JPH11177456A - Tuner shared for digital and analog broadcast signals - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate adverse effects on NTSC demodulation when receiving an analog broadcast program by suppressing spurious radiation from a base-bend demodulation section. SOLUTION: This tuner shared for digital and analog broadcast signals comprises a signal input terminal 14, a frequency conversion section 11 that coverts an input signal into an IF signal, a changeover distribution circuit section 55 that selects a transmission destination of the IF signal depending on the kind (analog/digital) of the received signals and distributes the signals, a base-band demodulation section 35 that base-band demodulates the IF signal into an I signal, an output terminal 43 for the I signal, and includes an output terminal 44 for the If signal. Each component is accommodated in a case 10 which acts like an electromagnetic shield and operations of the changeover distribution section 55 and/or of the base-band demodulation section 35 are controlled by control signals fed from the components in the case 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital / analog shared tuner for selectively receiving a digitally modulated television signal and an analogly modulated television signal.

[0002]

2. Description of the Related Art At present, digitalization of broadcasts is progressing, and receivers capable of receiving both analog and digital broadcasts are being developed.

In the United States, 8VSB (8 Vesti) is used as a digital modulation method for terrestrial waves.
gear sideband). 8V
SB is the same CH as the conventional analog broadcasting (NTSC).
Because of the bandwidth, the conventional front end can be used almost as it is.

FIG. 5 shows an example of a front end system (front end to demodulation circuit) of a conventional digital / analog shared tuner. FIG. 5 shows a digital / analog shared front end system (front end to demodulation circuit) adopting the double conversion method, and includes a frequency conversion unit 61, a switch unit 82, and a baseband demodulation unit 8.
5, an A / D converter 95, a VSB demodulator 96, and an NTSC demodulator 98. In the conventional example, the signal input terminal 64, the frequency converter 61, and the IF output terminal 81 are referred to as a "digital / analog shared tuner".

The frequency conversion unit 61 further includes a first conversion unit 6
2. It can be divided into a second conversion unit 63. The first converter 62 includes an RF amplifier 65, a first mixer 6
6. Band pass filter (BPF, Band Pas)
s Filter) 67, a first IF amplifier 68, a band-pass filter 69, a first PLL circuit 72, and a first local oscillator 73.

First, an input signal from the input terminal 64 is R
Broadband amplification is performed by the F amplifier 65. Next, the output and the first PLL control data 70 are transmitted via the terminal 71 to the first PLL control data 70.
The first local oscillator 73 generates a 1st Local signal based on a signal supplied from the first PLL circuit 72 to the L circuit 72. 1st Loca created by first PLL circuit 72
The 1 signal is added to a first local oscillator 73 and multiplied by a first mixer 66 to upconvert to a 1st IF signal. After the first IF signal is band-limited by the band-pass filter 67, it is amplified by the first IF amplifier 68, band-limited by the band-pass filter 69, and output.

The second converter 63 includes a second mixer 74, a second IF amplifier 75, a band pass filter (BPF) 76,
It comprises a second local oscillator 80 and a second PLL circuit 79. The second PLL control data 77 is applied to the second PLL circuit 79 via the terminal 78,
9 to the second local oscillator 80 for 2nd Lo.
Create a cal signal. Next, the output from the band-pass filter 69 of the first conversion unit 62 and the 2nd Local signal are multiplied by a second mixer 74 to downconvert to a 2nd IF signal. 2nd
The IF signal is broadband amplified by an RF amplifier 75, band-limited by a bandpass filter 76, and then output.

[0008] In the switch section 82, based on a control signal 97 corresponding to the type of received signal (analog / digital), I
The transmission destination of the F signal is being switched. The digital broadcast signal is connected to a terminal 84 side by a switch unit 82 and becomes an input signal to a baseband demodulation unit 85. On the other hand, the analog broadcast signal is connected to the terminal 83 side by the switch unit 82 and becomes an input signal to the NTSC demodulator 98 directly via the terminal 94.

The baseband demodulator 85 includes a band pass filter (BPF) 86, a digital IF amplifier 87,
It comprises an I signal demodulation mixer (mixer) 88, a Q signal demodulation mixer (mixer) 89, a 90-degree phase shifter 90, a baseband local oscillator 91, and a phase comparison mixer (mixer) 92. .

