JPH06112849A - Transmission signal level controller for radio transmitter - Google Patents

Abstract

PURPOSE:To realize a control of a transmission signal level of the TDMA system radio transmitter with simple configuration. CONSTITUTION:A control section 9 outputs a communication signal and its level designation signal for each time slot. A level control signal generating circuit 4 generates a level control signal in response to the level designation signal and outputs the signal to a level control circuit 2 via a D/A converter circuit 5. The modulated communication signal is level-controlled by the level control circuit 2, amplified by an RF amplifier circuit 3 and the amplified signal is outputted to the outside. The output level is detected by a detection circuit 8, fed back to the level control signal generating circuit 4 via an A/D converter circuit 7 and a detection characteristic storage circuit 6 to correct the level control signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission signal level control device for a radio transmitter, and more particularly to a device for controlling the output level of a base station transmitter in a TDMA mobile communication system.

[0002]

2. Description of the Related Art In a TDMA type mobile communication system, a base station transmitter needs to change the transmission level for each time slot so that a constant level signal is input to mobile station receivers at various positions. is there. As shown in FIG. 4, the conventional transmission signal level control device outputs the output of the modulation circuit 1 to the level control circuit 2 according to the voltage value of the level control signal generated by the level control signal generation circuit 12 based on the level designation signal. Was controlled by. A sudden change in the signal level spreads the transmission spectrum, so a level control signal that changes the signal level smoothly must be generated. Therefore, the level control signal generation circuit 12 has a configuration as shown in FIG. That is, in the reference voltage generation circuit 120, the output of the decoder 121 switches the analog switch 122 by the input level designation signal (plural bits), and the resistor 12 is turned on.
The output voltage is changed by changing the division ratio of 3 (Fig. 5 (b)).
Vd), and the low-pass filter (LPF) 125 smoothed the voltage change (see Vs in FIG. 5C).

Further, it is necessary to control the gain in order to correct the change in the transmission level due to the change in the gain of the RF amplifier circuit 13 due to temperature change or the like. Conventionally, as shown in FIG. 4, the input level of the RF amplifier circuit 13 is set to the first level.
The comparison circuit 10 compares the result of detection by the detection circuit 11 and amplification by the predetermined gain of the RF amplification circuit 13 with the result of detection of the output level of the RF amplification circuit 13 by the second detection circuit 8. The gain of the RF amplifier circuit 13 is controlled so as to be equal.

[0004]

In order to change the transmission level so that the spectrum of the transmission signal does not spread,
A smooth-changing waveform as shown in FIG. 2 is required as the level control signal. Therefore, the reference voltage generation circuit 1
20 needs to generate many intermediate reference voltages in addition to the reference voltage as shown in FIG. But each resistor 12
Since there are variations in the resistance value of 3, these reference voltages,
It was difficult to realize the intermediate reference voltage with high accuracy.

In addition, with the change of the transmission level, the first
Although the range of levels that the detection circuit 11 and the second detection circuit 8 must detect is wide, the detection characteristics of the first detection circuit 9 and the second detection circuit 8 are wide over a wide level range.
A complicated adjustment circuit was required to match the detection characteristics of.

[0006]

A transmission signal level control device for a radio transmitter according to the present invention controls a communication signal from the outside according to a reference timing signal for each time slot and outputs a level designation signal and a detection timing signal. A circuit and a modulation circuit that outputs a radio frequency signal by modulating a communication signal output from the control circuit,
A level control circuit that controls the level of the output signal of the modulation circuit according to the level control signal, an RF amplification circuit that amplifies the output of the level control circuit and outputs the signal as a transmission signal to the outside, and a reception timing signal when receiving the detection timing signal. Level detection means for detecting the level of the output signal of the RF amplification circuit and outputting a transmission signal level signal, and the level of the output signal of the RF amplification circuit is predetermined based on the level designation signal and the transmission signal level signal. And a level control signal generating means for generating the level control signal so as to attain the level.

Further, in the above structure, the level detecting means detects the output level of the RF amplifier circuit when the detection timing signal is received, and the A / D converter for A / D converting the output voltage of the detector circuit. Conversion circuit and A / D
The correspondence between the output value of the conversion circuit and the output level of the RF amplification circuit is stored in advance, the output level of the RF amplification circuit is determined from the given output of the A / D conversion circuit, and the signal is output as the transmission signal level signal. A configuration including a detection characteristic storage circuit may be used.

