A dual-mode dual-band bandpass filter with high cutoff rejection using an asymmetrical transmission zeros technique is presented here. Two dual-mode filters are combined to form a dualband filter by sharing the input and output coupled-feed line, which is more flexibly designed and maintains a small circuit size. Controllable asymmetrical transmission zeros (TZs) at lower-and uppersideband locations of dual-band filters are designed to achieve the high-selectivity dual-mode dual-band bandpass filter. Unwanted signals are suppressed by the location of the TZs between the first and second passbands, which gives a much-improved signal selectivity for the dual-band bandpass filter. The two passbands are centered at 1.8 and 2.4 GHz, respectively. The first and second passbands' insertion losses are only 0.9 dB and 1.1 dB, respectively, and the measured return losses are better than 20 dB. Three transmission zeros are located between the two passbands, which achieve rejection levels about 40 dB attenuations from 1.9 to 2.3 GHz.

This paper presents a high-selectivity dual-mode dual-band bandpass filter with good cutoff signal rejection. The high-selectivity dual-mode dual-band bandpass filter is designed by an asymmetrical transmission zero (TZ). The asymmetrical transmission zeros next to the upper sideband of the first resonant filter and the TZ at the lower sideband of the second passband filter are combined to form a dual-mode dual-band filter. The locations of the TZ are designed at the side passbands of the filters in order to filter out unwanted signals, obtain good cutoff rate in the stopband, and give much improved signal selectivity for the dual-band bandpass filter. One dual-mode filter is designed at the center frequency of 1.8 GHz and the other's desired performance at 2.4 GHz. The two filters can be combined using the coupled feed lines in which these coupled feed lines present a simple structure of dualmode dual-band bandpass filter. The insertion loss of the dual-mode dual-band bandpass filter is less than 1.2 dB, and the rejection between two transmission bands is about 18 dB from 1.9 to 2.35 GHz. This high-performance dual-mode dual-band bandpass filter can be used in many wireless communication systems.

This article presents the design of a dipole antenna structure in combination with a square electromagnetic band gap (EBG) to monitor the children trapped in cars using a 750 MHz frequency band which responds the most to human movement detection. The antenna structure was designed on a copper plate with a thickness of 0.297 mm and polyester mylar film baseplate with a thickness of 0.3 mm and dielectric value of 3.2. By design, the dipole antenna had a size of 201.56 × 12.5 mm 2 and 18 × 5 units square electromagnetic band gap (EBG) of size 254.64 × 71.86 mm 2 . The results of the measurement showed that the bandwidth impedance in the operating frequency range was 4.78% (735-771 MHz) with a gain of 6.3 dBi. There was an omnidirectional signal transmission. The dipole antenna had the best distance between the EBG plates of 30 mm. When being examined at a distance of 500-1,600 mm, it was the most effective at an average signal strength of approximately 0.032 mW every time there was movement of a human body in the car.

An ease of four-port dual-mode diplexer with high signal isolation is presented. A compact dual-mode diplexer with high signal isolation between the Rx and Tx modules is achievable by only using one resonator filter topology. Two back-to-back dual-mode diplexers have a 180° phase shift in one branch. The high isolation can be achieved by amplitude and phase cancellation technique. The delayed transmission line can be easily achieved by the phase shifter. The simulated and measured four-port dual-mode diplexers are designed at the centre frequency of Rx/Tx at 1.95 GHz and 2.14 GHz, respectively. The measured results of Rx/Tx dual-mode diplexer devices are presented with 47.1 dB Rx/Tx isolation. This four-port dual-mode diplexer achieves the isolation (S32) of more than 24.1 dB when compared with the conventional three-port dual-mode diplexer structure.

This article presents a dipole antenna using an I-shape adding technique on both sides of the antenna's body to widen the frequency range, using a horn waveguide to gain enhancement and harvest energy by matching the circuit which is compatible with the voltage multiplier circuit at the RF frequency (510-790 MHz) in a TV digital system. Having measured the effect of the antenna, it was found that the antenna operates at a frequency range of 60.24% (450-838 MHz), a 67.79% increase from the base dipole antenna, which has again enhancement of 10.23 dB from adding the horn waveguide (60.99%). It has a pattern of energy radiating in a specific direction, and when the antenna is used with an energy harvesting circuit to get energy or power from the front direction of the TV digital antenna at a distance of 10 km, it is capable of harvesting energy of up to 7.33 µW.