RF cabling, sensitive circuit and the subregion such as signal, ground connection are mainly considered in electrical partitioning.

(3) metallic shield: in order to prevent some interference signals in outside or circuit own, this circuit is just considered when designing to adopt metallic shield radio-frequency (RF) energy to be shielded in RF region.Metallic shield must be welded on ground plane, and must keep a suitable distance with spare part, and the digital signal line entering metallic shield should walk internal layer as far as possible, and during bamboo product, lower one deck of signal line layer is set to ground plane.RF holding wire can be gone out from the wiring layer cabling of the small gap bottom metallic shield and ground connection indentation, there, but will be surrounded by vast contact area as far as possible around indentation, there, and the ground connection on unlike signal layer can connect together by multiple via hole.Metallic shield is usually the unique solution of isolation Key Circuit.

(4) power source deoupling circuit: power source deoupling circuit is also extremely important.Many RF chips incorporating linear circuit are very responsive to the noise of power supply.RF decoupling is then jointly completed (see basic circuit diagram) by inductance 1L7 and electric capacity 1C15,1C19, and it makes RF signal cannot be coupled to chip from power line.Because all cablings are all that potential both can a reception also can the antenna of transmitting RF signal, so it is necessary for radiofrequency signal and critical circuits, spare part being isolated.Especially it is significant to note that: inductance is seldom parallel to be close together, because this is by formation air-core transformer, and mutual induction produces interference signal, the distance therefore between them at least will be equivalent to one of them height, or arrangement at a right angle reduces to minimum to make its mutual inductance.

(5) ground connection: the ground connection guaranteeing RF cabling lower floor is solid, and all spare parts all will be connected on main ground connection securely, and the cabling of noise may be brought to keep apart with other.In PCB design, public analogue ground and for shield and to separate the ground connection of holding wire normally of equal importance.Therefore should be ground connection copper sheet as far as possible around all RF cabling, pad and assembly, and be connected with main ground connection as far as possible.Miniature via hole structure plate is very useful in the RF circuit development phase, and it needn't spend any expense just can arbitrarily use a lot of via hole, otherwise boring will increase development cost on common pcb board, and this is uneconomic when large quantities of volume production.When a solid monoblock ground plane being placed directly in the lower ground floor in surface, isolation effect is best.Printed circuit board (PCB) by the analysis of amplifier and optimal design, by the circuit production that finally obtains on FR4 (ε r=4.5, h=0.8mm) substrate.By simulation software, Electromagnetic Simulation is carried out to amplifier PCB simultaneously, finally result is entered

Row treatment and analysis.

The single-stage LNA of low cost, low-power consumption, low noise, high-gain and High Linear is achieved by design above.

Seen the following form by network analyzer test result.

Product test result leading indicator

Therefore, design objective requirement is reached.

To the above-mentioned explanation of the disclosed embodiments, professional and technical personnel in the field are realized or uses the utility model.To be apparent for those skilled in the art to the multiple amendment of these embodiments, General Principle as defined herein when not departing from spirit or scope of the present utility model, can realize in other embodiments.Therefore, the utility model can not be restricted to these embodiments shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.

Claims (1)

1. a single-stage low noise amplifier, it is characterized in that: comprise, input high pass impedance matching network (1), output high pass impedance matching network (5), input high pass impedance matching network (1) selects band resistance to add varactor high pass filter structure, wherein, input high pass impedance matching network (1) and export high pass impedance matching network (5) and be π type matching network; Input high pass impedance matching network (1) includes to be connected the capacitor combination part (2) formed by variable capacitance diode; Gate bias circuit (3) is made up of resistance 1R99, resistance 1R100, electric capacity 1C165, resistance 1R104; Drain bias circuit (4) is made up of resistance 1R94, inductance 1L151, inductance 1L53, electric capacity 1C163; Described output high pass impedance matching network (5) comprises output stage band pass filter (6).