SIFT算法详解及应用(讲的很详细)
SIFT算法入门时看的一篇文章，SIFT算法详解及应用(讲的很详细)SIFT简介SIFTScale Invariant Feature Transform传统的特征提取方法成像匹配的核心问题是将同一目标在不同时间、不同分辨率、不同光照、不同位姿情况下所成的像相对应。传统的匹配算法往往是直接提取角点或边缘,对环境的适应能力较差,急需提出一种鲁棒性强、能够适应不同光照、不同位姿等情况下能够有效识别目标的方法。己0]/3/己7彐SIFT简介SIFTScale Invariant Feature TransformSIFT提出的目的和意义分1999年 British columbia大学大卫.劳伊( David g.Lowe)教授总结了现有的基于不变量技术的特征检测方法,并正式提出了一种基于尺度空间的、对图像缩放、旋转甚至仿射变换保持不变性的图像局部特征描述算子一SIFT(尺度不变特征变换),这种算法在2004年被加以完善己0]/3/己7SIFT简介SIFTScale Invariant Feature Transform将一幅图像映射(变换)为一个局部特征向量集;特征向量具有平移、缩放、旋转不变性,同时对光照变化、仿射及投影变换也有一定不变性。己0]/3/己7SIFT简介SIFTScale Invariant Feature TransformSIFT算法特点SIFT特征是图像的局部特征,其对旋转、尺度缩放、亮度变化保持不变性,对视角变化、仿射变换、噪声也保持一定程度的稳定性。独特性( Distinctiveness)好,信息量丰富,适用于在海量特征数据库中进行快速、准确的匹配。多量性,即使少数的几个物体也可以产生大量SIFT特征向量。经过优化的SIFT算法可满足一定的速度需求。可扩展性,可以很方便的与其他形式的特征向量进行联合。己0]/3/己7SIFT简介SIFTScale Invariant Feature TransformSIFT算法可以解决的问题目标的自身状态、场景所处的环境和成像器材的成像特性等因素影响图像配准/目标识别跟踪的性能。而SIFT算法在一定程度上可解决:目标的旋转、缩放、平移(RST)图像仿射/投影变换(视点 viewpoint)光照影响(111 amination)目标遮挡( occlusion)杂物场景(c1 utter)噪声己0]/3/己7SIFT算法实现细节SIFTScale Invariant Feature TransformSIFT算法实现步骤简述SIFT算法的实质可以归为在不同尺度空间上查找特征点(关键点)的问题。原图像特征点特征点目标的特检测描述征点集特征点匹匹配点矫配正目标图像特征点特征点目标的特检测描述征点集SIFT算法实现物体识别主要有三大工序,1、提取关键点;2、对关键点附加详细的信息(局部特征)也就是所谓的描述器;3、通过两方特征点(附带上特征向量的关键点)的两两比较找出相互匹配的若干对特征点,也就建立了景物间的对应关系。SIFT算法实现细节SIFTScale Invariant Feature TransformSIFT算法实现步骤关键点检测己。关键点描述彐·关键点匹配4·消除错配点己0]/3/己7关键点检测的相关概念SFTiant Feature Transfor1.哪些点是SIFT中要查找的关键点(特征点)?这些点是一些十分突出的点不会因光照条件的改变而消失,比如角点边缘点、暗区域的亮点以及亮区域的暗点,既然两幅图像中有相同的景物,那么使用某种方法分别提取各自的稳定点,这些点之间会有相互对应的匹配点。所谓关键点,就是在不同尺度空间的图像下检测出的具有方向信息的局部极值点。根据归纳,我们可以看出特征点具有的三个特征:尺度方向大小己0]/3/己7
- 2020-05-27下载
- 积分：1
使用CC2591作为CC2530的功放
使用CC2591作为CC2530的功放, CC2591 PAThe absolute maximum ratings and operating conditions listed in the CC2530 datasheet [1]and the CC2591 datasheet [4] must be followed at all times. Stress exceeding one or more ofthese limiting values may cause permanent damage to any of the devicesNote that these characteristics are only valid when using the recommended register settingspresented in Section 4.6 and in Chapter 8, and the CC2530 - EM reference designOperating Frequency240524835MHzOperating Supply Voltage2036VOperating Temperature-40CTC=25C, VDD=3.0V, f=2440 MHz if nothing else is stated. All parameters are measuredon the CC2530-Cc2591EM reference design [11] with a 50 Q2 loadReceive CurrentWait for sync, -90 dBm input levelWait for sync, -50 dBm input level24mATXPOWER OXE5166mATXPOWER OXD5149mATXPOWER OXC5138mATXPOWER OXB5127mATransmit currentTXPOWER OXA5115ATXPOWER = 0X95100mATXPOWER = 0X8594ATXPOWE=0×75mATXPOWE=0×6579APower Down Current PM2UAISTRUMENTSPage 3 of 19SWRA308ATC=25C, Vdd=3.0V, f= 2440 MHz if nothing else is stated. All parameters are measuredon the CC2530-CC2591 EM reference design with a 50 Q2 loadReceive Sensitivity HGM 1 %PER, IEEE 802. 15.4[6] requires -85 dBm-988dBmReceive Sensitivity LGM1 PER, IEEE 802. 15.4 [6] requires -85 dBm-90.4dBmSaturationlEEE 802.15. 4 [6] requires-20 dBm10dBmWanted signal 3 db above the sensitivity levelIEEE 802.15.4 modulated interferer at ieee 802.15.4 channelsInterferer Rejection+5 MHz from wanted signal, IEEE 802. 