DE10104260C2 - Electrical balancing circuit - Google Patents

Description

The invention relates to an electrical balancing circuit.

Such an electrical balancing circuit is known from [1] known.

The electrical balancing circuit described in [1] is shown in FIG. 2.

The electrical balancing circuit 200 , also known as a Boucherot bridge circuit, is usually used to convert a symmetrical electrical signal into an asymmetrical electrical signal or vice versa, that is to say to convert an asymmetrical electrical signal into a symmetrical electrical signal.

The balancing circuit 200 , which is also used as a transformation circuit, has a first input connection 201 and a second input connection 202 , to which the balanced input signal is present. The electrical resistance on the input side is also referred to as R ₁ .

The bridge circuit 200 has four branches, a first branch 203 , a second branch 204 , a third branch 205 and a fourth branch 206 .

In the first branch 203 , a first connection 207 of an inductor L 208 is coupled to the first input connection 201 , the second connection 209 of which is connected to a series-connected first connection 210 of a load resistor R _L 211, a second electrical connection 212 of the load resistor 211 is coupled to the ground potential, generally any reference potential 213 .

The second branch 204 is likewise electrically coupled to the first input connection 201 and has a first capacitance C 214 , the first connection 215 of which is coupled to the first input connection 201 and the second connection 216 of which is coupled to the second connection of the load resistor 211 and the ground potential 213 .

The third branch 205 has a second capacitance 217 , the first connection 218 of which is coupled to the second input connection 202 and the second connection 219 of which is coupled to the second connection of the first inductance 208 .

The fourth branch 206 has a second inductance L 220 , the first connection 221 of which is coupled to the second input connection 202 and the second connection 222 of which is coupled to the second connection 212 of the load resistor 211 and the ground potential 213 .

A power amplifier balancing circuit 300 known from [2] is also shown in FIG. 3.

The power amplifier balancing circuit 300 has an input / output stage 301 .

The input / output stage 301 has two coupled bipolar transistors 302 , 303 , the emitters of which are coupled to one another. The collector of the first NPN bipolar transistor 302 is coupled to a first output 304 of the input / output stage 301 . The collector of the second NPN bipolar transistor 303 is coupled to a second output 305 of the input / output stage 301 .

The input / output stage 301 has an input resistance R ₁ with respect to the other parts of the power amplifier balancing circuit 300 at an operating frequency ω = ω ₁ .

A second capacitance C ₂ 307 is connected between the first output 304 of the input / output circuit 301 and the ground potential 306 .

Furthermore, a second inductance L ₂ 308 is coupled to the first output 304 of the input / output stage 301 , a first connection 309 of the second inductance L ₂ 308 being coupled to the first output 304 and a second connection 310 of the second inductance L ₂ 308 with a first connection 311 of a first capacitance C ₁ 312 , the second connection 313 of which is coupled to the second output 305 of the input / output stage 301 .

Furthermore, a first connection 314 of a first inductance L ₁ 315 is coupled both to the second connection 313 of the first capacitance C ₁ 312 and to the second output 305 of the input / output stage 301 . The second connection 316 of the first inductor 315 is coupled to a supply connection 317 , to which the supply voltage V _{CC is} applied. Furthermore, the second connection 316 of the first inductance L ₁ 315 is coupled to the ground potential 306 via a first DC blocking capacitance 318 .

Furthermore, a first connection 319 of an inductor 320 is coupled to the supply connection 317 , the second connection 321 of which is coupled to the second connection 310 of the second inductance L ₂ 308 and via a second DC blocking capacitance 322 and one in series with the DC blocking capacitance 322 switched load resistor R _L 323 in turn with the ground potential 306 .

Each collector of the two bipolar transistors 302, 303 each has a resistance of R _1/2.

The load resistor R _L 323 usually has a resistance value of 50 Ω.

The inductances and capacities of the bridge circuit can be determined according to the following regulations:

the characteristic impedance of the power amplifier balun 300 is referred to.

With

ω ₁ = 2.π.f ₁ (4)

is the operating frequency at which the power amplifier balancing circuit 300 is operated.

