Multi-frequency matching for wide-band antennas

For matching of complex load with transmission line two cases are usually examined: narrow-band and wide-band matching. However in practice often it is necessary to ensure two-frequency or multi-frequency matching, when ideal matching on two or several narrow frequency bands is required. The authors examine the two-frequency matching method. This method allows matching of arbitrary complex loads on two arbitrary frequencies. The method is based on L-type circuit usage. Matching network structure is shown. On one frequency first L-circuit L1 or L2 matches load with transmission line. On the second frequency input impedances of these L-circuits are Z_L1 and Z(L2). The second L-circuit matches these impedances with the line on second frequency. Then the elements of the second L-circuit are replaced by parallel and serial oscillating contours. Resonance is present on the first frequency and the first L-circuit does not affect the whole network; on the second frequency contour impedances are equal to respective L-circuit elements impedance. The resulted network provides two-frequency matching