JP2009232253A - Transmission power control device for wireless apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission power control device for a wireless apparatus which enhances alternator noise without damaging a transmission power stabilization time. <P>SOLUTION: Transmission power is detected with the output of a transmission final amplifier, and an AC noise component included in the detection output is extracted and added to a power control voltage. When controlling the transmission power by comparing the power control voltage with the detection output, the AC noise component included in the detection output is canceled with the AC noise component added to the power control voltage. Further, when the transmission rises, the AC noise component is neither added nor canceled but after the transmission power is stabilized, the AC noise component is added and canceled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transmission power control apparatus for a radio.

  For example, in an FM radio device, as disclosed in Patent Document 1, a transmission power control device is provided to set transmission power (transmission output level) to a target value.

  FIG. 4 is a block diagram of a transmission circuit unit of a conventional FM radio. In the transmission power control, 11 is a transmission final amplifier, 12 is a transmission / reception changeover switch, 13 is an antenna filter, and 14 is an antenna. An output terminal, 15 is a power detection unit (transmission power detection circuit), 16 is a transmission power control circuit (hereinafter referred to as APC unit), and 17 is a D / A converter controlled by the CPU 18.

  In this FM radio, the voltage (transmission power) detected by the power detection unit 15 is input to the APC unit 16 and the power control voltage (power control signal, maximum power control signal) output from the D / A converter 17 By comparing and controlling the gate bias voltage of the transmission final amplifier 11 with the comparison result, the transmission power is set to the target value.

  At this time, if the gate bias voltage of the transmission final amplifier 11 is controlled by the power control voltage output from the D / A converter 17, the transmission power can be basically set to the target value. Since the relationship between the gate bias voltage and the transmission power greatly changes depending on the temperature or the like, the transmission power is detected inside the wireless device and compared with the power control voltage from the D / A converter 17, and the transmission final amplifier 11 It is necessary to apply feedback to the gate bias voltage.

  Therefore, the circuit of the power detection unit 15 is optimized so that the transmission power does not attenuate even when the load of the antenna output terminal 14 fluctuates. In addition, the response characteristic of the voltage control loop is optimized so that the circuit stabilizes instantaneously at the rise and fall of the transmission power. Furthermore, there is no abnormal oscillation.

  FIG. 5 is a specific circuit example of the conventional APC unit 16, and the power control signal output from the D / A converter 17 is amplified by the first stage differential amplifier 161 and then output from the D / A converter 17. By comparing the maximum power control signal with the second stage differential amplifier 162, a final power control voltage is generated. This power control voltage is supplied to the positive input of the final stage differential amplifier 163. On the other hand, the voltage detected by the power detector 15 is amplified by the differential amplifier 164 and then supplied to the negative input of the final stage differential amplifier 163. Then, the power detection voltage supplied to the minus input and the power control voltage supplied to the plus input are compared by the final stage differential amplifier 163, and the gate bias voltage of the transmission final amplifier 11 is controlled by the comparison result. Set the transmission power to the target value.

Here, the two signals (power control signal and maximum power control signal) output from the D / A converter 17 are used as power control voltages in order to strictly adjust the transmission power. At the time of adjustment, with the power control signal set to the maximum voltage of the D / A converter 17, the voltage of the maximum power control signal is adjusted to determine the maximum transmission power. Thereafter, the voltage of the power control signal is lowered to adjust the target transmission power.
JP-A-9-205334

  By the way, in the case of an FM in-vehicle wireless device, since the transmission power is large, a battery voltage is used as the power source of the transmission final amplifier 11. At this time, if there is in-vehicle noise (alternator noise) of the AC component in the battery voltage, AM modulation is applied, and the voltage detected by the power detector 15 varies due to the noise. The gate bias operates so as to suppress the AM modulation by reversing the AC component noise in the APC unit 16, but at this time, if the transmission final amplifier 11 has the characteristic that the delay amount varies due to the gate bias voltage variation, the FM Modulation is applied. Furthermore, since the delay amount fluctuates, the AM modulation component cannot be reliably suppressed, so that the gate bias voltage remains fluctuated with the noise frequency. This causes a problem that noise in the audible band can be heard on the FM receiver side even though transmission is performed without modulation.

  Therefore, audible noise is reduced by inserting a low-pass filter in the gate bias line and power detection line to stabilize the gate bias voltage. In this method, the transmission power rises and falls. There is a problem that it takes time until the power stabilizes (excessive transmission power). This is fatal in the trunking operation.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a transmission power control device for a radio that can improve alternator noise without impairing the transmission power stabilization time.

  The transmission power control apparatus for a radio of the present invention includes a detection means for detecting transmission power from an output of a transmission final amplifier, an extraction means for extracting an AC noise component included in the output of the detection means, and the AC noise component. Output means for outputting after the transmission power stabilizes after a lapse of a predetermined time after rising of transmission power, addition means for adding the AC noise component to the power control voltage, and comparison between the output of the detection means and the power control voltage Comparing means for controlling the transmission power of the transmission final amplifier according to the result and canceling the AC noise component with the AC noise component added to the power control voltage is provided.

  As a more preferred form, the amount of cancellation of the AC noise component is adjusted by adjusting the gain of the differential amplifier as the adding means. Furthermore, when the addition of the AC noise component to the power control voltage is started by the adding means, the output section of the extracting means is arranged so that the DC voltage state of the adding means becomes unstable, and as a result, the transmission power is not violated. The DC bias means is connected to.

  According to the radio transmission power control apparatus of the present invention as described above, the AC noise component included in the transmission power detection output is extracted, added to the power control voltage, and the detection output and the power control voltage are compared. Since the AC noise component included in the detection output is canceled by the AC noise component added to the power control voltage, the alternator noise can be improved. Furthermore, since the AC noise component is not added or canceled when the transmission power rises, and the AC noise component is added or canceled after the transmission power is stabilized, the transmission power stabilization time can be shortened.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a radio transmission power control apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram showing an embodiment, and 21 is a transmission final amplifier for amplifying a transmission signal. The transmission signal amplified by the transmission final amplifier 21 is radiated as a radio wave from the antenna 22. Reference numeral 23 denotes a power detection unit that detects transmission power from the output of the transmission final amplifier 21. The output of the power detector 23 is supplied to the plus input of the differential amplifier 24. A resistor 25 is connected between the output of the differential amplifier 24 and the negative input. The negative input is grounded through the resistor 26. The output of the differential amplifier 24 is connected to the negative input of the final stage differential amplifier 28 via a resistor 27. A resistor 29 is connected between the output of the final stage differential amplifier 28 and the negative input. The output of the differential amplifier 24 is connected to one end of a capacitor 30 as AC noise component extraction means. The other end of the capacitor 30 is connected to the drain of an FET 32 as output means via a resistor 31. Further, the DC bias means 33 is connected to the other end of the capacitor 30. The DC bias means 33 is composed of a series circuit of resistors 331 and 332 connected between a power supply voltage and the ground, and a connection point between the resistors 331 and 332 is connected to the other end of the capacitor 30. The power control signal output from the D / A converter 17 of FIG. 4 is supplied to the negative input of the first stage differential amplifier 35 via the resistor 34. A resistor 36 is connected between the output of the first stage differential amplifier 35 and the negative input. Further, the midpoint of the series circuit of the resistors 37 and 38 connected between the power supply voltage and the ground is connected to the plus input of the first stage differential amplifier 35. The output of the first stage differential amplifier 35 is connected to the negative input of the second stage differential amplifier 40 via a resistor 39. A resistor 41 is connected between the output of the second stage differential amplifier 40 and the negative input. The maximum power control signal output from the D / A converter 17 of FIG. 4 is supplied to the plus input of the second stage differential amplifier 40. The output of the second stage differential amplifier 40 is connected to the plus input of the final stage differential amplifier 28. The output of the final stage differential amplifier 28 is supplied to the transmission final amplifier 21 in order to control the gate bias voltage and the transmission power. The output of the final stage differential amplifier 28 is connected to the gate of the FET 32 via the resistor 42. A capacitor 43 is connected between the gate of the FET 32 and the ground. The source of the FET 32 is connected to the negative input of the first-stage differential amplifier 35 as an adding means and an amplifying means.

  In the device configured as described above, the power control signal is amplified by the first stage differential amplifier 35 and further compared with the maximum power control signal by the second stage differential amplifier 40, whereby the final power control voltage is obtained. Output from the second stage differential amplifier 40. This power control voltage is supplied to the positive input of the final stage differential amplifier 28. Further, the transmission power is detected by the power detection unit 23 and the detection voltage is amplified by the differential amplifier 24 and then supplied to the negative input of the final stage differential amplifier 28. The final stage differential amplifier 28 compares the detection voltage with the power control voltage, and the comparison result is supplied to the transmission final amplifier 21 to control the gate bias voltage of the amplifier 21 so that the transmission power becomes the target value. Set to

  Further, the AC noise component included in the transmission power detection voltage output from the power detection unit 23 is extracted from the output of the differential amplifier 24 by the capacitor 30. Then, since the extracted AC noise component is supplied to the negative input of the first stage differential amplifier 35 via the FET 32, the AC noise component is supplied to the power control signal (by extension, the second stage differential amplifier 35). Power control voltage output from the stage differential amplifier 40). Therefore, when the power control voltage and the transmission power detection voltage are compared by the final stage differential amplifier 28, the AC noise component included in the transmission power detection voltage is canceled by the AC noise component added to the power control voltage, It does not appear in the output of the final stage differential amplifier 28. Therefore, the influence of the AC noise component when controlling the transmission power is prevented.

  FIGS. 2A to 2C are waveform diagrams showing the state of the AC noise component at the input and output of the amplifier when the gain of the final stage differential amplifier is 0 dB. FIG. 2A shows a case of a conventional method without an AC noise component canceling function. FIGS. 2B and 2C show the case of the above apparatus having an AC noise component canceling function, and FIG. 2B shows the case where the positive input side of the final stage differential amplifier 28 is set to −12 dB on the negative input side. FIG. 2C shows a case where the positive input side of the final stage differential amplifier 28 is set to −6 dB on the negative input side. In the case of the final stage differential amplifier 28 having a gain of 0 dB in the above-described apparatus of the present invention, as shown in FIG. 2 (c), if a common-mode voltage of −6 dB amplitude is applied to the positive input side with respect to the negative input side amplitude, The output AC noise component can be completely removed. When the values of the resistors 34 and 36 connected to the first stage differential amplifier 35 are adjusted to adjust the gain of the first stage differential amplifier 35, the input state shown in FIG. And the influence of the AC noise component can be eliminated.

