JP2000183762A - Transmission power control circuit, its control method and transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate a control range over a wide dynamic range through the use of closed loop control and open loop control while keeping the transmis sion S/N high without deteriorating a transmission noise figure. SOLUTION: An automatic level control circuit ALC in a microwave/ millimeter wave transmission power control circuit is provided with a variable gain amplifier section 1 whose gain is variable, a power amplifier section 3 with a fixed gain that amplifies power of an output of the variable gain amplifier section 1, and an attenuator 2 whose attenuation factor is controlled at a pre-stage of the power amplifier section 3. The variable gain amplifier section 1 is provided with a detection means 11 that detects a power level outputted from the power amplifier section 3 and with a gain control means 12 that compares a reference voltage with the detected level by the detection means 11 and outputs a control signal to control the gain of the variable gain amplifier section 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission power control circuit and a transmission apparatus for a radio transmitter and the like, and more particularly to a transmission power control having a high transmission S / N and a low transmission noise figure with high accuracy over a wide dynamic range. The present invention relates to a circuit and a transmission device.

[0002]

2. Description of the Related Art When a wide range of transmission power control is performed, transmission S
/ N (Signal to Noise Ratio) deteriorates. In particular, in the case of a high-speed signal transmission device, it is difficult to satisfy all of a wide signal band, appropriate transmission output power, low transmission distortion requirement, and good transmission NF.

Conventionally, as this type of transmission power control circuit, a closed loop system in which a part of a transmission output is detected and feedback is provided to a power amplifier by the detected output has been often used. It should be noted that such a closed loop system is used, for example, when applied to a TDMA transmitter or the like, the dynamic range of control of both the detection system and the power amplification system is narrowed, and burst-like transmission power is obtained. In this case, the rising and falling characteristics are difficult to increase in speed, and it is difficult to adjust the output in a wide range, and the stability including the temperature characteristics of the output is low when the output is small. In addition, overshoot or unnecessary oscillation may occur at the rise of the burst output.

To solve such a problem, Japanese Unexamined Patent Publication No. 5-152977 discloses a method for controlling a transmission output burst wave stably and highly accurately over a wide output range, which is used in a TDMA radio transmitter or the like. It states that it can.

FIG. 5 shows a configuration diagram of a transmission output control circuit according to this publication. In the figure, a part of the output of the transmission power amplifier 23 is extracted by the directional coupler 24 and input to the variable attenuator ATT25. The attenuation of the ATT 25 is controlled such that the attenuation changes in response to, for example, a 4-bit digital control signal input from the control signal input 31 of the control unit 30. Such a digital control signal is often sent from a base station. The output of the ATT 25 is input to the detector 27 via the high frequency amplifier 26. At this time, the attenuation of the ATT 25 and the amplification of the high-frequency amplifier 26 are controlled so that the input to the detector 27 becomes as constant as possible irrespective of the transmission output (P0). The output (Vdet) of the detector 27 and the reference voltage (Vref) are compared by a comparison error amplifier 29 composed of a successive comparator or the like, and the error voltage (V
cont) controls the output of the power amplifier 23.

The directional coupler 24, the variable attenuator 25, the high-frequency amplifier 26, the detector 27, the comparison error amplifier 29, and the transmission power amplifier 23 form a (feedback) closed loop of a detection system. The reference voltage (Vre
f) has a burst-like shape like the reference waveform 28, and its peak value is given by the control unit 30 as a voltage that changes according to the transmission power P0. The ATT 25 and the high frequency amplifier 26 form a variable amplifier.

According to the transmission output control circuit described above, a variable attenuator is inserted after the transmission output coupling section, in addition to the closed loop control in which the control sensitivity of the detection system is kept constant with respect to a change in the transmission output. By changing the control sensitivity of the power amplifier 23 by combining two sets of loops in which a variable output level drive amplifier is placed in front of the power amplifier 23 and the drive level is controlled in an open loop, the transmission output control can be performed for all output levels. Control with a constant control sensitivity.

[0008]

However, in the above publication, it is considered that the dynamic range of the power adjustment of the transmission power is widened and the control sensitivity is widened.
Preventing deterioration of transmission S / N (Signal to Noise Ratio) due to deterioration of transmission NF (Noise Figure), wide signal band in case of high-speed signal transmission device, appropriate transmission Output power, low transmission distortion, good transmission NF, etc. could not be satisfied.

The present invention solves the above problems by controlling the closed loop and the open loop while maintaining the transmission S / N high without deteriorating the transmission noise figure NF, and thereby achieving a wide dynamic range control. The task is to compensate the range.

