## BPSK

The equation representing a sine wave is as follows: $$A\cos(2\pi ft +\phi)$$ From above equation, it can be see that we can making changes to the amplitude, frequency, and phase of a sine wave to encode information. However, as frequency is the first derivative of phase, so frequency and phase of the sine wave equation can be collectively referred to as the phase angle. 请输入链接描述 Amplitude Modulation $$\sin(x)\sin(20x)$$ I/Q data RF communication systems use advanced forms of modulation to increase the amount of data that can be transmitted in a given amount of frequency spectrum. BPSK stands for Binary Phase Shift Keying. It is digital modulation technique. The code main from: Jaseem Vp Below is the Matlab code A=5; t=0:.001:1; f1=5; f2=3; N=length(t); ip = rand(1,N)>0.5; x=A.*sin...

## 平行板间自然散热计算

Bar-Cohen and Rohsennow Solution Finned surfaces of various shapes, called heat sinks, are frequently used in the cooling of electronic devices. Energy dissipated by these devices is transferred to the heat sinks by conduction and from the heat sinks to the ambient air by natural or forced convection, depending on the power dissipation requirements. Natural convection is the preferred mode of heat transfer since it involves no moving parts, like the electronic components themselves. However, in the natural convection mode, the components are more likely to run at a higher temperature and thus undermine reliability. A properly selected heat sink may considerably lower the operation temperature of the components and thus reduce the risk of failure. Natural convection from vertical finned ...

## NATURAL CONVECTION:NATURAL CONVECTION FROM FINNED SURFACES AND PCBs

Natural convection flow through a channel formed by two parallel plates as shown in Fig. 20–16 is commonly encountered in practice. When the plates are hot (Ts> Too), the ambient fluid atToo enters the channel from the lower end, rises as it is heated under the effect of buoyancy, and the heated fluid leaves the channel from the upper end. The plates could be the fins of a finned heat sink, or the PCBs (printed circuit boards) of an electronic device. The plates can be approximated as being isothermal (Ts= constant) in the first case, and isoflux ( · = constant) in the second case. Boundary layers start to develop at the lower ends of opposing surfaces, and eventually merge at the midplane if the plates are vertical and sufficiently long. In this case, we will have fully developed c...