JPH05268117A - Transmission power control system - Google Patents

Abstract

PURPOSE:To simplify the control and to realize optimum distortion compensation by controlling a distortion compensation circuit so that a level of a pilot signal or a distortion level is minimized. CONSTITUTION:An output signal (d) from a hybrid circuit 5 is a sum of signals b, c, a signal spread over processing band around a frequency f1, a distortion signal and a pilot signal whose frequency is respectively f2, f3 are generated, and the signal (d) passes through a mixer 12, an amplifier 14, a variable attenuator 15 and an amplifier 16, then the distortion component whose frequencies are f2, f3 is generated just in opposite phase to that of the signal (d) by the amplifiers 14, 16 with respect to a signal (e) at a prescribed frequency band around the frequency f1, the distortion component whose frequencies are f2, f3 is cancelled. Thus, only the signal at the frequency band around the frequency f1 and only a pilot signal P are outputted as a resulting signal (f), the pilot signal P is not sent to an opposite station because the pilot signal P is cut off by a band pass filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission power control system, and more particularly to a system which includes a distortion compensation circuit and which controls the transmission power of a transmitter according to a reception level from an opposite transmitter.

Recent transmitters are configured to reduce distortion by a distortion compensation circuit (predistortion circuit) and to reduce power consumption by using a high frequency amplifier having a low saturation output level. Furthermore, in order to prevent a situation in which the reception level of the receiver of the opposite station is lowered due to multipath fading, rain attenuation, etc. and a reception error occurs, technical development is underway toward a transmission power control method that controls the transmission level. It's been done.

Therefore, when performing such transmission power control, it is strongly desired that the distortion compensating circuit always optimally compensates the intermodulation distortion generated in the high frequency amplifier of the transmitter.

[0004]

2. Description of the Related Art FIG. 7 shows the principle of a conventional transmission power control method. The transmission power control should be increased (up) or decreased (down) according to the reception level from the opposite transmitter. Is determined (step S11),
When it is necessary to increase the transmission power, the variable attenuator in the high frequency amplifier is removed (step S12), the output level of the intermediate frequency amplifier is reduced, and the distortion generated in the distortion compensation circuit (PD) is reduced. There is.

When it is found in step S11 that the control for reducing the transmission power is necessary, a variable attenuator is inserted (step S14) to increase the output level of the intermediate frequency amplifier and generate it in the distortion compensation circuit. Increase distortion.

However, since the distortion increases in step S15, if the phase of this distortion is generated by the high frequency amplifier, it becomes possible to cancel the distortion (intermodulation distortion) by making it the same level as the phase opposite to the distortion.

FIG. 8 shows a configuration for implementing the conventional transmission power control system shown in FIG. 7 as described above. This configuration will be described below together with its operation.

First, an intermediate frequency (hereinafter sometimes referred to as IF) signal is converted into a high frequency (hereinafter sometimes referred to as RF) output signal by a transmitter 21, received by a receiver RX of an opposite station and demodulated. The received signal is obtained by demodulation by the device DEM, but the received signal RX of this opposite station monitors the level of the output signal of the transmitter 21, judges the level detected value, and modulates the judgment result. MOD
The data is sent back by the transmitter TX via the.

Therefore, the receiver RX receives the judgment result of the transmission level of the own station from the transmitter TX of the opposite station, and informs the transmitter 21 of the judgment result via the demodulator DEM.

On the other hand, in the transmitter 21, the intermediate frequency signal is always subjected to AGC (automatic gain control) by the intermediate frequency amplifier 1, the detector 2 and the control unit (CONT) 3 so that the signal of a constant level is always distortion-compensated. The intermediate frequency signal output from the distortion compensating circuit 10 to the circuit 10 is converted into a high frequency signal by being mixed with the local frequency signal from the local oscillator 13 by the mixer 12, and an amplifier 14 constituting a high frequency amplifier is provided. Is transmitted as a high-frequency output signal via the variable attenuator 15 and the amplifier 16, and this transmission output signal is fixed by the AGC circuit composed of the detector 17, the controller 18, the variable attenuator 15 and the amplifier 16. A power transmission output signal is generated.

In such a transmitter 21, the receiver RX gives an instruction to increase the transmission output from the opposite station as described above.
When the transmission power control unit 20 receives the signal via the demodulator DEM, the transmission power control unit 20 receives the control signal (CONT).
By controlling 18 so that the variable attenuator 15 does not act, and the output signal of the amplifier 14 is directly applied to the amplifier 16, the transmission output level is increased.

