CN207491094U - Digital tv transmitter ultra wide band high efficiency power amplifier - Google Patents

Abstract

The utility model is related to digital TV transmitter ultra wide band high efficiency power amplifiers, including pre-amplifier (1) and two power splitter of Wilkinson connected to it (2), two power splitter of Wilkinson (2) divides the signal into two-way, enter booster amplifier (3) all the way, another way first passes through one section of phase compensation line (4), after a damping resistance R5, into main amplifier (5)；Through overmatching network 1 (61) after the amplification of main amplifier (5) signal, through overmatching network 2 (62) and compensation network (7) after the amplification of booster amplifier (3) signal, after two signal combinings, by 2 quadravalence impedance transformers (8), then it is exported by a bit of microstrip line (9), with working band is wide, high efficiency, gain level are high, band standing internal wave than it is small, long-time high/low temperature job stability is high, the good performance of amplifier reliability, it is easy to use, it can be widely used for television transmitter power amplifier link.

Description

Digital TV transmitter ultra wide band high efficiency power amplifier

Technical field

The utility model is related to a kind of digital TV transmitter ultra wide band high efficiency power amplifiers.

Background technology

With the development of digital television modulation technology, requirement higher of the digital transmission signal to equipment, a higher peak Compare, second is that wider occupancy bandwidth.In recent years simultaneously, with the proposition of economizing type theory, digital television transmissions system is to hair Penetrate the power consumption of machine and bandwidth propose strict requirements, the efficiency power amplifier of traditional AB class balanced structures all than relatively low, Cause the very big wasting of resources.The technology that current industry improves efficiency of amplitude mainly has, envelope separation and recovery technology, envelope Tracking technique, LINC technologies, Doherty technologies.Doherty technologies wherein the utility model is related to arrive have efficient, realization The advantages of method is simple, at low cost, while DPD (digital pre-distortion) function of DVB-T Transmitter is coordinated to improve linearly, it can To meet the requirement of digital TV transmitter system well, but tradition Doherty structures by after carrier amplifier four/ The influence of one wavelength impedance transformers, bandwidth are restricted.

Utility model content

The technical problem to be solved by the utility model is to provide digital TV transmitter ultra wide band high efficiency power amplifier, with solution Defect certainly in the prior art.

The technical solution that the utility model solves above-mentioned technical problem is as follows：

Digital TV transmitter ultra wide band high efficiency power amplifier, pre-amplifier (1) and Wilkinson connected to it two Power splitter (2), two power splitter of Wilkinson (2) divide the signal into two-way, all the way into booster amplifier (3), another way One section of phase compensation line (4) is first passed through, after a damping resistance R5, into main amplifier (5)；Main amplifier (5) is believed Through overmatching network 1 (61) after number amplification, through overmatching network 2 (62) and compensation network after the amplification of booster amplifier (3) signal (7), it after two signal combinings, by 2 quadravalence impedance transformers (8), is then exported by a bit of microstrip line (9).

Further, the main amplifier (5) and booster amplifier (3) connect main feed electric network (51) and auxiliary feedback respectively Electric network (31), the main feed electric network (51) and auxiliary feeding network (31) use low-resistance line impedence to be hindered for Z3 and high resistant line Resist the broadband feed design circuit formed for Z4；

Further, main amplifier (5) is biased using grid voltage and temperature-compensation circuit (52) carries out temperature-compensating；

The beneficial effects of the utility model are：With working band is wide, high efficiency, gain level are high, band standing internal wave than it is small, Long-time high/low temperature job stability is high, the good performance of amplifier reliability, wherein more than 40% power amplification efficiency, full frequency band band Interior gain be more than 14dB, with interior frequency response for ± 0.5dB, standing-wave ratio be less than 1.4, amplifier provide single supply power supply, packaging body Product is small, easy to use, can be widely used for television transmitter power amplifier link.

Description of the drawings

Fig. 1 is the utility model principle schematic diagram；

Fig. 2 is two power divider circuit structure diagram of broadband second order Wilkinson；

Fig. 3 is biased for grid voltage and temperature-compensation circuit electrical block diagram；

Fig. 4 is main feeding-network circuits structure diagram；

Fig. 5 is auxiliary feeding-network circuits structure diagram；

Reference numeral is as follows：

1st, pre-amplifier, 2, two power splitter of Wilkinson, 3, booster amplifier, 4, phase compensation line, 5, main amplification Device, 61, matching network 1,62, matching network 2,7, compensation network, 8, quadravalence impedance transformer, 9, microstrip line.

