Microwave Range

[gauravbijlani]

I work as a Test Engineer and have been encountering a strange problem of lately.As the range of microwave is to be measured to be put into the report book,I need to test each microwaves outside and the range of the microwaves vary from 30 metres to 60 meters.

It has been broght to my notice that :

The simplest solution for you will be to create a moving target (a rotating cylinder or fan) at the opposite end of your test space and to turn this on and off remotely to simulate your target. The measurement is in terms of microvolts and it is assumed that anything above 45 microwave refers to 60 meters.

I havent been told why and in practacality,the time(morning,afternoon) of the experiments make the readings vary even on the same unit.

I check for the voltages on the gunn diode and observe the waveform on CRO.The microwave is designed to perform as a occupancy sensor and turn on/off the light accordingly.

I am not able to comprehend how the distance to voltage conversion is related to the microwave?If it is an effective way to measure the range,why are there fluctuations in the readings of the same unit ?

Is there a way which would mean less tests outside?The weather is not conducive to be outside.
Can anyone please help me with suggestions please?

I check for the volts coming out of the gunn diode and check it on CRO.The microwave is designed to be a occupancy sensor and it turns on/off the light with regards to the presence.

 

[stevez]

Several things come to mind but they might be trivial, relative to the changes you are seeing.

First - I'd look to see if temperature and humidity can affect your measurements. They do have some effect however I do not know if the differences are so small they cannot be detected - or if they are significant.

Second- are you sure that the power output of your transmitter is constant? Could the unit be warming or cooling - or possibly drifting in frequency?

Are there things in close proximity to your test gear that could affect the transmitter? It needs to see a relatively constant load - if not the output would be affected. At microwave frequencies even non-metal objects have an impact.

 

[gauravbijlani]

Several things come to mind but they might be trivial, relative to the changes you are seeing.

First - I'd look to see if temperature and humidity can affect your measurements. They do have some effect however I do not know if the differences are so small they cannot be detected - or if they are significant.


The readings are taken in the same room always.There is a window on one side,however,the window is always closed when taking the readings.I have noted that when it is sunny or cloudy,it does make a little difference to the readings around 0.2 microvolt difference depending on the time of the day.


Second- are you sure that the power output of your transmitter is constant? Could the unit be warming or cooling - or possibly drifting in frequency?

I usually take the reading as soon as the unit is on and then let it soak for 30 minutes and again take the readings.There is a heat sink so the temprature variations are negligible.


Are there things in close proximity to your test gear that could affect the transmitter? It needs to see a relatively constant load - if not the output would be affected. At microwave frequencies even non-metal objects have an impact

There is a window on one side and multimeter and dc power supply on the other side.However,the test gear is brought in front of other obstructions so I guess,they dont affect the readings.

I am a little perplexed besides,I want to know,if I can,an alternate method to test the range fo the microwaves without going outside.