JPH01174033A - Fm multiplex data broadcast receiver - Google Patents

Abstract

PURPOSE:To receive a multiplex data signal without any error by correcting a signal being the result of Hilbert transformation of the 2nd harmonic of a received stereo difference signal at a level of an interference wave included in a multiplex data, and cancelling the interference between both carrier signals of the stereo difference signal and the multiplex data signal. CONSTITUTION:A band pass filter 103 extracts a stereo difference signal 2 from a base band signal of an input signal 101. Its output signal 115 is correspondent to the stereo difference signal 2. The signal 115 is supplied to a square circuit 116, where it goes to a 2nd harmonic wave and outputted as an amplitude modulation wave 117 of 100% modulation in 76kHz to a Hilbert transforming circuit 119, where the signal is transformed into a signal having a phase in matching with the negative direction of the I axis. A calculating circuit 127 forms interference wave elimination signal 128 from the signals. A multiplex data signal 114 including an interference wave is subject to an interference wave elimination signal 128 at an adder circuit 129 and a multiplex data signal 130 from which an interference wave is eliminated is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an FM multiplex data broadcasting receiver, and particularly to interference caused by harmonics of a differential channel signal caused by distortion in an FM broadcast wave transmission path. It is designed to remove signals.

[Summary of the Invention] The present invention provides a method for eliminating multipath interference caused by harmonics of stereo signals that occurs when receiving FM multiplex data broadcasting at a location with multipaths (multiple reflection paths). In order to reduce the noise, the second harmonic of the received stereo difference signal and the Hilbert-transformed signal of the second harmonic are corrected by the level of the interference contained in the multiplexed data signal, and the corrected signal is used. By canceling interference between the stereo difference signal and the recarried signal of the multiplexed data signal, the multiplexed data signal can be received without error.

[Prior Art] Previously, research has been conducted to remove interference caused by distortion in the transmission path of FM broadcast waves at the intermediate frequency stage of a receiver (for example, a method for automatically canceling multipath distortion in Date GenrFM broadcasts). ” (November 30, 1982) Technical Report TEBS59-1 of the Television Society of Japan; Takashi Mochizuki “A method of automatic removal of FM multipath distortion using an adaptive digital filter J (
1986.3) Television Society Journal Vol.

39, No. 3).

[Problems to be Solved by the Invention] However, as mentioned above, in the conventional technology, research is underway to remove multipath interference in the intermediate frequency stage of a receiver, and this method requires calculations for interference removal. Since the amount of data is large and the signal frequency of the intermediate frequency stage is a high frequency of IMHz or more, it is difficult to process it in real time, and it has not been put to practical use yet.

Therefore, an object of the present invention is to use a low-frequency baseband signal after FM demodulation, and from the correlation between the interference waves contained in the FM multiplex data channel and the stereo signal, to relatively easily perform interference processing in real time. An object of the present invention is to provide an FM multiplex data broadcasting receiver that can remove waves.

[Means for Solving the Problems] In order to achieve such an object, the present invention generates the second harmonic from the received stereo difference channel signal and demodulates the multiplexed data signal including the interference wave. The multipath interference level is detected from the average value over a predetermined period of time and the average value over a predetermined period after demodulating the second harmonic, and a interference cancellation signal is formed from them and subtracted from the multiplex data signal. .

