Search

This article presents the first demonstration of a full-waveguide feed at W-band, enabling transmit–receive duplexing and 2-D tracking of targets. The proposed device is a compact unit designed to be used as feed of a 94 GHz space-borne radar. Its duplexing concept relies on a septum orthomode transducer polarizer for transmitting and receiving sum signals with opposite circular polarizations. Additionally, the first higher order mode of circular waveguide (TM01) is allowed to propagate inside the device to extract a difference signal for tracking. By comparing received sum and difference signals in amplitude and phase, both angular directions of a target position can be derived. A prototype of the duplexer was fabricated and tested: measurements at 94 GHz show return loss and isolation above 23 dB at all ports, with reasonable performance from 92 to 96 GHz. The measured monopulse characteristic enables 2-D tracking of targets deviated by less than 8.5° from boresight. [ABSTRACT FROM AUTHOR]

This article presents a duplexing hybrid antenna architecture for short-range radar systems with high isolation and low loss between the two transmitting (TX) and receiving (RX) ports. The antenna utilizes a single slot for common resonance shared by the two TX and RX port excitations. These two ports were constructed through two parallel microstrip lines crossing over the specified shaped slot. The feeding structures of these two microstrip feedings and the separation are optimally designed to ensure the mutual coupling signals out-of-phase, and therefore, the signal cancellation can be achieved, leading to a high isolation between these two ports. In this design, the slot length is $0.92\lambda $ at 24.125 GHz, forming an equivalent short circuit at the other port. Given the initial design criteria, the design with the optimal isolation could readily be found by minimal full-wave simulations. Meanwhile, the equivalent circuit model was used to investigate the working principles and to improve the isolation bandwidth and impedance matching at the central frequency. The measured maximum isolation is 70 dB at 24.125 GHz. The RF front-end modules with TX and RX amplifiers are also integrated to validate its feasibility for the radar system application. The mechanisms to widen the isolation bandwidth are also addressed. [ABSTRACT FROM AUTHOR]

The quasi-elliptic multi-mode bandpass cavity filters and duplexer with slot mixed-coupling structure are proposed in this paper. A single metal cavity embedded with a rectangular- shaped slot-cut metal plate is utilized to constitute a multi-mode bandpass filter with a few features including wide passband, low profile and controllable transmission zeros (TZs). In this paper, the slot-cut metal plane serves as the multi-mode resonators. In detail, the slot on the metal plane functions as the circuit element to move the higher order modes within the reasonable frequency-band, while serving as a mixed-coupling structure to generate out-of-band transmission zeros. To demonstrate the multiple-mode capability in filter design, the dual-mode, triple-mode, and quadruple-mode filters are developed by appropriately allocating a few TZs in the upper stopbands using the proposed slot mixed-coupling approach, namely, Type-I filters. Next, a quadruple-mode cavity filter with both lower and higher TZs is designed, namely, Type-II filter, which is further applied for the exploration of a duplexer. Finally, the filter and duplexer prototypes are fabricated and measured. The measurement results are found in good agreement with the simulated ones.

In a scenario where the segment of wireless communication systems are allocated in an ever more crowded frequency spectrum, the design of filtering structures, stand-alone, duplexers, or multiplexers, become a challenging task. Moreover, filters based on acoustic wave resonators are the more suitable technology in this context due to the small size and the exhibited outstanding performance. However, to accommodate the technological requirements to the mask fulfillment is not straightforward unless a systematic synthesis methodology is used. Taking advantage on the nodal approach, the general synthesis methodology for ladder-type filters based on acoustic wave resonators is presented in this paper. This is a very fast procedure, which allow a better understanding of the interaction between technological constraints and filter performance. An experimental validation is proposed for a B28Rx band filter.

In this article, a body channel communication (BCC) transceiver (TRX) and low-power receiver (RX) that can cover wide applications are proposed. The IEEE 802.15.6 human body communication (HBC) physical layer (PHY) standard and high-speed data transmission are supported simultaneously with a single chip. First, the sinusoidal-modulated transmitter is proposed for the standard mode TRX, and it can reduce filtering power overhead 35%. Second, high-speed TRX is proposed that can support dual-band QPSK modulation to increase system data rate and bandwidth efficiency. Third, on-chip RC duplexer is proposed for full-duplex function in communication. Also, for the low-power RX, a wireless power transfer (WPT)-based wake-up receiver (WuRX) and a higher energy efficiency main RX is integrated into RX chip. The main HBC RX demodulates both ASK and frequency-shift keying (FSK) information with a sharing oscillator (OSC) with 31- $\mu \text{W}$ low-power consumption. The TRX and RX are implemented in 65-nm CMOS process. [ABSTRACT FROM AUTHOR]

This article describes the simulation analysis and experimental verification of a new type of high-isolation surface-acoustic wave (SAW) duplexer by using an SAW on-chip compensation circuit designed to cancel the leakage signal of the main SAW duplexer at multiple frequency bands. First, an analysis of amplitude and phase change of the SAW duplexer consists of a ladder-type transmitter (Tx) filter, and the double-mode SAW (DMS) receiver (Rx) filter is applied to clarify the cancellation conditions. Then, the feasibility of the SAW compensation circuit using a three-interdigital transducer (IDT) DMS resonator specially designed to satisfy the cancellation conditions is studied in circuit simulation based on the coupling-of-mode (COM) theory. Finally, we analyzed this concept in detail for a long-term-evolution (LTE) Band-I SAW duplexer for Tx and Rx band isolation in both a circuit simulation and experiment. Results showed that around 10-dB improvement of isolation in both the Tx and Rx bands was obtained without sacrificing other properties (e.g., insertion loss and attenuation) and that it agrees well with the result obtained by simulation analysis. These results are expected to be useful for now, considering that future mobile systems demand higher Rx sensitivity in multiple frequency bands. [ABSTRACT FROM AUTHOR]

This paper reports on the RF design of fully reconfigurable quasi-elliptic-type single- and multi-band microwave bandpass filters (BPFs) and duplexers. They are based on series-cascaded resonators and multi-resonant/multi-band cells that produce frequency-reconfigurable poles and transmission zeros (TZs). By appropriately tuning the resonant frequencies of their constituent resonators, multiple levels of transfer-function adaptivity can be obtained. These capabilities include center-frequency and bandwidth tuning, as well as intrinsic RF switching-off (i.e., without the use of RF switches). As opposed to conventional BPF tuning mechanisms, the aforementioned reconfiguration characteristics avoid the use of tunable couplings. The basic operating principles of the engineered resonator-cascade BPF concept are presented through a three-pole/two-TZ example. Afterward, methods for expanding the proposed filter design approach to higher order, multi-band, and multi-port (e.g., duplexers) realizations are explained through coupling-matrix-based analysis. For practical-demonstration purposes, four L-band tunable microstrip prototypes were developed and measured. They include: 1) a five-pole/four-TZ BPF; 2) a five-pole/two-TZ BPF; 3) a dual-band BPF with two three-pole/two-TZ passbands; and 4) an RF duplexer. [ABSTRACT FROM AUTHOR]

