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A micromachined based narrow band Fabry-Perot tunable bandpass filter is designed, fabricated and measured. The narrow bandpass characteristic is due to the cavity formed in the bandgap structures by the insertion of a transmission line resonator between the two Bragg reflectors. The parametric analyses of the Fabry-Perot electromagnetic bandgap (EBG) filter are investigated by considering (i) the effect of the EBG cells on the Q factor; (ii) the change in the cavity length and the slot dimension to influence the filter performance characteristics; and (iii) the propagation characteristics of the Fabry-Perot EBG filter. The Fabry-Perot EBG tunable filter is fabricated on a silicon substrate using a surface micromachining process. The measurement result of the fixed Fabry-Perot filter shows a 3-dB bandwidth of around 250 MHz with an insertion loss of 4 dB. Capacitive microelectromechanical system switches are fabricated in the cavity to develop a tunable filter. The switch heights are varied with a bias voltage from 0 to 34 V, and the resonant frequency is tuned. The result shows a tuning range of 7.5% with an insertion loss that varies from 4.1 to 7.35 dB. [ABSTRACT FROM AUTHOR]

The performance of multiband orthogonal frequency division multiplexing ultra-wideband (UWB) signal over a multimode fibre-based radio-over-fibre link is discussed. The co-transmissions of UWB signals with other wireless signal standards, including wireless code division multiple access (W-CDMA) (2.15 GHz), wireless local area network 802.11a/g and global system for mobile communication (1.8 GHz) are considered. Based on the measurement results, it has been shown that UWB signals can be transmitted without error over 400 m for the highest data rate of 480 Mbps using the system proposed. The co-transmission can also be successfully done with minimal mutual interference. [ABSTRACT FROM AUTHOR]

A wideband circularly polarised slot antenna is presented. The slot antenna is fed by four microstrip line feeds orientated to have relative phases of 0°, 90°, 180° and 270° using a feed network comprising a pair of broadband 90° hybrid. The proposed antenna delivers measured and simulated impedance bandwidths of 77.8% (1.02–2.32 GHz) and 89.1% (1.02–2.66 GHz), respectively, for standing wave ratio (SWR)<2, measured and simulated axial-ratio bandwidths of 88.9% (1–2.6 GHz) and 81% (1.1–2.6 GHz), respectively, for axial ratio < 3 dB and measured and simulated gain bandwidths of 33% (1.5–2.1 GHz) and 27% (1.6–2.1 GHz), respectively, for gain >3 dB. A good agreement is observed between simulation and measurement. [ABSTRACT FROM AUTHOR]

A compact dual-band printed wire antenna for applications in wireless communications is presented. An additional shorted parasitic element to the F-shaped wire antenna is introduced to achieve a dual-band operation. As an example, a new antenna was designed and fabricated for wireless local area network applications that operate in the 2.4 and 5.2/5.8 GHz bands. The prototyped antenna offered two separate measured impedance bandwidths of 700 (2.35–3.05 GHz) and 2150 MHz (3.95–6.1 GHz), for a return loss less than -10 dB. A measured antenna gain of 1.78–1.9 dBi was observed across the lower band, whereas a measured antenna gain of 3.9–4.4 dBi was observed across the upper band. The measured radiation patterns were stable across the passband. [ABSTRACT FROM AUTHOR]

A high-efficiency concurrent dual-mode dual-band power amplifier is presented. It simultaneously operates at class-F mode for one band and at inverse class-F mode for the other band. With this mode assignment method, the conflict in harmonic impedance control for concurrent dual-band applications is avoided. Experimental results show a high performance of more than 80% peaking power added efficiency with 40.6 and 41.8 dBm output power in the sampled bands of 0.8 and 1.25 GHz, respectively. [ABSTRACT FROM AUTHOR]

A novel 60 GHz three-dimensional (3D) cavity bandpass filter using low-temperature co-fired ceramic technology is presented. The proposed filter shows two finite transmission zeros with each at either side of the passband using the extracted-pole and cross-coupling techniques. Both simulated and experimental results of the filter are described. [ABSTRACT FROM AUTHOR]

A compact microstrip lowpass filter with an ultra-wide stopband is proposed. To achieve wide stopband suppression and compact size, both symmetrically loaded resonant patches and meander transmission line are adopted. A demonstration filter with 3 dB cutoff frequency at 1.3 GHz has been designed, fabricated and measured. The proposed filter also exhibits a very wide stopband of 152%, and is able to suppress the eleventh-harmonic response together with a small size of 0.12λg × 0.071λg, where λg is the guided wavelength at 1.3 GHz. [ABSTRACT FROM AUTHOR]

A novel miniaturised microstrip lowpass filter has been studied. With triangular and high–low impedance resonators symmetrically loaded, the proposed filter has successfully achieved size reduction and performance enhancement simultaneously. A demonstrator filter with 3 dB cutoff frequency at 1.5 GHz has been designed, fabricated and measured. Results show that a roll-off of 257 dB/GHz together with a relative stopband bandwidth of 157.4% can be obtained while achieving a high figure-of-merit of 38747. [ABSTRACT FROM AUTHOR]

A compact slow-wave microstrip rat-race ring coupler is presented. The new structure effectively reduces the occupied area to 8% of the conventional rat-race ring coupler due to the slow-wave effect. The design is validated both by using the full-wave electromagnetic simulator and by measurement. [ABSTRACT FROM AUTHOR]

A highly selective dual-band stepped impedance bandpass filter is presented. The filter has two tunable passbands. Two finite out-of-band transmission zeros are realised, which have high selectivity. [ABSTRACT FROM AUTHOR]

A compact microstrip lowpass filter with quasi-elliptic response is proposed. To achieve compact design, both symmetrically loaded radial-shape patches and meandered main transmission line are adopted. To realise the quasi-elliptic response and strengthen the roll-off sharpness for the filter, a coupled capacitor between adjacent radial-shape patches is introduced in interdigital form. Furthermore, the adoption of radial-shape patches and the interdigital structure can introduce both serial and parallel resonance in the circuit. Thus, a wide stopband with 7th harmonic suppression is achieved. A demonstration filter with 3 dB cutoff frequency at 1.18 GHz has been designed, fabricated and measured. Results show that a relative stopband bandwidth of 132.3% (referred to a suppression degree of 15 dB) is obtained while achieving a high figure-of-merit of 11543. [ABSTRACT FROM AUTHOR]

A compact planar bandpass filter with improved selectivity using source–load coupling is proposed. The new filter consists of quarter-wavelength resonators and short-ended feedlines. An extra transmission zero is produced near the passband owing to the source–load coupling, which can improve the skirt-selectivity of the filter, and quarter-wavelength resonators are used to enhance the rejection level around the second harmonic. Both simulated and measured results with good agreement are presented. [ABSTRACT FROM AUTHOR]