CN105811888A - Radio frequency power amplifier output match circuit structure and designing method thereof - Google Patents

Abstract

The invention discloses a radio frequency power amplifier output match circuit structure and a designing method thereof. The structure comprises a power amplifier tube, a choke inductor, a power amplifier tube output end capacitor, a secondary harmonic network and a broadband matching network. The secondary harmonic network is a secondary end network. The broadband matching network comprises a band-pass matching network composed of the inductor and the capacitor, and a blocking capacitor. The invention further provides the circuit parameter designing method of the radio frequency power amplifier output match circuit structure. The output end capacitor of the power amplifier tube, the secondary harmonic network and the broadband matching network are utilized for achieving impedance conversion, the inhibiting effect on secondary harmonics is enhanced, and three-time harmonics are well utilized; accordingly, the output voltage waves of a power amplifier are closer to square waves in shape, output currents are closer to semi waves, the overlapped part of the voltage wave shape and the current wave shape is small, the overall efficiency and the linearity of the power amplifier are improved greatly, and harmonic distortion of the output level of the radio frequency power amplifier is effectively reduced.

Description

A kind of radio-frequency power amplifier output matching circuit structure and method for designing thereof

Technical field

The present invention relates to a kind of radio-frequency power amplifier output matching circuit.

Background technology

At present, the whole world is applied to the portability such as smart mobile phone and moves the mobile network of equipment and develop rapidly and expand, and multifunction intelligent mobile telephone application is further extensive.In order to provide the big data of high data rate to transmit, Modern Communication System (3G/4G) have employed the modulation system of more complicated spectral efficient, such as the modulation system that the phase-shift keying (PSK)s such as QPSK and AQM and amplitude shift keying combine, this modulation system requires that power amplifier has the strict linearity, and the conflict index that the index linearity and efficiency are Designing power amplifier, high linearity means relatively low power efficiency.

For meeting the user demand of different user, smart mobile phone generally all supports two or more network formats, and along with the working form of mobile phone is different, its effective frequency bandwidth is different, it is therefore desirable to the output matching circuit of radio-frequency power amplifier has broadband impedance transfer capability.

Additionally, in order to ensure that the power amplifier working in certain special frequency channel does not disturb successive bands signal, the output spectrum of power amplifier must meet corresponding ACLR requirement.Such as, the E_UTRA_ACLR being applied to the power amplifier of LTE is-33dBc.

Along with functional module and the Modern Communication System modulation system of portable equipment become increasingly complex, it is desirable to be applied to the power amplifier of a new generation's communication system, it is necessary to have higher power efficiency and the linearity, and have wider bandwidth of operation.

In Chinese patent 201210041407.X, by adopting the output matching circuit of lowpass structures suppress harmonic wave and improve the efficiency of power amplifier.But this structure is not suitable for the application of broadband aspect, and efficiency raising degree is inconspicuous.

Additionally, in China CN201510057384.5, by adopting the combination of second harmonic network, triple-frequency harmonics network and broadband matching network to reach stronger harmonics restraint effect, but this method utilizes triple-frequency harmonics preferably so that efficiency declines to some extent.

Summary of the invention

In efficiency and the harmonics restraint processing method of the broadband matching circuit of the radio-frequency power amplifier reported, it is impossible to realize preferably compromising between bandwidth, efficiency and the linearity, and do not account for the impact on match circuit of the transistor output capacitance.

