JPH0534732U - Transmitter - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object to provide a transmitter which can be downsized and reduced in cost. [Structure] A digital modulation unit and 103 that perform modulation in which the envelope of a high-frequency signal fluctuates, an analog modulation unit 104 that performs modulation in which the envelope of a high-frequency signal is constant, and a digital modulation unit 103 and an analog modulation unit 104. A control unit 300 for selection, a digital modulation unit 103, and a power amplification unit 106 that performs power amplification on a high frequency signal modulated by a modulation unit selected by the control unit 300 among the analog modulation units 104, Analog modulator 10
When 4 is selected and the output level of the power amplification unit 106 is maximized, the power amplification unit 106 is subjected to saturation amplification, and in other cases linear amplification is performed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a wireless communication device, and more particularly to a transmitter of a wireless communication device used in a mobile communication system.

[0002]

[Prior Art]

 Mobile radio communication devices such as mobile phones, car phones, and cordless phones employ analog communication systems modulated by the FM (frequency modulation) method. As the use of radio waves increases in this way, how to efficiently carry out many communications within a limited frequency band becomes a problem. Recently, there is a concern that the secret of communication may be leaked when a third party intercepts the communication. Further, in the wireless communication of the mobile body as described above, unlike the communication of fixed stations, the communication line is required to be highly stable because the transmission line fluctuates. Considering such circumstances, it is necessary to shift to digital modulation.

In the transition period from an analog communication system using such a narrow band FM modulation / demodulation system to a digital communication system which is a new technology, a system that can communicate with either system is being studied. There are various types of digital modulation / demodulation systems, but from the viewpoints of frequency utilization efficiency, anti-fading, etc., π / 4 shift QPSK (quadrature phase shift keying), which is a kind of quadrature amplitude modulation, is adopted.

In the cellular type mobile telephone, automatic power control is performed to control the transmission output level to be constant in order to stabilize communication and reduce unnecessary power consumption. However, in the above-mentioned quadrature amplitude modulation such as π / 4 shift QPSK, the envelope of the modulated carrier wave fluctuates depending on the modulation signal, so it is necessary to perform linear amplification in power amplification. On the other hand, in the FM system, since the envelope of the carrier wave is constant regardless of the modulation signal, it is customary to perform saturation amplification with high power conversion efficiency.

As described above, in the transmission power amplification circuit of the system in which the analog FM system and the digital modulation system are mixedly operated, the class C operation (saturation amplification) is performed during analog FM, and the class AB operation (linear amplification is performed during digital modulation). ) Switch the operating state of the power amplifier. The automatic power control in this case is performed as follows.

That is, in class AB operation, the output level is controlled by varying the high-frequency signal input level to the power amplifier without changing the DC bias condition of the power amplifier to ensure linearity. On the other hand, in class C operation, the bias voltage of the power amplifier is controlled. This is because the power amplifier of class C operation becomes unstable as the input signal is made smaller, and therefore, when the set output level is made small, it is possible to prevent the occurrence of defects such as abnormal oscillation.

FIG. 5 is a block diagram showing the configuration of such a conventional power amplifier.

In the figure, reference numeral 1 is a variable attenuator for attenuating a modulated carrier wave. The modulated carrier wave attenuated by the variable attenuator 1 is power-amplified by the power amplifier 2, passes through the branch circuit 3, and is radiated into the air as a radio wave from the antenna. On the other hand, a part of the modulated carrier wave output from the power amplifier 2 becomes a DC voltage Vd according to the signal level of the modulated carrier wave by the detection circuit 4 and the smoothing circuit 5. In the case of transmission by the digital modulation method, the error amplifier 6a compares the reference voltage Vra with the DC voltage Vd, and the attenuation level of the variable attenuator is controlled by the signal according to the comparison result. In the case of the analog-FM FM transmission, the error amplifier 6b compares the reference voltage Vrb with the DC voltage Vd, and outputs a signal by controlling the bias voltage of the power amplifier 2 with a signal according to the comparison result. The level is controlled.

However, in this case, two systems of comparison circuits using the error amplifier are required, which causes a problem that the circuit scale becomes large and the cost becomes high.

[0010]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, in automatic power control of a transmitter capable of modulating a carrier wave by two modulation methods of digital quadrature amplitude modulation and analog FM modulation, two systems of comparison control circuits are required. Therefore, it has been an obstacle to miniaturization and cost reduction.