In this case, first, the band necessary for baseband demodulation is limited by a band-pass filter (BPF) 86, amplified by a digital IF amplifier 87, and then the signal is mixed with an I signal demodulation local mixer 88 and an I signal. The signal is input to the local mixer 89 for demodulation. I signal demodulating local mixer 88 and I
The signal generated by the baseband local oscillator 91 and the signal obtained by passing the signal through the 90-degree phase shifter 90 are input to the signal demodulation local mixer 89. As a result of multiplication, the I signal , Q signal.

Here, since it is necessary that the phase of the pilot carrier included in the input signal and the phase of the baseband local oscillator 91 must completely match, the I signal and the Q signal are mixed by a phase comparison mixer ( A mixer 92 detects the phase error and uses it to control the phase of the baseband local oscillator 91. Since only the I signal is used in the VSB demodulation, the baseband demodulation unit 85 outputs only the I signal to the A / D conversion unit 95.

The A / D converter 95 converts the I signal from the baseband demodulator 85 into a digital signal.

VSB (Vestial sideb)
and) The demodulation unit 96 performs VSB demodulation of the digital signal from the A / D conversion unit 95 and outputs a transport stream signal.

In the NTSC demodulation section 98, the switch section 82
, And performs NTSC demodulation.

In the conventional front-end system, the frequency conversion unit 61 is housed in one casing 60 having an input terminal 64 and an IF output terminal 81, and is used as a digital / analog shared tuner. Was placed on top.

Further, in the conventional digital / analog common tuner front-end system, a control signal for performing digital / analog switching includes an analog processing system up to a baseband demodulator 85 and an A / D converter. 9
The control signal 97 common to the digital processing system 5 and subsequent was used.

[0017]

However, the conventional digital / analog shared tuner has the following problems.

In the prior art, when receiving a digital broadcast, a baseband demodulator, a VSB demodulator and an A / D converter are arranged on the same substrate, and the same control signal causes
Since the baseband demodulation unit is controlled, the baseband demodulation unit is easily affected by noise generated in a digital processing system at the subsequent stage, and adversely affects characteristics such as the accuracy of the local oscillation frequency of the local oscillation unit of the baseband demodulation unit.

Further, since the baseband demodulation unit is not covered by the housing, unnecessary radiation generated from the case has been a problem.

In addition, the baseband demodulation unit operates during analog broadcast reception, which causes a problem during NTSC demodulation, which is a problem. The present invention has been made in view of solving these problems.

[0021]

According to a first aspect of the present invention, there is provided a digital / analog shared tuner having a signal input terminal, a frequency converter for converting an input signal into an IF signal, and a type of received signal (analog / digital). A switching distribution unit for switching or distributing a transmission destination of an IF signal; a baseband demodulation unit for further baseband demodulating the IF signal into an I signal;
A signal output terminal, and an IF signal output terminal,
A signal input terminal, a frequency converter,
The switching distribution unit, the baseband demodulation unit, the output terminal of the I signal, and the output terminal of the IF signal are housed in one housing that acts as an electromagnetic seal, and are controlled by control signals from components in the housing. , And controls the operation of the switching distribution unit or the operation of the baseband demodulation unit.

[0022] Further, according to claim 2 of the present invention, the digital
The analog shared tuner is characterized in that the switching distribution unit is constituted by a switch unit.

Further, according to the third aspect of the present invention, the digital
The analog shared tuner uses a control voltage of a PLL circuit of the frequency conversion unit for a control signal by a component in the housing for controlling the operation of the switching distribution unit or the operation of the baseband demodulation unit. It is characterized by the following.

Further, according to a fourth aspect of the present invention, the digital
The analog shared tuner is characterized in that when receiving an analog signal, the operation of the baseband demodulation unit is stopped by stopping at least a part of power supply to the baseband demodulation unit.

Further, according to claim 5 of the present invention,
The analog shared tuner is characterized in that when an analog signal is received, the operation of the baseband demodulator is stopped by supplying a stop signal to an operation stop terminal of the baseband demodulator.

Further, according to claim 6 of the present invention,
The analog shared tuner is characterized in that the switching distributor is configured by a distributor.

Further, according to a seventh aspect of the present invention, there is provided a digital
The analog shared tuner is characterized in that when receiving an analog signal, the baseband demodulation operation is stopped by stopping at least a part of power supply to the baseband demodulation unit.

