Usable Scripts 

Frequency Response for BPF

Purpose:  varying RF input frequency & LO frequency (1kHz offset between them) to measure frequency response of BPF. system amplitude of I & Q outputs are proportional to the frequency response of the filter

Variables:

• "freq" stores a vector of frequency points to be tested;

• "offset" controls the offset between the RF and LO signal frequencies, with the RF frequency being the LO frequency plus the offset; and

• "input_ampl" controls the amplitude of wave generator used to excite the RF_SIG port of Subsystem A. (default: 50 mVpp)

Operation:

• The signals fill as much of the vertical scale as possible, for maximum resolution;

• The signals are not clipped; and

• The scope is triggering cleanly on the signal.

Output:

• "bpf.png" : overall conversion gain (dB) as a function of frequency

• "bpf.txt": raw data (frequency, I - amplitude, Q -amplitude)

 Frequency Response LPF

Purpose:

This script measures the frequency response of the lowpass filter succeeding the mixer. It does so by varying the RF input frequency while keeping the LO frequency constant. The RF frequency is sinusoid whose frequency is equal to 14 MHz plus the a low-frequency equal to that of a sinusoidal message signal, which effectively generates an upper sideband RF input signal at the output of the oscilloscope’s function generator. In this way, the amplitudes of the I and Q outputs of Subsystem A are proportional to the frequency response of the filter.

Variables:

Output:

Output Power & FFT

This script carries out various tests on the power amplifier and lowpass filter. It does so by exciting the PA with a fixed-amplitude sinusoidal signal. The amplitude of this signal is controlled by a single variable, drive_amplitude, within the script. It should nominally be set to 1.0 (since the ICD specified the input signal must be 1.0 Vpp), but you can override this if you find your subsystem needs a large amplitude signal in order to work.

The script first measures the current consumption of Subsystem E in the idle and active stages (i.e. with no signal and a 14 MHz signal applied to the input of the PA). From this point, you can change the input frequency if you wish (either from the front panel, or permanently, by modifying the script).

It then conducts an FFT analysis with that signal frequency to determine the amplitudes of the first 5 harmonics produced by the PA, including the fundamental frequency. For example, if the input signal is at 14 MHz, harmonics at 14, 28, 42, 56, and 70 MHz are measured. Output power at the fundamental frequency is reported, along with DC-to-RF power conversion efficiency and the total harmonic distortion of the PA. It is recommended you do not increase the input frequency past 14 MHz, because it will be difficult to measure the amplitude of the higher-frequency harmonics (especially n=5) due to the limited bandwidth of the oscilloscope.

Finally, the frequency response of the PA is measured between 4-20 MHz by default (this can be overridden by changing the freq vector if you wish).

Output: