JPH11261913A - Digital/analog compatible receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select stably an output in response to the kind of a modulated wave of a reception signal in the case of receiving signals on analog/digital modulated waves. SOLUTION: The receiver 1000 converts a received high frequency signal into an intermediate frequency signal, and allows both an analog demodulation section 4 and a digital demodulation section 5 to apply demodulation to the intermediate frequency signal and discriminates totally a kind of a modulated wave that is transmitted and discriminated at present based on a discrimination result of an analog modulation wave discrimination circuit 400 and a digital modulation wave discrimination circuit 300. Thus, even in the case that an electric field strength of the received signal is fluctuated sometime or the like, the receiver properly discriminates whether the modulated wave of the received signal is an analog signal or a digital signal and selects automatically a proper demodulation output depending on the kind of the modulated wave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital / analog common receiving apparatus, and more particularly to a digital / analog receiving apparatus in which a video signal is mixed with an analog television modulation method or a digital modulation method by terrestrial, satellite radio or cable transmission. The present invention relates to a configuration of a digital / analog shared receiving device capable of selectively receiving a received signal.

[0002]

2. Description of the Related Art In a system for transmitting a video signal by a terrestrial wave or a cable, analog residual sideband amplitude modulation (VSB-FM modulation) has been often used. The conventional analog modulated wave receiving system is described in detail in, for example, "Color Television Textbook, Above, Below" (Japan Broadcasting Corporation).

In recent years, terrestrial and cable transmissions have been proposed in which digital video signals are encoded with high efficiency, then directly digitally modulated, and digitally transmitted with the same transmission bandwidth as conventional analog modulation. The digital transmission system has features such as being able to transmit more information and being not affected by transmission noise as compared with the analog modulation system, and is considered to be widely used in the future.

As a digital modulation method used for digital broadcasting, an orthogonal frequency division multiplexing method, an orthogonal amplitude modulation and the like are generally known.

With the recent development of digital transmission technology,
Conventionally, digital modulation can be performed even in a transmission and broadcasting system using an analog modulation method. As a result, the situation of receiving received waves in which both analog and digital modulation methods are mixed is increasing. For example, Japanese Patent Application Laid-Open No. 5-347736 discloses a receiver that can be used for both analog and digital modulated waves. FIG.
FIG. 1 is a schematic block diagram showing a configuration of a multi-method compatible receiving device disclosed in US Pat.

[0006] The receiving apparatus 7000 is a high frequency signal (hereinafter referred to as RF) in which digitally modulated waves and analog television modulated waves are mixed.
Signal, and receives an intermediate frequency signal (hereinafter, IF signal).
After the conversion, the analog modulation wave demodulator 7100 and the digital modulation wave demodulator 7200 that demodulate the respective modulation waves are provided.

[0007] Further, receiving apparatus 7000 operates according to the bit error rate of the signal from digital modulated wave demodulator 7200.
A digital modulation wave determination circuit 7300 that determines whether the input signal is a digital modulation wave is provided. The digital modulation wave determination circuit 7300 generates an identification flag indicating whether the current input signal is a digital modulation wave. If it is determined that a digital signal is being received using this identification flag, the switch 7008 is controlled to select the output of the digital decoding circuit 7201. On the other hand, if it is determined that no digital signal has been received, the switch 7008 switches to the signal processing unit 7.
It is controlled to select the output of 101.

The switch 7007 is turned on by the identification flag when a digital signal is not received. In this state, a frequency error detection circuit 7006 (hereinafter, referred to as Δf detection circuit), which is also installed in a general analog receiver, detects a frequency shift and controls the frequency of the frequency oscillator 7004. That is, a loop for stabilizing the IF signal is formed. With this configuration, an appropriate demodulation output can be selected according to the type of modulated wave of the received signal, and the operation of the frequency control loop can be automatically selected.

[0009]

However, as described above, only the signal from the digital modulation wave demodulator is used.
If it is determined whether the received signal is an analog modulated wave or a digital modulated wave, in an environment where the received electric field strength of the digital signal fluctuates, a problem may occur.

FIG. 6 is a conceptual diagram for explaining the problems of the prior art. For example, as shown in FIG. 6, when a digital signal is received in a vehicle-mounted receiver or the like, if the electric field strength is reduced, the reception is not normally performed, and the above-mentioned identification flag corresponds to "not a digital modulation wave". Output. At this time, the receiver temporarily selects and outputs the demodulated output of the analog modulated wave even while the digital signal is being received. Thereafter, when the electric field strength of the digital signal recovers, the selection of the output demodulated wave is switched again, and the operation of the receiver 7000 becomes unstable.

Note that this phenomenon can also occur when the digital modulation wave determination circuit malfunctions while receiving the analog modulation wave. That is, in the conventional technique, there is a problem in the stability with respect to the fluctuation of the intensity of the received signal in the method of determining whether the signal being received is an analog modulated wave or a digital modulated wave.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to perform a stable determination operation even when the signal strength during reception varies. It is to provide a digital / analog shared receiving device capable of performing the above.

[0013]

A digital / analog common receiving apparatus according to claim 1 is a digital / analog common receiving apparatus for receiving a high frequency signal in which a digital modulation wave and an analog television modulation wave having different modulation systems are mixed. An intermediate frequency introducing means for converting a channel-selected signal of the high-frequency signal into an intermediate frequency signal; and demodulation processing means for receiving the intermediate frequency signal and demodulating a digital modulation wave and an analog television modulation wave, respectively. The demodulation processing means includes a judgment means for judging which of the digital modulation wave and the analog television modulation wave is being transmitted by using the signal obtained by demodulating the digital modulation wave and the signal obtained by demodulating the analog television modulation wave, Control means for selecting and outputting a demodulated output according to the modulation scheme of the received signal based on the determination result of It provided La.

According to a second aspect of the present invention, there is provided a digital / analog dual-use receiving apparatus according to the first aspect of the present invention, wherein the first reception identifying means detects whether the reception state of the digital modulation wave is good or bad. Second reception identification means for detecting whether or not the reception state of the analog television modulated wave is good or bad; first reception identification means and second reception identification means.
When the reception identifying means of the present embodiment identifies that the reception state of the modulated wave currently determined to be transmitted is defective, and determines that the reception state of the other modulated wave signal is good, Comprehensive identification means for a received signal for updating the result.

A digital / analog common receiving apparatus according to a third aspect of the present invention is the digital / analog common receiving apparatus according to the second aspect, wherein:
The reception state is determined using information indicating a transmission error state obtained when decoding the transmission path coded data of the digital signal.

According to a fourth aspect of the present invention, there is provided a digital / analog common use receiving apparatus according to the second aspect, wherein the second reception identifying means comprises:
The reception state is determined using information of the horizontal synchronization circuit signal included in the analog television modulation wave.

According to a fifth aspect of the present invention, in the configuration of the first aspect of the present invention, the intermediate frequency introducing means outputs in response to a frequency variation of the input high frequency signal. Frequency stabilizing means for stabilizing the intermediate frequency signal, and means for operating the frequency stabilizing means at the time of receiving the analog television modulated wave according to the determination result of the determining means.

[0018]

FIG. 1 is a schematic block diagram showing the structure of an analog / digital shared receiving apparatus 1000 according to an embodiment of the present invention.

Referring to FIG. 1, an analog / digital shared receiving apparatus 1000 has an input terminal 1 for receiving an RF signal in which an analog television modulated wave and a digital modulated wave are mixed.
A high-frequency amplifier 2 for amplifying an RF signal, an intermediate frequency introducing unit 3 for receiving an output of the high-frequency amplifier 2 and converting it to an IF signal, and receiving an IF signal output from the intermediate frequency introducing unit 3 for analog demodulation. An analog demodulation processing unit 4 that performs processing, supplies a demodulated output to one of input nodes of an output selection switch 7, and outputs a determination signal indicating a reception state of an analog modulated wave with respect to a signal being received;
A digital demodulation process for receiving a signal, performing a digital demodulation process, supplying the demodulated output to the other input node of the output selection switch 7, and outputting a determination signal indicating the reception state of the digital modulation wave with respect to the signal being received. A total determination circuit 6 for determining whether the received signal is an analog modulated wave or a digital modulated wave using the determination signals from the analog demodulation processing unit 4 and the digital demodulation processing unit 5; And an output selection switch 7 for supplying an appropriate output according to the type of the received signal to the output terminal in accordance with the result of the determination in 6.

The intermediate frequency introducing section 3 is a tuner amplifying section 10 for converting and amplifying the amplified RF signal into an IF signal.
And an intermediate frequency stabilization circuit 11 that operates according to the type of the received signal based on the determination result of the comprehensive determination circuit 6.

FIG. 2 is a schematic block diagram showing the configuration of the analog / digital shared receiving apparatus 1000 in more detail.

As described above, the received RF signal in which the analog television modulated wave and the digital modulated wave are mixed is input to the input terminal 1 and amplified in the high frequency amplifier 2.

The tuner amplifying section 10 receives the output of the high-frequency amplifying section 2 and selects a channel using an oscillation signal from a local oscillator 22, and an automatic tuner 21 for controlling the gain of the IF signal output from the tuner 21. A gain control amplifier (hereinafter, referred to as an AGC amplifier) 23.

The intermediate frequency stabilizing circuit 11 includes a local oscillator 22 for generating an oscillation signal used for channel selection.
Receiving the output of the AGC amplifier 23, detecting a frequency shift, and outputting a frequency control signal to the local oscillator 22.
An f-detection circuit 24 and a switch 25 controlled by the comprehensive judgment circuit 6 to start or stop supplying a frequency control signal to the local oscillator 22 are provided.

That is, the local oscillator 2
2 is supplied with a frequency control signal, a frequency stabilization loop of the IF signal output from the tuner is formed.

The analog demodulation unit 4 includes an AGC amplifier 2
3, an analog modulated wave demodulator 100 for demodulating an analog modulated wave in response to the output of the switch 3, and a switch 7 for processing the demodulated signal.
And a signal processing unit 101 that supplies the signal to one of the input nodes of the analog modulation wave, and an analog modulation wave determination circuit 400 that checks the output signal of the analog modulation wave demodulator 100 and determines whether the reception state of the analog modulation wave is good or bad.

The digital demodulation unit 5 receives the output of the AGC amplifier 23 and demodulates the digital modulation wave. The digital demodulation unit 5 decodes the demodulated signal and supplies the demodulated signal to the other input node of the switch 7. Circuit 201 and a digital modulation wave determination circuit 300 that checks the output signal of the digital modulation wave demodulator 200 and determines whether the reception state of the digital modulation wave is good or bad.

The comprehensive judgment circuit 6 receives the judgment results of the analog modulation wave judgment circuit 400 and the digital modulation wave judgment circuit 300, and the reception state of the modulation wave judged as being received changes from good to bad. In this case, when the reception state of the other modulated wave is good, the determination result is updated to determine whether the currently received signal is an analog modulated wave or a digital modulated wave.

The operation of the switches 7 and 25 is controlled by the output of the comprehensive judgment circuit 6. That is, if the overall judgment circuit 6 judges that the digital modulated wave is being received, the switch 7 is controlled to select the output of the digital decoding circuit 201 and the switch 25 is turned off. If it is determined that the analog modulated wave is being received, the switch 7 is controlled to select the output of the signal processing unit 101 and the switch 25 is controlled to the on state.

With the above configuration, in the present invention, even if the signal strength of the modulated wave being received fluctuates, the type of the modulated wave is stably determined, and an appropriate demodulator output is selected based on the determination. be able to.

Further, in the present invention, by operating or stopping the IF signal frequency stabilization loop based on the above determination, it is possible to automatically stabilize the frequency of the IF signal at the time of receiving the analog television modulated wave.

FIG. 3 is a schematic block diagram showing the configuration of the digital modulation wave judgment circuit 300. Referring to FIG. 3, determination circuit 300 includes an input terminal 311 for receiving an output of digital modulated wave demodulator 200, a syndrome calculation circuit 313 for receiving an input to input terminal 311 and obtaining an error pattern in a block code, and a syndrome calculation circuit 313. Circuit 313
And a continuity detection circuit 315 that receives the result of the error number determination circuit 314 as an input. That is, the determination circuit 300 determines whether the input signal is a digital signal and determines whether the reception state of the digital modulation wave is good or bad by utilizing the characteristics of the transmission path coding in digital data transmission, that is, the property of error correction coding. Make a decision.

Next, the operation will be briefly described. The input terminal 311 is supplied with a demodulated output from the digital modulation wave demodulator 200. The signal from the input terminal 311 is input to the syndrome calculation circuit 313.

The syndrome calculation circuit 313 calculates an error pattern (syndrome) in the block code, and is composed of, for example, a binary code division circuit.
The position of the error bit can be detected from the syndrome obtained by this circuit. That is, error correction is possible. However, it is sufficient here to detect the number of errors.