In this paper, a novel triplexer using the substrate-integrated suspended line technology is proposed. Two matching circuits are designed to connect the three filter channels for the triplexer construction. The used bandpass filters are composed of a low-pass filter and a high-pass filter, and they have advantages of high controllability and low insertion loss. For the proposed triplexer, two adjacent filter channels compose a duplexer. Based on the design consideration, the triplexer can be extended to a multiplexer. The proposed design is further improved by using a patterned suspended substrate for loss reduction. The triplexer achieves good isolations among the three ports and low insertion losses of 1.4/1.3/0.8 dB for the three channels of 0.8, 2.5, and 5.8 GHz, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a novel, tunable, frequency-division duplexing radio frequency (RF) front end that combines passive and active self-interference (SI) cancellation. An electrical-balance duplexer is used to passively cancel transmitter noise in the receive band, and an active canceller is employed to suppress SI in the transmit (Tx)-band. Subsystem specifications are developed, and a system-level analysis of noise and SI powers in this novel architecture is provided, thereby illustrating its operation. A proof-of-concept demonstrator, built from a software-defined radio and discrete RF components, has been characterized across a range of duplex configurations in the 700–950-MHz range and also at 1900 (Long-Term Evolution (LTE) band 3) and 2600 MHz (LTE band 7). The prototype achieves an impressive 6.0–7.4-dB noise figure in the presence of a +27-dBm LTE uplink Tx blocker for duplex separations of 47.5 MHz and above. The duplexer has also been tested against reference sensitivity test cases defined in the 3GPP LTE specification, demonstrating specification compliant sensitivity in LTE bands 28 (700 MHz), 3, and 7. [ABSTRACT FROM AUTHOR]

In this paper, a highly integrated frequency-modulated continuous-wave (FMCW) radar system with a single-antenna interface for range sensing is proposed. In this paper, a circulator structure was developed and used in the radar system with the single-antenna interface. This structure capitalizes on frequency orthogonality to separate transmitted and received signals; thus, the isolation can be improved by using integrated filters to further suppress transmitter leakage. Without an additional back-end leakage cancellation mechanism and antenna tuner, the single-antenna FMCW radar system can be devised. The proposed system is composed of a radar transceiver, a frequency synthesizer, an analog signal processor, and an AD converter; the system is fabricated using a 65-nm CMOS technology, occupies a chip area of 1.9 mm2, and consumes 147-mW dc power under a 1.2-V power supply. The implemented front-end circuit can provide an output power of 10.5 dBm with power efficiency of 30%, over 1-GHz impedance matching, an insertion loss of 2 dB, a maximum noise figure of 16.8 dB (including the following IF amplifier), $P_{1\,\text {dB}}$ of 2 dBm, and IIP3 of 7 dBm. A wireless measurement process proved that the system can provide a 37-cm range resolution over a 50-m range for a $20 \times 20$ cm2 copper plate. Finally, an FMCW radar front-end board and a digital signal processing board were implemented for data analysis, thus completing the FMCW radar sensor unit. The proposed system can be utilized for multiple applications including 1-D object tracking, 2-D localization, and 3-D object tracking. [ABSTRACT FROM AUTHOR]

A highly integrated three-state diplexer (TSD) on a single planar elliptical structure is for the first time presented in this paper. Three resonant modes are investigated in a planar elliptical resonator, e.g., two TM11 degenerate modes and one TM21 mode. These three resonant modes are designed to form three filtering channels, which are further combined to generate three states of a diplexer, namely, TSD. The planar elliptical triple-mode resonator is fed by three microstrip lines to form a triple-mode TSD. In order to validate the concept, the designed planar TSD is fabricated and measured. The measured results are in good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

In cellular communications certain frequency bands are licensed to specific applications guaranteeing predictability and reliability of service quality. Undesirable interference from these bands have to be removed by high-quality passive filters. This paper introduces a novel measurement method to determine the frequency response of a cellular system related to these passive filters. The method is based on in situ BER measurements and does not require access to the components of the transceiver hardware or knowledge about components and implementation. It is nondestructive and can be applied as in situ measurement of any wireless modem during normal operation. The results are successfully verified against direct S-parameter measurements of the SMT components. [ABSTRACT FROM PUBLISHER]

