10 GHz Microwave Link 10 GHz Microwave Link 10 GHz Microwave Link - - PowerPoint PPT Presentation

10 GHz Microwave Link 10 GHz Microwave Link 10 GHz Microwave Link 10 GHz Microwave Link

• Project Objectives

Project Objectives

• System Functionality

System Functionality

• Testing Procedures

Testing Procedures

• Cautions and Warnings

Cautions and Warnings

• Problems Encountered

Problems Encountered

• Recommendations

Recommendations

• Conclusion

Conclusion

PROJECT OBJECTIVES PROJECT OBJECTIVES PROJECT OBJECTIVES PROJECT OBJECTIVES

• Implement a 10 GHz Wireless

Implement a 10 GHz Wireless Communication Link Communication Link

• Test the functionality of the link

Test the functionality of the link

• Implement it in an 10 Mbps Ethernet

Implement it in an 10 Mbps Ethernet Network Network

SYSTEM FUNCTIONALITY SYSTEM FUNCTIONALITY SYSTEM FUNCTIONALITY SYSTEM FUNCTIONALITY

• System acts as a pair of wireless

System acts as a pair of wireless transceivers using Voltage Controlled transceivers using Voltage Controlled Oscillators (VCOs) Oscillators (VCOs)

• VCOs used are MACOM MA87728

VCOs used are MACOM MA87728-

• MO1

MO1 Gunnplexer Units Gunnplexer Units

• VCOs directly generate FM waves

VCOs directly generate FM waves while being controlled by DC voltages while being controlled by DC voltages

SYSTEM FUNCTIONALITY SYSTEM FUNCTIONALITY SYSTEM FUNCTIONALITY SYSTEM FUNCTIONALITY

• During transmission, VCO acts as an

During transmission, VCO acts as an FM carrier FM carrier

• During reception, VCO acts as a local

During reception, VCO acts as a local

• scillator
• scillator
• Both transmission and reception

Both transmission and reception cannot be done simultaneously cannot be done simultaneously

SIGNAL TRANSMISSION SIGNAL TRANSMISSION SIGNAL TRANSMISSION SIGNAL TRANSMISSION

• Before applying a modulating signal to

Before applying a modulating signal to the VCO, it must be made to be the VCO, it must be made to be compatible compatible

• For this application, level shifting and

For this application, level shifting and amplification must be performed amplification must be performed

• Signal is then transmitted out an X

Signal is then transmitted out an X-

• band waveguide opening

band waveguide opening

SIGNAL RECEPTION SIGNAL RECEPTION SIGNAL RECEPTION SIGNAL RECEPTION

• VCO acts as a local oscillator

VCO acts as a local oscillator

• Frequency of VCO must be 145 MHz

Frequency of VCO must be 145 MHz away from the frequency of the away from the frequency of the transmitter transmitter

• FM signal is thus mixed down to 145

FM signal is thus mixed down to 145 MHz MHz

SIGNAL RECEPTION SIGNAL RECEPTION SIGNAL RECEPTION SIGNAL RECEPTION

• To recover original signal, IF signal

To recover original signal, IF signal must be demodulated must be demodulated

• Since the carrier frequency is reduced

Since the carrier frequency is reduced to 145 MHz, standard FM circuit to 145 MHz, standard FM circuit components can be used components can be used

• Recovered signal must still be level

Recovered signal must still be level shifted and amplified to reverse what shifted and amplified to reverse what is done in transmission is done in transmission

VCO UNITS VCO UNITS VCO UNITS VCO UNITS

• Also called Gunnplexers

Also called Gunnplexers

• Consist of 3 diodes and a resonant

Consist of 3 diodes and a resonant cavity cavity

• Resonant cavity is where electric

Resonant cavity is where electric field is produced and emitted field is produced and emitted

VCO UNITS VCO UNITS VCO UNITS VCO UNITS

• Gunn diode creates carrier signal

Gunn diode creates carrier signal

• Varactor (PIN) diode takes in

Varactor (PIN) diode takes in modulating signal modulating signal

• Mixer (Schottky) diode produces

Mixer (Schottky) diode produces mixed down output using Gunn mixed down output using Gunn signal as local oscillator signal as local oscillator

