JPH01106630A - Tuner circuit for satellite broadcast television receiver - Google Patents

Abstract

PURPOSE:To optimize the image suppression by patterning directly a resonance inductor for a pre-selector and a local oscillation circuit onto a printed circuit board in terms of microstrip line so as to facilitate the adjustment and to miniaturize the title circuit. CONSTITUTION:A satellite broadcast signal from a parabolic antenna 1 is converted into an IF signal by a converter 2 and inputted to a tuner 3. The frequency of the IF signal is selected in response to a voltage from a tuning voltage input terminal 30 by a pre-selector 6, mixed with a local oscillation signal whose wavelength is lambda/2 by a mixer 7 to be an IF signal and subjected to gain control by an AGC and the result is fed to a demodulation circuit of a conventional TV receiver. Microstrip lines 16a-16d, 16h of the pre-selector 6 and the mixer 7 form resonance inductors and are printed as a pattern directly on the printed circuit board so as to form lambda/4 resonance. The primary side lines 16a, 16b and the secondary side line 16c are coupled by the pattern to the resonance line 16h and strip lines 16e-16g of the coil of the mixer 7 are printed directly onto the printed circuit board.

Description

[Detailed Description of the Invention] "Field of Industrial Application" The present invention relates to a tuner circuit for a satellite broadcast television receiver, and in particular to a tuner circuit in which the settings and configuration of an interstage double-tuned circuit and a local oscillation circuit are simplified. It is.

"Prior Art" Generally, a satellite broadcast television receiver has a tuner circuit as an adapter connected to the front stage of a normal terrestrial broadcast television receiver.

To explain this tuner circuit, when a parabolic antenna receives satellite broadcasting signals in the 11 GHz band and 4 GHz band, the converter receives the first signal in the 950-1450 MHz band.
is converted into an intermediate frequency (IF) signal, amplified by this first IF multiplier signal amplification circuit, a preselector circuit consisting of a crotch double tuning circuit selects a signal of a predetermined frequency, and sends it to a mixer circuit. The circuit mixes the local oscillation signal of the local oscillation circuit and generates a second intermediate frequency (I
F) A signal is obtained, amplified by an amplifier circuit, passed through a low-pass filter (LPF) circuit, further amplified by an amplifier circuit, and sent to the demodulation circuit of a normal television receiver.

However, in the double tuning circuit or local oscillation circuit of the UHF tuner circuit of a normal television receiver, the tuning coil has one frequency that is high, so as shown in Figure 3, a microstrip line punched out of a copper plate into a U-shape or rod shape is used. (16)...
into the through hole (1a) of the printed circuit board (17)...
It is made by sticking it in place or fixing it with solder, etc. At this time,
When the interstage double-tuned circuit and local oscillation circuit were in the up position, the other was also set at -.

Uni: ``Problems that the invention aims to solve'' Microstrip lines are long when the frequency is low and become short as the frequency increases, but conventional ones made by punching out a copper plate have a short length when the frequency is high. A short one allows for miniaturization, but requires complicated adjustment; conversely, one with a low frequency and a long length makes adjustment easy, but increases the size. Furthermore, when fixing to a printed circuit board, there is a problem in that if there is a slight difference in the amount of solder or if the solder rises slightly from the printed circuit board, the single frequency characteristic changes.

``Means for Solving Problems'' The present invention was made to solve the above-mentioned problems, and after converting a satellite broadcasting signal received by a parabolic antenna into a first IF multiplied signal using a converter, In this circuit, a tuning voltage is applied to a preselector circuit to extract a signal of a predetermined frequency, and this signal is mixed with a local oscillation signal of a local oscillation circuit to convert the signal into a second IF multiplied signal.
The resonant inductor of the double-tuned circuit constituting the preselector circuit is set to -, the resonant inductor of the local oscillation circuit is set to -, and a microstrip line is patterned on a printed circuit board using these resonant inductors. It is something that is formed.

"Operation" When receiving satellite broadcasting signals in the 11GHz band and 4GHz band with a parabolic antenna, the converter receives 950~1450M
Hz is converted into a first IF signal, a preselector circuit selects a signal with a frequency corresponding to the tuning voltage, this signal is mixed with a local oscillation signal in a mixer circuit, and is converted to 134.
A second IF multiplied signal of 26MHz is obtained, and this signal is the second IF signal.
It is amplified by an amplifier circuit for At this time, since the preselector and the resonant inductor of the local oscillation circuit are formed by directly patterning a microstrip line on the printed circuit board, a second IF signal of an extremely accurate frequency is converted.

"Example" Hereinafter, one embodiment of the present invention will be described based on one aspect.

In Figure 2, (1) is a parabolic antenna.

This parabolic antenna (1) is coupled via a converter (2) to an input terminal (4) of a tuner circuit (3). This input terminal (4) is connected to the first IF amplifier circuit (5),
It is coupled to a mixer circuit (7) via a preselector circuit (6), and a local oscillation circuit (8) and an oscillation signal amplification circuit (9) are coupled to this mixer circuit (7).

On the output side of this mixer circuit (7), there is a first-stage amplifier circuit (11) for the second IF, a low-pass filter (LPF) circuit (
12), the output terminal (14) is coupled via a two-stage amplifier circuit (13) for the second IF;
Automatic gain control (AGC) is used in the first stage amplifier circuit (11) for
A circuit (10) is coupled. A second IF signal (134, 26 MHz) is connected to the output side of the oscillation signal amplification circuit (9).
) is coupled to a sufficient frequency circuit (15) for detecting deviation.

The double tuning circuit that constitutes the preselector circuit (6) is:
As shown in Figure 1, a microstrip line (16
a) (16b) (16c) (16d) (16h)
, variable capacitance diodes (19) (20), resistors (21) (22), capacitors (23) (24)
It consists of (25) (26) (27) (28) (29). Of these, the microstrip line (1
6a) (16b) (16c) (16d), (16h
) to form a resonant inductor, ■ are directly patterned and immediately installed on the printed circuit board (17) so as to have a resonance length, and the primary side (16a) (16b
) and the secondary side (16c) through their respective resonance lines (
16h) from an appropriate position in a pattern. Also, the coils of the mixer circuit (7) are immediately installed directly on the printed circuit board (17) using microstrip lines (16e, 16f, and 16g).

In addition, (30) is a tuning voltage input terminal, (31) is a signal input terminal, (32) is a local oscillation signal input terminal, (33)
is a second IF signal output terminal of 134.26 MHz.

The local oscillation circuit (8) oscillates a vertical resonance signal, and as shown in FIG. (35), and one capacitor (34) is coupled to a tuning voltage input terminal (37) via a resistor (36), as well as a variable capacitance diode (38). Other transistors (3
9), resistance (40) (41) (42) (43),
Capacitor (44) (45) (46) (47) (
48) (49) (50) (51)

The oscillation signal amplification circuit (9) also includes a pickup inductor (52), a transistor (5a) (54),
It consists of resistors (55) (56) (57) (58) and capacitors (59) (60) (61) (62). (63) is an output terminal to the mixer circuit (7).

Next, the present invention will be explained in detail.

When the parabolic antenna (1) receives satellite broadcast signals in the 11 GHz band and 46 tome band, the converter (2) receives the 950
It is converted into a first intermediate frequency (IF) signal in the ~1450 MHz band and input to the input terminal (4) of the tuner circuit (3). The first IF multiplied signal input to this input terminal (4)
It is amplified by an IF amplifier circuit (5), and a preselector circuit (6) selects a signal of a predetermined frequency corresponding to the voltage from the tuning voltage input terminal (30) and sends it to a mixer circuit (7). This mixer circuit (7) mixes the Δ local oscillation signal sent via the oscillation circuit (8) and the oscillation signal amplification circuit (9) to generate a second intermediate frequency (IF) signal of 134.26MHz. outputs. This second IF multiplied signal is amplified by the first stage amplifier circuit (11) for the first IF,
At this time, the gain is controlled to a predetermined value by the AGC voltage from the AGC circuit (10). After that, a low pass filter (LPF)
) circuit (12) to a two-stage amplifier circuit (13) for the second IF.
), and this 134.26 M7 second F signal is sent to the demodulation circuit of an ordinary television receiver via the output terminal (14).

"Effects of the Invention" As described above, in the present invention, when forming a resonant inductor with a microstrip line, τ resonance is used for the double-tuned circuit between the legs, and input resonance is used for the local oscillation circuit.
It is possible to configure a circuit that has the characteristics of easy adjustment and miniaturization. In addition, the desired selectivity (bandwidth) can be obtained by forming a pattern directly on the printed circuit board and coupling the primary and secondary sides from an appropriate position on each resonance line. Moreover, the best value can be selected for image disturbance.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of a preselector circuit and a local oscillation circuit in a tuner circuit according to the present invention, and FIG. 2 is a block diagram of a tuner circuit of a satellite broadcast television receiver.
FIG. 3 is a perspective view of a conventional microstrip line. (1)...Parabola antenna, (2)...Converter 1<3)...Tuner circuit, (4)...Input terminal, (5)...Amplification circuit, (6)... Preselector circuit, (7)... mixer circuit 5, (8)... oscillation circuit, (9)... oscillation signal amplification circuit, (io)...
AGC circuit, (11)...first stage amplifier circuit for second IF,
(12)...LPF circuit, (13)...2nd IF two-stage amplifier circuit, (14)...output terminal, (16) (
16a) ~(16i)-Microstrip line,
(17)...Printed circuit board. Third cause

Claims (1)

[Claims] (1) After converting the satellite broadcasting signal received by the parabolic antenna into a first IF signal with a converter, applying a tuning voltage to the preselector circuit to extract a signal of a predetermined frequency,
In a circuit configured to mix this signal with a local oscillation signal from a local oscillation circuit and convert it into a second IF signal, a resonant inductor of a double-tuned circuit constituting the preselector circuit is set to λ/4, A tuner circuit for a satellite broadcast television receiver, characterized in that a resonant inductor of the local oscillation circuit is set to λ/2, and microstrip lines are formed as the resonant inductors by patterning on a printed circuit board.