JP2008312045A - Method for controlling transmission power, and transmission power controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To readily and moreover accurately change the maximum attenuation of a variable resistance attenuator and the transmission power which is less than the critical minimum detection power of a detector, and to change the transmission power at a high frequency band over a wide dynamic range. <P>SOLUTION: At least among local oscillation signal, intermediate frequency signal, and high-frequency signal in an image rejection mixer circuit 2 is changed with a phase changer 24, according to the transmission power detected by a closed loop transmission power control system 3; and accordingly, the power ratio of image signal to high-frequency signal is changed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a wireless communication apparatus used in the microwave / millimeter wave band, which does not depend on the use environment conditions, and which can vary the transmission power in the high frequency band with high accuracy and in a wide dynamic range. The present invention relates to a power control method and a transmission power control apparatus.

  In a wireless communication device using a microwave / millimeter wave band, it is required to expand a variable dynamic range of transmission power.

  As a method for varying the transmission power, the following method is generally widely used. Conventional example 1 shown in FIG. 9 and conventional example 2 shown in FIG. 10 are general block diagrams for transmission. In both cases, local oscillation signal (LO) from local oscillator 101 is multiplied by local oscillation multiplier 102. On the other hand, the input intermediate frequency signal (IF) is varied by the intermediate frequency band variable resistance attenuator 103 and synthesized by the mixer 104 to be converted into a microwave / millimeter wave high frequency signal (RF). This is amplified by the transmission power amplifier 105 to obtain a transmission output. At that time, the transmission power is varied by the high frequency band variable resistance attenuator 106 in the previous stage of the transmission power amplifier 105.

  The prior art example 1 shown in FIG. 9 controls the transmission power control in a closed loop. A transmission power detector 107 is provided at the subsequent stage of the transmission power amplifier 105, and the detected signal is received by the closed loop transmission power control circuit 108. This is realized by feeding back to the high frequency band variable resistance attenuator 106.

  However, the detection diode used in the transmission power detector 107 has a significant deterioration in detection accuracy especially at a high frequency and at a low output, which makes high-precision detection difficult, which has become a technical barrier. Furthermore, it is a disadvantage of this configuration that it is expensive and technically difficult, or requires a variable resistance attenuator with a wide dynamic range in the microwave / millimeter wave band.

  The conventional example 2 shown in FIG. 10 controls the intermediate frequency band variable resistance attenuator 103 to vary the input power at the intermediate frequency. In order to compensate with a loop, a transmission power control circuit 109 for controlling the high frequency band variable resistance attenuator 106 with an open loop is required. Therefore, in order to correct variations in individual elements, it is necessary to individually set control parameters, which not only leads to a decrease in productivity, but also to changes due to amplifier deterioration over time, element failures, etc. Correction was impossible at all.

  By the way, in recent wireless communication apparatuses, an apparatus using an image rejection mixer that suppresses an image frequency is increasing.

  Patent Document 1 (Japanese Patent Application No. 2003-426041, International Publication No. WO2005 / 062474) discloses a technique for controlling the output power of a local oscillation signal by a control signal corresponding to communication quality in an image rejection mixer. It is disclosed.

However, this is intended to vary the LO output while satisfying the condition of LO / RF power ratio = 1, and the LO power is varied by changing the phase according to the LO output change command. The output RF power is not varied.
Japanese Patent Application No. 2003-426041 (International Publication Number WO2005 / 062474)

  It is an object of the present invention to easily and accurately change the maximum attenuation of a variable resistance attenuator and the transmission power below the limit minimum detection power of the detector, and to change the transmission power in the high frequency band with a wide dynamic range. Another object of the present invention is to provide a transmission power control method and a transmission power control apparatus that can perform the above.

  The present invention combines a local oscillation signal and an intermediate frequency signal to generate a high-frequency signal, amplifies the image rejection mixer circuit that suppresses the image signal, and the transmission power of the output of the image rejection mixer circuit, In a wireless communication apparatus having a closed-loop transmission power control system that detects the transmission power and controls it in a closed loop, at least one phase of a local oscillation signal, an intermediate frequency signal, and a high-frequency signal in an image rejection mixer circuit Is varied according to the transmission power detected by the closed loop transmission power control system, and the power ratio between the image signal and the high frequency signal is changed.

