JP2006014241A - Amplification apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an amplification apparatus capable of avoiding a state where a reception quality is deteriorated or reception is disabled if a high frequency amplifier or a receiver is affected by an interference wave caused by a distortion. <P>SOLUTION: An amplification apparatus comprises a first amplifier 39a to which a first branch transmission line branching an AC signal transmission line for transmitting an AC signal is connected and in which the AC signal inputted from the first branch transmission line is outputted with an amplification value corresponding to a first control signal; a second amplifier 39b to which a second branch transmission line branching the AC signal transmission line is connected and in which the AC signal inputted from the second branch transmission line is outputted with an amplification value corresponding to a second control signal; and an output synthesizing section 310 for outputting the sum of the amplification value of the first amplifier and the amplification value of the second amplifier. The first control signal and the second control signal control an amplification value of any one of the first amplifier and the second amplifier to be reduced so as not to affect the other amplification value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an amplifying apparatus capable of avoiding reception quality deterioration and a state in which reception is not possible when a high-frequency amplifier or receiver used in a portable terminal or the like in a wireless communication network is affected by interference waves due to distortion.

Although different from a portable terminal, as a first conventional example, in the “optical receiver” of Patent Document 1, a low noise amplifier and a low distortion amplifier are used in an optical communication receiving apparatus in order to cope with a wide range of reception level fluctuations. And a low noise amplifier when the signal level is low and a low distortion amplifier when the signal level is low, and a low distortion amplifier when the signal level is high.
In Patent Document 2 as a second conventional example which is another method, a variable attenuator is inserted in the input stage of the low-noise amplifier of the receiving apparatus, the input level is adjusted, and distortion of the low-noise amplifier is reduced. It was avoiding reception quality degradation and inability to receive.
Further, in Patent Document 3 “Distortion Characteristic Control Method” as a third conventional example, in order to obtain a predetermined distortion characteristic in a portable terminal for the purpose of suppressing useless power, the current value of a low noise amplifier is transmitted at the time of transmission. And a configuration for switching between reception and reception.
JP-A-9-298514 (page 4-5, FIG. 1) JP 2000-101461 A (page 8-10, FIG. 1) JP 2001-292037 A

The conventional receiving apparatus is configured as described above. In the first conventional example, in order to switch between the low noise amplifier and the low distortion amplifier, a switch must be inserted in the signal line, and the impedance differs at the time of switching. Therefore, there is a problem that level fluctuation occurs. Furthermore, switching between a low noise amplifier and a low distortion amplifier is determined only by level, but in order to apply this technology in wireless communications, the received signal is not only interfered by the distortion characteristics of the amplifier due to the interference wave but also the desired wave. Since waves are generated, there is a problem that consideration for quality, which is another characteristic important in reception, is not factored in.
In the second conventional example, a variable attenuator is inserted in the input stage of the low noise amplifier, and the noise coefficient (NF) deteriorates due to the loss caused by the variable attenuator, and the reception sensitivity deteriorates. There is.
Furthermore, in the third conventional example, there is a problem that only a simple current setting can be made only for the purpose of saving power during transmission.

  The present invention has been made in order to solve the above-described problems. An amplifier and a receiving apparatus that can avoid reception quality deterioration and a state in which reception cannot be performed when a high-frequency amplifier or receiver is affected by interference waves due to distortion. The purpose is to obtain.

The amplifying apparatus according to the present invention is connected to a first branch transmission line branched from an AC signal transmission line for transmitting an AC signal, and the AC signal input from the first branch transmission line is changed according to the first control signal. A first amplifier that outputs an amplified value;
A second amplifier that is connected to a second branch transmission line branched from the AC signal transmission line, and that outputs the AC signal input from the second branch transmission line with an amplification value corresponding to a second control signal;
An output synthesizer that outputs the sum of the amplified value of the first amplifier and the amplified value of the second amplifier;
The first control signal and the second control signal are a signal for controlling the amplification value of one of the first amplifier and the second amplifier so as not to affect the amplification value of the other. did.

