JPH07112163B2 - Linear modulation wireless transmitter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a linear modulation wireless transmission device using linear modulation capable of adaptively controlling average transmission power.

[Conventional technology]

FIG. 7 is a block diagram showing a conventional wireless transmission device,
In the figure, 10 is an FM modulator that frequency-modulates a carrier, and 20
Is a transmission power amplifier for amplifying a modulated carrier wave, 3 is a directional coupler, 4 is a level detector for detecting the level of an amplified signal, and 5 is a large number of comparison reference voltages V _i (i = 1 to n). A selector for selecting one of the following, 6 is a selected comparison reference voltage
A differential amplifier that amplifies the difference between V _i and the output signal of the level detector 4, 7 is a transmitting antenna, and 8 is a loop filter that determines the frequency characteristic of the loop.

Next, the operation will be described. The FM modulator 10 frequency-modulates a carrier with a modulation signal and outputs the modulated carrier. Next, the transmission power amplifier 20 amplifies the modulated carrier wave and outputs an amplified signal. This amplified signal is applied to the directional coupler 3
And is supplied to the transmitting antenna 7. Then, the transmitting antenna 7 sends out the amplified signal as a radio wave.

Further, the directional coupler 3 detects a traveling wave due to the amplified signal. Then, the detected traveling wave is input to the level detector 4. The level detector 4 detects the level of the traveling wave and outputs an output signal having a voltage corresponding to the level. On the other hand, the comparison reference voltage V _i corresponding to the predetermined transmission power is selected by the switch 5. Then, the selected comparison reference voltage V _i is input to the differential amplifier 6 together with the output signal of the level detector 4. The differential amplifier 6 amplifies the difference voltage between the voltage corresponding to the traveling wave level indicated by the output signal of the level detector 4 and the selected comparison reference voltage V _i, and outputs this difference voltage as an output signal. . This output signal is used by the loop filter 8 which determines the frequency characteristic of the loop.
After passing through, transmit power amplifier as power amplification control signal
Input to 20 control input terminals. As a result, the amplified signal output by the transmission power amplifier 20 has a value corresponding to the predetermined average transmission power.

FIG. 8 is a circuit diagram showing an example of the case where the transmission power amplifier 20 is composed of a field effect transistor or the like. It can be seen that the modulated carrier wave input to the input terminal is amplified by the amplification factor determined by the power amplification control signal input to the control input terminal and output as an amplified signal from the output terminal.

In this way, the average transmission power is automatically fixed to a predetermined value even if power supply voltage fluctuations or temperature fluctuations occur.

[Problems to be Solved by the Invention]

Since the conventional wireless transmitter is configured as described above, the transmission power is automatically controlled when the envelope of the modulated carrier is constant regardless of the modulation signal as in the case of using frequency modulation. However, when linear modulation in which the envelope of the modulated carrier changes according to the modulation signal is used, the feedback control suppresses the envelope component of the modulated carrier, and thus the modulated component is modulated. There is a problem that the information originally possessed by the carrier wave is damaged or the transmission spectrum is spread. In order to deal with this problem, if the time constant of the feedback loop is increased to make it difficult to follow changes in the envelope component, the response at the rising edge becomes slow and it cannot be applied to burst transmission that transmits intermittently. There was a problem.

The present invention has been made to solve the above problems, and can automatically maintain a constant average transmission power value without suppressing the envelope component of a linearly modulated carrier, and burst transmission. It is an object of the present invention to obtain a linear modulation wireless transmission device having a fast rising characteristic and capable of automatically controlling the average transmission power to be constant when performing the above.

[Means for Solving the Problems]

A linear modulation wireless transmission device according to the present invention includes an adjusting unit that adjusts an input level or a gain of a power amplifier that amplifies a linearly modulated carrier wave, and a level detecting unit that detects an envelope component of an amplified signal output by the power amplifier. A scaling means for converting the envelope component of the modulation signal or the output signal of the level detection means using a coefficient according to a predetermined average transmission power, and the level of the output signal of the level detection means or the envelope component of the modulation signal, Comparing with the level of the output signal of the scaling means, and based on this comparison result, the adjusting means gives a control signal to the adjusting means such that the level of the amplified signal becomes a value corresponding to the determined average transmission power. And means.

[Action]

The scaling means in the present invention converts the level of the envelope component of the modulated signal or the envelope component of the amplified signal using a coefficient according to the average transmission power, and outputs the scaled level. Further, the comparison means adjusts the envelope component of the modulated signal and the scaled level or compares the level of the amplified signal with the scaled level to adjust the level of the amplified signal to a value commensurate with the average transmission power. The means outputs a control signal indicating an adjustment amount to be adjusted.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
1 is a block diagram showing a linear modulation wireless transmission device according to a first embodiment of the present invention. In FIG. 1, 1 is a linear modulator that linearly modulates a carrier with a modulation signal, 9 is a variable attenuator that is an example of adjusting means, 2 is a linear power amplifier (power amplifier), and 11 is a coefficient according to the average transmission power. , A coefficient unit (scaling means) for scaling the output of the level detector 4, 12 is a comparison circuit (comparison means) for comparing the coefficient unit 11 with the envelope component of the modulation signal output by the linear modulator 1, and 8 is a loop. It is a loop filter that determines the frequency characteristics. Others are the same as those shown in FIG. 7 with the same reference numerals. Further, FIG. 2 is a waveform diagram showing waveforms at respective portions a to d shown in FIG.

