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This article proposes a novel design of a compact single-aperture dual circular polarization (CP) antenna with integrated duplexing functions using a phase controllable coupled resonator structure. To the best of the authors’ knowledge, this is the first report of a multifunctional CP antenna with integrated duplexing performance and dual polarizations. The two orthogonal CPs are realized for the two respective filtering channels. Each channel contains a phased filtering power divider forming the dual-feed to a patch to achieve right-hand or left-hand CP (RHCP or LHCP). The required output phases of the dividers are realized by varied configurations of the coupled k/2resonator pairs. A duplex-CP-antenna with RHCP/ LHCP at the downlink/uplink (2.45/2.7 GHz) is designed, fabricated, and measured. It achieved a 3dB AR bandwidth of 3.2/7.7% at the downlink/uplink and an isolation better than 20 dB. Meanwhile, the antenna showed expected second-order filtering characteristics at both channels.

A balanced RF duplexer with low interference in an extremely narrow bandgap is proposed. The Long-Term Evolution band-7 duplexer should be designed to prevent the co-existence problem with the WiFi band, whose fractional bandgap corresponds to only 0.7%. By implementing a hybrid bulk acoustic wave (BAW) structure, the temperature coefficient of frequency (TCF) value of the duplexer is successfully reduced and the suppressed interference for the narrow bandgap is performed. To achieve an RF duplexer with balanced Rx output topology, we also propose a novel balanced BAW Rx topology and RF circuit block. The novel balanced Rx filter is designed with both lattice- and ladder-type configurations to ensure excellent attenuation. The RF circuit block, which is located between the antenna and the Rx filter, is developed to simultaneously function as a balance-tounbalance transformer and a phase shift network. The size of the fabricated duplexer is as small as . The maximum insertion loss of the duplexer is as low as 2.4 dB in the Tx band, and the minimum attenuation in the WiFi band is as high as 36.8 dB. The TCF value is considerably lowered to .

In this article, a narrow-bandwidth duplexer with a triple-split ring resonator (T-SRR) using mu-negative metamaterial is presented. The T-SRR not only has negative permeability at the operating frequency band but also flexibility in size adjustment. The experimental results for insertion and return losses are 1.33 and 16.1 dB with a bandwidth of 10% at a RX center frequency of 8 GHz, and they are 1.27 and 16.8 dB at the same bandwidth at a TX center frequency of 10 GHz, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1537–1540, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27656

Transmitter leakage (TxL) has a significant impact on the performance of frequency division duplex devices using zero-IF receivers and thus requires a suitable compensation. In contrast to analog approaches, digital TxL compensation approaches can easily be reconfigured and therefore are highly attractive for multiband mobile devices. In this contribution, we present a system model, describing the TxL impact on the received digital baseband signal. Furthermore, we show analytically that TxL causes an additional, irreversible signal-to-noise loss due to the quantisation in the analog-to-digital converter, which limits the applicability of a digital TxL compensation. However, this signal-to-noise ratio loss remains negligibly small as long as the TxL interference does not exceed significantly the desired received signal. For TxL to be compensated digitally, the TxL channel needs be estimated. In this work, we present two TxL channel estimation approaches suitable for frequency flat and frequency selective channels. It is shown that the usage of these approaches mitigates effectively the TxL impact on the system performance. Thus, the system designer can allow much stronger TxL, which significantly relaxes the requirements on the transmitter‐receiver isolation of the duplexer and the linearity of the analog receiver frontend. Copyright © 2011 John Wiley & Sons, Ltd. *Correspondence

This paper is aimed at making it clear why we device engineers are keen to have high quality and highly piezoelectric materials for sophisticated radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices to be used in future communication systems. First, RF SAW/BAW resonators and their filter application are introduced, and it is shown how the resonator properties directly reflect to achievable filter performances. Discussions are also provided on how the acoustic and piezoelectric properties of base materials influence the total device performances. An emphasis is given to the fact that use of high quality and highly piezoelectric materials is essential for the applications. It is also demonstrated how high performance devices are achievable by the use of high coupling materials such as a single-crystalline LiNbO3 substrate with specific crystallographic orientation with extremely large electromechanical coupling. Further discussions are given on new applications of extremely wideband SAW/BAW resonators employing ferroelectric materials with extremely large electromechanical coupling.

This article presents a correction to a previously published duplexer-less LNA/PA circuit incorporating a bondwire antenna showing the comparison between the calculated, simulated, and measured results of the gain, radiated power, radiation pattern, and the transmitter to receiver link-budget for a bondwire-antenna for short-range radio communications in the 6-GHz frequency range.The correction is given in the radiation efficiency and power transmitted by the PA. The LNA and PA were matched to the 50-Ω ports of the measuring instruments via an active inductor. Besides the inductive bondwire antenna, the LNA and PA are designed to be completely inductor-less, thus, saving the silicon chip area. The transceiver range is calculated to be about 4.72 m, ideal for applications such as remote controls, biomedical monitoring equipment, or RFID tags. Both front end blocks are designed with low-power, low cost, and high yield considerations for production in industry. The inductorless LNA parameters at 6 GHz are S21 of 14 dB for both the LNA and PA, a deduced NF of 4.9 dB for the LNA, S11 and S22 less than −10 dB, with 10-mW TX, and 15-mW RX power consumption for a 1.2 V supply. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:761–766, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25823

A novel duplexer design based on cross-coupled resonators is presented which has the advantages of small size and reasonably sharp cutoff frequency. A duplexer for the UMTS upload and download bands is fabricated and the measured response is shown to be in close agreement to full-wave simulations. The fractional bandwidth for both bands is about 3%. The duplexer has an insertion loss of less than 1 dB and provides more than 20 dB of isolation. Lumped-element models for both the resonator and duplexer are derived and their responses are also shown to be very close to the simulated results, which make them potentially very useful since it can simplify the design of systems using the duplexer. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2792–2795, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25590

