JP2009165100A - High-frequency amplifier, high-frequency module and mobile wireless apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency amplifier having high linearity, easy to integrate and resistant to a variation in a transistor characteristic due to a process variation. <P>SOLUTION: This high-frequency amplifier has a bias circuit to bias an amplifying element for amplifying a high frequency. The bias circuit includes a feed back circuit, in which a circuit with a low pass characteristic and having capacity having grounded one end is inserted into a feedback group of its feedback circuit. Stable bias voltage is thus supplied, for improving the linearity of the high-frequency amplifier. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an amplifier for amplifying a high-frequency analog signal, a high-frequency module, and a mobile radio using the same, and is particularly suitable for wireless communication employing a CDMA system, an OFDM (Orthogonal Frequency Division Multiplexing) system, and an extended system thereof. The present invention relates to a high-frequency amplifier, a high-frequency module, and a mobile radio using the same.

  Conventionally, amplifiers for high-frequency analog signals such as those described in Patent Documents 1 to 7 are known.

  In Patent Document 1, as a high-frequency amplifier, a bias circuit of a bipolar transistor for signal amplification is configured by a feedback loop, and a self-bias resistor that has been conventionally grounded to this bias circuit is deleted. A bias circuit for an amplifier circuit is disclosed. According to Patent Document 1, it is described that the input resistance viewed from the input terminal can be increased by deleting the resistance of the bias circuit.

  In Patent Document 2, for example, in FIG. 5, a distortion compensating diode is connected via a first resistor between a base terminal and a base bias supply terminal of a bipolar transistor 101 for signal amplification. A power amplifier is disclosed in which a connection point between the first resistor and the distortion compensating diode is grounded. According to Patent Document 2, it is stated that the above configuration can suppress the change in the bias point even if the temperature changes.

  In Patent Document 3, for example, FIG. 1 has a bias voltage supply point and a constant voltage source connected to the base of a high frequency amplification transistor, and a rectifying transistor and a constant current source are connected to the bias voltage supply point. A bias voltage supply circuit is disclosed. According to Patent Document 3, the bias voltage supply circuit has a bias characteristic that once increases as the input power increases and decreases after passing the pole, so that a high-frequency amplifier circuit having excellent saturation characteristics can be obtained. It is stated.

  In Patent Document 4, for example, a preamplifier (FIG. 5) includes a feedback loop including a current signal input unit, a signal amplification transistor, and a control current source connected to the input unit and diverting the current signal. Current-voltage converter). According to Patent Document 4, it is stated that the output average potential becomes constant by automatically adjusting the current distribution ratio at the time of large input with the above configuration.

  In Patent Document 5, a transistor in which a collector and a base are directly connected is used as a parent transistor constituting a current mirror, and an inductor outside the chip connected to a base of a pair of transistors and a parent transistor are connected. A transmission amplifier in which a low-pass filter is configured by a capacitor connected between a base and an emitter is disclosed. According to Patent Document 5, with the above configuration, a high-frequency signal is prevented from being input to the parent transistor side, whereby a base bias potential does not decrease even at high output, and a high-output transmission amplifier can be realized. It is stated.

  In Patent Document 6, for example, in FIG. 6, an amplifier that amplifies an input signal, a reference amplifier that includes a current mirror circuit and generates a DC component of the input signal corresponding to the input power level, and amplifies the DC component. A power amplifier module including a DC current amplifier (dummy circuit) that supplies the amplifier is disclosed. According to Patent Document 6, it is stated that a highly efficient and low distortion power amplifier module can be realized with good reproducibility.

  Patent Document 7 discloses a bias generator connected to a gate terminal of a MOS transistor, a low-pass filter circuit connected between an input portion of an input signal and the bias generator, and the input portion and the MOS transistor. A semiconductor device having a high-pass filter circuit connected between gate terminals is disclosed. An object of the invention of Patent Document 7 is to provide a technology capable of accurately compensating for variations in bias conditions of a MOS device due to device temperature variations and / or process variations.

  An amplifier including a dual bias feed circuit described in Non-Patent Document 1 is also known. 12 to 14 show a circuit disclosed in Non-Patent Document 1. FIG. That is, Non-Patent Document 1 refers to the inductor bias feed circuit 710 and the resistance bias feed circuit 810 shown in FIGS. 12 and 13 and proposes the dual bias feed circuit of FIG.

In FIG. 12, 701 to 703 are transistors, 704 is an inductor, and 705 is a resistor. In FIG. 13, 801-803 are transistors, 804 are capacitors, 805-808 are resistors, 810 is an IC section, and 820-82 is a matching circuit. Further, the dual bias feed circuit of FIG. 14 is a circuit in which a diode bias feed circuit 900 is added to the resistance bias feed circuit 810. The diode bias feed circuit 900 includes transistors 901 to 903 and a resistor 904. According to Non-Patent Document 1, it is described that the linearity of the resistance bias feed circuit is improved by adopting the dual bias feed circuit.

Japanese Patent No. 3125723 Japanese Patent No. 3514720 JP 2005-228196 A Japanese Patent Laid-Open No. 09-130157 JP 2001-94362 A JP 2001-284984 A JP 2005-184838 A Eiji Taniguchi, 6 others, The Institute of Electronics, Information and Communication Engineers IEICE Technical Report “Dual Bias Feed SiGe HBT Linear Low Noise Amplifier”, MW2001-25, OPE2001-12 (2001-06), p. 1-5

  As a wireless standard in recent years, a digital modulation method such as a CDMA method and an OFDM method has been adopted for many mobile wireless devices such as a wireless LAN and WiMAX. In these digital modulation systems, high linearity is required for the amplifier.

That is, unlike the conventional GMSK method, which does not change the power of the high-frequency signal based on FSK (frequency modulation method), the power of the high-frequency signal changes with time in the CDMA method and the OFDM method. The peak value is considerably larger than the average value. In particular, in the OFDM scheme, N different frequency carriers are multiplexed and the frequency interval of each signal is narrow, so the peak power value of the multiplexed signal is the average power value as shown in FIG. 5 to 16 times (7-12dB). Therefore, an amplifier for an application that amplifies an analog signal having a large difference between the peak power value and the average power value has high linearity with respect to an input signal over a wide range from a small signal operation to a large signal operation. Is required.

However, the conventional high-frequency amplifier has not been sufficiently considered in this regard.
That is, when the digital modulation method such as the OFDM method is a target, the amplifier disclosed in Patent Document 1 cannot avoid a decrease in the potential of the bias point during a large signal operation. Obtaining high linearity is considered difficult.

  Similarly, in the amplifiers disclosed in Patent Documents 2 and 3, the potential at the bias point of the amplifier fluctuates with respect to a wide range of high-frequency input signals, and high linearity is obtained with respect to such input signals. It is considered difficult.

  The feedback loop of the current-voltage converter disclosed in Patent Document 4 is for adjusting the input impedance of the entire circuit, has no function of controlling the potential of the bias point of the signal amplification transistor, and has a wide range. It is considered difficult to obtain high linearity with respect to the high frequency input signal.

Furthermore, the low-pass filter disclosed in Patent Document 5 is provided outside the feedback loop. In addition, since it is externally attached to the semiconductor integrated circuit, it is difficult to integrate, and it is considered that there is a problem with miniaturization.
In addition, when the inductance of the low-pass filter disclosed in Patent Document 5 is replaced with a resistor and integrated in a semiconductor integrated circuit, this resistor increases the output impedance of the bias circuit. The increase in current causes a drop in bias voltage, which is considered a problem.

  Similarly, the power amplifier module disclosed in Patent Document 6 is provided with a dummy amplifier in addition to the reference amplifier, which is considered to be problematic for miniaturization.

  Further, the semiconductor device disclosed in Patent Document 7 has a low-pass filter for separating the reference voltage of the bias circuit from the high-frequency signal and DC voltage mixed outside the chip. This low-pass filter is a feedback loop of the bias circuit. In such a configuration, it is considered difficult to obtain high linearity for a wide range of input signals.

  On the other hand, in the example of FIG. 12 of Non-Patent Document 1, in the resistance bias feed circuit 810, a capacitor 804 exists in the bias circuit. This capacitor 804 is for preventing oscillation of the bias circuit, and is designed to have a cut-off frequency as low as possible. In many cases, the cutoff frequency is designed to be about several KHz. Further, during large signal operation, as shown in the large signal equivalent circuit of FIG. 15, a resistor 806 is connected in series with the capacitor 804, so that it is not grounded at a high frequency and sufficient signal attenuation cannot be realized. .

  Therefore, a signal is input to the base of the transistor 802 even at a high frequency exceeding the cutoff frequency, the signal is transmitted to the output of the transistor 802 and the base of the transistor 803, and the output of the transistor 803 varies. For this reason, a potential drop at the bias point 820 occurs during a large signal operation. Therefore, it is said that it is difficult for the resistance bias feed circuit to obtain high linearity with respect to a wide range of input signals.

  Based on this, Non-Patent Document 1 proposes a dual bias feed circuit in which linearity is improved by combining two types of bias circuits 810 and 900 as shown in FIG. However, the dual bias feed circuit of Non-Patent Document 1 has a problem in terms of miniaturization because the circuit scale is double that of the resistance bias feed circuit. That is, since the circuit scale is increased by combining two types of circuits, there is a problem with miniaturization.

  The problem to be solved by the present invention is to improve the above-mentioned problems and without increasing the circuit scale, a high-frequency amplifier and a high-frequency module having high linearity with respect to a wide range of input signals, and a mobile radio using them Is to provide.

  An example of a representative one of the present invention is as follows. That is, the high-frequency amplifier according to the present invention includes a high-frequency signal input terminal and output terminal, a high-frequency amplification transistor having a base terminal connected to the input terminal, and a current mirror type that biases the base terminal of the high-frequency amplification transistor. A bias circuit is provided, and a low-pass filter including a capacitor is inserted in a feedback loop of the bias circuit, and the capacitor constitutes a part of a shunt circuit that grounds the feedback loop. And

  According to the present invention, there are provided a high-frequency amplifier and a high-frequency module that have high linear characteristics, are easy to integrate, and are resistant to fluctuations in transistor characteristics due to process variations, and a mobile radio using them without increasing the circuit scale. be able to.

According to an exemplary embodiment of the present invention, in a high-frequency amplifier having a bias circuit for biasing a high-frequency amplification transistor, the bias circuit includes a feedback circuit, and one end is grounded in the feedback loop of the feedback circuit. A circuit having a low-pass characteristic having a capacitance is inserted. As a result, no feedback is applied to the transistor 803 at a high frequency where the input signal exceeds the cutoff frequency, and a stable bias voltage is supplied to the high frequency amplification transistor, so that the linearity of the high frequency amplifier can be improved even when the input signal level increases. Can be improved.
Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a high-frequency amplifier according to a first embodiment of the present invention. The high-frequency amplifier of this embodiment includes an amplifying operation transistor (first transistor) 101 that amplifies and outputs an input signal, and a bias circuit 110 that supplies a bias voltage and a bias current to the amplifying operation transistor 101. The bias circuit 110 includes a (second) transistor 102 and a (third) transistor 103, a capacitor 104, a resistor 105, and a (first) resistor 106. The transistors 102 and 103 and the amplification operation transistor 101 form a current mirror circuit. Therefore, the circuit configuration is resistant to variations in transistor characteristics due to process variations.

The bias circuit 110 is a bias circuit that constitutes a current mirror circuit having a foot-back circuit with the amplifying operation transistor 101, and has a low-pass filter 111 having a capacitor 104 with one end directly grounded in the feedback loop. is doing. The capacitor 104 having one end directly grounded functions as a shunt circuit for the feedback loop. The value of the operating current of the amplifying operation transistor 101 is determined by the resistors 106 and 105.
In the embodiment shown in FIG. 1, the feedback loop is a connection from the emitter terminal of the transistor 103 to the base terminal of the transistor 102, a connection from the collector terminal of the transistor 102 to the base terminal of the transistor 103, and the transistor 102. And 103, and a feedback path of a bias circuit composed of the transistors 102 and 103.
That is, the high-frequency amplifier according to the present embodiment biases the base terminal of the high-frequency amplification transistor, the input terminal and the output terminal of the high-frequency signal, the high-frequency amplification transistor whose base terminal is connected to the input terminal, A bias circuit having a feedback loop that forms a current mirror circuit with a high-frequency amplification transistor is provided, and a low-pass filter including a capacitor is inserted in the feedback loop of the bias circuit, and the capacitor is connected to the feedback loop. At least a part of the shunt circuit for grounding. This also applies to other embodiments.

  The bias circuit 110 has a low-pass filter 111 having a capacitor 104 with one end directly grounded in the feedback loop, thereby sufficiently suppressing the feedback of the high-frequency signal and causing the transistor 103 to operate as a stable emitter follower with respect to the high frequency. Thus, the voltage at the bias point is kept constant.

A feature of the present invention is that a shunt circuit is formed by grounding one end of the capacitor 104.
In the embodiment of FIG. 1, the shunt circuit is constituted by the capacitor 104, but the capacitor 104 only needs to constitute at least a part of the shunt circuit that grounds the feedback loop.

FIG. 2 shows a large signal equivalent circuit of this embodiment. According to this embodiment, there is no resistance component in series with the capacitor 104 between the connection point of the capacitor 104 that is one end of the resistor 105 and the output end of the low-pass filter 111 and the ground. Therefore, during large signal operation, the output point of the low-pass filter 111 is sufficiently connected to the ground. Therefore, a bias current having a controlled potential can be supplied to the bias point 120 even during a large signal operation. As a result, the above-mentioned problems are solved and a stable bias is realized.
Note that the absence of a resistance component in series with the capacitor 104 means that there is no resistance element connected in series with the capacitor 104.

Note that if the cutoff frequency of the low-pass filter 111 is f _C , the lower limit of the optimum range of the cutoff frequency is f _L , and the upper limit is f _H , f _L is at least 2 to 3 times the modulation frequency band of the high frequency input signal. , F _H is preferably designed to be equal to or lower than the frequency of the high-frequency input signal.

As an example, if the wireless LAN 11a standard using the OFDM system is taken as an example, f _H is a frequency in the 5 GHz band. In 11a, the modulation band is about 20 MHz, and f _L is 40 MHz to 60 MHz.
That is, f _L may be at least twice (40 MHz or more), more preferably three times (60 MHz or more) of the modulation frequency band of the high-frequency input signal.

That is, in the low-pass filter 111 constituted by the capacitor 104 and the resistor 105, the gain characteristic can be controlled and high linearization can be realized by appropriately adjusting the cutoff frequency f _C in the range from f _{L to} f _H.

Thus, according to this embodiment, one end of the low-pass filter 111 in the foot back loop of the bias circuit 110 is directly grounded via the shunt circuit, so that the signal attenuation is sufficient in the high frequency band of the input signal. Since it is large and no feedback is applied, the base of the transistor 102 is stabilized in a DC manner. Therefore, the transistor 103 is in a stable emitter follower operation state, and a constant voltage bias operation is realized. In particular, during a large signal operation in which the input signal becomes large, when the amplitude of the input swings in the positive direction, the transistor 103 is turned off and becomes high impedance. Is obtained. Conversely, when the amplitude fluctuates in the negative direction, the transistor 103 looks like an emitter follower circuit, and is maintained at a constant voltage. Can be realized.

  As an example, an analog signal of a digital modulation scheme based on the OFDM scheme has an average value of 18 dB in the wireless LAN 11a, whereas its peak value reaches 26 dB. Even with such a large amplitude and high frequency analog input signal, the high frequency amplifier of the present invention can amplify with high linearity. Also, the third harmonic distortion is small.

FIG. 3 shows a bias point 120 with respect to the magnitude of each input signal when there is no shunt circuit including the capacitor 104 in the embodiment of FIG. 1 and when the cutoff frequency of the low-pass filter is changed by changing the capacitance value of the shunt circuit. This is a result of confirming the relationship between the voltage Vbias and the gain in the simulation. It can be seen that having the low-pass filter composed of a capacitor with one end grounded in the feedback loop suppresses the potential drop of the voltage Vbias at the bias point 120 with respect to the increase in the input signal. It can also be confirmed that there is an effect of increasing the voltage Vbias depending on the condition of the cutoff frequency of the low-pass filter.
Further, the range in which the capacitance 104 in FIG. 3 is changed is 2 to 10 pF, and the resistance 105 is 100Ω. Each graph line related to the bias circuit with a low-pass filter in FIG. 3 corresponds to the case where the capacitance values are 2 pF, 3 pF, 6 pF, and 10 pF from the bottom as viewed on the right side of the drawing. At this time, the voltage change of the bias point (output voltage of the bias circuit) when the input signal is changed from −10 dBm to +17 dBm can be made 35 mV or less. Further, when the capacitance value of the shunt circuit is in the range of 3 to 10 pF, the voltage change is 15 mV or less. The high-frequency input signal at this time is a signal in the 5 GHz band (frequency band used in 11a), and the cut-off frequency change range of the low-pass filter is about 150 MHz to 800 MHz. It can also be confirmed that there is an effect of increasing the voltage Vbias depending on the condition of the cutoff frequency of the low-pass filter (for example, the capacitance value of the shunt circuit is 6 pF or more).

Furthermore, by properly setting the cut-off frequency in the range of f _L or more and f _H or less, as can be seen from FIG. 4, the gain characteristic for the input signal can be controlled.

That is, as can be seen from FIG. 4, the gain reduction is reduced with respect to the gain, and high linearity is realized. It can also be confirmed that there is an effect of increasing the gain depending on the condition of the cutoff frequency of the low-pass filter.
Further, the range in which the capacitance 104 in FIG. 4 is changed is 2 to 10 pF, and the resistance 105 is 100Ω. Each graph line related to the bias circuit with a low-pass filter in FIG. 3 corresponds to the case where the capacitance values are 2 pF, 3 pF, 6 pF, and 10 pF from the bottom as viewed on the right side of the drawing. At this time, by changing the voltage change of the bias point (the output voltage of the bias circuit) when the input signal is changed from −10 dBm to +17 dBm to 35 mV or less, the gain when the input signal is changed from −10 dBm to +17 dBm The change can be 1 dB or less. Further, it can be confirmed that there is an effect of increasing the gain depending on the condition of the cutoff frequency of the low-pass filter (for example, the capacitance value of the shunt circuit is 6 pF or more).

  Further, when the high frequency signal touches the positive side, the transistor 103 is turned off, and the impedance on the bias side becomes high, and leakage of the high frequency signal to the bias circuit side is suppressed.

  According to the present embodiment, the above configuration realizes a high frequency amplifier having a small circuit scale and high linear characteristics.

  As described above, the high-frequency amplifier according to the present invention can realize high linearity in one stage and can control increase and decrease in gain with respect to an increase in input signal. Therefore, it is possible to improve the linearity as a whole by connecting two or more high-frequency amplifiers of the present invention.

  According to the present embodiment, it is possible to provide a high-frequency amplifier and a high-frequency module that are easy to integrate, have a small circuit scale, and have high linearity for a wide range of input signals without increasing the circuit scale. it can.

  The low-pass filter of the first embodiment is configured by using the base input capacitor 130 of the transistor 102 instead of the capacitor 104, and the same effect can be obtained. Similar to the parasitic capacitance of the transistor, the same effect can be obtained by connecting one end of the capacitor 104 to the emitter of the transistor 102 instead of the ground.

FIG. 5 is a diagram showing a second embodiment of the present invention. The basic configuration is the same as that of the first embodiment, and is a high-frequency amplifier including a bias circuit 110 including an amplification operation transistor 101, transistors 102 and 103, and resistors 105 and 106.
Since the amplifying operation transistor 101 and the transistors 102 and 103 constitute a current mirror circuit, the circuit configuration is resistant to variations in transistor characteristics due to process variations. The bias current of the amplifying operation transistor 101 is determined by the resistors 106 and 105. In addition, by configuring the low-pass filter with the resistor 105 and the base input capacitance 130 of the transistor 102, it is possible to eliminate the need for a capacitive element and realize further circuit miniaturization. Further, the parallel connection circuit of the resistor 107 and the capacitor 108 is an example of a ballast circuit that prevents thermal runaway of the transistor 101, and the same effect is exhibited even when used in the first embodiment.
The ballast circuit is connected between the emitter terminal of the third transistor and the base terminal of the first transistor, and is connected between the input terminal and the base terminal of the first transistor. This also applies to the embodiments described later.
Further, the relationship between the base input capacitance 130 and the parasitic capacitance of the transistor will be specifically described. The main parasitic capacitance as the base input capacitance 130 is a base-emitter parasitic capacitance between the base and the emitter, and the parasitic capacitance of the transistor. Is the base-emitter parasitic capacitance. Further, the input capacitance of a transistor practically used as the transistor 102 is about several tens of fF to several hundreds of fF, and the cutoff frequency changed in FIG. 3 is obtained by setting the resistance 105 to a value of several kΩ to several hundred kΩ. Can be realized.

  As described above, according to the present embodiment, a high-frequency amplifier and a high-frequency module that can be easily integrated without increasing the circuit scale, are small in circuit scale, and have high linearity with respect to a wide range of input signals. Can be provided.

FIG. 6 is a diagram showing a third embodiment of the present invention. In this embodiment, one end of the resistor 106 is grounded via a capacitor 109. In addition, a (second) resistor 107 that connects the emitter terminal of the transistor 103 and the base terminal of the transistor 101, a (third) resistor 113 that connects the input terminal and the emitter terminal of the transistor 103, and an input terminal The emitter terminal of the third transistor 103 and the base terminal of the first transistor 101 are connected by a ballast circuit including a capacitor 108 that connects the base terminal of the first transistor 101.
The ballast circuit including the resistors 107 and 113 and the capacitor 108 illustrated in FIG. 6 is compared with the ballast circuit including the resistor 107 and the capacitor 108 illustrated in FIG. By separating from the signal path of the high-frequency signal, it is possible to realize a higher impedance for the high-frequency signal, and to reduce the attenuation of the high-frequency signal in the ballast circuit.

In this embodiment, a second low-pass filter 112 including a resistor 106 and a capacitor 109 is further added to the feedback loop by adding a capacitor 109 having one end grounded to the bias circuit of the first embodiment. Thereby, the high frequency signal can be further attenuated, and the emitter follower operation of the transistor 103 can be made more stable. Further, the circuit constituted by the resistors 107 and 113 and the capacitor 108 is another example of the ballast circuit shown in the second embodiment. Similarly, when applied to other embodiments, the transistor 101 is prevented from thermal runaway. effective.
Further, the resistor 106 and the capacitor 109 constituting the second low-pass filter are connected to the collector terminal of the transistor 102. Here, a high frequency signal is transmitted as a current signal from the collector terminal of the transistor 102. The second low-pass filter operates as a low-pass filter included in the feedback loop of the bias circuit 110 having the feedback loop.

  As described above, according to the present embodiment, a high-frequency amplifier and a high-frequency module that can be easily integrated without increasing the circuit scale, are small in circuit scale, and have high linearity with respect to a wide range of input signals. Can be provided.

FIG. 7 is a diagram showing a fourth embodiment of the present invention. In this embodiment, the feedback loop includes a plurality of low-pass filters including a capacitor 104 and a resistor 105, and a capacitor 140 and a resistor 141. Further, a resistor 107 that connects the emitter terminal of the transistor 103 and the base terminal of the transistor 101, and a resistor 113 that connects the input terminal and the emitter terminal of the transistor 103 are provided. Further, an emitter terminal of the transistor 103 and the transistor 1 are formed by a ballast circuit including a (fourth) resistor 114 connected to the input terminal and the base terminal of the first transistor 101 and a capacitor 108 connected in parallel to the resistor 114.
01 base terminal is connected. That is, the capacitor 104 and the resistor 105 constituting the low-pass filter 111 of the bias circuit of the first embodiment are added to the capacitor 140 and the resistor 141 to form a two-stage low-pass filter. Similar to the third embodiment, this is another embodiment in which the high frequency signal is further attenuated to stabilize the emitter follower operation of the transistor 103. Further, the circuit composed of the resistors 107, 113 and 114 and the capacitor 108 is an example of a ballast circuit having the same effect as in the second and third embodiments.

As described above, according to the present embodiment, a high-frequency amplifier and a high-frequency module that can be easily integrated without increasing the circuit scale, are small in circuit scale, and have high linearity with respect to a wide range of input signals. Can be provided.
Note that a resistor 141 can be connected instead of the capacitor 140 and the resistor 141 constituting a one-stage low-pass filter circuit of the two-stage low-pass filter shown in FIG. By adjusting the resistance value of the resistor 141 connected between the one-stage low-pass filter configured using the capacitor 104 and the resistor 105 and the base terminal of the transistor 102, the cutoff frequency of the resistor 106 and the low-pass filter can be adjusted. The bias current flowing through the high frequency amplification transistor 101 can be adjusted without changing the value of the resistor 105 to be determined, and the degree of freedom in designing the bias circuit can be increased.

FIG. 8 shows a fifth embodiment of the present invention. As the low-pass filter 111 of the bias circuit in each of the embodiments described above, an inductor 118 may be added in addition to the capacitor 104. The inductor 118 may be formed using a back via or a wire bond of an IC circuit. As an example, the capacitance is 100 pH or less, and the inductor is 1 nH or less.
In the embodiment shown in FIG. 8, the configuration is simplified by grounding the emitter of the transistor 102 and the capacitor 104 via the common inductor 118. The capacitor 104 and the emitter of the transistor 102 can be grounded via separate inductors. Further, only the capacitor 104 can be grounded via the inductor.

Thus, by providing a filter having a low-pass characteristic with a shunt circuit having a low impedance at the communication frequency in the feedback loop of the feedback circuit, it has a high linear characteristic without increasing the circuit scale, It is possible to provide a high-frequency amplifier that can be easily integrated and is resistant to variations in transistor characteristics due to process variations.

  FIG. 9 is a diagram showing the configuration of a high-frequency amplifier according to the seventh embodiment of the present invention. The high frequency amplifier 1310 of the present embodiment is realized by using the MOS transistor with the same configuration as the high frequency amplifier of the first embodiment. That is, the transistors 1301 to 1303 have a MOS structure, and the operation and effect obtained by providing the low-pass filter 1311 are the same as those in the first embodiment.

  By mounting and incorporating a semiconductor IC based on the high-frequency power amplifier and high-frequency low-noise amplifier of the present invention, a high-frequency switch, and a filter function on a multilayer dielectric substrate to form a high-frequency module, it is possible to reduce the size of communication equipment.

  FIG. 11 is a functional block diagram showing a configuration example of a mobile radio device including a high frequency module according to the seventh embodiment of the present invention.

The high-frequency module 1201 includes a high-frequency power amplifier 1202, a high-frequency low-noise amplifier 1203, a filter 1205, and a high-frequency switch 1204, which are mounted on a single multilayer dielectric substrate and modularized. The high frequency switch 1204 is connected to an external antenna 1208 by switching between a signal transmission path and a reception path.
This will be specifically described below. The high-frequency module 1201 is a module for performing wireless communication using a frequency-multiplex modulation type radio wave. The high-frequency power amplifier 1202 and the high-frequency low-noise amplifier 1203 are high-frequency amplifiers that amplify the signal on the transmission path and the signal on the reception path, respectively. The high-frequency switch 1204 is connected to the external antenna 1204 through a transmission / reception path, and the signal path is changed by switching between the transmission path and the reception path.
FIG. 16 shows a perspective view of such a high-frequency module. IC chips of a high frequency power amplifier 1202, a high frequency low noise amplifier 1203, and a high frequency switch 1204 are mounted on the surface of the multilayer dielectric substrate 1209, and the filter 1205 is configured inside the multilayer dielectric substrate. The filter 1205 removes unnecessary spectrum and interference waves from the transmission signal. On the back side of the multilayer dielectric substrate are provided an antenna terminal for connecting the transmission / reception path of the high-frequency switch to an external antenna, a transmission terminal for inputting a signal of the transmission path, a reception terminal for outputting a signal of the reception path, etc. It has been. As the multilayer dielectric substrate, for example, a ceramic substrate or a resin substrate is used. Further, a part of the high-frequency amplifier that amplifies the signal on the transmission path or the signal on the reception path may be disposed on a portion other than the multilayer dielectric substrate that constitutes the high-frequency module.
The configuration of the high-frequency module is not limited to that shown in FIG. That is, a high-frequency switch that switches between a transmission path and a reception path, and at least one high-frequency amplifier that amplifies a high-frequency signal in the transmission path or a high-frequency signal in the reception path, and wirelessly using radio waves of a frequency multiplex modulation method A high-frequency module for performing communication can be used. The configuration according to the above-described embodiment is used for such a high-frequency amplifier. A high-frequency module for multiband communication can also be configured by providing a branching circuit in the transmission path and reception path in the subsequent stage of the high-frequency switch (on the side opposite to the external antenna side). In such a case, the high-frequency amplifier according to the present invention can be used for each communication band.
The mobile radio shown in FIG. 11 has a high frequency module and an antenna, and the high frequency module includes a transmission unit including a high frequency power amplifier and a modulation unit, a reception unit including a high frequency low noise amplifier and a demodulation unit, and a high frequency switch. The high frequency power amplifier and the high frequency low noise amplifier each include at least one high frequency analog amplifier. The high frequency power amplifier 1202 of the transmission unit and the high frequency low noise amplifier 1203 of the reception unit are provided in the high frequency module 1201. On the other hand, the modulation unit and the demodulation unit are configured in the RF-IC 1206, and the RF-IC 1206 is connected to the baseband IC 1207.

The mobile radio apparatus according to the present embodiment has a function of performing wireless communication using radio waves of a frequency multiplex modulation system that employs a CDMA system, an OFDM system, or an extended system thereof. The high-frequency module 1201 constitutes the analog front end unit of the radio, and the high-frequency power amplifier 1202 and the high-frequency low-noise amplifier 1203 are key blocks in the analog front-end unit, and are amplifiers that amplify the high-frequency analog signal. The amplifier according to any of the embodiments of the present invention is used.
In particular, the high-frequency amplifier according to the present invention is preferably used as a high-frequency power amplifier that amplifies a transmission signal.
The mobile radio apparatus according to the present invention is not limited to the configuration shown in FIG. That is, according to the present invention, a mobile radio for performing radio communication using radio waves of a frequency multiplex modulation scheme includes a high-frequency switch that switches between a transmission path and a reception path, and a high-frequency signal on the transmission path or the reception It suffices to have a high-frequency module including at least one high-frequency amplifier that amplifies the high-frequency signal on the path, a high-frequency signal modulator, a high-frequency signal demodulator, and an antenna. The above-described configuration according to the present invention is applied to such a high-frequency amplifier. Examples of the mobile wireless device according to the present invention include a mobile phone and a personal computer, but are not limited thereto.

  According to the present embodiment, it is possible to provide a high-frequency module having a small circuit scale and a mobile radio using the same because it has high linearity over a wide range of input signals and is easily integrated.

It is a figure which shows the structure of the high frequency amplifier which becomes the 1st Example of this invention. FIG. 3 is a diagram illustrating a large signal equivalent circuit according to the first embodiment. It is a figure which shows the dependence of voltage Vias [V] with respect to input electric power [dBm] of Example 1. FIG. FIG. 3 is a diagram illustrating a gain [dB] characteristic with respect to input power [dBm] according to the first embodiment. It is a figure which shows the structure of the high frequency amplifier which becomes the 2nd Example of this invention. It is a figure which shows the structure of the high frequency amplifier which becomes the 3rd Example of this invention. It is a figure which shows the structure of the high frequency amplifier which becomes the 4th Example of this invention. It is a figure which shows the structure of the high frequency amplifier which becomes the 5th Example of this invention. It is a figure which shows the structure of the high frequency amplifier which becomes the 6th Example of this invention. It is a figure which shows an example of the time fluctuation | variation of the high frequency signal power of OFDM system. It is a functional block diagram which shows one structural example of the mobile radio | wireless machine provided with the high frequency module which becomes the 7th Example of this invention. It is a figure which shows the inductor bias feed circuit used as a prior art example. It is a figure which shows the resistance bias feed circuit used as a prior art example. It is a figure which shows the dual bias feed circuit used as a prior art example. It is an equivalent circuit diagram at the time of large signal operation of the conventional example of FIG. It is a perspective view which shows one Example of the high frequency module which concerns on this invention.

Explanation of symbols

101-103 ... transistor, 104 ... capacitor, 105-107 ... resistor, 108-109 ...
Capacitance 110 ... Bias circuit 111-112 ... Low pass filter 113-114 ... Resistance 118 ... Inductor 120 ... Bias point 130 ... Transistor input capacitance 701-703 ... Transistor 704 ... On-chip inductor 705 ... Resistor, 801-803 ... Transistor, 804 ... Capacitor, 805-808 ... Resistor, 830-831 ... Matching circuit, 901-903 ... Transistor, 904 ... Resistor, 1101-1103 ... Transistor large signal model, 2801-2803 ... Transistor 1201... High-frequency module, 1202-1203... High-frequency amplifier IC using the present invention, 1204.

Claims (20)

High-frequency signal input and output terminals;
A high-frequency amplification transistor having a base terminal connected to the input terminal;
Comprising a current mirror type bias circuit for biasing the base terminal of the high frequency amplification transistor;
A low-pass filter including a capacitor is inserted in the feedback loop of the bias circuit,
The high frequency amplifier according to claim 1, wherein the capacitor constitutes a part of a shunt circuit that grounds the feedback loop. In claim 1,
One end of the capacitor is directly grounded. In claim 1,
One end of the capacitor is grounded via an inductor. In claim 1,
The high-frequency amplifier according to claim 1, wherein the capacitor is a base input capacitor of a transistor constituting a part of the feedback loop. In claim 1,
The high-frequency amplifier, wherein the feedback loop includes a plurality of the low-pass filters. In claim 1,
The first mirror functioning as the high-frequency amplification transistor, the second transistor, and the third transistor constitute the current mirror type bias circuit,
Comprising a first resistor connected between a control voltage or power supply and the feedback loop and having a function of determining a bias current of the bias circuit;
The second transistor has a collector terminal connected to one end of the first resistor, an emitter terminal grounded,
A base terminal of the third transistor is connected to one end of the first resistor;
The feedback loop is configured to pass from the emitter terminal of the third transistor through the base terminal and collector terminal of the second transistor and connect the base terminal of the third transistor. . In claim 6,
The high-frequency amplifier having the low-pass filter including at least one capacitor having one end connected to the ground or the emitter terminal of the second transistor in the feedback loop. In claim 6,
A high frequency amplifier comprising an inductor having one end grounded and the other end connected to the capacitor. In claim 6,
A collector of the first transistor is connected to the output terminal, and an emitter terminal of the third transistor and a base terminal of the first transistor are connected. In claim 7,
The first transistor has a collector connected to the output terminal, and at least one of a connection point connecting the emitter terminal and the input terminal of the third transistor and a base terminal of the first transistor. A high-frequency amplifier, wherein the resistor and one or more capacitors are connected by a ballast circuit connected in parallel. In claim 9,
A second resistor connecting the emitter terminal of the third transistor and the base terminal of the first transistor; a third resistor connecting the input terminal and the emitter terminal of the third transistor; and The high frequency device characterized in that the emitter terminal of the third transistor and the base terminal of the first transistor are connected by a ballast circuit comprising a capacitor connecting the input terminal and the base terminal of the first transistor. amplifier. In claim 9,
A second resistor connecting the emitter terminal of the third transistor and the base terminal of the first transistor;
A third resistor connecting the input terminal and the emitter terminal of the third transistor;
The ballast circuit including a fourth resistor connected to the input terminal and the base terminal of the first transistor and a capacitor connected in parallel to the fourth resistor, the emitter terminal of the third transistor and the first transistor A high frequency amplifier characterized in that the base terminal of a transistor is connected. In claim 1,
A high-frequency amplifier, wherein the first transistor constituting the high-frequency amplification transistor, the second transistor and the third transistor constituting the feedback loop are each constituted by a MOS transistor. It has a high frequency amplifier and a high frequency switch,
It has a function to perform wireless communication using radio waves of frequency multiplex modulation system,
The high-frequency amplifier includes a high-frequency signal input terminal and an output terminal;
A high-frequency amplification transistor having a base terminal connected to the input terminal;
Comprising a current mirror type bias circuit bias circuit for biasing the base terminal of the high-frequency amplification transistor;
A high-frequency module comprising a low-pass filter having a shunt circuit inserted in a feedback loop of the bias circuit and having a low impedance at a communication frequency used for the wireless communication. In claim 14,
The shunt circuit has a capacitor with one end grounded. In claim 14,
The high-frequency module according to claim 1, wherein the shunt circuit has a capacitor having one end grounded via an inductor. In claim 14,
The frequency multiplexing modulation scheme is an OFDM modulation scheme;
A high-frequency module, wherein the high-frequency amplifier is mounted on a multilayer dielectric substrate and modularized. It has a high-frequency module and an antenna, and has a function of performing wireless communication using radio waves of a frequency multiplex modulation method.
The high-frequency module includes a transmitter unit including a high-frequency power amplifier and a modulation unit, a reception unit including a high-frequency low-noise amplifier and a demodulation unit, and a high-frequency switch.
The high-frequency power amplifier and the high-frequency low-noise amplifier each include at least one high-frequency analog amplifier,
The high-frequency analog amplifier includes a high-frequency signal input terminal and an output terminal;
A high-frequency amplification transistor having a base terminal connected to the input terminal;
Comprising a current mirror type bias circuit for biasing the base terminal of the high frequency amplification transistor;
A mobile radio apparatus comprising a low-pass filter having a shunt circuit inserted in a feedback loop of the bias circuit and having a low impedance at a communication frequency used for the radio communication. In claim 18,
The frequency multiplexing modulation scheme is an OFDM modulation scheme;
A mobile radio device comprising the high-frequency module mounted on a multilayer dielectric substrate and modularized. In claim 18,
The low pass filter includes a capacitance;
The mobile radio apparatus according to claim 1, wherein the capacitor constitutes a part of the shunt circuit for grounding the feedback loop.

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