It is assumed that the resistance values R ₁ and Z _{1 are} real. If the resistance value R _{1 has a} complex value, a balancing of the balancing circuit 300 is nevertheless possible, but this makes the bridge circuit more or less asymmetrical, that is, it becomes

C ₁ ≠ C ₂ , (5)

and

L ₁ ≠ L ₂ . (6)

With the known balancing circuits it is not possible to achieve a different impedance transformation and balancing at two different operating frequencies ω ₁ , ω ₂ .

In order to achieve an impedance transformation and balancing at two different operating frequencies ω ₁ , ω ₂ , two separate balancing circuits are to be provided according to the prior art, each of which can be controlled separately from one another, for example via a switch.

Alternatively, second separate signal paths could be provided be, in each case a corresponding balancing circuit is introduced.

From [3] is also a circuit for the transition from one Earth-symmetrical high-frequency arrangement on a earth-unbalanced high-frequency arrangement, or vice versa, known. In this known circuit is the Outer conductor of the asymmetrical arrangement or an auxiliary conductor connected to it connected to the one with the end of the outer conductor forms electrical symmetrical loop. The end of this Auxiliary conductor is conductive with the end of the inner conductor connected.

The invention is therefore based on the problem of specifying a balancing circuit with which an impedance transformation and balancing is possible at two different operating frequencies ω ₁ , ω ₂ and which requires fewer components than a balancing circuit according to the prior art.

The problem is caused by the electrical balancing circuit with the features according to independent claim 1 solved.

Advantageous further developments are in specified in the subclaims.

An electrical balun to convert a balanced signal into an unbalanced signal or to Convert an unbalanced signal to a balanced one Signal has a balun with at least four Components by means of which the symmetrical signal in the unbalanced signal is implemented or by means of which the unbalanced signal into the balanced signal is implemented, with two of the at least four components are inductively acting components, preferably Inductors, and two components capacitive Components are, preferably capacities, which one usual bridge circuit, preferably a Boucherot Bridge circuit, form.  

Each of the two capacitive components of the bridge circuit according to the state of the art is clearly expanded by a additional inductive component, which is in series with the respective capacitive component is switched. To this In each case, a series resonant circuit with the capacitive Component and the additional series connected inductive component formed.

Furthermore, each of the two inductive components one additional capacitive component in parallel switched, whereby a parallel resonant circuit from the inductive component of the non-expanded balun and the respective capacitive connected in parallel Component is formed.

In this way it is achieved that each series resonant circuit capacitive properties in a first frequency range and in a second frequency range that is different too the first frequency range, has inductive properties.

The parallel resonant circuit points in the first Frequency range inductive properties and in the second Frequency range capacitive properties.

The invention thus makes it very compact Balancing circuit specified that at two Operating frequencies can be operated without a explicit switching between the operating frequencies in the  electrical circuit, for example by means of a provided switch for selecting one of the two according to separate state necessarily provided in the prior art Balancing circuits, is required.

Furthermore, a significant number of required components (especially since a switch is no longer required) saved. Furthermore, there is only a single signal path required.

The invention can be clearly seen in that the Capacities are replaced in the usual bridge circuit by connecting a capacitance and a series Inductance and that the inductance of the usual Bridge connection is replaced by a parallel connection from a capacitance and inductance, the Inductors and the capacities according to the below described regulations are preferably dimensioned should.

The respective parallel resonant circuit works in one Frequency range below its resonance frequency inductive and in a frequency range above its resonance frequency capacitive.

The respective series resonant circuit, however, works in one Frequency range capacitive below its resonance frequency and in a frequency range above its resonance frequency inductive.

The inductors can, for example, as a coil or formed as an inductive electrical line his.

The respective capacitive component can be a capacitance or as a capacitive branch line in the Symmetry circuit be formed.  

The electrical balancing circuit is particularly suitable for use in the high frequency range, for example in Mobile radio area with a so-called dual-band Mobile phone. Another area of application of the electrical balancing circuit according to the invention is in a power amplifier or in a preamplifier see.

An embodiment of the invention is in the figures shown and will be explained in more detail below.

