A new printed antenna system mounted in an aperture in the roof of a car is evaluated for broadcast signal reception from 88-108 MHz. Results from simulations on the vehicle are compared with measurements. The overall performance of the antenna is also compared to common types of vehicle antennas, the roof monopole and a glass based antenna. Overall the average gain of the antennas was better than 3 dBi for vertical polarization and 10 dBi for horizontal while the input return loss was generally better than 2 dB before matching sections in the tuners and comparable with common automotive antennas. The antennas in the roof aperture offer an alternative place to mount antennas on automobiles.
Diplexers are three-port filtering devices with a junction connecting two channel filters; the common port connects to an antenna which serves the two channel filters bearing the second and the third port. In the design of diplexers, the technique used in connecting the two channel filters is of great importance to the designers. This is because it determines the size, the effectiveness of signal splitting and combining as well as the ease in implementation. In this article, an asynchronously tuned double split-ring resonator (SRR) was used in joining the two channel filters. Without incurring any extra space for the junction, the SRR, being a dual-mode resonator, also functioned as a resonant pole for each channel filter. A diplexer operating at 2 GHz and 3 GHz with 4% fractional bandwidths and 20 dB return loss has been demonstrated. The interactions between the SRR and the channel filters were investigated. Good agreement between the simulated and the measured responses was achieved.
K E Y W O R D Sasynchronous coupling, split ring resonator, synchronous coupling
In this article, a high frequency amplifier design method based on the negative impedance compensation has been demonstrated analytically and experimentally. An effective nonlinear model has been used to simulate the harmonic distortion and intermodulation distortion factors in amplifier design. The simulation and measurement results show that, with this proposed technique, high linearity and high gain accuracy can be achieved. The proposed method is particularly suitable for linearisation of RF/microwave amplifiers with low open-loop gain.
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