In this chapterFrequency scanning antenna, frequency scanning antennasAntennas with outstanding properties such as high directivity, wide frequency scanning, and simple feeding mechanism are discussed. Different types of frequency scanning antennasFrequency scanning antenna such as traveling wave and standing wave antennasStanding wave antenna are elaborated in this chapter. The method to achieve high gainMethods to achieve high gain and compact spoof surface plasmon polariton-based leaky-wave antenna is presented. The standing wave antennaStanding wave antenna used to realize a compact scanning antenna is discussed in detail in this chapter.