JPH11177449A - Mobile communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently save power and to attain a long life in a built-in battery by forming a shunt resistance which interferes serially in the operation current supply path by means of a MOS transistor and on/off-controlling it. SOLUTION: A logic control unit 2 outputs a power control signal Dx, consisting of a binary logical signal based on the operation state of a portable telephone terminal. When the power saving control signal Dx is set to a low inactive level, the MOS transistor M3 is controlled in an off state, and the operation current path to the transistor T1 of LNA1 is interrupted. Thus, its operation current Id is surely interrupted and a non-power consumption power saving state is set. Furthermore, the MOS transistor M3 for detecting the operation current in order to feedback-control the bias voltage Vb of the transistor T1 is commonly used as the function of a switch circuit for interrupting the bias operation current Id of the transistor T1 at saving of power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a mobile communication device,
Further, the present invention relates to a technology effective when applied to a mobile communication device using a GaAs field-effect transistor for an LNA (low-noise amplifier) in an RF front-end portion, and for example, a technology using CDMA (code division multidimensional connection) technology. The present invention relates to a technology effective for use in a digital mobile phone terminal.

[0002]

2. Description of the Related Art In a mobile communication device using radio waves in the UHF or microwave range, it is necessary to amplify a reception signal from an antenna without deteriorating the S / N ratio and perform reception processing. The LNA of the RF front-end unit receiving high performance is required to have high low noise performance.

In order to improve the performance of this LNA, NF
(Noise Factor) In addition to using a low-noise amplifier having a good (low NF) index, a circuit must be configured with operating conditions such as bias to maximize the performance of the amplifier. Generally, in order to amplify a bipolar transistor or a field effect transistor with low noise, it is necessary to apply a bias voltage that constantly supplies an operation current of a certain level or more as a bias current.

On the other hand, mobile communication devices, especially recent mobile telephone terminals, are strongly required to be small and lightweight and have a long battery life. In particular, a long life in a reception standby state is strongly desired. However, in mobile phone terminals that supply operating current entirely with the built-in battery, there is a contradictory factor in reducing the size and weight of the terminal and prolonging the life of the battery. Therefore, there is a contradiction that it is difficult to reduce the size and weight of the battery in order to extend the life of the battery.

In order to extend the life of the battery, the operating current during reception standby, which is continuously consumed regardless of the presence or absence of a telephone call, is reduced from the operating current during transmission, which is temporarily consumed only during a telephone call. That is more effective. However, in order to ensure predetermined reception performance, especially low noise performance, it is necessary to supply an operating current (bias current) of a certain degree or more to the amplifying element of the LNA as described above. That is, in a mobile communication device using a built-in battery as a power source, such as a mobile phone terminal, reducing the operating current consumed by the amplifying element of the LNA as a bias current is effective in extending the battery life.

The inventor of the present invention controls the switching of the bias voltage applied to the LNA amplifying element by a high / low binary control signal, thereby reducing the operating current consumed by the amplifying element as a bias current in a communication scene. In order to reduce the time-average current consumption, the power saving control was studied so that the cut-off was finely controlled in accordance with the control.

FIG. 4 shows a main part of a portable telephone terminal studied by the present inventor.

FIG. 1 shows an RF front end portion of a mobile phone terminal and its peripheral portion, where 11 is a transmitting / receiving antenna, 12 is an antenna duplexer, 1 is an LNA, 2 is a logical control unit, and 3 is a bias. It is a control circuit.

In FIG. 1, LNA1 is a low NF bipolar transistor T1 for high frequency low noise amplification, capacitors C1, C2, C3, Cp, inductances L1, L2,
It is constituted by a resistor Rb or the like, and preliminarily amplifies a radio reception signal wave input from the antenna 11 via the branching filter 12 and sends it to a receiving circuit (not shown) in a subsequent stage.

The logical control unit 2 is configured using a microcomputer, and controls the entire system in the terminal including the LNA 1.

