Six-port Technology Research Articles

A Ka-Band Integrated Six-Port Chip for Analog Complex Correlator.

Six-port technology has been widely used in microwave systems, such as interferometric passive imaging. In this paper, an integrated Ka-band (32–36 GHz) six-port chip based on the 0.15-μm GaAs technology is designed and fabricated to simplify the circuit structure and miniaturize the volume of the imaging system. The designed chip integrates two amplifiers, two phase shifters, and a six-port circuit as part of an analog complex correlator. In this integrated chip, the crosstalk between the two amplifiers cannot be ignored. This paper analyzes the influence of the isolation between two amplifiers on the correlation results to guide the six-port chip design. In addition, considering that the radiometer system receives a broadband noise signal, the phase shifter needs to ensure that the phase shift range of each frequency point is the same under the same control conditions. Therefore, the phase shifter is designed with a high-pass and low-pass structure. The measurement results show that the isolation between the two amplifiers is greater than 20 dB, and the measured phase shift range and phase shift range error of the designed chip are 220° and 10°, respectively, with the control voltage varying from 0 to 1.5 V, which meets the requirements of the system.

Free-Space Transmission Dielectric Properties Measurement Based on Six-Port Technology

A six-port technology operating in transmission mode was developed for accurate determination of dielectric properties of low-loss materials from space measurements. The transmission coefficient was obtained by using the ratio of incident waves at ports 1 and 2 of the six-port network, while the power readings were performed at ports 3-6 simultaneously. The incident wave at port 1 originated from a forward propagating electromagnetic wave passing through the material sample. The incident wave at port 2 was the reference signal related to the incident wave at port 1 before or after propagating through the material. The calibration function is developed. The proposed six-port measurement technique was demonstrated at 5.8 GHz for purpose of verification. The material sample was placed between transmitting and receiving antennas. The microwave signal from the oscillator was fed to the transmitting antenna. The receiving antenna collected the signal and sent it to port 1. Two configurations were set up at port 2, either connected to the microwave signal from the oscillator or terminated with an electrical load. Magnitude and phase measurement results for various thicknesses of dielectric slabs compared well with those obtained with a commercial automatic vector network analyzer (ANA). Similarly, dielectric properties measurements on polypropylene, acrylic, and acetal spheres also agreed well with those obtained by the ANA.

A dataset of clinically recorded radar vital signs with synchronised reference sensor signals

Using Radar it is possible to measure vital signs through clothing or a mattress from the distance. This allows for a very comfortable way of continuous monitoring in hospitals or home environments. The dataset presented in this article consists of 24 h of synchronised data from a radar and a reference device. The implemented continuous wave radar system is based on the Six-Port technology and operates at 24 GHz in the ISM band. The reference device simultaneously measures electrocardiogram, impedance cardiogram and non-invasive continuous blood pressure. 30 healthy subjects were measured by physicians according to a predefined protocol. The radar was focused on the chest while the subjects were lying on a tilt table wired to the reference monitoring device. In this manner five scenarios were conducted, the majority of them aimed to trigger hemodynamics and the autonomic nervous system of the subjects. Using the database, algorithms for respiratory or cardiovascular analysis can be developed and a better understanding of the characteristics of the radar-recorded vital signs can be gained.

A GaAs Power Detector Design for $C$ -Band Wideband Complex Cross Correlation Measurement

The design and measurement of a power detector circuit based on the 0.15- $\mu \text{m}$ GaAs pHEMT technology and its usage in complex cross correlation measurement are presented in this article. The six-port technology is employed for the calculation of the cross correlation, and the design equations from the requirements of the correlation measurement are provided to guide the power detector design. The relation between the signal-to-noise ratio (SNR) of the correlation results and the load resistor is deduced, which can restrict the resistor value choice for an acceptable SNR. By properly choosing the load resistor and the biasing of the transistor, a power detector circuit is designed with a suppressed output dc voltage variation resulting from the statistic feature of monolithic microwave integrated circuit (MMIC) production. A fabricated detector chip has been mounted onto a printed circuit board and has been characterized. The measurement results show a flat responsivity over 3.5–8 GHz and a 3-nV/ $\sqrt {\mathrm{ Hz}}$ output noise voltage spectrum. The complex cross correlation measurement is implemented using two power detector modules with carefully chosen bias currents. Across the frequency range of 3.5–8 GHz, the measured correlation circles have an amplitude imbalance of 3.5 dB and an axial ratio from 0.85 to 1.15. With an input power of −5 dBm, the measured SNR of the correlator output is above 26 dB.

A 77-GHz Six-Port Sensor for Accurate Near-Field Displacement and Doppler Measurements.

A continuous-wave (CW) radar sensor design based on a millimetre-wave six-port interferometer is proposed. A complete sensor prototype is conceived of, fabricated and measured at 77 GHz for short-range professional and industrial applications. This sensor is designed to measure distances and Doppler frequencies with high accuracy, at a reasonable cost. Accurate phase measurements are also performed using the six-port technology, which makes it a promising candidate for CW radar sensing applications. Advances in the performance and functionality of six-port sensors are surveyed to highlight recent progress in this area. These include improvements in design, low power consumption, high signal to noise ratio, compactness, robustness and simplicity in realization. Given the fact that they are easy to fabricate, due to the lack of active circuits and being highly accurate, it is expected that six-port sensors will significantly contribute to the development of human tracking devices and industrial sensors in the near future. The entire circuit prototype, including the transmitter, the receiver antenna, the six-port interferometer and the four power detectors have been integrated on a die. The circuit is fabricated using a hybrid integrated technology on a 127-m ceramic substrate with a relative permittivity of . Calibrated tuning forks are used to assess the performance of the six-port sensor experimentally for various frequencies.

NEW IMPLEMENTATION OF MM-WAVE HETERODYNE RECEIVER BASED ON SIX-PORT TECHNOLOGY: CIRCUIT CHARACTERIZATION AND HIGH DATA-RATE DEMODULATION RESULTS

This paper presents a new implementation of a millimeter wave heterodyne receiver based on six-port technology. The six-port circuit is designed using three hybrid couplers H-90 ◦ and a new ring power divider. For the characterization of the circuit, several six-port two-port measurement configurations were designed and fabricated on the same wafer along with calibration standards. The new six-port architecture evaluation based on qi points location demonstrates wideband performances and high coupled-port phase and amplitude balance in the 57-65 GHz frequency band. The six-port model based on S-parameter measurements is then implemented in ADS software, for realistic advanced simulation systems of a short-range 60 GHz wireless link. The millimeter wave frequency conversion is performed using a six-port down-converter. The second frequency conversion uses conventional means due to the low IF frequency value. The demodulation results of a V-band QPSK signal for high data rate from 100 to 1000 MBits/s are presented and discussed. The results of the Bit Error Rate (BER) analysis demonstrate that the proposed architecture can be successfully used for high speed wireless link transmission at 60 GHz.

Six-Port Technology for Traffic Safety

The market for driver-assistance systems for modern automobiles is rapidly growing. Formerly only provided for the luxury automotive market, these systems are nowadays more and more available for mid- and compact-class vehicles as well. This development is not only limited to the passenger car segment but is also more and more important for commercial vehicles and trucks. Some driving assistance systems have already become mandatory, e.g., the antilock breaking system (ABS). Some governments are currently thinking about requiring automatic distance control by law for heavy trucks. Automatic distance control in combination with an automatic emergency breaking system is one of the rising stars for enhancing traffic safety. Radar- based distance control mostly interacts with cruise control systems and it adapts the speed of the driver's car to the distance to the car or obstacle in front of the vehicle. Furthermore, unavoidable accidents are detected and actions for reducing the effects of the crash are automatically initiated for some systems.

Analysis and implementation of six-port software-defined radio receiver platform

With recent advances in semiconductor processing technology and the development of reconfigurable devices, high bit-rate software-defined radio (SDR) has become practical for commercial applications. This paper proposes an SDR receiver platform based on a new substrate integrated waveguide six-port structure. This SDR receiver platform operates from 22 to 26 GHz and it is designed to be robust, low cost, and suitable for different communication schemes. In this study, the receiver is demonstrated to support quadrature phase-shift keying and 16 quadrature amplitude modulation schemes. System-level simulation is made and prototype circuits are fabricated to evaluate the system performance. It is found that the combination of SDR and six-port technology can provide a great flexibility in system configuration, a significant reduction in system development cost, and also a high potential for software reuse. The proposed receiver shows a possible application of universal direct demodulator for future SDR terminals in various wireless communication systems.

Direction-of-arrival estimation method based on six-port technology

A new direction-of-arrival estimation method based on six-port technology is presented. In order to obtain the beam direction, the proposed circuit uses a two-channel multi-band receiver and analogue signal processing of the six-port circuit output signals. A practical approach for estimating the beam direction has also been proposed. This approach, based on the detection of the minimum magnitude of the in-quadrature output signal, avoids the necessity of computing the angle-of-arrival value. A dual-band prototype circuit was designed and fabricated. Simulation results in the S and C frequency bands are presented and discussed. In order to validate this method, measurements were carried out in the C-band. These results show a maximal angle-of-arrival estimation error of about 3%. Therefore, low-cost direction-of-arrival measurements can be performed using this new method.