That is, the present invention provides a stereo sum channel signal, a pilot signal, a stereo difference channel signal obtained by suppressing carrier amplitude modulation of the first subcarrier, and a QPS of the second subcarrier.
K-modulated multiplex data channel signals and FM
a first extraction means for receiving a modulated and transmitted FM broadcast radio wave, FM demodulating the received radio wave to extract an FM demodulated signal; and extracting a stereo difference channel signal subjected to suppressed carrier amplitude modulation from the FM demodulated signal. a first extraction means;
a second extraction means for extracting a QPSK modulated multiple data channel signal from the M demodulated signal; and a generation means for generating a second harmonic of the suppressed carrier amplitude modulated stereo difference channel signal extracted from the first extraction means. , an integral converting means for integrally converting the second harmonic from the generating means;
Detection means for QPSK demodulating the QPSK-modulated multiple data channel signal extracted from the extraction means using a second subcarrier, and detecting the level of the interference wave by averaging the demodulated baseband data channel signal over a predetermined period. a second extraction means for synchronously detecting the second harmonic from the generation means with a second subcarrier and taking out an average value obtained by averaging the synchronously detected baseband stereo difference channel signal over a predetermined period; and a generation means. Level correction is performed on the second harmonic from the output from the integral conversion means and the output from the integral conversion means based on the interference level detected by the detection means and the average value taken out from the second extraction means to form an interference wave removal signal. and means for removing the interference wave by subtracting the interference wave cancellation signal from the formation means from the multiple data channel signal to the QPS extracted from the second extraction means. .

[Function] According to the present invention, it is possible to receive an FM multiplex data broadcast, extract a stereo difference channel signal from the demodulated baseband, and generate a second harmonic. It is also possible to extract the multiplexed data signal containing interference waves, demodulate it, and detect the level of interference waves due to multipath from the average value averaged over a predetermined period, and detect the second harmonic of the stereo difference signal. Using the average value demodulated and similarly averaged over a predetermined period, the interference can be removed by subtracting the interference removal signal formed in accordance with the interference wave level from the multiplexed data signal containing the interference wave.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

In explaining the present invention in detail, first, the F~1 multiplex data broadcast system and interference caused by distortion in the transmission path, such as multipath interference, will be explained.

FIG. 5 is a layout diagram showing an example of the baseband spectrum of the FM multiplex data system.

In FIG. 5, 1 is a stereo sum signal.

2 is a stereo difference signal, which is subjected to suppressed carrier wave amplitude modulation with subcarrier toss of 38 kHz. 3 is 19k
11z pilot signal. 4 is a multiplex data signal, which is a digital signal modulated into QPS.

Its second subcarrier frequency is 76 k II z. The bit rate of multiplex data signal 4 is 48kb/s
It is. 38kHz subcarrier and 76kHz
The second subcarrier of z is the frequency 1 of the pilot signal 3
The frequencies are 2 times and 4 times 9 kHz, respectively. The phase of the first subcarrier and the I-axis (described later) phase of the second subcarrier match the phase of the pilot signal 3.

FIG. 2 is a layout diagram showing an example of a baseband signal spectrum when an FM broadcast wave including an FM multiplexed data signal is received at a receiving point with a multipath and FM demodulated.

In FIG. 2, the same parts as in FIG. 5 are given the same reference numerals. As a stereo signal, only the stereo difference signal 2, which has a large interference effect on the multiplexed data signal, is shown, and
This shows the spectrum in a multipath state that generates second harmonics where the interference level to the multiplexed data signal 4 is greatest, that is, when the phase difference between the main carrier waves of the direct wave and the reflected wave is around 90°. Ta. Also, for convenience of explanation, it is assumed here that the angular frequency of the stereo difference signal 2 is Ω8 and its level is V. 201 is the lower sideband wave of the stereo difference signal, its angular frequency is 2Ω, -Ω5, and the level is V/2. Here, Ω2 is the angular frequency of the pilot signal 3. 202 is a stereo difference ε upper sideband wave whose angular frequency is 2Ω2+Ω5 and the level is V/2. 203,2
04 and 205 are interference waves generated by multipath, and 203 and 205 are second harmonic components of the upper and lower sideband signals 201 and 202 of the stereo difference signal, respectively. The angular frequency of the interference wave 204 is 4Ω2) The level is AV
2) The angular frequency of the interference wave 203 is 4ΩP-2Ω8, the level is 8V2/2) The angular frequency of the interference wave 205 is 4Ω1+2Ω
5. The level is AV2/2. Here, the coefficient A is a coefficient for second high frequency generation determined by the thickness of the multipath, the delay time, and the phase difference between the main carrier waves, that is, the reception state.