The bias control circuit 3 includes a current detecting shunt resistor Rs interposed in series between the low noise transistor T1 and the power supply potential Vcc, an operational amplifier circuit 31 forming a negative feedback amplifier circuit, and a constant reference voltage Vr. , A switch circuit SW1 for controlling ON / OFF of the reference voltage Vr, CMOS transistors M1 and M2 forming an inverter logic circuit, and the like. The divided voltage Vs at the shunt resistor Rs is used as the reference voltage Vr. A DC negative feedback loop is formed to feedback-control the input bias voltage (base bias voltage) Vb of the transistor T1 so as to have a predetermined magnitude (Vr = Vs = Vcc-Vd) determined by the following equation.

As a result, the bias operation current (collector bias current) Id of the transistor T1 is reduced to the reference voltage Vr.
Operating current I by turning on / off the reference voltage Vr.
On / off control of d can be performed.

Therefore, the on / off of the reference voltage Vr is determined by the high / low 2 provided by the logic control unit 3.
If the power save control signal Dx is used, power save control can be performed to reduce time-average power consumption by selectively energizing the operating current Id of the low-noise transistor T1 only when necessary. Becomes

The mobile communication terminal device is described in, for example, “Nikkei Electronics 199” published by Nikkei BP.
The outline is described in the January 13, 2007 issue (no. 680), pages 65 to 90 (special feature: mobile phones).

[0015]

However, it has been clarified by the present inventors that the above-described technology has the following problems.

That is, the above-described technique is effective for a mobile communication device using a transistor having an enhancement characteristic as shown in FIG. 5A as a low noise amplifier of the LNA. In a device using a transistor having a depletion characteristic as shown in FIG. 3B, a considerable bias operation current Id flows even in a power save state in which the bias voltage Vb is reduced to zero.
It is not possible to obtain a sufficient effect to reduce the time-average power consumption.

In a low band such as the HF band, the level of external noise such as static electricity and urban noise is high, so that there is a limit to the expansion of the communication range only by improving the reception performance, but 1 GHz at which the level of the external noise decreases. In the mobile communication device using radio waves in the UHF or microwave range, improving the reception performance is effective for reducing the scale of the transmission power, and further reducing the scale of the transmission output increases the efficiency of frequency use. However, an amplifying element such as a GaAs field effect transistor having excellent high frequency characteristics and low noise characteristics is indispensable. However, most of the transistors having such characteristics, especially the characteristics of the GaAs field effect transistor, are not enhancement but depletion.

As described above, in a mobile communication device that uses UHF or microwaves in the microwave range of 1 GHz or more, a depletion-type transistor such as a GaAs field-effect transistor can be used in an LNA.
Although it is desirable to reduce the transmission power and improve the frequency use efficiency, there is a problem that the use of the depletion type transistor is a great obstacle to extending the life of the battery.

In order to reliably cut off (cut off) the bias operation current Id of the depletion type transistor, as shown in FIG. 5B, a negative bias voltage (Vb <Vth <) having a polarity opposite to the power supply voltage. 0) may be applied, but in this case, an inverter circuit for generating a negative voltage and a control circuit capable of switching the bias voltage over both positive and negative polarities are required, so that the device is complicated and large-scale. Problem arises.

It is an object of the present invention to provide a mobile communication device that uses radio waves in the UHF or microwave range with a relatively simple configuration while maintaining the receiving performance of the built-in battery by efficient power saving control. An object of the present invention is to provide a technology that enables a longer life.

The above and other objects and features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0022]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, this is a mobile communication device which operates by the supply current from the built-in battery (6), and uses a depletion type transistor (T1) as an amplifying element.
NA (1), a shunt resistor (Rs) interposed in series in the operating current supply path of the transistor (T1), and a divided voltage (Vs) at the shunt resistor (Rs) become predetermined control target values. As described above, the negative feedback circuit for feedback-controlling the bias voltage (Vb) of the transistor (T1) is provided, and the shunt resistor (Rs) is formed by the ON resistance of the MOS transistor (M3).
The on / off control of the OS transistor (M3) is performed by a high / low binary power save control signal (Dx).

