JPH06132990A - Fm multiplex signal receiving indicator - Google Patents

Abstract

PURPOSE:To prevent an erroneous display due to a pulse noise by detecting the presence or absence of a timing clock signal, and displaying that an multiple signal is received only during a period of time when the timing clock signal is detected. CONSTITUTION:An FM multiplex signal reception indicator 10 is equipped with a clock detecting part 11 which detects the timing clock, and an indicator 12 which displays the presence or absence of the reception of the signal according to the detection signal of the clock detecting part 11. Then, the presence or absence of the timing clock signal for demodulating the data of the FM multiplex signal is detected, and the indicator 12 displays that the signal is received only during the period of time when the timing clock signal is detected. Therefore, when the signal is not received, the timing clock signal can be prevented from being generated due to each signal even when a multi-path and a pulse noise is present.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indicator for displaying the fact that an FM multiplex signal is being received to inform the user, and more particularly to preventing erroneous display due to pulse noise such as multipath in the present invention.

[0002]

2. Description of the Related Art Conventionally, FM (F
There is an FM multiple signal reception indicator used in a receiver. In recent years, there has been a demand for development of a receiver for the FM multiplex broadcasting for mobile devices, in accordance with the movement toward practical use. FIG. 4 is a diagram showing a frequency spectrum of FM multiplex broadcasting. As shown in the figure, the frequency spectrum of the FM multiplex broadcast has a stereo sum signal, a pilot signal,
It is composed of stereo difference signals and multiple signals. Therefore, to detect whether the multiplex signal is being received, the frequency region of the spectrum of the multiplex signal is filtered, and if the power of the spectrum is present, reception is indicated.

[0003]

However, the conventional F
The M multiplex signal reception indicator may be affected by multipath distortion, pulse noise, etc. in mobile reception, and there may be power even though the multiplex signal is not actually received. There is a problem.

Therefore, in view of the above problems, it is an object of the present invention to provide an FM multiple signal reception indicator which does not cause an erroneous display due to multipath or the like.

[0005]

In order to solve the above problems, the present invention provides an F which indicates whether or not an FM multiplex signal is received.
The M multiplex signal reception indicator is provided with a clock detection unit and an indicator. The clock detector detects the presence or absence of a timing clock signal for demodulating the FM multiplex signal data.

The indicator is for indicating that the signal is being received only while the timing clock signal is being detected.

[0007]

According to the FM multiplex signal reception indicator of the present invention, the presence or absence of the timing clock signal for demodulating the data of the FM multiplex signal is detected, and the signal is received only while the timing clock signal is being detected. By displaying, the timing clock signal is not generated by these signals even if there are multipaths and pulse noises when no signal is received.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In the present invention, attention is paid to the fact that the synchronous detection and the differential detection used as the multiplex signal reception system reproduce the timing clock. As the modulation method of the multiplex signal, MSK which is a method for moving bodies is used.

FIG. 1 is a diagram showing an FM multiple signal reception indicator according to an embodiment of the present invention, which utilizes a differential detection system. As shown in the figure, the MSK receiver 10
An FM multiple signal reception indicator 10 is provided at 0.
First, the MSK receiving unit 100 comprises a mixer 101 for inputting a modulated wave of a digital signal as a multiplexed signal, and a delayer 102 for delaying the modulated signal by 1 bit and multiplying it by the input signal of the mixer 101. .

When the modulated signal f (t) of the multiplex signal is given here, f (t) = Acos (ωt + φ (t)) where ω: angular frequency of carrier signal, φ (t): MS
It represents the phase by the K (Mimimum Sift Keying) method. φ
(T) is specifically as follows. φ (t) = (πa / 2T) t + φ0 where a is 1 when the data is “1” and “0”
In the case −1, T is a 1-bit time length, φ
0 is the phase of the previous bit.

FIG. 2 is a diagram showing a phase according to the MSK method. As shown in this figure, the phase φ of the MSK method changes from data “1” “0” “1” “1” “0” to “1” so that the phase is π / It increases by 2 and decreases by π / 2 by "0". Furthermore, the solid line of this figure,
As shown by the dotted line, when the input signal f (t) of the mixer 101 is used and the output signal f (t−T) of the delay device 102 is given, f (t−T) = Acos {ω (t−T) + φ (t −T)} and the output signal F (t) of the mixer 101 is F (t) = f (t) (t) · f (t−T) = A ² cos (ωt + φ (t)) · cos { ω (t-T) + φ (t-T)} = A 2/2 [cos {ω (2t-T) + φ (t) + φ (t-T)} + cos {(ωT) + φ (t) -φ ( t-T)}].