The present invention was created in view of such circumstances, and an object of the present invention is to provide a transmission device that can be reduced in size and cost.

[0012]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the first invention is a first modulation means for performing a first modulation in which the envelope of a high frequency signal varies, and a second modulation for performing a modulation in which the envelope of a high frequency signal is constant. Means, a selecting means for selecting the first modulating means and the second modulating means, and a modulating means selected by the selecting means from the first modulating means and the second modulating means. When the power amplifying means for amplifying the power of the high frequency signal modulated by the above and the second modulating means by the selecting means are selected, and the output level of the power amplifying means becomes maximum. And a control means for controlling the power amplification means so as to perform saturation amplification of the power amplification means and linearly amplify the power amplification means in other cases. A second invention is the first invention. , The power amplification means Attenuating means for attenuating the input signal, output level detecting means for detecting the output level of the power amplifying means, and generating an output level voltage corresponding to the output level, and output level detecting means for generating the output level voltage. Comparing means for comparing the output level voltage with a predetermined reference voltage to generate a voltage difference signal corresponding to the difference between these voltages; and a damping means for damping the attenuating means based on the voltage difference signal generated by the comparing means. A transmission device further comprising attenuation level control means for controlling the amount, and a third invention is a transmission device used for communication between a base station and a mobile body in the first and second inventions. The output level of the power amplification means is a transmission device that is the transmission power signal requested by the base station.

[0013]

[Action]

 In the present invention, the high frequency power amplifier is saturated and amplified when the output level of the modulated high frequency signal having a constant envelope is maximized, and is linearly amplified in other cases.

[0014]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an embodiment when the present invention is applied to a wireless telephone device.

As shown in the figure, this radio telephone device includes a transmission system 100, a reception system 200, a control unit 300 for controlling the transmission system 100 and the reception system 200, and a local oscillation in the transmission system 100 and the reception system 200. It is composed of a PLL synthesizer 400 for supplying a high frequency signal, an antenna 500, and a duplexer 600.

The transmission system 100 includes a microphone 101 for converting a sound wave into an electric signal, and an electric signal converted by the microphone 101 is amplified to a predetermined level and subjected to a filtering process or converted into a digital signal for encoding. A transmission signal processing unit 102, a digital modulation unit 103 that modulates a digital signal, an analog modulation unit 104 that modulates an analog signal, and a non-modulation carrier wave modulated by the digital modulation unit 103 and the analog modulation unit 104. The mixer 105 includes a mixer 105 that mixes high-frequency signals from the PLL synthesizer 400 and converts the signals into a transmission frequency, and a power amplification unit 106 that amplifies the power of the signal output from the mixer 105.

The reception system 200 includes a high frequency amplification unit 201 that selects a band of a high frequency signal to be received and performs high frequency amplification, a reception signal that is high frequency amplified by the high frequency amplification unit 201, and a high frequency signal from the PLL synthesizer 400. A mixer 202 that mixes and frequency-converts, a digital demodulator 203 that demodulates a digitally modulated reception signal, an analog demodulator 204 that demodulates an analog-modulated reception signal, and a digital demodulation unit 203. The reception signal processing unit 205 reproduces the audio signal and the control signal by decoding the encoded data and the encoded control data, and the speaker 206 that outputs the audio signal reproduced by the reception signal processing unit 205 as a sound wave. ing . The control unit 300 has a microcomputer as a main control circuit and controls connection of a wireless line. Further, the control unit 300 selectively selects the digital modulation unit 103 and the analog modulation unit 104 for the transmission system 100, controls the bias voltage application of the power amplifier 106, and controls the digital signal for the reception system 200. Control is performed to selectively select the demodulator 203 and the analog demodulator 204. Further, the control unit 300 controls the oscillation frequency of the PLL synthesizer 400 to set a communication channel such as MCA (multi channel acess).

FIG. 2 is a block diagram showing the configuration of the power amplification unit 106.