15. 4 [6] requires 0 dBdB+10 MHz from wanted signal, IEEE 802. 15. 4 [6] requires 30 dB49dB+20 MHz from wanted signal wanted signal at- 82d BmdBdue to in the external lna and the offset in cc2530 the rssi readouts from cc2530CC2591 is different from rssi offset values for a standalone cc2530 design the offsetvalues are shown in table 4.4High Gain Mode79LoW Gain mode67Real rssi Register value-Rssl offsetISTRUMENTSPage 4 of 19SWRA308ATc=25C, Vdd=3.0V, f=2440 MHz if nothing else is stated All parameters are measuredon the CC2530-CC2591 EM reference design with a 50 Q2 load Radiated measurements aredone with the kit antennaRadiated Emissionwith TXPOWer Oxe5Conducted 2. RF (FCC restricted band)-462|dBmConducted 3. RF(FCC restricted band46.5 dBmComplies withFCC 15.247. SeeChapter 7 for moredetails about regulatoryRadiated 2.RF(FCC restricted band)42.2dBmrequirements andcomplianceIEEE 802.15.4[6]requires max.35%%Measured as defined by IEEE 802.15. 4 6TXPOWER OxE5. f= EEE 802.15. 4 channels13TXPOWER= OXD5. f= EEE 802.15.4 channelsTXPOWER= OXC5 f= EEE 802.15.4 channelsMax error∨ ectorTXPOWER OxB5 f= IEEE 802.15. 4 channelsMagnitude(EVM)TXPOWER OxA5. f= IEEE 802.15.4 channelsTXPOWER 0X95. f= IEEE 802. 15.4 channels643333%%%%%%%TXPOWER= 0x85. f= iEEE 802. 15.4 channelsTXPOWER =0x75 f= IEEE 802. 15.4 channels%TXPOWER= 065. f= iEEE 802. 15.4 channelsThe RF output power of the CC2530- CC2591 EM is controlled by the 7-bit value in theCC2530 TXPOWER register. Table 4.6 shows the typical output power and currentconsumption for the recommended power settings The results are given for Tc= 25 C, Vdd3.0V and f= 2440 MHz, and are measured on the cC2530-CC2591 EM reference designwith a 50 Q2 load. For recommendations for the remaining CC2530 registers, see Chapter 8 oruse the settings given by SmartRF StudioOXE520166OxD519149OxC18138OxB517127OxA5161150x95141000x8513940X75860x651079Note that the recommended power settings given in Table 4.6 are a subset of all the possibleTXPOWER register settings. However, using other settings than those recommended mightINSTRUMENTSPage 5 of 19SWRA308Aresult in suboptimal performance in areas like current consumption, EVM, and spuriousemissionTc=25C, Vdd=3.0V, f=2440 MHz if nothing else is stated All parameters are measuredon the CC2530-CC2591EM reference design with a 50 32 load2221-2V201918171611121314151617181920212223242526251510OxE5OxC5OxA50X850x65540-30-20-1001020304050607080ISTRUMENTSPage 6 of 19SWRA308A98Avg 3.6VAva 3vAvg 2V110111213141516171819202122232425261023.6V-1062V-110-40-30-20-100102030405060708070604020-Wanted signal at:-82 dBm10ISTRUMENTSPage 7 of 19SWRA308ACC2530-CC2591EM High Gain ModeC C2530-CC2591EM Low Gain Mode- CC2530EM40000-100110100908070-60-50-40-30-20-100The IEEE standard 802.15. 