ANTENNA DESIGN ANTENNA DESIGN ANTENNA DESIGN ANTENNA DESIGN

• Horn antennas are ideal for the

Horn antennas are ideal for the experiment experiment

• Reflector antennas could be

Reflector antennas could be interesting for increased range interesting for increased range

• Standard 10 dB horns used for initial

Standard 10 dB horns used for initial setup setup

ANTENNA DESIGN ANTENNA DESIGN ANTENNA DESIGN ANTENNA DESIGN

• A cutout of a 15 dB horn is provided

A cutout of a 15 dB horn is provided

• Has not been used as of yet

Has not been used as of yet

• Higher gain antennas could be

Higher gain antennas could be designed if need be designed if need be

ATTENUATION ATTENUATION ATTENUATION ATTENUATION CONSIDERATIONS CONSIDERATIONS CONSIDERATIONS CONSIDERATIONS

• It is desired to know how much

It is desired to know how much attenuation is needed over a given attenuation is needed over a given distance distance

• Knowing the gain of the antennas and

Knowing the gain of the antennas and the wavelength of the signal as well as the wavelength of the signal as well as the distance, attenuation can be the distance, attenuation can be determined determined

ATTENUATION ATTENUATION ATTENUATION ATTENUATION CONSIDERATIONS CONSIDERATIONS CONSIDERATIONS CONSIDERATIONS

• This is done using Friis free space

This is done using Friis free space transmission equation transmission equation

2

• r

t t r

r 4 λ G G P P       = π

ATTENUATION ATTENUATION ATTENUATION ATTENUATION CONSIDERATIONS CONSIDERATIONS CONSIDERATIONS CONSIDERATIONS

• For a distance of 100 meters, a

For a distance of 100 meters, a frequency of approximately 10 GHz frequency of approximately 10 GHz (wavelength is about 3cm) and 10 dB (wavelength is about 3cm) and 10 dB antennas on either end: antennas on either end:

• Friis says that the attenuation is 72.44

Friis says that the attenuation is 72.44 dB dB

TESTING PROCEDURES TESTING PROCEDURES TESTING PROCEDURES TESTING PROCEDURES

The project which we began came with The project which we began came with certain testing procedures. certain testing procedures. Our system differs from the original. Our system differs from the original. We therefore came up with some We therefore came up with some alternate testing methods which will alternate testing methods which will briefly be discussed. briefly be discussed.

Calibrating the Gunns Calibrating the Gunns Calibrating the Gunns Calibrating the Gunns

The The VCOs VCOs are the first component of the system that is are the first component of the system that is tested. tested. The transceiver modules are currently being repaired. The transceiver modules are currently being repaired. Upon return they should be calibrated. Upon return they should be calibrated. This is an extremely vulnerable part of the testing, This is an extremely vulnerable part of the testing, since the mixer diodes on the since the mixer diodes on the Gunns Gunns are very sensitive are very sensitive to shock, static charge etc. to shock, static charge etc. There is a certain procedure to this. However, There is a certain procedure to this. However, beforehand a test must be performed to ensure that beforehand a test must be performed to ensure that the Gunnplexers are in working order. the Gunnplexers are in working order.

Ensuring that the Mixer Ensuring that the Mixer Ensuring that the Mixer Ensuring that the Mixer Diodes are Functional Diodes are Functional Diodes are Functional Diodes are Functional

The detector diodes are very sensitive, and in The detector diodes are very sensitive, and in general they should not be closer than one general they should not be closer than one meter from one another. Diode readings meter from one another. Diode readings should be taken. should be taken. Specified measurements can then be Specified measurements can then be compared to designated values to see if the compared to designated values to see if the diodes are damaged and need to be replaced. diodes are damaged and need to be replaced.