The MSK receiving section 100 further includes a mixer 101.
And a low pass filter 103 connected to. The output of the low pass filter 103 removes high frequency components,
The modulated wave signal is converted into a detection signal as follows. ^{FD (t) = (A 2} /2) cos {(ωT) + φ (t) -φ (t-T)} where, when ωT = π / 2, in a manner for mobile is f in omega = 2 [pi] f = consists a 76 kHz T = 1 / 16K and (f is the carrier frequency) FD (t) = (a 2/2) sin {φ (t) -φ (t-T)}.

The above equation φ (t) = (πa / 2T) t + φ0
With, a ^{FD (t) = (A 2} /2) sin (πa / 2). The MSK receiving unit 100 further includes a timing clock reproducing unit 104 which is connected to the mixer 103 and reproduces a timing clock, and a code demodulating unit 105 which demodulates the output signal of the low pass filter 105 into data by the timing clock reproducing unit. To do. The timing clock reproducing unit 104 is composed of a PLL (Phase Lock Loop) and forms a timing clock based on the output of the low pass filter 103. Code demodulating unit 105 in each timing clock ^{FD (t) = (A 2} /2) sin (πa /
The positive / negative of 2) is judged, and if positive, the data is judged as "1", and if negative, it is judged as "0". In this way, the timing clock is always formed in order to demodulate the code.

Next, the FM multiple signal reception indicator 10
Is a clock detection unit 11 that detects a timing clock.
And an indicator 12 for displaying the presence or absence of reception by the detection signal of the clock detection unit 11. The clock detector 11 is connected to the timing clock regenerator 104 and delays the timing clock signal by 1 bit.
And an exclusive OR gate 2 that takes the exclusive OR of the output signals of the timing clock recovery unit 104 and the delay device 1. The indicator 12 includes a resistor 3 that is connected to the exclusive OR gate 2 and adjusts the magnitude of current, and a light emitting diode 4 that has an anode connected to one of the resistors and a cathode that is grounded to receive and display an FM multiplex signal. Including.

FIG. 3 is a timing chart for explaining the operation of the FM multiple signal reception indicator. This Figure 3 (a)
In the figure, the output waveform from the timing clock reproducing unit 104 is shown. An output waveform from the delay device 1 is shown in FIG. The output waveform from the exclusive OR gate 2 is shown in FIG. Therefore, when the output signal of the exclusive OR gate 2 is "H (high)", it is a period during which the multiplexed signal is being received, and when the output signal is "L (low)", the multiplexed signal is It is a period when no signal is received.

Therefore, according to this embodiment, since the timing clock is not reproduced unless the multiplex signal is received, the timing signal is divided from the MSK receiving section 100, and the reception can be confirmed by the presence or absence of this timing clock signal. Become. Also, most receivers are digital, so they detect like a stereo indicator,
Since no step such as amplification is required, the circuit can be made compact and inexpensive.

Although the case where the timing clock obtained by the differential detection is used has been described above, the same operation and effect can be obtained by the similar FM multiple signal reception indicator when the timing clock obtained by the synchronous detection is used. To be

[0018]

As described above, according to the present invention, F
The presence or absence of the timing clock signal for demodulating the data of the M multiplex signal is detected, and the fact that the timing clock signal is being received is displayed during the detection period. Even if there is multipath and pulse noise, these signals do not generate a timing clock signal, and erroneous display is prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing an FM multiplex signal reception indicator according to an embodiment of the present invention, which utilizes differential detection.

FIG. 2 is a diagram showing phases according to the MSK method.

FIG. 3 is a timing chart illustrating the operation of the FM multiple signal reception indicator.

FIG. 4 is a diagram showing a frequency spectrum of FM multiplex broadcasting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Delay device 2 ... Exclusive OR gate 3 ... Resistor 4 ... Light emitting diode 10 ... FM multiplex signal reception indicator 11 ... Clock detection unit 12 ... Indicator 100 ... MSK reception unit 101 ... Mixer 102 ... Delay device 103 ... Low pass filter 104 ... Timing clock recovery unit 105 ... Code demodulation unit 105

Claims (1)

[Claims] 1. An F indicating whether or not an FM multiplex signal has been received.
An M multiplex signal reception indicator, a clock detection unit (11) for detecting the presence or absence of a timing clock signal for demodulating the data of the FM multiplex signal, and receiving only during the period in which the timing clock signal is detected. And an indicator (12) indicating that the FM multiplex signal reception indicator.