When the phase in the image rejection mixer circuit is varied according to the transmission power, there are the following forms.
The phase of the intermediate frequency signal given a phase difference by the phase distributor in the image rejection mixer circuit is varied before being combined with the local oscillation signal.
The phase of the local oscillation signal distributed by the in-phase distributor in the image rejection mixer circuit is varied before being combined with the intermediate frequency signal.
The high frequency signal generated by the image rejection mixer circuit is varied before being synthesized by the phase synthesizer.

According to the present invention, in a variable range in which transmission power can be controlled with a desired accuracy, transmission power control is performed in the closed loop transmission power control system, and in the closed loop transmission power control system, depending on the performance of the transmission power detector. When the accuracy is not achieved and the transmission power is below the specified value, the phase of the local oscillation signal, intermediate frequency signal, and high frequency signal can be varied in the image rejection mixer circuit while controlling the detection voltage output to be constant. Then, by changing the image suppression ratio and changing the power ratio between the image signal and the high-frequency signal, the image of the image rejection mixer circuit at the maximum in addition to the transmission power control range in the closed-loop transmission power control system. The transmission power control range can be expanded by the amount of suppression.
Therefore, the maximum attenuation of the variable resistance attenuator and the transmission power equal to or lower than the limit minimum detection power of the detector can be easily varied with high accuracy and in a wide dynamic range.

  In addition, the power control area for phase change in the image rejection mixer circuit is basically realized by open loop control. However, the image rejection mixer circuit itself is a balanced type, so the effects of fluctuations in environmental factors such as temperature are affected. In addition, the gain control is performed so that the detected power is constant with respect to the deterioration over time of the elements on the output side of the mixer, such as a transmission power amplifier. Output correction and further failure detection can be easily realized.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a transmission power control apparatus according to a first embodiment of the present invention. This apparatus includes a local oscillator 1, an image rejection mixer circuit 2, a closed-loop transmission power control system 3 at the subsequent stage, and a band-pass filter 4 for suppressing unnecessary waves in the image band, as well as a closed-loop. A transmission power control circuit 5 and a phase control circuit 6 for varying the phase in the image rejection mixer circuit 2 under the control of the type transmission power control system 3.

  The image rejection mixer circuit 2 includes first and second mixers 21 and 22, a 90-degree phase distributor 23 and a phase variable unit 24 for the intermediate frequency band (IF), and a local oscillation frequency band (LO). It has an in-phase distributor 25 and a 90-degree phase synthesizer 26 for a high frequency band (RF).

  The IF signal inputted to the 90-degree phase distributor 23 is branched into two IF signals having a phase difference of 90 degrees, and the IF signal given the phase difference of 90 degrees is inputted to the first mixer 21 as it is. On the other hand, the IF signal that has not been given a phase difference is input to the phase variable unit 24, and the phase is varied.

  On the other hand, the LO signal from the local oscillator 1 is branched into two by the in-phase distributor 25, one of which is input to the first mixer 21 and synthesized with the IF signal given a phase difference of 90 degrees, and the other is The signal is input to the second mixer 22 and is combined with the IF signal whose phase is changed by the phase shifter 24.

  The RF signal generated by the first mixer 21 and the RF signal generated by the second mixer 22 are phase-synthesized by the 90-degree phase synthesizer 26 and output from the image rejection mixer circuit 2.

  The closed-loop transmission power control system 3 monitors a variable resistance attenuator 31 for variable gain, a transmission power amplifier 32, a transmission power detector 33 for a transmission power detection amount, and an input from the transmission power detector 33. The closed loop transmission power control circuit 34 can control the variable resistance attenuator 31.

  The transmission power control circuit 5 does not operate effectively in the variable range where the desired accuracy is obtained by the closed loop transmission power control circuit 34. However, if the desired accuracy is not obtained and the transmission power is below the transmission power, the phase control circuit 6 is activated. Thus, the phase variable device 24 in the image rejection mixer circuit 2 is varied.