4 [8] requires the transmitted spectral power to be less than thelimits specified in table 4.7If-fc>3.5 MHz-20 dB-30 dBmThe results below are given for Tc=25 C, Vdd=3.0V and f= 2440 MHz, and are measuredon the CC2530-CC259 1EM reference design with a 50 Q loadIEEE absoluteChannel 182432.52435243752442524452447.5ISTRUMENTSPage 8 of 19SWRA308AOnly a few external components are required for the CC2530-CC2591 reference design. Atypical application circuit is shown below in Figure 5.1. Note that the application circuit figuredoes not show how the board layout should be done. The board layout will greatly influencethe RF performance of the CC2530-CC2591EM. TI provides a compact CC2530CC2591 EM reference design that it is highly recommended to follow. The layout, stack-upand schematic for the CC2591 need to be copied exactly to obtain good performance. Notethat the reference design also includes bill of materials with manufacturers and part numbersL102 L10=TI INF inductorVDD13cc2530LA 1RF PANTCC2591 RF NFNPA EN(P1 1)i工工I NA FNP:1HGM ENPO 7)T:1Proper power supply decoupling must be used for optimum performance. In Figure 5.1, onlythe decoupling components for the CC2591 are shown. This is because, in addition todecoupling, the parallel capacitors C11, C101, and C131 together with, L101, L102, TL11TL101 and TL131 also work as RF loads. These therefore ensure the optimal performancefrom the CC2591. C161 decouples the AvDD blAs power.The placement and size of the decoupling components, the power supply filtering and thePCB transmission lines are very important to achieve the best performance Details about theimportance of copying the CC2530-CC2591EM reference design exactly and potentialconsequences of changes are explained in chapter 6The RF input/output of CC2530 is high impedance and differential. The CC2591 includes abalun and a matching network in addition to the PA, LNa and RF switches which makes theinterface to the CC2530 seamless. Only a few components between the CC2530 andCC2591 necessary for RF matching For situation with extreme mismatch(VSWR 6: 1 till 12: 1out-of-band as shown in Figure 6.2) it is recommended to include all the components asshown in Figure 5.1ISTRUMENTSPage 9 of 19SWRA308ANote that the PCB transmission lines that connect the two devices also are part of the RFmatching. It is therefore important to copy the distance between the devices, the transmissionlines and the stack-up of the PCB according to the reference design to ensure optimumperformanceThe network between the CC2591 and the antenna(L111, C112, C111 C113 and L112matches the CC2591 to a 50 2 load and provides filtering to pass regulatory demands. C111also works as a dc-blockR151 is a bias resistor the bias resistor is used to set an accurate bias current for internaluse in the cc2591The TI reference design contains two antenna options. As default, the Sma connector isconnected to the output of CC2591 through a 0 Q2 resistor. This resistor can be soldered offand rotated 90 clockwise in order to connect to the PCB antenna, which is a planar invertedF antenna(PIFA). Note that all testing and characterization has been done using the SMAconnector. The PCB antenna has only been functionally tested by establishing a link betweentwo EMs. Please refer to the antenna selection guide [6] and the Inverted F antenna designnote [7 for further details on the antenna solutionsISTRUMENTSPage 10 of 19SWRA308A
- 2020-11-30下载
- 积分：1