Further, in the digital / analog shared tuner according to claim 8 of the present invention, when the analog signal is received, the operation of the baseband demodulation unit is stopped by sending a stop signal to the operation stop terminal of the baseband demodulation unit. It is characterized by performing by supply.

[0029]

1 to 4 are circuit block diagrams showing a digital / analog shared front end system (front end to demodulation circuit) according to an embodiment of the present invention. Will be described with reference to the drawings.

FIG. 1 is a digital / analog shared front-end system (front end to front-end) including a digital / analog shared tuner circuit according to an embodiment of the present invention.
FIG. 3 is a circuit block diagram illustrating a demodulation circuit). In FIG. 1, a digital / analog shared front-end system (front end to demodulation circuit) employs a double conversion system, and a frequency conversion unit 11 and a transmission destination of an IF signal depending on the type of received signal (analog / digital). And a switching distribution unit 55 for switching or distributing the data, a baseband demodulation unit 35, an A / D conversion unit 45, a VSB demodulation unit 46, and an NTSC demodulation unit 48.

In the present invention, the housing 10 shown in FIG.
, The input terminal 14, the frequency conversion unit 11, the switching distribution unit 55, and the baseband demodulation unit 3.
5, the circuit up to the I signal output terminal 43 and the IF output terminal 44 is defined as a "digital / analog shared tuner" and used.

A feature of the present invention is a digital / analog shared tuner for receiving both digital broadcasts and analog broadcasts, a signal input terminal 14, a frequency converter 11 for converting an input signal into an IF signal, and a type of received signal ( analog/
Digital), a switching distributor 55 for switching or distributing the transmission destination of the IF signal, a baseband demodulator 35 for further baseband demodulating the IF signal into an I signal, an I signal output terminal 43, and an IF signal output terminal 44. , Including
A signal input terminal, a frequency converter,
The switching distribution unit, the baseband demodulation unit, the output terminal of the I signal, and the output terminal of the IF signal are housed in one housing 10 that acts as an electromagnetic seal, and control signals from components in the housing. Thus, the operation of the switching distribution unit or the operation of the baseband demodulation unit is controlled. In FIG. 1, the control voltage 31 from the second PLL circuit 29 is used as an example of a control signal from a component in the housing 10, whereby the operation of the switching distribution unit 55 or the baseband demodulation is performed. Operation of the unit 35,
Is controlled. As another example of a control signal from a component in the housing 10, a first PLL
A control voltage from circuit 22 can also be used.

The frequency converter 11 further includes a first converter 1
2. It can be divided into the second conversion unit 13. The first converter 12 includes an RF amplifier 15, a first mixer (mixer) 1
6. Band pass filter (BPF, Band Pas)
s Filter) 17, a first IF amplifier 18, a band-pass filter 19, a first PLL circuit 22, and a first local oscillator 23.

An input signal from the input terminal 14 (for example, 5
00 MHz) is first broadband amplified by the RF amplifier 15. Next, the output and the first PLL control data 20 are applied to the first PLL circuit 22 via the terminal 21,
The first local oscillator 23 generates a first local signal based on the signal from the PLL circuit 22. The first local signal generated by the first PLL circuit 22 is converted to a first local oscillator 23.
In addition, the signal is multiplied by a first mixer 16 to up-convert to a first IF signal.
For example, the first IF signal is 945.75 MHz. After the first IF signal is band-limited by the band-pass filter 17, it is amplified by the first IF amplifier 18, band-limited by the band-pass filter 19, and output.

The second converter 13 includes a second mixer 24, a second IF amplifier 25, a band pass filter (BPF, Band Pass Filter) 26,
A second local oscillator 30 and a second PLL circuit 29 are provided. The second PLL control data 27 is applied to a second PLL circuit 29 via a terminal 28, and the second PLL circuit 2
9 to the second local oscillator 30 for 2nd Lo.
Create a cal signal. Next, the output from the band-pass filter 19 of the first conversion unit 12 and the 2nd Local signal are multiplied by a second mixer 24 to downconvert to a 2nd IF signal. For example, the 2nd IF signal is at 45.75 MHz. 2
The nd IF signal is broadband amplified by the RF amplifier 25, band-limited by the band-pass filter 26, and output.