  In this way, the influence of the AC noise component is removed. However, when the transmission power rises after switching to the transmission state, the AC noise component is not added or canceled, and the AC noise component is turned on when the transmission power is stabilized. Addition to the control voltage starts AC noise component cancellation. That is, when the transmission power rises after being switched to the transmission state, the gate bias voltage rises from 0 V to the target voltage, but the gate voltage of the FET 32 is applied by the resistor 42 and the capacitor 43 with a delay, so that the OFF state It becomes. Therefore, the AC noise component extracted by the capacitor 30 is not supplied to the first stage differential amplifier 35 via the FET 32, is not added to the power control voltage, and is not canceled by the final stage differential amplifier 28. On the other hand, the AC noise component extracted by the capacitor 30 is supplied to the first-stage differential amplifier 35 via the FET 32 by setting the resistor 42 and the capacitor 43 so that the FET 32 is turned on after the transmission power rises and stabilizes. Are added to the power control voltage, and cancellation is started in the final stage differential amplifier 28. In this way, the transmission power stabilization time can be shortened by prohibiting addition and cancellation of AC noise components when the transmission power rises.

  If the DC voltage state of the first stage differential amplifier 35 becomes unstable when the FET 32 is turned on and the addition of the AC noise component is started by the first stage differential amplifier 35, the FET 32 is supplied to the final stage differential amplifier 28. In the above apparatus, the DC bias voltage is applied by the DC bias means 33 on the output side of the capacitor 30 because the gate control voltage fluctuates greatly and the transmission power becomes violent. (That is, the voltage between the drain and the source of the FET 32 is kept the same). Moreover, at this time, the constant ratio of the resistors 331 and 332 of the DC bias means 33 is equal to the constant ratio of the resistors 37 and 38 connected to the amplifier plus input so that the DC component is not amplified by the first stage differential amplifier 35. Make the same. Furthermore, the constant is made as small as possible in order to speed up the convergence of the detected waveform.

  FIG. 3A shows the measurement results of each voltage when no DC bias voltage is applied, and FIG. 3B shows the measurement results of each voltage when a DC bias voltage is applied. When the DC bias voltage shown in FIG. 3 (a) is not applied, the gate bias voltage is greatly shaken when the FET 32 is turned on (a portion in FIG. 3 (a)), and the transmission power becomes unclear. This measurement is set so that the FET 32 is turned on after about 120 mS from the rise of the transmission power. Even when there is no FET 32, or when an attempt is made to stabilize the gate bias voltage by adding only LPF, the gate bias voltage may be disturbed at the rising edge of transmission. On the other hand, when the DC bias voltage of FIG. 3B is applied, it can be seen that the gate bias voltage hardly fluctuates (a portion of FIG. 3B).

  Although one embodiment has been described above, according to this apparatus, AC noise components can be removed without impairing the transmission power stabilization time, and the noise can be canceled even at a low frequency such as an audible band as well as the alternator noise. . Furthermore, it is possible to prevent the transmission power from being rampant.

The circuit block diagram which shows one Embodiment of the transmission power control apparatus of the radio | wireless machine of this invention. The wave form diagram which shows the state of the AC noise component in the input and output of this amplifier when the gain of the last stage differential amplifier is 0 dB. The wave form diagram which shows the measurement result of each voltage when not applying a DC bias voltage, and when applying a DC bias voltage. The block diagram of the transmission circuit part of the conventional FM radio. The circuit diagram which shows the specific circuit example of the conventional APC part.

Explanation of symbols

21 Transmission final amplifier 23 Power detector 28 Final stage differential amplifier 30 Capacitor 32 FET
33 DC bias means 35 First stage differential amplifier 40 Second stage differential amplifier

Claims (3)

Detection means for detecting transmission power at the output of the transmission final amplifier;
Extraction means for extracting an AC noise component contained in the output of the detection means;
Output means for outputting the AC noise component after the transmission power has stabilized after a predetermined time has elapsed since the rising of the transmission power;
Adding means for adding the AC noise component to a power control voltage;
Comparison means for controlling the transmission power of the transmission final amplifier according to a comparison result between the output of the detection means and the power control voltage, and canceling the AC noise component with the AC noise component added to the power control voltage;
A radio transmission power control apparatus comprising:   2. The transmission power control apparatus for a radio according to claim 1, wherein the amount of cancellation of the AC noise component is adjusted by adjusting a gain of a differential amplifier as the adding means.   When the addition of the AC noise component to the power control voltage is started by the adding means, the DC voltage state of the adding means becomes unstable, and as a result, the output power of the extracting means is not DC 3. The radio transmission power control apparatus according to claim 1, further comprising a bias unit connected thereto.

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