JPH01206707A - Frequency discriminator - Google Patents

Abstract

PURPOSE:To detect a signal frequency-modulated without distortion by constituting a resonance circuit with using spiral coils, which are respectively formed as a coil to participate in resonance by a conductor foil provided on an insulating plate. CONSTITUTION:A frequency discriminator is composed by equipping first and second resonance circuits 27 and 28 and for these resonance circuits, spiral coils 11 and 12, which are respectively formed by the conductor foil provided on the insulating plate, are used as the coil to participate in the resonance. Then, the resonating characteristic of those coils is smoothly set to be suitable. Thus, out of an input signal added to an input terminal 6, the straight polarity part of the input signal is tuned by the second resonance circuit 28 and detected by a diode 8. After that, the high frequency component of the signal is removed by a capacitor 22 and a resistance 24 and the signal is outputted from an output terminal 7. On the other hand, out of the input signal to be added to the input terminal 6, the negative polarity part of the signal is tuned by the first resonance circuit 27. Then, after the signal receives the detection in a diode 17 and the removal of the high frequency component in a capacitor 21 and a resistance 23, the signal is outputted from the output terminal 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a frequency discriminator used in demodulation circuits of satellite broadcast receivers, satellite communication receivers, and the like.

(Prior art) Conventionally, a signal applied to an input terminal is branched and input into two resonant circuits with different resonant frequencies, and the output of one of these resonant circuits is detected by a diode in the forward direction, while the output of the other is detected by a diode in the opposite direction. A frequency discriminator is known that detects waves with diodes in both directions, synthesizes the detected outputs, and outputs the result from an output terminal. The resonant frequencies of the two resonant circuits are different from each other such that the frequency discriminator exhibits the well-known S-shaped frequency characteristic curve. Each of the above-mentioned resonant circuits is composed of a capacitor and an air-core coil. It is extremely difficult to improve the quality. In other words, since the Q of the air-core coils provided in each of the two resonant circuits is high, the central part of the S-shaped frequency characteristic curve obtained by combining the forward detection characteristics and the reverse detection characteristics curves upward and downward. The object of the present invention is to provide a frequency discriminator with good linearity in the center of an S-shaped frequency characteristic curve.

(Means to Solve the Problem) In order to solve this object, the measures described in the claims have been taken, and their effects are as follows.

(Function) In manufacturing a frequency discriminator, an insulating plate, ie, a circuit board, is prepared, to which conductive foils constituting input terminals, output terminals, first and second coils, etc. are attached. Next, first and second capacitors and detection diodes are mounted at predetermined positions on the circuit board and connected by soldering. For example, the cathode side of the first detection diode is connected to the first resonant circuit. The second detection diode is connected to the second resonant circuit in a direction opposite to that of the first detection diode, for example, on the anode side.

The frequency discriminator manufactured as described above does not require adjustment of the first resonant circuit or the second resonant circuit. Since the first resonant circuit and the second resonant circuit each use a spiral coil formed of conductive foil attached to an insulating plate as a coil involved in resonance, the resonance characteristics of both of them are moderately gentle. It is. Therefore, the frequency discrimination characteristic obtained by adding together the resonance characteristics of the first and second resonance circuits having mutually different resonance frequencies with opposite polarities is:
The linearity of the central portion of the S-shaped frequency characteristic curve is particularly good.

(Example) The drawings showing the embodiments of the present application will be described below.

FIG. 1 is a front view of the frequency discriminator, and FIG. 2 is a rear view thereof. 1 is a circuit board, for example, a double-sided printed board is used. 2 is an insulating plate, for example, a glass cloth/epoxy resin plate having a thickness of 16 mm. A conductor foil 3 is attached to the front side, and a conductor foil 4 is attached to the back side. These conductor foils 3 and 4 are made of silver foil having a thickness of 35 μtH, for example. Reference numeral 5 indicates a through hole for electrically connecting the conductor foil 3 on the front side of the circuit board 1 and the conductor foil 4 on the back side. 6 is an input terminal to which a signal to be FM detected is added. 7 is an output terminal, from which an FM detected signal is output. 8 is a voltage supply terminal to which a voltage for setting a reference voltage of the FM detection output is applied. The input terminal 6, output terminal 7, and voltage supply terminal 8 are each formed of conductive foil. 9
shows a choke coil constructed by winding polyurethane-coated copper wire. Both ends 10 and 10 of the choke coil 9 pass through a hole in the circuit board 1 and are soldered to a conductive foil on the back side. Reference numeral 11 indicates a first coil, and reference numeral 12 indicates a second coil. These coils 11 and 12 are each formed as a rectangular spiral coil on the front side of the circuit board.
A conductor foil constituting a ground conductor 13 is provided on the opposing back side. 14 is the ground conductor, through hole 5
It is electrically connected to the ground conductor 13 by.

15 is the first capacitor, 16 is the second capacitor,
Chip capacitors are used. The coil 11 and the capacitor 15 constitute a first resonant circuit, and the coil 12 and the capacitor 16 constitute a second resonant circuit. The first
The first resonant circuit is resonant at a higher resonant frequency in the S-shaped frequency characteristic curve, and the second resonant circuit is resonant at a lower resonant frequency. Next, 17 is a first detection diode, and 18 is a second detection diode. diode 1
The leads 19 and 19 at both ends of the diode 18 and the adhesives 20 and 20 at both ends of the diode 18 pass through holes in the circuit board 1 and are soldered to the conductive foil on the back side.

21 and 22 are capacitors, and chip capacitors are used. 23 and 24 indicate resistors, and chip resistors are used.

Next, FIG. 3 shows an equivalent circuit of the frequency discriminator having the above configuration. Elements corresponding to those in FIG. 1 and FIG. 2 are designated by the same reference numerals, and redundant explanations will be omitted. 25, indicated by a dotted line, is a resistance showing a loss of 4, which occurs because the conductive foil forming the coil 11 is attached to the insulating plate 2, and 26, indicated by a dotted line, is a resistance showing a similar loss for the coil 12. Reference numeral 27 indicates the above-mentioned first resonant circuit, and 28 indicates the above-mentioned second resonant circuit.

In the frequency discriminator having the above configuration, the positive polarity portion of the input signal applied to the input terminal 6 is tuned by the second resonant circuit 28 and detected by the diode 18, and then the part of the input signal applied to the input terminal 6 is tuned by the second resonant circuit 28 and detected by the diode 18.
2 and the resistor 24 remove high frequency components from the signal and output from the output terminal 7. On the other hand, the negative polarity portion of the input signal applied to the input terminal 6 is tuned by the first resonant circuit 27,
Detection with diode 17, capacitor 21 and resistor 23
After receiving the high frequency component removal at , the signal is output from the output terminal 7.

In the above case, the resistors 23 and 24 also function as part of the load.

Next, the solid lines in FIGS. 4 and 5 indicate the S-shaped frequency characteristic curves of the frequency discriminators shown in FIGS. 1 and 2. Although it has an inverted S-shape in FIG. 4, this is also referred to as an S-shaped frequency characteristic curve in this specification for convenience. 1. Figure 5 is number 4.
FIG. 2 is a characteristic diagram showing an enlarged portion of the used band in the figure. It can be seen that good linearity is shown in the center of the S-shape, which is the frequency band used.

For reference, coil 1 in resonance circuits 27 and 28
．． 1. , 1.2 The characteristics of a conventional frequency discriminator using an air-core coil are shown by dotted lines in Figure 4.

In addition, in order to obtain the above characteristics, coil 1] has a width of 0.2
A 5 mm conductive foil was constructed with the number of bends shown in FIG. 1, and the coil 12 was similarly constructed with a 0.25 mm wide conductive foil with the number of bends shown in FIG. Furthermore, the first capacitor 15 is 3 pF,
The second capacitor 16 was configured with 7 pF. The dimensions of the circuit board 1 are 1.7 mm in length and approximately 20 mtn in width. Further, the voltage applied to the voltage supply terminal 8 is 6V.

The above example uses a glass cloth/epoxy resin copper-clad laminate as a circuit board. The dielectric constant of the material of this insulating plate is about 45, and the dielectric loss tangent is about 0.02. Therefore, if the insulating plate is made of other materials, such as paper or phenolic resin, both the dielectric constant and the dielectric voltage contact will be much lower than in the above embodiment, so the first and second coils will be The length may be made shorter than that of the above embodiment. In the case of Teflon resin as a glass cloth base material, both the relative dielectric constant and the dielectric loss tangent are smaller than those in the examples shown in Figures 1 and 2, so the length of the coil is made longer than in the examples shown in Figures 1 and 2. do it.

(Effects of the Invention) As described above, in the present application, it is possible to improve the linearity of the center portion of the S-shaped frequency characteristic curve that appears in the relationship between the frequency of the input signal and the detected voltage. This means that a frequency discriminator that can detect frequency-modulated signals without distortion can be provided.

Moreover, since the good characteristics can be obtained at the time of manufacture without any adjustment, it is inexpensive.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application; FIG. 1 is a front view of the frequency discriminator, FIG. 2 is a back view of the frequency discriminator, and FIG. 3 is an equivalent of the frequency discriminator in FIGS. 1 and 2. Circuit diagram, Figure 4 is a diagram showing the S-shaped frequency characteristic curve of the frequency discriminator, Figure 5
The figure is a characteristic diagram showing an enlarged portion of the used band in FIG. 4. DESCRIPTION OF SYMBOLS 1... Circuit board, 2... Insulating board, 3... Conductor foil,
4... Conductor foil, 6... Input terminal, 7... Output terminal, 11... First Koinope 12... Second coil,
15...First capacitor, 16...Second capacitor, 17...First detection diode, 18...Second detection diode, 25°26...Resistance indicating coil loss , 27... first resonant circuit, 28... second
resonant circuit. Patent applicant: Maspro Electric Works Co., Ltd. Representative Takashi Hatayama

Claims (1)

[Claims] An input terminal and an output terminal both formed of conductive foil are provided on the insulating plate, and a cascade circuit including a first resonant circuit and a first detection diode is mounted on the insulating plate, and a second resonant circuit is mounted on the insulating plate. It is also equipped with a cascade circuit of a resonant circuit and a second detection diode, and furthermore, the ends of the two resonant circuits that are not connected to the diode are connected to the input terminal with conductive foil, and In the frequency discriminator, the ends of the diodes not connected to the resonant circuit are respectively connected to the output terminal, and the first resonant circuit is formed by a first coil and a first capacitor.
Further, the second resonant circuit is constituted by a second coil and a second capacitor, respectively, and the first coil and the second coil are each formed as a spiral coil by conductive foil attached on an insulating plate. A frequency discriminator characterized by: