JP2000022464A - Power module for high frequency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency power module whose power loss is reduced in response to a transmission output of a high frequency signal without losing the linearity and without being susceptible to the effect of a high frequency ground pattern on a mount board. SOLUTION: An output stage of the power module is provided with a push- pull circuit 13 that amplifiers power of a high frequency signal and outputs the signal with an excellent balance and also provided with a bias current setting circuit 17 that sets a bias current of the push-pull circuit in response to an external gain control signal. Thus, the amplifier system connects with a virtual ground to hardly receive the effect of the high frequency ground pattern, and output power is obtained stably without losing the linearity only by adjusting the bias current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is less susceptible to a high-frequency ground pattern on a mounting board, and can prevent a large increase in power loss when narrowing output power (transmission power) for high-frequency signals. The present invention relates to a high-frequency power module having a configuration suitable for circuitization.

[0002]

[Related Background Art] Recently, as one of techniques for simultaneously using radio waves of a limited bandwidth by a plurality of users, WC has been proposed.
DMA (Wideband-Code Division Multiple Access;
Attention has been paid to a wideband code division multiple access system. CD
The MA system is a system in which a large number of carriers are basically set within a limited frequency band, and each carrier is shared by a plurality of users. Noise mixing, occurrence of multipath and fading, and further, handover may occur. It has the advantage that the communication quality can be kept high by suppressing problems and the like.

Now, W-CDMA terminals (mobile phones)
As shown in FIG. 5, for example, a high-frequency unit (RF module) 2 for transmitting and receiving a 2 GHz signal (radio wave) via an antenna (ANT) 1 and a high-frequency unit 2 for modulating a transmission signal. And a baseband unit 3 having a receiving modem 3r for demodulating a signal received via the high-frequency unit 2 and a communication control unit (CCU) and a voice codec. It comprises a main control unit 4 for controlling information communication via the PC. Incidentally, the high frequency unit 2 is a tuplexer 2d.
And a synthesizer unit 2s mainly composed of a PLL circuit and controlling the operating frequencies of the transmitter 2t and the receiver 2r. .

[0004]

When the transmitting section 2t in the high-frequency section 2 is realized, the antenna 1
It is important to ensure the linearity of the transmission power through the GW and to minimize its power consumption. Conventionally, a common-emitter single-ended circuit that has been used in hybrid ICs has been used exclusively for high-frequency power amplifiers incorporated in this type of transmission unit 2t.
However, in a high-frequency power amplifier composed of a single-ended circuit, there is a problem that the amplification degree and the distortion are easily changed due to the influence of the high-frequency ground pattern on the mounting circuit board.

Further, if the bias current of the single-ended circuit is changed in order to control the transmission power, there is a problem that abnormal operation such as oscillation is likely to occur. In the single-ended circuit, it is relatively easy to make the power efficiency at the maximum output level 30% or more, but the power efficiency in the low output level region is as large as about 0.5 to 5%. And it is difficult to extract the maximum performance according to the transmission power.

The present invention has been made in view of such circumstances, and has as its object to reduce the transmission power in accordance with the level of a high-frequency signal, while being hardly affected by a high-frequency ground pattern on a mounting circuit board. Another object of the present invention is to provide a highly practical high-frequency power module that can save power by preventing a large increase in power loss.

[0007]

In order to achieve the above-mentioned object, a high-frequency power module according to the present invention has a push-pull circuit for amplifying a high-frequency signal at its output stage and outputting a balanced output. And a bias current setting circuit that variably sets the bias current according to an external gain control signal, for example, a signal that defines a transmission output.

That is, in the high-frequency power module according to the present invention, the output stage is constituted by a push-pull circuit,
The bias current of the push-pull circuit is set in accordance with an external gain control signal, so that the bias current of the push-pull circuit is not affected by the high-frequency ground pattern on the mounting circuit board. Is optimally set according to the transmission output, thereby reducing power loss.

In a particularly preferred aspect of the present invention, the operating current of a constant current circuit connected to each base of a pair of transistors forming the push-pull circuit is variably set, whereby the push-pull operation is performed. It is characterized by varying the bias current of the circuit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A high-frequency power module according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a W-CDMA terminal (mobile phone).
1 shows a schematic configuration of a high-frequency power module incorporated in the high-frequency section of FIG.
F power amplifier (MMIC; Microwave Monolithic Int)
egrated Circuit). This high-frequency power module is a 2G modulated through an RF modulator.
Hz (specifically, a spread signal having a center frequency of 1.9 GHz and a width of 5 MHz) is converted to a predetermined gain (for example, 30d).
B or more), and outputs the amplified signal to an antenna circuit (not shown) for transmission and output.

