JP4394296B2 - Automatic phase control method and transmitter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmitter, and more particularly to a loop phase control method capable of following a sudden phase change caused by switching between temperature and transmission frequency.
[0002]
[Prior art]
A linear modulation method widely used in digital mobile communication requires a linear amplifier as a power amplifier of a transmitter. Therefore, since it is possible to achieve both high power efficiency and good linearity, a nonlinear distortion compensation type power amplifier (linearizer) is employed. As one of the typical compensation methods, a Cartesian loop system that performs distortion compensation using a signal obtained by negatively feeding back a part of the output of the transmission power amplifier is well known. However, in this Cartesian loop system, since the stability of the loop is very important because of the closed loop control, the phase control of the loop is indispensable in order to operate the loop stably.
[0003]
An example of a transmitter to which a conventional Cartesian loop nonlinear distortion compensation technique is applied will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration of a conventional mobile communication terminal radio unit. 1 and 2 are input terminals, 3 and 4 are subtractors, 5 is a quadrature modulator (MOD), 6 and 8 and 14 are bandpass filters (BPF), 7 and 13 are mixers, 9 is a power amplifier, and 10 is a coupler , 11 is an antenna, 12 is an attenuator, 15 is a quadrature demodulator (DEMOD), 16 and 17 are oscillators, 18 is a phase shifter, 19 is a phase control circuit, and 22 and 23 are band limiting circuits.
The input terminal 1 is connected to the subtracted input terminal side of the phase control circuit 19 and the subtracter 3, and the input terminal 2 is connected to the subtracted input terminal side of the phase control circuit 19 and the subtractor 4. The output of the subtractor 3 is connected to the band limiting circuit 22, and the output of the subtracter 4 is connected to the band limiting circuit 23. Further, the outputs of the band limiting circuit 22 and the band limiting circuit 23 are connected to the quadrature modulator 5, respectively. The output of the quadrature modulator 5 is connected to the BPF 6, and the output of the BPF 6 is connected to the mixer 7. The output of the mixer 7 is connected to the BPF 8, and the output of the BPF 8 is connected to the power amplifier 9. The output of the power amplifier 9 is connected to the coupler 10, and the output of the coupler 10 is connected to the antenna 11 and the attenuator 12. The output of the attenuator 12 is connected to the mixer 13, and the output of the mixer 13 is connected to the quadrature demodulator 15. The output in-phase component (i) of the quadrature demodulator 15 is connected to the subtraction input terminal side of the subtractor 4 and the phase control circuit 19, and the output quadrature component (q) of the quadrature demodulator 15 is connected to the subtraction input terminal side of the subtractor 3. Connected to the phase control circuit 19. The output of the phase control circuit 19 is connected to the phase shifter 18. Further, the output of the oscillator 16 is connected to the quadrature modulator 5 and the phase shifter 18, and the output of the phase shifter 18 is connected to the quadrature demodulator 15. Furthermore, the output of the oscillator 17 is connected to the mixer 7 and the mixer 13.
[0004]
First, the transmission operation of the conventional transmitter will be described.
In FIG. 3, the oscillator 16 generates a carrier wave signal and supplies it to the quadrature modulator 5 and the phase shifter 18. The oscillator 17 generates an intermediate frequency signal and supplies it to the mixer 7 and the mixer 13.
The quadrature component (Q) of the baseband signal is input from the input terminal 1, and the in-phase component (I) of the baseband signal is input from the input terminal 2. The quadrature component (Q) of this baseband signal is given to the band limiting circuit 22 via the subtractor 3, band-limited so as to have a desired loop characteristic, and given to the quadrature modulator 5. The in-phase component (I) of the baseband signal is also supplied to the band limiting circuit 23 via the subtracter 4, band-limited so as to have a desired loop characteristic, and supplied to the quadrature modulator 5. The quadrature modulator 5 performs quadrature modulation on the carrier wave signal input from the oscillator 16 with the two input signals, and provides the output (modulated wave signal) to the BPF 6. The BPF 6 removes out-of-band spurious from the inputted modulated wave signal, and gives it to the mixer 7. The mixer 7 mixes with the carrier wave signal supplied from the oscillator 17, performs frequency conversion of the input signal, and supplies it to the BPF 8. The BPF 8 removes out-of-band spurious from the input signal and applies it to the power amplifier 9. The power amplifier 9 amplifies the power of the input signal to a specified output level and transmits it from the antenna 11 via the coupler 10.