  According to the present invention, two amplifiers having different characteristics are provided so as to operate by switching according to designation, and at that time, a received signal is shared by two amplifiers having different characteristics, for example, a low noise amplifier and a low distortion amplifier. Therefore, there is no switch in the received signal line for switching the amplifier, no loss occurs, and sensitivity is not deteriorated. Further, since there is little impedance variation at the time of switching, there is an effect that the signal loss is further reduced.

Embodiment 1 FIG.
The high-frequency amplifier or receiving device according to the present invention can be used for a receiving device of a mobile phone such as CDMA or PDC. One of the gist of the present invention is to switch the amplifier by controlling the bias of each transistor by connecting the base and the collector of the low noise amplifier and the low distortion amplifier in common (AC). For this reason, it is not necessary to insert a switch or a variable attenuator in the signal line, and no loss occurs, so that sensitivity deterioration does not occur. In addition, since the signal input is connected to the two amplifiers from the beginning and the amplifiers are switched, there is little impedance fluctuation at the time of switching, which is effective for applications that require signal phase continuity.
Furthermore, since the input impedance can be lowered or the matching can be shifted by stepping up and increasing the amplifier current in accordance with the reception quality, the voltage gain value of the amplifier can be continuously reduced. . As a result, the distortion characteristics of the amplifier are improved, so that the generation of interference waves due to the distortion can be suppressed, and a receiving apparatus can be obtained that can avoid reception quality deterioration or reception failure due to the influence of interference waves.

The configuration of the receiver according to this gist will be described.
FIG. 1 is a diagram showing a configuration of a receiving apparatus according to Embodiment 1 of the present invention, and FIG. 2 shows a quality state of the receiving apparatus. FIG. 3 is a control flow diagram for improving distortion characteristics, FIG. 4 shows the configuration of the high-frequency amplifier 3 in FIG. 1, and FIG. 7 is an equivalent model diagram of a low noise amplifier and a low distortion amplifier.
The configuration and operation in this embodiment will be described below with reference to the drawings.

  In FIG. 1, the signal received by the antenna 1 passes through the duplexer 2 to remove the transmission wave from the transmission unit 10 and unnecessary waves other than the external reception band, and is input to the high-frequency amplifier 3. Then, it is amplified by the high-frequency amplifier 3, and its output is removed by the band pass filter 4, and unnecessary waves other than the reception band that could not be sufficiently attenuated by the duplexer 2 are removed and input to the mixer 5. The signal is frequency-converted to a modulated wave signal by the mixer 5 and the local signal from the local station and input to the variable gain amplifier 6. The control circuit 9 controls the gain of the variable gain amplifier 6 so that the output of the variable gain amplifier 6 becomes constant. From the output of the variable gain amplifier 6, the signal of the adjacent channel wave is removed by the low-pass filter 7, and only the signal of the desired channel is taken out and input to the demodulation circuit 8. The demodulation circuit 8 demodulates received data. Further, the demodulating circuit 8 transmits the signal level and data error rate information of the received signal to the control circuit 9, and the control circuit 9 sends the high frequency amplifier switching signal 9b and the current control signal to the high frequency amplifier 3 from the obtained information. At 9c, distortion improvement is controlled.

  Next, the distortion improvement control of the high-frequency amplifier 3 will be described. As shown in FIG. 2, the received signal level 2b is low as in the case 1 and the reception quality 2a is poor due to the interference wave as in the case 1, and the received signal level 2b is high but the interference wave as in the case 2. Therefore, it can be considered that the reception quality 2a is in a bad state. In order to improve these conditions, high frequency amplifier control will be described with reference to the control flow diagram of FIG.

First, assuming the case 1, the control circuit 9 assumes that the reception level from the demodulation circuit 8 and the received data error rate are step S21 (hereinafter step description is omitted), and the reception level 2b is the lower limit of case 1. Control is started when the reception error rate is poor (reception quality 2a is poor) above a certain value. When the reception level is below a certain level, the reception error rate is not influenced by the interference wave, but the received signal is weak and is largely influenced by the thermal noise of the receiver, and thus control is not performed.
If the reception level 2b is above a certain level in S21 but the reception error rate is bad in S22, the third-order distortion is reduced as shown in the prior art document (IEEE JOURNAL OF SOLID STATE CIRCUIT, VOL.33 NO.4APRIL 1998). Since the level is inversely proportional to the third power of the current flowing through the transistor, the distortion characteristic can be improved by flowing a large amount of current into the low noise amplifier 39a. In S23, the control circuit 9 increases the current of the low noise amplifier 39a in a certain step by a current control signal 9c to the high frequency amplifier 3 to improve the distortion characteristics. In order to see the effect, the reception quality after the current increase is monitored to confirm whether the prescribed reception quality has been secured. If not, the current of the low noise amplifier is further increased, and the above routine is executed while confirming whether or not the current value is a predetermined maximum value in S25.

  If the current does not reach the target level even if the current is increased in S23, and the current value of the low noise amplifier 39a reaches the maximum current value, the control circuit 9 uses the amplifier switching signal 9b to control the high frequency amplifier 3 The internal amplifier is switched to the low distortion amplifier 39b. In S26, it is designated to return the current to the initial value, and it is confirmed whether or not the reception quality is secured. If the quality is not achieved, the control is performed to increase the applied current in a certain step in S27, and confirm whether or not the reception quality can be secured in S28, as controlled for the low noise amplifier. Let it be done. This is repeated until the current reaches the maximum value in S29.

Next, a specific configuration and operation of the high frequency amplifier 3 will be described.
As described above, the feature of the configuration in the present embodiment is that a common input that is always connected to two amplifiers having different characteristics, which is the gist of the invention, is given, and the operation of these amplifiers is switched. There is to use either. That is, it is not necessary to insert a change-over switch or the like, impedance fluctuations associated with switching between the use of two amplifiers are continuous, and fluctuations are small. In the case of FIGS. 1 to 4, the two amplifiers are a low noise amplifier 39a and a low distortion amplifier 39b, respectively. The operating point is determined by applying a bias voltage from the current mirror circuit 34a or 34b to the base of either the low noise amplifier 39a or the low distortion amplifier 39b. Naturally, the operating point is set to a different voltage, but the base of the amplifier that does not operate is fixed to the ground potential by the switch 41a or 41b. FIG. 8 is a diagram showing the input / output characteristics of these amplifiers. As shown in FIG. 8, the amplifier whose base is at the ground potential has a voltage (input) -current (output) characteristic that passes through the origin (0, 0) and has a downward convex characteristic curve. Therefore, when the input is a small input voltage 1, as shown by the output current 1, there is almost no output. On the other hand, in the amplifier on the operation side where a voltage is applied to the base from the current mirror circuit, the operating point shifts to a steep slope due to the set bias voltage, and the output current 2 with respect to the input AC voltage from the superimposed RFIN. A large current change output can be obtained. Therefore, in the configuration of FIG. 4, only by applying the amplifier switching control signal 9b, the two types of amplifiers 39a and 39b are practically operated at the bias voltage points set respectively.
As is clear from the above description, the current mirror circuit is configured to apply a set bias voltage to each of the two amplifiers, and the same effect can be obtained even when a configuration using another bias voltage applying circuit is used.

When the low noise amplifier 39a is selected in the high frequency amplifier 3 in S21 of FIG. 3, the low noise amplifier switching switch 32a is turned on by the amplifier switching signal 9b from the control circuit 9, and the base side switch 41a is turned off. The low-noise amplifier 39a is operated, and the switch 41b on the base side of the low-distortion amplifier 39b that performs the reverse operation is turned on, and the low-distortion amplifier switching switch 32b is turned off to stop the operation of the low-distortion amplifier 39b.
Also, the current control signal 9c from the control circuit 9 controls the current source 31a for the low noise amplifier that can switch the current at every step in S23 of FIG. The current source 31a for the low noise amplifier adjusts the current value through the current mirror units 34a, 35a, 36a, and 37a, and then flows the current into the low noise amplifier 39a. Since the current is continuously controlled in this way, the change in the output signal becomes smooth.
The duplexer 2 output received signal is input to the base of the low noise amplifier 39a through a DC (direct current) cut capacitor 38a. Since this connection is fixed regardless of amplifier switching, the impedance does not change by switching. This received signal is output from the connection point of the cascode amplifier 310 whose potential is fixed by the bias 33a and the output load 311.

