CN101005672A - Power amplifier based on PHS communication terminal - Google Patents

Abstract

The invention uses HBT technical transistors connected in a chip in cascade connection; its capacity of anti-load pulling is enhanced by optimizing its output load impedance under 4:1 standing-wave ratio. The emission power of the PHS terminal is determined by the gain of antenna and the output power of the amplifier; when the gain of antenna is a constant value, the emission power of PHS terminal varies along with the variation of the output power.

Description

A kind of power amplifier that is used for the PHS communication terminal

Technical field

The present invention relates to PHS communication (personal handyphone system, i.e. Personal Handyphone System) system, relate in particular to the power amplifier in the PHS communication terminal.

Background technology

At present, along with the continuous expansion of PHS communication network coverage, (CS CellStation) is widely used in high-power base station.Though reach its maturity and " zero intermediate frequency " scheme of whole CMOS radio frequency technology (adopt whole CMOS technology realization single-conversion can realize changing to accurate zero intermediate frequency by upper frequency, make original radio frequency receive structure and become simple relatively) receptivity of PHS communication terminal is greatly improved, but, when the PHS communication network is in the weak signal zone, for the down link of PHS mobile phone, it is weak that the performance of its up link seems.From it is carried out the result of on-the-spot test, when the PHS communication terminal in the weak signal zone frequent the switching is taken place, cause easily not only that mobile phone goes offline, the call tone quality deterioration, also can frequently register the base station because of the PHS communication terminal increases power consumption.

On the other hand, because the coverage of PHS communication network is insufficient, still there are weak signal area or even blind area in some place, when the user of PHS communication terminal on vehicle or walking when entering the weak signal area conversation, tend to occur exhaling that logical success rate is low, lost network, go offline frequent, switch phenomenons such as the call tone quality that frequently causes is relatively poor.In addition, because the transmitting-receiving uplink downlink between existing base station and the terminal unbalanced in the PHS communication network, user's call tone quality is relatively poor.

Summary of the invention

In the weak signal zone, receive and dispatch the uplink downlink imbalance and the defective of generation at above-mentioned PHS communication network, the invention provides a kind of power amplifier of the PHS of being used for communication terminal.

According to one aspect of the present invention, provide a kind of power amplifier of the PHS of being used for communication terminal.(Herterojunction Bipolar Transistor: heterojunction bipolar transistor) transistor of technology forms in the chip internal cascade this power amplifier by adopting HBT.

Wherein, adopt the PHS communication terminal of this power amplifier to comprise: the power amplifier of proprietary radio-frequency (RF) transceiver, baseband module and its corresponding memory, ancillary equipment, radio-frequency front-end, low noise amplifier, top filter, diverter switch and antenna;

Wherein, if definition V _CCBe above-mentioned transistorized collector voltage, V _SATBe transistorized radio frequency saturation voltage, P _OUTBe the power output of power amplifier, R _LPBe the equivalent load resistance in parallel with transistor collector, then the power output of power amplifier and the relational expression between the equivalent load resistance can be expressed as:

$P_{\mathrm{out}}=\frac{{(V_{\mathrm{CC}}-V_{\mathrm{SAT}})}^2}{{2R}_{\mathrm{LP}}}---\left(1\right)$

Further, if the power output of transistor under saturation condition is certain, then can determine the equivalent load resistance R in parallel with transistorized collector electrode by formula (1) _LPConcrete numerical value.The plural form of termination load impedance can be expressed as Z again _L=R _L+ jX _L, R _LPWith Z _LBetween have a following relation:

$R_{\mathrm{LP}}=\frac{{R_L}^2+{X_L}^2}{R_L}---\left(2\right)$

According to formula (1) and formula (2), the curvilinear path of the constant output of power amplifier just has constant R _LPThe curvilinear path of all termination load impedances of numerical value.

Wherein, if definition P _hBe the transmitting power of PHS communication terminal, P _OUTBe the power output of power amplifier, L _sBe the insertion loss of diverter switch, L _fBe the insertion loss of top filter, G _aBe the gain of antenna, then the transmitting power of PHS communication terminal can be expressed as:

P _h＝P _out-L _s-L _f+G _a (3)

More specifically, the transmitting power of PHS communication terminal is by the power output P of power amplifier _OUTGain G with antenna _aSum deducts the insertion loss L of top filter _fInsertion loss L with diverter switch _sSum.That is to say that the transmitting power of PHS communication terminal is by the power output decision of the gain of antenna and power amplifier, when the antenna gain constant, the transmitting power of PHS communication terminal only changes along with the variation of the power output of power amplifier.

It is pointed out that in wireless communication terminal, is by the modulation system decision of this communication terminal to the requirement of power amplifier in a sense.The permanent envelope modulation that is different from the gsm communication terminal, what the PHS communication terminal adopted is the orthogonal phase shift modulation system (QPSK:Quadrature Phase ShiftKeying) of π/4D QPSK.Because this orthogonal phase shift modulation system is the modulation of a kind of linear digital, the linearity of power amplifier there is very strict requirement, that is to say that the crucial linear index of power amplifier will have fundamental influence to the performance of PHS communication terminal.By formula (3) as can be known, the power output of power amplifier has material impact for the transmitting power of PHS communication terminal, is one of its crucial performance index, and in addition, Adjacent Channel Power Ratio and occupied bandwidth also are the Key Performance Indicators of PHS communication terminal.More specifically, adjacent-channel power (ACP:Adjacent Channel Power) is meant and is departing from the carrier frequency Δ fkHz place that transmits and in ± 96kHz, when the modulated signal of standard is launched, in the measured average power of 0.625ms, and Adjacent Channel Power Ratio (ACPR:Adjacent Channel Power Ratio) just is meant the ratio of adjacent-channel power and modulated transmit signal power; Occupied bandwidth (OBW:Occupied BandWidth) is meant 99% the shared frequency range of transmit signal power, and 0.5% the signal power low side in this frequency range is arranged simultaneously, other 0.5% high-end in this frequency range.The STD-28 standard code, OBW should be greater than 288kHz, because Adjacent Channel Power Ratio and occupied bandwidth have all reflected the linear distortion degree of PHS communication terminal, when it exceeds critical field, must cause interference to the PHS communication network, and power amplifier plays decisive role to these two indexs.In addition, the size of the power output of power amplifier degree of fluctuation with extraneous load variations also plays a part crucial to the communication quality of weak signal area.

According to another aspect of the present invention, a kind of communicating terminal is provided, this communicating terminal contains power amplifier.Wherein, this power amplifier adopts the transistor of HBT technology to form in the chip internal cascade, and in the microwave transmission process, when the load standing wave of this power amplifier increases to 4: 1 owing to mismatch, its key index can not worsen, wherein, reflected wave has the standing-wave ratio VSWR that explains with following formula with respect to incident wave, and VSWR=4: 1

$\mathrm{VSWR}=\frac{1+\left|{\mathrm{\Γ}}_{\mathrm{in}}\right|}{1-\left|{\mathrm{\Γ}}_{\mathrm{in}}\right|}$

Wherein, Γ _InBe apart to be with the termination load | the reflection coefficient of locating.

Adopt power amplifier of the present invention, improved the anti-load driving power of the power amplifier that is positioned at the PHS communication terminal significantly, it is unbalanced to have compensated between base station in the PHS communication network and the terminal transmitting-receiving uplink downlink effectively, even guaranteeing power amplifier suffers under the worst load mismatch situation at phs terminal, the PHS communication terminal still has the output of desirable transmitting power and can not strengthen interference to network, thereby has improved weak signal area phs terminal self calling quality effectively.

Description of drawings

The reader will be well understood to various aspects of the present invention after the reference accompanying drawing has been read the specific embodiment of the present invention.Wherein,

Fig. 1 shows the schematic diagram of the contained main functional modules of PHS communication terminal;

Fig. 2 has illustrated the circuit diagram of microwave transmission;

Fig. 3 has drawn the Smith circle diagram that is used to describe microwave circuit middle impedance coupling; And

Fig. 4 shows several the technical parameter tables of comparisons that power amplifier uses specific standing-wave ratio front and back.

Embodiment

With reference to the accompanying drawings, the specific embodiment of the present invention is described in further detail.