Linear, time-invariant, passive circuits and systems constructed from conventional materials with symmetric permittivity and permeability tensors are reciprocal. Breaking Lorentz reciprocity enables the implementation of non-reciprocal components, such as gyrators, isolators, and circulators, which find application in numerous wireless communication systems. Non-reciprocal components are traditionally implemented using ferrite materials, which exhibit the Faraday effect under the application of an external magnetic field bias. However, ferrite materials cannot be integrated into CMOS fabrication processes and require an external biasing magnet, and hence are bulky and expensive. Recently, there has been significant research interest in the implementation of non-magnetic non-reciprocal components using temporal modulation, including a fully integrated 25-GHz circulator in a 45-nm SOI CMOS, demonstrating magnetic-free passive non-reciprocity on silicon at millimeter waves for the first time. This paper presents a detailed analysis of the millimeter-wave circulator in both time and frequency domains. Millimeter-wave non-reciprocal operation is enabled by the concept of spatio-temporal conductivity modulation, which achieves broadband non-reciprocal gyrator functionality over theoretically infinite bandwidth (BW). When compared with prior approaches based on N-path filters, spatio-temporal conductivity modulation requires only four-phase 50% duty-cycle clocking at frequencies significantly lower than the operation frequency, enabling scaling to millimeter waves. The 25-GHz circulator achieves minimum transmitter (TX)-to-antenna (ANT)/ANT-to-receiver (RX) insertion losses of 3.3 dB/3.2 dB, respectively, with a 1-dB BW of 4.6 GHz. TX-to-RX isolation is 18.3–21.2 dB (limited by the measurement setup) over the same BW. The circulator IC occupies an area of 1.2 mm $\times $ 1.8 mm ( $\lambda /8 \times \lambda $ /6). The spatio-temporal conductivity modulation concept is readily scalable across frequency and can be an enabler for higher millimeter-wave (e.g., 77 GHz) circulators as well as optical isolators. [ABSTRACT FROM AUTHOR]

This paper presents the design consideration on a converged Rx surface acoustic wave (SAW) duplexer module for integrated RF front end. Two different matching-circuit and notch-circuit configurations were examined with importance placed on electrical characteristics (insertion loss and isolation of duplexer) and simplification of module, respectively. From circuit simulations and examinations, we verified that a simplified design was best in terms of both characteristics and space in the case of a finite inductor's Q. We also fabricate a quad-band converged Rx module (Band I + II, V + VIII) using an SAW duplexer and verified that its electrical characteristics agree well with our simulation results. [ABSTRACT FROM AUTHOR]

A class of frequency-reconfigurable input-reflectionless/absorptive RF/microwave filters is presented. They consist of tunable complementary-duplexer architectures that are composed of a main and an auxiliary channel with opposite filtering transfer functions. By loading the auxiliary channel with a reference-impedance resistor and by taking the output node of the main channel as the output terminal of the overall circuit, a filtering network of the same type of the main channel with theoretically perfect input-reflectionless behavior at all frequencies can be realized. This technique can be applied to design spectrally agile completely input-reflectionless filters with any kind of transfer function, such as low-pass, high-pass, and single/multiband bandpass/bandstop filters. The theoretical analysis of the first-order absorptive bandpass/bandstop filtering sections based on a coupling-matrix formulation is detailed. Furthermore, the synthesis of high-selectivity reflectionless filters either by cascading multiple first-order cells or using high-order channels in a single complementary duplexer is also described. For practical-demonstration purposes, frequency-tunable lumped-element and microstrip prototypes are manufactured and characterized. They correspond to first- and second-order bandpass/bandstop filters. In addition, their in-series cascade connection is used to implement a bandpass filter with spectrally controllable passband and out-of-band notches. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive RF front-end (RFFE) architecture that uses an electrical-balance duplexer (EBD) and tuned surface acoustic wave (SAW) resonators to enable adaptive dual-frequency isolation suited for LTE's frequency-division duplex (FDD) mode of operation. Alternatively, in the in-band full-duplex (IBFD) mode, the EBD cancels the in-band TX self-interference directly at RF for increased channel capacity. Furthermore, the EBD's balance network is optimized to reduce the TX insertion loss (IL) below the nominal 3-dB limit in the FDD mode. A 0.18-μm SOI CMOS prototype implements the EBD, low-noise amplifier, and SAW-tuning capacitor banks. The chip is mounted to a module substrate together with the SAWs and matching components. The RFFE achieves >50-dB dual-frequency isolation and 2.6-3.4-dB TX IL in FDD mode, has +58/+42-dBm TX/RX-path IIP3 for an increased IBFD-link budget and handles up to +27.5-dBm TX power in both modes. [ABSTRACT FROM AUTHOR]

