JPH0671182B2 - Frequency conversion amplifier - Google Patents

Description

The present invention relates to a frequency conversion / amplification device in which temperature characteristics and frequency characteristics of a device gain are compensated by an open loop.

[Conventional technology]

With the downsizing of equipment in recent years, a transmission frequency conversion amplification device (HPC = High Power Conv
on the receiving side, a low noise frequency conversion amplification device (LNC = Low Noise Converter) that integrates a low noise high frequency amplifier and a reception frequency conversion unit (down converter) is used in a small earth station for satellite communication. ing. FIG. 6 is a block diagram of a conventional HPC. In the figure, (1) is an up converter, (2) is a variable attenuator such as a PIN diode for adjusting device gain, (3) is a high frequency amplifier, and (4) is (3) A temperature sensor such as a thermistor that detects the ambient temperature in the vicinity, and (5) is a bias current control circuit that controls the bias current of (2) according to the detected temperature of (4).

Next, the operation will be described. The IF input signal is frequency-converted to the RF band by the up converter (1) and is high-frequency amplified by the high-frequency amplifier (3). The high frequency amplifier (3) is usually constructed by connecting semiconductor amplifier elements such as gallium arsenide (GaAs) FETs in multiple stages, but generally has a temperature characteristic that the high frequency gain decreases as the ambient temperature rises. In order to reduce this temperature characteristic, the temperature sensor (4) such as a thermistor is used to detect the ambient temperature in the vicinity of the high frequency amplifier (3), and when the ambient temperature rises, the attenuation amount of the variable attenuator (2) is reduced. As described above, the bias current control circuit (5) controls the bias current of the variable attenuator (2) to perform temperature compensation of the gain of the entire device. 14GH with temperature compensation shown in Fig. 7.
An example of the temperature characteristic and frequency characteristic of the gain of the Z-band high frequency amplifier will be shown. (In this example, 10 source-grounded GaAs field effect transistors are connected in stages.) From Fig. 4, the temperature variation of the gain is improved to about 1/3 by performing temperature compensation, but It can be seen that the frequency characteristic is not improved at all.

[Problems to be solved by the invention]

Since the conventional transmission frequency conversion / amplification device is configured as described above, the temperature variation of the device gain is compensated, but the frequency characteristic is not improved, and the amplitude equalizer includes the up converter (1) and the high frequency amplifier ( Although it is necessary to additionally compensate for the frequency characteristic during 3), the amplitude equalizer generally has a drawback that the adjustment becomes complicated. As another means, there is a method of compensating for both temperature fluctuation of gain and frequency characteristic by feedback control, but when the input carrier is intermittent like SCPC or TDMA, a variable attenuator is used while the input carrier is disconnected. The attenuation of (2) is minimized and the input carrier wave is turned on.
In this case, an excessive output is generated from the high frequency amplifier (3).

The present invention has been made to solve the above-mentioned problems, and in addition to the temperature characteristic compensation of the device gain in the conventional device, without using the amplitude equalizer or the feedback control,
An object is to obtain a transmission frequency conversion / amplification device that compensates for frequency characteristics.

[Means for solving problems]

The transmission frequency conversion amplifier device according to the present invention uses a control voltage to a voltage controlled oscillator (hereinafter referred to as VCO) used as a local oscillator of an up converter, and inputs this VCO control voltage to a polygonal line approximation circuit. The output voltage of the broken line approximation circuit and the output voltage of the temperature sensor are added, and this added voltage is added to the bias current control circuit that controls the amount of attenuation of the variable attenuator, and the frequency characteristics and temperature characteristics of the high frequency gain of the device are Both are compensated.

[Action]

The polygonal line approximation circuit (6) in the present invention receives the VCO control voltage proportional to the RF output frequency of the device as an input, outputs the correction amount of the frequency characteristic of the high frequency amplifier (3), and outputs the attenuation amount of the variable attenuator (2). To decide.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, (1) to (5) are the same as the conventional example shown in FIG. (6) is a polygonal line approximation circuit that receives the VCO control voltage obtained from the up-converter (1), and (7) is an addition that adds the output voltage of the temperature sensor (4) and the polygonal line approximation circuit (6). It is a vessel. FIG. 2 shows a block diagram of the upconverter. In the figure, (11) is an IF amplifier, (12) is a first stage mixer, (13) is a first local oscillator,
(14) is a band pass filter for suppressing the image frequency appearing at the output of the first-stage mixer (12), (15) is an amplifier for level adjustment between stages, (16) is a second-stage mixer, and (17) is a voltage. Controlled oscillator (VCO), (18) is a synthesizer for setting the output frequency, (19) is a phase discriminator (PSD) that compares the output frequency of the VCO (17) with the output frequency of the synthesizer (18), (20 ) Is a loop filter, (21) is a VCO (17)
A directional coupler for branching a part of the output of (2), and (22) is a bandpass filter for suppressing the image frequency appearing at the output of the second stage mixer.

Next, the operation will be described. In FIG. 7, for example, +
To flatten the frequency characteristic of gain at 25 ° C,
The correction attenuation amount as shown in the figure may be determined for each RF frequency, and the frequency characteristic of gain is improved as shown in FIG. In FIG. 1, a polygonal line approximation circuit (6) operates to give an approximate value of the correction attenuation amount shown in FIG. 3 to a variable attenuator (2) such as a PIN diode via a bias current control circuit (5). That is, the VCO control voltage obtained from the output of the loop filter (20) of the up converter (1) is given to the input of the broken line approximation circuit (6), and this VCO control voltage is set to the RF output frequency of the device. It is proportional. Therefore, in FIG. 3, the frequency on the horizontal axis corresponds to the VCO control voltage, and the correction attenuation amount on the vertical axis corresponds to the output voltage of the polygonal line approximation circuit (6). As can be seen from FIG. 3, the correction amount of the frequency characteristic of the high-frequency amplifier can be approximated by a straight line, so that a polygonal line approximation circuit can be easily realized by a circuit using an operational amplifier and a diode as well known.

Although the variable attenuator (2) is provided between the up converter (1) and the high frequency amplifier (3) in the above embodiment, the high frequency amplifier (3) is connected to the IF input terminal of the up converter (1). The variable attenuator (2) may be provided anywhere between the output stages of.

Further, in the above embodiment, the case of the transmission frequency conversion amplification device (HPC) in which the up converter and the high frequency amplifier are integrated has been described, but the low noise frequency conversion device (LNC) in which the low noise amplifier and the down converter are integrated is described. It may be applied to the temperature compensation of the gain and the compensation of the frequency characteristic, and has the same effect as that of the above-mentioned embodiment. The circuit diagram is shown in FIG.

〔The invention's effect〕

As described above, according to the present invention, since the frequency conversion / amplification device is configured to perform the temperature compensation of the device gain and the compensation of the frequency characteristic by the open loop, the configuration of the device is simplified, and when the feedback control is used. The drawbacks of can be eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a transmission frequency conversion / amplification device according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of an up converter section in the device of the present invention, and FIG. 3 is a frequency characteristic correction. FIG. 4 is an example diagram showing the amount of attenuation, FIG. 4 is an expected diagram of the characteristic after the frequency characteristic of the gain according to the present invention is corrected in the conventional device, and FIG. 5 is a low noise frequency showing another embodiment of the present invention. FIG. 6 is a block diagram showing the configuration of the conversion device, FIG. 6 is a block diagram of a conventional transmission frequency conversion amplification device, and FIG. 7 is an example diagram showing temperature fluctuation of gain and frequency characteristics of a 14 GHz high frequency amplifier. In the figure, (1) is an up converter, (2) is a variable attenuator, (3) is a high frequency amplifier, (4) is a temperature sensor,
(5) is a bias current control circuit, (6) is a broken line approximation circuit, (7) is an addition circuit, (8) is a low noise amplifier, and (9).
Is a down converter. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A high frequency amplifier comprising a transmission frequency converter (up converter) of a type for controlling the oscillation frequency of a local oscillator by a synthesizer, a high frequency amplifier, and a variable attenuator for controlling the gain of the entire apparatus. A temperature sensor that detects the temperature in the vicinity of the high-frequency amplifier is provided, and an adder that adds the output voltage of the temperature sensor and the voltage-controlled oscillation control voltage of the transmission frequency conversion unit is provided, and the variable attenuator is provided by the output of the adder. A frequency conversion / amplification device characterized in that it controls the amount of attenuation.