JP3097278B2 - 2-band electronic tuner used for PCM music broadcasting receiver for CATV - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-band electronic tuner for use in a PCM music broadcast receiver for CATV, which receives PCM music broadcasts via CATV or the like.

[0002]

2. Description of the Related Art In recent years, high-quality music of a compact disc has been converted to CAT by using a digital modulation technique by using an empty channel allocated to a CATV.
A new service has been started to be sent to individual subscribers via the V cable. In order to spread this service smoothly, there is a demand for the development of an optimal electronic tuner capable of receiving multi-channel PCM music broadcasts transmitted via a CATV cable.

Hereinafter, an electronic tuner used in a conventional PCM music broadcast receiver for CATV and peripheral devices thereof will be described with reference to the drawings.

FIG. 6 shows a block diagram of the entire CATV receiving system. In FIG. 6, reference numeral 30 denotes a CATV broadcasting company, and a CAT broadcast from the CATV broadcasting company 30.
The V broadcast is distributed by the distributor 34 from the cable trunk line 31 and sent to each individual contractor's house 33 via the branch line 32.

At each individual subscriber's house 33, as shown in FIG. 7, a broadcast signal transmitted from a branch line 32 is further distributed by a distributor 21, and one of the signals is transmitted via a CATV receiver 22 to a television set. The image is supplied to the image receiver 23 and received.
The other signal of the distributor 21 is input to the PCM music broadcast receiver 20 for CATV. The two output signals 8a and 8b are amplified by the audio amplifier 24 and drive the speakers 25 and 26, respectively.

Also, a PCM music broadcast receiver 2 for CATV
0, as shown in FIG. 8, an input terminal 1, a tuning electronic tuner 3 connected to the input terminal 1, an intermediate frequency filter 4 connected to an output 3 c of the electronic tuner 3,
Demodulator 5 connected to the output of intermediate frequency filter 4
A decoder 6 connected to the output of the demodulator 5; a D / A converter 7 connected to the output of the decoder 6;
Output terminals 8 respectively connected to the two outputs of the A / A converter 7
a, 8b.

As shown in FIG. 9, the electronic tuner 3 has an input terminal 3a of the tuner, an input tuning circuit 3p connected to the input terminal 3a, and an input tuning circuit 3p.
, An inter-stage tuning circuit 3r connected to the output of the RF amplifier 3q, a mixer 3s having the output of the inter-stage tuning circuit 3r connected to one input, An intermediate frequency tuning circuit 3t connected to the output of the mixer 3s, an output terminal 3c of a tuner connected to the output of the intermediate frequency tuning circuit 3t, and a local unit connected to the other input of the mixer 3s. A first tuner block including an oscillation circuit 3u, an electronic tuning control circuit 3v that outputs a tuning voltage 3x and a band switching signal 3y based on a tuning command signal 3b from the outside, and a first tuner block An input tuning circuit 3pa connected to the input terminal 3a for receiving a UHF band broadcast in parallel with the RF amplifier 3q connected to an output of the input tuning circuit 3pa.
a, an inter-stage tuning circuit 3ra connected to the output of the RF amplifier 3qa, a mixer 3sa having the output of the inter-stage tuning circuit 3ra connected to one input portion, and a mixer 3sa
a, an intermediate frequency amplifier 3z connected to the output of the intermediate frequency amplifier 3z, the intermediate frequency tuning circuit 3t connected to the output of the intermediate frequency amplifier 3z, and a local oscillation circuit 3ua connected to the other input of the mixer 3sa. And a second tuner block as shown by a broken line constituted by the electronic tuning control circuit 3v for outputting a tuning voltage 3xa based on the tuning command signal 3b from the outside. Reference numeral 3w is a crystal oscillator that gives a reference frequency to the electronic tuning control circuit 3v.

[0008]

However, the CAT
As for music serviced by V-channel multi-channel PCM music broadcasting, dozens of programs are transmitted using digital compression technology or the like, and a plurality (for example, 6 MHz) of dedicated bandwidth (for example, 6 MHz) of one channel of standard television broadcasting. (10 programs) High quality music equivalent to a compact disc of programs is multiplexed.