The error number determination circuit 314 is a circuit for detecting the number of errors by using the syndrome as an input. For example, a ROM having the number of output bits corresponding to the number of bits of the syndrome is used.
Is realized. Check data for error correction and the like is added to the digital data transmission. If a digital modulation wave for which the specified transmission path decoding is performed is input and the reception is normal, the number of errors may be reduced. The number of errors detected by the decision circuit 314 is relatively small.

However, when an analog modulated wave is input, this transmission line decoding operation is completely meaningless, so that the number of errors detected by the error number determination circuit 314 is extremely large. Become.

The error number determination circuit 314 determines that the input signal is not a digitally modulated wave when a large number of errors are continuously detected in order to allow an actual transmission error to some extent. The output of the error number determination circuit 314 is
It is input to the continuity detection circuit 315. When the state where the number of errors is large continues, a digital identification flag indicating that the digital modulation wave is not being received is obtained from the output terminal 316.

The continuity detecting circuit 315 can be realized by, for example, a simple counter circuit. In the above description, it is assumed that the input signal is block-coded. However, a non-block-coded signal such as convolution can be similarly applied.

FIG. 4 is a schematic block diagram showing the configuration of the analog modulated wave determination circuit 400. Referring to FIG. 4, determination circuit 400 includes an input terminal 411 to which an output from analog modulated wave demodulator 100, that is, a television signal is input, and a horizontal synchronization signal that receives a television signal and separates and outputs a horizontal synchronization signal. A separating circuit 412, a voltage controlled oscillator 415 for generating a signal synchronized with the horizontal synchronizing signal, and a multiplier 41 for multiplying the horizontal synchronizing signal by an output from the voltage controlled oscillator 415
4, a multiplier 413 that multiplies the horizontal synchronizing signal by a signal that is 90 ° out of phase from the signal of the voltage controlled oscillator 415 input to the multiplier 414, and a voltage controlled oscillator 415 that receives the output of the multiplier 414 and outputs Loop filter 4 to supply to
17 and the output of the multiplier 413 to compare the output
A low-pass filter 416 for output to the output terminal 18;
And a comparison circuit 418 for outputting the result to the output circuit 19.

The analog modulated wave determination circuit 400 determines whether or not an input signal is an analog signal by determining whether or not a horizontal synchronizing signal added to the analog television signal and serving as a timing reference for image reproduction is received on the receiving side. And a circuit for determining whether or not the reception state of the analog television modulated wave is good or bad.

Next, the operation will be briefly described. The input terminal 411 is supplied with a demodulated output from the analog modulated wave demodulator 100, that is, a television signal. Input terminal 4
The signal 11 is input to the horizontal synchronization signal separation circuit 412. The horizontal synchronization signal separation circuit 412 separates a horizontal synchronization signal from a television signal. The horizontal synchronizing signal separation circuit is described in detail, for example, in "Color Television Textbook, Above, Below" (Japan Broadcasting Corporation).

The horizontal synchronization signal separated by the horizontal synchronization signal separation circuit 412 is input to two multipliers 413 and 414.

The voltage controlled oscillator 415 generates two signals synchronized with the horizontal synchronizing signal as described later. The voltage controlled oscillator 415 has a horizontal synchronization frequency of 15.7.
The signal is set so as to output a signal in the vicinity of 34 KHz, and the output of the multiplier 414 passes through the loop filter 417 and forms a PLL loop in which the output is fed back as a frequency signal of the voltage controlled oscillator 415.

By the operation of the PLL loop, the output of the voltage controlled oscillator 415 is locked to the phase of the horizontal synchronizing signal of the input signal.

The multiplier 414 receives the horizontal synchronizing signal and the output of the voltage controlled oscillator 415. On the other hand, the horizontal synchronizing signal and a signal which is the output of the voltage controlled oscillator 415 and which is 90 ° out of phase with the output to the multiplier 414 are input to the multiplier 413.

When the output of the voltage controlled oscillator 415 is locked to the horizontal synchronization signal, the phase of the output of the voltage controlled oscillator 415 input to the multiplier 413 is shifted from the output to the multiplier 414 by 90 °. , The DC component of the output of the multiplier 413 becomes “H” level or “L” level. The output signal of the multiplier 413 is applied to the low-pass filter 4.
By integrating at 16, an "H" level or "L" level signal is obtained.

It should be noted that the voltage controlled oscillator 415 when the output of the voltage controlled oscillator 415 is locked to the horizontal synchronizing signal
To select the output of “H” level or “L” level can be arbitrarily determined in advance by the circuit design of the voltage controlled oscillator 415.

On the other hand, when the output of the voltage controlled oscillator 415 is not locked to the horizontal synchronizing signal, the outputs of the multipliers 413 and 414 are both noise-like signals that randomly swing up and down about the midpoint potential. Become. in this case,
When the output signal of the multiplier 413 is integrated by the low-pass filter 416, a signal having a substantially midpoint potential is obtained.

The comparison circuit 418 includes a low-pass filter 41
The DC voltage which is the output of No. 6 is compared with a reference value previously set to an appropriate value between the "H" level or "L" level and the intermediate potential. With this operation, the comparison circuit 418 can determine whether or not the PLL loop has locked to the horizontal synchronization signal. Based on this determination, an analog identification flag indicating that the signal being received is an analog modulated wave is output to output terminal 419 when locked to the horizontal synchronization signal.

In the configuration described above, the horizontal synchronizing signal separating circuit 412 is included independently in the analog modulated wave determination circuit 400 receiving the output of the analog modulated wave demodulator 100, but is included in the signal processing unit 101. The horizontal synchronizing signal separating circuit may be shared by the signal processing unit 101 and the analog modulation wave circuit 400.

FIG. 5 is a diagram showing an embodiment of the comprehensive judgment circuit 6. Referring to FIG. 5, comprehensive judgment circuit 6 has a terminal 50 for inputting an output signal of analog modulated wave judgment circuit 400.
1, a terminal 502 for inputting an output signal of the digital modulation wave determination circuit 300, a flip-flop 503 having the input terminals 501 and 502 as inputs, and an output terminal 506 for outputting the result of the flip-flop 503.

The comprehensive judgment circuit 6 is a circuit for outputting a total judgment result on whether the received signal is a digital modulation wave or an analog television modulation wave based on two input signals. Next, the operation will be briefly described.

The two input signals supplied to the input terminals 501 and 502 are an analog identification flag and a digital identification flag which are binary signals as described above.

In this configuration, the RS flip-flop 503 has two-input NAND circuits 504 and 505. For example, when a normal digital modulated wave signal is received, the digital identification flag is set to "
In this case, the H level and the analog identification flag are set to “L.” In this case, since the “H” level signal is supplied to the input terminal 502 and the “L” level signal is supplied to the input terminal 501, the output of the RS flip-flop 503 is output. The signal, that is, the comprehensive judgment result becomes “H.” From this state, if the reception electric field strength decreases and the reception state of the digital modulation wave becomes poor, the digital modulation wave is received even though it is being received. Digital identification flag is changed from "H" level
Switch to L "level.

However, the output of the RS flip-flop is such that the value of the signal input to the other input terminal 501 is "H".
Since the previous state is maintained as long as the level does not reach the level, the overall judgment result remains at the “H” level, and the analog / digital changeover switch 7 also maintains the state fixed to the digital side.

Here, when the received electric field strength is restored again and normal digital modulated waves can be received,
The digital identification flag, that is, the value of the signal input to the input terminal 502 becomes "H" level again, and a normal reception state is set.

If the analog TV modulated wave determination circuit 400 malfunctions while receiving the digital modulated wave, the inputs to the input terminals 501 and 502 are both "".
Although the input level is set to “H” level, the input that has been set to “H” level earlier in time is given priority as a characteristic of the RS flip-flop.
While the signal inputted to the output terminal 50 is at the “H” level.
Since the comprehensive judgment result of No. 6 is not affected by the analog identification flag, that is, the value input to the input terminal 501, there is no problem in reception.

Conversely, the same effect can be obtained when the receiving condition of the analog TV modulated wave is deteriorated while the analog TV modulated wave is being received and when the digital modulated wave determining circuit 300 malfunctions.

With the above configuration, according to the present invention, even when the signal intensity of the modulated wave being received fluctuates and when the digital modulated wave determination circuit 300 or the analog modulated wave determination circuit 400 malfunctions, the modulated wave being received is not affected. The type can be determined stably, and the operation or stop of the automatic IF signal frequency stabilization loop based on this can be performed, and an appropriate demodulator output can be selected.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0061]

The digital / analog common use receiving apparatus according to the present invention uses the judgment result of the analog modulation wave reception state judgment circuit and the digital modulation wave reception state judgment circuit for the signal being received. Since the type of modulation wave of the signal being received is comprehensively determined, it is possible to more reliably determine whether the signal being received is analog or digital, and select a demodulation output according to the modulation method of the received signal. it can.

A digital / analog dual-use receiving apparatus according to the present invention comprises: a determination circuit for determining whether a reception state of an analog television modulated wave is good or bad with respect to a signal being received; By using both the determination results of the determination circuit as to whether the reception state is good or bad,
When the reception state of the modulated wave determined to be currently transmitted is determined to be bad, and when the reception state of the other modulated wave signal is determined to be good, the comprehensive determination result is determined. Since the update is performed, even when the electric field strength of the received signal fluctuates with time or when one of the determination circuits malfunctions, it is appropriately determined whether the modulated wave of the signal being received is analog or digital. be able to.

A digital / analog dual-use receiving apparatus according to the present invention comprises: a determination circuit for determining whether the reception state of an analog television modulated wave is good or bad with respect to a signal being received; By using both the determination results of the determination circuit as to whether the reception state is good or bad,
Since the type of modulation wave of the signal being received is comprehensively determined, it is more reliable to determine whether the signal being received is analog or digital, and the frequency stabilization loop of the intermediate frequency signal is set when the analog TV modulation wave is received. Can be operated automatically.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram illustrating a configuration of an analog / digital shared receiving apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram showing the configuration of an analog / digital shared receiving apparatus 1000 according to an embodiment of the present invention in detail.

FIG. 3 is a schematic block diagram illustrating a configuration of a digital modulation wave determination circuit 300.

FIG. 4 is a schematic block diagram illustrating a configuration of an analog modulated wave determination circuit 400.

FIG. 5 is a schematic block diagram showing a configuration of a comprehensive judgment circuit 6.

FIG. 6 is a conceptual diagram for explaining a problem of the related art.

FIG. 7 is a schematic block diagram showing a configuration of a conventional multi-mode receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input terminal 2 High frequency amplification part 3 Intermediate frequency introduction part 4 Analog demodulation processing part 5 Digital demodulation processing part 6 General judgment circuit 7 Output selection switch 8 Output terminal 10 Tuner amplification part 11 Intermediate frequency stabilization circuit 21 Tuner 22 Local oscillator 23 AGC Amplifier 24 Δf detection circuit 25 Operation selection switch 100 Analog modulation wave demodulator 101 Signal processing unit 200 Digital modulation wave demodulator 201 Digital decoding circuit 300 Digital modulation wave judgment circuit 400 Analog modulation wave judgment circuit

Claims (5)

[Claims] 1. A digital / analog shared receiving apparatus for receiving a high-frequency signal in which a digital modulation wave and an analog television modulation wave having different modulation schemes are mixed, wherein a channel-selected signal of the high-frequency signal is an intermediate frequency signal. Intermediate frequency introducing means for converting the signal into an intermediate frequency signal, demodulation processing means for receiving the intermediate frequency signal and demodulating a digital modulation wave and an analog television modulation wave, respectively, the demodulation processing means Using a signal obtained by demodulating the analog television modulation wave, the digital television receiver includes a determination unit that determines which of the digital modulation wave and the analog television modulation wave is being transmitted. A digital / analog shared reception device further comprising control means for selecting and outputting a demodulation output according to the Apparatus. 2. The method according to claim 1, wherein the determining unit detects a good or bad reception state of the digital modulated wave, and a second reception unit detects good or bad reception state of the analog modulated wave. When the reception state of the modulated wave determined to be currently transmitted is determined to be bad by the first reception identification means and the second reception identification means, the other modulated wave signal 2. The digital / analog shared receiving apparatus according to claim 1, further comprising: means for comprehensively identifying a received signal for updating the determination result when it is determined that the receiving condition is good. 3. The reception state determination unit according to claim 2, wherein the first reception identification unit determines the reception state using information indicating a transmission error state obtained when decoding the transmission path coded data of the digital signal. Digital / analog receiving device. 4. The digital / analog common receiving apparatus according to claim 2, wherein said second reception identifying means determines the reception state using information of a horizontal synchronization signal included in the analog television modulated wave. 5. An intermediate frequency introducing unit, comprising: a frequency stabilizing unit for stabilizing an intermediate frequency signal to be output with respect to a frequency variation of an input high frequency signal; 2. The digital / analog shared receiving apparatus according to claim 1, further comprising means for causing the stabilizing means to operate when receiving an analog television modulated wave.