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? FM multiplex communication phase difference measuring apparatus App. No. 50-8206 ?
Japanese Patent Application No. 44-53757 [Phase] Application No. 44 (1969) July 9 @ inventor
Murakami Hitoshi Yokohama City Totsuka Ward 352 Yabecho Totsukahiko Kawasaki City Ikuta
72140 Application Cai Den Den Co., Ltd. [With] Agent Attorney Naoe Shibata
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of
the measuring apparatus according to the present invention, FIG. 2 shows a graph showing
characteristics of the L circuit, and FIG. 3 is another embodiment of the present invention. FIG.
4A to FIG. 4C are explanatory diagrams showing an example of the measured waveform in the
device of the present invention, and FIG. 5A to FIG. 5C are explanatory diagrams similarly
showing waveforms at the time of measurement, FIG. FIG. 7 is a block diagram showing the
transmission side of the multiple modulation system in the HFM-FM system, and FIG. 7 is a block
diagram showing the demodulation system on the same reception side.
DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for
measuring a phase difference between respective signals of a combined wave of an FM
(frequency modulated) signal and a non-FM signal in FM multiplex communication. In particular,
by introducing the composite wave into a composite circuit consisting of two circuits that do not
pass through a delay circuit and a circuit that does not pass through, it is possible to measure the
phase difference between each signal very simply and reliably. It is One example of FM multiplex
communication is HFM stereo broadcasting. As is well known, this system has better utilization of
broadcast radio waves than AM system, and only one receiver is required to receive the
broadcast [111111], and the balance between the left and right sounds is not lost So it is
extremely good, but it still has the following disadvantages. Incidentally, although what is widely
used as an FM stereo system is the so-called AM-FM system, the present invention is directed to
the HFM-FM system, which will be described below. In stereo broadcasting by the FM-FM system,
as in the AM-FM system, signals are transmitted by a method called a so-called sum-difference
system. The sound signal (L signal) input from the microphone on the left side and the signal (R
signal) input from the eight on the right side of the sound source are transmitted through the
matrix circuit 1 as shown in FIG. MA) Generate a sum signal of IJ LUX power and R, and on the
other hand, generate a difference signal of MAD IJ Nox output L-R, superimpose these two
signals by the mixer 2 and send it on one radio wave It is a thing. In multiplex modulation at that
time, the subcarrier (frequency Fs) is first FM (frequency modulated) with a difference signal, and
then this modulated wave is superimposed on the sum signal, and then this superimposed signal
The main carrier (frequency FC) is operated to FM. It should be noted that since the main carrier
FC generally has a wide bandwidth, it is used to modulate the main carrier as a whole with two
signal components by the non-FM sum signal and the subcarrier by FM with the difference
signal. It is Incidentally, reference numeral 2 in FIG. 6 denotes a superimposer, 3 denotes a
frequency modulation circuit of a subcarrier (frequency Fs), and 4 denotes a frequency
modulation circuit of a main carrier (frequency FC). On the other hand, on the reception side, as
shown in FIG. 7, the incoming radio wave is demodulated by the frequency discriminator 5 of the
center frequency f, and the demodulated output is converted to a sum signal and a subcarrier
(frequency Fc) FMed by the difference signal. After separation, the difference signal is further
demodulated by the frequency discriminator 6 of the center frequency f, and then the two signals
are passed through the matrix circuit 7 to be extracted as 2L and 2R left and right signal
components [111111] EndPage: 1 It is doing so.
As shown in L, in the FM-FM multiple modulation method, the two signal components of the HLfold signal R signal are converted into a sum signal and a difference signal, and the subcarrier is
once frequency-modulated with this difference signal. Since the signal which is superimposed on
the sum signal and then further superimposed is subjected to frequency modulation as a whole,
in order to keep the degree of isolation of each signal component in the best state, 1 ии (from the
matrix circuit 1 on the transmitting side) The delay time of the sum signal up to the matrix circuit
7 on the receiving side must be equal to the delay time of the difference signal. In other words,
on the transmitter side j, the delay time between the two signals is equalized or (1) it is necessary
to keep this at a constant value, and the carrier main carrier f as described above. Because a wide
band frequency characteristic is used for the point, for the point L, the delay time between the
two signals at A 'and A' in FIG. 6 is accurately calibrated. It will be good. As far as the phase
difference measuring apparatus HFM-FM system useful for this calibration is concerned, it is not
known yet, and rather than measuring and calibrating this, a delay circuit set to a predicted value
is incorporated in the sum signal circuit on the transmitting side. In fact, it is considered that
there is no way to calibrate other than adjusting this to one standard transmitter and the other to
match it. In the 'FM-FM method, unlike the conventional AM-FM method, the waveform can not
be read out by the onograph, and therefore calibration can not be performed as easily as in the
conventional method. In view of the above point, the present invention proposes a new
measuring device which can have the same function as that of the conventional AM-FM method,
and solve the above inconvenience. . In the block diagram of FIG. 1, 11 is an input terminal, 12 is
a divider, 13 is a delay circuit, and the delay time is (n? / 2?fs) ( Let n ('i positive total, the
same applies hereinafter). 14 is a superimposer and 15 is an output terminal. According to the
present invention, a measuring apparatus having a circuit configuration as described in the
present invention, for measuring the phase difference, is derived at the point A in FIG. 6 with
respect to the input end 'f11 Introduce a signal. That is, first, the sum signal (L + R,) [111111]
and the difference signal (L-R) are output from the matrix circuit 1 in the transmitter. Next, the
subcarrier (frequency f8) modulated with the above difference signal is obtained by the
frequency modulation circuit 3, the subcarrier modulated with this difference signal and the sum
signal are superimposed by the superimposer 2, and A superimposed wave of L О R) + (L?R,)
FM) is derived.
Then, a stereo multiplexed signal ((L ? R,) ▒ (L?R) FM) derived at point A is introduced to the
input terminal 11 of the measuring apparatus shown in FIG. In the measuring apparatus, this
stereo multiplexed signal is divided into two systems through the divider 12, and one is not
passed through one delay circuit and is directly led to the superimposer 14, and the other is
passed through the delay circuit 13. It is introduced into the superposer 14. That is, the signal
components appearing immediately after the first distributor 12 become the respective signals of
the sum signal and the subcarrier (frequency f8) modulated with the difference signal. Of these
two signals, the waveform of the system passing through the delay circuit 13 is set such that the
delay time of the circuit 13 is (n? / 2?f8), in other words, the subcarrier (frequency f8)
becomes the sum signal On the other hand, since the reverse phase is set, the waveform
immediately after passing through the circuit 13 is 180 ░ out of phase with the waveform of the
reverse phase with respect to the other output signal to the divider 12 Become. Therefore, by
superimposing the two signals having different phases again, it is possible to obtain an amplitude
frequency characteristic as shown in FIG. 2 and a circuit characteristic having a delay time as
shown in FIG. become. Incidentally, since the delay time of the delay circuit 13 is set to (n? /
2?f8), the delay time shown in FIG. 2 becomes / ri (1/2) и (n? / 2?f8) as a superimposed wave.
In the following, these points will be described in detail. As described above, since the delay
circuit 13 is set such that the subcarrier (frequency f) is in reverse phase, signals passing through
the circuit and signals not passing through the circuit are Are mutually offset with respect to the
frequency fs and their amplitudes become zero (see FIG. 2), while fluctuation of the input
frequency or output frequency centered on this subcarrier (frequency f8), ie, the sum The
frequency fluctuation corresponding to the signal or the difference signal appears as a
symmetrical amplitude waveform centered on the subcarrier frequency fs. These relationships
will be described with reference to FIG. In FIG. 4, the waveform corresponding to the sum signal
of waveform (A): (L + R,) [111111] EndPage: 2 Let its frequency be fa. Waveform layer):
waveform modulated with frequency by difference signal of (L?R) иии: composite waveform of
waveform (A) and waveform (B), and signal wave of (B) is signal wave of (B) Indicates a
modulated state. Note that the amplitudes of the above (i) and (ii) waveforms are At- and A ',
respectively, so that the waveforms (и и и the amplitude becomes A + A'. The symbol ? indicates
the phase difference between the (i) signal and the modulation signal ?).
In the measurement apparatus of the present invention, when a composite wave as shown in FIG.
4 is introduced to the input terminal 11, this signal is divided by the divider 12 into a circuit
passing through the delay circuit 13 and a circuit not passing through it. 7. As a result, the
superimposed wave of both signals has a waveform as shown in FIG. 5 due to the amplitude
characteristic of FIG. That is, since the subcarrier frequency f8 mutually cancels each other, it
does not appear at all as an amplitude ratio, and only the frequency fluctuation (f8 ▒ ?f)
centering on the subcarrier frequency f appears as an amplitude ratio. As mentioned above, since
the signal in FIG. 4 has a carrier frequency of f8, a modulation frequency of fa, and a frequency
displacement of f, the amplitude ratio can be considered as i / p, (f5 ▒ f) becomes U1 / q (see
FIG. 2). In this respect, the amplitudes of the signals in FIG. 4 and the mouth become A / p and Al
/ q, and become a signal (FIG. 5) delayed by (1/2) и (n? / 2?f8) Means Therefore, the synthetic
wave signal in FIG. 4A appears as a waveform layer whose full amplitude is (A / p + A '/ q), that
is, a waveform layer surrounded by two curves as shown in FIG. 5C, and two curves are As a
result, a shift a appears at the intersection point. Since the deviation aU indicates the abovedescribed phase difference ?, W111111 can be obtained by simply and surely knowing the
delay between the sum signal and the difference signal by measuring this deviation. Of course,
the observation 6 of the output waveform is performed through an oscillograph. FIG. 3 shows
another embodiment of the measuring apparatus according to the present invention, in which
reference numeral 16 is an impedance conversion circuit, 17 is a delay circuit consisting of a
waveguide as an example, and the waveguide is terminated. Are set so that the input waveform of
the delay circuit population and the reflected wave are in reverse phase at the subcarrier
frequency f. When the delay circuit configured in this way is connected to the signal line as
shown in the figure, it exhibits characteristics with the same amplitude frequency characteristics
and delay time as in the previous example. As a result, the phase difference is detected in the
same manner as described above. It is possible. Incidentally, if necessary, the circuit 6 can be a
coaxial line or a low pass filter. As described above, according to the present invention,
measurement of the delay (phase difference) of the sum signal and the difference signal in the
FM-FM method, which has hitherto been considered impossible, can be carried out by a direct
vision method using an onosillograph. And the measurement circuit has a simple configuration in
which an input signal is divided into a signal passing through a delay circuit and a signal not
passing through the delay circuit and then superimposed again, so that a stable measurement
apparatus can be provided. Have an industrial effect.
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