[0005]
On the other hand, a part of the output signal of the power amplifier 9 is taken out by the coupler 10 and given to the attenuator 12 as a feedback signal. The attenuator 12 adjusts the power level of the input feedback signal to an appropriate value and supplies it to the mixer 13. The mixer 13 mixes the signal input from the attenuator 12 with the intermediate frequency signal supplied from the oscillator 17 and converts the frequency to the BPF 14. The BPF 14 removes unnecessary components from the input signal and supplies the result to the quadrature demodulator 15.
The quadrature demodulator 15 is a carrier wave signal input from the phase shifter 18, and the signal input from the BPF 14 is orthogonally demodulated to the baseband signal, and the orthogonal component (q) of the orthogonally demodulated baseband signal is subtracted by the subtractor 3. And the in-phase component (i) is supplied to the subtractor 4.
[0006]
The subtracter 3 subtracts the quadrature component (q) of the feedback baseband signal from the quadrature component (Q) of the input baseband signal and applies the subtractor 3 to the quadrature modulator 5, and the in-phase component (I) of the feedback baseband signal from the in-phase component (I) ( Negative feedback is applied by subtracting i) and applying it to the quadrature modulator 5.
In such a negative feedback configuration, in order to stabilize the system, it is necessary to adjust the phase difference between the input baseband signal and the feedback baseband signal to 0 ° on the input sides of the subtractor 3 and the subtractor 4, respectively. . Therefore, it is necessary to control the phase shifter 18 by the phase control circuit 19 so that the phase difference between the input signal and the feedback signal becomes 0 °.
[0007]
Next, a conventional automatic phase control method for a transmitter will be described.
In FIG. 3, the quadrature component (Q) and the in-phase component (I) of the baseband signal input from the input terminals 1 and 2 are also given to the phase shift control circuit 19. Further, the quadrature component (q) and the in-phase component (i) of the feedback baseband signal given to the adders 3 and 4 are also given to the phase control circuit 19.
The phase control circuit 19 compares both the input baseband signal and the feedback baseband signal output from the quadrature demodulator, and if the phase of the feedback baseband signal is delayed, the phase shifter 18 A phase control signal is supplied to the phase shifter 18 so as to decrease the phase shift amount and control the phase shifter 18 to increase the phase shift amount when the phase shift is advanced. The phase shifter 18 performs phase shift of the carrier signal input from the oscillator 16 based on the phase control signal supplied from the phase control circuit 19, and changes the phase of the carrier signal supplied to the quadrature demodulator 15. Automatic phase control of the transmitter loop.
The automatic phase control function of the transmitter as described above is described in, for example, Japanese Patent No. 2746133.
[0008]
[Problems to be solved by the invention]
In the above-described prior art, the phase control circuit is constituted by a digital circuit that performs phase comparison after the input signal is pulsed by a limiter or the like in order to follow the change of the loop phase due to temperature or the like. There is a drawback that spurious is deteriorated due to leakage of a pulse signal.
Further, the conventional technique employs a method of following up or down a counter corresponding to the amount of phase shift according to the detected advance or delay of the phase. For this reason, in the usage pattern in which the transmission frequency is switched as in the vehicle-mounted device, there is a drawback that it is not possible to quickly follow a sudden phase change that occurs when the frequency is switched, and oscillation occurs in the worst case at the start of transmission.
The object of the present invention is to optimize the phase of the loop with respect to changes in temperature and transmission frequency without using a digital circuit to perform phase comparison in the phase control circuit in order to eliminate the above drawbacks. To provide an automatic phase control method and a transmitter that can be set to a value.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the automatic phase control function of the present invention monitors the temperature inside the transmitter with a temperature sensor, and when a temperature change occurs, a temperature table prepared in advance or In this configuration, automatic phase control is performed by giving optimum phase data of the loop phase calculated by the phase control circuit to the phase shifter from the approximate expression of the phase change with respect to the temperature change. For phase changes due to changes in transmission frequency, a frequency table in which optimum phase values for each transmission frequency stored in advance in the phase control circuit are tabulated, or an approximate expression for phase change with respect to frequency changes, is used when the transmission frequency changes. The automatic phase control is performed by calling and giving the information to the phase shifter.
[0010]
That is, the automatic phase control method of the present invention amplifies the baseband signal, feeds back a part of the amplified signal, and adds or subtracts the fed back baseband signal to the baseband signal, thereby reducing the nonlinear distortion of the amplifier. In a transmitter including a negative feedback amplifier for compensation, the temperature inside the transmitter is detected, and the phase of the feedback baseband signal is changed based on the detected temperature.
