An f0/2f0 (frequency ratio of two) microstrip diplexer with simple circuit configuration as well as low and wideband insertion-loss characteristics is proposed. It is a parallel combination of a coupled line for f0 port and a wave-trap circuit composed of a transmission line and an open stub for 2f0 port. All the lines and stub have a quarter-wave length for f0. Matching circuits are not needed. Circuit and electro-magnetic simulation results prove that the proposed f0/2f0 diplexer exhibits well-balanced properties of insertion loss (IL), IL bandwidth, and isolation, as compared to conventional simple f0/2f0 diplexers composed of two wave-trap circuits or two coupled lines. The proposed diplexer is fabricated on a resin substrate in a microstrip configuration at frequencies of f0/2f0=2.5/5 GHz. Measured results are in good agreement with simulations and support the above conclusion. The proposed diplexer exhibits ILs of 0.46/0.56 dB with 47/47% relative bandwidth (for f0/2f0), which are lower and wider than f0/2f0 diplexers in literatures at the same frequency bands.

This paper describes the theoretical analysis and experimental verification of a new type high-isolation surface-acoustic-wave (SAW) duplexer by using a SAW on-chip compensation circuit designed to cancel the signal of the main SAW filter at an attenuation frequency band. First, a numerical analysis based on the interference of waves propagating parallel waveguides is applied to clarify the relation between the absolute improvement value of the filter's attenuation level and cancel conditions. Then, the feasibility of the SAW compensation circuit using the double mode SAW (DMS) resonator filter are studied in both a circuit simulation and experiment. As a result, a 10-30 dB attenuation improvement was achieved within a band range of several tens of MHz using electrical characteristics of the lower side slope in the DMS resonator filter, and that it agrees well with the result obtained by numerical analysis. These results are expected to be useful for current and future mobile systems wants higher receiver sensitivity.

Using an electro-absorption duplexer (EAD) we presented a transceiver (TRx) module for dual function of both electrical-to-optical (E/O) and optical-to-electrical (E/O) conversion at 60 GHz band. The EAD chip was fabricated by monolithically integrating both a waveguide photodiode (PD) and an electro-absorption modulator (EAM) in association with traveling wave electrodes. We also investigated the issues of RF packaging in which the optoelectronic and electronic amplifier devices were co-packaged in a single housing. The RF impedance matching was accomplished in assistance with a microstrip bandpass filter.

In this paper a novel dielectric resonator (DR) bandpass filter (BPF) with flexible arrangement of attenuation poles is proposed. This DR filter is similar to a conventional DR filter except adding a microstrip line below a DR, which not only shifts the location of attenuation poles, but also improves skirt characteristics. The duplexer with the proposed DR BPF has been yielded better isolation and sharper skirt behavior than that with a conventional DR filter. The implemented duplexer has shown a good performance and been well agreed with the simulation.

In this paper, the method of locating multiple transmission zeros by the tap-coupling technique is described for bandpass filters (BPFs), using short-ended λ/2 resonators and its application to a duplexer. First, the method of locating the transmission zero using the short-ended λ/2 resonators is examined with various excitation methods. We focus on four types of short-ended λ/2 resonators: the end-coupling type, tap-coupling type, capacitive tap-coupling type and inductive tap-coupling type. Secondly, the BPFs based on the basic characteristics of the respective resonators are proposed and designed on the basis of a general filter theory with narrow band approximation. Lastly, we propose and design new duplexers consisting of the proposed BPFs. The results lead to the conclusion that the basic characteristics of the short-ended λ/2 resonators are useful for realizing a BPF with multiple transmission zeros and a high-performance duplexer fabricated without increasing the number of elements.

This paper proposes a new algorithm to control an adaptive duplexer for multiband software radio. It uses a wideband low isolation device combined with a two-tap/two-loop adjustable canceller to eliminate the need for multiple switched high isolation duplexers. The taps are adjusted to provide isolation peaks in the transmit and receive bands. The algorithm is based on the superposition of squared errors and achieved 66 dB isolation of the transmit signal and a 37 dB cancellation of the transmitter noise in the receiver band.

26 GHz bandpass filter and duplexer using TM11δ rectangular-mode dielectric cavity resonators are proposed. These have a configuration compact and suitable for mounting on circuit boards. The resonators consisting of the Ba(Mg,Ta)O3 ceramic material showed a high quality factor value of 2600, which is roughly comparable to that of conventional E-plane waveguide filters. The dielectric losses of the ceramic material were experimentally evaluated from the viewpoint of the high frequency operation and the dielectric loss tangent of 7.410-5 was observed at 20 GHz. A three-stage Tchebyscheff bandpass filter with 0.4% relative bandwidth was fabricated and the passband insertion loss was 1.7 dB. A duplexer designed with two TM11δ mode filters and a microstrip T-junction is also presented.

In this paper we describe the investigation of design methodology of a planar duplexer consisting of BPFs using mixed tapped resonators. Firstly, we propose the planar duplexer consisting of bandpass filters (BPFs) using a tapped open-ended λ/2 resonator and a tapped λ/4 resonator. The duplexer is designed based on the general filter theory with narrow band approximation and tap-coupling technique. The actual duplexer is fabricated using a coplanar waveguide (CPW). Secondly, downsizing of the planar duplexer is carried out based on the BPF using stepped impedance resonators (SIRs). Lastly, another type of duplexer consisting of different BPFs using mixed tapped resonators is investigated in the same manner. The results of this study lead us to the conclusion that the design methodology is useful for realizing the high-performance planar duplexer fabricated without increasing the number of elements.

Cost down of millimeter wave components, especially antenna duplexer, is a key for spreading millimeter wave communication systems. An excellent cost-performance antenna duplexer is proposed. It consists of two E-plane filters and a wave-guide circulator. The performance fluctuations due to manufacturing accuracies are studied by simulations and experiments. These results are very useful for cost-down of the practical duplexer without performance degradation.

The sharpness of the roll-off response of bandpass filters is a major concern for wireless communication systems. Bandpass filters with attenuation poles provide sharp roll-off. This paper investigates the performance of a ceramic comb-line filter with attenuation pole resonators (APRs), and studies the effects of the attenuation pole resonators on the filter response. The presented APRs are improved versions of previous ones and they are modeled here. The obtained results show that the length of APRs can be miniaturized via the loading capacitance. The resultant volume is about 400 mm3, which is very small comparing to coaxial type filters with the same attenuation rate in the stopband. With attenuation pole resonators added, skirt attenuation is greatly improved. Narrow bandwidth bandpass filters with attenuation poles in the stopband are designed and tested. Two designed examples demonstrate the flexibility of the attenuation pole resonator in the filter configuration. Experiments show good agreement with simulation results.

Taking a 1.5-GHz SAW antenna duplexer for PDC, we have developed a new configuration for the transmitter final stage filter and a new weighting technique for the receiver top filter. These transmitter and receiver filters provide insertion losses as low as 0.8 and 1.6 dB, respectively. Combining the filters, we have developed a miniature antenna duplexer of which size is 1.40.60.2 cm3 , several-time smaller than that of a conventional dielectric-filter duplexer. It also ensures sufficient power-handing capabilities.