The high-frequency power module has two stages of directly-coupled (direct-coupled) differential amplifiers 11 and 12 for balanced input of a high-frequency signal at its input stage. A push-pull circuit 13 that amplifies the high-frequency signal amplified through the power and amplifies and outputs the amplified signal to the antenna circuit is provided at its output stage. The bias current setting circuits 15 and 16 provided in each of the differential amplifiers 11 and 12 operate in response to the internal reference voltage Vref generated by the reference voltage generating circuit 19, and particularly, gain control signals externally applied. Variably sets the bias current of each of the differential amplifiers 11 and 12 according to the above, thereby playing the role of setting the amplification gain of each of the differential amplifiers 11 and 12. The push-pull circuit 1
The bias current setting circuit 17 provided in 3 optimizes and sets the bias current of the push-pull circuit 13 according to the gain control signal, thereby preventing the push-pull circuit 13 from having a large power loss. . Incidentally, the amplification gain in each stage for the high-frequency signal is set to, for example, about 10 dB. In particular, the gain control of 20 dB for varying the output of the high-frequency signal is performed by variably adjusting the bias current in the first-stage differential amplifier 11. Is being done.

More specifically, the high-frequency power module is configured by using a plurality of bipolar transistors T1, T2, to T11, for example, as shown in FIG. The first-stage differential amplifier 11 is mainly composed of a pair of transistors T1 and T2 having emitters connected in common and collectors provided with load resistors R1 and R2, respectively. The differential amplifier 11 composed of the transistors T1 and T2 is driven by a constant current source provided between the emitter and ground (GND) of the transistor T3 and connected to the respective bases of the transistors T1 and T2 via capacitors. Amplifies the balanced input high frequency signal.

The differential amplifier 12 at the next stage mainly includes a pair of transistors T4 and T5 whose emitters are commonly connected and whose bases are directly connected to the collectors of the transistors T1 and T2 of the differential amplifier 11 at the first stage. Be composed. The differential amplifier 12 composed of these transistors T4 and T5
The high frequency signal is balanced and amplified by being driven by a constant current source formed by a transistor T6 provided between the emitter and ground (GND).

The constant current sources formed by the transistors T3 and T6 serve to set the bias currents of the differential amplifiers 11 and 12, respectively. In particular, as described above, the bias current setting circuits 15, 16 The bias currents are set according to the gain control signal under the following conditions, and the amplification gains of the differential amplifiers 11 and 12 are variably set. AGC (automatic gain adjustment) for a high-frequency signal and the like are performed by such variable control of the bias current for each of the differential amplifiers 11 and 12. Note that the bias current setting circuits 15, 1
By controlling the operations of the transistors T3 and T6 by the control circuit 6, it is of course possible to provide the respective differential amplifiers 11 and 12 with functions such as temperature compensation.

A push-pull circuit 13 for power-amplifying a high-frequency signal to drive an antenna circuit has an emitter connected in common and grounded, and a high-frequency signal is balanced-input to a base via a capacitor and amplified between the collectors. It is composed of a pair of transistors T7 and T8 for obtaining an balanced output. In particular, a pair of drive transistors T9 and T10 are provided between the bases of these transistors T7 and T8 as a constant current source for setting the base current, and thus the bias current of the push-pull circuit 13. These drive transistors T9 and T10 are driven by the bias current setting circuit 17 via the transistor T11 to perform a constant current operation, thereby setting the DC bias (bias current) of the push-pull circuit 13. . In particular, resistors R3, R4, R5 inserted into the bases of the driving transistors T9, T10.
Thereby, high impedance is achieved. By increasing the impedance of the driving transistors T9 and T10, the operating conditions of the transistors T7 and T8 for high-frequency signals can be maintained stably while the transistors T7 and T8 are maintained.
The optimization of the bias current of the push-pull circuit 13 is performed, so that an increase in power loss is prevented.

As described above, according to the high-frequency power module in which the input stage is constituted by the two-stage differential amplifiers 11 and 12 connected directly and the output stage is constituted by the push-pull circuit 13, Input balanced,
Since the signal is amplified with a predetermined gain under the virtual ground and balanced and output, the signal system can be floated with respect to the power supply line and the ground line. Therefore, even if the high-frequency power module having the above-described configuration is mounted on a predetermined printed circuit board that forms a high-frequency section of a W-CDMA terminal (cellular phone), it is stable without being affected by the high-frequency ground pattern on the mounting board. It can be operated.

Moreover, since the bias current of each of the differential amplifiers 11 and 12 is variably set according to the gain control signal to vary the amplification gain, the gain control is easy and the gain can be varied stably. Can be. Therefore, for example, when suppressing the output power of the high-frequency signal via the antenna circuit, the amplification gain of each of the differential amplifiers 11 and 12 is set to be small, and the generation of distortion to the high-frequency signal is minimized according to the transmission output level. Push-pull circuit 1 while suppressing
The bias current of No. 3 can be narrowed down, whereby the power loss in the push-pull circuit 13 can be suppressed.

In the push-pull circuit 13 serving as an output stage, a high-frequency signal balanced and output from the differential amplifier 12 is input, and is amplified and output in a balanced manner. It can operate stably without receiving it. Therefore, in a high-frequency power module in which the output stage is constituted by the push-pull circuit 13, the bias current of the push-pull circuit 13 is optimized according to the transmission output, so that the high-frequency signal can be transmitted without undesired power loss. Power can be amplified. Therefore, in conjunction with the gain adjustment for the high-frequency signal by the differential amplifiers 11 and 12, even when the transmission output is narrowed to a medium level or less, for example, the power efficiency in the push-pull circuit 13 is not greatly reduced. It is possible to set the output power. Therefore, even when the output power for the high-frequency signal is varied over a wide range, it is possible to achieve overall power saving.