Show it:

FIG. 1 is an electrical balun according to an embodiment of the invention;

Fig. 2 is an electrical balun circuit according to the prior art;

Fig. 3 is a power amplifier balun circuit according to the prior art;

FIGS. 4a and 4b show two equivalent circuit diagrams, which the basic characteristics of the electric balun of FIG. 1 in a first frequency range below the resonance frequency of the parallel resonant circuit and the series resonant circuit (Fig. 4a) and in a second frequency range above the resonance frequency of the parallel resonant circuit and the series resonant circuit ( Figures 4b).

Fig. 5 shows a power amplifier balun according to an embodiment of the invention.

Fig. 1 shows the principle of the electric balun 100 displays according to an embodiment of the invention.

The electrical balancing circuit 100 is designed as a bridge circuit with a first input connection 101 and with a second input connection 102 , to which input connections 101 , 102 a symmetrical input signal is applied.

On the input side, the electrical balancing circuit 100 has a first input resistance R ₁ at a first operating frequency ω ₁ and a second input resistance R ₂ at a second operating frequency ω ₂ .

The electrical balancing circuit 100 has four branches in the bridge circuit, a first branch 103 , a second branch 104 , a third branch 105 and a fourth branch 106 .

The first branch, in which only one inductor is provided according to the prior art, now contains a first parallel circuit 107 comprising a first parallel inductor 108 and a first parallel capacitor 109 , a first connection 110 of the first parallel inductor 108 and a first connection 111 of the first parallel capacitance 109 are coupled to one another and to the first input connection 101 . A second connection 112 of the first parallel capacitance 108 and a second connection 113 of the first parallel capacitance are coupled to one another and to a first connection 114 of a load resistor R _L 115 , the second connection 116 of which is coupled to the ground potential 117 , generally any reference potential is.

The second branch 104 contains a first series circuit 118 comprising a first series capacitance 119 and a first series inductor 120 , a first connection 121 of the first series capacitance 119 being coupled to the first input 101 and a second connection 122 of the first series capacitance 119 with a first connection 124 of the first series inductance 120 . The second connection 124 of the first series inductor 120 is connected to the second connection 116 of the load resistor 115 and to the ground potential 117 .

In the third branch 105 , instead of the capacitance provided according to the prior art, a second series circuit 125 comprising a second series capacitance 126 and a second series inductor 127 is contained. A first connection 128 of the second series capacitance 126 is coupled to the second input connection 102 and a second connection 129 of the second series capacitance 126 is coupled to a first connection 130 of the second series inductance 127 , the second connection 131 of which is connected to the first connection 114 of the load resistor R _L 115 is coupled.

The fourth branch 106 has, instead of the inductance provided in accordance with the prior art, a second parallel circuit 132 comprising a second parallel capacitance 133 and a second parallel inductance 134 , a first connection 135 of the second parallel capacitance 133 having a first connection 136 of the second parallel capacitance 134 and is coupled to the second input connection 102 .

The second connection 137 of the second parallel inductor 134 is coupled to the second connection 138 of the second parallel capacitance 133 and to the ground potential 117 and the second connection 124 of the first series inductor 120 .

The values of the AC resistances of the first parallel inductor L _P 108 and the second parallel inductor L _P 134 are the same. Likewise, the values of the AC resistances of the first parallel capacitance _CP 109 and the second parallel capacitance _CP 133 are the same.

Furthermore, the values of the AC resistances of the first series capacitance C _S 119 and the second series capacitance C _S 126 are the same, as are the values of the AC resistances of the first series inductor L _S 120 and the second series inductor L _S 127 .

The respective parallel resonant circuit 107 , 132 with a first operating frequency

ω ₁ = 2.π.f ₁ (7)

operated, wherein the frequency f ₁ is smaller than the resonant frequency of each parallel resonant circuit 107, 132, acts parallel circuit 107, 132 is substantially inductive, that is, the resultant for each parallel resonant circuit 107, 132 equivalent circuit is an inductance (see FIG. Fig. 4a).

In a frequency range in which the frequencies are below the resonance frequency of a respective series resonant circuit 118 , 125 , ie at a second operating frequency

ω ₂ = 2.π.f ₂ (8)

of the series resonant circuit 118, 125 has a capacitive effect, that is the electrical equivalent circuit diagram of such a series circuit is symbolized in the frequency range below the resonance frequency of the series resonant circuit 118, 125 a capacitance, as shown in Fig. 4a.

FIG. 4a thus shows an equivalent circuit diagram 400 of the electrical balancing circuit 100 from FIG. 1, the same elements being provided with the same reference symbols.

In the first branch 103 , the first parallel resonant circuit 107 is replaced by a first inductive element 401 and in the fourth branch 106 the second parallel resonant circuit 132 from FIG. 1 is replaced by a second inductive component 402 .

In the second branch 104 and in the third branch 105 , the respective series resonant circuits 118 , 125 are replaced by a first capacitive component 403 in the second branch 104 and a second capacitive component 404 in the third branch 105 .

Thus, when the electrical balancing circuit 100 shown in FIG. 1 is operated at a first operating frequency ω ₁ or f ₁ , which is smaller than the resonance frequency of the parallel resonant circuit or the resonance frequency of the series resonant circuits, the equivalent circuit diagram shown in FIG known Boucherot Bridge corresponds.

If the electrical balancing circuit 100 is operated at a second operating frequency ω ₂ or f ₂ , which is greater than the resonance frequency of the parallel resonant circuits and than the resonance frequency of the series resonant circuits, the equivalent circuit diagram 410 shown in FIG. 4b results.

If the second operating frequency ω ₂ or f _{2 is} above the resonance frequency of the parallel resonant circuits 108 , 132 , the elements of the parallel resonant circuits behave as a whole as a capacitive element, which is why in the equivalent circuit 410 in the first branch 103 a third capacitive component 411 and in fourth branch 106, a fourth capacitive component 412 is provided instead of a parallel resonant circuit.

At a second operating frequency ω ₂ or f ₂ above the resonance frequency of the series resonant circuits 118 , 125 , the series resonant circuits behave inductively, that is to say they can be replaced by a third inductive component 413 in the second branch 104 and by a fourth inductive component 414 in the fourth branch 105 .

As can be seen from FIG. 4b, the circuit according to this equivalent circuit diagram 410 also represents a Boucherot bridge and thus functionally a balancing circuit, as is known per se from [1].

It can thus be seen, as can be seen from the above explanations, that the electrical balancing circuit 100 according to the invention can be operated at two operating frequencies ω ₁ , ω ₂ , at which the electrical balancing circuit 100 behaves like a conventional balun.

Fig. 5 shows a power amplifier shows balun 500 according to an embodiment of the invention.

The power amplifier balancing circuit 500 has an input / output stage 501 , which contains a first NPN bipolar transistor 502 and a second NPN bipolar transistor 503 .

The emitters of the two bipolar transistors 502 , 503 are coupled to one another and to the ground potential 512 .

Furthermore, the collector of the first bipolar transistor 502 is coupled to a first output terminal 504 of the input / output stage 501 . The collector of the second bipolar transistor 503 is connected to a second output 505 of the input / output stage 501 .

The input / output stage 501 provides at a first operating frequency ω = ω ₁ has a first input resistor R _1, and at a second operating frequency ω = ω ₂ a second input resistor _R.sub.2.

It should be noted that the first operating frequency ω _{1 is} a frequency which is below the resonance frequency of the parallel resonant circuits and series resonant circuits explained below and the second operating frequency is a frequency which is above the respective resonance frequencies.

The first output 504 of the input / output stage 501 is coupled to a first connection 506 of a first series capacitance C _S 507 , the second connection 508 of which is coupled to a first connection 509 of a first series inductance L _S 510 , the second connection 511 of which is in turn coupled to ground potential 512 .

The first series capacitance C _S 507 and the first series inductance L _S 510 together form a first series resonant circuit 513 .

Furthermore, the first output 504 of the input / output stage 501 and the first connection 506 of the first series capacitance C _S 507 are coupled to a first connection 514 of a first parallel inductor L _P 515 and to a first connection 516 of a first parallel capacitance C _P 517 . The second connection 518 of the first parallel inductance L _P 515 is coupled to the second connection 519 of the first parallel capacitance C _P 517 and to a first connection 520 of a first DC blocking capacitance 521 , the second connection 522 of which is connected to a first connection 523 Load resistor R _L 524 is coupled, the second terminal 525 is coupled to the ground potential 512 .

