Method and apparatus for rapidly testing passive components by reflectometry in the VHF range

A method of rapidly testing passive two terminal devices in the VHF range, said method comprising the steps of:

• (i) providing a long distributed constant transmission line comprising a first end and a second end and having a characteristic impedance R.sub.c,
• (ii) connecting an electric signal generator capable of generating frequencies in the VHF range and having an internal impedance equal to the characteristic impedance of the line to the first end of said line,
• (iii) connecting a two terminal device to be tested to the second end of said line,
• (iv) detecting the total voltage v.sub.t at the first end of the line,
• (v) detecting the maxima v.sub.tM and the minima v.sub.tm in the total voltage v.sub.t and
• (vi) determining a modulus of the reflection coefficient .vertline..GAMMA..vertline. on the basis of the following equation:
• .vertline..GAMMA..vertline.=(.vertline.v.sub.tM .vertline.-.vertline.v.sub.tm .vertline.).sup.e2.alpha.l /(.vertline.v.sub.tM .vertline.+.vertline.v.sub.tm .vertline.)
• wherein
• .alpha. represents the attenuation of the line and
• l represents the length of the line.

An apparatus for rapidly testing passive two terminal devices in the VHF range, said apparatus comprising:

• a distributed constant transmission line comprising a first end and a second end, and having a characteristic impedance R.sub.c,
• a resistive network having an input and an output, said resistive network comprising:
• a first leg including two resistances connected in series between said input and the ground, and an intermediate tab between said two resistances wherein a first resistance of said first leg, which is connected between the ground and the intermediate tab of the first leg has a value equal to 2/3 of the characteristic impedance R.sub.c of said line, while a second resistance of said first leg, which is connected between the input and the intermediate tab of said first leg has a value equal to 4/3 of the characteristic impedance R.sub.c of said line,
• a second leg including two resistances connected in series between said output and the ground, and an intermediate tab between said two resistances,
• wherein a first resistance of said second leg, which is connected between the ground and the intermediate tab of the second leg has a value equal to 2/3 of the characteristic impedance R.sub.c of said line while a second resistance of said second leg, which is connected between the output and the intermediate tab of said second leg has a value equal to 4/3 of the characteristic impedance R.sub.c of said line and
• a third leg including a resistance connected between said input and said output, and having a value equal to 4/3 of the characteristic impedance R.sub.c of said line,
• the output of said resistive .pi. network being connected to the first end of said line
• an electric signal generator capable of generating frequencies in the VHF range and having an internal impedance equal to the characteristic impedance of the line connected to the input of said resistive .pi. network,
• a two terminal device to be tested connected to the second end of said line,
• means for detecting a first signal related to the wave V.sub.r reflected by the device under test, between the output of said resistive .pi. network and the intermediate tab of said first leg
• means for detecting a second signal related to the incident wave V.sub.i, between the input of said resistive .pi. network and the intermediate tab of said second leg, and
• means for determining the behavior of a reflection coefficient .GAMMA. in the VHF range on the basis of the ratio of the modulus of the first signal and the modulus of the second signal .vertline.V.sub.r .vertline./.vertline.V.sub.i .vertline. to deduce the impedance of the two terminal device.

An apparatus for rapidly testing passive two terminal devices in the VHF range, said apparatus comprising:

• a long distributed constant transmission line comprising a first end and a second end and having a characteristic impedance R.sub.c,
• an electric signal generator capable of generating frequencies in the VHF range and having an internal impedance equal to the characteristic impedance of the line connected to the first end of said line,
• a two terminal device be tested connected to the second end of said line,
• means for detecting the total voltage v.sub.t at the first end of the line,
• means for detecting the maxima v.sub.tM and the minima v.sub.tm in the total voltage v.sub.t and
• means for determining a modulus of the reflection coefficient .vertline..GAMMA..vertline. on the basis of the following equation:
• .vertline..GAMMA..vertline.=(.vertline.v.sub.tM .vertline.-.vertline.v.sub.tm .vertline.).sup.e2.alpha.l /(v.sub.tM .vertline.+.vertline.v.sub.tm .vertline.)
• wherein
• .alpha. represents the attenuation of the line and
• l represents the length of the line.