JPS61283209A - Adjusting circuit for intermediate frequency band width - Google Patents

Abstract

PURPOSE:To obtain a required intermediate frequency band width by adding an intermediate frequency output of a tuner to a surface acoustic wave filter, connecting a tuning circuit in parallel with the output terminal of the surface acoustic wave filter and making the tuning circuit variable. CONSTITUTION:An intermediate frequency is impressed to an input terminal 6 of a surface acoustic wave filter 2 from an intermediate frequency output terminal via a capacitor 5. The intermediate frequency signal is fed to an intermediate frequency amplifier circuit 10 from output terminals 7, 8 of the filter 2 via a capacitor 9. The variation in the frequency characteristic due to the tuner 1 and the surface acoustic wave filter 2 is corrected properly by the tuning circuit comprising a variable coil 11, a tuning capacitor 12 and a damping resistor 13, fed to the intermediate frequency amplifier circuit 10 via the capacitor 9 to obtain a proper television signal.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a bandwidth adjustment circuit for an intermediate frequency amplifier circuit used in color television receivers and the like.

2. Description of the Related Art An example of a conventional intermediate frequency bandwidth adjustment circuit is shown in FIG. In FIG. 2, the bandwidth adjustment circuit 21 is connected to the tuner 2.
2 intermediate frequency output terminal 23 and surface acoustic wave filter 2
4 to obtain the necessary intermediate frequency bandwidth. Here, 25 is an intermediate frequency amplification circuit.

Problems to be Solved by the Invention However, in such conventional circuits, there were problems such as a complicated circuit configuration and a large insertion loss.The present invention was made in view of these points. It is an object of the present invention to provide an intermediate frequency bandwidth adjustment circuit with a simple configuration and low insertion loss.

Means for Solving the Problems In order to solve the above problems, the present invention adds the intermediate frequency output of a tuner to a surface acoustic wave filter, connects a tuning circuit in parallel with the output terminal of this surface acoustic wave filter, and The required intermediate frequency bandwidth can be obtained by making the tuning circuit variable.

Function The present invention corrects the frequency characteristics of the surface acoustic wave filter using the resonance curve of the tuning circuit with the above configuration, and adjusts it to the necessary intermediate frequency bandwidth, and also has a simple configuration. It is something that can be done.

Embodiment FIG. 2 shows an embodiment of the intermediate frequency bandwidth adjustment circuit of the present invention.

In FIG. 2, reference numeral 1 denotes a tuner of a television receiver, and an intermediate frequency signal is applied from an intermediate frequency output terminal of the tuner 1 to an input terminal 6 of a surface acoustic wave filter 2 via a capacitor 5. This intermediate frequency signal is transmitted from the output terminals 7 and 8 of the surface acoustic wave filter 2 via a capacitor 9 to an intermediate frequency amplification 11, a % capacitor 12. It is constituted by a damping resistor 13 and is connected in parallel to the output terminal 8 of the surface acoustic wave filter 2.

Next, to explain the operation, the intermediate frequency bandwidth of the tuner 1 and the bandwidth of the surface acoustic wave filter 2 usually vary, and in order to obtain appropriate frequency characteristics, the intermediate frequency bandwidth must be adjusted appropriately. There is a need. The intermediate frequency signal output from the output terminal 4 of the cheese 1 is supplied to the input terminal 6 of the surface acoustic wave filter 2 via the capacitor 5, and the frequency characteristics are determined by the filter 2. An intermediate frequency signal is output via the capacitor 9. These variations in frequency characteristics caused by the tuner 1 and the surface acoustic wave filter 2 are controlled by the variable coil 11 and the tuning capacitor 12. A tuning circuit comprising a damping resistor 13 corrects the signal appropriately, and the signal is supplied to the intermediate frequency amplification circuit 1o via the capacitor 10, thereby obtaining an appropriate television signal.

Effects of the Invention As described above, according to the present invention, it is possible to adjust the intermediate frequency bandwidth with an extremely simple circuit configuration, which is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an intermediate frequency bandwidth adjustment circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional intermediate frequency bandwidth adjustment circuit. 1... Tuner, 2... Surface acoustic wave filter, 3... Tuning circuit, 5... Capacitor, 9... Capacitor, 10.・・・・・・
Intermediate frequency amplification circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1/ Figure 2

Claims (1)

[Claims] The intermediate frequency signal output from the tuner is applied to a surface acoustic wave filter, and a tuning circuit including a variable coil, a capacitor, and a resistor is connected in parallel with the output terminal of the surface acoustic wave filter, and the intermediate frequency signal output from the surface acoustic wave filter is connected in parallel with the output terminal of the surface acoustic wave filter. and an intermediate frequency bandwidth adjustment circuit, wherein the band characteristics of the intermediate frequency signal are made variable by the tuning circuit.