It is an object of the invention to overcome weak point of the prior art, it is provided that a kind of broadband and high efficiency radio-frequency power amplifier output matching circuit structure, it is achieved through the following technical solutions:

A kind of radio-frequency power amplifier output matching circuit structure, this output matching circuit includes power amplifier tube 101, choke induction 102, power amplifier tube output capacitor 103, second harmonic network 104 and broadband matching network 107；

Second harmonic network 104 is connected to the singly-terminal pair being composed in series by inductance 105 and electric capacity 106 of the drain electrode of power amplifier tube 101 (colelctor electrode) other end ground connection for one end；

Broadband matching network 107 includes by inductance 112, inductance 110, the bandpass matching network of electric capacity 109 and electric capacity 108 composition, and capacitance 111；

Inductance 112 one end is connected to the drain electrode (colelctor electrode) of power amplifier tube 101；

One end of electric capacity 109 is connected to the other end of inductance 112 and the junction of electric capacity 108, other end ground connection；

One end of inductance 110 is connected to the other end of electric capacity 108 and the junction of capacitance 111, other end ground connection；

The other end of capacitance 111 connects with load.

Further, broadband matching network 107 can adopt two-stage low pass LC structure, and namely electric capacity 108 and inductance 110 position are exchanged, as shown in Figure 5.

Further, broadband matching network 107 can adopt two-stage high-pass LC structure, and namely inductance 112 and electric capacity 109 position are exchanged, as shown in Figure 6.

The present invention also provides for a kind of circuit parameter design method of described radio-frequency power amplifier output matching circuit structure, and it comprises the following steps:

Step a: determine the resistance value of load RL, the operating frequency of described radio-frequency power amplifier, makes power amplifier tube 101 export the resistance value of optimum impedance Ropt of maximum voltage and current swing and the inductance value of choke induction 102 simultaneously.Voltage swing when the output maximum voltage of power amplifier tube and current swing refer to can be output by peak power in current bias situation and current swing.

Step b: as it is shown on figure 3, Fig. 3 is the Fig. 2 equivalent circuit diagram at first-harmonic place.Determining the parameter of element inside broadband matching network 107, and convert the resistance value of load RL to admittance Y=Gopt-jBx through broadband matching network 107, the value then passing through admittance Y calculates the value of equivalent capacity Ceff.

Step c: as shown in Figure 4, Fig. 4 are Fig. 2 equivalent circuit diagram under triple-frequency harmonics.Broadband matching network 107 is equivalent to inductance Lin the value according to choke induction 102 and equivalent capacity Ceff, calculates described equivalent inductance Lin and the component parameters of second harmonic network 104 and the parameter of the output capacitor 103 of power amplifier tube 101；Output capacitor 103 is composed in parallel by power amplifier tube 101 output capacitance Cout and on-chip capacitance Cdie, and is connected in parallel between drain electrode and the source electrode of power amplifier tube 101, calculates the parameter of described on-chip capacitance Cdie according to the parameter of output capacitor 103.

Further, in described step a, choke induction 102 obtaining value method is the AC impedance n times of optimum impedance Ropt making choke induction 102 at the operating frequencies, and wherein n is any nonnegative number.

Further, described step b particularly as follows:

Bandwidth of operation according to power amplifier tube 101 determines the quality factor q of broadband matching network 107, and then calculating determines that interim transfer resistance RT, RT are tried to achieve by following formula:

$Q=\sqrt{\sqrt{\frac{RL}{RT}}-1}$

Calculate equal resistance per square RI, RI according to described quality factor q and interim transfer resistance RT to be tried to achieve by following formula:

$RI=\sqrt{RL\·RT}$

Calculating the parameter of element inside broadband matching network 107 respectively according to described quality factor q and equal resistance per square RI is:

$L_1=\frac{RL}{{\mathrm{Q\ω}}_0}$

$C_1=\frac{1+Q^2}{{{\mathrm{\ω}}_0}^2{L}_1{Q}^2}$

$C_2=\frac{Q}{{\mathrm{\ω}}_{0}RI}$

$L_2=(\sqrt{\frac{RIS}{Gx}-{\mathrm{RIS}}^2}+\frac{1}{{\mathrm{\ω}}_0{C}_{2eq}})/{\mathrm{\ω}}_0$

Wherein L₁Namely inductance 110, L₂Namely inductance 107, C₁I.e. electric capacity 108, C2 and electric capacity 109；

