Greetings,
I am working on converting a coupled-mode coaxial cable into a standing wave antenna. If anyone is not aware of it, it is a coaxial cable that has a corrugated copper shield and apertures milled into the shield at very close separation distances. The purpose of the shield and apertures is to provide an impedance mismatch and the discontinuities in the shield allow for the presence of standing waves. Since the magnitude of the standing waves decrease with radial distance, this cable becomes an inductively coupled Tx line. Its radiation pattern is that of an endfire antenna, see Antenna Theory: Design and Analysis 3rd edition pg 550.
In US patent no 5,473,336 entitled, cable for use as a distributed antenna, the author states that the coaxial cable is open ended and periodically loaded with some type of outer shield conductor tape melded onto the dielectric filling.
I was thinking that a dipole is a surface wave antenna, in that the arms end in open circuits, therefore the current is zero at the ends and there is a reflection of +1, the voltage wave is reflected and in phase with the sending wave, thus doubling the the effects on the electric field. But this is an electrical antenna, suppose I need a magnetic antenna, shouldn't I then short-circuit the load in order to get twice the current and doubling the H field strength? Would that burn out my amplifier or radio?
So whats my question? I have tested the leaky cable for coupling loss. This is the ratio of the power received by a dipole to the power in the cable. Technically I used a loop probe antenna, and I measured the leaked power on a portable spectrum analyzer. I also measured the power from another loop antenna. It seems the loop radiates more power than the leaky cable. I tested the cable by opening and short-circuiting the load. I did receive a boost in about 10 dBm. but it was still short compared to the loop.
I next ran an rf power amplifier through my Txing end. I received a -XdBm level peak compared to a -X+10 dBm on my loop. I can operate certain devices with the loop, but the cable seems dead. Also, for a -X dBm peak, I had to insert 40-50 watts of power into the cable. This is unacceptable.
However, I am stuck as how to improve the power being emitted by the cable. I need the power output from the cable to be greater than or equal to the loop. Right now I am measuring the input impedance of the cable and its S21. So, does anyone know of a procedure to improve the leaky power? I know in some cases, you can improve the gain of the cable by extending its length several lambda, but this is not possible in my case.
If anyone can help me, I'd very much appreciate it.
Thanks,
I am working on converting a coupled-mode coaxial cable into a standing wave antenna. If anyone is not aware of it, it is a coaxial cable that has a corrugated copper shield and apertures milled into the shield at very close separation distances. The purpose of the shield and apertures is to provide an impedance mismatch and the discontinuities in the shield allow for the presence of standing waves. Since the magnitude of the standing waves decrease with radial distance, this cable becomes an inductively coupled Tx line. Its radiation pattern is that of an endfire antenna, see Antenna Theory: Design and Analysis 3rd edition pg 550.
In US patent no 5,473,336 entitled, cable for use as a distributed antenna, the author states that the coaxial cable is open ended and periodically loaded with some type of outer shield conductor tape melded onto the dielectric filling.
I was thinking that a dipole is a surface wave antenna, in that the arms end in open circuits, therefore the current is zero at the ends and there is a reflection of +1, the voltage wave is reflected and in phase with the sending wave, thus doubling the the effects on the electric field. But this is an electrical antenna, suppose I need a magnetic antenna, shouldn't I then short-circuit the load in order to get twice the current and doubling the H field strength? Would that burn out my amplifier or radio?
So whats my question? I have tested the leaky cable for coupling loss. This is the ratio of the power received by a dipole to the power in the cable. Technically I used a loop probe antenna, and I measured the leaked power on a portable spectrum analyzer. I also measured the power from another loop antenna. It seems the loop radiates more power than the leaky cable. I tested the cable by opening and short-circuiting the load. I did receive a boost in about 10 dBm. but it was still short compared to the loop.
I next ran an rf power amplifier through my Txing end. I received a -XdBm level peak compared to a -X+10 dBm on my loop. I can operate certain devices with the loop, but the cable seems dead. Also, for a -X dBm peak, I had to insert 40-50 watts of power into the cable. This is unacceptable.
However, I am stuck as how to improve the power being emitted by the cable. I need the power output from the cable to be greater than or equal to the loop. Right now I am measuring the input impedance of the cable and its S21. So, does anyone know of a procedure to improve the leaky power? I know in some cases, you can improve the gain of the cable by extending its length several lambda, but this is not possible in my case.
If anyone can help me, I'd very much appreciate it.
Thanks,