[0008]

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

FIG. 1 is a block diagram showing an embodiment of the present invention. The transmission signal level control device according to the present embodiment distributes a digital communication signal including a control signal input via a communication line for each time slot according to a reference timing signal, and a 3-bit level designation signal and a detection timing signal. , A modulation circuit 1 for digitally modulating the communication signal to output a radio frequency IF transmission signal, and a level for controlling the output level of the IF transmission signal according to an analog level control signal. A control circuit 2, an RF amplifier circuit 3 that amplifies a level-controlled IF transmission signal and outputs it as an RF transmission signal, a level of the RF transmission signal is detected when the detection timing signal is received, and an analog detection level signal is output. Detection circuit 8
And the detection level signal as analog / digital (A / D)
The A / D conversion circuit 7 for converting and the correspondence between the value of the digital detection level signal and the level of the RF transmission signal are stored in advance, and the level of the RF transmission signal signal is discriminated from the given detection level signal to determine the transmission signal level. A detection characteristic storage circuit 6 for outputting as a signal, a level control signal generation circuit 4 for generating a digital level control signal by adding a correction by a transmission signal level signal based on a level designation signal, and a level control signal for digital / analog (D / D). A) D / to convert
And an A conversion circuit 5. The D / A conversion circuit 5 is the conventional reference voltage generation circuit 1 shown in FIG.
Similar to 20, the analog switch may be switched to change the resistance division ratio.

The output of the RF amplifying circuit 3 is carrier-combined with the output of another RF amplifying circuit (not shown) and is transmitted through a power amplifier and a transmitting antenna (both not shown).

Next, the operation will be described.

The level control signal generation circuit 4 has an arithmetic function and generates a digital output level control signal which sequentially changes from a level designation signal for each time slot until it reaches a predetermined value by calculation, and the signal is D / A. Conversion circuit 5
The signal is D / A converted by, and the level control circuit 2 controls the output signal (IF transmission signal) level of the modulation circuit 1 (see FIG. 2). Further, the output level of the RF amplification circuit 3 at the detection timing, that is, the RF transmission signal level is detected by the detection circuit 8, and the output is A / D converted by the D / A conversion circuit 7 and input to the detection characteristic storage circuit 6. To be done. The detection characteristic storage circuit 6 stores the detection characteristic of the detection circuit 8,
The transmission output level can be determined from the output of the A / D conversion circuit 7. The determination result (transmission signal level signal) is input to the level control signal generation circuit 4. The level control signal generation circuit 4 compares the signal level to be output with the detection level, and if there is a difference between them, corrects the level control signal and outputs it. The level control signal in this case is as shown in FIG.

[0013]

As described above, according to the present invention, the level control signal generating means for producing the analog level control signal from the digital level designating signal receives the feedback of the device output signal and outputs the corrected level control signal. Since the output is performed, unlike the conventional example, there is no need to be affected by variations in analog elements or a complicated adjustment circuit for adjusting the output of two different detection circuits is required, and the transmission level control accuracy can be improved with a simple configuration. A high transmission signal level control device can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a level control signal waveform.

FIG. 3 is a diagram showing an example of a corrected level control signal waveform.

FIG. 4 is a block diagram of a conventional transmission signal level control device.

5A and 5B are diagrams for explaining a conventional level control signal generation circuit, FIG. 5A is a block diagram, FIG. 5B is an output waveform diagram of a reference voltage generation circuit, and FIG. 5C is an output waveform diagram of a low-pass filter. Is.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Modulation circuit 2 Level control circuit 3,13 RF amplification circuit 4,12 Level control signal generation circuit 5 D / A conversion circuit 6 Detection characteristic storage circuit 7 A / D conversion circuit 8, 11 Detection circuit 9 Control circuit 10 Comparison circuit 120 Reference voltage generation circuit 121 Decoder 122 Analog switch 123 Resistor 125 Low pass filter (LPF)

Claims (2)

[Claims] 1. A control circuit that distributes a communication signal from the outside for each time slot according to a reference timing signal and outputs a level designation signal and a detection timing signal, and a communication signal output from this control circuit is modulated to wirelessly A modulation circuit that outputs a frequency signal, a level control circuit that controls the level of the output signal of the modulation circuit according to a level control signal, and an RF amplification that amplifies the output of this level control circuit and outputs it as a transmission signal to the outside. A circuit, level detection means for detecting the level of the output signal of the RF amplifier circuit when receiving the detection timing signal and outputting a transmission signal level signal, and the RF based on the level designation signal and the transmission signal level signal. Level control for generating the level control signal so that the level of the output signal of the amplifier circuit becomes a predetermined level A transmission signal level control device for a wireless transmitter, comprising: a signal generation means. 2. The level detecting means includes a detection circuit for detecting the output level of the RF amplification circuit when the detection timing signal is received, and an A / D conversion circuit for A / D converting the output voltage of the detection circuit. The correspondence between the output value of the A / D conversion circuit and the output level of the RF amplification circuit is stored in advance, and the output level of the RF amplification circuit is judged from the given output of the A / D conversion circuit to determine the transmission signal level signal. 2. The transmission signal level control device for a wireless transmitter according to claim 1, further comprising a detection characteristic storage circuit for outputting as.