At the same time, the control unit 18 controls the control unit 3 via the offset control unit 19 so as to raise the output level of the intermediate frequency amplifier 1.

As a result, the level of the input signal to the distortion compensating circuit 10 increases and the amount of distortion generated increases. Therefore, in the distortion compensating circuit 10, the input signal is first branched into two by the hybrid circuit 4, and one of them is delayed by the delay unit. The signal is delayed by 6 for a certain time and then applied to the hybrid circuit 5. The other branched signal is distorted by the distortion generator 7, the constant phase is changed by the variable phase shifter 8, and further attenuated by the variable attenuator 9. It is sent to the hybrid circuit 5.

The variable phase shifter 8 and the variable attenuator 9 are arranged so that the phase of the distortion generated by the distortion compensating circuit 10 by the control unit 11 is the opposite phase to the distortion generated by the amplifiers 14 and 16 and has the same level. Is controlled to cancel the distortion (mutual extension distortion).

When an instruction to reduce the output power of the transmitter is received from the opposite station, the variable attenuator 15 is controlled so as to be inserted, and the output of the intermediate frequency amplifier 1 is output via the offset control unit 19. Control to decrease the level. At this time, the input signal level of the distortion compensating circuit 10 decreases, but some kind of distortion compensating operation is still required, so that the variable phase shifter 8 and the variable attenuator 9 are controlled by the control unit 11 as in the above case. It is like this.

[0016]

In the conventional system as described above, there is a problem that the control becomes complicated because the output level is controlled in two stages according to the change of the output level of the transmitter. is there.

Further, as shown in FIG. 9A, there is no problem in an ideal state where the input / output characteristics of the high frequency amplifiers 14 and 16 and the distortion characteristics of the distortion compensating circuit 10 are close to each other. As shown in (b) and (c) of FIG. 3, the input and output characteristics of the two are different, and further, since the individual characteristics of the high frequency amplifiers 14 and 16 have variations, the distortion cannot be optimally adjusted. There is also.

Therefore, the present invention provides a distortion compensating circuit and controls the transmission power of the transmitter by inserting / removing the variable attenuator according to the reception level from the transmitter of the opposite station, thereby simplifying the output level control. The purpose is to make the input / output characteristics of the high frequency amplifier and the distortion compensation circuit relevant to each other.

[0019]

FIG. 1 is a flow chart showing the principle of the transmission power control system (No. 1) according to the present invention. In this system, the transmission power control is increased from the opposite station. It is determined whether the transmission power should be decreased or reduced (step S1), and when the transmission power needs to be increased, the variable attenuator is removed (step S2),
When reducing the transmission power, control is performed so that a variable attenuator is inserted (step S3).

On the other hand, in the present invention, the pilot signal is superposed on the input signal of the distortion compensation circuit, and such pilot signal is extracted from the transmission output signal from the high frequency amplifier (step S4), and the level of this pilot signal is extracted. Is detected (step S5), and the distortion compensation circuit is controlled so that the level of this pilot signal is minimized (step S6).

By doing so, the level control is not necessary even in the intermediate frequency amplifier, and the control of the distortion compensating circuit is controlled from the transmission output signal by using the pilot signal. Therefore, the input of the high frequency amplifier and the distortion compensating circuit is performed. A large correlation can be obtained in the characteristics.

FIG. 2 shows in principle the transmission power control method (No. 2) according to the present invention. In the present invention, the steps up to step S3 are the same as those of the present invention (No. 1) of FIG. After that, the distortion level in the transmission output from the high frequency amplifier is detected (step S7), and the distortion compensation circuit is controlled so that this distortion level is minimized (step S8).

Further, in the transmission power control method (No. 3) according to the present invention, as shown by the dotted line in FIG. 2, the transmission output signal is converted from the high frequency band to the intermediate frequency band without going to step 7. The distortion level in the signal in the intermediate frequency band is detected (step S9), and the distortion compensation circuit is controlled so that this distortion level becomes minimum (step S8).

When the distortion compensating circuit is controlled by detecting the distortion level in the transmission output signal as described above, a special circuit for the pilot signal is not required and the input characteristics of the high frequency amplifier and the distortion compensating circuit are large. You have a correlation.

