Project Tuna Ii Bode Analyzer And Teaching Tool

Students measuring the frequency response of a linear circuit (e.g., an active filter) by manual methods find the task mind-numbing and repetitive, and the purpose was frequently lost in the minutiae of data-taking. Project TUNA (Texas Universal Network Analyzer), a Bode analyzer for low to moderate frequencies, was conceived as an answer to this problem. The prototype of Project TUNA was developed as a project in Electronics II (EENG 4409) in 1999, and permanent copies were constructed in 2000. Project TUNA has been integrated into the electronics curriculum of UT-Tyler since that time. It is used as both a laboratory instrument and as a teaching tool, particularly to illustrate the principles of phase-sensitive demodulation. However, Project TUNA had drawbacks. The performance of its switching-type phase-sensitive demodulator degraded markedly above 100kHz. The dynamic range of voltage gains was limited (‒30dB), and analysis times were longer than necessary for frequencies above a few hundred Hz. Project TUNA also required three GPIB-controlled test instruments (power supply, function generator, and multimeter). These limitations provided the impetus for Project TUNA II. Project TUNA II has muchimproved performance: wider dynamic range (‒40dB), wider frequency range (10Hz to 1MHz), and shortened analysis times for frequencies above 200Hz. Use of a multifunction dataacquisition card in the host PC eliminated the GPIB-controlled power supply and dc voltmeter; only a GPIB-controlled function generator is required. Project TUNA II was developed in prototype form in 2001; permanent hardware and a much-improved LabVIEW virtual instrument were created in 2004. Project TUNA II is currently used alongside Project TUNA in electronics laboratories, and Project TUNA II is used to expand the instructional themes of the original Project TUNA. This paper describes the development, design, laboratory use, and instructional resources of Project TUNA II. Description of prior work—overview of Project TUNA The junior-year curriculum of the BSEE program of the University of Texas at Tyler includes two semesters of electronics laboratory courses. Measurement of frequency response of linear networks is a part of the laboratory procedures of each semester. In particular, extensive measurements of complex (magnitude and phase) frequency response are made in a laboratory procedure on active filters in EENG 4109 (Electronic Circuit Analysis II Laboratory). Students performing these measurements by manual methods found the task mind-numbingly repetitive, and the purpose of the laboratory was frequently lost in the minutiae of data-taking. Project TUNA (Texas Universal Network Analyzer), a Bode analyzer for low to moderate frequencies, was conceived as an answer to this problem. Project TUNA, combining custom external hardware, GPIB instrumentation, and a LabVIEW virtual instrument program, was designed and developed in prototype form as a class project in EENG 4109 in 1999. Permanent copies of the Project TUNA hardware were constructed in 2000. Project TUNA has been used in the laboratory curriculum since that time. P ge 11045.2 A block diagram of Project TUNA is shown in Fig. 1. Fig. 1. Block diagram of Project TUNA Project TUNA relies upon switching phase-sensitive demodulation to measure both the magnitude and phase of the input voltage Vin and output voltage Vo of the network under test. An Agilent HP33120A arbitrary waveform generator furnishes a sinusoidal signal to three unity-gain quadrature networks. Each quadrature network contains four two-pole unity-gain all-pass filters arranged in two groups as shown in Fig. 2 below. The poles of the filters are chosen using a design method described by Keely 1 such that the phase difference between the two output voltages remains constant at 90° over a wide range (approximately 25:1) of frequencies. Three quadrature networks are used to cover the range of frequencies from 10Hz to 100kHz; the appropriate quadrature network is selected by activating its relay. Two-pole All-pass filter 0 Two-pole All-pass filter 1 Two-pole All-pass filter 2 Two-pole All-pass filter 3 + C 0 genæ V cosine output sine output Relay c æ gen V