Calibrating the Gunn Calibrating the Gunn Calibrating the Gunn Calibrating the Gunn Frequency Frequency Frequency Frequency

There are three methods to There are three methods to perform the Gunn calibration. perform the Gunn calibration. Any one of the three can be used. Any one of the three can be used.

Method 1 Method 1

Using a Spectrum Analyzer. Using a Spectrum Analyzer. Using a Spectrum Analyzer. Using a Spectrum Analyzer.

If one is available: If one is available: Using the microwave spectrum Using the microwave spectrum analyzer, the screw of the first analyzer, the screw of the first Gunnplexer is tuned to 10.323 GHz, and Gunnplexer is tuned to 10.323 GHz, and the other Gunnplexer is tuned to the other Gunnplexer is tuned to 10.178 GHz. 10.178 GHz.

Method 2 Method 2

Using an Oscilloscope Using an Oscilloscope Using an Oscilloscope Using an Oscilloscope

If a spectrum analyzer is not available to perform the If a spectrum analyzer is not available to perform the tests, calibration can be done in the following manner. tests, calibration can be done in the following manner. The two Gunnplexers are placed at least one meter The two Gunnplexers are placed at least one meter from one another with their apertures facing one from one another with their apertures facing one another. another. Using an oscilloscope, measurements are taken until Using an oscilloscope, measurements are taken until 145 MHz can be read off the mixer diode. A 10X probe 145 MHz can be read off the mixer diode. A 10X probe will work better at picking up a signal since it is a will work better at picking up a signal since it is a better match to the impedance of the Gunnplexers. better match to the impedance of the Gunnplexers.

Method 3 Method 3 Using a Voltmeter. Using a Voltmeter. Using a Voltmeter. Using a Voltmeter.

If a 145 MHz frequency generator can be If a 145 MHz frequency generator can be

• btained:
• btained:

the FSK demodulator circuitry should be the FSK demodulator circuitry should be aligned first. aligned first. The mixer diode is connected to the test The mixer diode is connected to the test point of the demodulator assembly. If all was point of the demodulator assembly. If all was done correctly to date, a zero volt reading done correctly to date, a zero volt reading across pins 4 & 5 of the chip indicates 145 across pins 4 & 5 of the chip indicates 145 MHz. MHz.

FSK Demodulator Calibration FSK Demodulator Calibration FSK Demodulator Calibration FSK Demodulator Calibration

The FSK demodulator is a circuit that takes in a 145 The FSK demodulator is a circuit that takes in a 145 MHz signal from the mixer diode of the Gunnplexer and MHz signal from the mixer diode of the Gunnplexer and extracts an amplified, level shifted version of the extracts an amplified, level shifted version of the desired Ethernet signal. desired Ethernet signal. Our circuit contains a fixed inductor. Thus we can only Our circuit contains a fixed inductor. Thus we can only verify that this circuit is working properly, unless the verify that this circuit is working properly, unless the inductor is changed for the tunable type inductor is changed for the tunable type There are several models of tunable inductors that we There are several models of tunable inductors that we found and have included in the project document. found and have included in the project document.

FSK Demodulator calibration FSK Demodulator calibration FSK Demodulator calibration FSK Demodulator calibration

A test signal emulating the Ethernet signal is A test signal emulating the Ethernet signal is needed needed Given the fact that the overall bandwidth of Given the fact that the overall bandwidth of the 145 MHz signal is 40 MHz and the fact the 145 MHz signal is 40 MHz and the fact that the carried signal is 10 MHz, the that the carried signal is 10 MHz, the sensitivity can be determined. sensitivity can be determined. This sensitivity is used to simulate a This sensitivity is used to simulate a modulated signal. modulated signal.