On the other hand, when the low distortion amplifier is selected, the switching is performed when the distortion characteristic cannot be satisfied by supplying the current to the low noise amplifier 39a in S25 of FIG. 3, or the current is suppressed without requiring low noise so much. A low distortion amplifier 39b is used.
In operation, an amplifier switching signal from the control circuit 9 turns on the low distortion amplifier switching switch 32b and turns off the paired low noise amplifier switching switch 32a. Then, the constant current circuit 31b that can switch the current at every step by the current control signal from the control circuit 9 adjusts the current value through the current mirror units 34b, 35b, 36b, 37b, and 313, and then reduces the current distortion. It flows into the amplifier 39b.
The received signal which is the output of the duplexer 2 is input to the base of the low distortion amplifier 39b through the DC cut capacitor 38b. This received signal is output from the connection point of the cascode amplifier 310, the potential of which is fixed by the bias power supply 33a, with the output load 311.
The resistor 312 is a feedback resistor for securing an input dynamic range, and the input dynamic range is expanded by the amount of voltage generated in the resistor, thereby constituting a low distortion amplifier.

The configuration of the high-frequency amplifier 3 is characterized in that the base and collector of the low noise amplifier 39a and the low distortion amplifier 39b are respectively AC (alternating current) common. For this reason, in the configuration in which an amplifier corresponding to the application is switched and selected by control from the control unit, no switch is required in the reception signal line, and no loss occurs in the reception signal, so that good reception characteristics can be obtained.
In addition, by selectively changing the current of the amplifier stepwise using the current control signal from the control circuit 9, it is possible to improve the distortion of the received signal. Further, the input impedance of the high-frequency amplifier 3 is such that there is little change in impedance matching when the amplifier is switched because the low noise amplifier 39a and the low distortion amplifier 39b are fixedly connected to the signal line at the receiving end. This is effective in applications where the continuity of the phase of the received signal is required.

Further, as shown in FIG. 7, the base resistance Ria of the low noise amplifier is rπ = vi / ib = vi · β0 / ic, and the base resistance Rib of the low distortion amplifier is Rib = rπ + RE (β0 + 1) ≈rπ (1 + gm · R312). Therefore, increasing the current decreases the input impedance of the amplifier and decreases the voltage gain, thereby improving the distortion characteristics of the amplifier.
Since it is configured as described above, the distortion characteristics of the amplifier can be selectively improved by current trade-off, and the reception quality can be ensured.
The current selection is changed in steps in FIGS. 3 and 4, but the command button is determined instead of the configuration, and the time for issuing the control signal is proportional to the time of pressing the command button. May be continuously increased as the command button is pressed.
The reception level has been described as being obtained from the demodulation circuit 8, but it may be obtained from another circuit.

Embodiment 2. FIG.
A configuration in which the dynamic characteristics of the low distortion amplifier are improved and noise resistance is improved will be described.
FIG. 5 is a diagram showing a configuration in which another element is used as the high-frequency amplifier 3 in FIG. 1 for this purpose. That is, instead of a resistor, an inductor 314 is used as a feedback circuit connected to the emitter of the low distortion amplifier 39b as one amplifier.
When the resistor is connected to the emitter, the base resistance of the low distortion amplifier 39b is (1 + gm · feedback resistor 312) times as large as that without the feedback resistor 312. Therefore, there is a possibility that the noise characteristic becomes a problem. is there. However, according to the configuration of FIG. 5, since the inductor 314 is used as the feedback element, the amount corresponding to the base resistance is eliminated, and this problem can be solved.

Similarly, FIG. 6 is a diagram showing a configuration using another element as the high-frequency amplifier 3 in FIG. That is, one amplifier in FIG. 5, the low distortion amplifier 39b, is not a bipolar transistor but a MOS (Moss) type transistor 39c. The current characteristic of the MOS transistor 39c is expressed by second order IC = β / 2 (Vgs−Vth) 2, and in principle there is little third order distortion.
Also with this configuration, the same effect as the configuration of the first embodiment can be obtained.

