Ideal Response Simulated Response Measured Response Nathan Roth Advisors Dr. Brian Huggins Dr. Prasad Shastry Mr. James Jensen, Northrop Grumman Corporation Bradley University College of Engineering and Technology Department of Electrical and Computer Engineering D efinition F requency S ynthesizer: a device that is capable of generating many desired frequencies from a single or a few reference signal frequencies S pecifications: -Output Frequencies of 3650 MHz, 3700 MHz, 3850 MHz, 3900 MHz, 4450 MHz, 4500 MHz, 4650 MHz, and 4700 MHz - Output Power of 0 dBm, ± 3 dB - Output Spurs < -45 dBc (noise in the signal) - Transition Time < 500 ns, 200 ns if possible What Why F requency synthesizers are an integral part of any wireless system, including cellular phones. A cell phone must be able to operate on a variety of different channels, or frequency bands. It is a frequency synthesizer that allows this functionality. F requency synthesizers also are used in electronic warfare systems. Northrop Grumman Corporation will use the results of this project in defensive system application. Results T he figure to the left shows a detailed block diagram. There is a reference signal of 100 MHz. The digital input command will configure the switches to produce the desired output frequency. While appearing complex, it is composed of seven basic components: amplifiers, digital logic, filters, mixers, multipliers, prescalers, and switches. How A mplifiers make a signal bigger. M ixers add frequencies. The output is the sum and difference of the input frequencies, IF + LO and IF – LO. D igital Logic controls the switches. M ultipliers are like frequency multipliers. In this system, the output signal has a frequency two times that of the original. F ilters eliminate un- wanted signals. P rescalers are the opposite of multipliers – they divide the frequency. Here, the output signal will be one quarter of the original. S witches select the path for the signal to travel. Filter Simulated Center Frequency Measured Center Frequency Simulated Bandwidth Measured Bandwidth Filter MHz MHz120 MHz125 MHz Filter MHz977.5 MHz120 MHz115 MHz Filter MHz MHz195 MHz167 MHz Filter 4962 MHz932 MHz195 MHz220 MHz Filter MHz1181 MHz108 MHz112 MHz Filter 6982 MHz990.2 MHz202 MHz201 MHz A typical graphical filter response is shown above. The table below lists the results of the six band-pass filters. -10 dBm -50 dBm A contributing factor to the overall performance of the system is isolation, or how well the switch keeps a signal from leaking on to the path. In this system, the switch performs well, showing 40 dB of isolation A long with the sum and difference of the input signals, mixers also produce noise. In this case, the input signals are 1400 MHz and 200 MHz. Filters will eliminate every signal except for the 1200 MHz signal. S imilar to a mixer, the prescaler also produces noise. An input of 1200 MHz is shown to produce the desired 300 MHz signal, along with harmonic signals.