FSK Demodulator calibration FSK Demodulator calibration FSK Demodulator calibration FSK Demodulator calibration

A signal that is 10 MHz that has 500mV peak A signal that is 10 MHz that has 500mV peak to peak is taken as a test signal. to peak is taken as a test signal. It is passed to the two AUI input pins on the It is passed to the two AUI input pins on the FSK modulator circuit board. From the pin FSK modulator circuit board. From the pin that says that says “ “To Varactor To Varactor” ”, , It should be verified on an oscilloscope that It should be verified on an oscilloscope that the signal at that point is a level shifted, the signal at that point is a level shifted, amplified version of the original signal. amplified version of the original signal. Using a stand alone FM generator, this test Using a stand alone FM generator, this test signal is modulated on 145 MHz signal is modulated on 145 MHz

FSK Demodulator calibration FSK Demodulator calibration FSK Demodulator calibration FSK Demodulator calibration

On a spectrum analyzer the carrier should be centered On a spectrum analyzer the carrier should be centered at 145 MHz, with the lower end at 125 MHz and the at 145 MHz, with the lower end at 125 MHz and the upper end at 165 MHz. upper end at 165 MHz. The signal must be applied to the pin labeled The signal must be applied to the pin labeled “ “From From Mixer Mixer” ”. . The output of the FSK Demodulator circuit should be The output of the FSK Demodulator circuit should be tested on an oscilloscope. tested on an oscilloscope. If the original test signal reappears then the FSK If the original test signal reappears then the FSK Demodulator is working properly. Demodulator is working properly.

Modulation Using the Gunn Diodes Modulation Using the Gunn Diodes Modulation Using the Gunn Diodes Modulation Using the Gunn Diodes

If demodulation is not occurring as expected, the If demodulation is not occurring as expected, the inductor will have to be replaced with a tunable one inductor will have to be replaced with a tunable one The tunable inductor must be tuned until a 0V The tunable inductor must be tuned until a 0V difference across pins 4 & 5 of the MC13155 is difference across pins 4 & 5 of the MC13155 is reached. reached. If the circuits have covers, the cover of the circuit If the circuits have covers, the cover of the circuit board should be installed and it should be verified that board should be installed and it should be verified that the values don the values don’ ’t change with the cover on. t change with the cover on. If they do change, compensate the inductor If they do change, compensate the inductor accordingly. accordingly. This is similar to preloading the tank circuit with extra This is similar to preloading the tank circuit with extra inductance. inductance.

FSK Modulator Deviation Adjustment FSK Modulator Deviation Adjustment FSK Modulator Deviation Adjustment FSK Modulator Deviation Adjustment

The gain of the modulator is 3.6. This The gain of the modulator is 3.6. This can be verified by testing the peak to can be verified by testing the peak to peak output of a known input signal. peak output of a known input signal. This step has been completed but This step has been completed but should be repeated to be thorough. should be repeated to be thorough. Repeat the FSK modulation test with Repeat the FSK modulation test with an actual Ethernet signal once one is an actual Ethernet signal once one is available. available.

Enclosure of Power Supplies Enclosure of Power Supplies Enclosure of Power Supplies Enclosure of Power Supplies

Before any testing should be done, Before any testing should be done, metallic enclosures should be metallic enclosures should be purchased for the circuits. purchased for the circuits. These enclosures should not contain These enclosures should not contain free wires and there should be bypass free wires and there should be bypass capacitors at their entrance points to capacitors at their entrance points to block out any potential noise. block out any potential noise.

Finishing up Testing Finishing up Testing Finishing up Testing Finishing up Testing

Make sure any testing equipment needed is Make sure any testing equipment needed is promptly located and reserved promptly located and reserved The testing should be done with the The testing should be done with the confidence that a working system is confidence that a working system is ultimately going to be achieved. ultimately going to be achieved. As the link is connected the test stages As the link is connected the test stages should be repeated to ensure continuous should be repeated to ensure continuous functionality functionality

Cautions and Warnings Cautions and Warnings Cautions and Warnings Cautions and Warnings

Gunnplexers Gunnplexers Gunnplexers Gunnplexers

• Use appropriate voltage polarity (+8V

Use appropriate voltage polarity (+8V 10mW; 10mW; -

• 8V 100mW)

8V 100mW)

• Secure shorting strap between mixer

Secure shorting strap between mixer and ground when not in use and ground when not in use

• Avoid using waveguides as

Avoid using waveguides as transmitting medium transmitting medium

Cautions and Warnings Cautions and Warnings Cautions and Warnings Cautions and Warnings

Circuitry Circuitry Circuitry Circuitry

• If using polarized capacitors, verify

If using polarized capacitors, verify that they are installed correctly that they are installed correctly

• RF Amplifiers may be damaged from

RF Amplifiers may be damaged from when they were mounted. when they were mounted.