While the stereo difference signal sidebands 201 and 202 are suppressed carrier amplitude modulated waves, the interference (1
1203, 204 and 205 are amplitude modulated waves with a modulation depth of 100%, the average level of which is AV2, and varies sinusoidally between the maximum level 2AV2 and the minimum level at an angular frequency of 2Ω5.

In order to demodulate the multiplexed data signal, the multiplexed data signal 4 shown in Fig. 5 is extracted and demodulated using a bandpass filter, but since the interference waves 203, 204 and 205 are in the same band, these interference waves are directly detected. receive. Particularly, when the second harmonic generation coefficient A and the level of the stereo difference signal 2 are both large, interference occurs to the extent that the multiplexed data signal 4 cannot be demodulated.

Next, the above relationship will be explained using mathematical expressions.

According to Carlson's theory (FM Radio Engineering 2, Nikkan Kogyo Shimbun, edited by Kan Atsushi), - numerically, the characteristic U (Δ
Ω) has a linear distortion, and U(ΔΩ) becomes U(ΔΩ)−1+
αI(ΔΩ)+α2(ΔΩ)2+α, (ΔΩ)3+...
・+j(βl(ΔΩ) 1β2(ΔΩ)2+β3(ΔΩ)
3+ β4 (ΔΩ) 4+ ...), and if the modulation signal of the FM wave is μ(1), the distortion Ωd(1) generated in this transmission path is the coefficient α of the series.
, β and μ(1), it can be calculated as follows.

Now, if the stereo difference signal is VCOS (Ω5), the modulation signal μ(1) is as follows. Here VP is the level of the pilot signal,
The first term of μ(1) indicates the pilot signal, and the second and third terms indicate the upper and lower bands of the stereo difference channel, respectively.

On the other hand, when there is multipath, the characteristics of the FM wave transmission path are that there is only one reflected wave, and the phase difference between the direct wave and the reflected wave is 90
degree, U(ΔΩ)-1-"sin (rΔΩ)-jr' c
It can be approximated by os(rΔΩ). Here, r is the level ratio of the reflected wave and the direct wave, and τ is the delay time of the reflected wave. This U (
ΔΩ) becomes by series expansion. From this μ(1) and U(ΔΩ), the above Ωd
From the equation (t), the distortion generated by multipath is as follows.

By actually substituting the value of μ(1) and calculating, the distortion falling in the band centered at 76 Hz of the multiplex data channel is calculated by 4.
By finding the next term, x V' (1+c
os2Ω, Ht) cos (4ΩPt). 1st
If we set [] of the term to B and [] of the second term to C, we get Ωd (t) −BV' (1+cos 2Ω5t)s
in(4Ωpt)”(:V2(1+cos 2Ωs
t) denoted as CO5 (4Ωpt). If the first term is an AM wave that is in phase with the pilot phase, and the second term is an AM wave that is 90 degrees ahead of phase, then Ωd (t) = Av2 (1 + cos2Ω5t)si
n(4Ω, 1-θ). That is, the distortion that falls on 76k)Iz is IOQ% with a carrier frequency of 76kHz.
It is a modulated AM wave, and its carrier level is 2 of the difference signal level ■
The proportional coefficient A and phase θ are determined by the level, phase difference, and delay time of the reflected wave. The phase θ indicates the deviation from the phase of the pilot signal.

The above stereo signal was calculated as a single sine wave, but
- Numerically, it is a combination of multiple sine waves, and the distortion that occurs in this case is a suppressed carrier AM modulated wave component with a frequency equal to the sum of each sine wave component, in addition to the 100% modulated AM wave as described above. Although this component also occurs, it does not affect the spirit of the present invention, and this component can also be removed at the same time.

Furthermore, if the phase of the reflected wave is other than 90 degrees, the coefficients α and β of the series expansion of the transmission characteristics will have different values, and as a result, A
Although the values of and θ change, the form of the distortion equation of Ω and (t) does not change at all.

