Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Distributive type parameters
Reexamination Certificate
1998-07-08
2001-11-06
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Distributive type parameters
C324S642000, C324S646000
Reexamination Certificate
active
06313644
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method for measuring a voltage standing wave ratio of an antenna of a base station, and more particularly to the apparatus and method for measuring the voltage standing wave ratio of a transferring terminal TX and a receiving terminal RX of the base station of a mobile communication, by using a base-station test unit for checking and testing the base station of the mobile communication.
2. Discussion of Related Art
In general, in the mobile communication system, it is an ideal that transmission output from the base station radiates in the air through a transmitting antenna. But the location of each base station, the surroundings and equipment installation conditions are different from each other, even though the same equipment is used, the efficiency in the transmission and reception of the base station is affected by the surroundings.
Thus, in order to make the base station perform at an optimal state, the state of the base station should be controlled in accordance with conditions around the base station and to minimize the minimize the effects of conditions by continuously monitoring the state of the base station.
The voltage standing wave ratio is used to check the state of the base station.
The standing wave is also called a stationary wave, which is generated by the combination of an incident wave from the signal source on the transmission line, and a reflected wave from the receiving terminal. The standing wave has a constant ratio of an order value between points of “A” and “B”, regardless of time, and ordinarily there are a lot of cases in which the amplitude of variation in the transmission is of the periodic function of the distance to the wave length direction.
Also, the standing wave ratio is of the amplitude to both anti node and wave node. If reflection coefficient is “&tgr;”, the SWR is defined as (1+&tgr;)/(1−&tgr;). Particularly, the SWR to a voltage is named VSWR, which is the ratio of the amplitude of voltage at the maximum point of the voltage caused around the waveguide, coaxial cable and transmission line at the minimum point adjacent thereto.
Accordingly, by measuring the SWR, each base station can check if the transmitting signals are efficiently well transmitted through an antenna connected to its transmission terminal. That is, it is determined whether the antenna and the transmission source are properly and efficiently matched. This means that each base station has to measure the above VSWR consistently and periodically.
In general, the large VSWR means that the transmission output at the base station doesn't radiate in the air, but returns to a transmission outlet of the system as much as the amount of mis-matching and has a bad effect on its transmission outlet.
Namely, the mismatching means that VSWR is so large that the quality and effectiveness of the system equipment is substantially degraded. Therefore, by measuring VSWR, the efficiency can be determined. Accordingly, each base station can control the loss of transmission in order to make good electrical matching between the different mediums and to make it possible to send voltage without any loss.
Also, even in case there is something wrong with a cable and antenna by the change of surrounding nearby, it triggers the big change of the VSWR so that each station can control its condition in a remote way.
The coupler is widely used as a tool for measuring the VSWR, which consists of an input terminal, a coupling terminal, an isolation terminal, and an output terminal.
The coupling terminal is where the signal inputted to the input terminal is outputted, after being attenuated as much as a fixed coupling coefficient C. The isolation terminal is where the signal inputted to the input terminal is theoretically held completely. But, in reality, there happens to be a little leaking named the isolation coefficient I. Also, the input terminal of the coupling can be used as an output terminal, which means the coupling terminal and the isolation terminal exchange their role. Namely, the terminal for generating an input signal from the input terminal is the coupling terminal and the opposite one to prevent output is the isolation terminal. The difference between the coupling coefficient C and the isolation coefficient is marked “D”.
So, the output terminal is where the signals inputted to the input terminal are generated, namely, the transmission signals are generated and decreased as much as the coupling coefficient of the coupling terminal and the isolation coefficient of the isolation terminal. For example, if the coupling coefficient is 30 dB and the isolation is perfect, 99.9% of the signals in the input terminal is transmitted. Namely, the coupling coefficient of 30 dB is {fraction (1/1000)}, about 0.1%, which means that 0.1% of the entire transmitted signals are generated to the coupling terminal and 99.9% is generated to the output terminal without any leak into the isolation terminal.
The equipment to measure VSWR of the output and input terminals at each base station according to the prior art will be explained in FIG.
1
.
The VSWR measuring equipment
15
of the prior art has a cellular or PCS station system
1
, a transmission coupler
10
having an input terminal
11
, a coupling terminal
12
, an isolation terminal
13
, and an output terminal
14
connected to the transmitting terminal of the base station
1
, a transmission voltage standing wave ratio
15
for measuring the voltage standing wave ratio of the transmitting terminal under connection to the coupling terminal
12
and the isolation terminal
13
of the transmission coupler
10
, and a transmitting antenna
16
connected to an output terminal of the transmission coupler
10
.
Also, as the combination of the VSWR measuring equipment
23
of the reception terminal, the reception coupler
20
connected with the reception terminal of the above station has the following 5 terminals, namely the input terminal
24
, a first coupling terminal
25
, a second coupling terminal
26
, an output terminal
27
, and isolation terminals
28
. The first coupling terminal
25
of the reception coupler
20
is coupled with the Phase Locked Loop
21
, the second coupling terminal
26
of the reception coupler
20
with the voltage standing wave ratio
23
of the receiving terminal, respectively.The input terminal
24
of the reception coupler
20
is coupled with the receiving antenna
22
, the output terminal
27
of the reception coupler
20
with the receiving terminal of the base station
1
, and the isolation terminal
28
with the voltage standing wave ratio
23
of the receiving terminal, respectively.
There will be explained an operation of the antenna of the base station VSWR measurement equipment as follows.
First, the measuring procedure of the VSWR on the transmission terminal is fully explained. The signal from the output terminal of the station system
1
is transmitted to the input terminal
11
of the transmitting coupler
10
, diminishes as much as coupling coefficient C and becomes an output X
1
, which is transmitted to the SWR measuring equipment
15
of the reception terminal.
Also, the signal of the above station inputted to the above transmitting coupler
10
is transmitted to the transmitting antenna
16
through the output terminal
14
. But, if the transmission terminal and transmitting antenna
16
of the base station
1
are not fully matched, all the signals transmitted to the above transmission antenna
16
will not radiate to the air and some transmitted signals are reflected due to the mis-matching. This reflected signal is applied to the output terminal
14
of the transmission coupler
10
and becomes the output X
2
through the isolation terminal
13
of the above transmission coupler
10
to thereby be applied to the transmission terminal VSWR equipments
15
which measure the ratio of the VSWR of the transmission terminal coupler comparing the values of outputs X
1
and X
2
.
There will b
Kim Bo Jong
Kim Dae Won
Kim Young Min
Brown Glenn W.
Fleshner & Kim LLP
LG Information & Communications Ltd.
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