Self-checking circuit in microwave equipment

A self-checking circuit in a microwave equipment comprising: directional couplers each for separating and extracting a portion of a microwave signal from each monitoring point on a microwave main signal path; detectors each for detecting an extracted signal from the directional coupler; multiple temperature measuring means each for measuring temperature of the detector; multiple amplifying means each for amplifying a detected signal from the detector; multiple analog/digital converting means each for converting an output signal of the amplifying means into digital data; an interface for performing interface with an outside with respect to the signal of the temperature measuring means and the digital data of the analog/digital converting means; first storage means for storing signal values transmitted through the interface; second storage means for storing a control program and various data; a central processing circuit for comparing and analyzing the signals stored in the first storage means using the control program and data stored in the second storage means and outputting a result of the comparison and analysis; and means for displaying an output signal of the central processing circuit.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a self-checking circuit for accurately 
detecting a component having an error in a microwave equipment and, more 
particularly, to a self-checking circuit for accurately measuring electric 
power of a relevant microwave equipment by compensating for 
characteristics of each detector changing according to temperature and 
displaying degrees of the electric power of microwave signals allowing 
close observance in the microwave equipment, thereby making it easy to 
check, maintain, and repair the system. 
2. Discussion of Related Art 
Generally, a microwave equipment uses a wave guide and coaxial line as a 
signal transmission line. The wave guide is disturbed in its function by 
change in its form caused by shock from outside or introduction of foreign 
substances or by change in environment such as pressure and temperature. 
For the coaxial line, the function may not be done well due to 
superannuation or breaking of a wire. These may influence other components 
which are normally operating. In this case, it is difficult to determine 
with the naked eye what components lose their functions in the overall 
circuit, so periodical check using a function measuring equipment is 
needed. Therefore, checking circuits should be installed at every 
important monitoring point on a signal transmission path of the microwave 
equipment to check whether each component operates in normal in the 
system. 
FIG. 1 shows an embodiment of a conventional self-checking circuit 
installed at one of multiple monitoring points on a microwave main signal 
path. The conventional self-checking circuit comprises: a directional 
coupler 7 for separating and extracting a portion of a microwave signal 
passing through the microwave main signal path; a detector 1 for 
converting the portion of the microwave signal separated and extracted by 
the directional coupler 7 into a low frequency signal using an envelop 
detection method; an amplifier 2 for amplifying a signal, which is 
detected by the detector 1 and has weak electric power, to produce a 
signal having a predetermined electric power level; a comparing unit 3 for 
comparing the electric power of a signal amplified by the amplifier 2 with 
a predetermined value and producing a result value of the comparison; an 
interface 5 for receiving the result signal from the comparing unit 3 and 
identifying a location of a checked component; and a display 4 for visibly 
displaying a signal outputted by the interface 5. 
With reference to FIGS. 1 and 2, operation of the conventional circuit 
having such configuration explained above will now be described in detail. 
FIG. 2 shows a detailed configuration of a detecting unit 10 according to 
the prior art. 
The directional coupler 7 is connected to a monitoring point to be checked 
on the microwave main signal path, and an output signal of the directional 
coupler 7 is applied to the detection unit 10 consisting of the detector 
1, amplifier 2, and comparing unit 3. 
In this case, a portion of the microwave signal passing through the 
monitoring point to be checked on the microwave main signal path is 
separated and extracted by the directional coupler 7. 
The extracted portion of the microwave signal received from the directional 
coupler 7 is detected through the envelop detection method by the detector 
1, thus removing a high frequency portion from the microwave signal and 
detecting a low frequency signal. 
The low frequency signal outputted from the detector 1 has very weak 
electric power. The amplifier 2 amplifies a level of the low frequency 
signal up to a predetermined power level and applies a result signal of 
the amplifier 2 to the comparing unit 3. 
The comparing unit 3 compares the level of the signal, which becomes to 
have sufficient electric power through the amplifier 2, with a reference 
value which has previously been set therein and applies a result value of 
the comparing unit 3 to the interface 5 in a processing unit 20. 
The interface 5 transmits the result value from the comparing unit 3 to the 
display 4. The display 4 displays normality or abnormality based upon the 
result value. 
With reference to FIG. 2, the comparing unit 3 which determines 
normality/abnormality of the monitoring point will now be described in 
detail. 
The comparing unit 3 comprises a comparator 8 and a variable resistor 6. 
The variable resistor 6 coupled to one terminal of the comparator 8 is 
grounded and sets the reference value, or a threshold level. Consequently, 
a signal which has been amplified by the amplifier 2 and then applied to 
the other terminal of the comparator 8 is recognized as a signal of higher 
or lower level than the threshold level set by the variable resistor 6. 
However, such electric power measuring circuit of the conventional 
microwave equipment just outputs "GOOD" or "FAIL" as a result of comparing 
the electric power of a detected signal from the amplifier 2 with a 
predetermined value. Change in inner temperature of the microwave 
equipment results in a change in an output value of the detector since the 
detector is very sensitive to the temperature. Consequently, abnormality 
may be displayed even though, actually, the equipment operates in normal. 
In this regard, the conventional self-checking circuit of the microwave 
equipment can detects an error only when a component concerned in the 
microwave equipment is completely out of order instead of previously 
detecting and predicting deterioration of the performance of the overall 
system caused by deterioration of the performance of each component. This 
makes it difficult to repair or replace a component which may be a major 
cause that a lifetime of the overall microwave equipment is reduced. 
On the other hand, there is a problem in that a good component without 
malfunction may be replaced. 
In addition, since this conventional circuit just determines "GOOD" or 
"FAIL", a special microwave electric power measuring equipment is required 
when the system is checked, maintained and repaired to prevent the 
deterioration of the performance of the system. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention is directed to a self-checking circuit 
in a microwave equipment that substantially obviates one or more of the 
limitations and disadvantages of the related art. 
An object of the present invention is to provide a self-checking circuit 
which can be fixedly installed within a microwave equipment, for easily 
measuring electric power of a microwave signal passing through a microwave 
main signal path at any time without a separate microwave electric power 
measuring equipment, accurately measuring actual electric power of a 
relevant microwave equipment by compensating for characteristics of a 
detector changing according to a temperature, and displaying degree of the 
electric power of the microwave signal concerned, allowing close 
observance in the microwave equipment, thereby making it easy to check, 
maintain, and repair the system. 
Additional features and advantages of the invention will be set forth in 
the description which follows, and in part will be apparent from the 
description, or may be learned by practice of the invention. The 
objectives and other advantages of the invention will be realized and 
attained by the structure as illustrated in the written description and 
claims thereof, as well as the appended drawings. 
To achieve these and other advantages, and in accordance with the purpose 
of the present invention as embodied and broadly described, the 
self-checking circuit in a microwave equipment includes: directional 
couplers installed at each monitoring point on a microwave main signal 
path, each, for separating and extracting a portion of a microwave signal; 
detectors each for converting the separated and extracted portion of the 
microwave signal into a low frequency signal using an envelop detection 
method; temperature measuring units each for measuring temperature of the 
microwave equipment and applying a result signal of measurement to an 
interface; amplifying units each for amplifying a signal, which is 
detected by the detector and has weak electric power, to produce a signal 
of a predetermined electric power level; analog/digital converting units 
each for converting an analog signal amplified by the amplifying unit into 
a digital signal; an interface for adding a unique number of a relevant 
monitoring point to both the signal from the temperature measuring unit 
and the signal outputted from the analog/digital converting unit and 
interfacing with an outer processing unit; a RAM which is a first storage 
device for storing signal values transmitted through the interface; a FOM 
which is a second storage device for storing temperature characteristics 
and electrical characteristics of each detector, gains of each amplifying 
unit, values of change of each signal, correlation between multiple 
monitoring points in their locations, priority and weight of importance of 
each monitoring point, and data and a program which a central processing 
circuit operates according to; a central processing circuit for searching 
various necessary data in the ROM based upon the values of the signals 
stored in the RAM and runs a control program, thus generating display 
control signals according to a result of execution of the program; and a 
display for displaying operational status of the system according to the 
display control signals received from the central processing circuit. 
It is to be understood that both the foregoing general description and the 
following detailed description are exemplary and explanatory and are 
intended to provide further explanation of the invention as claimed.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Reference will now be made in detail to the preferred embodiments of the 
present invention, examples of which are illustrated in the accompanying 
drawings. 
With reference to the accompanying drawings, the present invention will now 
be described in detail. 
The self-checking circuit in a microwave equipment according to the present 
invention comprises: a directional coupler 109 installed at each 
monitoring point on a microwave main signal path, for separating and 
extracting a portion of a microwave signal; a detector 101 for converting 
the separated and extracted portion of the microwave signal into a low 
frequency signal using an envelop detection method; a temperature 
measuring unit 110 for measuring temperature of the microwave equipment 
and applying a result signal of measurement to an interface 104; an 
amplifying unit 102 for amplifying a signal, which is detected by the 
detector 101 and has weak electric power, to produce a signal of a 
predetermined electric power level; an analog/digital converting unit 103 
for converting an analog signal amplified by the amplifying unit 102 into 
a digital signal; an interface 104 for adding a unique number of a 
relevant monitoring point to both the signal from the temperature 
measuring unit 110 and the signal outputted from the analog/digital 
converting unit 103 and interfacing with an outer processing unit 120; and 
the processing unit 120 for processing and displaying the digital signals 
transmitted from the interface 104. 
The temperature measuring unit 110 includes a temperature sensor 111, an 
amplifier 112, and an analog/digital converter 114. The temperature 
measuring unit 110 measures the ambient temperature of a monitoring point 
concerned, converts a result signal of the measurement into a digital 
signal, and applies the digital signal to the interface 104. 
The processing unit 120 comprises a ROM 106, a central processing circuit 
107, a RAM 105, and a display 108. This processing unit 120 is installed 
within the microwave equipment and has a function of processing and 
displaying digitalized data and unique identifications generated from each 
monitoring point. 
The RAM 105, which is a first storage device, stores each digital signal 
into which a low frequency signal separated and extracted from a microwave 
signal at each monitoring point is converted and each measured value of 
temperature, these digital signal and measured temperature value are 
transmitted from the interface 104. 
The ROM 106, which is a second storage device, stores temperature 
characteristics and electrical characteristics of each monitoring point 
and detector 101, gains of each amplifying unit 102, highest and lowest 
limitations of electric power of each monitoring point, correlation 
between multiple monitoring points in their locations, priority and weight 
of importance of each monitoring point, and data and a program which the 
central processing circuit 107 operates according to. 
The central processing circuit 107 searches various necessary data in the 
ROM 106 based upon the values of the signals stored in the RAM 105 and 
runs a control program, thus analyzing characteristics of microwave 
signals at each monitoring point and generating operation control signals 
according to results of the analysis. 
The display 108 visibly displays operation status of the system according 
to display control signals received from the central processing circuit 
107. 
Operation and effect of the present invention will now be described in 
detail with reference to FIGS. 3 and 4. 
Each directional coupler 109 is connected to each monitoring point on a 
microwave main signal path. The directional coupler 109 separates and 
extracts a portion of a microwave signal. 
The detector 101 converts the extracted signal into a low frequency signal 
using the envelop detection method. 
In the temperature measuring unit 110, the temperature sensor 111 detects 
ambient temperature by electrically of the detector 101, the amplifier 112 
amplifies the electrically detected level of the temperature, and the 
analog/digital converter 114 converts the amplified analog signal into a 
digital signal. The digital data on the ambient temperature of the 
detector 101 is applied to the interface 104. 