To develop the high-performance filters and duplexers required for recent long-term evolution frequency bands in mobile handsets, a surface acoustic wave (SAW) resonator is needed that has a higher quality (Q) and a lower temperature coefficient of frequency (TCF). To achieve this, the authors focused on acoustic energy confinement in the depth direction for a rotated Y-X LiTaO3 (LT) substrate. Characteristics of multilayered substrates with low-impedance and high-impedance layers under LT layer were studied numerically in terms of acoustic energy distribution, phase velocity, coupling coefficient, and temperature characteristics employing a finite-element method simulation. After several calculations, a novel multilayered structure was developed that uses SiO2 for a low-impedance layer and AlN for a high-impedance layer under the thin LT layer. A one-port resonator using the new substrate was fabricated, and its experimental results showed that the developed resonator had a Bode-Q over 4000 and TCF of −8 ppm/°C, which are four times higher than and one-fifth as small as those of a conventional 4° YX-LT SAW resonator, respectively. By applying this technology, a band 25 duplexer with very narrow duplex gap was successfully developed, which shows extremely low insertion loss, steep cutoff characteristics, and stable temperature characteristics. [ABSTRACT FROM AUTHOR]

Today, acoustic filters are the filter technology to meet the requirements with respect to performance dictated by the cellular phone standards and their form factor. Around two billion cellular phones are sold every year, and smart phones are of a very high percentage of approximately two-thirds. Smart phones require a very high number of filter functions ranging from the low double-digit range up to almost triple digit numbers in the near future. In the frequency range up to 1 GHz, surface acoustic wave (SAW) filters are almost exclusively employed, while in the higher frequency range, bulk acoustic wave (BAW) and SAW filters are competing for their shares. Prerequisites for the success of acoustic filters were the availability of high-quality substrates, advanced and highly reproducible fabrication technologies, optimum filter techniques, precise simulation software, and advanced design tools that allow the fast and efficient design according to customer specifications. This paper will try to focus on innovations leading to high volume applications of intermediate frequency (IF) and radio frequency (RF) acoustic filters, e.g., TV IF filters, IF filters for cellular phones, and SAW/BAW RF filters for the RF front-end of cellular phones. [ABSTRACT FROM AUTHOR]

Although there is much active research on software-defined radios (SDRs) with receive (RX) or transmit (TX) functionality, little work has been done on SDR transceivers supporting frequency division duplex (FDD). In this paper, we present a new circuit concept in which a distributed TX circuit cancels the transmitted signal at a reverse RX port through destructive interference while adding signal constructively at a forward TX port. We pair the distributed transmitter with a receiver-tracking PA degeneration technique to suppress the injected noise from TX circuits in the RX band. The system does not require off-chip filters or circulators, but still achieves both SDR flexibility and both FDD and time division duplex function. Measurements from the transceiver implemented in 65-nm CMOS show a frequency tuning range of 0.3–1.6 GHz with TX–RX isolation >23 dB and transmitted power up to 19 dBm. [ABSTRACT FROM AUTHOR]

We present a mixer-duplexer-antenna leaky-wave system based on periodic space-time modulation. This system operates as a full transceiver, where the upconversion and downconversion mixing operations are accomplished via space-time transitions; the duplexing operation is induced by the nonreciprocal nature of the structure, and the radiation operation is provided by the leaky-wave nature of the wave. A rigorous electromagnetic solution is derived for the dispersion relation and field distributions. The system is implemented in the form of a spatio-temporally modulated microstrip leaky-wave structure incorporating an array of subwavelengthly spaced varactors modulated by a harmonic wave. In addition to the overall mixer-duplexer-antenna operation, frequency beam scanning at fixed input frequency is demonstrated as one of the interesting features of the system. A prototype is realized and demonstrated by full-wave and experimental results. [ABSTRACT FROM PUBLISHER]