As shown in the figure, the power amplification unit 106 includes a variable attenuator 701 that attenuates an input signal, a power amplification circuit 702 that performs power amplification of a high frequency signal attenuated by the variable attenuator 701, A branch circuit 703 including a directional coupler that branches the high-frequency signal power-amplified by the power amplifier circuit 702, and a Schottky barrier diode that detects the high-frequency signal branched by the branch circuit 703. The configured detection circuit 704, a smoothing circuit 705 that removes high-frequency components of the signal detected by the detection circuit 704 to perform smoothing, a DC voltage output from the smoothing circuit 705, and a voltage Vref determined by the control unit 300. Of the error amplifier 707 that outputs a voltage according to the comparison result by comparing with the reference power source 706 of And a sample-and-hold circuit 708 that controls the attenuation level of the variable attenuator 701 a voltage sample and hold to.

Next, the operation of the power amplification unit 106 will be described.

First, the operation in the digital modulation mode will be described.

In this case, since it is necessary to perform linear amplification, a signal designating class AB operation is applied from the control unit 300 to the operation mode switching terminal 702 a of the power amplification circuit 702. Further, the reference voltage 706 is set to a voltage value corresponding to the output level according to the setting command requested by the base station according to the instruction of the control circuit 300. A part of the high frequency signal output from the power amplifier 702 is branched by the branch circuit 703, and a part of this high frequency signal is converted into a DC voltage by passing through the detection circuit 704 and the smoothing circuit 705. That is, the DC voltage Vd output from the smoothing circuit 705 indicates the level of the high frequency signal output. Then, the DC voltage Vd output from the smoothing circuit 705 is compared with the reference voltage Vref, and a signal of a voltage Ve corresponding to this voltage difference is output. The signal of this voltage Ve is input to the sample & hold circuit 708. Then, during burst transmission, the control signal of the control unit 300 is applied to the input terminal so that the sampling state is set when transmission is turned on and the hold state is set when transmission is turned off. The signal output from the sample & hold circuit 708 is input to the variable attenuator 701 and the attenuation level is adjusted. In this way, the constant high frequency output level indicated by the reference voltage Vref is controlled. In this case, since the DC bias condition of the power amplifier circuit 702 is not changed at all, the linearity is not particularly deteriorated. If burst transmission is not necessary, the sample & hold circuit 708 is not always necessary.

Next, the operation in the analog modulation mode will be described.

First, a case where there is a request from the base station to transmit with the maximum power will be described.

In this case, the control circuit 300 sets the reference voltage Vref to the maximum value. Then, the control circuit 300 applies a signal designating class C operation to the operation mode switching terminal 702a. At this time, the attenuation level of the variable attenuator 701 becomes the minimum, and a sufficient level is input to the power amplifier 702. Therefore, the operation of the power amplifier circuit 702 becomes stable. Therefore, the power conversion efficiency is improved.

Next, a case will be described in which there is a request from the base station for transmission with power that is not maximum.

In this case, the control circuit 300 sets the reference voltage Vref to a value that is not the maximum. Then, the control circuit 300 applies a signal designating class AB operation to the operation mode switching terminal 702a. Then, the same operation as in the digital modulation mode described above is executed. However, the sample and hold circuit 708 applies a control signal to the control terminal 708a so that the sample and hold circuit 708 is always in the sampling state. If controlled in this way, the operation of the power amplification circuit 702 is class AB. Therefore, even if the attenuation amount of the variable attenuator 701 is increased to reduce the input level to the power amplification circuit 702, an unstable operation such as abnormal oscillation is generated. I can't see it.

FIG. 3 is a circuit diagram showing the configuration of the power amplification circuit 702 of the power amplification unit 106.

In the figure, Q indicates a final-stage transistor. An inductor L1 and a capacitor C1 for impedance matching on the input side are connected to the base of the transistor Q 1. A coupling capacitor C2 for coupling is connected to the input side of the inductor L1. Resistors R1 and R2 for base bias are connected to the base of the transistor Q via a high frequency cheek coil RFC. An anode side of a diode D1 for temperature compensation is connected to a connection point P1 between the resistors R1 and R2. The cathode side of the diode D1 is grounded. The capacitor C3 is for removing the AC component. A switch SW controlled by the control unit 300 is connected to the connection point P1, and the switch SW turns on / off the base bias voltage VB. The collector voltage Vc is applied to the collector of the transistor Q via the inductor L3. The capacitor 4 is for removing high frequency components. Further, an impedance matching circuit composed of a capacitor C5, an inductor L4, a capacitor C6, an inductor L5 and a capacitor C7 is connected to the collector of the transistor Q.

Next, the operation of the above-described power amplification circuit 702 will be described.