The first IF signal and the second IF signal are respectively 945.75 MHz and 45.75 MHz.
For example, when the reception frequency (input signal) is 500 MHz, the 1st Local signal is 1
445.75 MHz, 1st IF signal is 945.75M
Hz, 2nd Local signal is 900MHz, 2nd
The IF signal is 45.75 MHz. Further, when the receiving frequency (input signal) is 700 MHz, the first Lo
The cal signal is 1645.75 MHz, the first IF signal is 945.75 MHz, the second local signal is 900
MHz and the second IF signal is 45.75 MHz.

Switching distribution section 5 for switching the transmission destination of the IF signal in accordance with the type (analog / digital) of the received signal
5 can be constituted by a switch unit, a distribution unit, or the like. When the switch unit is used, the IF signal can be completely separated, whereas when the distribution unit is used,
It merely distributes the IF signal, and completes the switching of the transmission destination of the IF signal in combination with the stop of the operation of the baseband demodulation unit 55.

The digital broadcasting signal is supplied to the switching distribution unit 55.
Is connected to the terminal 34 side and becomes an input signal to the baseband demodulation unit 35. On the other hand, the analog broadcast signal is connected to the terminal 33 side by the switch unit 32 and becomes an input signal to the NTSC demodulator 48 directly via the terminal 44.

The baseband demodulator 35 includes a band-pass filter (BPF) 36, a digital IF amplifier 37,
It is composed of an I signal demodulation mixer (mixer) 38, a Q signal demodulation mixer (mixer) 39, a 90-degree phase shifter 40, a baseband local oscillator 41, and a phase comparison mixer (mixer) 42. .

Here, first, a band-pass filter (BPF) 36 limits the band necessary for baseband demodulation, amplifies the signal with a digital IF amplifier 37, and converts the signal into a local mixer 38 for I signal demodulation and a Q signal. The signal is input to the local mixer 39 for demodulation. I signal demodulation local mixer 38 and Q
The signal generated by the baseband local oscillator 41 and the signal that has been passed through the 90-degree phase shifter 40 are input to the signal demodulation local mixer 39. As a result of multiplication, the I signal , Q signal.

Here, since it is necessary that the phase of the pilot carrier included in the input signal and the phase of the baseband local oscillator 41 are completely matched, the I signal and the Q signal are mixed by the phase comparison mixer ( A mixer 42) detects the phase error and uses it to control the phase of the baseband local oscillator 41. Since only the I signal is used in the VSB demodulation, the baseband demodulator 35 outputs only the I signal from the output terminal 38.

The A / D converter 45 converts the I signal from the baseband demodulator 35 into a digital signal.

VSB (Vestial sideb)
and) The demodulator 46 performs VSB demodulation of the digital signal from the A / D converter 45 and outputs a transport stream signal as shown in FIG. The output of the VSB transport stream signal indicates a data string encoded according to MPEG2. In a digital / analog shared tuner, after VSB demodulation, each signal is separated by a separation unit at a separation unit, and is decoded by a decoder to become a video signal, an audio signal, and the like. This processing unit is generally called an MPEG processing unit.

In the NTSC demodulation section 48, the switching distribution section 5
5 and performs NTSC demodulation, and outputs the signal from the NTSC demodulation unit 48 as shown in FIG.

Further, as shown in FIG. 1, the digital / analog shared front-end system according to the embodiment of the present invention comprises a signal input terminal 14, a frequency converter 1
1. The switching distribution unit 55, the baseband demodulation unit 35, the I signal output terminal 43, and the IF signal output terminal 44 are housed in one housing 10 that acts as an electromagnetic seal, and the first PLL control is performed. Data input terminal 21, second PLL
It has a control data input terminal 28, and the housing 10 completely separates the "digital / analog shared tuner" up to the baseband demodulator 35 from the digital processing system after the A / D converter 45. .

Furthermore, conventionally, a control signal 97 common to a circuit up to a baseband demodulation unit and a digital processing system after an A / D conversion unit is used as a control signal for switching between digital and analog. However, according to the present invention, the analog / digital switching of the switching distribution unit 55 is 2n
d Using the control voltage 29 of the PLL 27, the A / D converter 4
A configuration is adopted in which the control signal is separated from the control signal 43 of the digital processing system after the first. A / D converter 45, VSB demodulator 46,
And the NTSC demodulation unit 48 is controlled using the same control signal 47.

Thus, when receiving a digital signal,
"Digital / analog shared tuner" and digital processing system can be fully isolated.
A "digital / analog shared tuner" that is resistant to noise from digital processing systems can be realized.