The low frequency signal detected at the detector 101 has an electric power 
level which is too weak to be use. The amplifying unit 102 amplifies the 
low frequency signal to make a signal of a predetermined electric power 
level, before applying it to the analog/digital converting unit 103. 
The analog/digital converting unit 103 converts the low frequency signal 
amplified by the amplifying unit 102 into a corresponding digital signal 
and applies it to the interface 104. 
The interface 104 adds a unique identification number of the relevant 
monitoring point to both the signal from the temperature measuring unit 
110 and the signal from the analog/digital converting unit 103, before 
applying them to the central processing circuit 107 in the processing unit 
120. 
The central processing circuit 107 searches the necessary control program 
and various data in the ROM 106 and analyzes the characteristics of the 
microwave signal of the relevant monitoring point based upon the values of 
signals extracted at each monitoring point and each ambient temperature 
detection signal value transmitted via each interface 104 to and stored in 
the RAM 105, and then compensates for a change in an output of the 
detector 101 of which the operational characteristic changes according to 
its ambient temperature. 
As a result of the compensation, a display control signal is generated and 
operational status of the system is displayed through the display 108. 
A control program necessary for the displaying operation is also stored in 
the ROM 106. 
The program allows to show change of each monitoring point to be checked 
through the display or to generate or display an alarm for malfunction 
when the change exceeds limits which have been previously set for smooth 
operation of the microwave equipment. 
In other words, the central processing circuit 107 performs the function of 
the conventional comparing unit 3 and compensates for characteristics of 
each detector 101 of which the output changes according to the 
temperature, thereby making it possible to measure a real value of a 
signal level of the microwave main signal path and display a signal level 
detected from a relevant monitoring point in linear instead of displaying 
it as "GOOD" or "FAIL" in binary. 
Accordingly, the present invention accurately determines whether the 
microwave equipment operates normally or abnormally and previously 
recognizes the deterioration of the performance or malfunction, thus 
making it easy to check, maintain, and repair the system to establish 
optimum performance in the system. 
Additionally, since the present invention displays the detected signal 
level linearly, a special microwave electric power measuring equipment is 
not needed. 
Such measuring method using the present invention comprises the steps of: 
separating and extracting a portion of a microwave signal at a monitoring 
point on a microwave main signal path using the directional coupler 109; 
detecting the extracted signal using the detector 101; measuring ambient 
temperature of the detector 101 using the temperature measuring unit 110; 
converting an output signal of the amplifying unit 102 into digital data 
using the analog/digital converting unit 103; performing interface with an 
outside with respect to the signal from the temperature measuring unit 110 
and the signal from the analog/digital converting unit 103 using the 
interface 104; storing signal values transmitted through the interface 104 
in the first storage device 105; storing a control program and various 
data necessary for checking the microwave equipment in the second storage 
device 106; comparing and analyzing the signals stored in the first 
storage device 105 using the control program and data stored in the second 
storage device 106 and producing a result value of the comparison and 
analysis using the central processing circuit 107; and displaying the 
result value outputted from the central processing circuit 107 using the 
display 108. 
The method will now be described in detail much more with reference to FIG. 
5. 
Measured electric power values and temperatures at every monitoring point 
from the first one to the last one are read from the first storage device, 
RAM 105, based upon unique identifications of each monitoring point (S51 
and S52). 
The temperature characteristics and electrical characteristics of each 
detector 101 at each monitoring point, gains of each amplifying unit 102, 
and the highest and lowest limit values of the set electric power at each 
monitoring point are read and a testing result with respect to electric 
power values measured at each monitoring point is previously set to "FAIL" 
(S53) 
Each electric power value at each monitoring point is compensated for a 
temperature characteristic and electrical characteristic of a relevant 
detector 101 and for a gain of a relevant amplifying unit 102. Therefore, 
the measured electric power values at every monitoring point are adjusted 
to compensated new values (S54). 
Each compensated new value is compensated for the corresponding temperature 
value read at the step S52 (S55). 
Through compensation for the ambient temperature of the equipment, 
temperature characteristic and electrical characteristic of the detector 
101, and gain of the amplifying unit 102, the measured electric power 
value at the relevant monitoring point is replaced with a real value which 
is actually desired to be measured. 
Whether or not to display the compensated electric power values of each 
monitoring point is determined (S56). 
If it is decided to display the value, a corresponding unique 
identification (ID) of the relevant monitoring point is inputted (S57) and 
the compensated real electric power value of the corresponding monitoring 
point is outputted to a monitor or a printer with its unique ID in linear 
(s58). 
If it is determined that the electric power value is not displayed at the 
step S56, an ID of a monitoring point is set to the unique ID number of 
the first monitoring point (S59) 
Whether or not the electric power value corresponding to the unique ID 
exceeds the highest limit value is determined (S60). If the electric power 
value does not exceed the highest limit value, whether or not the electric 
power value is less than the lowest limit value is determined (S61). If 
the electric power value is not less than the lowest limit value, a test 
result is established as "GOOD" (S62), and 1 is added to the unique ID 
number of the monitoring point (S63). 
If the electric power value exceeds the highest limit value at the step S60 
or is less than the lowest limit value at the step S61, the test result is 
established as "FAIL" (S64). 1 is added to the unique ID of the monitoring 
point which is under the test in present and test results with respect to 
all the monitoring points hereafter are set to "GOOD" (S65). 
If the ID of a monitoring point established at the step S65 is less than 
the last ID number, the procedure goes back: to the step S60 (S66). 
Otherwise, the ID of a monitoring point is set to the unique ID number of 
the first monitoring point (S67). The unique ID, weight of importance, 
test result, and electric power value of the corresponding monitoring 
point are outputted to the monitor or printer (S68). 
1 is added to the unique ID (S69), and whether or not the ID corresponds to 
that of the last monitoring point (S70). 
If the ID is not the last one, the procedure goes back to the step S68. If 
the ID number exceeds the last one, whether or not to perform a retest is 
determined (S71). 
If the test is determined not to be performed any more, the procedure ends. 
To continue the test, the procedure goes back to the step S51. 
In the microwave equipment which has a single signal path and where each 
component on the path is established as a monitoring point, the present 
invention measures electric power values of each monitoring point and 
determines the correlation between multiple monitoring points in their 
locations and priority and weight of importance of each monitoring point 
using a program, thereby easily finding a component causing the 
deterioration of the performance or malfunction in the microwave 
equipment. 
In case where there are multiple microwave equipments and they are distant 
from each other, the interface 104 may be made having a function of remote 
data communication and the central processing circuit 107, ROM 106, and 
RAM 105 in the processing unit 120 may be replaced with a personal 
computer or the like equipment having performance above that of the 
personal computer. In addition, the substitute equipment such as the 
personal computer may be fixedly coupled to one of the self-checking 
circuits of the multiple microwave equipments. Consequently, the interface 
104 can be used as a remote measuring circuit by making it have the remote 
data communication function. 
When an equipment uses a signal of a microwave frequency band, any 
embodiment of the present invention can be applied to the equipment. 
Accordingly, the present invention easily measures an electric power of a 
microwave signal which is compensated for the temperature characteristic 
of a monitoring point at any time and easily finds a component causing 
deterioration of the performance and malfunction of the system through an 
internally installed microwave electric power measuring apparatus, thereby 
facilitating check, maintenance, and repair of the microwave equipment. 
Additionally, since the present invention shows the electric power level of 
the microwave signal in detail through the display, allowing direct 
judgement on the status of the performance of the microwave equipment, and 
compensates for the change of temperature, allowing accurate measurement 
of a real value of a signal level. 
It will be apparent to those skilled in the art that various modifications 
and variations can be made in a self-checking circuit in a microwave 
equipment of the present invention without deviating from the spirit or 
scope of the invention. Thus, it is intended that the present invention 
cover the modifications and variations of this invention provided they 
come within the scope of the appended claims and their equivalents.