$RIS=\frac{RI}{1+Q^2}$

$Gx=\frac{1}{Ropt}$

$C_{2ep}=C_2\·\frac{1+Q^2}{Q^2}$

Calculating equivalent capacity Ceff according to the parameter of element inside broadband matching network 107 is:

$Ceff=\frac{{\mathrm{\ω}}_0{L}_2-1/\left({\mathrm{\ω}}_0{C}_{2ep}\right)}{{\mathrm{\ω}}_0({\mathrm{RIS}}^2+{({\mathrm{\ω}}_0{L}_2-1/({\mathrm{\ω}}_0{C}_{2eq}\left)\right)}^2)}$

Wherein, ω₀Angular frequency for corresponding operating frequency.

Further, described step c particularly as follows:

The computational methods of the broadband matching network 107 equivalent inductance Lin under triple-frequency harmonics are:

$Lin=imag\left(\right(RL//\left({\mathrm{j\ω}}_3{L}_1\right)+\frac{1}{{\mathrm{j\ω}}_3{C}_1})//\frac{1}{{\mathrm{j\ω}}_3{C}_2}+{\mathrm{j\ω}}_3{L}_2)/{\mathrm{\ω}}_3$

Wherein, ω₃=3 ω₀

The component parameters computational methods of second harmonic network 104 are:

$Ls2=\frac{8}{3}\·\frac{Lcin}{Ceff\·5{{\mathrm{\ω}}_0}^{2}Lcin-5/9}$

$Cs2=\frac{1}{4{{\mathrm{\ω}}_0}^{2}Ls2}$

Wherein, Lcin=Lin//Lc, Ls2 and inductance 105, Cs2 and electric capacity 106, Lc and choke induction 102；

The output capacitor Cc of power amplifier tube 101, namely the capacitance of electric capacity 103 is expressed as:

$Cc=Ceff-\frac{1}{3{{\mathrm{\ω}}_0}^{2}Ls2}$

The relatively size of output capacitor Cc and the output capacitance Cout of power amplifier tube 101, if output capacitor Cc is relatively big, then the parameter of on-chip capacitance Cdie is:

Cdie=Cc-Cout

Otherwise return step a, reselect matching network quality factor q, then recalculate.

Beneficial effects of the present invention: the present invention is by utilizing the output capacitance of power amplifier tube, second harmonic network and broadband matching network to realize impedance transformation, and this matching network realizes under second harmonic in short-circuit condition, enhances the inhibition to second harmonic；And be open-circuit condition at triple-frequency harmonics, utilize triple-frequency harmonics preferably；So that the output voltage waveforms of power amplifier is closer to square wave, output electric current is closer to half-wave, therefore voltage waveform is less with current waveform lap, thus substantially increasing the whole efficiency of power amplifier；By adopting second harmonic and the broadband matching network with filtering characteristic, second harmonic is carried out inhibitory action preferably, and has improve the linearity of power amplifier.The present invention significantly reduces the harmonic distortion of radio-frequency power amplifier output stage, improves the power efficiency of power amplifier.

Accompanying drawing explanation

Fig. 1 is the circuit theory diagrams of the present invention.

Fig. 2 is the match circuit figure looked over toward load direction from Fig. 1 transistor output.

Fig. 3 is the Fig. 2 equivalent circuit diagram at first-harmonic place.

Fig. 4 is Fig. 2 equivalent circuit diagram under triple-frequency harmonics.

The circuit diagram of the two-stage low pass LC structure that Fig. 5 is the electric capacity 108 of Fig. 1 and inductance 110 position is exchanged.

The circuit diagram of the two-stage high-pass LC structure that Fig. 6 is the inductance 112 of Fig. 1 and electric capacity 109 position is exchanged.

Detailed description of the invention

Embodiment 1, as shown in Figures 1 to 4, a kind of radio-frequency power amplifier output matching circuit structure, this output matching circuit includes power amplifier tube 101, choke induction 102, power amplifier tube output capacitor 103, second harmonic network 104 and broadband matching network 107；Second harmonic network 104 is connected to the singly-terminal pair being composed in series by inductance 105 and electric capacity 106 of the drain electrode of power amplifier tube 101 (colelctor electrode) other end ground connection for one end；Broadband matching network 107 includes by inductance 112, inductance 110, the bandpass matching network of electric capacity 109 and electric capacity 108 composition, and capacitance 111；Inductance 112 one end is connected to the drain electrode (colelctor electrode) of power amplifier tube 101；One end of electric capacity 109 is connected to the other end of inductance 112 and the junction of electric capacity 108, other end ground connection；One end of inductance 110 is connected to the other end of electric capacity 108 and the junction of capacitance 111, other end ground connection；The other end of capacitance 111 connects with load.

Embodiment 2, as it is shown in figure 5, compared with embodiment 1, broadband matching network 107 adopts two-stage low pass LC structure, exchanges by electric capacity 108 and inductance 110 position of embodiment 1.

Embodiment 3, as shown in Figure 6, compared with embodiment 1, broadband matching network 107 adopts two-stage high-pass LC structure, exchanges by inductance 112 and electric capacity 109 position of embodiment 1.

Claims (7)

1. a radio-frequency power amplifier output matching circuit structure, it is characterized in that: this output matching circuit includes power amplifier tube (101), choke induction (102), power amplifier tube output capacitor (103), second harmonic network (104) and broadband matching network (107)；

Second harmonic network (104) is connected to the singly-terminal pair being composed in series by inductance (105) and electric capacity (106) of the drain electrode other end ground connection of power amplifier tube (101) for one end；

Broadband matching network (107) includes the bandpass matching network being made up of inductance (112), inductance (110), electric capacity (109) and electric capacity (108) and capacitance (111)；

Inductance (112) one end is connected to the drain electrode of power amplifier tube (101)；

One end of electric capacity (109) is connected to the other end of inductance (112) and the junction of electric capacity (108), other end ground connection；

One end of inductance (110) is connected to the other end of electric capacity (108) and the junction of capacitance (111), other end ground connection；

The other end of capacitance (111) connects with load.

2. radio-frequency power amplifier output matching circuit structure according to claim 1, it is characterised in that: electric capacity (108) and inductance (110) position are exchanged.

3. radio-frequency power amplifier output matching circuit structure according to claim 1, it is characterised in that: inductance (112) and electric capacity (109) position are exchanged.

4. the circuit parameter design method of radio-frequency power amplifier output matching circuit structure according to claim 1, it is characterised in that: the method comprises the following steps:

Step a: determine the resistance value of load RL, the operating frequency of described radio-frequency power amplifier, can export the resistance value of the optimum impedance Ropt of maximum voltage and current swing and the inductance value of choke induction (102) while of making power amplifier tube (101) in current bias situation；

Step b: determine the parameter of broadband matching network (107) the inside element, and convert the resistance value of load RL to admittance Y=Gopt-jBx through broadband matching network (107), the value then passing through admittance Y calculates the value of equivalent capacity Ceff；

Step c: broadband matching network (107) is equivalent to inductance Lin, and the value according to described choke induction (102) and equivalent capacity Ceff, calculate described equivalent inductance Lin and the component parameters of second harmonic network (104) and the parameter of the output capacitor (103) of power amplifier tube (101)；Output capacitor (103) is composed in parallel by power amplifier tube (101) output capacitance Cout and on-chip capacitance Cdie, and it is connected in parallel between drain electrode and the source electrode of power amplifier tube (101), the parameter of described on-chip capacitance Cdie is calculated according to the parameter of described output capacitor (103).

5. the circuit parameter design method of radio-frequency power amplifier output matching circuit structure according to claim 4, it is characterized in that: in described step a, choke induction (102) obtaining value method is the AC impedance n times of optimum impedance Ropt making choke induction (102) at the operating frequencies, and wherein n is any nonnegative number.

6. the circuit parameter design method of radio-frequency power amplifier output matching circuit structure according to claim 5, it is characterised in that: described step b particularly as follows:

Bandwidth of operation according to power amplifier tube (101) determines the quality factor q of broadband matching network (107), and then calculating determines that interim transfer resistance RT, RT are tried to achieve by following formula:

$Q=\sqrt{\sqrt{\frac{RL}{RT}}-1}$

Calculate equal resistance per square RI, RI according to described quality factor q and interim transfer resistance RT to be tried to achieve by following formula:

$RI=\sqrt{RL\·RT}$

The parameter calculating broadband matching network (107) the inside element according to described quality factor q and equal resistance per square RI respectively is:

$L_1=\frac{RL}{{\mathrm{Q\ω}}_0}$

$C_1=\frac{1+Q^2}{{{\mathrm{\ω}}_0}^2{L}_1{Q}^2}$

$C_2=\frac{Q}{{\mathrm{\ω}}_{0}RI}$

$L_2=(\sqrt{\frac{RIS}{Gx}-{\mathrm{RIS}}^2}+\frac{1}{{\mathrm{\ω}}_0{C}_{2eq}})/{\mathrm{\ω}}_0$

Wherein L₁Namely inductance (110), L₂Namely inductance (107), C₁Namely electric capacity (108), C₂I.e. electric capacity (109)；

$RIS=\frac{RI}{1+Q^2}$

$Gx=\frac{1}{Ropt}$

$C_{2ep}=C_2\·\frac{1+Q^2}{Q^2}$

Parameter according to broadband matching network (107) the inside element calculates equivalent capacity Ceff and is:

$Ceff=\frac{{\mathrm{\ω}}_0{L}_2-1/\left({\mathrm{\ω}}_0{C}_{2ep}\right)}{{\mathrm{\ω}}_0({\mathrm{RIS}}^2+{({\mathrm{\ω}}_0{L}_2-1/({\mathrm{\ω}}_0{C}_{2eq}\left)\right)}^2)}$

Wherein, ω₀Angular frequency for corresponding operating frequency.

7. the circuit parameter design method of radio-frequency power amplifier output matching circuit structure according to claim 6, it is characterised in that: described step c particularly as follows:

The computational methods of the broadband matching network (107) equivalent inductance Lin under triple-frequency harmonics are:

$Lin=imag\left(\right(RL//\left({\mathrm{j\ω}}_3{L}_1\right)+\frac{1}{{\mathrm{j\ω}}_3{C}_1})//\frac{1}{{\mathrm{j\ω}}_3{C}_2}+{\mathrm{j\ω}}_3{L}_2)/{\mathrm{\ω}}_3$

Wherein, ω₃=3 ω₀

The component parameters computational methods of second harmonic network (104) are:

$Ls2=\frac{8}{3}\·\frac{Lcin}{Ceff\·5{{\mathrm{\ω}}_0}^{2}Lcin-5/9}$

$Cs2=\frac{1}{4{{\mathrm{\ω}}_0}^{2}Ls2}$

Wherein, Lcin=Lin//Lc, Ls2 and inductance (105), Cs2 and electric capacity (106), Lc and choke induction (102)；

The output capacitor Cc of power amplifier tube (101), namely the capacitance of electric capacity (103) is expressed as:

$Cc=Ceff-\frac{1}{3{{\mathrm{\ω}}_0}^{2}Ls2}$

The relatively size of output capacitor Cc and power amplifier tube (101) output capacitance Cout, if output capacitor Cc is relatively big, then the parameter of on-chip capacitance Cdie is:

Cdie=Cc-Cout

Otherwise return step a, reselect matching network quality factor q, then recalculate.