Abstract: Disclosed herein is the structure of a Square Quadrifilar Helical antenna (S-QHA). The structure of the S-QHA includes a square column, four radiation elements, and a feed network. The four radiation elements are formed on the square column. The feed network is disposed at the top or bottom of the square column, and feeds signals to the radiation elements at a phase difference of 90 degrees in a clockwise or counterclockwise direction. As a result, the S-QHA according to the present invention can receive circularly polarized signals.

Abstract: A radar detector includes an antenna for receiving a first signal of ultrahigh-frequency, a first local oscillator oscillating a second signal, a first filter removing noise from the second signal oscillated via the first local oscillator, a first mixer mixing the first signal of ultrahigh-frequency with a third signal filtered via the first filter, an intermediate frequency amplifier amplifying a fourth signal mixed at the first mixer, a second local oscillator oscillating a fifth signal, a second mixer mixing a sixth signal amplified via the intermediate frequency amplifier with the fifth signal oscillated by the second local oscillator, a second filter filtering a seventh signal mixed at the second mixer, a demodulator converting analog values of an eighth signal filtered by the second filter into digital values, a memory part storing data of relations between a ninth signal converted via the demodulator and the second and fifth signals oscillated by the first and second local oscillators, a central proces

Abstract: A radar detector includes an antenna for receiving a first signal of ultrahigh-frequency, a first local oscillator oscillating a second signal, a first filter removing noise from the second signal oscillated via the first local oscillator, a first mixer mixing the first signal of ultrahigh-frequency with a third signal filtered via the first filter, an intermediate frequency amplifier amplifying a fourth signal mixed at the first mixer, a second local oscillator oscillating a fifth signal, a second mixer mixing a sixth signal amplified via the intermediate frequency amplifier with the fifth signal oscillated by the second local oscillator, a second filter filtering a seventh signal mixed at the second mixer, a demodulator converting analog values of an eighth signal filtered by the second filter into digital values, a memory part storing data of relations between a ninth signal converted via the demodulator and the second and fifth signals oscillated by the first and second local oscillators, a central proces