[0025]

FIG. 3 shows an embodiment of the transmission power control method (No. 1) according to the present invention shown in FIG. 1. In this embodiment, the distortion compensating circuit 10 in the transmitter 21 is fed to the pilot signal. Is superimposed as an input signal, a mixer 31 for mixing a transmission output signal from the amplifier 16 and a pilot signal from the oscillator 30, and the mixer 3
1, a low-pass filter 32 for detecting the level of the pilot signal output from the signal generator 1, and a variable phase shifter 8 and a variable attenuation of the distortion compensation circuit 10 according to the level of the pilot signal detected by the low-pass filter 32. A difference from the conventional example shown in FIG. 8 is that a control unit 33 for controlling the device 9 is newly provided and an offset control unit 19 for controlling the intermediate frequency amplifier 1 from the control unit 18 is removed.

Next, the operation of the embodiment of the present invention shown in FIG. 3 will be described with reference to the waveform diagram shown in FIG. 4. First, when the intermediate frequency signal is input to the transmitter 21, the amplifier 1 causes The signal a is amplified and has a constant frequency band (not shown) centered on the frequency f1. And this signal a
The pilot signal from the oscillator 30 is superposed on and is branched by the hybrid circuit 4 into a signal b, and the other signal branched by the hybrid circuit 4 is the distortion generator 7, the variable phase shifter 8 and the variable attenuator 9. , The anti-phase distortion component around the frequency f1 is generated at the frequencies f2 and f3 outside the band of the signal a, and the pilot signal P also becomes a signal attenuated in the opposite phase and is given to the hybrid circuit 5. Be done.

Accordingly, the output signal d from the hybrid circuit 5 has a form in which the signal b and the signal c are added, and as shown in the figure, a signal spread over a certain band centering on the frequency f1 and a distortion signal of frequencies f2 and f3 and A pilot signal is generated, and the signal d passes through the mixer 12, the amplifier 14, the variable attenuator 15, and the amplifier 16, so that the amplifier 14 and the signal e in the constant frequency band centered around the frequency f1 are generated. At 16, the distortion components of the frequencies f2 and f3 are just generated in the opposite phase to the signal d, so these distortion components of the frequencies f2 and f3 are canceled out, and only the signal in the frequency band centered on the frequency f1 and the pilot signal P are signaled. The pilot signal P is output as f and is cut by a band filter (not shown) so as not to be transmitted to the opposite station.

Therefore, in the mixer 31 to which the signal f and the pilot signal P from the oscillator 30 are input, the pilot signal is taken out by performing the synchronous detection, and the pilot signal is converted to the DC level by the low-pass filter 32. When the signal is converted and the level is detected and given to the automatic control unit 33, the automatic control unit 33 controls the variable phase shifter 8 and the variable attenuator 9 as indicated by the signal e.

FIG. 5 shows an embodiment of the transmission power control system (No. 2) according to the present invention shown by the solid line in FIG. 2. In this embodiment, pilot signals are transmitted as in the embodiment of FIG. Instead, the distortion of the transmission output signal is detected and the automatic control unit 33 tries to control the distortion compensation circuit 10 according to the detection result.

That is, as shown in the figure, a circuit in which a narrow band filter 41, a high frequency amplifier 43 and a detector 45 for detecting the distortion level are connected in series to detect the distortion of the transmission output signal is provided on the input side of the automatic control unit 33. The points provided are different from the embodiment shown in FIG.

When the narrow band filter 41 is a narrow band filter on the high band side, the distortion component (hatched part) of a constant frequency band around the low band frequency f2 is amplified as shown in the waveform in the figure. The automatic control unit 33 detects the level of the distortion component of the frequency f2 detected by the detector 43 and the detector 45.
To the distortion compensation circuit 1
The variable phase shifter 8 and the variable attenuator 9 at 0 are controlled so that distortion components of the same level are generated in antiphase as shown in FIG. 4 to cancel the distortion components due to the high frequency amplifier. Further, in order to extract the distortion component of the frequency f3 on the high frequency side and detect the distortion level thereof, the narrow band filter 40 for distortion detection on the high frequency side, the amplifier 42 and the detector 4 as shown by the dotted line.
A series circuit with 4 may be used.

FIG. 6 shows an embodiment of the transmission power control system (part 3) according to the present invention, which is partially shown by the dotted line in FIG. 2, and in this embodiment, the transmission output signal and the local oscillator 13 are used.
A narrow band constituting a mixer 50 for mixing a local oscillation signal from the converter to convert it to an intermediate frequency signal, and a circuit for detecting the level of the distortion component with respect to the intermediate frequency signal from the mixer 50 as in FIG. A point different from the embodiments of FIGS. 3 and 5 is that a series circuit including a filter 51, an amplifier 53, and a detector 54 for detecting a distortion level is provided on the input side of the automatic control unit 33.

