JPH0430622A - television tuner - 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 INDUSTRIAL APPLICATION The present invention relates to a television control tuner used in television receivers, home VTRs, and the like.

Conventional technology (Conventional technology 1) will be described below with reference to the drawings. Second
Figures (a) to (c) are a circuit diagram of an input circuit section of a conventional television tuner and an equivalent circuit diagram of its essential parts.

In FIGS. 2(a), (b), and (C), 1 is an input terminal from an antenna, 2 is an IF filter, and 3. 9.
11゜14, 21 is a DC blocking capacitor, 4 is a low band matching coil, 5 is a high band matching coil, 6. '1.12.22.23 is a bias resistor for switching diode, 8 is a tuning coil for low band, 10 is a tuning coil for high band, 13.24 is a switching diode, 15 is a varicap diode for tuning, 16 is a varicap diode 17 is an RF signal amplification circuit, 18 is a voltage application terminal for low band reception, 19 is a voltage application terminal for high band reception, 2
0 is a voltage application terminal for a varicap diode.The TV station chainer configured in the above keyaki will be explained below.

A television signal (hereinafter abbreviated as RF signal) inputted to the input terminal 1 from the antenna has its intermediate frequency band attenuated by the IF filter 2 and is sent to the high band matching coil 5 and then to the low band matching coil 4. is input. The RF multiplied signals outputted from these are input to the next stage tuning coil 8.10 and the tuning varicap diode 15, and after selecting the RF multiplied signal of the desired channel, the signal is amplified by the RF signal amplification circuit ll117 and sent to the next stage. communicated. Thereafter, the signal is mixed with local oscillation, converted into an intermediate frequency, and output from a television syllan tuner.

Next, a method of switching between the low band and high band will be explained.

Figure 2 (The equivalent circuit for low-band reception in part A of the grape is shown in Figure 2.
The equivalent circuit at the time of high band reception of the A part of the above-mentioned Fig. 2 (B) is shown in Fig. 2 (C). In Fig. 2 (B), 7A is It is a combined resistance of bias resistors 6 and 7 for switching diodes, and is shown in Figure 2 (
In C), IOA is the combined inductance of the low-band tuning coil 8 and high-band tuning coil 10 in FIG. 2(6), and 22A is the combined inductance of the switching diode bias resistors 6, 7, and 22 in FIG. 2(a). It is a composite resistance. In part A of FIG. 2(a), during low band reception, a voltage is applied to the low band reception voltage application terminal 18, and the high band voltage application terminal 19 is set to O potential or open. Then, the cathode potential of the switching diode 13 becomes high via the switching diode bias resistor 7, and the switching diode 13 is turned off.
A matching coil during low band reception is formed by connecting a low band matching coil 4 and a high band matching coil 5 in series to obtain low band matching. Similarly, by turning off the switching diode 24, the high band tuning coil 10 is opened, and the low band tuning coil 8 performs low band tuning. During high-band reception, by setting the low-band reception voltage application terminal 18 to 0 potential or open and applying a voltage to the high-band voltage application terminal 19, current flows to the switching diode 13 via the switching diode bias resistor 22, and the switching diode 13 By turning on, the low band matching coil 4 is short-circuited, and high band matching power is obtained. Similarly, by turning on the switching diode 24, the high band tuning coil io is grounded and connected in parallel with the low band tuning coil 8. Tuning coil for high band
Since O is sufficiently smaller than the low band tuning coil 8, the inductance during high band reception is approximately determined by the high band tuning coil 7L and IQ. This allows high band reception.

(Prior Art 2) Next, a description will be given of a conventional technology 2 in which a low band matching coil and a high band matching coil are configured in parallel with reference to the drawings.

FIGS. 3(a) to 3(e) are a circuit diagram and an equivalent circuit diagram of an input circuit section of a conventional television tuner. Figure 3 (6
), (b), and (C), 1 is the input terminal from the antenna, 2 is the IF filter, 3.9.11.14.
21 is a DC blocking capacitor, 4 is a low band matching coil, 5 is a high band matching coil, 6.
7.12.22.23 is a bias resistor for switching diode, 8 is a tuning coil for low band, lO is a tuning coil for high band, 13.24 is a switching diode, 15 is a varicap diode for tuning, 16 is for varicap diode Bias resistor, 17 is an RF signal amplification circuit, 18 is a voltage application terminal for low band reception, 19
2 is a voltage application terminal for high band reception, and 20 is a voltage application terminal for a varicap diode.The television tuner constructed of the above-mentioned camphor will be described below.

The RF multiplied signal input to the input terminal l from the antenna, I
The intermediate frequency band is attenuated by the F filter 2 and input to the low band matching coil 4 and the high band coil 5. RF multiplied signal outputted from these Next stage tuning coil 8.10 and tuning varicap diode 1
After selecting the RF multiplied signal of the desired channel, the signal is amplified by the RF signal amplification circuit 17 and transmitted to the next stage. Thereafter, the signal is converted into an intermediate frequency by mixing with the local oscillation, and output from the television tuner. Next, a method of switching between the low band and high band will be explained.

The equivalent circuit of section A in FIG. 3(a) during low band reception is shown in FIG. 3(a), and the equivalent circuit of section A of FIG. 3), 7A is the combined resistance of the switching diode bias resistors 6, 7, and 22 in FIG. 3 (3);
In Figure (C), 5A is the composite inductance of the low band matching coil 4 and high band matching coil 5 in Figure 3 (a), and IOA is the composite inductance of the low band tuning coil 8 and high band matching coil 8 in Figure 3 (a). 22A is the composite inductance of the tuning coil 10, and 22A is the third
This is a combined resistance of the switching diode bias resistors 6, 7, and 22 in FIG.

FIG. 3 (In part A of the stem, when receiving a low band, a voltage is applied to the low band reception voltage application terminal 18, and when the high band voltage application terminal 19 is at 0 potential or opened, the switching diode 13 is applied via the switching diode bias resistor 7. The cathode potential becomes high and the switching diode 13 is turned off. Therefore, the matching coil during low band reception is formed by the low band matching coil 4, and low band matching is obtained. Similarly, the switching diode 24 is turned off. As a result, the high band tuning coil 10 is opened, and low band tuning is performed by the low band tuning coil 8. At the time of high band reception, the low band reception voltage application terminal 18 is set to 0 potential or open, and a voltage is applied to the high band voltage application terminal 19. Then, current flows to the switching diode 13 via the switching diode bias resistor 22, the switching diode 13 is turned on, and the matching coil for high band reception is divided into the matching coil 4 for the low band and the matching coil 4 for the high band. The coils 5 are connected in parallel to obtain high band matching.Similarly, when the switching diode 24 is turned on, the high band tuning coil 10 is grounded and connected in parallel with the low band tuning coil 8.High band tuning Since the coil 10 is sufficiently smaller than the low band tuning coil 8, the inductance during high band reception is almost determined by the high band tuning coil 10. This makes it possible to receive the high band.

Problems to be Solved by the Invention However, in the configuration as shown in (Prior Art 1), during high band reception, the switching diode bias resistors 6 and 7 are
．． 22 is connected in parallel to the high band tuning coil 10. Bias resistor 6 for the switching diode
, 7.22 combined resistance 22A is 400Ω when the power supply voltage is 5μ and the diode current is 2μA, which is a tuning circuit consisting of a parallel connection of a varicap diode 15, which normally has an impedance of about 10Ω, and a high-band tuning coil 10. This has the problem of acting as damping on the circuit and as stray capacitance due to component mounting, deteriorating the NF, selectivity, and broadband reception of the circuit.

In addition, in order to solve this problem, there is a method (conventional technique 2) in which the bias resistors 6, 7, and 22 for switching diodes are connected to points of low impedance.
There were the following problems.

Usually the matching coil is about 550nH when receiving low band and 250nH when receiving high band.
Since the low-band matching coil 4 is configured with approximately 330 nH and the high-band matching coil 5 is configured with approximately 250 nH in (Conventional Technology 1), as shown in FIG. Since the circuit configuration of technology 2) is a parallel connection configuration, the low band matching coil 4 requires approximately 580 nH, and the high band matching coil 5 requires approximately 500 nH. However, this resulted in a very large shape, which left a problem in that it was a major hindrance to the miniaturization of television tuners. Therefore, the present invention (prior art 1)
), the purpose is to prevent deterioration of the NF, selectivity, and broadband reception of the circuit, and to prevent the circuit from increasing in size as in (prior art 2).

Means for Solving the Problems and In order to achieve this object, the present invention electrically connects one end of a low band matching coil to a tuner input terminal into which a television signal is input, and One end of a high band matching coil is electrically connected to the other end, and a switching diode is electrically connected in parallel with the low band matching coil.

According to this configuration, the switching diode and the bias resistor for the switching diode can be placed before the high-band matching coil coil with low impedance, which solves the problem during high-band reception, which was the problem with (prior art 1). In addition to preventing deterioration of NF, selectivity, and broadband reception, connecting the low-band matching coil and high-band matching coil in series also eliminates the problem of increasing the size of the coil, which was a problem with conventional technology 2. It can be solved.

Example Hereinafter, an explanation will be given based on one embodiment of the present invention.

FIGS. 1(a) to 1(C) are a circuit diagram and an equivalent circuit diagram according to an embodiment of the present invention.

In Fig. 1 ((material), (6), and (C)), 1 is the input terminal from the antenna, 2 is the IF filter, and 3.9.11.
1421 is a DC blocking capacitor, 4 is a low band matching coil, 5 is a high band matching coil,
6. 7.12.22.23 is a bias resistor for switching diode, 8 is a tuning coil for low band, 10 is a tuning coil for high band, 13.24 is a switching diode, 15 is a varicap diode for tuning, 16
is the bias resistor for the varicap diode, 17 is the RF
signal amplification circuit; 18 is a voltage application terminal for low band reception;
19 is a voltage application terminal for high band reception, and 20 is a voltage application terminal for varicap diode.The television tuner configured as above will be described below.

The RF signal input to input terminal 1 from the antenna is I
The intermediate frequency band is attenuated by the F filter 2 and inputted to the low band matching coil 4 and then to the high band matching coil 5. R output from these
The F signal is input to the next stage tuning coils 8 and 10 and the tuning varicap diode 15, and after selecting the RF signal of the desired channel, the signal is amplified by the RF signal amplification circuit 17 and transmitted to the next stage. Thereafter, it is mixed with local oscillation, converted into an intermediate frequency, and output from a television tuner.

Next, a method of switching between the low band and high band will be explained.

The equivalent circuit of section A in FIG. 1(a) during low band reception is shown in FIG. 1(b), and the equivalent circuit of section A in FIG. 1(a) during high band reception is shown in FIG. 1(C). ), 7A in FIG. 1(b) is the combined resistance of the switching diode bias resistors 6 and 7 in FIG. 1(a), and 8A
is the combined inductance of the low-band tuning coil 8 and the high-band tuning coil 10 in FIG. 1(a), and in FIG. 1(C), 22A is the switching diode bias resistor 6 and 7 in FIG. 1(a). and 22 combined resistance.

In section A of FIG. 1(a), during low band reception, a voltage is applied to the low band reception voltage application terminal 18, and the high band voltage application terminal 19 is set to O potential or open. Then, the cathode potential of the switching diode 13 increases via the switching diode bias resistor 7,
The switching diode 13 is turned off, and the L/4t low band matching coil 4 and the high band matching coil 5 are connected in series to obtain low band matching.Similarly, the switching diode 24 is turned off. The low band is tuned by the inductance formed by the series connection of the high band tuning coil 10 and the low band tuning coil 8.When receiving the high band, the low band reception voltage application terminal 18 is set to 0 potential or open, and the high band voltage is turned off. A voltage is applied to the application terminal 19. Then, a current flows to the switching diode 13 via the switching diode bias resistor 22, and the switching diode 13 is turned on.As a result, the low band matching coil 4 is short-circuited, and high band matching is disabled. Similarly, when the switching diode 24 is turned on, the low-band tuning coil 8 is short-circuited, and the high-band tuning is performed by the inductance of the high-band tuning coil IO.

As described above, according to this embodiment, one end of the low-band matching coil 4 is electrically connected to the input terminal 1 of the tuner into which a television signal is input, and the other end of the low-band matching coil 4 is connected to the input terminal 1 of the tuner to which a television signal is input. , one end of the high band matching coil 5 is electrically connected, and a switching diode 1 is connected in parallel with the low band matching coil 4.
This is an electrical version of 3.

For this reason, during high-band reception, as is clear from the equivalent circuit in FIG. 1 (C) during high-band reception, the combined resistance 2
2A is 400Ω when the power supply voltage is 5V and the diode current is 2mA, but since it is connected to the antenna input section whose impedance is as low as 75Ω, there is almost no effect of stray capacitance due to damping or component mounting in terms of the circuit. Therefore, it is possible to design a circuit that prevents deterioration of NF, selectivity, and broadband reception. However, since the matching coil is formed by connecting the low band matching coil 4 and the high band matching coil 5 in series, in (prior art 2), the low band matching coil 4 has a power of about 580 nH, and the high band matching coil 4 has a power of about 580 nH. While the matching coil 5 is configured with approximately 500 nH, according to this embodiment, the low band matching coil 4 can be configured with approximately 330 nH, and the high band matching coil 5 can be configured with approximately 250 nH. The inductance of the low-band matching coil 4 and the high-band matching coil 5 can be reduced, and by using smaller air-core coils, the tuner can be made smaller at the same time.

Effects of the Invention As described above, the present invention electrically connects one end of a low band matching coil to a tuner input terminal into which a television signal is input, and connects a high band matching coil to the other end of the low band matching coil. NF by electrically connecting one end of the matching coil and electrically connecting a switching diode in parallel with the low band matching coil.

It is possible to realize a television tuner that has excellent selectivity and broadband reception, and is space-saving and suitable for downsizing.

[Brief explanation of the drawing]

1(a) is a circuit diagram of the input circuit section of a television tuner according to an embodiment of the present invention, and FIG. 1(b) is a circuit diagram of the input circuit section of a television tuner according to an embodiment of the present invention.
A) Equivalent circuit diagram of part A during low band reception, Figure 1 (
C) is an equivalent circuit diagram of part A of FIG. 1(a) during high band reception; FIG. 2(a) is a circuit diagram of the input circuit section of a television tuner according to (prior art 1); 0)) is an equivalent circuit diagram of part A in Fig. 2(a) during low band reception, Fig. 2(C) is an equivalent circuit diagram of part A in Fig. 2(a) during high band reception, and Fig. 3 Figure (a) is a circuit diagram of the input circuit section of a television tuner (prior art 2) and Figure 3 (b).
is an equivalent circuit diagram of part A in FIG. 3(a) during low band reception, and FIG. 3(C) is an equivalent circuit diagram of part A in FIG. 3(a) during high band reception. 1... Input terminal from antenna, 2...
・IF filter, 3. 9.11.14...
DC blocking capacitor, 4...Matching coil for low hand, 5...Matching coil for high band, 6.7.12...Bias resistor for switching diode, 8 ...0- Han F'
Tuning coil for use, 10... Tuning coil for high band, 13... Switching diode, 15.
...Tuning varicap diode, 16...
...Bias resistor for varicap diode, 17.
Old...RF signal amplification circuit, 18... Voltage application terminal for low band reception, 19... Voltage application terminal for high band reception, 20... Voltage application for varicap diode Terminal, 7A... Combined resistance of bias resistors 6 and 7 for switching diode, 8A...
...Combined inductance of high band tuning coil 10 and drawpant tuning coil 8, 5A...Combined inductance of low band matching coil 4 and high band matching coil 5, 22A... Combined resistance of bias resistors 6, 7, and 22 for switching diodes.

Claims (1)

[Claims] Electrically connect one end of the low band matching coil to the tuner input terminal where the television signal is input,
A television tuner characterized in that one end of a high band matching coil is electrically connected to the other end of the low band matching coil, and a switching diode is electrically connected in parallel with the low band matching coil.