JPH0221181B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides an FM device equipped with a small booster amplifier.
The present invention relates to a receiving antenna device in which a selection circuit for switching between intervening and non-intervening booster amplifiers depending on the strength of a received signal is also formed on the same insulating substrate as the antenna conductor.

In recent years, FM broadcasting has been rapidly becoming popular, and along with this, playback equipment including FM tuners have improved and improvements have been made to achieve high fidelity playback. However, one of the factors that hinders such high-fidelity reproduction is the problem with antennas. This problem is caused by the fact that high-performance FM antennas are generally large and difficult to install due to housing conditions. In other words, the allocated frequency band for domestic FM broadcasting is 76 to 90 MHZ, and the total length of a half-wavelength dipole antenna is approximately 166 to 197 cm (181.5 cm at the center frequency). No matter how high-performance such an antenna is, it cannot be installed indoors, so by installing a feeder antenna, etc.
The reality is that they are forced to sacrifice their original performance.

For this reason, as shown in FIGS. 1a to 1c, a circular printed wiring board 1 with a diameter of about ten centimeters has a loop-shaped antenna conductor on its outer periphery that is wide and partially open. 2, and a pair of tuning circuit connection conductors 3 and 4 extending inward from the open end of the antenna conductor 2, as well as a pair of conductors 3 and 4 extending inward from the feed point on the opposite side, which is substantially opposite to the open end of the antenna conductor 2. Connection conductor 5 and connection conductor 6 of the extended amplifier circuit
A circuit pattern 8 for mounting booster amplifier components, which will be described later, is simultaneously formed in the vicinity of these connection conductors 5 and 6. A circuit component group as shown in FIG. 2 is mounted on the surface of the printed wiring board 1 formed in this way. In this case, first, variable capacitors for tuning are connected to the connection conductors 3 and 4.
VC is connected thereto, thereby forming an antenna main body ANT in which a tuning circuit is directly connected to the antenna conductor 2. Each component constituting the booster amplifier AMP that should be directly connected to the antenna main body ANT is mounted. In the booster amplifier AMP having the connecting conductors 5 and 6 as input ends, one conductor 5 side is connected to the base of the transistor TR1 via the capacitor C1, and the other conductor 6 is connected to the emitter of the transistor TR1. The transistor TR1
A series circuit of a capacitor C2 and a resistor R1 is interposed and connected between the base and collector of. Further, a series circuit of a resistor R2 and a capacitor C3 is interposed and connected between the base and emitter of the transistor TR1. Furthermore, the collector of the transistor TR1 is connected to one output terminal 9 via a capacitor C4 and inductances L1 and L2, and is also connected to a transformer T1.
It is connected to the connection point between the resistor R2 and the capacitor C3 via. On the other hand, one of the capacitors C5 is connected to the connection point of the inductances L1 and L2, and the other of the capacitors C5 is connected to the emitter of the transistor TR1 and to the other output side 10 which is the ground side. Furthermore, the connection point between the resistor R2 and the capacitor C3 is connected to the output terminal 10 via a resistor R3, a choke coil RFC, and a power source E.

As shown in FIG. 3, the antenna device configured as described above is an equivalent representation of the antenna device 11 shown in FIG.
The signal is guided to a mixer 102 via a high frequency amplifier 101, where it is converted to an intermediate frequency by injecting a local signal from a local oscillator 103, and then sent to the next stage, such as a discriminator, via an intermediate frequency amplifier 104. It is something that is sent out.

However, in the antenna device configured as shown in Figures 1 to 3, the radio waves incident on the antenna conductor are always outputted via the booster amplifier regardless of the distance from the FM broadcasting station or the strength of the electric field. It will be introduced in Chiyuna. This means that when receiving at a strong electric field point, the strong radio waves are further amplified by the booster circuit, so the FM
Since the signal input to the tuner exceeds the allowable input signal of the FM tuner, distortion occurs in the output of the FM tuner. In order to prevent this, it is possible to install a circuit that turns the booster amplifier on and off depending on the electric field strength, but if you simply install a switch to switch the booster amplifier, it will be difficult to connect the wiring to the switch. This has drawbacks such as deterioration of the SN and the need for wiring work due to the wiring, and variations in product performance due to uneven wiring.