Therefore, according to the high-frequency power module configured as described above, for example, as shown by the solid line A in FIG.
Even if it is narrowed down to about mW, its power efficiency is 1
It can be maintained as high as about 0%. In particular, in a conventional general high-frequency power module, FIG.
When the transmission power is narrowed down to about 1 mW as shown by a dashed line B in FIG. 2, the power efficiency can be sufficiently increased to save power as compared with the fact that the power efficiency is reduced to about 1%.

FIG. 4 shows a CDM having a maximum transmission power of 1 W.
It shows the ratio of the general frequency of the transmission output variably set in the A terminal (mobile phone) according to the usage environment. As is clear from this characteristic, the CDMA terminal (mobile phone) is rarely driven at full power (maximum output), and is mostly driven with a low output of 10 mW or less. In view of such a tendency, it is natural to improve the quality of the transmission signal (high-frequency signal) at the time of the maximum output, but rather to enhance the signal quality at the time of the low output of 10 mW or less, and at the same time, the power efficiency at that time. It is important to improve overall power saving.
In this regard, according to the high-frequency power module having the above-described configuration, the differential amplifiers 11 and 12 and the push-pull circuit 1
Since the amplification gain and the output power for the high-frequency signal can be easily adjusted without increasing the distortion only by adjusting the bias current for No. 3, the effect can be said to be extremely large.

The present invention is not limited to the above embodiment. For example, depending on the amplification gain for a high-frequency signal, it is possible to provide only one stage of differential amplifier, or conversely, it is also possible to directly connect three or more stages of differential amplifier. Also, with respect to the push-pull circuit 13, it is of course possible to connect the output transistors in Darlington connection depending on the output power. Further, in the embodiment, the circuit is configured using the npn transistor, but it is of course possible to use the pnp transistor. Also, when making a high-frequency power module composed of these transistor circuits into a monolithic IC,
In addition to using a Si bipolar transistor, a so-called M using a III-V compound semiconductor such as GaAs is used.
It is also possible to use an ES-FET or an insulated gate bipolar transistor (IGBT). In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0023]

As described above, according to the present invention, a push-pull circuit is provided at the output stage for amplifying and outputting a high-frequency signal in a balanced manner, and the bias current of the push-pull circuit is controlled by an external gain. A high-frequency power module is realized by including a bias current setting circuit that optimally sets according to a control signal. Therefore, according to the high-frequency power module having the above-described configuration, the high-frequency signal is amplified by virtual grounding, so that the high-frequency signal can be stably operated without being affected by the high-frequency ground pattern on the mounting board. Even if the number of power sources is narrowed down, the power efficiency does not significantly deteriorate, and overall power saving can be achieved. Moreover, the output power can be variably set easily and stably simply by adjusting the bias current for the push-pull circuit. Accordingly, a great effect can be obtained in practical use as a high-frequency power amplifier or the like incorporated in a CDMA terminal.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall schematic configuration of a high-frequency power module according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration example of a differential amplifier and a push-pull circuit of the high-frequency power module shown in FIG. 1;

FIG. 3 is a diagram showing a relationship between transmission output and power efficiency in the high-frequency power module shown in FIG. 1 in comparison with a conventional general high-frequency power module.

FIG. 4 is a diagram showing a relationship between transmission power variably set in a CDMA terminal (cellular phone) and its use frequency.

FIG. 5 is a diagram showing an example of the overall configuration of a W-CDMA terminal (mobile phone).

[Explanation of symbols]

 Reference Signs List 11 differential amplifier (input stage) 12 differential amplifier 13 push-pull circuit (output stage) 15 bias current setting circuit 16 bias current setting circuit 17 bias current setting circuit 19 reference voltage generation circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Go Imai 2 Minami-Aoyama, Minato-ku, Tokyo 1-10-10 Minami-Aoyama A Building 7F Mobile Com Tokyo Co., Ltd. F-term (reference) 5J040 AA02 AA25 AA26 BA05 BA08 BB01 BB07 BB11 BB13 BC02 CA01 CA05 DA07 EA02 FA01 5J091 AA01 AA12 AA16 AA59 CA36 CA58 CA91 FA09 FA10 HA02 HA25 HA29 HA35 KA02 KA12 MA08 SA14 5K022 EE01 EE21

Claims (2)

[Claims] An output stage includes a push-pull circuit for amplifying a high-frequency signal and outputting a balanced output, and a bias current setting circuit for setting a bias current of the push-pull circuit according to a gain control signal. Power module for high frequency. 2. The bias current setting circuit optimizes a bias current of the push-pull circuit by variably setting an operating current of a constant current circuit connected to each base of a pair of transistors forming the push-pull circuit. The high-frequency power module according to claim 1, wherein: