JPS63267024A - Antenna booster mixer - Google Patents

Abstract

PURPOSE:To prevent the generation of mutual modulation between an antenna signal and an output signal of an RF modulator by making the direction of the antenna signal in a signal line and the direction of a modulator signal at a coupling section identical. CONSTITUTION:An antenna signal is distributed to an output section 4 to a tuner in a VTR and a booster mixer 15 by a distributer 3. The booster mixer 15 has an RF amplifier 6 and a mixer 17. A direction A of the antenna signal path in the signal line 17a and a direction V of an output path from the RF modulator 9 at a coupling section 17b are directed the same in the mixer 17. Even when the antenna input signal with a large level is given in the VTR reproducing mode, the antenna signal is inputted to the coupling section 17b while being attenuated largely. Thus, the beat of a picture due to the mutual modulation between the antenna signal and the output signal of the RF modulator 9 in not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an antenna booster/mixer that is integrated with an RF modulator or the like, and particularly relates to an antenna booster/mixer that reduces antenna signal loss and improves isolation characteristics.

(Background of the Invention) FIG. 8 is a block diagram showing the configuration of a conventional RF modulator in which an antenna booster and mixer are integrated.

This integrated RF modulator does not require switching the signal output path between a TV receiver reception mode and a VTR playback mode.

That is, an antenna signal received by a television antenna 1 is amplified by an RF amplifier 2, and then distributed by a distributor 3 to an output 4 to a tuner in the VTR and a booster mixer 5. R for booster mixer 5
An F amplifier 6 and a mixer 7 are provided. Conventionally, a balun transformer has been used as the mixer 7, and the mixer 7 is connected to the RF amplifier 6, the TV output section 8, and the RF modulator 9.

When performing normal reception by a television receiver, U) IF or VH received by the television antenna 1
The antenna signal of F is amplified by the RF amplifier 2, distributed by the distributor 3, roughly amplified by the RF amplifier 6, and sent to the TV via the signal path shown by arrow A in FIG.
The signal is sent from the output section 8 to the antenna signal input section of the television receiver. Further, one of the attenuator signals distributed by the distributor 3 is sent to a tuner in the VTR, and when in the recording mode, the tuner selects a channel and records the video.

In the VTR playback mode, RF is transmitted from the playback circuit inside the VTR.
A video signal and an audio signal (A/V signal) are sent to the modulator 9. The RF modulator 9 emits a carrier wave corresponding to the U) IF vacant channel (usually 36 channels) of the television, modulates this carrier wave with the A/V signal, and outputs it to the mixer 7. The output signal from the RF modulator 9 is output from the mixer 7 to the TV output section 8 through a path indicated by an arrow V, and is further sent to the antenna signal input section of the television receiver.

In this way, this type of RF modulator integrated with an antenna booster/mixer has 36 channels, etc.
An IF vacant channel can always be used as a VTR re-main channel, eliminating the need for switching between television reception mode and VTR playback mode.

[Problem that the invention seeks to solve]

As described above, in conventional integrated RF modulators, a balun transformer is often used as the mixer 7 because it is low cost and easy to mount on a board.

However, when a balun transformer is used as the mixer 7, even if the impedances of the TV signal system (path A) and the RF modulator signal system (path V) and the TV output section 8 are matched, the mutual isolation is (isolation) becomes low. FIG. 10 is a graph showing isolation characteristics when a balun transformer is used.

The horizontal axis is the reception frequency, and the vertical axis is the isolation.

The frequency band indicated by the dashed line is the transmission frequency band (around 36 channels) by the RF modulator.As shown in this graph, when a balun transformer is used, the isolation is generally lO~15d.
You will only be able to get a grade of B.

Further, when the antenna signal system and the RF modulator signal system are outputted via the balun transformer, a distribution loss of about 4 to S dB occurs for each, and there is a possibility that the image quality of the television receiver will deteriorate.

In particular, there is a risk that the image quality will be noticeably degraded in the television receiver.

Furthermore, as shown in the graph of FIG. ~900M
H2) Since the balun transformer must distribute the antenna signal to the TV output section 8 with low loss in this wide frequency band, the above-mentioned isolation is almost constant over this wide frequency band. be. Therefore, for example, when a high-level antenna signal at a frequency lower than the frequency output from the RF modulator 9 (approximately 36 channels), for example, a VHF frequency, flows into the RF modulator 9 via the mixer 7, the antenna signal and the RF modulator Intermodulation (Int
er Modulation), and there is a problem in that beats and the like occur on the screen of a television receiver.

As a measure to prevent this intermodulation, as shown in FIG. 9, a filter 10 may be provided to prevent antenna signals such as VHF from flowing into the RF modulator 9. However, this measure has the drawback of increasing the number of components to be mounted and increasing costs.

The present invention solves the above-mentioned conventional problems, and can output antenna input signals to a television receiver without loss, and even if high-level antenna signals are input, RF
The present invention provides an antenna booster mixer that does not cause large intermodulation with the output signal of a modulator.

[Specific means for solving the problem] The antenna booster mixer according to the present invention has an antenna input signal line in which one end is an input end for an amplified antenna signal and the other end is an output end to a television receiver. , a coupling part provided in parallel with the signal line and having one end connected to a signal output part from the RF modulator, and the direction of the antenna signal in the signal line and the direction of the modulator signal in the coupling part are the same direction. This is what has become.

[For production]

In this antenna booster mixer, when the television receiver is in reception mode, the antenna signal is output to the television receiver through the antenna input signal line without loss. In the VTR playback mode, the output signal from the RF moderator modulated by the A/V signal is output from the coupling section through the signal line to the television receiver with some loss. Furthermore, since the coupling part and the signal line are arranged with the same directionality, even if a high-level antenna input signal is input in VTR playback mode, this antenna signal is greatly attenuated and input to the coupling part. Therefore, the problem of image beat due to intermodulation between the antenna signal and the output signal of the RF modulator does not occur.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described with reference to the drawings of FIGS. 1 to 7.

Fig. 1 is a block diagram showing the circuit configuration of an RF modulator integrated with an antenna booster mixer equipped with a mixer according to the present invention, and Figs. 2 to 6 show the specific structure of the mixer for each embodiment. It is something that

In FIG. 1, reference numeral 1a represents an antenna input terminal;
The signal from TV antenna 1 is connected to this antenna input terminal 1.
input to a. Reference numeral 2 is an RF amplifier, and 3 is a distributor. The antenna signal is distributed by a distributor 3 to an output section 4 to a tuner in the VTR and a booster mixer 15.

Booster mixer 15 includes RF amplifier 6 and mixer 17.

The mixer 17 includes an antenna input signal line 17a and a coupling section 17b. One end of the signal line 1a is an input end for an antenna signal, and the other end is an output end. The input end is connected to the RF amplifier 6, and the output end is connected to the TV output section 8. Furthermore, one end of the coupling portion 17b is connected to the RF modulator 9, and the other end is connected to the resistor 18.
is grounded through. In this mixer 17, the direction of the antenna signal path in the signal line 17a (direction A) is the same as the direction of the output path from the RF modulator leading to the coupling portion 17b (direction V).

The operation will be explained.

The antenna signal received by the TV antenna 1 is
One of the zero-divided antenna signals amplified by the RF amplifier 2 and distributed by the distributor 3 is input to a tuner in the VTR.

In the VTR recording mode, channels are selected and recorded by this tuner. The other distributed antenna signal is amplified by the RF amplifier 6 and input to the signal line 17a. In the reception mode of the TV receiver, the antenna signal in the frequency band (40 to 900 MHz) from the VHF low channel to the υI (F high channel) passes through the signal line 1a and is delivered to the TV output section without loss. 8
and is input to the antenna signal input section of the television receiver.

In addition, in the playback mode of the VTR, the RF modulator 9 emits a carrier wave in the UHF frequency band corresponding to the available TV channels (around 36 channels), and this carrier wave is used to transmit the video and audio signals from the playback circuit in the VTR ( ^
/V signal) and input to the coupling section 17b. Then, the RF modulator output, which is slightly attenuated (about 6 B) due to the insertion loss from the coupling section 17b to the signal line 17a, is output from the TV output section 8 and input to the antenna input section of the television receiver.

As mentioned above, the direction of the antenna signal path of the signal line 17a (direction A) and the direction of the output path from the RF modulator of the coupling section 17b (direction V) are the same, and this mixer 1f Since it has directionality, even if the antenna signal that becomes the path in the A direction flows into the RF modulator 9 via the coupling part 17b (path indicated by AI),
Due to the directionality of the coupling portion 17b, the antenna signal flowing into the RF modulator 9 is significantly attenuated (for example, about 20 dB). Therefore, in the VTft reproduction mode, even if an antenna signal with a higher level and a lower frequency than the output signal of the RF modulator is input, the intermodulation between this antenna signal and the output signal from the RF modulator can be reduced. On the contrary, there is the above-mentioned direction.

The lag (path indicated by Vt) of the output signal from the RF modulator 9 to the antenna circuit is also significantly attenuated (for example, about 20 dB).

The graph shown in FIG. 7 shows the insertion loss and isolation characteristics of the mixer 17, where the horizontal axis shows the reception frequency and the vertical axis shows the insertion loss and isolation in the mixer 1f. Further, the broken line occlusion indicates the frequency band of the carrier wave emitted by the RF modulator 9. As shown in this graph, in the mixer 17, the coupling characteristic between the signal line 1 fa and the coupling part 1 fi is the best (6 dB) in the frequency band of the output of the RF modulator 9 (around 36 channels).
(insertion loss), and the coupling characteristics can be set to deteriorate in a frequency band lower than that. Also, as shown in this graph, the isolation can be sufficiently large (26 dB around 36 channels).
degree). By setting in this manner, even if a low frequency and high level antenna signal such as a VHF low channel is input, the antenna signal will be significantly attenuated and input to the coupling portion 17b. Therefore, especially V
Intermodulation between a low frequency antenna signal such as the HF low channel and the output signal of the RF modulator can be significantly reduced, and beat disturbances on the television screen will no longer occur. Also, from VHF low channel to UHF
Frequency band up to the high channel (40-900M)
The antenna signal of Iz) is directly connected to the TV from the signal line 17a.
It is output to the output section 8. Therefore, in the television receiver, the antenna signal is unrelated to the insertion loss and isolation characteristics shown in FIG. 7, and is output to the television receiver without attenuation.

Next, the concrete structure of mixer 1 will be explained.

In the embodiment shown in FIG. 2, the antenna input signal line 17
a and the coupling portion 17b connected to the RF modulator are both made of metal plates. The signal line 17a and the coupling portion 17b are erected on the printed circuit board 21 with a gap therebetween. Both ends of the signal line 17a are electrically connected to conductor patterns 22a and 22b, and one pattern 22a
is connected to the RF amplifier 6, and the other pattern 22b is connected to the RF amplifier 6.
It is connected to the V output section 8. Both ends of the coupling portion 17b are also connected to conductive patterns, and one of the ends of the connecting portion 17b is
is connected to the output section of the RF modulator 9. Furthermore, an earth pattern 24 for forming distributed capacitance and for shielding is formed on the back surface of the printed circuit board 21.

In the embodiment shown in FIG. 3, the antenna input signal line 17
A is formed by a conductive pattern on the printed circuit board 21. The coupling portion 1b is a metal plate, and the coupling portion 17b faces the signal line 17a with a gap therebetween.

Note that 24 is a ground pattern.

In the embodiment shown in FIG. 4, two printed circuit boards 21a and 21b are used, and one printed circuit board 21a has a signal line 17a formed by a conductive pattern, and the other printed circuit board 21b has a connecting portion formed by a conductive pattern. 17b
The two printed circuit boards 21a and 21b on which are formed are stacked with an insulating sheet 25 in between, so that the signal line 17a and the coupling part 17b face each other with the insulating sheet 25 in between. At this time, as shown in FIG.
b with the connecting fittings 26, and both printed circuit boards 21a
and the ground pattern 24a formed on the back surface of 21b.
, 24b are electrically connected to each other by the connecting fitting 26, thereby making it possible to improve the shielding performance.

The embodiment shown in FIG. 6 can be manufactured at the lowest cost, and the antenna input signal line 17a and the coupling portion 17 are
b are both formed of conductive patterns.

(Effects of the Invention) In the present invention, the antenna signal can be output from the TV output section without attenuation, and the antenna signal and RF
Intermodulation with the modulator is also less likely to occur. Further, unlike mixers using conventional balun transformers, there is no need to provide a filter to prevent antenna signals in a low frequency band from being input to the RF modulator, and the mixer can be manufactured at low cost.

[Brief explanation of drawings]

1 to 7 show embodiments of the present invention, and FIG. 1 shows an antenna booster equipped with a mixer according to the present invention.
A block diagram showing the circuit configuration of an RF modulator integrated with a mixer, Fig. 2 is a perspective view showing a first embodiment of the specific structure of the mixer, and Fig. 3 is a second embodiment of the specific structure of the mixer. 4 is an exploded perspective view showing the third embodiment of the specific structure of the mixer, FIG. 5 is a sectional view showing the assembled state, and FIG. 6 is a perspective view of the specific structure of the mixer. A perspective view showing the fourth embodiment, FIG. 7 is a diagram showing the insertion loss and isolation characteristics of the mixer according to the present invention, and FIGS. 8 and 9 show an antenna booster mixer equipped with a conventional mixer and FIG. 10 is a block diagram showing a circuit configuration of an integrated RF modulator, and a diagram showing isolation characteristics in a conventional mixer. 6-RF amplifier, 8-TV output section, 9-RF modulator, 17...mixer, 17a--signal line for antenna input, 17b...coupling section. Figure 2 Figure 3 17b... Department extension Figure 6 Figure 7 Figure 9 Figure 10

Claims (1)

[Claims] An antenna input signal line with one end serving as an input end for the amplified antenna signal and the other end serving as an output end to the television receiver, and one end connected to the signal output section from the RF modulator. an antenna booster/mixer comprising a coupling section, wherein the direction of the antenna signal in the signal line and the direction of the modulator signal in the coupling section are the same.