The majority of the week was spent understanding the individual blocks needed to build the spectrum analyzer as well as familiarizing ourselves with Labview.

 

VCO

The VCO was first tested by applying a DC voltage to the Vtune pin. The VCO outputted a signal with a constant frequency according to the voltage supplied to Vtune. Therefore, by using the calibration curve, the desired frequencies could be chosen. A ramp generator was then connected to Vtune which effectively swept a range of frequencies based on the offset and amplitude of the ramp.

 

RF Amplifier

The gain of the RF amplifier was tested by inputting a -40dB signal and measuring the output with a spectrum analyzer. This gain was recorded for future use.

 

Band-pass filters

The frequency response of the two band-pass filters was tested by utilizing the tracking generator of the spectrum analyzer. The frequency response provided some useful information on the bandwidth and gain of these two filters.

 

Mixer

The VCO was also tested with the Mixer and a 50 MHz signal. The 10.7 MHz band-pass filter was attached to the output in order to filter out the desired frequency. The Vtune pin of the VCO was then swept until the spectrum analyzer measured a signal from the output of the mixer. The mixer would produce two signals; one at a frequency of the sum of the two inputs and one at a frequency of the difference of the two inputs. Since the band-pass filter was connected to the output of the mixer, one of the two frequencies had to be within the filter’s range. By adjusting the settings of the various inputs, the tuning range of the VCO needed for this project was determined.

 

Peak detector

The peak detector was designed and built by implementing a high pass filter with a schottky diode. After the circuit was built, it was tested with a 10 MHz signal and the power limits of the peak detector was determined. The transfer function was also found by utilizing the tracking generator of the spectrum analyzer.

 

LabView Coding

To begin understanding the functionality of LabView, the group members working on software familiarized themselves with the platform by stepping through the starter tutorials online. Next, the team implemented the Ramp voltage output function to be later integrated with the VCO. In the upcoming week, the software functions will be expanded to allow user interface and processing of input signals from the hardware.