According to the above-described means, it is possible to reliably shut off the bias operation current of the depletion type transistor during power saving by using the current detecting element for feedback-controlling the bias voltage during the amplification operation. This makes it possible to extend the life of the built-in battery by efficient power saving control while ensuring the reception performance of mobile communication devices that use UHF or microwave radio waves with a relatively simple configuration. Is achieved.

It is preferable to use a GaAs field effect transistor (T1) as an amplifying element constituting the LNA (1). As a result, it is possible to improve the minimum reception level by reducing noise particularly in the UHF or microwave region.

Further, a first MOS transistor (M3) interposed in series with an operating current supply path of the low noise amplifier (T1) constituting the LNA (1), and a constant current source (3
3) The second MO that is supplied with a constant current (Ir) by
The voltage (Vs) divided by the ON resistance of the S transistor (M6) and the first MOS transistor (M3) is equal to the voltage (Vr) divided by the ON resistance of the second MOS transistor (M6). A negative feedback circuit for feedback-controlling the bias voltage Vb of the low-noise amplifier element (T1), and the first MOS transistor (M3) and the second MOS transistor (M6) have a pair configuration having the same characteristics. I do. As a result, it is possible to compensate for the error factor due to the variation in the on-resistance in each of the MOS transistors (M3, M6).

A resistor (R) is connected to the constant current source (33).
2), the bias voltage (Vb) is feedback-controlled by a reference voltage (Vr) generated by dividing the voltage, and a resistor (R1) paired with the resistor (R2) is connected to a low-noise amplifier ( The operating current supply path of T1) is interposed in series. As a result, it is possible to cancel out the variation in the resistance values of the resistors (R1, R2).

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of a mobile communication device to which the technology of the present invention is applied.

The mobile communication device shown in FIG. 1 is configured as a CDMA type mobile phone terminal which operates by a current supplied from a built-in battery 6.
1, an antenna duplexer 12, an LNA 1, a logic control unit 2, a bias control circuit 3, a transmission / reception main circuit 4, and the like.

LNA1 is GaAs for low-noise high-frequency amplification.
s field-effect transistor T1, capacitive elements C1, C2, C
3, a radio reception signal input from the antenna 11 via the duplexer 12 is pre-amplified and sent to the transmission / reception main circuit 4. The GaAs field-effect transistor T1 exhibits a particularly excellent low-noise characteristic in a frequency region equal to or higher than UHF, but has a depletion characteristic as shown in FIG.

The logical control unit 2 is configured using a microcomputer and controls the entire system including the LNA 1.

The bias control circuit 3 forms a MOS transistor M3 interposed in series in a current path between the low noise transistor T1 and the power supply potential Vcc, an operational amplifier circuit 31 forming a negative feedback amplifier circuit, and an inverter logic circuit. C
It comprises MOS transistors M1 and M2, a reference voltage source 32 for generating a constant reference voltage Vr, and the like. Here, the MOS transistor M3 forms a shunt resistor Rs interposed in series with the operating current path of the transistor T1 due to its ON resistance.

The transmission / reception main circuit 4 includes a reception frequency converter 4
1, reception IF unit 42, transmission IF unit 43, transmission frequency conversion unit 44, high-frequency power module 45, PLL unit 46 for generating a local oscillation signal, analog control unit for detecting reception electric field strength and controlling transmission output 47, a baseband unit 48 for centrally performing modulation / demodulation processing and multiplexing processing of transmission / reception signals, a handset 49, an operation panel 50, and the like. The radio reception signal preliminarily amplified by the LNA 1 is IF-converted by the frequency conversion unit 41, amplified to a predetermined level by the IF unit 42, and then demodulated by the baseband unit 48.

Next, the operation will be described.

In FIG. 1, a logic control unit 2 outputs a power save control signal Dx composed of a high / low binary logic signal based on the operation state of the portable telephone terminal. The power save control signal Dx is transmitted as an on / off control signal to the gate of the MOS transistor M3 via the CMOS transistors M1 and M2.

