JPH0362707A - Frequency converter for receiving satellite broadcast - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a frequency conversion device for satellite broadcasting that converts the frequency of a desired signal with low loss and suppresses undesired signals in reception of satellite broadcasting.

Conventional technology In recent years, frequency converters for receiving satellite broadcasting are required to have low loss and high interference rejection ability in order to be able to receive various programs at low cost due to the increase in the number of broadcast waves and the miniaturization of receiving antennas. There is.

A conventional frequency converter for receiving satellite broadcasting will be described below.

FIG. 3 is a block diagram of a satellite broadcast frequency conversion device.

In FIG. 3, 1 is a first intermediate frequency input terminal, and 2 is an input circuit composed of a filter circuit and an amplifier circuit. 3 is a double tuning circuit, 4 is a frequency mixing circuit, 5 is a voltage controlled oscillator, 6 is a second intermediate frequency output circuit constituted by a filter circuit 1 and an amplifier circuit, and 7 is a second intermediate frequency output terminal.

FIG. 4 shows a double tuning circuit of a conventional satellite broadcasting frequency converter.

In FIG. 4, 8 is an input circuit, 9 and 14 are coupling lines, 10.12 is a tuning line inductance, and 11.
13 is a tuning variable capacitance element, and 15 is a frequency mixing circuit.

The operation of the satellite broadcast reception frequency conversion circuit configured as above will be described below.

First, the input first intermediate frequency signal is amplified through the input circuit 2, with signals outside the band being suppressed. Next, in the double tuning circuit 3, signals outside the required channel band are further suppressed and output to the frequency mixer 4. A frequency mixer 4 mixes the signal with a local oscillation signal from a local signal generator 5 to convert it into a second intermediate frequency.

Next, the second intermediate frequency signal outputted from the frequency mixer 4 passes through the intermediate frequency output circuit 6, further suppresses unnecessary bands, is amplified, and is outputted from the terminal 7.

Next, the operation of the input signal selection filter 3 shown in FIG. 3 will be explained with reference to FIG. 4. By controlling the voltage of the variable capacitance elements 11.13 in synchronization with the local oscillation frequency, double tuning characteristics can be obtained between the inductances 10.12. Input of the signal is carried out using an inductance 10 via a coupling line 9 by inductive coupling, and output is carried out using an inductance 12.
This is done using the coupling line 14. In addition, the coupling line 9, the inductance 10, and the inductance 1
By setting the distance between the coupling line 14 and the coupling line 14, the degree of coupling can be adjusted and the passband can be varied.

With the above configuration, the loss of the desired signal is minimized, and the undesired signal that causes interference is sufficiently suppressed and then output to the frequency mixer.

Problem to be Solved by the Invention In the conventional configuration, the desired signal is passed through with low loss by selecting a double-tuned circuit and setting high characteristics, and for undesired signals, the suppression ratio is large and high interference rejection characteristics are achieved. such that it does not degrade the selection characteristics in order to be able to obtain
The connection structure between the front and rear circuits was important. However, in the conventional configuration described above, the impedance of the input and output circuits is much lower than the characteristic impedance of the double-tuned circuit, so tightly coupling the line inductances reduces the characteristic impedance of the line inductor of the double-tuned circuit. As a result, the selection characteristics of the double-tuned circuit deteriorate, so in order to obtain the desired amount of sweat control, the line inductance must be loosely coupled. However, if the coupling is loosely coupled, the coupling loss increases, resulting in a decrease in gain and a deterioration in the noise figure.

The present invention solves the above-mentioned conventional problems, and aims to provide a frequency conversion device for receiving satellite broadcasting that has low loss and can secure the necessary amount of suppression of undesired signals.

Means for Solving the Problems To achieve this object, the frequency converter for satellite broadcast reception of the present invention includes a double-tuned circuit consisting of a pair of line inductances and a variable capacitance element, and a pair of line inductances. It has a configuration in which a capacitor and a coil are connected in series to the input and output terminals connected between the capacitor and the variable capacitance element.

Effect With this configuration, the input/output load is not directly connected to the line inductance of the double-tuned circuit, so the characteristic impedance of the line inductance is not reduced.
Therefore, frequency conversion can be realized without deteriorating the selection characteristics of the double-tuned circuit.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a double tuning circuit of a frequency converter for receiving satellite broadcasting according to an embodiment of the present invention. 1st
In the figure, 16 is an input circuit, 17.24 is a coupling capacitor, 18.23 is a coupling coil, 19.21 is a tuning line inductance, 20.22 is a variable capacitance element,
25 is a frequency mixing circuit. Here, 17 and 18 and 24 and 23 are selected so as to match the impedance with the front and rear circuits in the first intermediate frequency band width.

FIG. 2 shows a specific circuit example of a frequency converter for receiving satellite broadcasting using the configuration shown in FIG.

In Fig. 2, 28 is an amplification transistor, 29 is a power supply terminal, 30.32 is a voltage controlled variable capacitance diode, 31.33 is a DC stopping capacitor, 34.35 is a tuning voltage application resistor, and 36 is a tuning voltage application resistor. Voltage application terminal, 37 voltage controlled oscillator, 38 frequency mixing transistor, 39
is the next stage amplifier.

The operation of the frequency converter for receiving satellite broadcasting configured as described above will be described below.

First, the input first intermediate frequency signal is amplified by the transistor 28 and then input to the double-tuned circuit via the capacitor 7 coil 8. Here diode 30
．． 32 changes its capacitance in synchronization with the local oscillation frequency of the oscillator 37 by a tuning voltage applied from the terminal 36, thereby passing only a desired channel band. The next signal passed through coil 23. The frequency is mixed with the local oscillation signal from the oscillator 37 by the transistor 38 via the capacitor 24 to generate a second intermediate frequency. This output is output via an amplifier 39.

As described in 2 below, according to this embodiment, by coupling the capacitor and the coil in series to the input and output terminals of the double-tuned circuit, there is no direct coupling to the line inductance of the double-tuned circuit, so the line inductance can be reduced. The loss of the desired signal can be reduced by performing impedance matching and direct coupling without lowering the characteristic impedance of the double-tuned circuit and therefore without degrading the selection characteristics of the double-tuned circuit.

Effects of the Invention As described above, the present invention includes a double-tuned circuit consisting of a pair of line inductance and a variable capacitance element, and a capacitor connected in series to the input and output terminals connected between each line and the variable capacitance element. By providing a configuration for connecting the coils, it is possible to realize an excellent frequency conversion device for satellite broadcast reception that can transmit data with low loss without deteriorating the selection characteristics of the double-tuned circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a double-tuned circuit of a frequency converter for satellite broadcast reception according to an embodiment of the present invention, and FIG. 2 is a specific circuit diagram of a frequency converter for satellite broadcast reception that constitutes a double-tuned circuit of the embodiment. FIG. 3 is a block diagram of a frequency converter for receiving satellite broadcasts, and FIG. 4 is a circuit diagram of a double tuning circuit of a conventional frequency converter for receiving satellite broadcasts. 18 23... Coil, 17. 24...-
・Capacitor, 19.21...Line inductance, 2022...Variable capacitance element.

Claims (1)

[Claims] It is characterized by a double-tuned circuit consisting of a pair of line inductances and a variable capacitance element, and a capacitor and a coil connected in series to the input and output terminals connected between each line inductance and variable capacitance element. Frequency converter for satellite broadcast reception.