JP2000284011A - Device for measuring antenna characteristic of moving terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for measuring the antenna characteristics of a moving terminal capable of accurately measuring an antenna received field without being affected by a measuring system by using a light converting device instead of a coaxial cable. SOLUTION: This device for measuring antenna characteristics is provided with a laser diode 13 (light output means) embedded in a moving terminal 1 for converting a received field by an antenna mounted to the moving terminal 1 into optical energy, a photo diode 14 (light receiving means) provided separately from the moving terminal 1 to receive optical energy from the laser diode 13 via an optical cable 10 and to convert it into high-frequency energy, and a measuring device 9 such as a spectrum analyzer to measure the received field of the moving terminal 1 on the basis of the output of the light receiving means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile terminal antenna characteristic measuring apparatus for measuring the reception characteristics of an antenna used for a mobile terminal such as a portable telephone.

[0002]

2. Description of the Related Art A mobile communication service such as a mobile phone system is installed at a fixed position for communicating with a mobile terminal housed in a small casing that can be freely carried by an individual via radio waves. Is performed with the base station. The communication path between the base station and the terminal is a radio wave propagation environment whose strength degrades purely in inverse proportion to the distance if there are no obstacles between them, especially in urban areas. There are large obstacles such as buildings that do not move, and relatively small obstacles that are always moving, such as trains and cars.Radio waves transmitted from base stations and terminals are complicated by these obstacles. Due to reflection, diffraction, and the like, a small change in the propagation environment called fading, which has a characteristic such that the intensity sometimes drops greatly, occurs.

[0003] In order to remedy the characteristic degradation due to the poor fluctuation of the propagation environment, there is a technique for receiving radio waves by a method called diversity reception. This is a concept in which radio waves are received by a plurality of antennas, the antenna having the highest received electric field strength is always selected, and a large drop in the received electric field is prevented as much as possible. This is implemented in both base station and terminal receivers.

FIG. 4 illustrates a conventional antenna characteristic measuring apparatus for a mobile terminal of this kind. As shown in FIG. 4A, two antennas are currently used for diversity reception actually performed in the mobile terminal 1. One is a whip antenna 2 which is a flexible rod-shaped antenna and is made to be able to be put in and out of the housing 3. The other is an inverted F antenna 4 made of sheet metal or the like, which is built in the housing 3. FIG.
5A shows a shield case 5.

[0005] In order to confirm the operation of the antenna of the mobile terminal 1 described above, it is necessary to measure how much diversity effect (gain) can be obtained under these fading environments. In addition, it is necessary to measure the directional characteristics of the antenna in free space such as an anechoic chamber and the absolute gain of the antenna itself as basic data.

As a simple method, as shown in FIG. 4B, a transmitting antenna 7 is placed in a free space such as an anechoic chamber 6.
And the mobile terminal 1 for receiving the transmission power from the transmitting antenna 7 is arranged, the coaxial cable 6 is directly connected to the antenna receiving end of the mobile terminal 1, and the coaxial cable 8 is guided to the outside of the anechoic chamber 6, There is a method in which a measuring instrument 9 such as a spectrum analyzer is connected to the other end of the coaxial cable 8 to directly measure an antenna reception electric field.

[0007]

However, in the above-described measurement shown in FIG. 4B, an antenna reception current is also induced in the coaxial cable 8, and this coaxial cable 8
There is a problem in that accurate antenna characteristics cannot be evaluated because antenna characteristics are different between the case where there is and the case where there is no antenna.

That is, as shown in FIG. 4B, the high-frequency energy transmitted from the transmitting antenna 7 is normally received by the antenna element and the housing of the mobile terminal 1, but in this case, It can be considered that the coaxial cable 8 also becomes a receiving antenna. For this reason, the antenna reception characteristics differ depending on whether or not the coaxial cable 8 is provided or how the coaxial cable 8 is routed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to measure an accurate antenna reception electric field without being affected by a measurement system by using an optical converter instead of a coaxial cable. It is an object of the present invention to provide an apparatus for measuring antenna characteristics of a mobile terminal capable of performing the following.

[0010]

In order to achieve the above object, an antenna characteristic measuring apparatus for a mobile terminal according to the present invention is built in the mobile terminal, and receives an electric field received by an antenna mounted on the mobile terminal. An optical output unit for converting the optical output into optical energy, and the mobile terminal is provided at a distance, the optical receiving unit for receiving the optical energy from the optical output unit via an optical cable and converting it to high-frequency energy, Measuring means for measuring a reception electric field of the mobile terminal based on an output of the light receiving means.

[0011] Further, the present invention is characterized in that light energy is transmitted through the optical space from the light output means to the light receiving means without using the optical cable.

Further, an optical measuring system comprising the optical output means, the optical cable and the optical receiving means is provided with a number of systems corresponding to the number of antennas mounted on the mobile terminal, and the measuring means comprises a plurality of antennas. The diversity gain is measured.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an antenna reception electric field is converted into light by a laser diode, and the reception energy is output by an optical cable made of a material (plastic) which does not affect the antenna induced current. By converting the received power to high-frequency energy again by the photodiode and measuring the received power, accurate measurement of antenna characteristics is realized.

To the extent that antenna directional characteristics are measured, a VCO (Voltage Controlled Oscillator) is built in the housing of the mobile terminal using the reversibility of the antenna (transmission characteristics and reception characteristics are the same). Although it is easy to evaluate the transmission characteristics, there is no simpler method than the present invention, especially when the reception characteristics such as the measurement of the characteristics of the reception diversity antenna must be evaluated.

First embodiment. Hereinafter, specific embodiments will be described. FIG. 1 is a diagram illustrating an apparatus for measuring antenna characteristics of a mobile terminal according to a first embodiment. FIG. 1A is a schematic diagram thereof, and FIG. 1B is a block diagram of a specific measurement system.

As shown in FIGS. 1 (a) and 1 (b), the antenna reception electric field received by the reception antenna 11 of the mobile terminal 1 is affected by the plasticity of the optical cable 10 routed from the housing. The light is input to the photodiode 14 as the light receiving means without receiving the light.

Normally, an LNA (Low Noise Amplifier) is provided between the receiving antenna 11 and the laser diode 13 as an optical output means in order to expand the measurement dynamic range of the reception electric field and improve NF (Noise Figure). 12 is inserted. This also means that the loss due to light conversion is compensated for.

After being converted into light energy, it is input via an optical cable 10 to a photodiode 14 located at a sufficiently distant position. Here, it is converted into a high-frequency current according to the light intensity. Usually, after this, the LNA for amplification
Are arranged to provide high-frequency energy output. This high-frequency energy is input to a measuring instrument 9 such as a spectrum analyzer in the same manner as in the conventional example, and measurement according to the antenna reception electric field becomes possible.

By measuring with such a measuring system,
It is possible to evaluate an accurate antenna reception electric field without being affected by a measurement cable as compared with the related art.

Second embodiment. Next, FIG. 3 shows a second embodiment, in which the optical cable portion in the first embodiment is eliminated and optical space transmission is performed by infrared rays or the like. In this case, since the optical transmission device often cannot use a high frequency, the antenna receiving electric field is detected by the detector 15 in the mobile terminal 1 and A / D converted, and then the optical output device 16 is used.
In this case, the light is transmitted in an optical space by infrared rays or the like and transmitted. On the receiving side, after receiving by the optical receiver 17, D / A
By converting and measuring the DC voltage level with a digital oscilloscope or the like, the antenna reception electric field can be known. If the data is input to a D / A board built in the personal computer after the reception, the data can be directly processed by the personal computer.

Third Embodiment Next, FIG.
(B) shows an example of the diversity antenna of the mobile terminal 1. This is a flexible rod-shaped antenna called a whip antenna 2 as explained in the conventional example.
It is made so that it can be put in and out of the housing. The other is an antenna called an inverted F antenna 4 made of sheet metal or the like, which is built in a housing.

In order to measure these two antenna reception electric fields simultaneously, the mobile terminal 1 is provided with the laser diode 13 and the LN as the light output means described in the first embodiment.
A12 is built in two systems. The optical cable 10 after this,
A photodiode 14 as an optical receiving means and a measuring device 9 such as a spectrum analyzer are also used in two systems.
The reception electric fields of the two antennas are measured simultaneously. Then, by processing these two measurement data with a measurement device 9 such as a spectrum analyzer,
It is possible to easily calculate the diversity gain.
It should be noted that the case where there are three or more receiving antennas can also be handled by increasing the number of measurement systems.

[0023]

As described above, according to the present invention, since a plastic optical cable is routed from a mobile terminal instead of a coaxial cable, there is no effect on an antenna reception electric field, and pure antenna characteristics are evaluated. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram and a block diagram illustrating an apparatus for measuring antenna characteristics of a mobile terminal according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an apparatus for measuring antenna characteristics of a mobile terminal according to a second embodiment of the present invention;

FIG. 3 is a schematic diagram and a block diagram illustrating an apparatus for measuring antenna characteristics of a mobile terminal according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a conventional diversity antenna and how the antenna is received by a coaxial cable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mobile terminal 2 Whip antenna 4 Inverted F antenna 9 Measuring device (measuring means) such as spectrum analyzer 10 Optical cable 13 Laser diode (optical output means) 14 Photodiode (optical receiving means) 16 Optical output device (optical output means) 17 Optical receiving device (optical receiving means)

Claims (3)

[Claims] An optical output means for converting an electric field received by an antenna mounted on the mobile terminal into light energy, the optical output means being provided in the mobile terminal, the mobile terminal being provided at a distance from the mobile terminal; Light receiving means for receiving light energy from the light output means via an optical cable and converting it to high-frequency energy; andmeasuring means for measuring a reception electric field of the mobile terminal based on an output of the light receiving means. An antenna characteristic measuring device for a mobile terminal. 2. The apparatus for measuring antenna characteristics of a mobile terminal according to claim 1, wherein optical energy is transmitted from said optical output means to said optical receiving means in space without using said optical cable. A mobile terminal antenna characteristic measuring device. 3. The antenna characteristic measuring apparatus for a mobile terminal according to claim 1, wherein an optical measurement system comprising said optical output means, said optical cable and said optical receiving means is mounted on said mobile terminal. Wherein the measuring means measures the diversity gain of a plurality of antennas.