Next, the operation will be described. First, the linear modulator 1 modulates a carrier with a modulation signal and outputs the modulated carrier to the variable attenuator 9 (FIG. 2 (a)). At the same time, the envelope component of the modulated signal is output to the comparison circuit 12 (FIG. 2 (b)). The modulated carrier wave is linearly amplified by the linear power amplifier 2 to become an amplified signal (FIG. 2 (c)), and is supplied to the transmitting antenna 7 through the directional coupler 3.

Further, the directional coupler 3 detects a traveling wave due to the amplified signal. Then, the level detector 4 converts the level of the traveling wave into a corresponding voltage (FIG. 2 (d)). The converted voltage is further scaled by a coefficient unit 11 using a coefficient according to a predetermined average transmission power. The predetermined average transmission power is predetermined in advance of transmission, and the information is used as scaling information, that is, as a coefficient.
11 is input from the outside. The output signal of the coefficient unit 11 and the envelope component of the modulation signal are input to the comparison circuit 12. Then, based on the comparison result, the variable attenuator 9 determines the amount (adjustment amount) to be attenuated so that the amplified signal has a value commensurate with the average transmission power, and outputs the determined amount as a control signal. . This control signal is input to the variable attenuator 9 as a control input after passing through the loop filter 8. Then, the variable attenuator 9 determines the amount of attenuation based on the control signal and adjusts the level of the modulated carrier wave, so that the amplified signal has a level commensurate with the average transmission power.

FIG. 3 is a block diagram showing a linear modulation radio transmitter according to the second embodiment of the present invention. In FIG. 3, 2a
Is a linear power amplifier with variable gain that can change gain while maintaining linearity. By using the linear power amplifier 2a whose gain can be adjusted in this way, the output of the loop filter 8 can be directly input to the linear power amplifier 2a.

FIG. 4 is a block diagram showing a linear modulation radio transmitter according to the third embodiment of the present invention. In FIG. 4, 11
a is a coefficient unit that scales the envelope component of the modulated signal by a coefficient according to a predetermined average transmission power. In this case,
The output signal of the level detector 4 is directly input to the comparison circuit 12. Although the envelope component of the modulated signal is scaled, the comparison circuit 12 outputs the adjustment amount as in the first and second embodiments, and the comparison circuit 12 outputs the adjustment amount as in the first and second embodiments. Has the same effect.

FIG. 5 is a block diagram showing a linear modulation radio transmitter according to the fourth embodiment of the present invention. In the first or second embodiment, the delay time of the level detector 4 and the coefficient unit 11 is sufficiently small, but if this delay time cannot be ignored, the configuration according to this embodiment is particularly useful. . That is, the delay compensation circuit 13 is provided between the linear modulator 1 and the comparison circuit 12, and the envelope component of the modulation signal input to the comparison circuit 12 is delayed by the delay compensation circuit 13 and compared with the output signal of the coefficient unit 11. The phase of the modulated signal input to the circuit 12 is matched with the envelope component.

FIG. 6 is a block diagram showing a linear modulation wireless transmission device according to the fifth embodiment of the present invention. In this embodiment, the envelope component of the modulated carrier wave output from the linear modulator 1 is detected by the level detector 14 and this detection signal is input to the comparison circuit 12. However, in the first embodiment, The same effect as the case is produced.

〔The invention's effect〕

As described above, according to the present invention, the linear modulation wireless transmission device is compared with the envelope component of the modulation signal and the envelope component of the amplified signal output by the power amplifier after adding information on a predetermined average transmission power. Since it is configured to control the input level or gain of the power amplifier according to the comparison result,
The average transmission power can be kept at a predetermined value without suppressing the envelope component of the linearly modulated carrier wave, and an effect suitable for burst transmission can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a linear modulation wireless transmission apparatus according to a first embodiment of the present invention, FIG. 2 is a waveform diagram showing waveforms in the main part of the one shown in FIG. 1, and FIGS. Are block diagrams showing linear modulation radio transmitters according to second to fifth embodiments of the present invention, FIG. 7 is a block diagram showing a conventional radio transmitter, and FIG. 8 shows an example of the configuration of a power amplifier. It is a block diagram. 1 is a linear modulator, 2 is a linear power amplifier (power amplifier), 4 is a level detector (level detecting means), 7 is a transmitting antenna, 9 is a variable attenuator (adjusting means), 11 is a coefficient unit (scaling means). , 12 are comparison circuits (comparison means). In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A linear modulator for generating a carrier wave linearly modulated by a modulation signal, a power amplifier for amplifying the linearly modulated carrier wave, and a transmitting antenna for sending an amplified signal output by the power amplifier as a radio wave. In a linear modulation wireless transmission device including: an adjusting means for adjusting an input level or a gain of the power amplifier; a level detecting means for detecting an envelope component of the amplified signal; and an envelope component of the modulated signal or the level detecting means. Output signal of
Scaling means for level conversion using a coefficient according to a predetermined average transmission power, and an envelope component of the modulated signal or the level of the output signal of the level detecting means and the level of the output signal of the scaling means Then, based on the comparison result, the adjusting means determines an adjustment amount for making the level of the amplified signal a value corresponding to the average transmission power, and gives a control signal indicating the adjustment amount to the adjusting means. A linear modulation wireless transmission device comprising: a comparison unit.