A switchable and tunable bulk acoustic wave (BAW) duplexer for RF applications is presented in this paper. The fabricated BAW duplexer was built on sapphire substrate using solidly mounted resonators. A metal-organic solution deposition technique was used to form resonators with barium strontium titanate (BST) thin film and six layers of silicon dioxide and tantalum oxide as Bragg reflector. By applying dc bias, the BST thin film shows an electrostrictive effect, and the two filter paths of the BAW duplexer switch to a bandpass response with center frequencies at 4.635 and 4.878 GHz, showing a bandwidth of 119 and 154 MHz for the transmitting (Tx) and receiving (Rx) filters, respectively. Further, the BAW duplexer was simulated using the circuit, Butterworth-van-Dyke, and electromagnetic models. The simulated results are in agreement with the measurements and show the response of bandpass filters at center frequencies of 4.633 and 4.876 GHz for Tx and Rx, respectively. [ABSTRACT FROM PUBLISHER]

An electrical-balance duplexer achieving the state-of-the-art linearity and insertion loss (IL) performance is presented, enabled by a partially depleted RF silicon-on-insulator CMOS technology. A single-ended configuration avoids the common-mode isolation problem suffered by topologies with a differential low-noise amplifier. Highly linear switched capacitors allow for impedance balancing to antennas with <1.5:1 voltage standing wave ratio from 1.9 to 2.2 GHz. +70-dBm input-referred third-order intercept point is achieved under high transmitter (TX) power (+30.5 dBm max.). TX IL is <3.7 dB, and receiver IL is <3.9 dB. [ABSTRACT FROM PUBLISHER]

A dual-band CMOS duplexer employing a switchable autotransformer is proposed for highly integrated RF front ends in mobile phones. Because on-chip switches are used to change the length of the autotransformer, the inductance is sized for two different frequency ranges. It is designed to support both low-band (LB) mode from 0.7 to 0.9 GHz and mid-band (MB) mode from 1.7 to 2.0 GHz for cellular applications. With different inductances for LB and MB modes, transmitter (TX)-to-receiver (RX) isolation is achieved by using two separate balance networks for LB and MB. The duplexer is implemented in a 65 nm CMOS process. In LB mode, TX and RX insertion losses (ILs) are less than 4.3 dB, while TX-to-RX isolation is more than 50 dB. In MB mode, TX IL and RX IL are less than 4.5 dB, while TX-to-RX isolation is more than 50 dB. The proposed duplexer proves feasible structure to cover both LB and MB frequency ranges in cellular 3G/4G applications. [ABSTRACT FROM AUTHOR]

This paper proposes a novel concept of an integrated duplex antenna for realizing a compact multifunction RF front end by integrating a duplexer and a dual-band patch antenna. First, an all-resonator-based duplexer is designed. It is composed of two sets of split-ring resonators as channel filters, which are joined by a dual-mode stub-loaded resonator as the junction resonator. Then, a novel dual-band patch antenna is achieved by coupling a patch with a hairpin resonator through a slot in the ground. Uniform radiation characteristics have been achieved across the two bands. Finally, the duplexer is integrated with the dual-band patch antenna to form a highly integrated duplex antenna by coupling the hairpin resonator to the junction resonator of the duplexer directly. In this process, the 50- $\Omega $ interface and matching network between them are removed, contributing to a compact footprint. The details of codesign approach have been discussed in this paper. Compared with the traditional cascaded duplexer and antennas, this paper is much more compact and integrated but with an improved frequency response. A prototype of an integrated duplex antenna at S-band is fabricated and measured, showing two operation channels of 2.52–2.65 GHz for transmitting and 2.82–2.94 GHz for receiving with an isolation of over 32 dB. The measured results agree well with the simulation results. [ABSTRACT FROM PUBLISHER]