It is a figure which shows the structure of the receiver in Embodiment 1 of this invention. 6 is a diagram illustrating a control method based on reception quality and reception level of the reception device in Embodiment 1. FIG. 6 is a diagram illustrating a control flow performed by a control circuit in the receiving apparatus according to Embodiment 1. FIG. 3 is a diagram illustrating a detailed configuration of a high-frequency amplifier in the receiving apparatus according to Embodiment 1. FIG. 6 is a diagram illustrating a detailed configuration of a high-frequency amplifier in a receiving apparatus according to Embodiment 2. FIG. 10 is a diagram illustrating a detailed configuration of a high-frequency amplifier in another receiving device according to Embodiment 2. FIG. 3 is a diagram illustrating an equivalent circuit of a high-frequency amplifier in the receiving apparatus according to Embodiment 1. FIG. 6 is a diagram illustrating input / output characteristics of an amplifier in the receiving apparatus according to Embodiment 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Antenna, 2 Duplexer, 3 High frequency amplifier, 4 Band pass filter, 5 Mixer, 6 Variable gain amplifier, 7 Low pass filter, 8 Demodulator circuit, 9 Control circuit, 10 Transmitter, 31a Current source for low noise amplifier, 31b Low distortion Amplifier current source, 32a Low noise amplifier switching switch, 32b Low distortion amplifier switching switch, 33a Bias power supply, 34a Current mirror current compensation transistor for low noise amplifier, 34b Current mirror current compensation transistor for low distortion amplifier, 35a Low noise Amplifier current mirror transistor, 35b Current mirror transistor for low distortion amplifier, 36a Current mirror resistance for low noise amplifier, 36b Current mirror resistance for low distortion amplifier, 37a Current mirror resistance for low noise amplifier, 37b Low distortion Current mirror resistor for amplifier only, 38a DC cut capacitor for low noise amplifier, 38b DC cut capacitor for low distortion amplifier, 39a Low noise amplifier, 39b Low distortion amplifier, 39c Low distortion amplifier (MOS transistor), 41a, 41b switching Switch, 42a, 42b inverter, 310 cascode amplifier, 311 output load, 312 feedback resistance, 313a feedback mirror resistance, 313b inductance mirror equivalent resistance, 314 inductor, S21 reception level detection step, S22 reception quality detection step, S23 low noise Step of increasing current to the amplifier, S24 reception quality detection step, S25 step of detecting whether the current value is maximum, S26 step of switching to the low distortion amplifier and setting the initial value, S27 increase of low distortion A step of increasing the current in the width device, a step of detecting S28 reception quality, and a step of detecting whether the current value is maximum.

Claims (5)

A first branch transmission line branched from an AC signal transmission line for transmitting an AC signal is connected, and the AC signal input from the first branch transmission line is output with an amplification value corresponding to the first control signal. An amplifier;
A second amplifier that is connected to a second branch transmission line branched from the AC signal transmission line, and that outputs the AC signal input from the second branch transmission line with an amplification value corresponding to a second control signal;
An output synthesizer that outputs the sum of the amplified value of the first amplifier and the amplified value of the second amplifier;
The first control signal and the second control signal are signals for controlling the amplification value of one of the first amplifier and the second amplifier to be small enough not to affect the other amplification value. An amplifying device characterized by being.   2. The amplifying apparatus according to claim 1, wherein the first control signal or the second control signal can switch the amplification value output from the first amplifier or the second amplifier in multiple stages.   3. The amplifying apparatus according to claim 1, wherein the first amplifier is a low noise amplifier, and the second amplifier is a low distortion amplifier. A reception level detection means for detecting the reception level of the reception signal and a reception quality detection means for detecting the reception quality of the reception signal;
The amplifying apparatus according to claim 1, wherein the first amplifier and the second amplifier are controlled in accordance with detection results of the reception level detection means and the reception quality detection means.   The amplifying apparatus according to claim 1, wherein the first amplifier or the second amplifier has an inductor connected to a ground side terminal.

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