[0010]

SUMMARY OF THE INVENTION The present invention provides a microwave
In a millimeter wave transmission power control circuit, an automatic output control circuit (ALC), the automatic output control circuit varies a gain, and a fixed gain power amplifier amplifies an output of the variable gain amplifier. And a controllable attenuator having a predetermined attenuation degree at a stage preceding the power amplifying unit,
The variable gain amplifying unit detects a power level output from the power amplifying unit, and outputs a control signal for controlling a gain of the variable gain amplifying unit by comparing a detection result of the detecting unit with a reference voltage. And a gain control means.

The present invention is also directed to a microwave / millimeter wave transmitting apparatus, wherein the microwave / millimeter wave high-frequency input signal is input and the gain is changed by a DC control signal; An attenuator switch that passes the output of the amplifying unit at a positive voltage and attenuates the output of the attenuator switch by a predetermined amount at a negative voltage; a power amplifying unit that amplifies the power of the output of the attenuator switch; A demultiplexing unit to be extracted, an output level detection circuit unit for converting the control signal into a DC component, and detection by the output level detection circuit unit based on a reference voltage for setting a power output level of the power amplification unit to a predetermined value. Gain control means for outputting a DC control signal in comparison with the obtained DC value, and an attenuator switch for varying the transmission output power of the power amplification section by a fixed width by a switch signal supplied to a control terminal. When, wherein the band-pass filter to the output of the power amplifier and the desired band, the more becomes that the antenna for radiating the microwave and millimeter-wave high-frequency signals that have passed through the band-pass filter.

Further, the present invention relates to a transmission power control method for controlling transmission power of microwaves and millimeter waves, comprising: an automatic output control circuit (ALC); and a variable gain amplifying section for varying a gain by the automatic output control circuit. A power amplifier having a fixed gain that amplifies the output of the variable gain amplifier, detects an output level of the power amplifier, converts the output level into a DC voltage corresponding to the output level, The gain of the variable gain amplifying unit is controlled in accordance with a difference from a voltage, and a predetermined attenuator is provided at an anterior stage of the power amplifying unit. The output power of the power amplifying unit is controlled according to a voltage. In a microwave / millimeter wave transmitter, a transmission output power control circuit constitutes an automatic output control circuit (ALC), and a transmission having a variable gain amplifier and a (fixed gain) amplifier to constitute the ALC circuit. The transmitter has a wide transmission output power control range and good distortion characteristics, and is equipped with an attenuator switch capable of obtaining a fixed width attenuation in order to prevent deterioration of the transmission S / N ratio. , The operating point of the attenuator switch lowers the transmission output power,
The transmission S / N ratio is set so as not to exceed the reference value.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described.
This will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing the configuration of a transmission power control apparatus according to the first embodiment. The transmission power control device includes a variable gain amplifying unit 1, an attenuator switch 2, a power amplifying unit 3, a demultiplexing unit 4, a mixer unit 5, a local oscillation signal unit 10, an output level detection circuit unit 11, and an amplification gain. It comprises control means 12.

Here, the output signal of the mixer section 5 is input to the amplification gain control means 12 through the output level detection circuit section 11. Also, the reference voltage Vre input from the terminal 102
The gain of the variable gain amplifying unit 1 is controlled such that the transmission output power becomes the transmission power corresponding to the reference voltage by comparing with f1. With the closed loop circuit configuration, an automatic output control circuit (ALC circuit) is formed.

In addition to the closed circuit configuration of the ALC circuit, an attenuator switch control means 20 for turning the attenuator switch 2 ON and OFF is provided, and the transmission output power is varied with a fixed width by the voltage of the control terminal 103. The attenuator switch 2 is always
It is used at one of two voltages set at the set voltage supply terminals 111 and 112.

The signal input from the terminal 101 is
After passing through the bandpass filter 6 through the power amplifier 3, the signal is output from the antenna 7. When the antenna is used for both transmission and reception, it goes without saying that the band-pass filter 6 functions as a duplexer.

[Explanation of Operation of this Embodiment] A baseband signal to be transmitted is converted into a high-frequency signal, and is converted into a desired transmission frequency signal by a local oscillation signal from a local oscillator (not shown). The transmission frequency signal is input to terminal 101,
The high-frequency signal whose amplification gain is controlled by the variable gain amplifying unit 1 and output from the power amplifying unit 3 is separated by a demultiplexing unit such as a directional coupler having a permissible coupling amount (for example, −20 dB) of transmission output power loss. The signal is branched at 4 and input to the down-conversion mixer unit 5. After being converted into a low-frequency signal by the mixer unit 5, the signal power is detected by the output level detection circuit unit 11, becomes a DC value, and enters the amplification gain control unit 12.