Also, since the baseband demodulation unit 35 is housed in a single casing that acts as an electromagnetic seal,
Unwanted radiation from the baseband demodulation local oscillator 41 to the digital processing system can be suppressed. Further, when receiving an analog signal, the baseband demodulator 35 and the NTSC
Sufficient isolation from the demodulation unit 48 can be obtained.

FIG. 2 is a circuit block diagram showing a digital / analog shared front end system (front end to demodulation circuit) including a digital / analog shared tuner circuit according to another embodiment of the present invention. In FIG. 2, a digital / analog shared front end system (front end to demodulation circuit) adopts a double conversion system, and a frequency conversion unit 11 and a transmission destination of an IF signal depend on a type of a received signal (analog / digital). , A switching distribution unit 55 for switching or distributing the signals, a baseband demodulation unit 35, an A / D conversion unit 45, a VSB demodulation unit 46, and an NTSC demodulation unit 48.

The difference between FIG. 1 and FIG. 2 of the present invention resides in that the switch section 32 is used as the switching distribution section 55. When an analog signal is received, the switch section 32 is controlled by a frequency conversion section. The control voltage 31 of the second PLL circuit 29 is used. Since the switching of the IF signal is completely performed by using the switch unit 32 as the switching distribution unit 55, the stop / start of the operation of the baseband demodulation unit 35 by the control voltage 31 is not controlled.

The operation shown in FIG. 2 is the same as that shown in FIG. In the switch unit 32,
Depending on the type of received signal (analog / digital), the second
The transmission destination of the IF signal is switched based on the control voltage 31 from the PLL circuit 29. The digital broadcast signal is connected to a terminal 34 side by a switch unit 32 and becomes an input signal to a baseband demodulation unit 35. On the other hand, the analog broadcast signal is connected to the terminal 33 side by the switch unit 32 and becomes an input signal to the NTSC demodulator 48 directly via the terminal 44.

In FIG. 2, 10 is a housing, 11 is a frequency converter, 12 is a first converter, 13 is a second converter, 14 is a signal input terminal, 15 is an RF amplifier, and 16 is a first mixer ( Mixer), 17 is a band-pass filter, 18 is a first IF amplifier, 19 is a band-pass filter, 20 is first PLL control data, 21 is an input terminal of first PLL control data, 22 is a first PLL circuit, and 23 is a first local oscillator. , 24 are a second mixer, 25 is a second IF amplifier, 26 is a bandpass filter, and 27 is a second PLL.
Control data, 28 is an input terminal of the second PLL control data,
29 is a second PLL circuit, 30 is a second local oscillator, 31 is a control voltage of the second PLL 29, 32 is a switch unit,
3 is a terminal, 34 is a terminal, 35 is a baseband demodulator, 3
6 is a band pass filter (BPF), 37 is a digital IF amplifier, 38 is an I signal demodulator (mixer), 39 is a Q signal demodulator (mixer), 40 is a 90 degree phase shifter, and 41 is a base. Local oscillator for band demodulation, 42 is a mixer for phase comparison, 43 is I
A signal output terminal, 44 is an IF output terminal, 45 is an A / D converter, 46 is a VSB demodulator, 47 is a control signal of a digital processing system after the A / D converter 45, and 48 is an NTSC demodulator. .

FIG. 3 is a circuit block diagram showing a digital / analog shared front end system (front end to demodulation circuit) including a digital / analog shared tuner circuit according to another embodiment of the present invention. In FIG. 3, a digital / analog shared tuner is a digital / analog shared front end system (front end to demodulation circuit) employing a double conversion method, and includes a frequency conversion unit 11, a switch unit 32, a baseband demodulation unit 35, / D converter 45, VSB demodulator 46, N
And a TSC demodulator 48.

The difference between FIG. 2 and FIG. 3 of the present invention is that a switch circuit 50 is provided on a power supply line 51 to a baseband demodulation unit 35, and a switch unit 32 is provided when an analog signal is received.
The switch circuit 50 is turned off by using the control voltage 31 of the PLL circuit of the frequency conversion unit that controls the switching. This allows the baseband demodulation unit 35 to use the NTSC demodulation unit 4
8 can be suppressed.

When an analog signal is received, a stop signal (that is, the control voltage 31 of the second PLL 29) is supplied to an operation stop terminal 56 provided in the baseband demodulation unit 35, if necessary, so that the baseband demodulation unit Can be stopped. The operation stop terminal 56 is generally
In the case of an IC-based baseband demodulation unit 35 called an enable terminal or a shutdown terminal, a part or all of the function of the baseband demodulation unit 35 is stopped or put into a standby state by supplying a stop signal. This allows the baseband demodulation unit 35 to use the NTSC demodulation unit 4
8 can be suppressed.

Further, in FIG. 3, reference numeral 10 denotes a housing,
Is a first converter, 13 is a second converter, 14 is a signal input terminal, 15 is an RF amplifier, 16 is a first mixer, 17 is a bandpass filter, 18 is a first IF amplifier, and 19 is a bandpass. Filter, 20 is the first PLL
Control data, 21 is an input terminal of the first PLL control data,
22 is a first PLL circuit, 23 is a first local oscillator, 24 is a second mixer, 25 is a second IF amplifier, 26
Is a band-pass filter, 27 is a second PLL control data, 28 is an input terminal of the second PLL control data, 29 is a second PLL circuit, 30 is a second local oscillator, and 31 is 2nd
The control voltage of the PLL 29, 33 is a terminal, 34 is a terminal, 36
Is a band pass filter (BPF), 37 is a digital IF amplifier, 38 is an I signal demodulation mixer,
39 is a mixer for Q signal demodulation (mixer), 40 is a 90 degree phase shifter, 41 is a local oscillator for baseband, 42
Is a mixer for phase comparison, 43 is an I signal output terminal, 44 is an IF output terminal, and 56 is an operation stop terminal.

FIG. 4 is a circuit block diagram showing a circuit configuration of a digital / analog shared tuner according to another embodiment of the present invention. In FIG. 4, a digital / analog shared tuner is a digital / analog shared front-end system (front end to demodulation circuit) employing a double conversion method, and includes a frequency conversion unit 11, a switch unit 32, a baseband demodulation unit 35, A D / D converter 45, a VSB demodulator 46, and an NTSC demodulator 48.

The difference between FIG. 3 and FIG. 4 of the present invention is that the switch unit 32 is replaced by a distribution unit 52.
In the embodiment of the present invention shown in FIG. 3, the configuration is adopted when distortion of the IF signal in the switch unit 32 poses a problem. That is, the switch circuit 50 is provided on the power supply line 51 to the baseband demodulation unit 35, and when the analog signal is received, the switch circuit 50 is turned off using the control voltage 31 from the second PLL circuit 29. As a result, the NTSC demodulation unit 48 by the baseband demodulation unit 35
Can be suppressed.

When an analog signal is received, a stop signal (that is, the control voltage 31 of the second PLL 29) is supplied to an operation stop terminal 56 provided in the baseband demodulation unit 35 as necessary, so that the baseband demodulation unit Can be stopped. The operation stop terminal 56 is generally
In the case of an IC-based baseband demodulation unit 35 called an enable terminal or a shutdown terminal, a part or all of the function of the baseband demodulation unit 35 is stopped or put into a standby state by supplying a stop signal. This allows the baseband demodulation unit 35 to use the NTSC demodulation unit 4
8 can be suppressed.

Further, in FIG. 4, reference numeral 10 denotes a housing;
Is a first converter, 13 is a second converter, 14 is a signal input terminal, 15 is an RF amplifier, 16 is a first mixer, 17 is a bandpass filter, 18 is a first IF amplifier, and 19 is a bandpass. Filter, 20 is the first PLL
Control data, 21 is an input terminal of the first PLL control data,
22 is a first PLL circuit, 23 is a first local oscillator, 24 is a second mixer, 25 is a second IF amplifier, 26
Is a band-pass filter, 27 is a second PLL control data, 28 is an input terminal of the second PLL control data, 29 is a second PLL circuit, 30 is a second local oscillator, and 31 is 2nd
The control voltage of the PLL 29, 33 is a terminal, 34 is a terminal, 36
Is a band pass filter (BPF), 37 is a digital IF amplifier, 38 is an I signal demodulation mixer,
39 is a mixer for Q signal demodulation (mixer), 40 is a 90 degree phase shifter, 41 is a local oscillator for baseband, 42
Is a mixer for phase comparison, 43 is an I signal output terminal, 44 is an IF output terminal, and 56 is an operation stop terminal.

It should be noted that the present invention is naturally applied to a digital / analog shared tuner of a single conversion type in the same manner. The single conversion method refers to, for example, in FIG.
Means a single frequency conversion unit, and the frequency conversion unit 2 includes only a first conversion unit without a second conversion unit. The frequency used is, for example, 4
5.75 MHz or the like.

[0062]

As described above, according to the digital / analog shared tuner according to the first aspect of the present invention, the signal input terminal, the frequency converter for converting the input signal to the IF signal, and the type of the received signal (analog / analog). Switching distribution unit 55 for switching or distributing the transmission destination of the IF signal by digital)
A signal input terminal, a frequency conversion unit, and a switching distribution unit, each of which includes a baseband demodulation unit for baseband demodulating the signal into an I signal, an output terminal for the I signal, and an output terminal for the IF signal; , A baseband demodulation unit, an I signal output terminal, and an IF signal output terminal are housed in a single casing that acts as an electromagnetic seal, and are switched by a control signal from a component in the casing. The operation of the distribution unit or the operation of the baseband demodulation unit is controlled. Therefore, the baseband demodulation unit is not affected by the noise generated in the digital processing system at the subsequent stage, and the accuracy of the local oscillation frequency of the local oscillator of the baseband demodulation unit can be increased. The generated unnecessary radiation can be suppressed, and an adverse effect at the time of NTSC demodulation due to the operation of the baseband demodulation unit at the time of analog broadcast reception can be eliminated.

Further, according to the second aspect of the present invention,
The analog shared tuner is characterized in that the switching distribution unit is constituted by a switching unit. By using the switching unit 32 as the switching distribution unit 55, the switching separation of the IF signal is completely performed. Will be

Further, according to the third aspect of the present invention,
The analog shared tuner uses a control voltage of a PLL circuit of the frequency conversion unit for a control signal by a component in the housing for controlling the operation of the switching distribution unit or the operation of the baseband demodulation unit. It is characterized by the following. Therefore, the baseband demodulation unit is not affected by noise generated in the digital processing system at the subsequent stage, and the accuracy of the local oscillation frequency of the local oscillator of the baseband demodulation unit can be improved.

Further, the digital communication device according to claim 4 of the present invention.
The analog shared tuner is characterized in that, when receiving an analog signal, the operation of the baseband demodulation unit is stopped by stopping at least a part of power supply to the baseband demodulation unit. Unwanted radiation generated from the band demodulation unit can be suppressed, and an adverse effect at the time of NTSC demodulation due to the operation of the baseband demodulation unit during analog broadcast reception can be eliminated.

Further, according to claim 5 of the present invention,
The analog shared tuner is characterized in that when an analog signal is received, the operation of the baseband demodulator is stopped by supplying a stop signal to an operation stop terminal of the baseband demodulator. Therefore, part or all of the functions of the baseband demodulation unit 35 are stopped or in a standby state, and the NTSC demodulation unit 48
Can be suppressed. Thus, it is possible to prevent the baseband demodulation unit 35 from interfering with the NTSC demodulation unit 48.

Further, according to the sixth aspect of the present invention, the digital
The analog shared tuner is characterized in that the switching distributor is configured by a distributor. Therefore, the configuration is particularly effective when distortion of the IF signal in the switch unit 31 causes a problem.

Further, the digital communication device according to claim 7 of the present invention.
The analog shared tuner is characterized in that, when receiving an analog signal, stopping the operation of the baseband demodulation is performed by stopping at least a part of power supply to the baseband demodulation unit. Unwanted radiation generated from the demodulation unit can be suppressed, and an adverse effect on NTSC demodulation due to operation of the baseband demodulation unit during analog broadcast reception can be eliminated.

Further, in the digital / analog shared tuner according to claim 8 of the present invention, when an analog signal is received, the operation of the baseband demodulator is stopped by sending a stop signal to the operation stop terminal of the baseband demodulator. It is characterized by performing by supply. Therefore, part or all of the function of the baseband demodulation unit 35 is stopped or put into a standby state, and the NTSC demodulation unit 4
8 can be suppressed. Thus, it is possible to prevent the baseband demodulation unit 35 from interfering with the NTSC demodulation unit 48.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a digital / analog shared front-end system including a digital / analog shared tuner circuit according to an embodiment of the present invention;
FIG. 9 is a diagram illustrating a switching distribution unit 55 that switches or distributes a transmission destination of an IF signal according to a type of a received signal (analog / digital).

FIG. 2 is a diagram showing another embodiment of the present invention;
FIG. 3 is a circuit block diagram illustrating a digital / analog shared front-end system including a circuit of an analog shared tuner, and includes a switch unit 32 in a switching distribution unit 55.

FIG. 3 is a digital digital camera according to another embodiment of the present invention.
FIG. 2 is a circuit block diagram illustrating a digital / analog shared front-end system including a circuit of an analog shared tuner, including a switch unit 32 in a switching distribution unit 55 and a switch unit 50 to a baseband demodulation unit.

FIG. 4 is a digital digital camera according to another embodiment of the present invention.
FIG. 2 is a circuit block diagram illustrating a digital / analog shared front-end system including a circuit of an analog shared tuner, which includes a switching unit to a switching distribution unit 55 and a switch unit 50 to a baseband demodulation unit.

FIG. 5 is a circuit block diagram showing a configuration of a conventional digital / analog shared tuner front-end system.

[Explanation of symbols]

REFERENCE SIGNS LIST 10 housing 11 frequency conversion unit 12 first conversion unit 13 second conversion unit 14 signal input terminal 15 RF amplifier 16 first mixer (mixer) 17 bandpass filter 18 first IF amplifier 19 bandpass filter 20 first PLL control data 21 First PLL Control Data Input Terminal 22 First PLL Circuit 23 First Local Oscillator 24 Second Mixer 25 Second IF Amplifier 26 Bandpass Filter 27 Second PLL Control Data 28 Second PLL Control Data Input Terminal 29 Second PLL Circuit 30 2nd local oscillator 31 2nd PLL 29 control voltage 32 switch unit 33 terminal 34 terminal 35 baseband demodulation unit 36 bandpass filter (BPF) 37 digital IF amplifier 38 I signal demodulation mixer (mixer) 39 Q signal demodulation mixing vessel Mixer) 40 90-degree phase shifter 41 Local oscillator for baseband 42 Mixer for phase comparison (mixer) 43 I signal output terminal 44 IF output terminal 45 A / D converter 46 VSB demodulator 47 A / D converter 45 or later Control signal of digital processing system of 48 NTSC demodulation unit 50 switch circuit 51 power supply line 52 distribution unit 55 switching distribution unit for switching or distributing IF signal transmission destination 56 operation stop terminal

Claims (8)

[Claims] 1. A digital / analog shared tuner for receiving both digital and analog broadcasts, a signal input terminal, a frequency converter for converting an input signal into an IF signal, and an IF depending on the type of received signal (analog / digital).
A switching distribution unit for switching or distributing a signal transmission destination;
A baseband demodulation unit for baseband demodulating the IF signal into an I signal, an output terminal for the I signal, and an output terminal for the IF signal;
Frequency converter, switch distributor, baseband demodulator, I
The output terminal of the signal and the output terminal of the IF signal are housed in one housing that acts as an electromagnetic seal, and the operation of the switching distribution unit according to a control signal from a component in the housing, or A digital / analog shared tuner for controlling the operation of a baseband demodulation unit. 2. The digital / analog shared tuner according to claim 1, wherein said switching distribution unit is constituted by a switch unit. 3. The digital / analog shared tuner according to claim 2, wherein the operation of the switching distribution unit is performed.
A digital / analog shared tuner, wherein a control voltage of a PLL circuit of the frequency conversion unit is used as a control signal by a component in the housing for controlling an operation of a baseband demodulation unit. 4. The digital / analog shared tuner according to claim 3, wherein when the analog signal is received, the operation of the baseband demodulation unit is stopped and at least a part of the power supply to the baseband demodulation unit is stopped. A digital / analog shared tuner characterized by the following: 5. The digital / analog shared tuner according to claim 3, wherein when the analog signal is received, the operation of the baseband demodulation unit is stopped by supplying a stop signal to an operation stop terminal of the baseband demodulation unit. A digital / analog shared tuner characterized by the following. 6. The digital / analog shared tuner according to claim 1, wherein said switching distribution unit comprises a distribution unit. 7. The digital / analog shared tuner according to claim 6, wherein when the analog signal is received, the operation of the baseband demodulation is stopped by stopping at least a part of the power supply to the baseband demodulator. A digital / analog shared tuner characterized by performing. 8. The digital / analog shared tuner according to claim 6, wherein when the analog signal is received, the operation of the baseband demodulator is stopped by supplying a stop signal to an operation stop terminal of the baseband demodulator. A digital / analog shared tuner characterized by the following.