JP3033454B2 - Wireless microphone with built-in antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless microphone antenna device.

[0002]

2. Description of the Related Art With the recent development of telecommunication technology and the development of socio-economics, the demand for the use of radio waves has been rapidly increasing. In particular, the demand for wireless communication in a building, a school, or the general society, which has a relatively narrow service area, is rapidly increasing.

In order to cope with such social demands,
Weak radio stations that use extremely weak radio waves that do not require a radio station license, or specific low-power radio stations with an antenna power of about 10 mW or less are institutionalized. An FM wireless microphone is a small wireless device that uses these radio waves to transmit sound wirelessly.

[0004] FM wireless microphones have a long history of development, and the method called the weak wireless microphone is FM.
Of the frequency bands of the broadcasting stations, 76 MHz to 90 MHz, a method that uses a frequency far from the broadcasting frequency as a carrier frequency and performs frequency modulation with an audio signal has been frequently used. However, in recent years, a large amount of unnecessary radiation noise from computers has been generated in the same frequency band, so that the practical service area is inadequate, and the frequency of high-frequency electronic devices has become low, and so on. Practical use has been made possible by frequency allocation in a higher frequency region where the operating frequency of the wireless microphone is 200 MHz and further 800 MHz.

[0005] By the way, in order to radiate a carrier wave of an FM wireless microphone as a radio wave, an antenna is required.
The 200 MHz band and the frequency band of the 800 MHz band are 150 cm and 37.5 cm, respectively. For example, when a generally used 1 / 4λ single type antenna is used,
The mechanical dimensions of the antenna are 37.5 cm and 9.
It is a practical size of 375 cm. If the FM wireless microphone is, for example, a hand-held microphone, the overall length is about 20 cm, which seems to be an easy-to-use size. Therefore, when the above-mentioned single type antenna of 1 / 4λ is attached to the lower end of the hand-held microphone, it is 3 in the 200 MHz band microphone.
A 7.5 cm wire is required, and an 800 MHz band microphone would require a 9.375 cm wire. Since the wire length of the 200 MHz band microphone is too long, 37.5 cm, a shortened antenna in which a shortening coil is inserted in series is often used. In any case, in most cases, the transmitting antenna is provided at the lower end of the handheld microphone.

FIG. 8 is an external view showing a conventional hand-held wireless microphone in the 800 MHz band. In the figure, a hand-held wireless microphone has a microphone section A, a microphone body section B, and an antenna section C, which are more generally configured. The microphone unit A has a configuration in which the protection ring 1 and the microphone unit 3 are built in the windshield 2. The microphone body B is configured to include a cylindrical case upper part 4, a case lower part 5, and a power switch 6. In the figure, C denotes an antenna unit, which is an 800 MHz band microphone in the prior art, and has an antenna structure in which a piano wire of about 9 cm is used as a core wire and covered with a rubber protection member.

As is apparent from FIG. 1, when the microphone body B is used close to the mouth in a hand-held state, it is natural that the antenna C is obstructive. This antenna structure is not preferable from the viewpoint of uncomfortable feeling and robustness when the image is taken.

FIG. 9 is an exploded perspective view showing another conventional example of a hand-held wireless microphone. 10 is a windshield in the figure,
11 is a microphone unit, 12 is a divided part of an inner case, 1
3 is an inner case main body, 14 is a rubber ring, 15 and 16
Is a part of the cylindrical case, 17 is a cover part of the inner case, 1
8 is a switch cover, 19 is a switch knob, 20 is a coaxial connector Ass, y, 21, 22, 23, 24, and 25 are labels. Reference numeral 26 denotes an antenna board on which antenna wires are provided, and 27 and 27 denote buffer members.

In the drawing, reference numeral 28 denotes a main circuit board of the wireless microphone, which supplies an electric signal from the microphone unit 11 to a terminal indicated by CN1 in FIG. Coaxial connector As from terminal
A circuit arrangement is provided in which a carrier frequency signal frequency-modulated with an audio signal is connected and supplied to the antenna substrate 26 via s and y20. In a state where the components shown in this drawing are assembled, the antenna substrate 26 is
The antennas are housed in the inside of the antennas 5 and 16, so that the antenna is not exposed from the main body and obstructed as in the conventional example.

However, the hand-held wireless microphone according to the prior art does not have a sense of incongruity even when, for example, a speaker having the microphone is picked up on a TV picture, and the antenna structure is preferable from the viewpoint of robustness. Was.