The output level detection circuit section 11 includes a mixer section 5
Is converted to a DC component using a logarithmic IC for RSSI detection in accordance with the low-frequency signal level of the output of, and is used as a detection value. Alternatively, a detector constituted by a diode may be used.

These DC value outputs are supplied to the amplification gain control means 1.
At 2, the voltage is compared with the reference voltage Vref1 input from the terminal 102. This reference voltage Vref1 corresponds to a set target value of the transmission output power. By changing the reference voltage Vref1 from outside, the transmission output power can be varied.

When the control range of the transmission output power is wide, the attenuator switch 2 is switched at a certain set point in the control range. Assuming a case where the transmission output maximum state is set to the attenuation amount 0 dB and the transmission output is reduced, first, the attenuator switch 2 is ON, that is, only the gain of the variable gain amplifying unit 1 is reduced in the pass mode, but with this. The transmission output S / N ratio deteriorates. The attenuator switch 2 is switched at a switching set point determined by the required value of the transmission spectrum mask and the required value of the transmission distortion characteristic. At the switching point, the attenuator switch 2 is OFF, that is, the attenuation mode, and the gain of the variable gain amplifier 1 becomes equal to the initial state. Thereafter, the attenuator switch 2 is in the OFF state, and the variable gain amplifier 1
Will be lowered.

[0022]

Next, an embodiment according to the present invention will be described specifically.

As an example, the radio carrier frequencies 18 to 2
This embodiment will be described using a transmission unit of a microwave communication device that allows a data transmission rate of 150 Mbps in a band of about 6 GHz. Assuming that the signal band is 40 MHz, 30 dB
It is assumed that the transmission output control width is required. It is assumed that the required transmission spectrum mask is 80 MHz away from the carrier frequency and the required / unwanted wave ratio is 50 dB. The required value of the transmission spectrum mask is ETSI (Europe
This is a value indicating a permissible value of a required wave / unwanted wave of each band in a transmission spectrum described in an Telecommunication Standards Institute (ETS 300-431) standard.

In order to satisfy the required value of the transmission spectrum mask, it is necessary that the NF of the transmission section is good. Because, in the frequency band as assumed now, the band-limited BPF (Band Pass Filter) or DUPL
This is because it is difficult to suppress unnecessary waves 80 MHz apart and obtain a signal band of 40 MHz by using the EXER. Since it is considered that transmission S / N = transmission gain + transmission NF, transmission NF becomes a problem if the transmission output is controlled to lower the transmission gain.

Still, when the transmission output control width is small, for example, about 10 to 15 dB, the transmission unit NF rarely causes a problem. Or if the signal bandwidth is narrow,
For example, if the transmission speed is about several Mbps, the transmission unit NF
Is rarely a problem. However, when trying to transmit a high-speed signal such as 150 Mbps, the required signal bandwidth naturally increases. As a result, the thermal level increases, so that the NF characteristic required for the transmission unit becomes stricter than in the case of low-speed signal transmission.

Here, the case where the signal bandwidth is 5 MHz and the case where
When comparing the case of 0 MHz, the thermal level is 9 dB
Therefore, the transmission unit NF must be good by 9 dB.

In addition, when the control range of the transmission output power is wide, the transmission NF has a considerable effect. When a transmission output control width of 30 dB is required, if the signal is attenuated near the input, that is, at a low gain, the transmission NF will be degraded, and the required value of the transmission spectrum mask cannot be satisfied. For example, in the present embodiment, if the gain of the variable gain amplifying unit 1 is reduced while the attenuator switch 2 is kept ON (pass mode), the transmission NF deteriorates, and therefore the transmission S / N ratio deteriorates. The required value of the transmission spectrum mask cannot be satisfied.
Configuration B in FIG. 2 corresponds to this.

In order not to deteriorate the transmission NF, it is necessary to insert an attenuator as close as possible to the final stage of the amplifier. Ideally, it should ideally be inserted between the power amplifier 3 and the bandpass filter 6. However, the passing loss of the attenuator directly leads to a decrease in transmission output power. In particular, it is often difficult to increase the output power of the amplifier in the frequency band as described in the description example here. It is not desirable from the viewpoint of power consumption. Therefore, inserting an attenuator before the power amplifying unit 3 has a great merit for the whole system. The attenuator switch 2 of the present invention corresponds to this. By inserting an attenuator here, the gain up to the attenuator switch 2 can be increased.
Deterioration of transmission NF can be suppressed.

