1. Field of Invention
This invention is related to variably tuned circuits and more particularly to matching a source of a frequency modulated signal to a load.
2. Description of the Prior Art
In modern warfare, a source of radio frequency radiation, known as a jammer, is used to disrupt either radio communication or radar operation at an enemy installation. The intensity of the radiation at the installation is inversely related to the distance between the installation and the jammer. Therefore, the jammer is most effective when it is located in the vicinity of the installation.
One particular type of jammer is delivered to the vicinity of the installation in a vehicle that is fired from an artillery piece. At a predetermined time after the firing, when the vehicle is at an altitude of several thousand feet, the jammer separates from the vehicle, thereby causing the jammer to rapidly lose altitude. The predetermined time is selected to cause the jammer to land in the vicinity of the installation.
There is a substantial impact between the jammer and the ground when the jammer lands. Because of the distribution of the mass of the jammer, the impact implants the jammer firmly in the ground at a desired attitude with the respect to the ground. The impact causes a whip antenna to emerge from the chassis of the jammer.
The radiation from the jammer is typically frequency modulated over a known band of frequencies. However, the whip antenna is usually substantially resonant over a band of frequencies that is narrow compared to the known band, whereby the antenna mismatches the output impedance of the jammer to the impedance of free space at frequencies within the known band. The mismatch causes the radiation to be at a reduced level, thereby decreasing the effectiveness of the jammer.