For this purpose, a temperature table for referring to a phase correction amount corresponding to a temperature change in advance is provided, and the phase of the baseband signal fed back by the phase correction amount of the temperature table corresponding to the detected temperature is changed.
For this purpose, an approximate expression for calculating a phase correction amount corresponding to a temperature change is provided in advance, and the baseband signal obtained by calculating the phase correction amount with respect to the detected temperature by the approximate expression and feeding back the calculated phase correction amount. The phase is changed.
Furthermore, the automatic phase control method of the present invention changes the initial phase of the baseband signal fed back in accordance with the transmission frequency when the transmission frequency is switched.
Therefore, the automatic phase control method of the present invention includes a frequency table for referring to an initial phase setting value corresponding to the value of the transmission frequency in advance, and feedback is performed according to the initial phase setting value of the frequency table corresponding to the transmission frequency to be switched. The phase of the baseband signal is changed.
In addition, the automatic phase control method of the present invention includes an approximate expression for calculating an initial phase set value corresponding to the value of the transmission frequency in advance, and calculates an initial phase set value for the transmission frequency to be switched by the approximate expression. The phase of the baseband signal fed back by the initial phase setting value is changed.
[0011]
Furthermore, the transmitter of the present invention inputs a baseband signal via an adder or subtracter, performs a predetermined band limitation circuit, a quadrature modulator that performs quadrature modulation on the band-limited signal, An amplifier that amplifies the modulated signal; and a quadrature demodulator that demultiplexes a part of the amplified signal and performs quadrature demodulation, and supplies the quadrature demodulated signal to the first adder or subtractor, In a negative feedback amplifier that compensates for nonlinear distortion of the amplifier by adding or subtracting band signals, a temperature sensor that detects the internal temperature of the transmitter and a quadrature demodulated based on the temperature detected by the temperature sensor A phase control circuit that outputs a phase control signal for correcting the phase of the signal and a phase shifter that corrects the phase of the quadrature demodulated signal based on the phase control signal are orthogonal to the baseband signal. It is intended to match the phase of the tone signal.
Furthermore, the transmitter of the present invention includes a central control device that switches the transmission frequency, and the phase control circuit sets an initial phase for switching the initial phase value of the phase shifter based on the transmission frequency information input from the central control device. The control signal is output, and the phase shifter changes the initial phase value to the initial phase setting control signal.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a mobile communication terminal radio unit according to the present invention. Components having the same functions as those described in FIG. 3 are given the same numbers. In addition, 19 'is a phase control circuit, 20 is a temperature sensor, and 21 is a central control unit (CPU: Central Processing Unit, hereinafter referred to as CPU).
The configuration of FIG. 1 replaces the phase control circuit 19 with a phase control circuit 19 'in FIG. 3, connects the output of the temperature sensor 20 to the phase control circuit 19', and combines the CPU 21 and the phase control circuit 19 '. is doing. Further, the signals from the input terminals 1 and 2 and the quadrature demodulator 15 are not input to the phase control circuit 19 ′. Further, as a signal input from the phase control circuit 19 'to the phase shifter 18, there is an initial phase setting signal for changing the initial setting value of the phase value in addition to the phase control signal related to the phase correction amount.
[0013]
The transmission operation of the transmitter shown in FIG. 1 is the same as that of the prior art described with reference to FIG.
An embodiment of a transmitter phase control method according to the present invention will be described below.
In the present invention, a temperature sensor is installed to constantly monitor the temperature of the peripheral portion of the device that affects the phase change due to the temperature change. The temperature sensor is attached inside the transmitter of the mobile communication terminal radio unit. In particular, it is attached in the vicinity of an element (for example, a high-frequency band-pass filter: in FIG. 1, a band-pass filter 8) that is greatly affected by characteristic changes due to temperature fluctuations.
The temperature sensor 20 sequentially inputs a signal (temperature data) corresponding to the detected temperature to the phase control circuit 19 ′. The phase control circuit 19 ′ reads the input temperature data at a predetermined time interval, reads the phase correction amount with reference to the temperature table stored in the phase control circuit 19 ′ in advance, and sets the phase correction amount to the phase correction amount. Based on the phase control signal, the phase shifter 18 is provided. The phase shifter 18 performs phase shift of the carrier wave signal input from the oscillator 16 based on the phase control signal given from the phase control circuit 19 ', and changes the phase of the carrier wave signal given to the quadrature demodulator 15. Thus, automatic phase control of the transmitter loop is performed.
Note that an initial value of the phase shift amount is set in advance in the phase shifter 18, and an input phase control signal determines the phase shift amount from the set initial phase value.
[0014]
Next, the phase control method using the temperature table will be further described with reference to FIGS. FIG. 2 is a block diagram showing the configuration of an embodiment of the phase control circuit used in the present invention. FIG. 6 is a diagram showing an example of a temperature table used in the present invention.
The temperature table is a table in which phase correction amounts for temperature data are preliminarily tabulated, and a temperature table determined based on a phase change amount for each temperature measured in advance is used. In this embodiment, the initial phase value is determined based on the phase of 20 ° C. 91 is an A / D converter, 92 is a temperature table memory storing a temperature table, 93 is a frequency table memory storing a frequency table, and 94 is an adder.
[0015]
In FIG. 2, temperature data input from the temperature sensor 20 is given to the A / D converter 91, converted into a digital value, and given to the temperature table memory 92. In the temperature table memory 92, the phase correction amount corresponding to the input digital value is read out against the temperature table and output to the phase shifter 18 as a phase control signal.
Note that it is also possible to perform phase control using an approximate expression as a substitute for the temperature table. FIG. 4 is a graph showing an example of the relationship between the temperature detected by the temperature sensor 20 and the optimum phase correction amount. The horizontal axis represents temperature (° C.), and the vertical axis represents the optimum phase correction amount Δφ (°). The solid line portion of this graph is, for example, an approximation equation approximated by a straight line. For example, an approximate equation calculation unit is provided instead of the temperature table memory 92 of FIG. Similarly, automatic phase control can be performed.
[0016]
Next, the case where the transmission frequency is switched, which is another embodiment of the present invention, will be further described with reference to FIGS. FIG. 7 is a diagram showing an embodiment of a frequency table used in the present invention.
For the transmission frequency, a frequency table memory 93 is prepared in which optimum phase values for the transmission frequency are stored in a table.
In FIG. 2, frequency information given from the CPU 21 is input to the frequency table memory 93. The frequency table memory 93 reads the initial phase setting value corresponding to the frequency optimum phase value from the input frequency information, and outputs it to the phase shifter 18 as an initial phase setting control signal. The phase shifter 18 changes the setting of the initial phase value set in the phase shifter 18 based on the input initial phase setting control signal.
[0017]
In the above embodiment, a subtractor is used to synthesize the input baseband signal and the feedback baseband signal. However, an adder may be used. In this case, the input baseband signal and the feedback baseband signal are used. Adjust the phase difference to 180 °.
It is also possible to perform phase control using an approximate expression as a substitute for the frequency table. FIG. 5 is a diagram illustrating an example in which the relationship between the frequency output by the CPU 21 and the optimum phase correction amount is graphed. The horizontal axis represents the transmission frequency f (MHz), and the vertical axis represents the optimum phase value φ (°). The solid line portion of this graph is, for example, an approximation equation approximated by a straight line, for example, by providing a calculation unit of an approximation equation instead of the frequency table memory 93 of FIG. Similarly, automatic phase control can be performed.
Incidentally, the phase shift due to secular change is dealt with, for example, by periodically updating the contents of the temperature table and the frequency table.
[0018]
【The invention's effect】
As described above, according to the present invention, the dedicated control circuit for dealing with the phase change due to the temperature change is not required by the temperature sensor and the temperature table prepared in advance. As a result, the cause of spurious deterioration generated by the digital circuit can be solved. Furthermore, by using the frequency table, the stability of the loop is always maintained even when the transmission frequency is switched, and the oscillation of the transmitter can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of an embodiment of a phase control circuit used in the present invention.
FIG. 3 is a block diagram showing a configuration of a conventional mobile communication terminal radio unit.
FIG. 4 is a graph showing an example of the relationship between temperature and optimum phase correction amount.
FIG. 5 is a graph showing an example of the relationship between frequency and optimum phase correction amount.
FIG. 6 is a diagram showing an example of a temperature table used for phase control according to the present invention.
FIG. 7 is a diagram showing an example of a frequency table used for phase control according to the present invention.
[Explanation of symbols]
1, 2: Input terminal, 3, 4: Subtractor, 5: Quadrature modulator (MOD), 6, 8, 14: Band pass filter (BPF), 7, 13: Mixer, 9: Power amplifier, 10: Coupler 11: Antenna, 12: Attenuator, 15: Quadrature demodulator (DEMOD), 16, 17: Oscillator, 18: Phase shifter, 19, 19 ': Phase control circuit, 20: Temperature sensor, 21: CPU, 22 , 23: Band limiting circuit, 91: A / D converter, 92: Temperature table memory, 93: Frequency table memory.

Claims (8)

A negative feedback amplifier that amplifies a baseband signal, feeds back a part of the amplified signal, and adds or subtracts the fed back baseband signal to or from the baseband signal to compensate for nonlinear distortion of the amplifier; In the transmitter
When the temperature inside the transmitter is detected and the phase of the feedback baseband signal is changed based on the detected temperature and the transmission frequency is switched, the feedback baseband corresponding to the transmission frequency is used. An automatic phase control method characterized by changing an initial phase value of a signal . The automatic phase control method according to claim 1,
A frequency table for referring to an initial phase setting value corresponding to a transmission frequency value in advance is provided.
An automatic phase control method, wherein the phase of the fed back baseband signal is changed according to an initial phase setting value of the frequency table corresponding to a transmission frequency to be switched. The automatic phase control method according to claim 1,
An approximate expression for calculating an initial phase setting value corresponding to the value of the transmission frequency in advance is provided.
An automatic phase control method, wherein an initial phase setting value for a transmission frequency to be switched is calculated by the approximate expression, and the phase of the feedback baseband signal is changed by the calculated initial phase setting value. A negative feedback amplifier that amplifies a baseband signal, feeds back a part of the amplified signal, and adds or subtracts the fed back baseband signal to or from the baseband signal to compensate for nonlinear distortion of the amplifier; In the transmitter
An automatic phase control method characterized by changing an initial phase value of the fed back baseband signal corresponding to a transmission frequency when the transmission frequency is switched. The automatic phase control method according to claim 4, wherein
A frequency table for referring to an initial phase setting value corresponding to a transmission frequency value in advance is provided.
An automatic phase control method, wherein the phase of the fed back baseband signal is changed according to an initial phase setting value of the frequency table corresponding to a transmission frequency to be switched. The automatic phase control method according to claim 4, wherein
An approximate expression for calculating an initial phase setting value corresponding to the value of the transmission frequency in advance is provided.
An automatic phase control method, wherein an initial phase setting value for a transmission frequency to be switched is calculated by the approximate expression, and the phase of the feedback baseband signal is changed by the calculated initial phase setting value. A band-limiting circuit that inputs a baseband signal via an adder or subtractor and performs a predetermined band limitation;
An orthogonal modulator for orthogonally modulating the band-limited signal;
An amplifier for amplifying the quadrature modulated signal;
A quadrature demodulator for demultiplexing a part of the amplified signal and performing quadrature demodulation;
In a negative feedback amplifier that compensates for nonlinear distortion of the amplifier by applying the quadrature demodulated signal to the adder or subtractor and adding or subtracting the baseband signal,
A temperature sensor for detecting the temperature inside the transmitter;
A phase control circuit that outputs a phase control signal to correct the phase of the quadrature demodulated signal based on the temperature detected by the temperature sensor;
A phase shifter for correcting the phase of the quadrature demodulated signal based on the phase control signal ;
A central control device for switching a transmission frequency, and the phase control circuit outputs an initial phase setting control signal for switching an initial phase value of the phase shifter based on transmission frequency information input from the central control device; The phase shifter changes an initial phase value to the initial phase setting control signal . A band-limiting circuit that inputs a baseband signal via an adder or subtractor and performs a predetermined band limitation;
An orthogonal modulator for orthogonally modulating the band-limited signal;
An amplifier for amplifying the quadrature modulated signal;
A quadrature demodulator for demultiplexing a part of the amplified signal and performing quadrature demodulation;
In a negative feedback amplifier that compensates for nonlinear distortion of the amplifier by applying the quadrature demodulated signal to the adder or subtractor and adding or subtracting the baseband signal,
A phase control circuit that outputs a phase control signal to correct the phase of the quadrature demodulated signal;
A phase shifter for correcting the phase of the quadrature demodulated signal based on the phase control signal;
A central control device for switching a transmission frequency, and the phase control circuit outputs an initial phase setting control signal for switching an initial phase value of the phase shifter based on transmission frequency information input from the central control device; The phase shifter changes an initial phase value to the initial phase setting control signal.

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