JPH03280727A - Transmission power control system - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a transmitter and to control the transmission power against the fluctuation of a reception level by decreasing a bias voltage of an amplifier normally and increasing a bias voltage of the amplifier at fading only. CONSTITUTION:When a reception level detection section at a receiver side detects a level reduction, the section sends control information to an interface circuit 51 of a sender side. A bias voltage control circuit 52 changes slowly a bias voltage of an amplifier from a steady-state value to a value at a high output by using control information received by the circuit 51. Moreover, upon the receipt of information representing the decrease in the reception level, an input level control circuit 54 changes the input level of the amplifier at a speed not causing a code error to increase the transmission power. furthermore, a distortion generating quantity control circuit 53 controls the distortion compensation circuit simultaneously. Thus, the power consumption is reduced without causing a code error to control the transmission power.

Description

[Detailed Description of the Invention] [Industrial Application Field] In fixed microwave communication, the present invention is characterized by reducing power consumption in a transmitter and controlling the transmission level on the transmitting side according to changes in the receiving level on the receiving side. The present invention relates to a transmission power control method.

[Conventional technology]

Current fixed microwave systems can only output a fixed value of transmission power within the legally permitted range, and therefore transmission power control systems have not been put into practical use. On the other hand, in the satellite communication system, a method has been proposed in which the bias of the transmission power amplifier is changed to increase the transmission power due to a drop in the reception level during rain. For example, JP-A-1
According to No. 170227, the bias state of an amplifier is switched and controlled in two stages by comparing the signal level of a beacon signal, pilot signal, etc. received at an earth station with a reference level.

[Problem to be solved by the invention]

In the case of fixed microwave communication systems, the reception level decreases due to fading, but this fading is frequency selective fading. It is generally independent of the reception level of the wireless channel. It also has no correlation with the reception level of radio waves transmitted in the opposite direction. For this reason, the situation is completely different from the reception level drop characteristics during rain in the satellite communication system.

In addition, in the case of fixed digital microwave communication systems, in order to increase frequency usage efficiency, unlike satellite communication systems, signal information is also included in the amplitude component, and the reception level changes faster than in the case of rain. It is extremely difficult to control the bias voltage and input level of a high-power amplifier simultaneously and at high speed. Furthermore, in fixed digital microwave communication systems, a circuit that compensates for the nonlinear distortion of the amplifier is usually inserted in the transmitting section, and when changing the operating point of the amplifier, it is necessary to control this compensation circuit at the same time. This makes control even more difficult.

In addition, with the current fixed microwave system, the transmission power can only be output at a fixed value within the legally permitted range, so it is necessary to take into account the drop in reception level during fading, and to increase the transmission power level with a considerable margin. is set. As a result, the power consumption of the transmitter increases, and measures to reduce this are desired.

Based on the above points, the present invention monitors the reception level in a fixed microwave communication system against fading that fluctuates at high speed, transfers this information to the transmitting side, and first controls the bias voltage of the amplifier on the transmitting side. The purpose of this invention is to provide a practical transmission power control method that does not cause code errors (and also reduces power consumption) by controlling the input level based on the above.

[Means to solve the problem]

According to the present invention, a reception level detection unit on the reception side monitors the reception level, and information according to the result is sequentially transferred to the transmission side. In response to this, on the transmitting side, the bias voltage and input level of the amplifier are controlled according to the procedure shown below, and the transmission power level is increased only during fading to ensure line quality.

(1) First, when the reception level drops below a certain predetermined reception level (L1), that information (L1 information) is transferred to the transmitting side. On the transmitting side, the bias voltage of the high-output amplifier is increased and maintained for a specified period of time. If further Ll information comes within this holding time, from that point on, the bias voltage is further increased and held for a certain period of time.

At this time, a distortion compensation circuit is also controlled in order to compensate for nonlinear distortion of the input/output characteristics of the amplifier due to changes in the bias voltage.

(2) Further, when the reception level decreases and becomes lower than the predetermined reception level (L2), the information (L2 information) is transferred to the transmitting side. On the transmitting side, the input level of the high-output amplifier is raised to a certain level. At this time, the input level is set with a necessary time constant so as not to affect the operating characteristics of the AGC circuit and demodulator on the receiving side. In addition to input level control, it also controls the distortion compensation circuit.

■ When the receiving level recovers on the receiving side and reaches the specified receiving level (L3), the information (L3 information) is transferred to the transmitting side. On the transmitting side, the input level of the high-output amplifier is lowered to the steady state level. At this time, the input level is set with a necessary time constant so as not to affect the operating characteristics of the AGC circuit and demodulator on the receiving side.

In addition to input level control, it also controls the distortion compensation circuit. At this time, the receiving level will drop by the amount that the transmitting level has been raised, but on the transmitting side, the bias voltage of the amplifier will continue to be raised for a certain period of time, so that the receiving level will be low.
If it does not fall below l, the bias voltage is returned to its normal value.

■ In addition, when controlling the transmission power by increasing the input level of the amplifier, a function to prevent malfunction is provided, such as controlling the bias voltage of the amplifier to always be selected at a high value.

For reference in the above explanation, FIG. 1 shows the control state of the amplifier on the transmitting side and the control state of the transmission level depending on the reception level situation. Furthermore, FIG. 2 shows how the input/output characteristics of the high-output amplifier change during transmission power control.

〔Example〕

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

FIG. 3 is a block diagram showing an embodiment of a wireless communication device to which the present invention is applied. 1 and 17 are antennas 2 and 18 are duplexers, 3 and 19 are reception high frequency filters, 4 and 20 are frequency conversion sections, 5 and 21 are intermediate frequency amplification sections, 6 and 22 are AGC sections, 7 and 23 are Demodulator, 8 and 24 are reception level detection sections, 9 and 25 are high frequency filters for transmission, 10 and 26 are FET power amplification sections, 11 and 27 are distortion compensation circuit sections, 12 and 28 are frequency conversion sections, 13 and 29 is an intermediate frequency amplification section, 1
4 and 30 are modulation sections, 15 and 31 are demodulation sections, and 16 and 32 are transmission power control sections. FIG. 4 is a detailed diagram of the transmission power control section 16 or 32, 51 is an interface circuit that translates control information and connects to each control circuit, 52 is a bias control circuit that controls the bias voltage of the amplifier, and 53 is a distortion compensation circuit. A distortion generation amount control circuit controls the circuit, and 54 is an input level control circuit. Next, the operation of the wireless communication device with the above configuration will be explained assuming that the transmitting side is station A and the receiving side is station B. First, a reception input signal received by the antenna 17 is converted to an intermediate frequency band (IF band) through a duplexer 18, a reception high frequency filter 19, and a frequency converter 20.

The received signal in the intermediate frequency band is then input to the demodulating section 23 via the intermediate frequency amplifying section 21 and the AGC section 22. The reception level detection unit 24 outputs transmission level control information using the AGC voltage indicating the reception power level, and this control information is inserted into a control circuit created by adding bits to the main signal sequence in the demodulation unit 31. , modulation section 30, intermediate frequency amplification section 29, frequency conversion section 28, distortion compensation circuit section 27
, FET power amplification section 26, high frequency transmission filter 25,
After passing through the transmitter/receiver duplexer 18 and the antenna 17, the source A
Transferred to the station side. On the A station side, this control information is input to the demodulator 7 via the antenna 1, the duplexer 2, the reception high frequency filter 3, the frequency converter 4, the intermediate frequency amplifier 5, and the AGC section 6, where it is input to the demodulator 7. Separated from signal line. The transmission power control unit 16 controls the transmission power level using this separated control information. First, each control is performed according to a control signal received by the interface circuit 51. 1111 circuit. Based on the L1 information, the bias voltage control circuit 52 slowly changes the bias voltage of the amplifier from the steady state value to the high output value and waits.0 Next, when the L2 information is received, the input level control circuit 54 changes the amplifier bias voltage to the high output value. To increase transmission power by changing the input level at a speed that does not cause code errors. In each control step in the transmission power control section 16 described above, the distortion generation amount control circuit 53 similarly controls the amplitude and phase component of the distortion generated to compensate for nonlinear distortion within the distortion compensation circuit 11.

〔Effect of the invention〕

As explained in detail above, in fixed microwave communication, the bias voltage of the amplifier is lowered during steady state operation.
By increasing the bias voltage of the amplifier only during fading, which occurs at a very small rate of time, the power consumption of the transmitter is reduced, and conventional methods cannot be applied to high-speed fluctuations in the received electric field level due to fading, etc. This enables a transmission power control method that controls bias voltage, which was not possible before.

[Brief explanation of drawings]

Fig. 1 is a state diagram of reception, transmission levels and high power amplifier during fading to explain the control procedure according to the present invention, and Fig. 2 is an input characteristic and state diagram of the high power amplifier to explain the control procedure according to the present invention. , FIG. 3 is a block diagram showing an embodiment of a wireless communication device according to the present invention, and FIG. 4 is a block diagram showing an embodiment of a transmission power control section. 1.17---Antenna, 2.18---One transmitter/receiver duplexer, 8.24---One reception level detector, 10.2
6---FET high output amplifier, 16.32---1 transmission power control section, 17.27---distortion compensation circuit section ill Reception level τ (3) Measure the transmission level 1°tμ3. [Mu time S [^ I'l1 Figure output level Figure 2

Claims (1)

[Claims] In a method for controlling transmission power in a fixed microwave communication system, the received power level is set to a certain level (
If the voltage drops below L1), the transmitting side switches the bias voltage of the high-output power amplifier using a field-effect transistor (FET), resets the amplifier's nonlinear distortion compensation, and waits for a certain period of time. When the power level drops below a certain level (L2:L2<L1), the power consumption of the transmitter and the transmission power level can be reduced by controlling the input level of the high-output amplifier and the amount of nonlinear distortion compensation. A transmission power control method characterized by changing the transmission power.