Next, the phase and level relationship between signals and interference waves involved in the demodulation of multiplexed data signals will be explained.

Figure 3 shows the vector (phase and level) when demodulating a QPSK-modulated multiplex data signal when there is no interference wave.
It is an explanatory diagram showing an example of.

In FIG. 3, 301 is a reference axis that matches the phase of the pilot signal and is referred to as one axis. 302 is an axis orthogonal to the I axis and is referred to as the Q axis. 303.304.305 and 30
6 indicates a vector of a multiplexed data signal modulated into QPS, which has phases of 45 degrees, 135 degrees, 225 degrees, and 315 degrees from the ■ axis, respectively. As the symbols of the multiplexed data signal to be transmitted flow, one of the four phase vectors described above is sequentially selected and transmitted according to a certain rule. In order to reproduce the code flow of the transmitted multiplex data signal, the receiver must detect which of the four vectors has been sent sequentially. This determination is made by detecting the lengths of perpendicular lines drawn to the I-axis and Q-axis, that is, the points at I-axis demodulation levels 307 and 308 and the points at Q-axis demodulation levels 309 and 310.

FIG. 4 is an explanatory diagram showing an example of a vector when the multiplexed data signal is demodulated when the interference waves 203 to 205 shown in FIG. 2 are added.

In Fig. 4, the vector of the interference wave is 401 from the origin 401.
Length up to 02 Centered on Al, the maximum is 40 from the origin
Lengths up to 3AV2) Vary periodically between lengths at minimum, ie undisturbed conditions. The angular frequency of the periodic quotient fluctuation is 2Ω8. The phase of the interference wave vector has a phase of θ from the I-axis direction. The phase θ is determined by the multipath condition at the receiving point.

Due to the presence of the interference wave vector, the center point of multiplex de-tie No. 3 moves periodically on a straight line between the origin and point 403. FIG. 4 shows the data signal vector when the interfering wave vector has a length of 402 at the midpoint.

At this time, when the multiplexed data signal is demodulated on the I-axis and Q-axis, the center point of each data signal demodulation level is
On the @ axis, it varies from the origin to 405 with the point 404 as the center, and on the Q axis, it varies from the origin to 407 with 406 as the center.・As shown in Figure 7, the vector center of the multiplexed data signal constantly fluctuates due to interference waves, so even if this is demodulated on the ■ axis and the Q axis, the accurate multiplexed data signal as shown in Figure 3 cannot be obtained. information becomes undetectable.

Here, the position 404 on I ab is A (cosθ)v
2, and the position 406 on the Q axis is =A (sino)v
It is 2. Interfering wave vector 408 is vector 4 on Ii
09 can be decomposed into vector 410 on the Q axis, and conversely, by combining vectors 409 and 410, vector 408
can be restored.

In this embodiment, an interference component shown as a vector 408 in FIG. 4 is created in the receiver and subtracted from the received multiplexed data signal to eliminate the interference.This will be explained below.

As shown in FIG. 2, interference waves 203, 204 and 705
is the second harmonic of the stereo difference signal 2, so if the receiver generates the second harmonic of the stereo difference signal 2, the multipath interference waves 203, 204, and 205 will be generated.
It is possible to obtain waveforms that are similar in amplitude and phase but have a similar relationship. That is, a stereo difference signal 2 is extracted from the received signal using a bandpass filter, and by passing this through a square circuit, a second harmonic is obtained as an output. If this second harmonic is shown in comparison with the interference wave vector 408, it becomes a vector 411, whose direction coincides with the opposite direction of the Q axis,
The position 412 of its tip is Q! It becomes 1■2 on 1ill.

When this second harmonic is subjected to Hilbert transformation, a signal having the same amplitude but a phase delayed by 90 degrees is obtained.

The vector of this Hilheld transformed wave is shown at 413.

The position of the tip 414 of the vector 413 is on one axis -2.

If we know the lengths of vectors 409 and 410, we can reduce vector 413 and invert it to create the same vector as vector 409, and reduce vector 411 to create vector 4]
Since the same vector as 0 can be created, if these are combined, the same vector as vector 408 can be created.

