JP2008244986A - High frequency amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency amplifier in which communication quality is ensured by keeping constant the signal level of inter-modulation distortion of an amplifier for communication that operates in a high frequency domain, and high-efficiency operation can be performed with low power consumption even when an environmental temperature is changed. <P>SOLUTION: The high frequency amplifier comprises: an amplifier 2 which inputs high frequency power; a distortion level detection circuit 5 which defines branch output from the output line of the amplifier 2 as detection output; a comparator 6 which compares the detection voltage with a reference voltage; and a control circuit 7 to which the output voltage of the comparator 6 is input, and which includes a ROM in which a data table determining a supply voltage to the gate electrode and the drain electrode of the amplifier 2 in accordance with the output voltage of the comparator 6 is written in the inside. On the basis of ROM data, the drain voltage and the gate voltage of the amplifier 2 are controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a high-frequency amplifier that operates in a high-frequency region such as a microwave band.

  As an FET amplifier that minimizes deterioration of distortion characteristics with respect to changes in operating environment temperature, for example, in Japanese Patent Application Laid-Open No. 2003-224429, FIG. 1 (see Patent Document 1), the source terminal of an LDMOS FET 1 is grounded, and the gate A gate voltage Vgs is applied from the bias terminal 3 via the temperature compensation circuit 2 and the choke coil, and a drain voltage Vds is applied from the drain bias terminal 4 via the choke coil to operate as an amplifier.

    In FIG. 1 of Japanese Patent Laid-Open No. 7-202580 (see Patent Document 2), the gates of a signal amplification FET 1 and a control FET 2 are connected to each other, and the gate voltage is varied by a variable reference voltage generator. Control the current. The drain terminal of the FET 1 is connected to the output terminal, and the drain terminal of the FET 2 detects the amount of distortion using a bandpass filter and a peak detector that pass the frequency at which distortion occurs, and the voltage comparison amplifier has a certain amount of distortion. The variable reference voltage generator is controlled so as not to exceed. Therefore, the drain current of FET2 is always controlled so that the distortion characteristics are optimal, and as a result, FET1 also has the optimal drain current.

JP 2003-224429 A (FIG. 1)

JP-A-7-202580 (FIG. 1)

  However, in the device described in Patent Document 1, a thermistor (temperature sensor) is used as a temperature compensation circuit on the gate voltage Vg side of the amplifier, the gate voltage is changed according to the environmental temperature, and the current flowing through the amplifier is controlled. Although the temperature compensation circuit 2 is designed to improve efficiency, there is a variation in resistance values inherent in the resistance elements 21 and 22 and the thermistors 23 and 24, which makes it difficult to perform sufficient temperature compensation. .

  Moreover, in the thing of patent document 2, since a reference voltage (Vref) is input into one input terminal of the voltage comparison amplifier 6, and it does not operate | move when the signal from the peak detector 5 is smaller than Vref, it is a wide range. There was a problem that the operation over the range was impossible.

  The present invention has been made to solve the above-described problems. Communication quality is maintained by keeping the signal level of intermodulation distortion of a communication amplifier operating in a high frequency region such as a microwave and a millimeter wave band constant. It is another object of the present invention to provide a high-frequency amplifier that can operate with high efficiency and low power consumption even when the environmental temperature changes.

The high-frequency amplifier according to the first aspect of the present invention has a gate electrode and a drain electrode whose source electrodes are grounded, and is provided in an amplifier for inputting high-frequency power and an output line of the amplifier, and one of the branch outputs is high-frequency amplified. Distortion level that is connected to the control output line of the power distributor, and that extracts the nonlinear distortion generated in the amplifier and that is used as a detection output as an output line and the other branch output as a control output line The comparison circuit that outputs the differential voltage by using the detection circuit and the output voltage of the distortion level detection circuit as one input and the reference voltage corresponding to the desired high frequency output power set in advance as the other input, and this comparison The output voltage of the amplifier is inputted, the output is connected to the gate electrode and the drain electrode of the amplifier, respectively, and the gain of the amplifier corresponding to the output voltage of the comparator inside. A control circuit having a ROM in which a data table defining supply voltages for the first electrode and the drain electrode is written, and for a voltage value greater than the output voltage value of the reference voltage input to the comparator, the drain of the amplifier By decreasing the voltage and decreasing the gate voltage, for voltage values smaller than the output voltage value of the reference voltage input to the comparator, increasing the drain voltage of the amplifier and increasing the gate voltage, It operates while maintaining the output power corresponding to the reference voltage.