The present invention eliminates the above-mentioned drawbacks and uses an antenna device formed on the same printed wiring board as the antenna conductor, etc., to provide a switch that selectively switches the booster amplifier to the intervening or non-intervening state depending on the state of the electric field strength. This is what we provide.

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 4 to 5, but the same parts as in FIGS. 1 to 3 are designated by the same numbers, and the explanation thereof will be omitted.

That is, in the present invention, as shown in FIG. 4, a connecting conductor 7, figure a, is newly provided from the antenna conductor 2, and a switch SW is provided on the surface of the printed wiring board 1, figure b. As shown in FIG. 5, the connecting conductor 7 connected to the antenna conductor 2 is connected to the first fixed contact SA of one switch S1 of the switches SW, and this switch S1
The second fixed contact SB is connected from the collector of the transistor TR1 to a capacitor C4 in series and an inductance L2 connected in series to these via an inductance L1. Also this switch S1
The movable contact Sc is connected to one output end 9.
Further, the first fixed contact SA of the other switch S2 of the switches SW has an open end, and the second fixed contact SA has an open end.
SB is connected from the base of the transistor TR1 through a resistor R2 and a resistor 3 in series to a chiyoke coil RFC which is further connected in series with these.

Further, the movable contact Sc of the switch S2 is connected to the output end 10 via the power source E. The switches S1 and S2 of the switch SW are interlocked, and when the movable contact Sc of the switch S1 is the first fixed contact SA, the movable contact Sc of the switch S2 is also the first fixed contact.
In this relationship, each movable contact Sc is connected to either the first or second fixed contact SA or SB.

Furthermore, 12 in FIG. 6 is an antenna device equivalently shown in FIG.
This figure shows the state in which it is connected to the front end section of the FM tuner 111.

According to the antenna device configured as described above, a weak electric field (a state far away from a normal broadcasting station) is present.
Assuming that the switches S1 and S2 are connected to the first fixed contact SA side, the output signal from the antenna conductor 2 is led out to the output terminals 9 and 10 via the connecting conductors 6 and 7. be done. At this time,
Since the signal received by the antenna conductor 2 has a weak electric field, the received signals delivered to the output ends 9 and 10 are extremely small. If the FM tuner 111 receives the signal in this state, the SN will be extremely poor.
Therefore, move the movable contacts Sc of switches S1 and S2 to the second position.
When switching to the fixed contact SB side, the received signal received by antenna conductor 2 is guided to connection conductors 5 and 6,
Output terminal 9,1 via booster amplifier AMP
It is derived as a strong received signal amplified to 0, and when this signal is applied to the FM tuner 111,
SN is improved.

Next, suppose that the switches S1 and S2 are connected to the second fixed contact SB under a strong electric field (very close to a broadcasting station or the same conditions).
The received signal is output from the antenna conductor 2 through the connection conductors 5 and 6 to the output terminals 9 and 10 via the booster amplifier AMP, and the strong received signal is further strengthened by the booster amplifier AMP.
Therefore, when the FM tuner 111 receives this, the level exceeds the allowable input signal and the FM tuner 1
A distorted output signal will be output from the front end section No. 11.

For this reason, each switch S1, S2 of switch SW
When the movable contact Sc is connected to the fixed contact SA side (the state shown in the figure), the received signal received by the antenna conductor 2 is led out to the output ends 9 and 10 via the connection conductors 7 and 6. At this time, the received signal can be directly received from the antenna conductor 2 without going through the booster amplifier AMP, and can be directly guided to the output end. Since this signal is within the allowable input signal range of the FM tuner 111, the FM tuner 111 that receives this signal can reproduce a signal without distortion.

