JP2000183612A - Antenna system and communication unit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the antenna system that is made thin in profile where stability of an entire circuit is attained without deteriorating the overall gain. SOLUTION: An antenna 3 and an amplifier 4 that amplifies a signal received by the antenna 3 are mounted on the same board 2 and a phase shift circuit 11 to adjust a phase condition of a closed loop configured with the antenna 3, the amplifier 4 and a space is provided between the antenna 3 and the amplifier 4 to configure the antenna system 10. Thus, the circuit of the antenna system is made stable to reduce the deterioration in the overall gain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antenna device and a communication device using the same, and more particularly, to an antenna device used as a GPS antenna and a communication device using the same.

[0002]

2. Description of the Related Art For reception only, such as a GPS antenna,
2. Description of the Related Art In an antenna device often used separately from a receiver main body, an amplifier for amplifying a signal received by an antenna is often built in the antenna device.

FIG. 7 shows a conventional antenna device. FIG. 8 shows an equivalent circuit thereof. 7 and 8, the antenna device 1 has an antenna 3 and an amplifier 4 mounted on a substrate 2, and both are connected by a connection wiring 5. Here, the antenna 3 is a microstrip patch antenna, and a ground electrode (not shown) is formed on the back surface of the base 3a.
A substantially rectangular radiation electrode 3b is formed on the surface, and the radiation electrode 3b
A power supply line (not shown) penetrating through the base 3a from the back surface of the base 3a is connected to a part of the feed points 3c, and
Circularly polarized radio waves can be received. In addition, amplifier 4
Is composed of several individual components such as FETs, resistors and capacitors and distributed constant elements such as microstrip lines.

In the antenna device 1 configured as described above, the antenna 3 receives a circularly polarized wave transmitted from a GPS satellite or the like, and inputs the received signal to the amplifier 4. The amplifier 4 amplifies and outputs the input signal.

[0005]

However, in the antenna device 1 shown in FIGS. 7 and 8, the antenna 3 and the amplifier 4 are mounted on the same substrate 2 and are spatially close to each other. A phenomenon occurs in which the amplified signal leaks from the amplifier 4 as an electromagnetic wave s, and the antenna 3 receives the leaked signal. At this time, since the antenna 3 and the amplifier 4 are directly connected and are also connected via a space through which the electromagnetic wave s passes, a closed loop is formed. For this reason, feedback is applied from the amplifier 4 to the antenna 3, and the gain of the entire circuit of the antenna device 1 may decrease, become unstable, or in some cases, abnormal oscillation may occur.

More specifically, when the phase shift of the signal during one round of the closed loop is -90 degrees to 90 degrees, positive feedback occurs, the circuit becomes unstable, and abnormal oscillation easily occurs. Conversely, the phase shift is from -180 degrees to -90 degrees, or 90 degrees.
If the angle is 180 degrees to 180 degrees, negative feedback occurs and the circuit is stabilized. However, when the phase shift is around 180 degrees (-180 degrees), the signals cancel each other out, so that the total gain is greatly reduced.

On the other hand, measures to prevent the radiation of electromagnetic waves by covering the amplifier 4 with a shield case are conceivable, but it is difficult to completely shield the amplifier 4 and the cost of the antenna device is increased.

Further, it is conceivable to reduce the amount of feedback by mounting the antenna 3 and the amplifier 4 on another surface of the substrate 2. However, the thickness of the antenna device is increased, which hinders the thinning of the antenna device. Become.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an antenna device which can be made thinner and can stabilize the entire circuit without deteriorating the overall gain, and a communication device using the same.

[0010]

In order to solve the above-mentioned problems, an antenna device according to the present invention comprises an antenna and an amplifier for amplifying a signal received by the antenna mounted on the same substrate. A phase circuit is provided between the amplifiers for adjusting a phase condition of a closed loop formed by a signal leaking from the amplifier as an electromagnetic wave being received by the antenna.

[0011] A communication device according to the present invention is characterized by using the above-mentioned antenna device.

With this configuration, in the antenna device of the present invention, it is possible to stabilize the circuit and reduce the decrease in the overall gain.

Further, in the communication device of the present invention, the communication quality can be stabilized.

[0014]

FIG. 1 shows an embodiment of an antenna device according to the present invention. FIG. 2 shows an equivalent circuit thereof.
1 and 2, the same or equivalent parts as those in FIGS. 7 and 8 are denoted by the same reference numerals, and the description thereof will be omitted.

In the antenna device 10 shown in FIG.
A phase circuit 11 composed of a coaxial line is connected between the antenna 3 and the amplifier 4. Then, in a closed loop composed of the antenna 3, the phase circuit 11, the amplifier 4, and the space, the phase shift amount of the phase circuit 11 is set so that the phase shift satisfies the condition of negative feedback and the deterioration of the gain is small. Specifically, the length of the coaxial line is determined.

FIG. 3 shows the relationship between the length of the coaxial line of the antenna device 10 and the total gain (the gain of the antenna device 10 as a whole including the gain of the amplifier 4) in an experiment conducted by the present inventor. In FIG. 3, the horizontal axis represents frequency,
The vertical axis indicates the total gain. Also, characteristics a1, a2,
a3 and a4 are 0 mm (that is, the antenna 3 and the amplifier 4 are directly connected), 40 mm, and 90 m, respectively.
m and 110 mm are shown. In addition,
The antenna device at this time is designed to have a frequency band around 1575 MHz.

First, when the length of the coaxial line is set to 0 mm, as shown by a characteristic a1, the circuit has an unstable peak with a total gain around 1565 MHz. When the length of the coaxial line is 40 mm, the characteristic a
As shown in FIG. 2, the circuit is stable, but the phase of the closed loop is near 180 degrees, and the overall gain is reduced. When the length of the coaxial line is 90 mm, the circuit is stable and the overall gain is high near 1575 MHz, as shown by the characteristic a3. When the length of the coaxial line is 110 mm, the closed loop is in a positive feedback state as shown by the characteristic a4, and oscillates around 1575 MHz.

As described above, the phase circuit 11 is provided between the antenna 3 and the amplifier 4, and the phase circuit 11 is adjusted so that the phase of the closed loop formed by the antenna 3, the phase circuit 11, the amplifier 4 and the space is optimized. By adjusting the amount of phase shift, it is possible to stabilize the circuit of the antenna device and reduce the decrease in the overall gain.

The phase circuit in the antenna device according to the present invention is not limited to a circuit using a coaxial line.
4 and 5 show another embodiment of the phase circuit in the antenna device of the present invention.

In FIG. 4, the phase circuit 12 is formed by forming a microstrip line to a fixed length.
Thus, by configuring the phase circuit 12 with the microstrip line, the phase circuit 12 can be formed on the substrate 2 at the same time as the electrode pattern of the amplifier 4, and the phase circuit is provided with almost no increase in price. be able to. Further, when the dielectric constant of the substrate forming the microstrip line is high, a large wavelength shortening effect can be obtained, and the size of the phase circuit can be reduced. Further, the length of the microstrip line can be easily adjusted by shaving the electrode pattern, and the fine adjustment of the phase circuit 12 after the antenna device is assembled can be easily performed.

Next, in FIG. 5, the phase circuit 13 includes an inductance element L1 provided in series, and capacitance elements C1 and C2 provided in parallel on both sides thereof. In this way, by configuring the phase circuit 13 with the individual elements such as the inductance element and the capacitance element, the phase circuit 1
3 can be mounted, and an increase in mounting cost can be reduced. Moreover, by using an individual element as an element for the phase circuit 13, a large-value individual element can be used, and a large amount of phase shift can be obtained. In this case, compared to a coaxial line or a microstrip line, The area occupied by the phase circuit can be reduced, and the antenna device can be downsized.

In addition, any other phase circuit may be used as long as the phase can be shifted, such as a delay line on a chip.

In the above-described embodiment, a direct-feeding patch antenna is used as an antenna. It may be another type of antenna, such as the above antenna.

Further, the amplifier is not limited to the one using individual elements, and an IC may be used.

FIG. 6 shows an embodiment of the communication apparatus of the present invention. FIG. 6 is an example of a navigation system.

In FIG. 6, a communication device 20 is connected to an antenna device 10 of the present invention, a receiving unit 21 connected to the antenna device 10, a signal processing unit 22 connected to the receiving unit 21, and a signal processing unit 22, respectively. It comprises a map system 23, a display 24 and an interface unit 25. The antenna device 10 receives radio waves from a plurality of GPS satellites, and the receiving unit 21 extracts various signals from the radio waves. The signal processing unit 22 obtains the current position of the communication device 20 from the received signal, that is, the current position of the vehicle equipped with the communication device 20, and cooperates with a map system 23 equipped with map software such as a CD-ROM and an interface unit 25 such as a remote controller. Then, the map and the current position are displayed on the display 24.

As described above, when a navigation system as one of the communication devices is configured using the antenna device of the present invention, the total gain of the antenna device can be stabilized, and the communication quality can be stabilized.

[0028]

According to the antenna device of the present invention, the antenna and the amplifier for amplifying the signal received by the antenna are mounted on the same substrate, and the antenna and the amplifier are provided between the antenna and the amplifier.
By providing a phase circuit for adjusting the phase condition of the closed loop composed of the antenna, the amplifier, and the space,
It is possible to stabilize the circuit and reduce the decrease in overall gain.

In the communication device according to the present invention, the use of the above-described antenna device makes it possible to stabilize the communication quality.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an antenna device of the present invention.

FIG. 2 is an equivalent circuit diagram of the antenna device of FIG.

FIG. 3 is a diagram showing a relationship between the length of a phase circuit and the total gain in the antenna device of FIG. 1;

FIG. 4 is another embodiment of the phase circuit used in the antenna device of the present invention.

FIG. 5 is still another embodiment of the phase circuit used in the antenna device of the present invention.

FIG. 6 is a block diagram showing one embodiment of the communication device of the present invention.

FIG. 7 is a perspective view showing a conventional antenna device.

FIG. 8 is an equivalent circuit diagram of the antenna device of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 ... Substrate 3 ... Antenna 4 ... Amplifier 10 ... Antenna device 11, 12, 13 ... Phase circuit 20 ... Communication device s ... Electromagnetic wave L1 ... Inductance element C1, C2 ... Capacitance element

Claims (2)

[Claims] An antenna and an amplifier for amplifying a signal received by the antenna are mounted on the same substrate, and a signal leaking as an electromagnetic wave from the amplifier is received by the antenna between the antenna and the amplifier. An antenna device provided with a phase circuit for adjusting a phase condition of a closed loop formed by the antenna. 2. A communication device using the antenna device according to claim 1.