In the high frequency amplifier according to the invention of claim 2, the connection between the control circuit and the drain electrode of the amplifier, and the connection between the control circuit and the gate electrode of the amplifier are respectively n / 4 (n: 2. A positive odd number) through a stripline with an in-tube wavelength.

  As described above, according to the first aspect of the present invention, the drain voltage and the gate voltage are controlled in accordance with the preset distortion signal level corresponding to the input power, so that the output saturation power can be kept within a certain region. Output power can be maintained. In addition, by maintaining an appropriate back-off amount with respect to the distortion signal level, it is possible to obtain a high-frequency amplifier with good communication quality considering power efficiency and low power consumption even with respect to environmental temperature changes.

  According to the invention of claim 2, since the control circuit and the high frequency circuit are separated by the 1 / 4λg line in order to reduce the influence on the control circuit due to the leakage of the high frequency, the control signal due to the leakage of the microwave or the like. It is possible to alleviate malfunctions.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIG. FIG. 1 is a block configuration diagram of a high-frequency amplifier according to the first embodiment. In FIG. 1, 1 is an input terminal for inputting a high frequency input signal such as a microwave band, 2 is an amplifier composed of an FET transistor for amplifying the high frequency input signal, 3 is an output terminal for outputting an amplified high frequency signal, 4 is A power detection circuit 5 including a power distributor that allows the amplified signal amplified by the amplifier 2 to pass through and outputs a part of the amplified signal is received. The power detection circuit 5 receives the branch signal of the power detection circuit 4 and detects the branch signal. This is a level detection circuit. The distortion level detection circuit 5 generates an output voltage (Vdet) according to the branch signal level.

Reference numeral 6 denotes a comparator which receives the detected detection voltage (Vdet) as one input and inputs a reference voltage (Vref) from a reference voltage generator which can be arbitrarily set. A control circuit 7 receives an output voltage (Vcom) corresponding to a comparison result between Vdet and Vref compared by the comparator 6 and sends a control signal to the amplifier 2. The control circuit 7 previously stores the contents corresponding to the output voltage value of Vcom and has a storage element such as a ROM as a memory table, and the drain voltage (Vd) and gate voltage of the amplifier 2 corresponding to Vcom. (Vg) is generated, and the control voltage is supplied to the gate and drain of the amplifier 2.

  Next, the operation will be described. The data table written in the ROM of the control circuit 7 obtains the input / output power characteristics of the amplifier 2 in advance, and holds the optimum constants (backoff amount) of the drain voltage (Vd) and the gate voltage (Vg) of the amplifier 2. The optimum constant corresponds to the output voltage Vcom extracted from the magnitude of the detection voltage of the distortion level detection circuit 5 by extracting the distortion of the amplifier 2. A constant distortion signal level set in advance is maintained by controlling the drain voltage (Vd) and the gate voltage (Vg) corresponding to Vcom together.

FIG. 2 is a circuit diagram of the high-frequency amplifier according to the first embodiment. In FIG. 2, the high-frequency line through which the amplifier 2 is interposed and the Vd control signal and the Vg control signal from the control circuit 7 are (n / 4) × λg (n: an odd integer) in order to prevent high-frequency leakage. ) It is configured with a length and is separated by a microwave strip line whose back surface is a ground conductor. The drain voltage (Vd) of the amplifier 2 is supplied from the power supply (PS) of the control circuit 7 via a variable attenuator (VATT). Supplied directly. Similarly, the gate voltage (Vg) of the amplifier 2 is supplied from the PS of the control circuit 7 via the VATT, and is coupled to the high frequency line. Note that λg is the reciprocal of the high-frequency power frequency (f) and indicates the in-tube wavelength of the high-frequency transmission line to be conveyed.

Next, a method for setting optimum constants (backoff amounts) of the drain voltage (Vd) and the gate voltage (Vg) of the amplifier 2 will be described. FIG. 3 is an example showing the input / output characteristics of the amplifier 2. In FIG. 3, as the input power (P) gradually increases, the output power increases linearly in the low power region, but the output power saturates at a constant input power. At this time, by increasing or decreasing the drain voltage (Vd) of the predetermined amplifier 2, the output saturation power also changes with respect to a constant input voltage. That is, when Vd increases, the output saturation power increases, and when Vd decreases, the output saturation power also decreases. In general, when the gate voltage Vg of the amplifier is changed, the drain current (Ids) also changes. That is, when the gate voltage (Vg) increases, the drain current (Ids) also increases, and when Vg decreases, Ids also decreases.