Specific embodiment

The principle and feature of the utility model are described below in conjunction with attached drawing, example is served only for explaining this practicality It is novel, it is not intended to limit the scope of the utility model.

As shown in Figs. 1-5, after digital television signal first passes through preposition pre-amplification, input signal first passes through the Weir gold of second order Gloomy two power splitter is divided into two-way, and all the way into the booster amplifier of asymmetric IDPA, another way first passes through one section of impedance Z 0=50 Ω, length is the phase compensation line of 1/4 wavelength, after a damping resistance R5, into main amplifier；Main amplifier signal Successively pass through matching network (impedance through overmatching network (impedance Z3, length Lb), auxiliary amplifier signal amplification after amplification For Z4, length Lc) and compensation network (impedance Z5, length La), two signals are after the combining of peak points, by 2 four Rank impedance transformer is Z6-Z9 and Z10-Z13 respectively, is then exported by the microstrip line that a bit of impedance is Z0.Main amplifier Low-resistance line impedence is all used as broadband feed design electricity that Z3 and high resistant line impedence are Z4 compositions with booster amplifier feeding network Road, wherein main amplifier carry out the analog circuit of temperature compensated bias voltage using triode.

1/4 wavelength impedance transformers (Z5, La) are added in behind booster amplifier unlike the prior art, and master is put 1/4 wavelength line (Z0, La) before big device plays the role of phase compensation.

In small-signal, booster amplifier does not work, and only main amplifier works, such as Fig. 1, is put at this time from load to auxiliary The impedance Z b that big device looks over is approximate infinitely great, understands that Zc is approximately zero by 1/4 wavelength, is leaked into this way from main amplifier auxiliary The power for helping amplifier is just very small.The impedance Z a=25 Ω looked over from the output network of main amplifier, pass through matching in this way Network and compensating line are transformed to 2 times of Z0 in the drain output impedance of main amplifier, when the electric current of main amplifier reaches maximum Electric current half, main amplifier enter voltage saturation, and booster amplifier opens work, this is that efficiency reaches first peak value, output Power is the 1/4 of saturation power, i.e., the same with traditional Doherty amplifiers, and in back-off 6dB, efficiency is maximum.

When big signal, main and auxiliary amplifier is all in working condition, when output power reaches saturation, Za=Zb=Zc =50 Ω.At this time by matching network and compensating line, the drain electrode output impedance of main and auxiliary amplifier is Z0.It is auxiliary in IDPA structures 1/4 wavelength of amplifier out is helped not only to play a part of phase compensation, also reduces the effect of power leakage, and main amplification The output network (impedance Z 3, length Lb) of matching network and the compensating line composition of device, other than the effect of impedance matching to be realized, The effect of impedance transformation is also acted as, this is that IDPA structures are essentially different with traditional Doherty, so IDPA bands Width can be wider, more efficient.

Because the booster amplifier in Doherty amplifiers is operated in C classes, main amplifier is operated in AB classes, therefore for same The input signal of sample size, the output current of booster amplifier is certainly less than the output current of amplifier.This just brings load to lead The problem of drawing deficiency, so as to reduce the whole efficiency of Doherty amplifiers.And the peak-to-average force ratio of DTMB signals is also higher, is full Sufficient linear index requirement, the operating power of amplifier need more rollbacks, but traditional Doherty is to retract Efficiency highest when 6dB, in order to solve this defect, the design employs the Doherty amplifiers of unsymmetric structure, in master Increase attenuator R5 before amplifier, the circuit that this scheme is realized simply can be used preferably with IDPA respective outer side edges, be led to Cross adjustment R5 resistance value, can when rollback 7-8dB efficiency highest.

Meanwhile the impedance transformer network after combining is improved to multistage impedance transformation, is realized ultra-wide by 1/4 traditional wavelength Band performance, because total has 8 rank impedances transformation, if designed on same circuit board, otherwise 4 rank impedances below can be caused The microstrip line for becoming device is too thin, and the microstrip line for influencing 4 rank impedance transformer of high-power output or front is too thick, can make cloth board foot It is very little too big, so herein using 2 kinds of pcb board materials, before 4 rank impedance transformers impedance comparison it is small using than relatively thin plank, The impedance ratio of 4 rank impedance transformer next is larger to use thicker plank.