The first parallel inductance 515 and the first parallel capacitance 517 form a first parallel resonant circuit 526 .

Furthermore, the second connection 518 of the first parallel inductor L _P 515 and the second connection 519 of the first parallel capacitance C _P 517 are coupled to a first connection 527 of a second series inductor L _S 528 , the second connection 529 of which is connected to a first connection 530 a second series capacitance C _S 531 is coupled. The second connection 532 of the second series capacitance C _S 531 is coupled to the second output 505 .

The second series inductance L _S 528 and the second series capacitance C _S 531 together form a second series resonant circuit 533 .

With the second output 505 of the input / output stage 501 and the second connection 532 of the second series capacitance C _S 531 there are also a first connection 534 of a second parallel inductor L _P 535 and a first connection 536 of a second parallel capacitance C _P 537 coupled.

The second connection 538 of the second parallel inductance L _P 535 and the second connection 539 of the second parallel capacitance C _P 537 are coupled to one another and to a first connection 540 of a second DC blocking capacitance 541 , the second connection 542 of which is coupled to the ground potential 512 is.

The first connection 540 of the second DC blocking capacitance 541 , the second connection 538 of the second parallel inductance L _P 535 and the second connection 539 of the second parallel capacitance C _P 537 are furthermore coupled to a supply connection 546 to which the operating potential V _CC is created.

The second parallel inductance L _P 535 and the second parallel capacitance C _P 537 together form a second parallel resonant circuit 542 .

Furthermore, a first connection 543 of an inductor 544 is coupled to the supply connection 546 , whose second connection 545 is coupled to the first connection 520 of the first DC blocking capacitance 521 .

The operation of the power amplifier balun 500 corresponds to the operation of the electrical balun, as described above in connection with the description of Figs. 4a and Fig. 4b.

The values of the individual elements of the power amplifier balancing circuit 500 result in the following way:
The first series inductor L _S 510 and the second series inductor L _S 528 result from the following regulation:

The first series capacity C _S 507 and the second series capacity C _S 531 result from the following regulation:

The first parallel inductance L _P 515 and the second parallel inductance L _P 535 result from the following rule:

The first parallel capacitance C _P 517 and the second parallel capacitance C _P 537 arise the following rule:

the characteristic impedances of the bridge circuit at the first operating frequency ω ₁ and the second operating frequency ω _{2 are} designated.

In this context, it is assumed that the input resistors R ₁ , R ₂ at the respective operating frequencies and the resistors Z ₁ and Z _{2 are} real.

In this context it should be noted that:

ω ₂ <ω ₁ . (15)

The following publications are cited in this document:
[1] DE patent 603 816;
[2] A. Krischke, Rothammels Antenna Book, Stuttgart, Frank-Cosmos, 11th edition, 1995;
[3] DE patent 890 070.