FIG. 10 is a block diagram showing the electrical structure of another conventional hand-held wireless microphone shown in FIG. 1
Reference numeral 1 denotes a microphone unit, and the output of the microphone unit 11 is connected and supplied to input terminals 30a and 30b of the microphone amplifier circuit 30. Output terminal 3 of microphone amplifier circuit 30
0d is connected and supplied to the input terminal 31a of the compression circuit 31. The output signal of the output terminal 31b of the compression circuit 31 is supplied to the input terminal 33 of the low-pass filter circuit 33 via the level adjuster 32.
a. An output terminal 33b of the low-pass filter circuit 33 is connected and supplied to an input terminal 34a of the gate circuit 34. The output terminal 34b of the gate circuit 34 is connected and supplied to the input terminal 35a of the VCO circuit 35.

A functional block indicated by T in the figure is a tone oscillating circuit, which comprises an amplifying circuit 45, an amplifying circuit 46 and a crystal oscillator X1 in the figure, and a crystal oscillating circuit. In a state where the circuit between Sb is open,
The configuration is such that the oscillation continues while the power supply voltage V5 is applied. The output signal of the amplifier circuit 46 is supplied to the input terminal 34a of the gate circuit 34 via the level adjuster 47.
Is also connected and supplied.

An output terminal 35b of the VCO circuit 35 is connected to a first output 36b via a buffer amplifier 36 having two outputs.
Is connected to and supplied to an input terminal 37a of a doubling circuit 37, and a second output 36d is connected to and supplied to an input terminal 40a of a PLL circuit 40. The PLL circuit 40 is a functional block including a frequency dividing circuit, a reference oscillation circuit, and a phase comparison circuit. The PLL circuit 40 determines a reference oscillation frequency obtained by dividing the oscillation frequency of the X2 crystal oscillator and an input frequency input to the input terminal 40a. A phase comparison output signal with a frequency signal divided by the frequency division ratio is obtained at an output terminal 40d, and is supplied to an input terminal 35d of the VCO circuit 35.
It forms a locked loop. An input terminal 40b of the PLL circuit 40 is a program input terminal for the frequency division ratio of the frequency dividing circuit, and predetermined frequency division data is supplied from a control output terminal c of the CPU 41 shown in FIG.

In the figure, reference numeral 42 denotes a ROM circuit, which is constituted by an IC in which a unique identification code is written. ROM circuit 4
The second output terminal 42a is connected to the data input terminal a of the CPU 41 and also to the input terminal 35a of the VCO circuit 35. The clock input terminal 42b of the ROM circuit 42 is configured to supply the unique identification code to the input terminal 35a of the VCO circuit 35 when a serial data transfer clock is supplied from the clock output terminal b of the CPU 41.

The CPU 41 is provided with data input terminals g and f, and outputs of the code switches 43 and 44 are connected and supplied, respectively. When the frequency-divided data set by the code switches 43 and 44 is input to the data input terminals g and f of the CPU 41, the PLL circuit 40
Is configured so that the frequency division ratio of the frequency division circuit is input to the program input terminal 40b. The functional block indicated by P in the figure is a power supply circuit, and a contact S of a power switch S
When the circuit between e and Sf is closed, the timing circuit 48
A control signal delayed by a predetermined time is supplied to the gate circuit 49, and the power supply voltage of the power supply battery 51 supplied to the gate circuit 49 is supplied to the DC-DC converter 50 via the gate circuit 49, and the desired circuit voltage is supplied. It is configured to be converted to V1. In the figure, reference numeral 52 denotes a power supply voltage monitoring circuit, which is configured to supply a warning signal from the input terminal h to the CPU 41 when the power supply voltage of the power supply battery 51 falls below a predetermined voltage.

In the figure, a doubling circuit 37 is a circuit for converting an inputted frequency to a doubling frequency, and an output terminal 37b is connected and supplied to an input terminal 38a of a high frequency amplifier circuit 38.
In the figure, reference numeral 38c denotes a power supply terminal. A variable resistor 53 is inserted and connected between the power supply terminal 38c and the bias input terminal 38d, and the output power of the high-frequency amplifier circuit 38 is variably controlled by changing the bias current. ing.

An output terminal 38b of the high-frequency amplifier circuit 38 is connected to an RF output terminal CN2 via a band-pass filter circuit 39. A functional block indicated by 54 in the figure is an antenna circuit on the antenna substrate 26.

The antenna circuit 54 is, for example, an antenna unit C of a hand-held wireless microphone shown in FIG.
For example, in the case of an 800 MHz band microphone, an antenna structure in which a piano wire of about 9 cm is used as a core wire and covered with a rubber protection member may be used.

In FIG. 10, the structure shown in the lower right part of the drawing shows a conventional example of a printed circuit board structure as the antenna circuit 54. In the figure, CN3 is an RF input terminal, which is electrically connected to a conductor pattern (antenna pattern) 26a formed on the antenna substrate 26 at a connection portion CN3. An antenna board 26 is built in a predetermined position of the inner case 13 shown in FIG.
When connected to the circuit board of the wireless microphone at ss, y20, the antenna circuit 54 has a smart appearance structure in which the antenna is not exposed outside the wireless microphone.
A power controller 55 is controlled by an output k of the CPU 41.

