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This paper proposes an innovative design approach for a voltage‐controlled (variable) attenuator that allows continuous control of attenuation through analog voltage. Different from fixed attenuators, this work employs PIN diodes and compensated gold wire inductors to configure the attenuation network. It is based in imperfect matching theory, ensuring to obtain the acceptable S‐parameters over the operating band. Measurement results demonstrate effective performance of the attenuator within the voltage range of 0.7–1.03 V. Return losses of the attenuator are all better than 15 dB in the operating range of 10.5–19 GHz. The insertion losses exhibit continuous variation from 2 to 15 dB, requiring only a single controlled voltage to adjust the attenuation value. [ABSTRACT FROM AUTHOR]

In this letter, a novel design of electrically tunable substrate integrated waveguide (SIW) equalizer, based on PIN diodes, is proposed. Compared to previous SIW equalizers, this one introduces PIN diodes that exhibit varying impedance under different direct current (DC) voltages. The equalizing values of the SIW equalizer are directly linked to the DC voltage applied to the PIN diode within a specific voltage range. This feature allows it to be considered as an electrically tunable SIW equalizer. The experimental results demonstrate that the equalizing values are consistently monotonic and adjustable within the range of 1.59–7.56 dB in Ku‐band. This adjustment is attained through a DC voltage step of −0.01 V, applied within the range of 1.23–1.11 V. Additionally, the microwave equalizer is a planar structure that can be conveniently implemented on traditional printed circuit board, resulting in lower costs, easier realization, and integration. This SIW equalizer can be applied in amplitude compensation circuits and networks to compensate flatness dynamically. [ABSTRACT FROM AUTHOR]

In this paper, a wideband reflectometer based on six-port technology is presented. The designed six-port junction is built by using a modified ring power divider and three identical 90-degree hybrid couplers. The main difference from its initial application as a conventional six-port reflectometer is the addition of a fourth qi point. Here, the four power detectors are used to find the reflection coefficient (4 qi points) and a fifth detector is added as a reference. To simplify the fabrication process and minimize the cost, the six-port circuit is designed on a single-layer PCB. The measured results of the six-port junction reveal high performance over a large frequency band from 2.2 to 3.55 GHz. In order to evaluate its performance for real-time measurements, the proposed six-port reflectometer is then tested by measuring the reflection coefficient of different devices under test (DUTs). The measured results are then corrected by a simplified calibration method to have optimal results. Compared to conventional six-port calibration methods, the proposed calibration process is simple and allows accurate reflection coefficient measurements. After calibration, there is a great improvement in the corrected results of the reflection coefficient compared to the measured results which proves that the calibration process works perfectly from 2.6 to 3.8 GHz. [ABSTRACT FROM AUTHOR]

A six-port K [alpha]-band front-end architecture based on direct conversion for a software-defined radio application is proposed in this paper. The direct conversion is accomplished using six-port technology. In order to demodulate various phase-shift-keying/quadrature-amplitude-modulation (PSK/QAM) modulated signals at a high bit rate, a new analog baseband circuit was specially designed according to the I/Q equations presented in the theoretical part. An experimental prototype has been fabricated and measured. Simulation and measurement results for binary PSK, quaternary PSK (QPSK), 8 PSK, 16 PSK, and 16 QAM modulated signals at a bit rate up to 40 Mb/s are presented to validate the proposed approach. A software-defined radio can be designed using the new front-end and only two analog-to-digital converters (ADCs) because the I/Q output signals are generated by analog means. Previous six-port receivers make use of four ADCs to read the six-port dc levels and require digital computations to generate the I/O. output signals. With the proposed approach, the load of the signal processor will therefore be reduced and the modulation speed can be significantly increased using the same digital signal processor. Index Terms--Direct conversion, front-end, phase-shift keying (PSK), quadrature amplitude modulation (QAM), six-port.

A new direct-conversion wide-band (26-28.5 GHz) six-port receiver is proposed for mass-market wireless communications. This six-port receiver is designed to operate without the need for precise power reading and the use of a digital signal processor that is usually required in other receivers. The proposed receiver architecture is chosen to satisfy requirements of hardware receivers used in high-speed QPSK communications. The receiver contains a receiver front-end, QPSK demodulator, and carrier recovery module. A reverse modulation loop was used to provide a rapid carrier recovery. The maximum bit rate is determined solely by the limiting speed of the baseband module. This new hardware receiver is proposed as a robust, rugged, low-cost receiver for use in wide K a-band wireless mass-market QPSK communications such as local multipoint distribution system services, which is a prime example of communication equipment requiring such receivers. Bit-error-rate results are presented versus the noise and reference signal phase shift. Index Terms--Carrier recovery, direct conversion, monolithic-microwave integrated-circuit (MMIC) technology, QPSK modulation, six-port junction.

A new direct-conversion wide-band (23-31 GHz) six-port receiver is proposed suitable for millimeter-wave integrated system design. This new hardware receiver is found to be robust, rugged, low cost, and suitable for use in broad-band wireless mass-market QPSK communications. The prototype circuits are fabricated to validate this new concept with our miniaturized hybrid microwave integrated-circuit technology and the proposed receiver topology is also suitable for monolithic-microwave integrated-circuit fabrication. This application-specific integrated receiver is designed on the basis of a wide-band six-port junction and other analogical circuits in the form of a simple multichip module. Bit-error-rate measurements and simulation results are shown and discussed in the presence of noise, adjacent signal interference, local-oscillator (LO) phase shift, and LO phase noise. The maximum bit rate is fundamentally limited by the speed of the video and decoder circuits. Nevertheless, several hundred megabits per second can be achieved at low cost. Index Terms--Homodyne receiver, MHMIC technology, millimeter wave, QPSK modulation, six-port junction.

The study has presented an extensive analysis of an integrated millimeter wave six-port interferometer, operating over a 10 GHz band, from 80 to 90 GHz. It has covered both semi-unlicensed point-to-point links (81-86 GHz), and imaging sensor system frequencies (above 85 GHz). An in-house process is used to fabricate miniaturized hybrid millimeter wave integrated circuits on a very thin ceramic substrate. Two-port S-parameter measurements are performed on a minimum number of circuits integrated on the same die, exploiting the circuit’s physical symmetry and chosen to collect enough data for full-port characterization. Based on these measurements on an integrated prototype, a six-port circuit computer model was implemented and advanced system simulations was performed for circuit analysis. Interferometer performances evaluated using several methods: analysis of harmonic balance, qi points’, homodyne quadrature demodulation, and error vector modulation (EVM). The analysis showed that this circuit could directly perform, without any calibration, the demodulation of various PSK and QAM signals over the 10 GHz band, with very good results. [ABSTRACT FROM AUTHOR]

In this Letter, a novel empty substrate-integrated waveguide (ESIW) phase inverter (PI) applied in millimetre-wave has been proposed. ESIW PI, based on the structural symmetry design, is made of four parts: top cover, middle layer, ESIW PCB, and bottom layer. Owing to the reversed-phase transmission channel, the phase difference between the two outputs is absolutely equal to 180°. The simulation and measurement results are in a good agreement. In the entire Ka band, the return losses, insertion losses and amplitude imbalance of ESIW PI are better than 12.7, 2.66, and 0.64 dB ± 0.6 dB, respectively. Besides, the phase difference is within 180.5° ± 2.9° in the same frequency band. In addition, the input and output ports are located in the identical circuit plane, which is easy to integrate with other devices and components. [ABSTRACT FROM AUTHOR]