DE1271774B - Device for the stereo reproduction of signals according to the FCC method - Google Patents

Description

GERMAN WfTWSl PATENT OFFICE

EDITORIAL

H04h

German class: 21 a2-16 / 03

Number: 1 271 774

File number: P 12 71 774.7-31 (N 26599)

1 271 774 filing date: April 21, 1965

Open date: 4th July 1968

The invention relates to a device for the stereophonic reproduction of signals the FCC procedure. For these purposes, a receiving device has already been proposed which an information channel allowing the information signals to pass through and, in parallel, an auxiliary carrier channel, which filters out the pilot signal and the one frequency doubler to recover the subcarrier owns, as well as contains a so-called ring demodulator. The ring demodulator exists of four rectifiers connected in series with the same polarity, which are combined to form a ring, in its ring branches formed by the rectifier optionally switched on impedances are. The information channel and the auxiliary carrier channel have two opposite branch points of the ring, while the other two junction points are connected to the two output channels are connected.

Tests have shown that with these receiving devices the quality of the monaural Playback does not meet expectations, especially with monaural signals of small amplitude perfectly sufficient. This is due to the fact that at the time of takeover, i.e. when that Signal changes its polarity, so that one diode would be conductive and the other would have to be blocked one diode is not yet conductive and the other is already blocked. This causes non-linear distortions, which are expressed on the one hand in an increase in the distortion factor and on the other hand also worsen the signal-to-noise ratio. The non-linear distortions result in mixed products formed by inaudible noise components which then fall into the audible range.

The aim of the invention is to create a receiving device of the type mentioned in the opening paragraph, wherein in a surprisingly simple way, the non-linear distortion in the monaural reproduction is considerable be reduced.

Based on a device for stereophonic reproduction of signals according to the FCC method, which has an information channel that allows the information signals to pass through and, in parallel, an auxiliary carrier channel that filters out the pilot signal and a frequency doubler for recovering the auxiliary carrier signal, as well as a demodulator part that contains four with the same polarity in Series-connected rectifier, which are combined to form a ring, in whose ring branches formed by the rectifier impedances are switched on, the information channel and the subcarrier device for stereophonic reproduction
of signals according to the FCC method

Applicant:

NV Philips' Gloeilampenfabrieken,
Eindhoven (Netherlands)

Representative:

Dipl.-Ing. E.-E. Walther, patent attorney,
2000 Hamburg 1, Mönckebergstr. 7th

Named as inventor:

Petrus Willem Zwollo, Eindhoven (Netherlands)
Claimed priority:

Netherlands of April 25, 1964 (6404602) - ■

canal are connected to two opposite diagonal points of the ring, while the two remaining Diagonal points are connected to the two output channels, the invention is therefore characterized in that that the rectifiers of the ring are set uniformly in the forward direction so that with positive polarity of the monaural input signal, those in opposite ring branches switched on rectifier and with negative polarity the other rectifiers are conductive and that one pair of rectifiers is already conducting when the other pair of rectifiers is blocked.

The invention and its advantages are explained in more detail below with reference to the figures.

Fig. 1 shows a stereophonic receiver with a device according to the invention;

F i g. 2 shows a frequency diagram, and

F i g. 3 shows a detailed circuit diagram to explain the device according to the invention.

The in F i g. 1 shown stereophony receiver is suitable for receiving the frequency-modulated on the same carrier frequency signals that are derived from the sum signal A + B of the coherent stereophony signals A and B, z. B. in the range from 30 to 15,000 Hz, and the difference signal A-B amplitude-modulated by carrier wave suppression to a subcarrier frequency of 38 kHz and a pilot signal of 19 kHz (FCC method), the modulation thus obtained

809 568/398

signal in the range of 30 to 53,000 Hz which is used to indicate the presence of a local

Has carrier frequency with a maximum swing of 75 kHz carrier wave oscillation,

frequency modulated. At the center tap of the coupling coil 26 is

The stereophonic receiver is equipped with a receiver that only lets the information signals through

receiving antenna 1 and an intermediate frequency stage 2 5 of the low-pass filter 27 of the information channel 14 to

with a mixing stage and one connected to it, whereby to regain the coherent

closing oscillator 3, the stereophonic signals A and B being the ends

Mixture obtained intermediate frequency oscillations of the coupling coil 26 with the diagonal points 61,

are connected in the range of 10 700 kHz after amplification 62 (see FIG. 3) of a ring 46 and

and any limitation in the intermediate frequency io each of the ring branches the series connection of one

stage 2 are fed to an output filter, the series resistor 32, 33, 34, 35 and a DC

is formed by two coupled circles 4, S. includes rectifier 28, 29, 30, 31, being rectifier

The band filter 4, 5 forms part of a per se 28, 29, 30, 31 in the direction of rotation of the ring 46 for the detection of normal frequency modulation - have the same transmission direction. The two transmissions known frequency detector and contains 15 rectifiers 28, 29 and the two rectifiers 30, two connected to the ends of the circuit 5, in pairs form an electronic switch in 31, passing current in opposite directions whereby the output voltages of the two rectifiers 6, 7, which are connected to an output impedance 8 electronic switches 28, 29 and 30, 31, with a center tap point being taken from the diagonal points 63, 64 of the ring 46 to the end of one of the output resistors 36, 36 'of the circular coil 4 20 Coupling coil 9 is connected. The output resistors 36, 36 'of the two electrical output impedance 8 of the frequency detector consists of ironic switches 28, 29 and 30, 31 are made up of a resistor 10, which is connected by the series of the coherent stereophonic signals A and B of two capacitors 11, 12 also removed, which is bridged via a separate playback of a grounded connection point and a 25 channels 37, 38 existing low frequency amplifier smoothing capacitor 13, wherein the output voltage of the frequency detector supplied to the playback devices 39, 40 are the mit-. The low-frequency amplifiers are designed in the same manner taken from the output resistor 10 and have transistors 41, 42,. whose emitter circuits are not bridged resistors

Then occurs at the output impedance of the frequency 30 43 containing 44, wherein the amplified coherent quenzdetektors 6, 7, an output voltage of the transistors 41 shown in the collector circuits of Fig. 2 in the frequency diagram in signals A and B, 42 existing AusgangsimpeGestalt on, which, as can be seen from the figure, are taken from 50, 51, which, as is shown schematically in from the sum signal A + B in the range of the figure, over separating 30 to 15,000 Hz, the on the Subcarrier frequency 35 capacitors 47, 48 with the playback device of 38 kHz with carrier frequency suppression modulations 39, 40 are connected. Crosstalk between the second difference signal ^ iB in the frequency range of the reproduction channels 37, 38 is shown in the illustrated from 23,000 to 53,000 Hz and the pilot signal from the device in a simple manner by a

19,000 Hz is composed. negotiated between the emitter circuits 43, 44 of the transistors To the coherent stereophonic signals 40 ^ 41, 42 switched shunt resistor 49

and B from the output set illustrated in FIG. 2 , which can be adjusted for this purpose. In this voltage of the frequency detector 6, 7 a crosstalk level of better than -40 db was obtained, these signals are directed to a device, which is carried out with stereophonic reproduction, which is drawn in parallel on the input side. The effect of the circuit when receiving the output voltage of the frequency detector 45 catching stereophonic signals is similar to the transmitting information channel 14 and a pilot channel 15 1149 396 which only transmits the pilot signal in the circuit according to the German interpretation.

with a frequency doubler housed in it.

20 for generating the subcarrier frequency of 38 kHz signal of the in FIG. 2 includes the type of supplies illustrated. In the illustrated embodiment contains 5 °, the device described a stereophonic the pilot channel, an input pilot filter 16, and a playback excellent quality, and a pilot amplifier connected as a transistor 17, for the monaural input signal. B. in the frequency band output circuit one through two coupled circuits 18, from 30 to 15,000 Hz is in this device

19 contains formed pilot filter, the output achieved a monaural reproduction. In this case voltage is supplied to the frequency doubler 20 55 namely the pilot channel 15 does not deliver any local carrier, which is formed by a push-pull rectifier with the frequency, so that direct transmission of the monaural rectifier 21, 22 and an output resistance input signal via the electronic switches 28, 23 is formed . 29, 30, 31 on the separate playback channels 37,

At the output circuit of the frequency doubler 38 takes place. Depending on the polarity of the

20, a transistor 24 60 input signal connected as an amplifier is connected to each of the two electronic ones, the collector circuit of which is permeable to a circuit rectifier tuned to the switches 28, 29 and 30, 31 in each case to one of the subcarrier frequency of 38 kHz. With an input signal 25 and a display instrument 45 in the form of a positive polarity, for. B. contains the rectifier 29, 30 AC current meter. The local carrier 65 obtained through fre- in the ring 46 conductive and the rectifier 28, 31 quenzverdoppler 20 blocked, while conversely at an input frequency after amplification in the transistor 24 signal of negative polarity, the rectifier 29, 30 via the circuit 25 of a coupling coil 26 supplied, blocks and the rectifier 28,31 are conductive. About the display instrument 45 a deflection the alternately conductive rectifiers 28, 29, 30,

Claims (1)