FIG. 4 is a diagram for explaining input / output characteristics of the high-frequency amplifier due to environmental temperature changes and the like. In FIG. 4, the output saturation power increases at a low temperature and the output saturation power decreases at a high temperature with respect to the drain voltage (Vd) and gate voltage (Vg) of the predetermined amplifier at room temperature. This is because Ids increases because the gate voltage (Vg) increases at a low temperature with respect to a predetermined gate voltage (Vg) at room temperature. Conversely, at high temperatures, the gate voltage (Vg) decreases, so Ids also decreases.

From the above, for a voltage value larger than the output value of the reference voltage (Vref) input to the comparator 6, the drain voltage is decreased and the gate voltage is also decreased, which is smaller than the output value of the reference voltage input to the comparator 6. With respect to the voltage value, by increasing the drain voltage and the gate voltage, it is possible to increase the efficiency of the control speed as compared with the case of independent control.

Therefore, as shown in FIGS. 3 and 4, in order to maintain the specified output power (P ₀ ) that does not reach the output saturation power with respect to the input power and the environmental temperature change, the output saturation power (Psat) and the specified output By setting the back-off power amount that is the difference from the power (P ₀ ), a data table of Vd and Vg corresponding to this is created, and the distortion level detection circuit 5 at the specified output voltage (P ₀ ) Power control can be achieved by controlling the drain and gate of the amplifier 2 by the control circuit 7 based on the information.

That is, in order to make the distortion level constant, Vref corresponding to the specified output power (P ₀ ) is set, the backoff amount at this time is set to zero, and the backoff amount and the control voltage are set. Alternatively, when the power is set to be higher than the specified output power, the backoff amount is controlled to correspond to the increase or decrease of the input power or the like by setting the backoff amount to a specified value of +.

As described above, according to the first embodiment, by detecting only the distortion signal component without using the temperature compensation circuit, it is possible to maintain an appropriate back-off amount even when the input power and the environmental temperature fluctuate. It is possible to operate so as to maintain the output power.

In addition, since bias control is performed while keeping the distortion signal level constant, there is an effect that it is difficult to be affected by variations due to circuit constituent elements and stable communication quality can be maintained.

It is a block block diagram of the high frequency amplifier by Embodiment 1 of this invention. 1 is a circuit diagram of a high frequency amplifier according to Embodiment 1 of the present invention. FIG. It is a figure explaining the input-output characteristic of the high frequency amplifier of the high frequency amplifier circuit by Embodiment 1 of this invention. It is a figure explaining the input-output characteristic by the environmental temperature change etc. of a high frequency amplifier.

Explanation of symbols

1 ・ ・ Input terminal 2 ・ ・ Amplifier 3 ・ ・ Output terminal 4 ・ ・ Power detection circuit (Power distributor)
5 ・ ・ Distortion level detection circuit 6 ・ ・ Comparator 7 ・ ・ Control circuit

Claims (2)

The source electrode has a grounded gate electrode and drain electrode, and is provided in an amplifier that inputs high-frequency power, and an output line of this amplifier. One branch output is a high-frequency amplification output line, and the other branch output is a control output. A power distributor as a line, a distortion level detection circuit connected to the control output line of the power distributor, extracting a nonlinear distortion amount generated by the amplifier, and serving as a detection output, and an output of the distortion level detection circuit A comparator that outputs a differential voltage by using a voltage as one input and a reference voltage corresponding to a desired high-frequency output power set in advance as the other input, and an output voltage of the comparator are input, Connected to the gate electrode and the drain electrode of the amplifier, respectively, and supplied to the gate electrode and the drain electrode of the amplifier corresponding to the output voltage of the comparator inside A control circuit having a ROM in which a data table for determining a voltage is written, and for a voltage value larger than the output voltage value of the reference voltage input to the comparator, the drain voltage of the amplifier is decreased and the gate voltage is reduced. For the voltage value smaller than the output voltage value of the reference voltage input to the comparator, the output corresponding to the reference voltage is increased by increasing the drain voltage of the amplifier and increasing the gate voltage. A high-frequency amplifier that operates while maintaining power. The connection between the control circuit and the drain electrode of the amplifier, and the connection between the control circuit and the gate electrode of the amplifier are via a strip line of n / 4 (n: positive odd number) in-tube wavelength of the high frequency power frequency. The high-frequency amplifier according to claim 1.

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