一种新型FMCW雷达射频对消方法

随着平台一体化及雷达系统微型化的发展,调频连续波(FMCW)雷达发射至接收的信号泄漏更为严重,信号泄漏已成为制约FMCW雷达系统性能的关键因素。为解决这一问题,提出了一种新型的射频对消方法以提高FMCW雷达的收发隔离度,利用FMCW雷达泄漏信号与回波信号在频域可分离特点,采用数字锁相环技术产生主动对消矢量信号,在给定FMCW雷达泄漏信号初值的条件下仿真分析对消比与相位误差、幅度误差的关系,建立了特定条件下的具有自适应功能的射频对消方案,并设计了验证电路以验证方案的可行性。验证结果表明该方法在1 GHz带宽内实现了优于25 dB 的对消比,且该对消电路具有低功耗、结构简单等优势。     

一种平衡式环行器收发隔离电路的设计与实现

对于收发天线一体、收发频率相近、收发信号同时存在的无线电通信应用场景,比如UHF RFID的读卡器,目前一般使用单独的环行器来进行收发隔离,但其隔离度有限,一般在20 dB左右。从理论上分析了由两个环行器组成的平衡式环行器隔离电路的隔离原理,并提出了一种改进平衡式环行器收发隔离电路,同时制作了电路模块。网络分析仪测试表明,该改进平衡式环行器收发隔离电路的发射端到天线端的传输损耗和天线端到接收端的传输损耗都在1 dB以内,在连接驻波比为1.2∶1的板式天线情况下,其收发隔离度达到了50 dB以上;实测当射频输入功率处于0.1 W～8.0 W区间时,该电路的收发隔离度稳定在40 dB以上,较使用单独环行器时的隔离度至少提高了20 dB。     

一种具有高隔离度的双频双圆极化卫星通信天线

 提出了一种新型的用于卫星通信的双频双圆极化多层微带贴片天线.该天线采用兰格耦合器正交馈电,分别在420±1.5MHz和450MHz±1.5MH的收发频率实现右旋和左旋圆极化辐射,且满足单一天线收发双工的通信要求;采用耦合贴片馈电方式和附加集总电路滤波网络,有效地改善了两端口之间的收发隔离度.此外,该天线采用高介电常数的介质基板减小了天线尺寸.兰格耦合器采用曲折线技术减小了馈电网络的结构尺寸(约74.6%).仿真和实测结果吻合良好,在工作频带内收发隔离度大于40dB,VSWR小于2.0,增益大于3dBc,0dB增益宽度及3dB轴比宽度均达到80°.     

一种新颖的宽频共缆微带分路器设计

随着有源相控阵天线技术的发展,天线设备同系统中的收发终端需要通过采用各类射频、数字和电源类型的线缆进行互联,采用宽频共缆传输技术可以有效降低工程成本和系统重量。设计了一种宽频共缆微带分路器,通过采用传输线的多级阻抗变换原理,在不用额外的滤波电路情况下,在射频工作频段内,总输入端口的电压驻波比小于1.8,通往射频分端口2的S₂₁大于-0.6 dB,通往控制分端口3和电流分端口4的S₃₁小于-45 dB和S₄₁小于-105 dB,实现了良好的隔离度和传输效果。该分路器具有设计简单、隔离度高、信号能量损耗小和易于调试的优点。     

一种高收发隔离的RFID读写器天线设计仿真

提出了一种新型用于UHF频段RFID读写器的圆极化高隔离度收发天线,该天线采用3dB分支线定向耦合器馈电,在915±5MHz频段内实现发射左旋圆极化波接收右旋圆极化波,不但满足了单天线收/发双工通信,还实现了发射和接收两端口高隔离度,仿真结果表明在中心频率915MHz处隔离度高达51dB,有效抑制了载波泄漏到接收端口中...     

单天线FMCW雷达发射泄漏信号抑制技术研究

针对单天线调频连续波雷达发射信号泄漏问题,考虑到自适应控制系统的数据处理能力强、准确灵活等优点,提出了自适应对消技术方案,并进行了仿真分析和实验验证,结果表明,该方案有效抑制了由于收发隔离不足导致的发射泄漏信号问题。     

FMCW雷达发射泄漏信号数字对消技术研究

针对单天线调频连续波雷达发射信号泄漏问题,结合数字自适应系统数据处理能力强、准确灵活、通用能力强等优点,提出了数字对消技术方案,并进行了仿真分析和实验验证,结果表明,该方案能有效抑制由于收发隔离不足导致的发射信号泄漏问题。     