31, the monaural input signal is transmitted to the output impedances of the electronic switches 28, 29, 30, 31 formed by the resistors 36, 36 '. In addition to a simple embodiment, the described device offers the possibility of receiving a stereophonic or monaural input signal to automatically achieve a stereophonic or a monaural reproduction without mechanical switching, while the display instrument 45 indicates whether a stereophonic or a monaural input signal is being received. It was found, however, that the reproduction quality with a monaural input signal, in particular with a low amplitude, did not meet the expectations and that the cause was due to the non-linear effects occurring at the time of takeover, i. H. at the points in time at which the transmission of the monaural signal of a pair of rectifiers 29, 30 or 28, 31 is taken over by the other pair 28, 31 or 29, 30. The distortions in the monaural signal caused by these non-linear effects are e.g. B. in the order of several percent. While maintaining the excellent reproduction quality achieved with a stereophonic input signal, according to the invention, the monaural reproduction quality is also considerably improved in a surprisingly simple manner, in that the connection point 52 of the series resistor 34 and the rectifier 30 in one ring branch and the corresponding connection point 33 in the opposite ring branch 29, 33 are connected to terminal 56 of the supply voltage source via a separate resistor 54 or 55, the other grounded terminal 57 of the supply voltage source being connected to the diagonal points connected to these output resistors 36, 36 'via the two output resistors 36, 36' as direct current-passing connections of the ring 46 is connected. The DC voltage source supplies a practically identical presetting in the forward direction for all rectifiers 28, 29, 30, 31 of the ring 46. To illustrate the course of the direct currents, FIG. 3, the ring 46 is shown, the same elements being denoted by the same reference numerals. The diagonal points to which the coupling coil 26 is connected are denoted by 61,62; the diagonal points to which the output resistors 36, 36 'are connected are denoted by 63, 64. The direct current flowing from the supply voltage terminal 56 via the resistor 54, 55 is distributed via the resistors 33 and 34 and the circuits with the rectifiers 29, 31 and 30, 28 and is then transferred to the output resistors 36, 36 ' Terminal 57 of the supply source flow, the direct current in the two circuits with the rectifiers 29, 31 and 30, 28 providing a presetting of the rectifiers 29, 31, 30, 28 in the forward direction. For symmetry, all rectifiers 29, 31, 30, 28 have practically the same presetting in the forward direction, which can be easily set to a desired value by making the two resistors 54, 55 jointly adjustable. As a result of the same presetting of the rectifiers 28, 29, 30, 31 ', the stereophonic reproduction is not adversely affected in any way, which, as stated above, is already of excellent quality. When a monaural input signal is fed to the center tap of the coupling coil 26, the rectifiers 28, 31 will be conductive in the manner described above if the polarity of the monaural input signal is positive and the rectifiers 29, 30 will be conductive if the polarity is negative. As a result of the presetting of the rectifiers in the forward direction, the distortions caused by the non-linear effects at the takeover times are considerably reduced, since at the times at which one pair of rectifiers 28, 31 or 29, 30 is blocked, the other pair of rectifiers 29, 30 or 28, 31 is already conductive due to the presetting in the forward direction. The improvement achieved is substantial. If the size of the presetting of the rectifiers 28, 29 or 30, 31 is regulated by the joint setting of the resistors 54, 55, it results that at a certain value of the setting current a relatively strong minimum occurs in the distortion of the monaural signal reproduction, where the distortion level has decreased by a factor of about 10. With the rectifiers of the AA-119 type used, there was a minimum distortion level with a setting current of around 3 μΩ. In addition to the excellent stereophonic reproduction quality, the particular simplicity of the construction and the possibility of adjustment, the device according to the invention has a significant improvement in the monaural reproduction quality, while it was further established that as a result of the presetting of the rectifiers 28, 29, 30, 31 a certain compensation of the Scattering of the rectifier characteristics is achieved. In a device of the type described, which has been extensively tested in practice, individual parts with the following data were used: Rectifiers 28, 29, 30, 31 .... 4 · AA 119 resistors 54, 55 1.5 MOhm resistors 32, 33, 34, 35 15 kOhm output resistors 36, 36 '47 kOhm supply voltage 15V Patent claims: 1. A device for the stereophonic reproduction of signals according to the FCC method, which has an information channel permitting the information signals and, in parallel, an auxiliary carrier channel that filters out the pilot signal and a frequency doubler for recovering the auxiliary carrier signal, as well as a demodulator part that contains four with the same polarity in series has switched rectifiers, which are combined into a ring, in whose ring branches formed by the rectifier impedances are switched on, the information channel and the auxiliary carrier channel are connected to two opposite diagonal points of the ring, while the two remaining diagonal points are connected to the two output channels, thereby characterized in that the rectifiers (28 ... 31) of the ring (46) are set uniformly in the forward direction so that with positive polarity of the monaural input