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 � oscillator oscillator � 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 P λ = r o G G t r π P 4 r t
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 VCOs VCOs are the first component of the system that is are the first component of the system that is The 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 Gunns Gunns are very sensitive are very sensitive since the mixer diodes on the 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.
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