Study Of Direct Conversion Receiver Based On The Sex-port Technology

With the rapid development of the wireless communication technology, wirelesscommunications products have become a significant part of the developing informationworld. RF receiver, located in the forefront of the wireless communication system,directly determines the structure and performance of the system. Therefore, theresearchers are committed to optimizing the design of the structure and choosing theappropriate manufacturing process in order to improve the performance-to-price ratio.Practical receiver system has two basic architectures: superheterodyne andzero-intermediate frequency (direct conversion). Superheterodyne receiver is the mostclassic receiver structure, which played a significant role in the wireless system for avery long time. In recent years, the direct conversion receiver has gradually become ahotspot for its simple structure, no mirror-frequency interference, low-frequencychannel selection based on the low-pass filter, ease of integration and other advantages.Direct conversion receivers can be used in the phase measurement, frequencymeasurement, direction finding, position sensor or the demodulation of digital signal.As the core technology of the direct conversion receiver, the researchers try their best tomake progress in six-port technology and have gained some achievements these years.In this thesis, the direct conversion receiver based on the six-port technology isdiscussed. The theoretical derivation, design of circuit module, composition of the blockdiagram, structure of test platforms and some related tasks are proposed as well. Themain contents of this thesis are summarized as follows: the design and implementationof the wideband (narroband) six-port junction, some measurement techniques based onthe six-port technique (phase measurement, frequency measurement, direction finding,position sensor), the design and implementation of the high-gain amplifier, thecalibration technique based on the ANN (Artificial Neural Networks) and SVR (SupportVector Regress), the miniaturization of components and system via LTCC (LowTemperature Co-fired Ceramic), etc. This thesis is divided as the following aspects:1. The theory of six-port technology, the principles of six-port reflectometer anddirect conversion receiver based on six-port technology are introduced systemly. Based on the principles and the design methods of the six-port junction, a narrowband six-portjunction is designed and manufactured. To expand the bandwidth, we designed twokinds of ultra-wideband power dividers and3dB couplers to elucidate two types ofultra-wideband six-port junctions.2. Based on the six-port technology, the systems of phase measurement, frequencymeasurement, direction finding and position sensor are intensively studied. Someengineering problems occurring in these systems such as self-oscillation, crosstalk, andphase drift have been solved. One of the difficulties is the design of hign-gain amplifier.The crosstalk of power supply, electromagnetic radiation, interaction of internalcascaded amplifiers and other factors can lead to the self-oscillation. These uncertainfactors need to be taken into considerations, and the corresponding solutions areproposed in the circuit design. The electromagnetic compatibility is utilized in theintegration of receiver system, based on the high-gain RF amplifier.3. The calibration techniques based on ANN and SVR is introduced. Owing to theinherent flaws of the six-port receiver, such as the non-idealitied of amplitude and phasecharacteristics in six-port junction, the nonlinearity of diode detector, theinconsistencies of microwave channel and other factors, the system need to becalibrated by a simple and practical methods. First of all, a set of test data is obtained bythe instrumentation. Then all of the test data is divided into two parts: training andcross-validation data set. The training data set is used to obtain a “kernel function” toreflect the relationship between the input and output, while cross-validation data set isused to verify the predicted effect of “kernel function”.4. The wideband3dB coupler and power divider based on the LTCC technologyare designed to reduce the circuit area of the six-port junction. Microstrip line andair-filled waveguide are two basic energy transmission pathways. However, theenormous difference in the characteristic impedance between them makes impedancematching difficult. To expand the bandwidth Multi-resonant patches andmulti-impedance transformation sections are added into the LTCC dielectric materialand the transmission line, respectively. Furthermore, the LTCC miniaturization of thetransceiver system has been studied in this thesis.