However, in this embodiment, since the mixer 50 converts the signal into the intermediate frequency signal, the narrow band filter 51 is a narrow band filter having a lower frequency than the narrow band filter 41 of FIG. Is composed of an intermediate frequency amplifier.

Distortion components f2 'and f3' are also generated as shown in the figure for the signal in the frequency band centered on the frequency f1 'as shown in the figure, which is output from the mixer 50. In order to detect the distortion component of the frequency f2 ′ on the low frequency side, the narrow band filter 51 is used for the low frequency side and the amplifier 53 is an amplifier of the intermediate frequency band, and the distortion component of the frequency f3 ′ on the high frequency side is extracted. In order to perform the distortion level detection, a series circuit including a high-frequency side narrow band filter 52 for distortion detection, an intermediate frequency amplifier 54, and a detector 56 may be used as shown by a dotted line.

[0035]

As described above, according to the transmission power control method of the present invention, the pilot signal is superimposed on the input signal of the distortion compensation circuit and the level of the pilot signal is detected from the transmission output signal, or The distortion level in the transmission output signal or the distortion level of the signal obtained by converting the transmission output signal into an intermediate frequency unit is detected, and the distortion compensation circuit is controlled so that the level of the pilot signal or the distortion level is minimized. Since it is configured, the intermediate frequency amplifier on the input side of the transmitter does not need to be included in the transmission power control, the control is simplified, and the distortion compensation operation correlated with the transmission power can be realized, so that the optimum distortion compensation is realized. be able to.

[Brief description of drawings]

FIG. 1 is a flowchart showing the principle of a transmission power control method (No. 1) according to the present invention.

FIG. 2 is a flowchart showing the principle of the transmission power control method (No. 2 and No. 3) according to the present invention.

FIG. 3 is a block diagram showing an embodiment of a transmission power control method (No. 1) according to the present invention.

FIG. 4 is a waveform diagram for explaining the operation of the embodiment of the transmission power control system according to the present invention.

FIG. 5 is a block diagram showing an embodiment of a transmission power control method (No. 2) according to the present invention.

FIG. 6 is a block diagram showing an embodiment of a transmission power control method (Part 3) according to the present invention.

FIG. 7 is a flowchart showing the principle of the conventional method.

FIG. 8 is a block diagram showing a configuration example of a conventional method.

FIG. 9 is a diagram for explaining a problem of the conventional example.

[Explanation of symbols]

 7 Distortion generating section 8 Variable phase shifter 9 Variable attenuator 10 Distortion compensating circuit 14, 16 High frequency amplifier 15 Variable attenuator 17 Detector 18 Control section 20 Transmission power control section 21 Transmitter 30 Pilot signal oscillator 31, 50 Mixer 32 Low Distortion filter 33 Distortion compensation circuit automatic control unit 40, 41, 51, 52 Distortion detection narrow band filter 42, 43, 53, 54 Amplifier 44, 45, 55, 56 Distortion level detection detector Indicates the same or a corresponding portion.

Claims (3)

[Claims] 1. A system comprising a distortion compensation circuit, wherein transmission power control of a transmitter is performed by inserting / removing a variable attenuator according to a reception level from a transmitter of an opposite station, wherein a pilot signal is supplied to the distortion compensation circuit. A transmission power control system characterized by superimposing it on an input signal, extracting the pilot signal from a transmission output signal, detecting the level, and controlling the distortion compensation circuit so that the level of the pilot signal is minimized. .. 2. A system comprising a distortion compensation circuit, wherein transmission power control of a transmitter is performed by inserting / removing a variable attenuator according to a reception level from a transmitter of an opposite station, the distortion level in a transmission output signal is controlled. A transmission power control method characterized by detecting and controlling the distortion compensating circuit so as to minimize the distortion level. 3. A system comprising a distortion compensating circuit, wherein transmission power control of a transmitter is performed by inserting / removing a variable attenuator according to a reception level from a transmitter of an opposite station. A transmission power control method characterized by converting to a frequency band, detecting a distortion level in the intermediate frequency band signal, and controlling the distortion compensation circuit so that the distortion level is minimized.