The operation will be described using the transmission spectrum of FIG.
In order to realize a desired transmission output variable range with a high dynamic range, the output spectrum from the image rejection mixer circuit 2 is mainly composed of a desired RF signal and its signal as shown in a state 0 in FIG. It consists of an image signal having a level lower by the rejection ratio, and further an LO leakage signal.

  First, the lower limit transmission that can be easily realized from the viewpoint of detection accuracy and the dynamic range of the variable resistance attenuator 31 from the state 0 of the maximum transmission output at which the output of the transmission power detector 33 is maximum and the variable resistance attenuation amount is minimum Up to state 1 which is output power, the closed loop transmission output control circuit 34 controls the transmission output in the closed loop. The transmission output range obtained here is the transmission output control range (1) shown in FIG.

  Next, when realizing transmission power below the transmission output control range (1) obtained by the above closed loop control, using the phase variable device 24 provided in the image rejection mixer circuit 2, the transmission power is Variable with high accuracy over a wider range as follows.

  State 1 defined in FIG. 2 can be realized from state 2 to state 3 by varying the phase variable device 24 provided in the image rejection mixer circuit 2 from 0 degrees to 180 degrees. Specifically, by controlling the phase of the IF signal in an open loop, the image rejection ratio is controlled as shown in states 1 to 3 in the graph of FIG. What is important here is that the transmission power detector 33 detects all of the RF signal, the image signal, and the LO signal. Therefore, even when the image rejection ratio is controlled, the detection voltage hardly changes as shown in the graph of FIG.

  This means that even if the image rejection ratio is changed while maintaining the minimum output of the first closed loop, the transmission power detector 33 detects the sum of the transmission waves of all of the RF signal, the image signal, and the LO signal. Therefore, the entire power is controlled to be constant, and as a result, the change amount (deterioration amount) of the image rejection ratio can be considered as the change amount (absolute decrease amount) of the RF transmission signal. Finally, the bandpass filter 4 in FIG. 1 blocks the image signal and transmits only the RF signal, resulting in only the image rejection ratio, ie, the transmit power control range (2) shown in FIG. The variable dynamic range of transmission power can be expanded.

  Thus, in addition to the transmission output control range (1) by the transmission power detector 33 and the variable resistance attenuator 31, the transmission output control range (2) which is the image rejection ratio amount of the image rejection mixer circuit 2 is obtained. Only the transmission output range can be expanded.

  The transmission power control based on such image rejection change is theoretically highly accurate even when the transmission power range slightly changes due to a temperature change as shown in FIG. FIGS. 5A and 5B show simulation results when the temperature is changed. If the operation principle of the image rejection mixer is originally a differential type, the result can be easily inferred.

  Further, since the transmission power is controlled while detecting the sum of the transmission waves of all of the RF signal, the image signal, and the LO signal and maintaining the closed loop, environmental factors such as temperature fluctuation of the transmission power amplifier 32 are controlled. Therefore, it is possible to compensate for characteristic fluctuations and deterioration with time, or to detect such abnormalities.

  In consideration of the fact that the transmission output control range (1) in the microwave / millimeter wave band can be easily realized at about 30 dB, and the transmission output control range (2) based on the image rejection ratio can be easily realized at about 20 dB. The transmission output variable range can be easily secured.

  In the second embodiment shown in FIG. 6, the phase variable device 24 is provided between the in-phase distributor 25 and the second mixer 22, and the phase of one LO signal branched by the in-phase distributor 25 is varied. Thus, the same effect as in the first embodiment can be obtained.

  In the third embodiment shown in FIG. 7, the phase variable device 24 is provided between the first mixer 21 and the 90-degree phase synthesizer 26 so that the phase of the RF signal generated by the first mixer 21 is variable. Thus, the same effect as in the first embodiment can be obtained.

  In the fourth embodiment shown in FIG. 8, a 90-degree phase distributor 25a is used instead of the in-phase distributor 25 in the first embodiment shown in FIG. 1, and an in-phase phase synthesizer 26a is used instead of the 90-degree phase synthesizer 26. is there.

The phase variable device 24 does not need to change the phase continuously, and there is a method of switching in a switch manner.
In general, it may be difficult to realize a high-performance phase shifter, but the same effect can be achieved by switching the polarity of the 90-degree combiner / distributor using a switch.
In a simple manner, the same transmission power variable range can be obtained by a method of switching the polarity of each 90-degree phase distributor / combiner using an input / output switch or the like. Although there is a drawback that the transmission power control becomes discontinuous, in the case of an apparatus that does not need to continuously change the output power, the transmission output range can be easily expanded.

It is a block diagram which shows the structure of Example 1 of this invention. It is the figure explaining the operation | movement using the transmission spectrum. (A) is a graph which shows that transmission power changes by changing a phase with the phase variable device provided in the image rejection mixer circuit of FIG. (B) is a graph showing that the detection voltage of the transmission power detector hardly changes even if the phase is varied. It is a graph which shows that the relationship between IF input electric power and detection electric power is influenced by temperature. (A) is the same graph as FIG. 3 (A) which shows the simulation result when temperature is changed. (B) is the same graph as FIG. 3 (B). It is a block diagram which shows the structure of Example 2 of this invention. It is a block diagram which shows the structure of Example 3 of this invention. It is a block diagram which shows the structure of Example 4 of this invention. It is a block diagram which shows the structure of the prior art example 1. FIG. It is a block diagram which shows the structure of the prior art example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Local oscillator 2 Image rejection mixer circuit 3 Closed loop type transmission power control system 4 Band pass filter 5 Transmission power control circuit 6 Phase control circuits 21 and 22 1st and 2nd mixer 23 90 degree phase divider 24 Phase variable device 25 In-phase distributor 26 90-degree phase synthesizer 31 Variable resistance attenuator 32 Transmission power amplifier 33 Transmission power detector 34 Closed loop transmission power control circuit

Claims (8)

  The local oscillation signal and the intermediate frequency signal are combined to generate a high-frequency signal, and the image rejection mixer circuit that suppresses the image signal and the transmission power of the output of the image rejection mixer circuit are amplified, and the transmission power is In a wireless communication apparatus having a closed-loop transmission power control system that detects and controls in a closed loop, at least one phase of a local oscillation signal, an intermediate frequency signal, and a high-frequency signal in the image rejection mixer circuit is A transmission power control method characterized by varying a power ratio between an image signal and a high-frequency signal by varying the transmission power detected by a loop type transmission power control system.   2. The transmission power control method according to claim 1, wherein the phase of the intermediate frequency signal given a phase difference by the phase distributor in the image rejection mixer circuit is varied before being combined with the local oscillation signal.   2. The transmission power control method according to claim 1, wherein the phase of the local oscillation signal distributed by the in-phase distributor in the image rejection mixer circuit is varied before being combined with the intermediate frequency signal.   2. The transmission power control method according to claim 1, wherein the high frequency signal generated by the image rejection mixer circuit is varied before being synthesized by the phase synthesizer.   The local oscillation signal and the intermediate frequency signal are combined to generate a high-frequency signal, and the image rejection mixer circuit that suppresses the image signal and the transmission power of the output of the image rejection mixer circuit are amplified, and the transmission power is In a wireless communication apparatus having a closed-loop transmission power control system that detects and controls in a closed loop, the phase of at least one of a local oscillation signal, an intermediate frequency signal, and a high-frequency signal in the image rejection mixer circuit is varied A phase variable circuit, and a phase control circuit that controls the phase variable circuit in accordance with transmission power detected by the closed-loop transmission power control system, the power of the image signal and the high-frequency signal in the image rejection mixer circuit Transmission power whose ratio is detected by the closed loop transmission power control system In response transmission power control apparatus characterized by changing.   6. The phase varying device according to claim 5, wherein the phase of the intermediate frequency signal given a phase difference by the phase distributor in the image rejection mixer circuit is varied before being combined with the local oscillation signal. Transmission power control device.   6. The transmission power control according to claim 5, wherein the phase varying unit varies the phase of the local oscillation signal distributed by the in-phase distributor in the image rejection mixer circuit before being combined with the intermediate frequency signal. apparatus.   6. The transmission power control apparatus according to claim 5, wherein the phase varying unit varies the high-frequency signal generated by the image rejection mixer circuit before being synthesized by the phase synthesizer.

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