LIST OF REFERENCE NUMBERS

100

Electrical balancing circuit

101

First input port

102

Second input port

103

First branch

104

Second branch

105

Third branch

106

Fourth branch

107

First parallel resonant circuit

108

First parallel inductor

109

First parallel capacity

110

First connection first parallel inductance

111

First connection first parallel capacitance

112

Second connection first parallel inductance

113

Second connection first parallel capacitance

114

First load resistor connection

115

load resistance

116

Second load resistor connection

117

ground potential

118

First series resonant circuit

119

First series capacity

120

First series inductance

121

First connection, first series capacity

122

Second connection first series capacity

123

First connection first series inductance

124

Second connection first series inductance

125

Second series resonant circuit

126

Second series capacity

127

Second series inductance

128

First connection, second series capacity

129

Second connection, second series capacity

130

First connection second series inductance

131

Second connection second series inductance

132

Second parallel resonant circuit

133

Second parallel capacity

134

Second parallel inductance

135

First connection second parallel capacitance

136

First connection second parallel inductance

137

Second connection second parallel inductance

138

Second connection second parallel capacitance

200

Electrical balancing circuit

201

First input port

202

Second input port

203

First branch

204

Second branch

205

Third branch

306

Fourth branch

207

First connection first inductance

208

First inductance

209

Second connection first inductance

210

First load resistor connection

211

load resistance

212

Second load resistor connection

213

ground potential

214

First capacity

215

First connection first capacity

216

Second connection first capacity

217

Second capacity

218

First connection second capacity

219

Second connection, second capacity

220

Second inductance

221

First connection second inductance

222

Second connection second inductance

300

Power amplifier balun

301

Input / output stage

302

First bipolar transistor

303

Second bipolar transistor

304

First output input / output stage

305

Second output input / output stage

306

ground potential

307

Second capacity

308

Second inductance

309

First connection second inductance

310

Second connection second inductance

311

First connection first capacity

312

First capacity

313

Second connection first capacity

314

First connection first inductance

315

First inductance

316

Second connection first inductance

317

supply terminal

318

First DC blocking capacity

319

First choke coil connection

320

inductor

321

Second choke coil connection

322

Second DC blocking capacity

323

load resistance

400

First equivalent circuit diagram balancing circuit

401

First inductive component.

402

Second inductive component

403

First capacitive component

404

Second capacitive component

410

Second equivalent circuit diagram balun

411

Third capacitive component

412

Fourth capacitive component

413

Third inductive component

414

Fourth inductive component

500

Power amplifier balun

501

Input / output stage

502

First bipolar transistor

503

Second bipolar transistor

504

First output input / output stage

505

Second output input / output stage

506

First connection, first series capacity

507

First series capacity

508

Second connection first series capacity

509

First connection first series inductance

510

First series inductance

511

Second connection first series inductance

512

ground potential

513

First series resonant circuit

514

First connection first parallel inductance

515

First parallel inductor

516

First connection first parallel capacitance

517

First parallel capacity

518

Second connection first parallel inductance

519

Second connection first parallel capacitance

520

First connection first DC blocking capacity

521

First DC blocking capacity

522

Second connection first DC blocking capacity

523

First load resistor connection

524

load resistance

525

Second load resistor connection

526

First parallel resonant circuit

527

First connection second series inductance

528

Second series inductance

529

Second connection second series inductance

530

First connection, second series capacity

531

Second series capacity

532

Second connection, second series capacity

533

Second series resonant circuit

534

First connection second parallel inductance

535

Second parallel inductance

536

First connection second parallel capacitance

537

Second parallel capacity

538

Second connection second parallel inductance

539

Second connection second parallel capacitance

540

First connection second DC blocking capacity

541

Second DC blocking capacity

542

Second connection second DC blocking capacity

543

First choke coil connection

544

inductor

545

Second inductor coil connection

546

supply terminal

Claims (4)

1. Electrical balancing circuit for converting a balanced signal into an unbalanced signal or for converting an unbalanced signal into a balanced signal,
with a balun with at least four components, by means of which the balanced signal is converted into the unbalanced signal or by means of which the unbalanced signal is converted into the balanced signal,
in which two components of the at least four components of the balun are inductively acting components and two components are capacitively acting components,
in which each of the two capacitive components is connected in series with an additional inductive component, thereby forming a series resonant circuit,
in which each of the two inductive components is connected in parallel with an additional capacitive component, thereby forming a parallel resonant circuit,
in which each series resonant circuit has capacitive properties in a first frequency range and inductive properties in a second frequency range that is different from the first frequency range,
in which each parallel resonant circuit has inductive properties in the first frequency range and capacitive properties in the second frequency range, and
in which the at least four components of the balun form a bridge circuit,
wherein the branches of the bridge circuit alternately contain at least one capacitive component and at least one inductive component. 2. Electrical balancing circuit according to claim 1,
in which at least some of the inductive components are designed as inductors, and / or
in which at least some of the capacitive components are designed as capacitors. 3. Electrical balancing circuit according to claim 1 or 2,
in which at least part of the inductive components is designed as an inductively acting electrical line, and / or
in which at least some of the capacitive components are designed as capacitive stub lines. 4. Electrical balancing circuit according to one of claims 1 to 3,
at which the frequencies of the first frequency range lie below the resonance frequency of the electrical balancing circuit, and
at which the frequencies of the second frequency range lie above the resonance frequency of the electrical balancing circuit.