A point to be noted here is the transmission distortion characteristic. When performing high-speed signal transmission at 150 Mbps or the like, the transmission unit is required to have good distortion characteristics. Transmission output power = + 18 dBm, gain of power amplification unit 3 is 8 dB,
Assuming that the required third-order intermodulation (IM3) distortion value is a required wave / unwanted wave ratio = 40 dB, the distortion characteristic of the PIN diode becomes a value that cannot be ignored when the input power is more than +10 dBm, and does not satisfy the required transmission distortion value. . Especially several dB
In the case of the attenuation amount (about 3 to 8 dB), the distortion characteristic of the attenuator is most deteriorated. Therefore, the use of an attenuator at this operating point has a problem in distortion characteristics and should be avoided. Here, for example, a specific circuit diagram of the present attenuator 2 is shown in FIG.
Shown in A predetermined attenuation can be obtained according to the voltage applied to the PIN diode. When a positive voltage is applied, a predetermined degree of attenuation is obtained, and when a negative voltage is applied, a high-frequency signal is passed.

Therefore, when the attenuator switch 2 is ON (passing mode), it is used as a cutout. For example, in the case of a P-type diode that operates as an attenuator in a direction in which a PIN diode applies a positive voltage and a current flows, a negative voltage is applied.
Thereby, the passage loss of the attenuator is reduced and distortion characteristic deterioration is prevented. Conversely, attenuator switch 2 is OFF (attenuation mode)
At times, it is used as a complete. Specifically, if the voltage of the terminal 111 is set to about +5 V and the voltage of the terminal 112 is set to about −5 V and the attenuator switch (PIN diode switch) is operated with either voltage, the operation is performed almost completely or completely. Is possible. That is, the operating point at which the distortion characteristic of the attenuator is most deteriorated is used.

FIG. 2 shows a comparison between the transmission S / N ratio and the transmission distortion characteristics under the conditions of a signal input power of -25 dBm, a signal output power of +18 dBm, and a transmission power control width of 30 dB. In FIG. 2, the configuration A is the transmission power control circuit of the present invention. Here, the transmission power control amount 15 dB is calculated as the switching set point of the attenuator switch 2. Configuration B shows a case where only the gain of the conventional transmission power control circuit, that is, the variable gain amplifying section 1 is changed.

[Second Embodiment] FIG. 3 is a block diagram showing a transmission power control apparatus according to a second embodiment of the present invention.
This is a case where the transmission frequency is low and the output level can be detected without using the mixer unit 5, and the mixer unit 5 is omitted from FIG.

The transmission power control apparatus includes a variable gain amplifying section 1 which receives a microwave high frequency input signal and varies the gain by a DC control signal, and a -15d negative voltage which passes through a positive voltage.
An attenuator switch 2 for attenuating about B, a power amplifying section 3 for about 15 dB, a demultiplexing section 4 such as a directional coupler for extracting a control signal, and an output level detection circuit for converting the control signal into a DC component An amplification gain control unit 12 that outputs a DC control signal based on a reference voltage 102 that sets the power output level of the power amplification unit 3 to a predetermined value, based on a reference voltage 102; Switching between a positive voltage 111 and a negative voltage 112 for varying the transmission output power with a fixed width according to the voltage of the control terminal 103, and turning the attenuator switch 2 on and off.
Attenuator switch control means 20, a band-pass filter 6 for setting the output of the power amplifier 3 to a desired band, and an antenna 7 for radiating a microwave high-frequency signal passing through the band-pass filter 6.

Here, as described above, FIG.
Assuming that the signal input power input to 01 and the output power of the microwave high-frequency signal of the power amplifier 3 are -25 dBm and the transmission power control width is 30 dB, the transmission S / N ratio (dB) and 9 shows a comparison of transmission distortion characteristics of the modulation component IM3. In FIG. 2, configuration A is the transmission power control circuit of the present embodiment. Here, the transmission power control amount 15 dB is calculated as the switching set point of the attenuator switch 2 by supplying the positive and negative voltages of the switching control signal by the attenuator switch control means 20.
Configuration B shows a case where only the gain of the conventional transmission power control circuit, that is, the variable gain amplifier 1 is changed.

[0035]

According to the present invention, by providing a closed-loop and an open-loop control circuit in the transmission power control device, the degradation of the transmission noise figure NF can be reduced, the transmission S / N can be kept high, and the dynamic range can be maintained. A wide control range.

Further, according to the present invention, a transmission apparatus having a wide control range of transmission output power and excellent distortion characteristics is provided. In addition, in order to prevent deterioration of transmission S / N, a fixed width attenuation amount is reduced. The operating point of the attenuator switch is set so that the transmission S / N ratio does not exceed the reference value when the transmission output power is reduced. It is possible to obtain high quality and flexible transmission power in a severe radio wave environment.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a transmission power control device according to an embodiment of the present invention.

FIG. 2 is a graph illustrating an operation / action according to the present invention.

FIG. 3 is a configuration block diagram of a transmission power control device.

FIG. 4 is a partial configuration diagram of a transmission power control device according to an embodiment of the present invention.

FIG. 5 is a configuration block diagram of a conventional transmission power control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable gain amplifier 2 Attenuator switch 3 Power amplifier 4 Demultiplexer 5 Mixer 6 Band pass filter 7 Antenna 11 Output level detection circuit 12 Amplification gain control means 20 Attenuator switch control means 102 Reference voltage 103 Control terminal 111 Positive Voltage 112 Negative voltage

Claims (7)

[Claims] 1. A microwave / millimeter wave transmission power control circuit, comprising: an automatic output control circuit (ALC); a variable gain amplifying section for varying a gain by the automatic output control circuit; and an output of the variable gain amplifying section. A power amplifying unit having a fixed gain for amplifying power, and a controllable attenuator having a predetermined attenuation degree at a stage preceding the power amplifying unit, wherein the variable gain amplifying unit detects a power level output from the power amplifying unit. A transmission power control circuit, comprising: a detection unit that performs a control signal for controlling a gain of the variable gain amplifying unit by comparing a detection result of the detection unit with a reference voltage. . 2. The transmission power control circuit according to claim 1, wherein said detection means detects a part of the output of said power amplification section and converts the output to a low frequency signal by a mixer for mixing with a local oscillation signal of a local oscillator. A transmission power control circuit for converting the low frequency signal into a DC component. 3. The transmission power control circuit according to claim 1, wherein the reference voltage in the gain control means is a voltage at which an output of the power amplifying unit has a desired value, and the attenuator is an attenuator. A transmission power control circuit characterized in that a control signal of a positive voltage is applied when the degree is 0, and a negative voltage is applied when the degree of attenuation is a predetermined degree of attenuation. 4. A microwave / millimeter wave transmitting apparatus, comprising: a variable gain amplifying unit that receives a microwave / millimeter wave high frequency input signal and varies a gain by a DC control signal; and an output of the variable gain amplifying unit. An attenuator switch that passes a positive voltage and attenuates a predetermined amount by a negative voltage, a power amplifying unit that amplifies the output of the attenuator switch, and a demultiplexer that is connected to an output of the power amplifying unit and extracts a control signal. An output level detection circuit unit that converts the control signal into a DC component; and a DC value detected by the output level detection circuit unit based on a reference voltage that sets a power output level of the power amplification unit to a predetermined value. An amplification gain control unit that outputs a DC control signal as compared with a control signal; an attenuator switch that varies a transmission output power of the power amplification unit with a fixed width by a switch signal supplied to a control terminal; A band-pass filter to the output of the force amplifying unit and a desired band, microwave and having passed through the band-pass filter
A transmitting device comprising an antenna that radiates a millimeter-wave high-frequency signal. 5. The transmission device according to claim 4, wherein the output level detection circuit section detects the output of the demultiplexing section, and mixes the output signal with a local oscillation signal of a local oscillator to generate a low-frequency signal. A mixer for converting the signal, an output level detection circuit for converting the low-frequency signal into a DC component, and an amplification gain for outputting the DC control signal for varying the gain of the variable gain amplifier in accordance with an output of the output level detection circuit. A transmission device comprising a control unit. 6. The transmission device according to claim 4, wherein a transmission output power of said power amplification unit is varied with a fixed width by a voltage of said control terminal, and said attenuator switch is set by two set voltage supply terminals. The transmitter being used at one of two voltages. 7. A transmission power control method for controlling microwave / millimeter wave transmission power, comprising: an automatic output control circuit (AL);
C), a variable gain amplifier for varying the gain by the automatic output control circuit, and a fixed gain power amplifier for power amplifying the output of the variable gain amplifier, and detecting an output level of the power amplifier. Then, the output voltage is converted into a DC voltage corresponding to the output level, the gain of the variable gain amplifying unit is controlled in accordance with the difference between the DC voltage and the reference voltage, and a predetermined attenuation is turned on before the power amplifying unit. A transmission power control method, comprising: providing an attenuator that performs a through operation, controlling the attenuator, and controlling an output power of the power amplification unit according to the reference voltage.