Two power splitter of broadband second order Wilkinson therein is introduced below, due to the bandwidth of full frequencies in digital TV section It is wider, it is necessary to could to meet index request using multistage Wilkinson structure, band can be met using second order structure by calculating Width requirement.According to correlation theory, by tabling look-up and correlation computations, the isolation resistance R1=1.96*Z0 of second order power splitter is obtained, R2=4.82*Z0 considers that engineering practice uses R1=100 Ω, R2=250 Ω here.And second order transformer section is distinguished For Z1=83.35 Ω and Z2=60 Ω, while in order to reduce overall dimensions, 1/4 wavelength impedance transformation Z1, Z2 is using serpentine Cabling mode, physical circuit model such as Fig. 2.

Feeding network：In Fig. 3 grid voltage biasing circuits, resistance R2 is one highly important parameter of amplifier, it It can be obtained with formula R2=400/P, P is the saturation output power of amplifier in formula.

It additionally needs and is pointed out that feed offset line is all with the microstrip line of λ/4, infinite-impedance is showed to match circuit, Biasing circuit is not involved in Circuit Matching.L1 is the microstrip line of big inductance or λ/4 in RF frequency, and C1, C2 are decoupling capacitor, and R1 is used To improve the stability of circuit.

LDMOS pipes are under certain grid voltage, when operating temperature is promoted, quiescent current Idq raisings, on the contrary it reduces.It is quiet The variation of state electric current can influence the gain of system, efficiency and the indexs such as linear, wherein again maximum with linear influence.Therefore, it needs It to give on the grid voltage circuit of main amplifier for being operated in AB classes and do grid voltage temperature-compensating plus triode.

Emitter junction forward voltage drop Vb has negative temperature coefficient, under magnification, is -2mV/ DEG C for silicone tube, utilizes This characteristic of emitter junction, the multiple circuit of Vb realize temperature-compensating, as shown in figure 3, when IR3 is increasing (during calculating Can use ten times of relationships),

Have for the circuit：Vd=(1+R3/R4) * Vb

When R3 is equal to 1.2K, and R4 is equal to 2.2K, the current potential of Vd is：

Vd=(1+1.2/2.2) * 0.66=1.02V

When 1 DEG C of temperature change, the variable quantity of Vd is：

=-3mV/ DEG C of Δ Vd=(1+R3/R4) * Δs Vb=(1+1.2/2.2) * (- 2mV/ DEG C)

It is approximately equal to the temperature varying coefficient of LDMOS pipes, during verification experimental verification R3=1.2K Ω, R4=2.2K Ω, can obtains Stable static working current, which is successfully used in actual circuit design, and has stable performance.

Through actual test, the amplifier have working band is wide, high efficiency, gain level are high, band standing internal wave than it is small, long when Between high/low temperature job stability is high, the good performance of amplifier reliability, wherein increase in more than 40% power amplification efficiency, full frequency band band Benefit is more than 14dB, be ± 0.5dB with interior frequency response, standing-wave ratio is less than 1.4, amplifier provides single supply power supply, encapsulation volume is small, It is easy to use, it can be widely used for television transmitter power amplifier link.

The above is only the preferred embodiment of the present invention, is not intended to limit the utility model, all in this practicality Within novel spirit and principle, any modification, equivalent replacement, improvement and so on should be included in the guarantor of the utility model Within the scope of shield.

Claims (3)

1. digital TV transmitter ultra wide band high efficiency power amplifier, it is characterised in that：Pre-amplifier (1) and prestige connected to it Bis- power splitters of Er Jinsen (2), two power splitter of Wilkinson (2) divides the signal into two-way, all the way into booster amplifier (3), another way first passes through one section of phase compensation line (4), after a damping resistance R5, into main amplifier (5)；Master is put Through overmatching network 1 (61) after big device (5) signal amplification, after the amplification of booster amplifier (3) signal through overmatching network 2 (62) and Compensation network (7), it is then defeated by a bit of microstrip line (9) by 2 quadravalence impedance transformers (8) after two signal combinings Go out.

2. digital TV transmitter ultra wide band high efficiency power amplifier according to claim 1, it is characterised in that：The main amplification Device (5) and booster amplifier (3) connect main feed electric network (51) and auxiliary feeding network (31), the main feed electric network respectively (51) and auxiliary feeding network (31) use low-resistance line impedence as broadband feed design that Z3 and high resistant line impedence are that Z4 is formed Circuit.

3. digital TV transmitter ultra wide band high efficiency power amplifier according to claim 2, it is characterised in that：Main amplifier (5) temperature-compensating is carried out using grid voltage biasing and temperature-compensation circuit (52).