In other words, it is sufficient to know each proportionality constant.

On the II axis, the length of vector 409 is A (case)
2, and since the length of the solid ring 413 is 12, the constant of proportionality is -A (case). On Q@h, the length of vector 410 is -A (sinO)v2, and the length of vector 411 is -V2, so the proportionality constant is A (sinO)v2.
nO).

These proportionality constants can be obtained as follows.

Multiplexed data signal 4 and interference waves 203, 204 and 205
is demodulated over a period of several tens of words, and its average value is determined as R. Further, demodulation is performed on the Q axis, and the average value is obtained over a period of several tens of words, and this is set as Do. Here, the word period is equal to twice the reciprocal of the transmission bit rate, and in this case, since the transmission bit rate is 48 kb/s, one word period is 1724000 seconds. T! ll! and Q@
The demodulation levels of the multiplex data signal 4 and the interference wave 20 are respectively
3.204 and 205 are added.

However, since the multiplexed data signal 4 is sent out in a pre-random code, the sent word vectors 303 to 306 (see FIG. 3) are as follows:
If you take an appropriate period of time, each will appear with equal probability. Therefore, for example, if averaged over a 64-word period, I
The data signal components of the demodulation level average values of the axis and Q@ are; As a result, the average value and Do include only the interference waves 203, 204, and 205, and the interference waves can be detected. DI is A
(case) equal to V 2 and DO is −Ax
(sinO) is equal to v2. Here, although the value of ■2 does not change in a short period of time, it may change in a 64-word period, so the time average of the 64-word period is taken and is shown as V2.

On the other hand, the signal obtained by squaring the stereo difference signal 2 is the vector 411 shown in FIG.
Let S be the average value over a 4-word period,
S will be equal to -V 2/2. From these values of o, , Do and S, the proportionality constant -A×(case) and A(
sinO) are found, respectively or/25, D, /
It becomes equal to 2S. Therefore, the interference wave vector 409 of IIJIII is −A (cas
e) obtained by multiplying by DI/25, Q! l1
The disturbance wave vector 410 of lh is the vector 411 of A (
sinO), that is, D0/2S.

As described above, it is possible to create an interference removal wave that is equivalent to the interference wave from the stereo difference signal, and it is possible to eliminate the interference wave.

Next, FIG. 1 is a block diagram showing the configuration of an embodiment that best represents the features of the present invention.

In Figure 1, 101.104.111,112,1
14.115°117, I24.125,126,12
8, 130, 132, 133, 134, and 135 are signals at corresponding positions, respectively.

+02 is a bandpass filter centered at 76kHz that takes out the multiplexed data signal, and 103 is a 38k filter that takes out the stereo difference signal.
) 1z centered bandpass filters, 105, 106 and 12
0 is a multiplication circuit. 107 and 108 are low-pass filters, which take out the baseband signal of the multiplexed data signal from the outputs of the multiplication circuits 1W105 and 106.

12+ is a low pass filter similar to low pass filters 107 and 108, which limits the bandwidth of the signal to the same bandwidth as the multiplexed data signal.

116 is a square circuit. 109, 110 and 122
is an average value calculation circuit, which calculates the average value of the signal for a 64-word period. 119 is a Hilbert transform circuit. 1
13 and 8 are delay circuits, and a low-pass filter 107
It is also used to match the delay of the signal generated in the average value calculation circuit 109. 123 is a delay circuit, and the Hilbert transform circuit 1 is calculated from the delay time of the delay circuit 118.
Delay the value minus the delay time in 19.

127 is a calculation circuit for generating an interference cancellation signal, 129 is an addition circuit, and 131 is a demodulation/carrier recovery circuit.

With the above-described circuit configuration, the ■-axis tone signal 132 and the Q-axis tone signal 133, which are multiplex data signals from which interference has been removed, are obtained from the multiplex data signal included in the human input signal lot.