A duplexer filter with open-loop resonators, having internal stubs, for the GSM band in the DSC1800 Cellular Radio Base Station standard is presented. The filters use square open-loop resonators. Insertion of the stubs allows the perimeter of the loop to be less than λ/2, which is the length used in the canonical loop. The device was fabricated on PTFE (RO3010) board. An eight-pole selective filter with a single pair of attenuation poles was used. A full-wave EM simulator was used to obtain the dimensions of the resonators. The measurement results are presented in comparison with the expected simulated values. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2422–2426, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23677

In this article, organic SIP based FEM comprised of passive components, power amplifier module, and SAW duplexer are designed, fabricated, and optimized for CDMA handset applications. Two different geometries are compared for optimizing their performance characteristics and verifying their applicability. In addition, LC resonant tank circuits are adopted in the DC bias circuits in order to improve ACPR characteristics and to reduce the size of FEM. The proposed resonant tanks can be easily embedded into and integrated onto the organic SIP packaging substrate because of the relatively small inductance and capacitance values compared with conventional RF choke inductor. The fabricated and optimized organic SIP based FEM has a gain of 25.9 dB, DC supply current of 387 mA at 25 dBm, ACPR1 of −50.8 dBc at 885 kHz, ACPR2 of −56.3 dBc at 1980 kHz, and PAE of 24%, respectively. The fabricated FEM has a size of 6 × 5 × 1.3 mm3 (height). The organic SIP based FEM is promising for advanced handsets and wireless applications due to the small size, low cost, and high performance characteristics. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2044–2048, 2006; Published online in Wiley Inter-Science (www.interscience.wiley.com). DOI 10.1002/mop.21842

Silicon bulk micromachined FBAR filters and duplexer have been developed. The proposed filters are comprised of several resonators and the duplexer is made with two filters and a phase delay line. The fabricated FBAR filters have insertion losses (IL) of −1.46 and −1.86 dB, return losses of −13 and −10 dB, stop band rejection of −14 and −33 dB, central frequency of 1.88 and 1.96 GHz, and size of 1.3 mm × 1.5 mm, respectively. The fabricated FBAR duplexer has insertion loss (IL) of −3.5 dB (Max.) in pass band and absolute attenuation of −42 dB (Min.) at transmitter to antenna ports, while it has IL of −4.5 dB (Max.) in pass band and absolute attenuation of −52 dB (Min.) at antenna to receiver ports. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 339–342, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22133

In this paper, novel microstrip open-loop resonator (OLR) bandpass filters are presented. By introducing additional spiral inductors as well as gap-coupled capacitors, the bandpass filters (BPFs) exhibit another attenuation pole at the upper stopband. Also, a novel miniaturized high-Q duplexer for Universal Mobile Telecommunications System (UMTS) bands using these BPFs is discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 69–72, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20904

A stepped-impedance resonator (SIR) bandpass diplexer using over-coupling structures and tapped input/output (I/O) has been presented. The advantages of this construction are simple design and suppression of spurious response at twice the center frequency (2f0). The tapped I/O creates an extra transmission zero in each filter of the duplexer in order to improve stopband attenuation. The diplexer, designed at 0.9 and 1.8 GHz, is suitable for mobile communication and is easily fabricated in the packing surface. Experimental results of the designed duplexer are in good agreement with the theoretical predictions and simulated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 79–82, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20215

In this paper, a compact planar microwave duplexer on a high-dielectric substrate is proposed. As Ba(Mg1/3Ta2/3)O3 (BMT) has good dielectric performances with a high-dielectric constant of er = 23, it is suitable for application on printed circuit boards for compact-size circuits. The BMT substrate is fabricated using a tape-casting process; then, metal patterns are screen-printed upon it and silver pasted. An open-loop ring-type duplexer is designed and implemented on the BMT substrate. A size reduction of about 80% is achieved without any degrading duplexer performances, compared with the same one fabricated on a commercial substrate (er = 6.15). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 251–253, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20108

Before a SAW filter is applied to the high-power section of a cellular radio portable phone, it is necessary to develop a higher-performance filter with a high-power capability and a small, nonlinear effect. In this paper, as a new type of filter, a SAW resonator coupled filter of an extended type is proposed which uses two types of piezoelectric substrates. A design method considering the impedance matching between the substrates is presented as well as the results of the experimental duplexer satisfying the specifications of the cellular radio portable phone for the United States. This filter has a third-order nonlinearity effect that results in the spurious response sensitivity much smaller than the conventional transversal type. These characteristics are almost identical to those for the present dielectric resonator duplexer for the forementioned use.

An integrated optical duplexer with three rib waveguides is investigated theoretically by a two-dimensional mode-matching technique with modal fields obtained by the method of lines. The results are compared with those of a one-dimensional analysis and show the range of applicability of the effective index method. An optimized duplexer for separation of the 1.3-μm band from the 1.55-μm band is only 290 μm long and has a 1-dB bandwidth of 0.15 μm. A complete one-dimensional mode expansion shows that radiation has no significant influence on the duplexer characteristics. They are also nearly independent of polarization.

High-power duplexer consisting of a four-port ferrite junction circulator and two-stage switched PIN diode limiter with appropriate driver circuit is designed and developed for a low-recovery-time requirement. Insertion loss of 1.5 dB, isolation of 70 dB and recovery time of 40 ns are achieved at a 10-KW peak, 200-ns pulsewidth at Ku band.