Problems Encountered Problems Encountered Problems Encountered Problems Encountered

Damaged Mixer Diodes Damaged Mixer Diodes Damaged Mixer Diodes Damaged Mixer Diodes

• Initial testing through an attenuated

Initial testing through an attenuated waveguide produced no results waveguide produced no results

• Diode tests on mixer diodes showed they

Diode tests on mixer diodes showed they had been damaged had been damaged

• Initial supplier of Gunnplexers could not

Initial supplier of Gunnplexers could not furnish replacement diodes furnish replacement diodes

• Found alternate MA

Found alternate MA-

• COM supplier

COM supplier

• Shipped Gunnplexers to be repaired

Shipped Gunnplexers to be repaired

Problems Encountered Problems Encountered Problems Encountered Problems Encountered

Lack of Test Equipment Lack of Test Equipment Lack of Test Equipment Lack of Test Equipment

• Basic lab equipment useless for RF

Basic lab equipment useless for RF

• Had trouble getting RF quality test equipment

Had trouble getting RF quality test equipment 10 MHz signal generator 10 MHz signal generator Functional FM signal generator Functional FM signal generator Oscilloscope with at least 145 MHz Oscilloscope with at least 145 MHz bandwidth bandwidth

• Received a Tektronix 300 MHz scope

Received a Tektronix 300 MHz scope

• Had to make a 10 MHz source using a crystal

Had to make a 10 MHz source using a crystal

Problems Encountered Problems Encountered Problems Encountered Problems Encountered

Components Mounted Incorrectly Components Mounted Incorrectly

• Testing of FSK Modulator section resulted in

Testing of FSK Modulator section resulted in smoking component smoking component Cause: Polarized capacitor mounted Cause: Polarized capacitor mounted backwards backwards

• Problem not isolated to this sub circuit

Problem not isolated to this sub circuit

Problems Encountered Problems Encountered Problems Encountered Problems Encountered

• Noise and RF Interference

Noise and RF Interference Noise and RF Interference Noise and RF Interference

• Initially hypothesized that PCB will attract

Initially hypothesized that PCB will attract noise noise

• Hypothesis proven to be true

Hypothesis proven to be true Ground plane picking up interference Ground plane picking up interference

• Presence of noise may disrupt signal

Presence of noise may disrupt signal Causing distortion of waveform Causing distortion of waveform Resulting in an unrecoverable signal Resulting in an unrecoverable signal

• Solution #1: Cut PCB’s and place in aluminum

Solution #1: Cut PCB’s and place in aluminum enclosures enclosures

• Solution #2: Restart design of circuitry

Solution #2: Restart design of circuitry implementation implementation

Problems Encountered Problems Encountered Problems Encountered Problems Encountered

Little Documentation on PCBs Little Documentation on PCBs Little Documentation on PCBs Little Documentation on PCBs

• No clear labels on any connector

No clear labels on any connector pads pads

Had trace through circuitry to Had trace through circuitry to determine proper connections determine proper connections Connector have been labeled with a Connector have been labeled with a permanent marker permanent marker

• No indication on the type of

No indication on the type of connectors to be used connectors to be used

Problems Encountered Problems Encountered Problems Encountered Problems Encountered

AUI Network Cards AUI Network Cards AUI Network Cards AUI Network Cards

• Difficult to find

Difficult to find

• One available in H

One available in H-

• 847

847

• May be able to find another one

May be able to find another one elsewhere in the school elsewhere in the school

PROJECT TIMELINE PROJECT TIMELINE PROJECT TIMELINE PROJECT TIMELINE

RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS

1. 1.