The human signal 101 is a baseband signal of FM demodulation output,
It consists of the signals shown in the baseband spectrum layout diagram of FIG. 5, and if there is multipath interference, the interference waves 203 to 205 shown in FIG. 2 are also included at the same time. A signal 104 is a signal obtained by adding interference waves 203 to 205 to the QPS-modulated multiplexed data signal 4 extracted by the bandpass filter 102. Signals 134 and 135 are 76k) Iz sine wave signals generated in the demodulation/carrier regeneration circuit 131, and the phase of signal 134 is drop and coincides with the ■ axis and is used for I@ demodulation, and the phase of signal 135 is 90 degrees. It coincides with the Q-axis and is used for Q-axis demodulation.

The signal 104 was multiplied by a 76 kHz sine wave with a phase of 0 degrees and 90 degrees in each multiplier circuit 105 and 106, respectively, and demodulated in each axis of 0 degrees and 90 degrees by passing through low pass filters 107 and 108. It becomes a baseband signal. Then, the average value calculation circuit 109
and 110, respectively, to determine the average value over the 64-word period.

The output signal 111 of the average value calculation circuit +09 is the average value of the I@ demodulated output, and this is the average value of the interference wave as described above. In addition, the output signal 11 of the average value calculation circuit 110
2 is the average value of the Q-axis demodulated output, and this is the average value D0 of the above-mentioned interference wave.

H: The force signals Ill and 112 are input to the low-pass filters +07 and 108, respectively, at a time delayed by 32 word periods, which is half of the 64 word period, and 32 word periods before and after the input. The average value of human power is output.

Therefore, the signal delay time required to calculate the average value is 32
It is a wide period.

The multiplexed data signal 104 containing the interference wave is input to the delay circuit 113, where the delay time is calculated by combining the delay time of the low-pass filter 107 and the delay time of the 32-word period in the average value calculation circuit 109 without being demodulated. A signal 114 delayed by the sum time is output.

Next, a system for creating an interference wave removal waveform from the stereo difference 1'Δ No. 2 will be explained.

The bandpass filter 103 extracts the stereo difference signal 2 from the baseband signal of the human input signal 101. Its output signal 11
5 corresponds to the stereo difference signal 2, the 6th harmonic 115 becomes twice the harmonic through the square path 116, and becomes 1 of 76kllz.
An amplitude modulated wave of 00% modulation +17 is output. Signal +17 is from delay circuit 11B), signal 1 ] 4
, ], 11 and 112 in time, an output signal 125 is obtained. The signal 125 is a signal of a vector 411 whose phase coincides with the negative direction of the Q axis shown in FIG.
This is tentatively called 80. Signal 117 is also input to Hilbert transform circuit +19 and I! It is converted into a signal having a phase that matches the negative direction of ilh, and this is converted into a signal having a phase that matches the negative direction of
The output signal 125 matches the delay of the signal 125. Here, the signal 126 is a signal indicated by the vector 413 shown in the fourth diagram, and is expressed as (on the contrary, S).

It is called.

The signal 117 is also input to a multiplier circuit 120 and multiplied by a 76 ktlz sine wave 135 with a phase of Q
It is demodulated with 1lith. The signal output from the multiplier circuit 120 is limited to the same bandwidth as the spanned signal band of the multiplexed data signal by a low-pass filter 121, and then the average value over a 64-word period is determined by an average value calculation circuit 122. , an output signal 124 is obtained. Signal 124 is the average value S of the second harmonic of the stereo difference signal described above.

A calculation circuit 127 generates an interference wave removal signal. In this, the I-axis signal 126 and the Q@ signal 125, which are the sources of the signals, as well as the signal III DI, the signal 112 DO, and the signal 124 S are manually input. There is. The calculation circuit 127 calculates [(
soxoo÷25)" (S, xO, ÷25)1, the interference wave removal signal 128 is created. This has the same waveform as the interference wave.

The multiplexed data word 114 containing interference waves is sent to an adder circuit 129.
The interference wave cancellation signal 128 is subtracted therefrom, resulting in a multiplexed data signal 130 from which interference waves have been removed.

The demodulation/carrier regeneration circuit 131 is a commonly used demodulation circuit that demodulates a QPSK multiplexed data signal and a carrier regeneration circuit that regenerates carriers that cannot be used in the demodulation circuit. The multiplexed data signal 130 is demodulated by a demodulation/carrier recovery circuit 1.31 to obtain an I-axis modulation signal 132 and a Q-axis modulation signal 133. In addition, demodulation/carrier regeneration circuit +
Among the carriers reproduced at 31, the carrier 134 having the phase of the ■ axis is used by the multiplication circuit 105, and the carrier 135 having the phase of Q@ is used by the multiplication circuit 106 and +20.

As described above, it becomes possible to demodulate the FM multiplex data signal by canceling the interference waves and significantly reducing their influence. This entire circuit can be constructed from analog circuits, digital circuits, or a mixture of both.

Note that in the above explanation, a Hilbert transform circuit was used to create a signal with a phase that matched in the negative direction of the ■ axis to create an interference wave removal signal, but this can be done using other integral transform circuits that produce the same effect. It may be.

[Effects of the Invention] As is clear from the above, according to the present invention, interference can be removed and reduced with a relatively simple circuit configuration by combining currently available circuit techniques.

Further, according to the present invention, great effects can be obtained not only in application to fixed reception but also in application to movement distance A8 where multipath interference is large and its state changes constantly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a layout diagram showing an example of a baseband spectrum of multipath interference, and FIG. 3 is an explanation showing an example of a vector for demodulating multiple data signals. 4 is an explanatory diagram showing an example of a demodulation vector by an interference wave, and FIG. 5 is a layout diagram showing an example of a baseband spectrum of the FM%i data method. 10I, 104, 111.112.1+4j15,11
7,124.125°121i, 128.130.13
2,133,134,135...signal, 102.10
3...-band filter, 105.106, 1.20-...multiplying circuit,! 07.1
08,121...Low pass filter, 109.110,
122...average value calculation circuit, +13. [8,123・
...Delay circuit, +16...Square circuit, 119...Hilbert transform circuit, 127...Calculation circuit, 129...Addition circuit, +31...Demodulation/carrier regeneration circuit. Tsukasa) Applicant: Japan Broadcasting Corporation

Claims (1)

[Claims] 1) A stereo sum channel signal, a pilot signal,
A stereo difference channel signal in which the first subcarrier is suppressed carrier amplitude modulated and a multiplex data channel signal in which the second subcarrier is QPSK modulated are collectively FM modulated and transmitted, and the FM broadcast radio waves are received. a first extracting means for extracting an FM demodulated signal by FM demodulating a radio wave; a first extracting means for extracting the suppressed carrier amplitude modulated stereo difference channel signal from the FM demodulated signal; second extraction means for extracting a modulated multiple data channel signal; generation means for generating a second harmonic of the suppressed carrier amplitude modulated stereo difference channel signal extracted from the first extraction means; integral converting means for integrally converting a second harmonic from the means; and QPSK modulated multiple data channel signal extracted from the second extracting means on the second subcarrier.
detecting means for detecting the level of an interference wave by performing SK demodulation and averaging the demodulated baseband data channel signal over a predetermined period; and detecting the second harmonic from the generating means on the second subcarrier. a second extraction means for synchronously detecting and extracting an average value obtained by averaging the synchronously detected baseband stereo difference channel signal over a predetermined period; forming means for level-correcting the output to form a disturbance wave removal signal based on the disturbance wave level detected by the detection means and the average value taken out from the second extraction means; and from the formation means. FM multiplex data broadcasting characterized by comprising means for removing the interference wave by subtracting the interference wave removal signal from the QPSK modulated multiplex data channel signal extracted from the second extraction means. Receiving machine. 2) The FM multiplex data broadcast receiver according to claim 1, wherein the integral transform means is a Hilbert transform means.