Tài liệu Lò vi sóng RF và hệ thống không dây P10 pdf

... wireless communications are frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA). Frequency division multiple access and TDMA are ... frequency band, and interference caused by intermodulation and sideband distortion. 10.3 TIME DIVISION MULTIPLE ACCESS AND TIME DIVISION MULTIPLEXING A TDMA or time division multiplexing (TDM)...

Ngày tải lên: 21/01/2014, 23:20

... possible spurious frequen- cies due to the two RF frequencies: f RF1 ¼ nf LO À f IF m ð5:29Þ f RF2 ¼ nf LO þ f IF m ð5:30Þ The RF frequencies of f RF1 and f RF2 will generate spurious responses. 5.8 ... generated. Any RF frequency that satisfies the following equation can generate spurious responses in a mixer: mf RF À nf LO ¼Æf IF ð5:28Þ where f IF is the desired IF frequency....

Ngày tải lên: 24/12/2013, 17:15

... various services such as voice mail, email, video, messaging, data, and computer on-line services. The direct link between satellites and personal communication systems can provide voice, video, ... to cable television, and the end of the Cold War has made many military technologies available to civilian applications. The global positioning systems (GPSs), RF identi®cation (RFID) systems, ....

Ngày tải lên: 24/12/2013, 17:15

... line < 300 20±50 Moderate High Low Poor Fair 13 CHAPTER TWO Review of Waves and Transmission Lines 2.1 INTRODUCTION At low RF, a wire or a line on a printed circuit board can be used to connect ... frequencies, the current tends to concentrate on the surface of the wire due to the skin effect. The skin depth is a function of frequency and conductivity given by d s  2 oms  1=2 2:1 whe...

Ngày tải lên: 24/12/2013, 17:15

... data. The second method is the cavity model [11]. This model assumes the rectangular patch to be essentially a closed resonant cavity with magnetic walls. The cavity model can predict all properties ... slot Since antennas interface circuits to free space, they share both circuit and radiation qualities. From a circuit point of view, an antenna is merely a one-port device with an associated ....

Ngày tải lên: 24/12/2013, 17:15

... looking at the device terminals (driving point) [1]. The impedance transformer network includes the device package and embedding circuit. The circuit impedance seen by the device is Z c ð f Þ¼R c ð ... resistance generates RF power from the DC bias supplied to the active solid-state device. Figure 4.35 shows a general oscillator circuit, where Z D is the solid-state device impedance and Z C...

Ngày tải lên: 24/12/2013, 17:15

... device impedance is a function of frequency ð f Þ, bias current ðI 0 Þ, generated RF current ðI RF Þ, and temperature ðTÞ. Therefore, at the resonant frequency, we have Im½Z D ð f ; I 0 ; I RF ; ... for space or battery operating systems. The DC-to -RF conversion efficiency is given by Z ¼ P RF P DC Â 100% ð6:4Þ where P RF is the generated RF power and P DC is the DC bias power. I...

Ngày tải lên: 21/01/2014, 23:20

... the target moving toward the radar and the minus sign for the target moving away from the radar. Let us consider the following two cases: The target is stationary, and the target is moving. 7.7.1 ... beat frequency at the receiving time (i.e., t 2 ). FIGURE 7.15 Block diagram of an FMCW radar. 7.7 FREQUENCY-MODULATED CONTINUOUS-WAVE RADAR 217 7.7.2 Moving-Target Case If the target is moving,...

Ngày tải lên: 21/01/2014, 23:20

... of stations provided a multiple-access technique is used. Frequency division multiple access (FDMA) will distribute links established at the same time among different frequencies. Time division multiple ... picture of this vision [8]. The WLAN is for wireless indoor radio communication services or high-data-rate communications. The system employs a central microcell hub (base station) that se...

Ngày tải lên: 21/01/2014, 23:20

... of modulation is always needed in an RF system to translate a baseband signal (e.g., audio, video, data) from its original frequency bandwidth to a specified RF frequency spectrum. Some simple modulation ... time-sharing transmission is called time division multiplexing. 3. The message is represented by a coded group of digital pulses. The effects of random noise can be virtually eliminate...

Ngày tải lên: 21/01/2014, 23:20