The two main PCB The two main PCB’ ’s should be made into the three smaller s should be made into the three smaller

• nes contained within it. After being cut they should be
• nes contained within it. After being cut they should be

mounted in a metal enclosure similar to Hammond Diecast mounted in a metal enclosure similar to Hammond Diecast Aluminum 1590 series enclosures. Aluminum 1590 series enclosures. Purpose? Purpose? Doing this would be to reduce noise picked up by the Doing this would be to reduce noise picked up by the

• system. Perhaps LEDs could be added to indicate that
• system. Perhaps LEDs could be added to indicate that

each voltage bus is on and working properly. each voltage bus is on and working properly.

RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS

2. 2.

The power supplies could be placed in an enclosure that The power supplies could be placed in an enclosure that has some form of ventilation to keep the regulators cool. has some form of ventilation to keep the regulators cool. Use cheaper plastic enclosures that are also available Use cheaper plastic enclosures that are also available from Hammond. from Hammond.

3. 3.

Decoupling capacitors should be added to all power Decoupling capacitors should be added to all power components both at the point where the power cable exits components both at the point where the power cable exits the power supply and where it enters any sealed box the power supply and where it enters any sealed box containing circuitry. containing circuitry. The decoupling capacitors on the sealed boxes would The decoupling capacitors on the sealed boxes would eliminate any potential RF noise that may enter the box eliminate any potential RF noise that may enter the box

RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS

4. 4.

Build horn antennas to the specifications that were Build horn antennas to the specifications that were presented in this report. If necessary modify the presented in this report. If necessary modify the design. design. A horn can be built with aluminum sheeting or an A horn can be built with aluminum sheeting or an easier way is to male it with cardboard and cover it easier way is to male it with cardboard and cover it in aluminum foil. in aluminum foil.

RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS

5. 5.

It would be a good idea to use reflectors to try to It would be a good idea to use reflectors to try to maximize range. Standard reflectors should be maximize range. Standard reflectors should be readily available. readily available. Horn antennas should thus be designed to act as Horn antennas should thus be designed to act as good feeds for the reflectors. This should take into good feeds for the reflectors. This should take into account the aperture of the reflector as well as its account the aperture of the reflector as well as its focal point focal point

RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS

6. 6.

The Gunnplexer The Gunnplexer’ ’s Gunn diode could be upgraded s Gunn diode could be upgraded from the 10 from the 10 mW mW to the 100 to the 100 mW mW model. This will

• model. This will

further increase the range of the system by further increase the range of the system by increasing the transmit power. increasing the transmit power. CAUTION should be taken to ensure that they are CAUTION should be taken to ensure that they are mounted properly, that is backwards, so that the mounted properly, that is backwards, so that the main connector will now require main connector will now require -

• 8V instead of +8V

8V instead of +8V

RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS RECOMMENDATIONS

7. 7.

All necessary test equipment discussed in this report All necessary test equipment discussed in this report should be requested as early as possible. should be requested as early as possible. This is to enable the department plenty of time to process This is to enable the department plenty of time to process and grant the request for any given equipment. Also, and grant the request for any given equipment. Also, should there be a problem; it could be dealt with earlier. should there be a problem; it could be dealt with earlier.

CONCLUSION CONCLUSION CONCLUSION CONCLUSION

Despite the fact that the microwave link system is not Despite the fact that the microwave link system is not complete, much progress has been made to it. No additional complete, much progress has been made to it. No additional hardware needs to be installed and, in theory, all the hardware needs to be installed and, in theory, all the necessary test equipment should be available. necessary test equipment should be available. If all goes well, very little work should need to be done to get If all goes well, very little work should need to be done to get the microwave link operational and, should anyone try to the microwave link operational and, should anyone try to pursue this project, the probability of them achieving pursue this project, the probability of them achieving success is relatively high. success is relatively high.

THANK YOU THANK YOU THANK YOU THANK YOU