一种应用收发一体功分器设计收发馈电网络的方法

为了实现高密度的天线集成,通常会将多个天线单元紧密排列,因此需要设计连接各个单元的收发馈电网络。应用收发一体功分器级联成收发馈电网络,收发一体功分器在设计时就采用多层结构,并考虑网络层叠的影响,可以确保发射和接收互不干扰。此外,采用通孔结构,并将电阻置于底部可以降低加工难度和成本。应用该方法设计了一种收发一体双8路的馈电网络,在工作频带内,测试的反射系数小于-22 dB,隔离度高于61 dB,各个通道间的幅度一致性小于0.2 dB,相位一致性小于2.3°。该方法可缩短设计周期,提高研发效率,而且设计的馈电网络具有高隔离和低成本等优点,可用于平板阵列天线中。     

同时同频全双工天线阵列自干扰抑制设计

针对同时同频全双工天线阵列系统中的自干扰问题,开展收发一体天线优化设计,对收发天线间表面波电流的传播途径进行了分析。根据分析结果,在发射天线与接收天线之间设计谐振陷波结构,可有效降低天线之间的自干扰信号电平。通过仿真手段验证了陷波结构对抑制收发天线间自干扰的可行性,达到了42 dB的无源天线隔离度,从而为同时同频全双工天线阵列的设计提供一种可行的应用方案。     

一种基于FPGA的自适应射频对消方法

针对单天线调频连续波(FMCW)雷达的发射信号泄漏进接收通道,恶化接收机灵敏度,使接收机前端饱和的问题。本文基于最小均方(LMS)自适应算法,利用FPGA实时对消泄漏进接收通道的发射信号,有效提高单天线FMCW雷达收发间的隔离度。在X波段单天线FMCW雷达平台上,测试结果表明,泄漏进接收通道的发射信号可以达到40dB的对消深度,表明该方法的有效性。     

A Quadrature Radar Topology With Tx Leakage Canceller for 24-GHz Radar Applications

A quadrature radar topology with a Tx leakage canceller is presented. The canceller is composed of four branch-line hybrid couplers, a 90deg delay line, and a Wilkinson combiner. It has high Tx-to-Rx isolation and wide bandwidth characteristics. The isolation is 35.27 dB at 24 GHz and does not drop below 30 dB over a 2-GHz bandwidth. Given that the isolation of the branch-line hybrid coupler is 21.5 dB, the enhancement of the isolation is expected to be 13.77 dB. A quadrature Doppler radar front-end with the canceller was implemented. The noise level in the mixer output is lower by 9 dB compared with that of a conventional quadrature radar. This radar can measure speed as low as 0.76 mm/s, which correspond to a 0.12-Hz Doppler shift. It is also able to detect signs of the Doppler shift from a moving target due to its quadrature topology.     

Quasi-circulator for effective cancellation of transmitter leakage signals in monostatic six-port radar

A quasi-circulator, composed of two branch-line couplers and an asymmetric power combiner, is proposed to effectively cancel the transmitter leakage signals in a monostatic six-port radar. The effective isolation is improved by 12.2 dB at 24 GHz. With the proposed quasi-circulator, the maximum detectable range of the six-port radar is improved by 167 , compared with that of the six-port radar with a conventional branch-line coupler.     

A compact 24 GHz quadrature Doppler radar with front-end MMIC

A compact 24?GHz quadrature Doppler radar front-end monolithic microwave integrated circuit (MMIC) with Tx leakage canceller is developed. The chip is 3?×?2?mm² and the front-end module is 3?×?3?cm². The MMIC consists of a 24?GHz voltage-controlled oscillator, a Tx leakage canceller and two mixers. The radar module can measure speeds as low as 2.5?mm/s, which corresponds to a 0.41?Hz Doppler shift. The quadrature topology enables the signs of a Doppler shift to be detected and obviates the null point problems.     

Balanced topology to cancel Tx leakage in CW radar

Balanced topology in radar front-end is presented, which can reduce Tx leakage to receiver drastically. The balanced radar front-end which is composed of a differential cross-coupled oscillator, two Lange couplers, and a Wilkinson combiner is implemented using commercially available InGaP/GaAs heterojunction bipolar transistor technology. The tuning range of voltage control oscillator is 320 MHz from 25.307 to 25.627 GHz. The peak output power is 0.8 dBm. Average Tx-to-Rx isolation is about 40.5 dB. Since the isolation of the Lange coupler is 19 dB, the additional cancellation due to balanced topology is expected to be 21.5 dB. The chip size is 1.05 /spl times/ 1.70 mm/sup 2/.     