Therefore, for example, when performing multi-channel PCM music broadcasting of about 50 programs, the required channels are:
50 ÷ 10 = 5 instantaneously for 5 channels. This is (6x
5 = 30 MHz) is sufficient.

FIG. 10 schematically shows the band division of a 4-band tuner (54 to 890 MHz) and a 3-band tuner (54 to 810 MHz) used in a conventional television receiver and a reception frequency region. (90-10
8 MHz) and a CATV broadcast band (54 to 560 MHz) assigned to CATV broadcasting in the United States.

[0011] Since multi-channel PCM music broadcasting for CATV is performed using an empty channel in the CATV broadcasting band, if a 4-band tuner or 3-band tuner for television reception is used as it is, at least 560 MHz or more. No receiving function is required.

[0012] In this way, the conventional electronic tuner had a problem that really becomes a high price for that had the performance you do not want to use in reality.

Therefore, the present invention provides a low-priced CATV P
An object of the present invention is to provide a two-band electronic tuner used for a CM music broadcast receiver.

[0014]

To achieve the above object, a two-band electronic tuner used in a PCM music broadcast receiver for CATV according to the present invention comprises an input terminal of a tuner and an input terminal connected to the input terminal. A tuning circuit, an RF amplifier connected to the output of the input tuning circuit,
An interstage tuning circuit connected to the output of the amplifier, a mixer having the output of the interstage tuning circuit connected to one input, an intermediate frequency tuning circuit connected to the output of the mixer, An output terminal of a tuner connected to the output of the frequency tuning circuit, and a local oscillation circuit connected to the other input of the mixer, wherein the mixer has an oscillation frequency output from the local oscillation circuit. By performing frequency conversion, the output frequency is set to approximately 44.0 MHz, and the frequency of the signal input to the input terminal is a first band that can be continuously received from approximately 72 MHz to approximately 2.2 times the frequency. And a second band in which the frequency of the signal input to the input terminal can be continuously received from approximately 1/2/2 of the highest frequency of the CATV broadcast frequency to the highest frequency, and First And a band switching means for electrically switching between the second band and the second band.

[0015]

According to this structure, the second tuner block for receiving the UHF band as shown by a broken line is not required, so that a two-band electronic tuner used for a low-priced CATV PCM music broadcast receiver is provided. be able to.

[0016]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of a PCM music broadcast receiver 40 for CATV using the two-band electronic tuner of the present invention. As shown in FIG. 2, the PCM music broadcast receiver 40 for CATV includes an input terminal 41, a two-band tuning tuner 43 of the present invention connected to the input terminal 41,
An intermediate frequency filter 44 connected to the output 43c of the electronic tuner 43; a demodulator 45 connected to the output of the intermediate frequency filter 44; a decoder 46 connected to the output of the demodulator 45; A D / A converter 47 connected to the output of the converter 46, and output terminals 48a, 48b connected to two outputs 47a, 47b of the D / A converter 47, respectively.
48b.

Also, the two-band electronic tuner 43 of the present invention.
Is a tuner input terminal 43a, as shown in FIG.
The input tuning circuit 43p connected to the input terminal 43a
The RF amplifier 43q connected to the output of the input tuning circuit 43p, the inter-stage tuning circuit 43r connected to the output of the RF amplifier 43q, and the output of the inter-stage tuning circuit 43r connected to one input unit. Mixer 43s and an intermediate frequency tuning circuit 43t connected to the output of the mixer 43s.
A tuner output terminal 43c connected to the output of the intermediate frequency tuning circuit 43t, a local oscillation circuit 43u connected to the other input of the mixer 43s, and a tuning command signal 43b from the outside. Electronic tuning control circuit 4 for outputting tuning voltage 43x and band switching signal 43y
3v. Reference numeral 43w is a crystal oscillator that gives a reference frequency to the electronic tuning control circuit 43v.