As can be seen from Figure 1, a PHS communication terminal comprises its proprietary radio-frequency (RF) transceiver, baseband module and the pairing memory of this module, and the power amplifier of radio-frequency (RF) transceiver front end, low noise amplifier, top filter, diverter switch and antenna.This power amplifier is mainly formed in the chip internal cascade by the transistor that adopts HBT technology.If definition V _CCBe above-mentioned transistorized collector voltage, V _SATBe transistorized radio frequency saturation voltage, P _OUTBe the power output of power amplifier, R _LPBe the equivalent load resistance in parallel with transistor collector, then the power output of power amplifier and the relational expression between the equivalent load resistance can be expressed as:

$P_{\mathrm{out}}=\frac{{(V_{\mathrm{CC}}-V_{\mathrm{SAT}})}^2}{{2R}_{\mathrm{LP}}}---\left(1\right)$

Further, if the power output of transistor under saturation condition is certain, then can determine the equivalent load resistance R in parallel with transistor collector by formula (1) _LPConcrete numerical value.The plural form of termination load impedance can be expressed as Z again _L=R _L+ jX _L, R _LPWith Z _LBetween have a following relation:

$R_{\mathrm{LP}}=\frac{{R_L}^2+{X_L}^2}{R_L}---\left(2\right)$

According to formula (1) and formula (2), the curvilinear path of the constant output of power amplifier just has constant R _LPThe curvilinear path of all termination load impedances of numerical value.

With reference to Fig. 1, if definition P _hBe the transmitting power of PHS communication terminal, P _OUTBe the power output of power amplifier, L _sBe the insertion loss of diverter switch, L _fBe the insertion loss of top filter, G _aBe the gain of antenna, then the transmitting power of PHS communication terminal can be expressed as:

P _h＝P _out-L _s-L _f+G _a (3)

More specifically, the transmitting power of PHS communication terminal is by the power output P of power amplifier _OUTGain G with antenna _aSum deducts the insertion loss L of top filter _fInsertion loss L with diverter switch _sSum.That is to say that the transmitting power of PHS communication terminal is by the power output decision of the gain of antenna and power amplifier, when the antenna gain constant, the transmitting power of PHS communication terminal only changes along with the variation of the power output of power amplifier.

Fig. 2 shows the circuit diagram of microwave transmission.As shown in Figure 2, if definition Z _LBe termination load impedance, Z ₀Be the characteristic impedance on the transmission line, Γ ₀For being positioned at the reflection coefficient at termination load impedance place, Γ _InBe the reflection coefficient at distance termination load impedance-Shu place, Z _InBe the equiva lent impedance of seeing into to the termination load from distance termination load impedance-Shu, the standing-wave ratio of VSWR for seeing into to the termination load from distance termination load impedance-Shu, then according to the transmission line theory of travelling wave,

Can be expressed as at the reflection coefficient that is positioned at termination load impedance place:

${\mathrm{\Γ}}_0=\frac{Z_L-Z_0}{Z_{L+}{Z}_0}---\left(4\right)$

Can be expressed as at the reflection coefficient that is positioned at apart from termination load impedance-Shu place:

Γ _in＝Γ ₀e ^-j2βl (5)

Wherein, β=2 π/λ, λ are the wavelength of microwave.

The equiva lent impedance Z that sees into to the termination load from distance termination load impedance-I _InCan be expressed as:

$Z_{\mathrm{in}}=Z_0\frac{(Z_L+Z_0)+(Z_L+Z_0)e^{-j2\mathrm{\βl}}}{(Z_L+Z_0)-(Z_L-Z_0)e^{j2\mathrm{\βl}}}$

Can get after the distortion

$Z_{\mathrm{in}}={\mathrm{<figure-callout\; id="0"\; label="Z"\; filenames="A20071000783300121.png"\; state="\{\{state\}\}">Z</figure-callout>}}_0\frac{1+{\mathrm{\&Gamma;}}_{\mathrm{in}}}{1-{\mathrm{\&Gamma;}}_{\mathrm{in}}}---\left(6\right)$

The standing-wave ratio VSWR that sees into to the termination load from distance termination load impedance-Shu can be expressed as again:

$\mathrm{VSWR}=\frac{1+\left|{\mathrm{\&Gamma;}}_{\mathrm{in}}\right|}{1-\left|{\mathrm{\&Gamma;}}_{\mathrm{in}}\right|}---\left(7\right)$

In the microwave transmission field, because according to the microwave transmission line theory, the wavelength that high frequency is corresponding has down shortened, and the size of some electronic components and wavelength are more approaching, at this moment, we can not be again treat each part in the microwave circuit according to the lamped element under the low frequency.The displacement of different cross section process will exert an influence to phase place, thereby variation has also just taken place the pairing impedance of different cross section.In conjunction with Fig. 1 and Fig. 3,, radiate for making energy efficient if when the load impedance of PHS communication terminal is 50 ohm of standard, must make standing-wave ratio as far as possible near 1, and according to formula (4), (5) and (7), the variation of termination load impedance will directly have influence on the standing-wave ratio in impedance cross section.From the schematic diagram of the contained main functional modules of PHS communication terminal shown in Figure 1 as can be known, if the PHS communication terminal is under standby or the talking state, because of the load variations of extraneous factor potato masher antenna to the space, the standing wave of output that finally is reflected to power amplifier is with variation.

Fig. 3 shows the power output of power amplifier, the Smith circle diagram of the variation track of termination load impedance under different condition.Real part and the coordinate of the imaginary part mode that visually be integrated into circle diagram of this figure by complex impedance will be in the microwave theory commonly used strengthened the conceptual understanding to impedance and impedance matching, is a very favorable analysis tool in microwave circuit especially impedance matching.With reference to Fig. 3, each group complex impedance all can be represented on the Smith circle diagram, physical characteristic according to microwave active device especially microwave transistor amplifier, can on the Smith circle diagram, adopt gang's load curve to identify (the discontinuous family of curves among Fig. 3) corresponding to specific power output, and meanwhile power amplifier must satisfy other index performance, so must be the intersection point of each family's curve to the internal output impedance of power amplifier finally.

According to transmission line theory, in the nearly all test macro of microwave, consider the factor of maximum transmission power, the termination load impedance in the industrywide standard definition test macro is 50 ohm.Under ideal conditions, and power amplifier output termination impedance is when being 50 ohm of standard, being sent on the antenna of the power output 100% of power amplifier, the just capable ripple in the microwave transmission.Standing wave is meant for the row ripple, to have a kind of state that reflected wave exists in microwave transmission.Standing-wave ratio circle (constant VSWR circle) curve such as in the Smith of Fig. 3 circle diagram, show respectively, the constant power load curve family (constant power contour) of mapping standing-wave ratio circle (reflected VSWR circle) curve and different capacity grade.

In the Smith circle diagram as shown in Figure 3, be illustrated under the extraneous mismatch situation, fixedly the load impedance locus of points of the termination load impedance of standing-wave ratio etc. the standing-wave ratio circle; The circle expression of mapping standing-wave ratio is mapped to the load impedance locus of points on the load impedance cross section of power amplifier output because of the extraneous mismatch of user communication terminal.Constant power load curve family from figure as can be known, when the power output of power amplifier is steady state value, its termination load impedance numerical value should on the corresponding constant power load line a bit, and these load impedance corresponding points are 50 ohm of round dots of extraneous impedance.When the external world caused deviant 50 ohm of antenna standing wave because of various situations, the termination load impedance that is mapped to the power amplifier output will be the center with 50 ohm of round dots of desired load impedance, formed the less standing-wave ratio circle of a radius.The arbitrarily a bit all mismatch load impedance value under the standing-wave ratio such as representative on this circle, and when this standing-wave ratio circle drops on more sparse regional of constant power load line, the anti-load driving power of power amplifier that is positioned at the PHS communication terminal is stronger, and the power output of power amplifier changes not remarkable.

Based on this theory, we can also in above-mentioned Smith circle diagram, draw be similar to the constant power load line wait Adjacent Channel Power Ratio and etc. the impedance point track of termination load impedance of occupied bandwidth.When the standing-wave ratio of power amplifier was certain numerical value, linear indexes such as the power amplifier output power of PHS communication terminal, Adjacent Channel Power Ratio and occupied bandwidth all can not worsen.Prove by on-the-spot test, adopt the PHS communication terminal of this power amplifier can improve the communication effect of weak signal area really.According to the test empirical value, usually the PHS communication terminal is under the serious situation of load mismatch, the standing-wave ratio that is reflected on the antenna is 8: 1, and according to the transmission line theory of travelling wave, because the existence of diverter switch and top filter Insertion Loss, this moment, the standing-wave ratio corresponding to the power amplifier output was 4: 1.Employing has the PHS communication terminal of the power amplifier of anti-certain standing-wave ratio, and when the communication uplink downlink of weak signal area was unbalanced, call performance significantly improved.

Fig. 4 shows several the performance parameter tables of comparisons that power amplifier uses anti-specific standing-wave ratio (standing-wave ratio is 4: 1) front and back weak signal area.On-the-spot test table from Fig. 4 as can be seen, adopting anti-standing-wave ratio is the PHS communication terminal of 4: 1 power amplifier, the logical success rate of exhaling of weak signal area has improved 8 percentage points, can reach 88%; Switching times has also reduced 20 times; The duration of call is also than having increased nearly 1 hour under the normal weak signal area situation.

Above, describe the specific embodiment of the present invention with reference to the accompanying drawings.But those skilled in the art can understand, under situation without departing from the spirit and scope of the present invention, can also in the specific embodiment of the present invention improve one's methods and power amplifier model etc. is done various changes and replacement.These changes and replace all drop in claims of the present invention institute restricted portion.

Claims (12)

1. power amplifier apparatus that is used for communication terminal, it is characterized in that, described power amplifier adopts the transistor of HBT technology to form in the chip internal cascade, and in the microwave transmission process, when the load standing wave of described power amplifier increased to 4: 1 owing to mismatch, its key index can not worsen, wherein, reflected wave has the standing-wave ratio VSWR that explains with following formula with respect to incident wave, and VSWR=4: 1

$\mathrm{VSWR}=\frac{1+\left|{\mathrm{\&Gamma;}}_{\mathrm{in}}\right|}{1-\left|{\mathrm{\&Gamma;}}_{\mathrm{in}}\right|}$

Wherein, Γ _InBe with the termination load at a distance of being the reflection coefficient at I place.

2. device as claimed in claim 1 is characterized in that described power amplifier is applied to the PHS communication terminal.

3. device as claimed in claim 1 is characterized in that described power amplifier is a linear unit.

4. device as claimed in claim 1 is characterized in that, the bipolar transistor in the described HBT technology adopts the circuit structure of common emitter.

5. device as claimed in claim 1 is characterized in that, the power output of described power amplifier and the relational expression between the equivalent load resistance are approximate can be expressed as:

$P_{\mathrm{out}}=\frac{{(V_{\mathrm{CC}}-V_{\mathrm{SAT}})}^2}{2R_{\mathrm{LP}}}$

Wherein, V _CCBe transistorized collector voltage, V _SATBe transistorized radio frequency saturation voltage, P _OUTBe the power output of power amplifier, R _LPBe equivalent load resistance.

6. device as claimed in claim 5 is characterized in that, described equivalent load resistance is in parallel with described transistorized collector electrode.

7. device as claimed in claim 1 is characterized in that, described power amplifier is that the reflection coefficient at I=O place can be expressed as relational expression at termination load impedance place:

${\mathrm{\&Gamma;}}_0=\frac{Z_L-Z_0}{Z_L+Z_0}$

Wherein, Z _LBe described termination load impedance, Z ₀Be the characteristic impedance on the transmission line.

8. as claim 1 or 7 described devices, it is characterized in that described power amplifier can be expressed as relational expression at the reflection coefficient at the described termination load I of distance place:

Γ _in＝Γ ₀e ^-j2βl

Wherein, β=2 π/λ, λ are the wavelength of microwave.

9. device as claimed in claim 1 is characterized in that, the relation between the transmitting power of the power output of described power amplifier and described PHS communication terminal can be expressed as:

P _h＝P _out-L _s-L _f+G _a

Wherein, P _hBe the transmitting power of PHS communication terminal, P _OUTBe the power output of power amplifier, L _sBe the insertion loss of diverter switch, L _fBe the insertion loss of top filter, G _aGain for antenna.

10. device as claimed in claim 9 is characterized in that, the transmitting power of described PHS communication terminal is by the power output of described power amplifier and the gain decision of described antenna.

11. device as claimed in claim 9 is characterized in that, when the gain constant of described antenna, the transmitting power of described PHS communication terminal changes with the power output of described power amplifier and changes.

12. one kind includes the communicating terminal of power amplifier according to claim 1.

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