Maximum Phase Imbalance Research Articles

Integrated-Designs of Filtering Circuits Based on Adjustable Dielectric Waveguide Resonators

This brief presents a new kind of adjustable dielectric waveguide resonator (DWR), based on which integrated designs of filtering circuits are conducted. The DWR is composed of a dielectric part as the main resonating body and a printed circuit board (PCB) part as the cover. An unmetallized blind hole is carved at the upper surface of the dielectric part. A tuning screw is installed on the PCB and inserted into the unmetallized blind hole to adjust the resonant frequency the DWR. This adjusting method is flexible and reversible. By using the proposed adjustable DWR, a fourth-order bandpass filter (BPF) is designed, fabricated and measured. The measured results show that the BPF is with an in-band insertion loss of 0.8 dB and an in-band return loss better than 19 dB. A capacitive cross coupling structure is constructed on the PCB so that two transmission zeros are introduced close to the passband to improve the filtering selectivity. In addition, a Wilkinson power divider is realized on the PCB and integrated with the above BPF, forming a filtering power divider. The measured in-band insertion loss of the filtering power divider is 1.1 dB. The isolation is better than 24 dB and the maximum phase imbalance is 1° in the passband.

Broadband Beam-Forming Circuit Using Microstrip Multilayer Couplers

Multipath antenna arrays require broadband small-sized beam-forming circuits for their implementation. For Butler matrix circuits implemented by means of directional couplers, the models have been developed of the broadband power tap devices using coupled lines. However, as a rule, the current topologies feature relatively large amplitude imbalance within the working frequency band. In order to reduce the flatness of both the working attenuation and the transient attenuation, a microstrip topology of the multilayer directional coupler is introduced using coupled lines. Distinctive feature of this topology is the uncommon configuration of the coupling aperture. The coupling aperture shape is optimized within the 4-8 GHz frequency band according to the criterion of the minimum deviation of the amplitude-frequency characteristics from the ideal values. Within the octave band, the developed coupler features the flatness of the working attenuation and the transient attenuation of 0.6 dB as well as the phase imbalance equal to 1.2°. The maximum overall size of the coupler topology does not exceed a quarter of the wavelength. A four-beam beam-forming Butler circuit based on this coupler is presented. The results of both electrodynamic simulation of the circuit and the experimental studies of the mock-up produced are also demonstrated. It is determined that they are in good agreement with each other. The experimental values of the transient droop and the working attenuation of the matrix circuit deviate from the level of 6 dB by no more than 2.5 dB. The maximum phase imbalance does not exceed 8° from the nominal value.

Ultrawide Bandwidth 180°-Hybrid-Coupler in Planar Technology

A new concept of an ultrawide bandwidth 180°-hybrid-coupler is presented. The ultrawideband design approach is based on the excitation of a coplanar waveguide (CPW) mode and a coupled slot line (CSL) mode in the same double slotted planar waveguide. The coupler is suitable for realization in planar printed circuit board technology. For verification of the new concept a prototype was designed for the frequency range from 3 GHz to 11 GHz, built, and measured. The measurement results presented in this paper show a good agreement between simulation and measurement and demonstrate the very broadband performance of the new device. The demonstrated coupler with a size of 40 mm × 55 mm exhibits a fractional bandwidth of 114% centered at 7 GHz with a maximum amplitude imbalance of 0.8 dB and a maximum phase imbalance of 5°.

Superconducting 4–8-GHz Hybrid Assembly for 2SB Cryogenic THz Receivers

We present here the design and characterization of an intermediate frequency (IF) assembly comprising a compact 90° hybrid chip (coupled line coupler - Lange coupler- coupled line coupler), two bias-T circuits for biasing the superconductor-insulator-superconductor (SIS) mixers, and two transmission-line circuits. Specifically, the miniaturized three-section hybrid chip fabricated using thin-film technology utilizes superconducting Niobium (Nb) transmission lines, air bridges to connect the fingers of the Lange coupler (middle section), and is complemented with two bias-T circuits with integrated MIM capacitors. The assembly was designed to ensure amplitude and phase imbalances better than 0.6 dB and ±2°, respectively. Experimental verification of the assembly at 4 K shows good agreement between the measurements and simulations with amplitude imbalance of 0.5 dB and maximum phase imbalance of ±2°. The ALMA band-5 (163-211 GHz) receiver will include such assembly. The receiver tests shows sideband rejection ratio better than 15 dB over the entire RF band, i.e., a systematic improvement of 3-9 dB as compared with the previously reported results.

A Parallel-Strip Balun for Wideband Frequency Doubler

A parallel-strip phase inverter with a pair of simple impedance matching networks is designed. The phase inverter introduces the almost frequency independent 180° phase shift and was employed in the wideband parallel-strip balun. The balun was designed and measured with the maximum magnitude imbalance of 0.5 dB and the maximum phase imbalance of 6.0°. The proposed balun is used as input network for the wideband balanced frequency doubler. The proposed frequency doubler achieves significant conversion gain from 0.1 GHz to 1.7 GHz. The frequency doubler achieves 7.4 dB conversion gain and 23 dB fundamental signal suppression at 1 GHz.

Superconducting 4–8 GHz IF Hybrid for Low Noise mm-Wave Sideband Separation SIS Receiver

We present the design and performance of a superconducting 90° hybrid covering a full octave bandwidth from 4 to 8 GHz. The hybrid is designed using the Lange coupler layout. The novel features of this quadrature hybrid include superconducting niobium (Nb) transmission lines, air bridges to connect the fingers of the coupler and a bias-T integrated with the coupler. Our simulations indicate that the amplitude imbalance of the designed hybrid is less than 0.8 dB over the entire 4-8 GHz band with negligible phase imbalance. Experimental verification of the hybrid at 4 K, shows very good agreement between the simulations and the measurement results. The measured amplitude imbalance of the hybrid is less than 0.8 dB over 98% of the band and the maximum phase imbalance is ±4 degrees.

Uniplanar bridgeless CPW-to-slotline transition and its application to CPW balun

A new coplanar waveguide (CPW)-to-slotline transition that is uniplanar and bridgeless is presented. The transition consists of a CPW cross and CPW stubs in which both the even and odd modes are utilised. Based on this transition a uniplanar bridgeless CPW balun has been designed and fabricated. The fabricated balun has 1 dB insertion loss, 0.8 dB maximum amplitude imbalance, 4° maximum phase imbalance and 56% fractional bandwidth. Measurements are in a good agreement with simulations.

An Ultra-Wideband Balun Using Multi-Metal GaAs MMIC Technology

In this paper, we demonstrate an ultra-wideband MMIC Marchand balun that utilizes a two-layer benzocyclobutene (BCB) GaAs MMIC process with a total of 4 metal layers. This multi-metal technology is built upon a standard GaAs HEMT technology with full compatibility. The fabricated balun achieved an approximately 11:1 bandwidth from 2 to 22 GHz, with less than 3-degree maximum phase imbalance, and less than 1 dB maximum amplitude imbalance. To our knowledge, this is the largest bandwidth ratio ever reported for an MMIC Marchand balun.

Wide-band reduced-size uniplanar magic-T, hybrid-ring, and de Ronde's CPW-slot couplers

New reduced-size uniplanar magic-T and hybrid-ring coupler suitable for MIC's and MMIC's have been developed using a CPW-slotline ring that is 20% smaller than comparable designs. These circuits provide good amplitude and phase characteristics over a broad bandwidth. Experimental results show that the hybrid-ring coupler has a 1.3 octave bandwidth centered at 4 GHz and the magic-T has a bandwidth of 1.6 octave from 2-6 GHz. Both have a maximum power dividing imbalance of 0.4 dB and a 2.5/spl deg/ maximum phase imbalance. Also a new uniplanar de Ronde's CPW-slot directional coupler was developed with good performance. The even-odd mode analysis of four-port networks with double symmetry was used to analyze this coupler. A de Ronde's coupler with 5 dB coupling was designed and demonstrated over the frequency range of 2.4-3.4 GHz. The measurement results agree with the theoretical design.