Direct quadrature phase shift keying modulator using six-port technology

A direct quadrature phase shift keying modulator based on six-port technology is presented. The modulator comprises a six-port circuit, a switch matrix and open and short terminations. Using this modulator, direct phase shift keying modulation was achieved. Six-port technology has the advantage of signal integrity, low power consumption and physical scalability to attain different frequencies of operation and extendibility to M-ary phase shift keying. Experiment results demonstrate performance with an output phase difference from 0.8 to 4.5° and an amplitude difference from 0.5 to 2.7 dB. A data throughput of 200 Mbits was attained.

Ka-band analog front-end for software-defined direct conversion receiver

A six-port Ka-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/Q 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.

The six-port as a communications receiver

Configurable radio terminals require receivers with wide-band capabilities in order to support as many services as possible at most different carrier frequencies. Conventional well-known receiver architectures employing active circuitry are limited in this respect. Therefore, alternative architectures are investigated, such as the six-port, which has been introduced as a very flexible and elegant means for microwave measurements in the 1960s and 1970s. Later on, it has been used in radar applications. It was not until recently that communications receivers have been built upon the six-port principle. However, in all publications, there is always a certain mystic about the six-port. It has even been described as a black box. In order to help paving the way for a wider application of the six-port technology, this paper describes the basic six-port theory and sets it into relation with the conventional receiver architectures such as the homodyne and heterodyne receiver. Finally, the advantages and possible applications of receivers based on the six-port technology are discussed.

Low cost architecture of direct conversion digital receiver

The paper presents a low-cost architecture for a direct conversion digital receiver that uses six-port technology. An experimental prototype has been constructed and tested. Analogue carrier recovery and decision circuits are investigated as a means to provide future system integration and high data rate capacity. The designed receiver is operated at an ISM frequency of 2.45 GHz and uses a QPSK modulation format. Results on data rate limitations are given for QPSK signals up to 52 Mb/s. Test results related to adjacent channel, co-channel and CW interferences are presented for a data rate of 40 Mb/s. Phase offset between carrier and reference signals, along with carrier frequency deviation performances, are also presented for a rate of 40 Mb/s. A frequency hopping spread spectrum technique is discussed on the basis of the proposed architecture.

A Software Defined Radio Platform with Direct Conversion: SOPRANO

In this paper, a new software defined radio platform with direct conversion is introduced. The platform is named SOPRANO, which stands for Software Programmable and Hardware Reconfigurable Architecture for Network. Main features of SOPRANO include a high-level design methodology for digital circuits, direct conversion based on six-port technology, and novel digital signal processing algorithms for multi-band and multi-mode operation. The first prototype of the SOPRANO platform has been built and was able to receive M-ary PSK (Phase Shift Keying) and QAM (Quadrature Amplitude Modulation) signals, with two different carrier frequencies at 2.45 GHz and 5.25 GHz, by changing signal-processing software.

On the Application of Six-Port Technology (SPT) in Ultrasonic Imaging for Medical Diagnosis

In this paper, an introduction of six-port technology to ultrasonic imaging for medical diagnosis is presented for the first time. Calculations are made to explore the possibilities and advantages of this application. Analysis shows that the introduction of six-port technology for medical ultrasonic imaging to detect the phase information of the reflected signal will improve the measurement accuracy and simplify the instrumentation of imaging technologies used in medical diagnosis.

Six-port based wave-correlator with application to beam direction finding

Six-port technology is well known for its ability to accurately measure the scattering parameters of a microwave network. In this paper a six-port based wave-correlator, which is operated as a two-channel wave receiver, is reported. A novel method for calibrating the six-port based wave-correlator by using only one phase shifter is proposed. The calibration procedure offers simple formulas for determining the calibration parameters, and their validity and accuracy are confirmed by measurements. In addition, an application of the proposed wave-correlator to beam direction finding is discussed. Experimental proof at X-band frequency was carried out and satisfactory results were obtained.

Six-Port Receiver and Frequency Measurement for Radar Applications at 35GHz

The application of a six-port technology in the receiving part of a radar front-end is described in this paper. This receiver allows measuring magnitude and phase of the radar signal without the need of down-conversion. According to the applications and the availability of the devices needed for assembling the prototype sensor, the frequency of operation was set to 35GHz. The structure of this six-port as well as the calibration and measurement algorithms are described in detail. The accuracy of the phase measurement is 2–10° depending on the power level of the signal. Another key element of the proposed radar sensor is a direct frequency counter. Using this circuit it is possible to measure the frequency of operation with a resolution of 20 bits within 120μs. The accuracy of the distance reading of the radar is directly related to the accuracy of the frequency measurement and has reached 0.1mm.

A microwave position sensor with submillimeter accuracy

Design and characteristics of a prototype distance sensor are presented in this paper. The radar front-end operates at 35 GHz and applies six-port technology and direct frequency measurement. The sensor makes use of both frequency-modulated continuous wave and interferometer principles and is capable of measuring distance with a very high accuracy of /spl plusmn/0.1 mm.