# US 4,394,617 A · Swept-dip probe

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- Number: US 4,394,617 A
- Document ID: US4394617A
- Status: Granted
- Kind: A
- Application number: 06/298,657
- Filed: 1981-11-18
- Granted: 1983-07-19
- Earliest claimed: 1981-11-18
- Inventors: E. Lawrence Wampler
- Web page: https://patentgrep.com/patent/US4394617A

## CPC

- G01R 27/2688: {Measuring quality factor or dielectric loss, e.g. loss angle, or power factor (power factor related to power measurements G01R21/006; testing capacitors G01R31/016)}
- G01R 23/07: using response of circuits tuned on resonance, e.g. grid-drip meter
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

The present invention relates to the design and fabrication of a probe, ancillary signal conditioning circuits with display circuits and related equipment required to measure the resonate frequency and display the shape of the resonance curve. The probe uses the energy absorbing method of indicating these parameters. A graphical display or an analog meter dip indicates the resonant frequency. A digital frequency meter can measures the frequency points precisely.

## Claims

### Claim 1

A probe comprising a detachable coupling link acting as a primary winding of a transformer, a secondary is formed by the network-under-test coupling inductance; one terminal of the primary is series connected to a diode, the second terminal of the primary winding is connected to the outer conductor of a coaxial transmission line; the second terminal of the diode is connected to the center conductor of the coaxial transmission line; the purpose of the diode is to couple rectified r.f. energy to the primary winding of the transformer and to rectify the r.f. energy for measurement of the circuit resonance parameter; the coaxial transmission line center conductor and the first diode junction are connected to a second diode; the second diode, rectifies the r.f. energy in phase opposition to the first diode, the opposite terminal of the second diode is connected to the outer conductor of the coaxial transmission line; an analog signal that is a net result of the rectification by the two diodes is carried by the transmission line to the r.f. energy-analog signal combiner/separator; the input to the combiner/separator is the r.f. energy source and the output is the analog signal representation of the resonance response curve that is a frequency function of the network-under-test; the analog signal is displayed by a suitable display device with radio frequency on one axis, driven by the frequency sweep analog waveform and on the other axis is the network response function driven by the probe analog waveform, a result of probe coupling to the network-under-test; and,
including a r.f. frequency-analog signal combiner/separator for processing the signals and comprised of an r.f. input connection, a r.f. signal output, coupled to the probe coaxial cable center conductor through a d.c. blocking capacitor; the coaxial cable center conductor is also connected to an r.f. choke first end, and the r.f. choke second end is connected to the display device, the display device end of the r.f. choke, the second end, is connected to a r.f. bypass capacitor; the opposite end of the r.f. bypass capacitor is connected to the common circuit point of the system, thus forming a lowpass filter.

### Claim 2 (depends on 1)

A probe as recited in claim 1, except an auto-transformer is connected between the two diodes and the center conductor of the transmission line, to form an impedance match between the diode network and the transmission line, the auto-transformer tap terminal is connected to the center conductor of the coaxial transmission line, the top auto-transformer terminal is connected to the junction point of the two diodes, and the bottom auto-transformer terminal is connected to the coaxial transmission line outer conductor through a d.c. blocking capacitor; a resistor is connected across the the two outer terminals of the auto-transformer for the purpose of trimming the relatively high diode/link circuit r.f. impedance to that required to match the transmission line; the auto-transformer is used to step-down the relatively high diode impedance to the transmission line.

### Claim 3 (depends on 1)

A probe as recited in claim 1, including a digital frequency meter to measure precisly the frequency points along the response curve in a very slow sweep and with manually swept frequency; and an analog meter, digital and electro-mechanical, used to indicate the network-under-test resonant frequency point.

### Claim 4 (depends on 2)

A probe as recited in claim 2 including a matching transformer of conventional design.

### Claim 5 (depends on 2)

A probe as recited in claim 2 including a matching transformer of the transmission-line transformer type of design.

### Claim 6 (depends on 1)

A probe as recited in claim 1 with a sweep waveform including a pause of selectable time duration and curve point location; the pause time duration used to mark the display and to permit the digital frequency counter to perform a frequency measurement.