Therefore, when the antenna device is installed in a place with a weak electric field, the movable contacts of each switch S1 and S2
Sc is switched to the second fixed contact SB side and guided to the output terminals 9 and 10 through the booster amplifier, and when the antenna device is installed in a place with a strong electric field, the movable contact Sc of each switch S1 and S2 is switched to the first fixed contact SB side. Switching to the contact SA side, the received signal received by the antenna conductor 2 is directly guided to the output sides 9 and 10 and reproduced within the range of allowable input signals of the FM tuner 111. In other words, when the electric field is weak, the second fixed contact SB
By switching the movable contact Sc to the first stationary contact SA side, and switching the movable contact Sc to the first fixed contact SA side when the electric field is strong, a received signal having a desired electric field strength can be introduced into the FM tuner 111.

When switch S1 selects booster amplifier AMP, the fixed contact SB in switch S1
In SA, high frequency signals are electrically coupled due to stray capacitance between fixed contacts. However, the fixed contact SA of switch S1 is connected to the booster amplifier AMP.
It is connected to a different connecting conductor 7 from the connecting conductor 6 connected to the input of the input terminal. Therefore, output end 1
The amplified high-frequency signal between 0 and the fixed contact SB is fed back between the connecting conductors 6 and 7 due to the stray capacitance. When the amplified high-frequency signal is fed back between the connecting conductors 6 and 5, positive feedback occurs and oscillation occurs at a frequency where the phases are in-phase, but in the present invention, the connection is made between the connecting conductors 6 and 7. Therefore, booster amplifier AMP can prevent oscillation without creating a positive feedback loop.

As described above, the antenna device of the present invention includes an antenna conductor, a tuning circuit that tunes to a desired signal received by the antenna conductor, and a booster amplifier that amplifies the received signal on the same printed wiring board. The antenna conductor, tuning circuit, Since there is no need to run a cord to connect between the booster amplifier and the changeover switch, the performance of the antenna device itself can be made uniform, and since the changeover switch is also installed on the printed wiring board, the connection point with the switch can be set as short as possible. The need for installing a switch and connecting wires does not interfere with the antenna device.

Furthermore, the fact that the antenna conductor, tuning circuit, booster amplifier, and changeover switch are formed on the same printed wiring board has the advantage that these parts can be connected at the same time using an automatic soldering device after being inserted into the predetermined positions. Also plays.

Furthermore, by switching a switch on the same printed wiring board, the received signal can be supplied to the FM tuner in a state where it has the electric field strength by directing it through a booster amplifier or directly without going through it.

[Brief explanation of drawings]

1A to 1C are back views, front views, and side views of a printed wiring board for explaining the present invention; FIG. 2 is a circuit diagram formed on the printed wiring board shown in FIG. 1;
The figure is a connection diagram connecting the circuit diagram of Fig. 2 and the FM tuner section, and Figs. 5 is a circuit diagram formed on the printed wiring board shown in FIG. 4, and FIG. 6 is a connection diagram showing a state in which the circuit shown in FIG. 5 and the FM tuner are connected. 1...Printed wiring board, 2...Antenna conductor, 5,
6, 7... Connection conductor, 8... Booster amplifier, SW... Switch.

Claims (1)

[Claims] 1. A printed wiring board for an antenna on which at least an antenna conductor, a booster amplifier for amplifying the received signal, and a tuning circuit for tuning to the received frequency are formed, and a third antenna conductor from different positions of the antenna conductor is located between the first and second antenna conductors. first, second, and third connection conductors arranged and drawn out such that the connection conductors are formed on the printed wiring board, the first connection conductor is connected to the first input, and the second a selection circuit that connects a connecting conductor to a second input, selects the received signal supplied to the first and second connecting conductors, and outputs the received signal between the third connecting conductor and the third connecting conductor; A booster amplifier is inserted between one input of the selection circuit and the first connection conductor, and the input of the booster amplifier is connected to the second connection conductor connected to the second input of the selection circuit. An antenna device characterized in that an oscillation phenomenon of a booster amplifier is prevented by connecting to a different first connection conductor.