The mixer 43s converts the oscillation frequency output from the local oscillation circuit 43u into an output frequency of about 44.0 MHz by performing frequency conversion.
The frequency of the signal input to the input terminal 43a is approximately 72
A first band that can be continuously received from MHZ to about 2.2 times the frequency, and a frequency of a signal input to the input terminal 43a is about 1/2 times the highest frequency of the CATV broadcast frequency. From the first band to the highest frequency, and a band switching means for electrically switching between the first band and the second band. It is.

The two-band electronic tuner thus configured is different from the conventional example shown in FIG. 9 in that the UHF band receiving circuit block is omitted and the control for band switching shown in FIG. 9 is performed. The signal drive 3y is also simplified as compared with the television receiving 3-band / 4-band switching electronic tuner.

Further, the two-band electronic tuner of the present invention comprises:
It is possible to continuously receive at least from 72 MHz to at least the maximum frequency of the US FM broadcasting frequency (this is the first frequency).
Band). In other bands, CATV
Can receive, including the highest frequency f _H of the broadcast frequency, the received lower limit frequency f _L satisfies the f _L ≦ 1/2 · f _H, can continuously receive the frequency domain to the f _H from this f _L (This is called the second band). Here, the first band and the second band are electrically switched by the band switching signal 3y, and in any case, the intermediate frequency is 44.0 MHz.

PCM for CATV constructed as described above
The reason why the two-band electronic tuner used for the music broadcasting receiver can be sufficiently used as the two-band electronic tuner used for the PCM music broadcasting receiver for CATV will be described below.

FIG. 3 shows one channel (6) of the NTSC system.
(MHz), the video carrier f _VIF (45.75 MHz) and its occupied bandwidth are indicated by hatching, and the audio sub-carrier f _SIF
(41.25 MHz) is also assigned independently of f _VIF . Here, it is shown at the intermediate frequency.

FIG. 4 shows an intermediate frequency f _IFPCM (4) of a phase-modulated signal used for multi-channel PCM music broadcasting.
(4.0 MHz). Here, an example is shown in which the dedicated bandwidth is 3.0 MHz. For example, PCM music on a compact disk is digitally compressed and multiplexed into about five programs.

As can be seen by comparing FIGS. 3 and 4, in the case of the phase modulation, the modulation spectrum is uniformly distributed above / below on the frequency axis. It is the center of 6.0 MHz. We are choosing to 44.0MHz intermediate the substantially f _VIF and f _SIF at IF frequencies.

Here, since the multi-channel PCM music broadcast for CATV is broadcast using an empty channel which is not used in the conventional CATV, a portion which is originally unsuitable for transmitting a video carrier becomes an empty channel. ing.

For example, 72 to 76 MHz is a frequency region in which no channel is allocated originally,
0 to 108 MHz is rarely used.

Further, a higher frequency region (for example, 350 to
570 MHz) increases the transmission loss of the cable,
It is not desirable from the noise limiting sensitivity of the receiver itself, and care is taken not to use it as much as possible.

Naturally, the frequency domain allocated to the CATV multi-channel PCM music broadcast is 2 as described above.
Regions, 72-108 MHz and 350-570
MHz is targeted.

On the other hand, in the case of a single super electronic tuner, the frequency range in which one band can be received (f _L : lower limit, f _L ) is determined by the capacitance change ratio of the variable capacitance diode (varicap diode) used and the limitation of the tuning circuit using the same.
f _H: upper limit) is approximately f _H ≒ 2.2 × f _L.

Lower limit frequency f_1LIs 72 MHz, f
_1H= 158 MHz. Also, one of the higher frequency regions
The upper limit frequency f_2HAs its lower limit
Wave number f_2LIs f_2L= 1 / 2.2 · f_2HTo f_2H= 570
F assuming MHz _2L= 260 MHz.

As described above, the upper limit of the FM band from 72 MHz can be realized by one band, and the high frequency range of CATV broadcasting (350 to 570 MHz)
Can be received in one band, and the two-band electronic tuner of the present invention can be provided as an electronic tuner used for a CATV multi-channel PCM music broadcast receiver.

FIG. 5 shows a multi-channel P for CATV according to the present invention.
The reception frequency of the two-band electronic tuner used for the CM music broadcast receiver is shown.