Incidentally, there is a method called 3m method for measuring the radiated electric field strength of a wireless microphone or the like. The propagation characteristics of radio waves radiated not only from wireless microphones but also from radio equipment antennas are the characteristics of the combination of the direct wave to the reception antenna and the reflected wave reflected to the ground. The electric field intensity has characteristics with attenuation and enhancement. The attenuation and enhancement characteristics become more pronounced as the frequency of the radio wave used increases. Therefore, a method called the 3m method is a method of normalizing the electric field strength when the frequency of the radio wave to be used and the distance from the transmitting antenna to the receiving antenna are constant, and quantifying the measured value of the electric field strength.

In the 3 m method, a test wireless microphone to be measured for electric field strength is installed at a center position of a rotary turntable having a predetermined height. The height of the rotary turntable is selected to be, for example, about 1.5 m as the ground height at the mouth of an upright speaker in the case of measurement with a wireless microphone. A receiving antenna is installed at a distance of 3 m horizontally from the center of the rotary turntable.
As the receiving antenna, a dipole antenna tuned to the frequency of the radio wave to be used is used. Generally, for convenience, a broadband so-called log-peri antenna or the like may be used.

From the center position of the rotary turntable,
Assuming that the distance to the receiving antenna is R, the ground plane in the range of the ellipse having the radius R from the center of the rotary turntable and the center of the receiving antenna position is at least 1 / 10λ or less of the radio wave frequency used. Form a reflective surface.
When the radiated electric field from the test wireless microphone installed at the center position of the rotary turntable and a predetermined height is received by the receiving antenna installed at the distance of 3 m, the received electric field strength is maximized. The antenna is moved up and down to the height of the receiving antenna to measure the electric field strength.

FIG. 11 is a chart showing a directional characteristic of the electric field strength in the horizontal direction, which is a measurement example in which the electric field strength of the wireless microphone is measured by the 3m method. In the figure, 0 °
The measured value of the electric field strength in the direction indicated by is the measured value of the electric field strength at the reference position assuming that the speaker faces the front of the receiving antenna while holding the wireless microphone under test.

The measurement example of the electric field strength indicated by the solid line E in the figure is the measurement example of the electric field strength of the wireless microphone in which the antenna section C is exposed, which is the conventional example shown in FIG. The measurement example of the electric field strength indicated by the broken line D in the figure is the conventional example shown in FIG. 10, in which the antenna section C is mounted as an antenna board 26 at a predetermined position of the inner case 13 as shown in FIG. 5 is an example of measuring the electric field strength of a wireless microphone with a built-in antenna. Both the wireless microphone in which the antenna unit C is exposed and the wireless microphone with a built-in antenna are configured to supply RF power to a transmitting antenna.
The terminals of the F connector CN2 are adjusted so as to output the same high-frequency power. Here, the RF
A 50 Ω pure resistor is connected to the terminal of the connector CN2, and a wireless microphone that outputs the same high-frequency power whose output high-frequency power is adjusted to, for example, 5 mW is used for measurement. However, while the measured value of the electric field strength (solid line E in the figure) of the wireless microphone in the form in which the antenna section C is exposed is about 65 dBμV at the front position shown in FIG. The measured value of the electric field strength (broken line D in the figure) of the portable wireless microphone shows a low value of approximately 57 dBμV at the front position indicated by 0 ° in the figure. Moreover,
The exposed antenna type wireless microphone shown by the solid line E has substantially uniform horizontal directivity, whereas the antenna built-in type wireless microphone shown by the broken line D has a dip of, for example, a measured value of the electric field strength in the 315 ° direction of about 49 dBμV. Non-uniform horizontal directional characteristics.

The antenna substrate 26 to be built in the built-in antenna type wireless microphone is connected to the coaxial connector Ass, y20 similarly to the exposed antenna type wireless microphone.
It has been confirmed that the electric field intensity substantially equal to that of the solid line A can be obtained when the exposure is performed through the through hole. This means that the radiation efficiency is reduced by incorporating the antenna into the wireless microphone irrespective of the antenna structure and gain.

[0026]

Referring again to the prior art shown in FIG. 9, the cause of the low radiation efficiency of the wireless microphone with a built-in antenna will be considered. In FIG. 9, the antenna substrate 26 is housed in a predetermined position of the inner case 13. The disposition position is stored in a position inside the hand-held portion 16 of the outer case. In the figure, MAI indicated by reference numeral 28
N BOARD is a circuit board of a wireless microphone,
It is configured to be accommodated in a state parallel to a position very close to the antenna substrate 26. The circuit board of the wireless microphone is a high-frequency circuit board on which a conductor pattern is formed. In particular, the high-frequency output circuit section is a high-frequency circuit board on which a wide earth pattern is formed.

However, when the high-frequency circuit board is disposed parallel to a position close to the antenna board 26, the electromagnetic field radiated from the antenna board 26 is widely formed on the high-frequency circuit board. It is conceivable that the reciprocal electromagnetic field generated when the eddy current flows through the ground pattern cancels out the electromagnetic field radiated from the antenna substrate 26. As a result, it can be considered that the antenna radiation efficiency is reduced. When the wireless microphone is used by hand while the antenna substrate 26 is built in the inside of the hand-held portion 16 of the outer case, the electromagnetic field radiated from the antenna substrate 26 penetrates the palm of a human body. Will do. Naturally, the human body contains a lot of moisture, and as with the eddy current loss of the earth pattern described above, using a wireless microphone by hand,
It can be considered that the antenna radiation efficiency is reduced.

As described above, an antenna is required to radiate a carrier wave of an FM wireless microphone as a radio wave, and the carrier frequency is, for example, 800 MHz.
In the case of a band frequency, the wavelength is 37.5 cm. For example, when a generally used 1 / 4λ single type antenna is used, the mechanical size of the antenna is 9.375 cm, which is a practical size. Therefore, if the 1 / 4λ single antenna is mounted as an external antenna at the lower end of the handheld microphone, the intensity of the radiated electric field can be obtained strongly, but the exposed antenna obstructs the appearance and the movable antenna is exposed. Therefore, the external antenna structure was not preferred from the viewpoint of robustness.

Since the wavelength is short, for example, when the antenna is used as an antenna substrate and is housed in a cylindrical case, the antenna is not exposed from the main body and does not become a hindrance. The upper part also became a smart wireless microphone, and the antenna structure was preferable from the viewpoint of robustness. However, the electric field strength of a wireless microphone with a built-in antenna is lower than the electric field strength of a wireless microphone with an exposed antenna, and the radiation efficiency is improved by incorporating an antenna into the wireless microphone regardless of the antenna structure and gain. However, there was a problem that the temperature was reduced.

Furthermore, the exposed antenna type wireless microphone has a substantially uniform horizontal directional characteristic, whereas the built-in antenna type wireless microphone has an uneven horizontal direction in which a dip occurs in the electric field strength when a substrate antenna is incorporated, for example. There was a problem that the directional characteristics were likely to occur. Therefore,
Even with the built-in antenna, there is a demand for a robust wireless microphone with a built-in antenna that can obtain uniform directional characteristics without lowering radiation efficiency.

[0031]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. According to the present invention, a microphone unit, a microphone amplifier circuit, and a high-frequency power amplifier circuit are provided in an insulating housing. A wireless microphone incorporating a series of wireless microphone circuits such as a power supply circuit, wherein one end of an unbalanced high-frequency output of the high-frequency power amplifier circuit is connected to a primary unbalanced input of a transformer via a series capacitor, The other end of the unbalanced high-frequency output of the high-frequency power amplifier circuit is connected to the other end of the primary unbalanced input, and both ends of a hollow loop antenna wound in a coil shape are connected to the secondary balanced output of the transformer, An antenna-equipped wireless microphone having a hollow loop antenna incorporated in the housing is provided.

According to a second aspect of the present invention, in addition to the first aspect, the series capacitor and the transformer are arranged on a matching substrate different from the wireless microphone circuit.

According to a third aspect of the present invention, there is provided a wireless microphone in which a microphone unit and a series of wireless microphone circuits such as a microphone amplifier circuit, a high-frequency power amplifier circuit, and a power supply circuit are built in an insulating housing. One end of the unbalanced high-frequency output of the circuit is connected and supplied to the primary unbalanced input of the transformer via a series capacitor, and the other end of the unbalanced high-frequency output of the high-frequency power amplifier circuit is connected to the other end of the primary unbalanced input. The two ends of a hollow loop antenna wound in a coil shape are connected to the secondary balanced output of the transformer, and the series capacitor and the transformer are arranged on a matching substrate, respectively. A cylindrical or rod-shaped longitudinal casing, wherein the loop surface of the hollow loop antenna is provided on a surface orthogonal to a longitudinal direction of the casing, and the insulating casing is To provide an antenna built-in wireless microphone incorporating the hollow loop antenna therein.

According to a fourth aspect of the present invention, there is provided a wireless microphone in which a microphone unit and a series of wireless microphone circuits such as a microphone amplifier circuit, a high-frequency power amplifier circuit, and a power supply circuit are built in an insulating casing. One end of the unbalanced high-frequency output of the amplifier circuit is connected and supplied to the primary unbalanced input of the transformer via a series capacitor, and the other end of the unbalanced high-frequency output of the high-frequency power amplifier circuit is connected to the other end of the primary unbalanced input. The two ends of a hollow loop antenna wound in a coil shape are connected to the secondary balanced output of the transformer, and the series capacitor and the transformer are respectively disposed on a matching substrate. Is a cylindrical or rod-shaped longitudinal casing, wherein the loop surface of the hollow loop antenna is provided on a surface orthogonal to the longitudinal direction of the casing, and the hollow Power receiving units at both ends of the loop antenna are connected to the transformer balanced output on the matching substrate at positions separated from the hollow portion of the hollow loop antenna, and the built-in antenna type wireless has the hollow loop antenna built in the insulating casing. Provide a microphone.

According to a fifth aspect of the present invention, the transformer is a balun transformer, and the wireless microphone with a built-in antenna according to the first, third, and fourth aspects, and a sixth aspect of the present invention, the antenna element of the hollow loop antenna is provided. 5. The wireless microphone with a built-in antenna according to claim 1, wherein the hollow loop antenna is formed of a metal wire having a spring characteristic and the hollow loop antenna is built in the insulating casing as a shortened coil structure. Things.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Since a wireless microphone with a built-in antenna is desired due to its apparent smartness and robustness, an antenna structure that does not reduce the radiation efficiency while maintaining its specifications will be studied. Conventionally, the radiation efficiency is reduced when the antenna unit is formed of an antenna substrate and is housed inside the cylindrical case of the wireless microphone, because the electromagnetic field radiated from the antenna substrate is reduced by the circuit substrate of the wireless microphone. A major factor is that they are arranged in a direction that passes through. Therefore, the configuration is such that the electromagnetic field radiated from the antenna does not pass through the circuit board of the wireless microphone as much as possible.

For this purpose, the object can be achieved by arranging, for example, a substrate type antenna having a conductor antenna formed on a pattern surface of an antenna substrate on a surface orthogonal to a circuit substrate of the wireless microphone. However, in the case of the hand-held wireless microphone, a cylindrical or rod-shaped main body shape is a necessary condition because it is a hand-held specification. This means that a large area is required for the circuit board of the wireless microphone. Therefore, it is necessary to make the surface of the wireless microphone having a cylindrical or rod-shaped main body vertically sectioned as the circuit board surface of the wireless microphone. . Therefore, only the surface on which the antenna substrate is arranged is a surface obtained by cutting the cylindrical or rod-shaped main body into a ring shape, and can be used as the antenna substrate surface.

The area obtained by cutting the cylindrical or rod-shaped main body into a circle is extremely small, and the maximum practical diameter is about 3 cm. For example, if an attempt is made to form a conductor antenna of an 800 MHz wireless microphone in that dimension, the wavelength is 37.5 cm and 1 /
The conductor antenna length of 2λ is approximately 19 cm, and it is difficult to form a pattern. Thus, a shortened coil type antenna is used as a method for realizing an antenna element that can be accommodated in a cylindrical shape having a diameter of about 3 cm.

In order to accommodate the shortened coil type antenna in the cylindrical housing, the shortened coil type antenna having a spring characteristic is provided so that the coil shape is maintained uniformly. A groove structure in which a hooking projection is provided at an edge portion of the receiving portion having the dimension and shape is formed, and an antenna dimension diameter of the shortened coil type antenna having the spring characteristic before being attached to the receiving portion having the cylindrical dimension and shape. Can be mounted by setting the length of the housing to be smaller than the diameter of the cylindrical housing.

Alternatively, a groove having an annular concave portion is formed in the cylindrical housing portion, and the annular concave portion has, for example, a structure in which the bottom of the groove structure is set to be wide, and The antenna can be mounted by setting the antenna dimension diameter of the shortened coil type antenna having the cylindrical dimension and shape before mounting on the cylindrical dimension and shape accommodation section longer than the cylindrical dimension and shape accommodation section diameter. For example, the shortened coil type antenna can be firmly mounted in the cylindrical housing.

The antenna element length of the shortened coil type antenna is approximately 9c, which is a conductor antenna length of λλ.
m may be used, but 1 / 2λ can be selected as the antenna element length having higher radiation efficiency. In this case, an unbalanced-balanced conversion transformer is generally used as an antenna matching circuit. In order to obtain higher radiation efficiency, a feeder from the conversion transformer to the power receiving section of the 1 / 2λ balanced antenna is connected to the shortened coil type. By disposing the antenna away from the center of the hollow portion of the antenna, the electromagnetic field radiated from the shortened coil type antenna is reduced by half from the conversion transformer.
The antenna element arrangement of the built-in antenna has a structure for preventing a reduction in radiation efficiency due to interference with a power supply unit up to the power receiving unit of the λ balanced antenna.

FIGS. 6 and 7 each show a prototype example in which 1 / 2λ is selected as the shortened coil type antenna element length. One end of the coaxial connector Ass, y20 has an RF connector CN2 electrically connected to the core wire and the sheath wire. Similarly, an RF connector (not numbered) is also electrically connected to the other end at the core wire and the sheath wire. In the figure, reference numeral 60 denotes an antenna matching board,
R for board to be fitted to RF connector at the other end of ss, y20
An F connector, a phase adjustment capacitor (Co) 61, and a conversion transformer 62 are mounted. The wiring and arrangement of the mounted components will be described later.

In FIG. 7, the balanced output from the conversion transformer 62 is supplied to the shortened coil type antenna element 58 by the feeding section.
In FIG. 6, the balanced output from the conversion transformer 62 is arranged such that the feeding portion of the balanced output from the hollow portion of the shortened coil type antenna element 58 is as small as possible in FIG.
It is located at a remote location.

FIG. 1 illustrates an embodiment of a wireless microphone according to the present invention. In the drawing, 10 is a windshield, 11 is a microphone unit, 12 is a divided part of an inner case, 13 is an inner case main body, 15 and 16 are a part of a cylindrical case, and a cylindrical case 16 is a hand-held part. .
17 is a cover part of an inner case, 18 is a switch cover,
19 is a switch knob, 20 is a coaxial connector Ass, y,
Reference numerals 21, 22, 23, and 24 are labels. Reference numeral 60 denotes an antenna matching board, and 27 denotes a buffer member. In the figure, MAIN BOARD indicated by reference numeral 28 is a circuit board of the wireless microphone, and the same parts as those in the conventional configuration of FIG. 9 are denoted by the same reference numerals. The microphone circuit mounted on the circuit board 28 of the wireless microphone employs the same microphone circuit as that shown in FIG. 10, and a specific configuration thereof is omitted.

FIGS. 6 and 7 each show a prototype example showing the arrangement of components mounted on the antenna matching substrate 60 in an antenna structure applicable to the shortened coil type antenna according to the embodiment of the present invention. is there. In the figure, reference numeral 20 denotes a coaxial connector Ass, y as described above. 58 is a shortened coil type antenna element, and 59 is an insulating antenna cover.

The coaxial connector Ass, y20 has an RF terminal at one end.
The connector CN2 is electrically connected to the core wire and the jacket wire, and the core wire at the other end is electrically connected to one end of the shortened coil antenna element 58. The sheath wire at the other end is open. The shortened coil type antenna element 58 as an antenna element is an annular hollow loop antenna having a spring characteristic and wound in a coil shape.
Buried in the concave groove 59a.

Here, the concave groove 59 of the antenna cover 59
The symbol a denotes the groove structure of the annular concave portion, for example, a groove structure in which the bottom of the groove is set wide, and the antenna coil diameter of the shortened coil type antenna having the spring characteristic before being attached to the concave groove 59a of the antenna cover 59. Is set longer than the dimension diameter of the concave groove 59a so that the annular concave portion can be securely mounted in a state where the shortened coil type antenna is housed. The other end of the shortened coil type antenna element 58 is electrically opened and fixed to the concave groove of the antenna cover 59.

An electric signal from the microphone unit 11 is supplied to a terminal indicated by CN1 in the figure via a connection line (not numbered), and is output from an output terminal indicated by CN2 in the figure via a coaxial connector Ass, y20. The carrier frequency signal frequency-modulated by the audio signal is connected to and supplied to an antenna substrate (antenna matching substrate) 60. Antenna matching board 60
The board includes an RF connector for a board, which is fitted to the RF connector at the other end of the coaxial connector Ass, y20, a phase adjustment capacitor 61, and a conversion transformer 62. The feed portion of the balanced output from the conversion transformer 62 is arranged as far away from the hollow portion of the shortened coil type antenna element 58 as possible.

FIG. 3 shows an electric circuit arrangement. In FIG. 6, the balanced output from the conversion transformer 62 has a feed terminal provided at an end of the antenna matching board 60 and one end of the feed terminal is connected to one end 5 of the antenna element 58.
8b, and the other end of the feeding terminal is extended from the other end 58a of the antenna element 58 by a predetermined wire length in a state where the coil is not wound, and connected at the end of the antenna matching substrate 60. Have been.

FIG. 3 shows an electric circuit arrangement configuration, in which 20 is a coaxial connector Ass, y,
A core wire at the other end of the input terminal to which the RF connector CN2 is connected is connected to one end of the phase adjustment capacitor 61. The jacket wire at the other end of the input terminal to which the RF connector CN2 is connected is connected to a common connection terminal of the conversion transformer 62. The other end of the phase modulation capacitor 61 is connected to a first connection terminal of the conversion transformer 62, and the antenna element 58
Is also connected to one end 58b. The other end 58a of the antenna element 58 is connected to the second connection terminal of the conversion transformer 62. The first connection terminal and the second connection terminal of the conversion transformer 62 have a relationship in which winding coils are wound in opposite phases with respect to the common connection terminal, and the first connection terminal of the conversion transformer 62 is When the unbalanced input terminal is used and the common connection terminal is used as the ground input terminal, the conversion transformer 6
The first and second connection terminals have a circuit configuration that acts as a balun to obtain a balanced output.

Although the transformer shown in FIG. 3 is an embodiment of a transformer having a primary ring structure, it is needless to say that a general transformer in which primary and secondary coils are wound can be used. It is.

FIG. 2 shows the radiated electric field strength of the wireless microphone with a built-in antenna substrate shown in FIG. 9 (FIG. 10) and the radiated electric field strength of the wireless microphone with a shortened coil type shown in FIGS. FIG. 7 is a horizontal directional characteristic diagram comparing FIG. D in the figure is a front position indicated by 0 °, which is approximately 5 °.
The measured value of 7 dBμV is shown. The measured value of the electric field strength in the direction of 315 ° is about 49 dBμV, which is a non-uniform horizontal direction directivity characteristic in which a dip has occurred.

In the drawing, the characteristic diagram of the electric field strength indicated by the two-dot chain line of G is obtained by measuring a prototype example when 1 / 2λ is selected as the antenna element length shown in FIG. At the front position, the measured value is approximately 75 dBμV. In addition, the measured values of the electric field strength show almost uniform values in all the angular directions. The characteristic diagram of the electric field strength indicated by the dashed line F in FIG. 7 is the above-mentioned diagram in the case of another prototype when 1 / 2λ is selected as the antenna element length.
The electric field intensity characteristics were slightly reduced to approximately 7 dB at the front position indicated by 0 ° from the electric field intensity characteristics indicated by the two-dot chain line of G, but the electric field intensity characteristics were stable.

According to the results of the above-described trial production experiments, the wireless microphone with a shortened coil type provided a better radiation electric field strength than the wireless microphone with a built-in antenna substrate, which was far higher than the wireless microphone with an external antenna shown in FIG. A strong electric field strength was obtained.

FIG. 4 is a diagram showing a change in electric field strength when the capacitance value of the phase adjustment capacitor 61 shown in FIG. 6 is changed. 808 as the carrier frequency of the wireless microphone
In the case of a fixed frequency of MHz, the highest measured value of 77.2 dBμV is obtained when the capacitance value of the phase modulation capacitor 61 is 12 pF. FIG. 5 is a diagram showing a change in electric field strength when the capacitance value of the phase modulation capacitor 61 shown in FIG. 6 is fixed to 12 pF and the carrier frequency of the wireless microphone is changed. 807.7 as the carrier frequency
At the frequency of 5 MHz, the highest measured value of 77.4 dBμV is obtained.
It can be seen that there is not much change in the electric field strength in the frequency range up to 9.750 MHz.

[0056]

According to the present invention, in spite of the wireless microphone with built-in antenna according to the first aspect, the radiated electric field intensity equal to or higher than that of the conventional external antenna type is obtained with uniform horizontal directivity. As a result, it is possible to provide a wireless system with a wide service area in which the radio wave reach of the wireless microphone is improved. In addition, since the wireless microphone has a built-in antenna, it is possible to provide a smart wireless microphone in which a disturbing wire antenna or the like is not exposed.

According to the second aspect of the present invention, by separately providing the antenna matching substrate, the housing of the microphone can be made compact, and the antenna matching circuit mounted on the antenna matching substrate is located at a position very close to the feeder of the antenna element. By arranging them, a wireless microphone with high matching efficiency can be provided.

According to a third aspect of the present invention, the loop surface of the loop antenna is provided on a surface orthogonal to the longitudinal direction of the microphone housing. The vertical polarization characteristics of the radiated electric field strength are the same as those of the wireless microphone provided outside in the direction parallel to the longitudinal direction of the microphone housing. A matching high-efficiency wireless microphone can be provided.

Further, in the fourth aspect, the directional characteristics are good and the electric field strength is large. According to the fifth aspect of the present invention, a wireless microphone having a high matching conversion efficiency can be provided by a balun transformer having a primary ring structure capable of obtaining a high coupling coefficient.

According to a sixth aspect of the present invention, a springy conductive material is used as the built-in antenna element, and a shortened coil type antenna element having a springy property is embedded in the antenna case, so that the accuracy of the antenna diameter is maintained uniformly, and the antenna is stable. Electric field strength is obtained,
Effects such as providing a wireless microphone excellent in robustness and assemblability can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a wireless microphone with a built-in antenna according to the present invention.

FIG. 2 is a horizontal directional characteristic diagram comparing electric field strengths of a wireless microphone with a built-in antenna of the present invention and a conventional wireless microphone.

FIG. 3 is an electric circuit layout configuration diagram of the present invention.

FIG. 4 is a characteristic diagram of electric field strength when the phase modulation capacitor in FIG. 6 of the present invention is changed.

FIG. 5 shows a case where the capacitance of the phase adjustment capacitor shown in FIG.
FIG. 6 is a diagram showing a change in electric field strength when the carrier frequency of the wireless microphone is changed when the frequency is fixed at.

FIG. 6 is a layout diagram of an antenna matching substrate according to an embodiment of the present invention.

FIG. 7 is a layout view of an antenna matching substrate according to another embodiment of the present invention.

FIG. 8 is an external perspective view of a conventional wireless microphone.

FIG. 9 is an exploded perspective view of another conventional wireless microphone.

FIG. 10 is a block diagram showing an electrical configuration of the wireless microphone of the conventional example shown in FIG.

FIG. 11 is a horizontal directional characteristic diagram comparing electric field strengths of a conventional wireless microphone.

[Explanation of symbols]

11: microphone unit, 13: inner case body, 15,
16: Part of the cylindrical case, 20: Coaxial connector Ass,
y, 38: high frequency amplifier circuit, 58: shortened coil type antenna element, 59: antenna cover, 60: antenna matching board, 61: phase adjusting capacitor, 62: conversion transformer.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04R 1/04 H04B 1/04

Claims (6)

(57) [Claims] 1. A wireless microphone in which a microphone unit and a series of wireless microphone circuits such as a microphone amplifier circuit, a high-frequency power amplifier circuit, and a power supply circuit are built in an insulating housing, wherein the wireless high-frequency power amplifier circuit has One end of the balanced high-frequency output is connected to the primary unbalanced input of the transformer via a series capacitor, and the other end of the unbalanced high-frequency output of the high-frequency power amplifier circuit is connected to the other end of the primary unbalanced input; A wireless microphone with a built-in antenna, wherein both ends of a hollow loop antenna wound in a coil shape are connected to a secondary balanced output of a transformer, and the hollow loop antenna is built in the housing. 2. The wireless microphone with a built-in antenna according to claim 1, wherein said series capacitor and said transformer are disposed on a matching substrate different from said wireless microphone circuit. 3. A wireless microphone having a built-in microphone unit and a series of wireless microphone circuits such as a microphone amplifier circuit, a high-frequency power amplifier circuit, and a power supply circuit inside an insulating casing, wherein the wireless microphone has an integrated circuit. One end of the balanced high-frequency output is connected and supplied to the primary unbalanced input of the transformer via a series capacitor, and the other end of the unbalanced high-frequency output of the high-frequency power amplifier circuit is connected to the other end of the primary unbalanced input, The two ends of a hollow loop antenna wound in a coil shape are connected to the secondary balanced output of the transformer, and the series capacitor and the transformer are provided on a matching substrate, respectively. Alternatively, in the case of a rod-shaped elongated housing, the loop surface of the hollow loop antenna is provided on a surface orthogonal to the longitudinal direction of the housing, and the inside of the insulating housing is Built-in antenna wireless microphones, characterized in that a built-in loop antenna. 4. A wireless microphone in which a microphone unit and a series of wireless microphone circuits such as a microphone amplifier circuit, a high-frequency power amplifier circuit, and a power supply circuit are built inside an insulating housing, wherein the wireless high-frequency power amplifier circuit has One end of the balanced high-frequency output is connected and supplied to the primary unbalanced input of the transformer via a series capacitor, and the other end of the unbalanced high-frequency output of the high-frequency power amplifier circuit is connected to the other end of the primary unbalanced input, The two ends of a hollow loop antenna wound in a coil shape are connected to the secondary balanced output of the transformer, and the series capacitor and the transformer are provided on a matching substrate, respectively. Alternatively, in the case of a rod-shaped long-shaped housing, the loop surface of the hollow loop antenna is provided on a surface orthogonal to the longitudinal direction of the housing, and both ends of the hollow loop antenna are provided. A built-in antenna, wherein an electric part is connected to the transformer balanced output on the matching substrate at a position separated from the hollow part of the hollow loop antenna, and the hollow loop antenna is built in the insulating casing. Type wireless microphone. 5. The wireless microphone with a built-in antenna according to claim 1, wherein said transformer is a balun transformer. 6. An antenna element of the hollow loop antenna, wherein the antenna element is made of a metal wire having a spring characteristic, and the hollow loop antenna is built in the insulating casing as a shortened coil structure. Item 7. A wireless microphone with a built-in antenna according to items 1, 3, and 4.