Here, when the power save control signal Dx is at a high active level, the MOS transistor M3 is controlled to be on. At this time, the MOS transistor M
3 is a transistor T1 of LNA1 due to its ON resistance.
Operate as a shunt resistor Rs interposed in series in the operating current supply path of the first embodiment. The operational amplifier circuit 31 operates so that the voltage Vd appearing on the output side of the shunt resistor Rs, that is, the drain side of the transistor T1 is at the same level (Vr = Vs = Vcc-Vd) as the predetermined reference voltage (Vcc-Vr). L
The gate bias voltage Vb of the transistor T1 of NA1 is feedback-controlled. As a result, the transistor T1 of the LNA1 performs preliminary amplification of the radio reception signal under the bias condition set by the reference voltage Vr.

When the power save control signal Dx is set to the low inactive level, the MOS transistor M3 is controlled to be in the off state, and cuts off the operating current path of the LNA1 to the transistor T1. Thereby, the transistor T1 is reliably shut off its operating current Id irrespective of the depletion / enhancement mode, and is set to the non-power-consuming power save state.

At this time, it should be noted that the MOS transistor M3 for detecting the operating current for feedback-controlling the bias voltage Vb of the transistor T1 has a bias operating current Id of the transistor T1 during power saving.
And also functions as a switch circuit for shutting off. That is, it is possible to reliably shut off the bias operation current of the depletion type transistor T1 at the time of power saving by using the current detecting element for performing the feedback control of the bias voltage Vb at the time of the amplification operation.

Thus, with a relatively simple configuration,
It is possible to extend the life of the built-in battery by efficient power saving control while ensuring the reception performance of a mobile communication device that uses UHF or microwave waves.

FIG. 2 shows the configuration of a mobile communication device according to a second embodiment of the present invention.

Focusing on the differences from the one shown in FIG. 1, in the device shown in FIG. 1, a constant current source 3 for supplying a constant current Ir is used as a reference voltage source 32 for generating a reference voltage Vr.
3. MOS for transmitting the constant current Ir to the current mirror
A MOS transistor M6 is provided which generates a constant voltage (Vr) according to the mirror current when the mirror current transmitted to the transistors M4 and M5 and the MOS transistor M5 is supplied. The reference voltage Vr is M
It is taken out from between the OS transistors M6 and M5 and supplied to the operational amplifier circuit 31 as a comparison reference voltage.

In the above-described configuration, the MOS transistor M3 for detecting the operating current Id of the transistor T1 by the on-resistance and the MOS transistor M6 for generating the reference voltage Vr by the on-resistance have the same characteristics. The pair configuration has an advantage that an error factor due to a variation in the on-resistance of each of the MOS transistors M3 and M6 can be offset and compensated.

FIG. 3 shows the configuration of a mobile communication device according to a third embodiment of the present invention.

The device shown in FIG.
2 are connected in series to generate a reference voltage Vr. A resistor R1 is inserted in series into an operating current supply path of the transistor T1, and the two resistors R1 and R2 are paired. , The variation in the resistance values of the resistors R1 and R2 can be canceled out. As a result, the circuit configuration can be greatly simplified as compared with that of FIG.

As described above, the above embodiment is directed to a mobile communication device which operates by a supply current from a built-in battery (6), and uses an LNA (1) using a depletion type transistor (T1) as an amplifying element. The shunt resistor (Rs) interposed in series with the operating current supply path of the transistor (T1) and the transistor (T1) are set such that the divided voltage (Vs) at the shunt resistor (Rs) becomes a predetermined control target value. T1) has a negative feedback circuit for feedback-controlling the bias voltage (Vb), forms the shunt resistor (Rs) with the on-resistance of the MOS transistor (M3), and furthermore, turns the MOS transistor (M3) high / low. On / off control is performed by a binary power save control signal (Dx). The bias operation current of the transistor can be reliably shut off by using a current detection element for feedback-controlling the bias voltage at the time of the amplification operation, thereby having a relatively simple configuration. The effect is obtained that the built-in battery life can be extended by efficient power save control while securing the reception performance of the mobile communication device using the radio wave in the UHF or microwave range.

Further, since the GaAs field effect transistor (T1) is used as the amplifying element constituting the LNA (1), the noise in the UHF or microwave region is reduced to reduce the minimum reception level. The effect that improvement can be achieved is obtained.

Further, a first MOS transistor (M3) interposed in series with an operating current supply path of the low noise amplifier (T1) constituting the LNA (1), and a constant current source (3
3) The second MO that is supplied with a constant current (Ir) by
The voltage (Vs) divided by the ON resistance of the S transistor (M6) and the first MOS transistor (M3) is equal to the voltage (Vr) divided by the ON resistance of the second MOS transistor (M6). A negative feedback circuit for feedback-controlling the bias voltage Vb of the low-noise amplifier element (T1), and the first MOS transistor (M3) and the second MOS transistor (M6) have a pair configuration having the same characteristics. Therefore, an effect is obtained that an error factor due to a variation in on-resistance in each of the MOS transistors (M3, M6) can be offset and compensated.

Further, a resistor (R) is connected to the constant current source (33).
2), the bias voltage (Vb) is feedback-controlled by a reference voltage (Vr) generated by dividing the voltage, and a resistor (R1) paired with the resistor (R2) is connected to a low-noise amplifier ( Since the operating current supply path of T1) is interposed in series, the resistance (R
1, R2) can be compensated for.

Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

In the above description, the case where the invention made by the inventor is applied to a portable telephone terminal, which is the field of use as the background, has been mainly described. However, the present invention is not limited to this case. It can also be applied to unmanned base terminals that operate on.

[0052]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

That is, with a relatively simple configuration, U
It is possible to extend the life of the built-in battery by efficient power save control while ensuring the reception performance of a mobile communication device that uses radio waves in the HF or microwave range.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a mobile communication device to which the technology of the present invention is applied;

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a main part of a mobile communication device studied prior to the present invention;

FIG. 5 is a diagram showing characteristics of an amplification element used in an LNA.

[Explanation of symbols]

Reference Signs List 11 transmission / reception antenna 12 antenna duplexer 1 LNA 2 logic control unit 3 bias control circuit 4 transmission / reception main circuit 6 built-in battery T1 low noise high frequency amplifying element (GaAs field effect transistor) C1 to C3 capacitance element Cp capacitance element L1, L2 inductance Rb Resistance M1 to M6 MOS transistor Rs Shunt resistance for detecting operating current R1, R2 Resistance 31 Operational amplifier circuit 32 forming a negative feedback amplifier circuit 32 Reference voltage source 33 Constant current source 41 Reception frequency conversion unit 42 Reception IF unit 43 Transmission IF unit 44 Transmission frequency conversion unit 45 High frequency power module 46 PLL unit 47 Analog control unit 48 Baseband unit 49 Handset 50 Operation panel Vb bias voltage Id Bias operation current Vs Divided voltage (Id detection voltage) Dx Power save control signal Vr Reference voltage Ir Constant current

Claims (4)

[Claims] 1. A mobile communication device which operates by a supply current from a built-in battery, comprising: a low-noise amplifier using a depletion-type transistor as an amplification element; and a shunt resistor interposed in series in an operation current supply path of the transistor. A negative feedback circuit that feedback-controls the bias voltage of the transistor so that the divided voltage at the shunt resistor becomes a predetermined control target value,
The shunt resistor is formed by the ON resistance of a MOS transistor.
A mobile communication device wherein on / off control is performed by a value power save control signal. 2. The mobile communication device according to claim 1, wherein a GaAs field effect transistor is used as an amplifying element constituting the low noise amplifier. 3. A first MOS serially interposed in an operating current supply path of a low noise amplifier element constituting a low noise amplifier.
A transistor, a second MOS transistor to which a constant current is supplied by the constant current source, and a voltage divided by the on-resistance of the first MOS transistor. A negative feedback circuit for feedback-controlling the bias voltage of the low-noise amplifying element so as to be equal;
3. An OS transistor and a second MOS transistor having a pair configuration having the same characteristics.
A mobile communication device according to claim 1. 4. A bias voltage is feedback-controlled by a reference voltage divided by connecting a resistor to a constant current source in series, and a resistor paired with the resistor is connected to an operating current supply path of a low-noise amplifier. The mobile communication device according to any one of claims 1 to 3, wherein the mobile communication device is interposed in series.