This is an electronic tuner having a two-band switching configuration of, for example, one band including an FM broadcast band from 72 MHz and another band capable of receiving a high frequency region of CATV broadcast.

Further, the two-band electronic tuner is provided with a CA
For a frequency range (for example, 30 MHz) required for TV multi-channel music broadcasting, in the case of 72 to 158 MHz,
86 MHz and 31 for 260 MHz to 570 MHz
0 MHz frequency range, and the frequency allocation necessary for CATV multi-channel music
The present invention provides a function that can be freely assigned with sufficient time to one band and that can be sufficiently expanded even when the number of programs needs to be increased in the future.
It turns out that band electronic tuners can be fulfilled.

At the same time, the tuner has two bands, so that the band switching operation of the tuner is simplified as compared with the four-band switching system or the three-band switching system, and the peripheral circuits for channel selection can be greatly rationalized.

[0037]

As described above, according to the present invention, the mixer of the two-band electronic tuner converts the frequency with the oscillation frequency output from the local oscillation circuit, and changes the output frequency to approximately four.
The first band that can be continuously received from a frequency of approximately 72 MHz to approximately 2.2 times the frequency of a signal input to the input terminal is set to 4.0 MHz, and the frequency of the signal input to the input terminal is CATV. 1. Approximately the highest broadcast frequency
A configuration having band switching means for enabling reception of a second band that can be continuously received from half to the highest frequency and for electrically switching between the first band and the second band; Therefore, the second tuner block for receiving the UHF band is unnecessary,
Used for low-priced CATV PCM music broadcast receivers 2
A band electronic tuner can be provided.

Further, since the components of the UHF band receiving circuit block are not required, the size can be reduced accordingly.

Furthermore, since the band switching process is simplified, there is an effect that the size of the peripheral circuit for channel selection can be reduced and the price can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a two-band electronic tuner used in a PCM music broadcast receiver for CATV according to the present invention.

FIG. 2 is a block diagram of a PCM music broadcast receiver for CATV using the same two-band electronic tuner.

FIG. 3 is an NTSC system IF spectrum distribution diagram.

FIG. 4 is an IF spectrum distribution diagram of a phase modulation method.

FIG. 5 is a diagram showing a reception frequency of the two-band electronic tuner of the present invention.

FIG. 6 is a block diagram of the entire CATV receiving system;

FIG. 7 is a block diagram of a PCM music broadcast receiving system for CATV.

FIG. 8: PC for CATV using a conventional electronic tuner
Block diagram of M music broadcast receiver

FIG. 9 is a block diagram of an electronic tuner used in a conventional PCM music broadcast receiver for CATV.

FIG. 10 is a diagram showing a reception frequency of an electronic tuner for television.

[Explanation of symbols]

 43 two-band electronic tuner 43a tuner input terminal 43p input tuning circuit 43q RF amplifier circuit 43r interstage tuning circuit 43s mixer 43t intermediate frequency tuning circuit 43u local oscillator

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/06-1/26 H04N 5/44 H04N ⁷ /00-7/16

Claims (1)

(57) [Claims] 1. An input terminal of a tuner, an input tuning circuit connected to the input terminal, an RF amplifier connected to an output of the input tuning circuit, and an interstage tuning circuit connected to an output of the RF amplifier. A mixer in which the output of the interstage tuning circuit is connected to one input, an intermediate frequency tuning circuit connected to the output of the mixer, and a tuner connected to the output of the intermediate frequency tuning circuit. An output terminal, and a local oscillation circuit connected to the other input unit of the mixer, wherein the mixer substantially converts an output frequency by performing frequency conversion with an oscillation frequency output from the local oscillation circuit. 44.
0 MHz, a first band in which the frequency of the signal input to the input terminal can be continuously received from approximately 72 MHz to approximately 2.2 times the frequency, and the frequency of the signal input to the input terminal is CATV. It is possible to receive a second band that can be continuously received from about 1/2/2 of the highest frequency of the broadcast frequency to the highest frequency, and to electrically connect the first band and the second band. A two-band electronic tuner for use in a PCM music broadcast receiver for CATV having band switching means for selectively switching.