The high frequency signal output from the variable attenuator 701 is subjected to impedance matching through a coupling capacitor C2 and an impedance matching circuit including an inductor L1 and a capacitor C1. The power of the high frequency signal is amplified by the transistor Q, and impedance matching is performed by an impedance matching circuit including a capacitor C5, an inductor L4, a capacitor C6, an inductor L5, and a capacitor C7. Then, the power-amplified high-frequency signal is supplied to the duplexer 600 and the antenna 500 and transmitted as a radio wave.

When a signal instructing a class C operation is sent from the control section 300 to the operation mode switching terminal 702a, the switch SW is turned on, a bias voltage is applied, and the transistor Q operates as saturation amplification. Further, when a signal instructing a class AB operation is sent from the control section 300 to the operation mode switching terminal 702a, the switch SW is turned off and the transistor Q operates as a linear amplifier.

Next, attention is paid to the current consumption when the transistor Q is operated in the class AB.

FIG. 4 is a graph showing the relationship between the input level and the collector current when the transistor Q operates in class AB.

In the figure, G1 indicates a collector current and G2 indicates an output level.

Generally, in the class AB power amplifier 702, the collector current is constant at an input level of an extremely small signal, but as shown in the figure, when a signal of a certain level or more is input, the collector current increases. When the maximum output level in digital modulation mode (point A in the figure) is small in analog FM (point B in the figure), the collector current decreases by ΔI. Therefore, even when operated in class AB, the collector current does not extremely increase as compared with the conventional class C operation PA.

As described above, in the high frequency power amplifier circuit of the present embodiment, when the operation of the power amplifier 702 is switched to the class AB operation (linear amplification) and the class C operation (saturation amplification) by the modulation method, the transmission output setting is maximum. Only when the value is a value, the operation is switched to the class C operation, and when the other transmission output setting values are smaller than the maximum value, the operation is not switched to the class C operation regardless of the modulation method, and all AB Operate in class. Therefore, the structure of the APC circuit is simplified and the size can be reduced. Further, the maximum value of the collector current can be made equal to that of the conventional one, so that the burden on the thermal design can be avoided.

[0039]

[Effect of the device]

 According to the transmitter of the present invention, the high frequency power amplifier is saturated and amplified when the output level of the modulated high frequency signal having the constant envelope is maximized, and is linearly amplified in other cases. Since the control loop can be configured with one, miniaturization is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment when the present invention is applied to a wireless telephone device.

FIG. 2 is a block diagram showing a configuration of a power amplification unit.

FIG. 3 is a circuit diagram showing a configuration of a power amplification circuit of a power amplification unit.

FIG. 4 is a graph showing a relationship between an input level and a collector current during class AB operation of a transistor.

FIG. 5 is a block diagram showing a configuration of a conventional power amplifier.

[Explanation of symbols]

 300 ... Control part 701 ... Variable attenuator 702 ... Power amplification circuit 703 ... Branch circuit 704 ... Detection circuit 705 ... Smoothing circuit 706 ... Reference power supply 707 ... Error amplifier 708 ... Sample & hold circuit

Claims (3)

[Scope of utility model registration request] 1. A first modulating means for performing a first modulation in which an envelope of a high frequency signal fluctuates, a second modulating means for performing a modulation in which an envelope of a high frequency signal is constant, and the first modulation. Selecting means for selecting means and the second modulating means, and electric power for the high frequency signal modulated by the modulating means selected by the selecting means among the first modulating means and the second modulating means. When the power amplifying means for performing amplification and the second modulating means are selected by the selecting means, and when the output level of the power amplifying means becomes maximum, the power amplifying means is saturated and amplified, and In the case of, a transmitter comprising a control means for controlling the power amplification means so as to perform linear amplification. 2. An attenuator for attenuating a signal input to the power amplifier, and an output level detector for detecting the output level of the power amplifier and generating an output level voltage corresponding to the output level. Comparing means for comparing the output level voltage generated by the output level detecting means with a predetermined reference voltage to generate a voltage difference signal corresponding to the difference between these voltages; and the voltage difference signal generated by the comparing means. The transmission device according to claim 1, further comprising: an attenuation level control unit that controls an attenuation amount of the attenuation unit based on the attenuation level control unit. 3. A transmission device used for communication between a base station and a mobile body, wherein the output level of the power amplification means is a transmission power signal requested by the base station. Transmitter.