JPH04335726A - Medium wave am stereo broadcast system - Google Patents

Abstract

PURPOSE:To exclude pilot signal disturbance to assist the reception of a stereophonic broadcast in the AM stereo broadcast in which a broadcast carrier is broadcast from plural synchronized medium wave band stations. CONSTITUTION:A subordinate synchronization frequency of 24.9kHz detected from an STL equipment 8 in a subordinate station (b) is used for a PL signal of an AM stereo. That is, the subordinate synchronization frequency of 24.9kHz is inputted to an AM stereo PL signal phase controller P and inputted to a phase adjustment device 16 via a BPF 15, its output is frequency-divided into 25.0Hz by a 1/996 frequency divider 17, amplified by an amplifier 18 and inputted to a stereo exciter 19 as a PL signal. The stereo exciter 19 generates a sum signal M.(L+R) and a difference signal S.(L-R) from L and R signals of a broadcast program signal and uses an orthogonal amplitude modulator by using the signal to apply orthogonal modulation to a 1494kHz carrier inputted from a VCTCXO 14 and the result is broadcast as a stereo signal from a transmitter 20.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AM stereo broadcast system carried out by a plurality of frequency-synchronized medium wave band AM broadcast stations.

0002

[Prior Art] Stereo broadcasting has traditionally been carried out in the very short wave band in Japan, but AM broadcasting in the medium wave band has not been carried out.
High-quality stereo broadcasting is also desired for M broadcasting.

[0003] AM stereo broadcasting in the medium wave band (hereinafter referred to as medium wave stereo broadcasting) is broadcast using various systems in various countries, and each system has advantages and disadvantages. In order to introduce such medium-wave stereo broadcasting, Japan's Ministry of Posts and Telecommunications consulted the Telecommunications Technology Council. In response to this inquiry, the Telecommunications Technology Council recently announced that C-Q, a medium-wave stereo broadcasting system developed by Motorola in Japan, has the advantage of being economically practical and compatible with current monaural broadcasting equipment.
The report recommended that the UAM method (compatible orthogonal amplitude modulation method) should be adopted. In this regard, broadcasting stations must always ensure high-quality stereo broadcasting with good separation between left and right stereo signals for fixed or mobile listeners within the service area.

FIG. 2 shows the C-QU developed by Motorola.
AM (Compatible Quadrature)
This is a system diagram showing an example of an AM) type medium wave stereo broadcasting device, and 21 is an audio matrix, which generates a difference signal S·(L−R) and a sum from the left side signal (L) and right side signal (R) of the audio. A signal M・(L+R) is formed, and a difference signal S・(L−R
) as a quadrature amplitude modulator (or independent sideband modulator (ISB)
(Independent Sideband Sys
tem) method) 22, and the pilot signal (
By adding a signal that assists reception of stereophonic broadcasting (hereinafter abbreviated as PL signal) and performing quadrature amplitude modulation, a broadcast carrier wave having a quadrature modulation phase angle is formed, and this broadcast carrier wave and the audio matrix formed above are combined. sum signal M
- (L+R) is input to the broadcasting device 23 for stereo broadcasting.

In order for a plurality of stereo broadcasting stations configured as described above to perform medium wave stereo broadcasting over a wide service area, each station broadcasts using a broadcasting carrier wave that matches the broadcasting carrier frequency of one standard station. In addition, in order to match the broadcast carrier waves, each station is equipped with a highly stable oscillator, which is
A broadcast carrier wave is formed by slave synchronization with a synchronization signal sent from a reference station.

[0006]

[Problem to be solved by the invention] However, the above,
When stereo broadcasting is performed by a standard station and a plurality of so-called dependent stations that use broadcast carrier waves that are slave-synchronized to that station, even if the synchronization of both the carrier wave and PL signal is perfectly adjusted, there may be interference in radio wave interference areas. In a constant electric field zone, PL signal interference occurs on the receiving side, resulting in a problem of degrading stereo quality.

In view of the above, the present invention provides medium-wave AM stereo broadcasting that eliminates and suppresses PL signal interference occurring in a uniform electric field zone of a radio wave interference area when a plurality of stations synchronizing broadcast carrier waves perform stereo broadcasting. The purpose is to provide a method.

[0008]

[Means for Solving the Problems] The present invention achieves the above objects,
In stereo broadcasting carried out by a plurality of broadcasting stations using synchronized broadcasting carrier waves, a configuration in which the phases of PL signals for assisting stereophonic broadcasting reception are made to almost match in the equal electric field zone of the radio wave interference area between each broadcasting station. achieved by.

[0009]

[Operation] According to the present invention having the above-described structure, PL signal interference occurring in a uniform electric field zone of a radio wave interference area is eliminated, thus making it possible to receive stereo broadcasts of good quality.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below using examples and drawings. FIG. 1 is a block diagram showing the main configuration of broadcasting equipment in an embodiment of the present invention, and (a) is a reference station (hereinafter referred to as
(referred to as a master station), (b) is a main part of a device of a station subordinate to the master station (a) (hereinafter referred to as a dependent station). Hereinafter, this will be explained using a broadcast carrier wave of 1494 kHz as an example.

First, in the master station (a), the oscillation frequency of the highly stable 10 MHz reference oscillator 1 and its 1/2
A frequency of 9.96 MHz is created from the output frequency of the 50 frequency divider 2, passed through a band pass filter (hereinafter abbreviated as BPF) 3, and then 24.9 kHz by the 1/400 frequency divider 4.
Divide the frequency into STL using that as the reference dependent synchronous frequency
(ESTILINK) Modulates the carrier wave of the device 5 and modulates the dependent station (
In b), it is sent out via parabola 6.

The dependent station (b) receives the carrier wave modulated at the dependent synchronization frequency of 24.9 kHz transmitted by the master station (a) through the parabola 7, and
Detects the slave synchronization frequency of 4.9kHz. This 24.
The dependent synchronization frequency of 9kHz is BPF9, phase adjuster 10
After that, it is multiplied by 60 by 60 multiplier 11 and becomes 1494kHz.
z, and inputs it to the phase comparator 13 via the BPF 12. 14 is a VCTCXO (voltage controlled temperature compensated oscillator) that oscillates at 1494 kHz, and its oscillation output is input to the phase comparator 13, and
The comparison voltage VC, which is compared with the slave synchronization frequency input from PF12 and is proportional to the phase difference, is applied to the above-mentioned VCTCXO.
14, the oscillation frequency is adjusted to a carrier frequency of 1494 kHz, which exactly matches the slave synchronization frequency, and the signal is input to the stereo exciter of the slave station (b), which will be described next. In addition, in the above, the phase adjuster 10 is a unique phase adjuster for adjusting the phase difference of the dependent synchronization frequency between a plurality of stations arranged as a master station (a) and a dependent station (b),
Match the reference phase between multiple stations located at different locations.

[0013] In the dependent station (b), the above-mentioned STL device 8
The dependent synchronous frequency of 24.9kHz detected from AM
It is also used as a stereo PL signal. That is, the dependent synchronization frequency of 24.9 kHz is input to the AM stereo PL signal phase control device P, and is input to the phase adjuster 16 via the BPF 15, and the output thereof is converted to 25.0 Hz by the 1/996 frequency divider 17. The signal is frequency-divided into 1, amplified by an amplifier 18, and inputted to a stereo exciter 19 as a PL signal.

The stereo exciter 19 generates a sum signal M.(L+R) from the L signal and R signal of the broadcast program signal.
) and a difference signal S·(L−R) are generated, and the 1494 kHz carrier wave inputted from the VCTCXO 14 is orthogonally modulated using the signal using a quadrature amplitude modulator, and the signal is broadcast in stereo from the transmitter 20.

The present invention performs medium wave stereo broadcasting as described above, but the phase adjuster 16 is connected to the master station (a).
This is to match the phase of the PL signal between the broadcasting station (b) and one or more dependent stations (b), and by adjusting the phase, the received electric field is low in the uniform electric field zone in the radio wave interference area. Even in the case of an electric field, the occurrence of PL signal interference is suppressed.

[0016]

Effects of the Invention As is clear from the above detailed description, the present invention is capable of reducing radio wave interference by using a PL signal to assist reception of stereophonic broadcasts in medium wave stereo broadcasting carried out by a plurality of broadcasting stations broadcasting synchronously. This method eliminates reception disturbances that occur in local uniform electric field zones by nearly matching the phase of the PL signals between each broadcasting station.As a stereo system, it can be implemented not only in the C-QUAM system but also in the ISB system. Since it can be configured extremely economically and easily, it can be expected to have great effects when used in medium wave stereo broadcasting that will be put into practical use in the future.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of main parts of an apparatus in an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a medium wave stereo device.

[Explanation of symbols]

1 Reference oscillator 2 1/250 frequency divider 4 1/400 frequency divider 5 STL device (estilink device) 8
STL device (estilink device) 10 Phase adjuster 11 60 multiplier 13 Phase comparator 14 VCTCXO (voltage controlled temperature compensated oscillator) 1
6 Phase adjuster 17 1/996 frequency divider 19 Stereo exciter 20 Transmitter

Claims (1)

[Claims] [Claim 1] Multiple medium wave AM consisting of a master station and slave stations
It consists of broadcasting stations, and the dependent stations form broadcast carrier waves based on the dependent synchronization frequency transmitted by the master station.
Medium-wave stereo broadcasting is performed using the same broadcasting frequency as the master station, and at that time, a pilot signal to assist stereophonic broadcast reception is formed based on the slave synchronization frequency, and its phase is adjusted to the master station's or slave station's radio frequency. A medium-wave AM stereo broadcasting system that is characterized by adjusting and broadcasting so that they are almost in phase in a uniform electric field area.