Aiming at the problems of low gain, low efficiency in low frequency band and warping pattern in high frequency band of the existing HF broadband whip antenna, this paper introduces frequency reconfigurable antenna technology and radiation blades loading technology to redesign whip structure, loading and matching network in different bands, and designs a kind of frequency-reconfigurable whip antenna with improved gain and efficiency. The whip body structure, loading and matching network structure of the antenna in each band are optimized, and the on-off control is carried out through the radio frequency switch according to the actual needs. The results show that the standing wave ratio of the proposed antenna is all less than 3, the average value is 2.32; the gain is all greater than -2dB, the average value is 3.63dB; the total efficiency is all over 20%, the average value is 72.77%, and the pattern keeps horizontal omnidirectional in the whole short wave band without upward warping phenomenon.

Introduction

The working frequency band of 10-meters HF whip antenna is 3∼۳۰MHz, and the bandwidth is up to 10 octaves. In the whole short-wave band, for the whip antenna with standing wave current distribution, the limitation of its operating frequency band is mainly caused by its impedance characteristics [1], [2], because the input impedance of whip antenna is highly sensitive to frequency, which is hard to match the feeder. In low frequency band, the antenna has small electrical length, small input resistance, large input capacitance, high Q value, low antenna efficiency, narrow working frequency band, which makes it difficult to meet the requirements of modern communication. In high frequency band, the effective length of antenna is far larger than 1/4 wavelength, the reverse phase current on the oscillator increases continuously, the maximum direction of the antenna pattern deviates from the horizontal direction, and the phenomenon of ‘‘warping’’ appears, which results in the antenna can’t satisfy the short-range and medium-range communication in the high frequency band. In order to improve the bandwidth and radiation performance of antennas, top loading [3], [4], loading network [5]–[۷], broadband matching network [8]–[۱۰], fractal technology [11]–[۱۳] have been proposed. At present, loading and matching network technology is widely used, because the introduction of impedance elements effectively improves the standing wave of antenna, but it also brings new losses to the antenna, which greatly reduces its gain and efficiency.