JPH071854Y2 - Frequency converter - Google Patents

Description

[Detailed Description of the Invention] "Industrial application field" This invention is a low noise block converter (hereinafter, abbreviated as LNB) that frequency-converts a received microwave in a receiving system for receiving satellite broadcasting, for example. The present invention relates to a frequency conversion device suitable for use as the above, and particularly to a frequency conversion device having a simplified power supply circuit.

“Prior art” For example, when receiving satellite broadcasting, microwaves sent from artificial satellites are received by a parabolic antenna, the received weak signals are amplified by the LNB, and converted to a frequency band that is easy for signal processing. After that, it is pulled into the house with a coaxial cable or the like and is input to the receiver.

This type of LNB has conventionally been configured as shown in FIG. In this figure, 1 is a high-frequency amplifier consisting of three-stage FETs (field-effect transistors) 2, 3 and 4 for amplifying an RF signal (for example, a weak signal of 12 GHz) supplied to its input terminal IN with low noise. (RFAmp) 5 is a bias circuit for applying a bias voltage between the gate and drain of each of the FETs 2, 3, and 4 described above. Reference numeral ₆ denotes a mixer (MIX) which mixes the output (microwave) of the high frequency amplifier 1 with the output of the local oscillator 7 and outputs an intermediate frequency signal of about 1 GHz, and from the strip lines SL ₁ to SL ₅ connected in parallel. And a mixer with a cathode connected to the stripline SL ₃ of the coupler 8.
A diode D, a strip line SL ₆ whose other end is grounded at one end is connected to the cathode of the mixer diode D, a strip line SL ₇ whose one end is connected to the anode of a mixer diode D, the strip line SL It is composed of a resistor R and a capacitor C interposed between the other end of ₇ and the ground. Reference numeral 9 is an intermediate frequency amplifier (IFAmp) that amplifies the output of the mixer 6 and outputs it from its output terminal OUT. Reference numeral 10 is a three-terminal regulator that supplies a positive voltage to the intermediate frequency amplifier 9, the positive voltage input terminal 5p of the bias circuit 5, and the negative power supply circuit 11 based on the power source + B supplied from the outside to the output terminal OUT. Reference numeral 11 denotes a negative power supply circuit including a low-frequency oscillator circuit 12 driven by a positive voltage supplied from the three-terminal regulator 10 and a rectifier circuit 13 that rectifies the output of the low-frequency oscillator circuit 12. Reference numeral 11 supplies the generated negative voltage to the negative voltage input terminal 5n of the bias circuit 5. The low frequency oscillation circuit 12 is composed of a multivibrator.

Low-noise FETs 2, 3, and 4 are used in the high-frequency amplifier 1 that constitutes the above-mentioned LNB in order to satisfy the requirement for low noise. The noise figure of this type of low-noise FET depends on the drain current Id as shown in FIG. 3. In the example shown in FIG. 3, the noise figure is the best near the drain current Id of 10 [mA]. Low noise characteristics can be obtained. Further, FIG. 4 is a diagram showing the relationship between the gate-source voltage VGS and the drain current Id of the low noise FETs 2, 3, and 4 of this type, and the drain current Id becomes 10 [mA]. To the gate about −
It is understood that a bias voltage of 1 [V] should be applied.

Here, by directly grounding the sources of FET2,3,4,
By lowering the grounding impedance, the current feedback can be minimized, and the low noise characteristic that the element originally has can be brought out. Therefore, in order to realize a low noise amplifier using the FETs 2, 3, and 4 of this type, two systems of power supplies, a positive voltage applied to the drain and a negative voltage applied to the gate, are required. If it is necessary to make the bias voltages applied to the FETs 2, 3, 4 different, a plurality of bias circuits 5 may be arranged in parallel.

[Problems to be solved by the device] By the way, in the high-frequency amplifier 1 using the low-noise FETs 2, 3, and 4, in order to maintain a steady operation state in which good high-frequency characteristics are obtained, two positive and negative power supplies are used. is necessary. However, as in the case of the LNB shown in FIG. 2, when only a positive voltage is supplied from the outside, it is necessary to provide the negative power supply circuit 11 that internally generates a negative voltage, which is a drawback that the power supply circuit becomes complicated. . Further, since the low-frequency oscillator circuit 12 such as a multivibrator is used to configure the negative power supply circuit 11, a low-frequency signal leaks to the output terminal OUT,
There is a possibility that inconvenience may occur such that the output signal is interfered with by the low frequency signal.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to eliminate the need for a negative power supply circuit, which simplifies the structure of the power supply circuit and reduces the conventional low-frequency oscillator circuit that constitutes the negative power supply circuit. It is an object of the present invention to provide a frequency conversion device that can eliminate all inconveniences that have occurred.

"Means for Solving the Problem" This invention amplifies a received signal by a low noise amplifier,
In the frequency conversion device for frequency-converting and outputting by mixing the output of the amplifier and the output of the oscillator by a mixer diode, a bias resistance is inserted between the detection output end of the mixer diode and the ground. A negative voltage is applied to the amplification element of the low noise amplifier as a bias voltage.

[Operation] According to the above configuration, the negative voltage generated in the bias resistor interposed between the detection output end of the mixer diode and the ground can be used as the bias voltage of the amplification element of the low noise amplifier. As described above, it is not necessary to separately provide a negative power supply circuit configured by a low frequency oscillation circuit, which simplifies the configuration of the power supply circuit and
All the inconveniences such as the modulation interference caused by the low frequency signal in the low frequency oscillation circuit are eliminated.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. In this figure, the difference from the conventional LNB shown in FIG. 2 is that the negative power supply circuit 11 is deleted, and instead, the connection point between the strip line SL ₇ and the resistor R and the negative voltage input terminal of the bias circuit 5. It is located at a point where it is connected to 5n via a connection line 20.

With this configuration, the negative DC voltage induced in the resistor R interposed between the cathode (detection output end) of the mixer diode D and the ground is the negative voltage input to the bias circuit 5 of the high frequency amplifier 1. The bias circuit 5 is driven by the voltage supplied to the end 5n, and a negative voltage is supplied to each gate of the FETs 2, 3, and 4. That is, the strip lines SL ₆ and SL _{7 having} a predetermined length
Has the function of blocking the passage of high-frequency components and passing only the DC component, and by applying the oscillation output of the local oscillator 7 to the mixer diode D,
The detection current (diode current is about 5 [mA]) flows. Here, a desired negative voltage is induced by appropriately setting the value of the resistor R (about 1 [kΩ], -5 [V]) so that the voltage required in the bias circuit 5 can be obtained. It By driving the bias circuit 5 by the negative voltage induced in the resistor R, the negative voltage is supplied to the FETs 2, 3, 4 of the high frequency amplifier circuit 1. Then, by controlling the gate-source voltage VGS, a desired drain current Id can be obtained, and a steady operation state in which good high frequency characteristics are obtained can be maintained.

As described above, according to the above-described embodiment, the negative power supply circuit 11 which has been necessary in the related art is no longer necessary.
All the inconveniences such as the spurious of the low frequency signal generated by the low frequency oscillating circuit 12 and the modulation interference with the output signal are eliminated.

[Advantage of the Invention] As described above, according to the present invention, the negative voltage generated in the bias resistor inserted between the detection output end of the mixer diode and the ground is used as the bias voltage of the amplification element of the low noise amplifier. Since the conventional power supply circuit is used, the negative power supply circuit, which has been necessary in the past, is unnecessary, the power supply circuit is simplified, the entire device can be downsized, and the low-frequency oscillation circuit forming the negative power supply circuit can be deleted. Therefore, it is possible to eliminate the spurious of the low frequency signal, and it is possible to eliminate the inconvenience that the low frequency signal causes the modulation disturbance to the output signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention,
Fig. 2 is a block diagram showing the configuration of a conventional LNB, Fig. 3 is a graph showing the relationship between the minimum noise figure and drain current of a low noise FET, and Fig. 4 is the gate-source voltage and drain current of the FET. It is a graph which shows the relationship with. 1 ... High frequency amplifier (low noise amplifier), 2,3,4 ... FET
(Amplifying element) 5 ... Bias circuit, 5n ... Negative voltage input terminal, 6 ... Mixer, 7 ... Local oscillator, 8 ... Combiner, D ... Mixer diode, R ... Resistor (bias resistor ), 20 …… Connection line.

Claims (1)

[Scope of utility model registration request] 1. A received signal is amplified by a low noise amplifier,
In a frequency conversion device for frequency-converting and outputting by mixing the output of the amplifier and the output of the oscillator by a mixer diode, a bias resistor is inserted between the detection output end of the mixer diode and the ground. A frequency conversion device, wherein a negative voltage is applied as a bias voltage to an amplification element of the low noise amplifier.