This paper presents a millimeter-wave tunable hybrid-transformer-based duplexer concept with dual-antenna configuration. By using orthogonal sequentially-rotated linearly-polarized antennas and the hybrid-transformer-based duplexer, the transmitter and receiver duplexes the two antennas with orthogonal circular-polarized signals. An on-chip tuning technique using magnetic coupling is introduced to improve the isolation of the duplexer in case of impedance imbalances. An alternative duplexer with a similar principle using an on-board rat-race coupler is also proposed and designed for comparison. In order to demonstrate the isolation with practical antenna connections, prototypes have been developed to integrate the on-chip duplexer and the rat-race coupler with on-board aperture-coupled microstrip antennas with sequential rotation technique. Measurement results demonstrate the orthogonal circular polarizations for the receiver and transmitter modes on both prototypes. The achieved isolation by the on-chip tunable duplexer is better than 50 dB between 30.2 and 31.2 GHz, while the achieved isolation by the rat-race version is about 20 dB in the same bandwidth. [ABSTRACT FROM AUTHOR]

A low-energy 40/160 MHz dual-band full duplex body channel communication (BCC) transceiver and a 13.56 MHz R-C oscillator-based super-regenerative transceiver are integrated in 65 nm CMOS mixed mode process for both entertainment and healthcare applications. The on-chip R-C duplexer uses notch filters for full duplex communication with 40 Mb/s data rate and combined dual-band operation shows 80 Mb/s data rate with half duplex communication. 40 MHz sine wave and 160 MHz rectangular wave are adopted for modulation in the dual-band transmitter with 30 dB SNR improvement, and shared-loop BPSK receiver reduces the power consumption by 25%. The proposed super-regenerative transceiver including an OOK transmitter and an R-C oscillator-based receiver achieves >60\,\textdB interference rejection with 100 kb/s data rate and 42.5\,\upmu\textW power consumption under the 0.8 V supply. [ABSTRACT FROM PUBLISHER]

A method to design quasi-elliptic-type multiplexers without cross coupling in its channelizing bandpass filters is reported. It is based on the use of a multi-transmission-zero (TZ)/multipole filtering cell in the junction of the multiplexer channels. This filtering cell increases the orders of the multiplexer channels by one in relation to the isolated filters, whereas its TZs are shared by all channels. In this manner, an enhanced order sharp-rejection multiplexer can be synthesized. The operational foundations of the proposed quasi-elliptic-type multiplexer approach, which is general for symmetrical and asymmetrical arbitrary-order designs in any RF technology, are described under a coupling-matrix-based formalism. Moreover, for practical-validation purposes, a third-order microstrip duplexer prototype with channels centered at 2.15 and 2.65 GHz is manufactured and tested. [ABSTRACT FROM AUTHOR]

A compact 680-GHz waveguide orthomode transducer (OMT) and circular horn combination has been designed, tested, and characterized in a radar transceiver's duplexer. The duplexing capability is implemented by a hybrid waveguide quasi optical solution, combining a linear polarization OMT and an external grating polarizer. Isolation between the OMT's orthogonal ports' flanges was measured with a vector network analyzer to exceed 33 dB over a >10% bandwidth between 630 and 710 GHz. Calibrated Y-factor measurements using a mixer attached to the OMT ports reveal losses through the transmit and receive paths that sum to an average of 4.7 dB of two-way loss over 660–690 GHz. This is consistent with radar sensitivity measurements comparing the new OMT/horn with a quasi-optical wire grid beam splitter. Moreover, the radar performance assessment validates the OMT as a suitable compact substitute of the wire grid for the JPL's short-range 680-GHz imaging radar. [ABSTRACT FROM AUTHOR]