A Circularly Polarized Balanced Radar Front-End With a Single Antenna for 24-GHz Radar Applications

In this paper, we propose a circularly polarized balanced radar front-end topology with a Tx leakage canceller. This radar is composed of a dual-orthogonal fed microstrip patch antenna, a 90$^circ$ delay line, a differential cross-coupled oscillator, two Lange couplers, a Wilkinson combiner, and a mixer. We implemented circularly polarized balanced Doppler radars by using a printed circuit board and InGaP/GaAs heterojunction bipolar transistor technologies. The front-end chip and module with antenna are 1 mm $times$ 1 mm and 3 cm $times$ 3 cm, respectively. The average Tx-to-Rx isolation is about 36 dB. This radar can measure speeds as low as 0.5 mm/s, which corresponds to a 0.076-Hz Doppler shift. The received signals of the circularly polarized balanced Doppler radar are about two times larger than those of a linearly polarized balanced Doppler radar due to the topology. This result occurs because the proposed radar has an intrinsic loss of only 3 dB in the receiving path.      

Multilayer Substrate Integrated Waveguide Six-Port Circuit

In this paper a new design of a six-port circuit based on multilayer substrate integrated waveguides (SIW) is presented. This design is based on the use of a multilayer structure aimed at reducing the dimension of the circuit while conserving the performances of the component. The designed SIW six-port is composed of two basic elements, a SIW power divider and directional coupler. These two elements are designed, optimized and matched to produce a better performance at the required operating frequency of 11 GHz. The results of simulations show that the new multilayer SIW six-port circuit has good performances including a good return loss and isolation under–20 dB and the transmission magnitude better than–10 dB. This multilayer SIW six-port has the advantage of a small size 160-34.8 mm; its width is about 50% smaller than the planar SIW six-port circuit, which helps to get a higher density of integration in telecommunication systems and allows much smaller devices to be conceived.A microstrip toSIWtransition is used in order to facilitate the integration of this component into other planar circuits. The structures are designed, simulated and optimized using the Ansoft HFSS simulation software.     

新型四次谐波混频电路

本文介绍了一种适用于高次谐波混频的电路原理图,基于空闲频率相位抵消理论,该混频电路结构可以避免复杂的空闲频率回收电路设计,同时能获得很高的端口隔离度。基于该结构,设计了新型的Ka波段四次谐波混频器,该混频器在38.4 GHz测得最小变频损耗 8.3 dB,在34-39 GHz 变频损耗小于10.3dB, LO-IF、RF-LO、 RF-IF 端口隔离度分别优于30.7 dB、 22.9dB、46.5dB。     

基于微带双脊间隙波导技术的Ka波段六端口网络电路

面向毫米波高精度雷达探测应用,文中提出了一种基于微带双脊间隙波导技术的六端口网络电路。设计了基 于微带双脊间隙波导的功分器和耦合器电路,提出了微带双脊间隙波导至微带线的新型过渡转换结构,并基于简化的六 端口网络原理框图,将所设计的功分器、耦合器以及过渡转换结构进行有机组合,实现了所设计的Ka 波段六端口网络电 路。实验测试结果表明:在所设计的37.5 GHz~ 42.5 GHz 频率范围内,输入端口1 与四个输出端口间的相位差均 在±2.5°以内,输入端口2与四个输出端口间的相位差均在±5°内,工作中心频率处的输入输出间插入损耗约为7.3 dB。 实验与仿真结果吻合较好。     

A 77 GHz SiGe sub-harmonic balanced mixer

A novel SiGe 77 GHz sub-harmonic balanced mixer is presented with a goal to push the technology to its limit [SiGe2-RF transistor (f/sub T/=80 GHz)]. This new topology uses a compact input network not only to achieve high isolation between the LO and RF ports, but also to result in excellent 2LO-RF isolation. The measured results demonstrate a conversion gain of 0.7 dB at 77 GHz with an LO power of 10 dBm at 38 GHz, LO-RF isolation better than 30 dB, 2LO-RF isolation of 25 dB, and a P/sub 1dB/ of -8 dBm. The mixer core consumes 4.4 mA at 5 V. The circuit demonstrates that SiGe sub-harmonic mixers have comparable performance with GaAs designs, at a fraction of the cost.     

Design and analysis for a miniature CMOS SPDT switch using body-floating technique to improve power performance

A low insertion-loss single-pole double-throw switch in a standard 0.18-/spl mu/m complementary metal-oxide semiconductor (CMOS) process was developed for 2.4- and 5.8-GHz wireless local area network applications. In order to increase the P/sub 1dB/, the body-floating circuit topology is implemented. A nonlinear CMOS model to predict the switch power performance is also developed. The series-shunt switch achieves a measured P/sub 1dB/ of 21.3 dBm, an insertion loss of 0.7 dB, and an isolation of 35 dB at 2.4 GHz, while at 5.8 GHz, the switch attains a measured P/sub 1dB/ of 20 dBm, an insertion loss of 1.1 dB, and an isolation of 27 dB. The effective chip size is only 0.03 mm/sup 2/. The measured data agree with the simulation results well, including the power-handling capability. To our knowledge, this study presents low insertion loss, high isolation, and good power performance with the smallest chip size among the previously reported 2.4- and 5.8-GHz CMOS switches.