Quick Links. Popular Categories. Our Network. Follow Us :. Need Help Finding a Product? Yes, I would like to receive weekly updates. Successfully Submitted! Our team will get back to you shortly.
Submit Another Query. Full Name. Your Company. Your Email. Please wait Please provide valid credentials. Create an account Create an account on everything RF to get a range of benefits. Enter Name. Enter Company. Enter Email. Enter Password. Create Account.
Already have an account? Sign In. Login Login to everything RF to download datasheets, white papers and more content. Forgot Password? Don't have an account? In baseband, envelope detector generates envelope by taking magnitude of IQ, which is. The magnitude of the signal is not the ideal signal for envelope tracking power supply. To obtain the maximum efficiency, the magnitude of the signal is often modified by shaping.
A shaping table is then developed to map the signal magnitude to the required voltage supply on the PA. This shaping table determines characteristics of ET system, so system designers spend a lot of time and effort to optimize shaping tables. For envelope tracking PA, the envelope tracking power supply and the RF input signal should be aligned strictly in time. Figure 1. Conventional PA block diagram With the pursuit of increased data throughput in limited radio frequency bandwidth, higher spectral efficiency is required.
Figure 2. Constant power supply for variable envelope The consequence of the PA inefficiency is very practical.
Each of these techniques has its advantages and disadvantages. Each technique has its own advantages and can be used to provide significant benefits under certain scenarios. Envelope tracking is able to offer some significant benefits in terms of efficiency, and general operation for RF power amplifiers used in many applications. Before looking further into the technology in this envelope tracking tutorial, it is worth looking at the background and need for the techniques like envelope tracking that improve RF amplifier efficiency.
In most RF amplifier applications, the efficiency of the amplifier has an impact on the design, operation and efficiency of the overall system. Power supply requirements, RF amplifier capabilities and heat-sinks are all affected by it. However with the increased use of battery power systems like smartphones, battery power consumption is a particularly important issue.
For any RF amplifier power is supplied to the circuit, and a signal is produced. The output will always be less than the DC input power, the ratio of output to DC input being the efficiency.
The efficiency of an amplifier depends upon the shape of the waveform and the mode in which it is operating. When operating in a linear mode, the output device must always be in conduction, with the output voltage rising and falling between the two limits. However in a real system the achieved levels are always below this. To achieve better efficiency levels, it is possible to drive the amplifier into compression.
Much greater levels of efficiency can be achieved, and if a steady waveform, like FM is used, the only degradation of the signal is that additional harmonics of the fundamental carrier are generated and these can be filtered out using RF filters. Unfortunately when modulation with an amplitude component is applied to a carrier this is distorted if it is passed through an amplifier that is run in compression. The situation becomes worse as if the peak to average ratio is high, i.
During the peaks, the amplifier requires the full voltage to be able to deliver the required power without running into compression, but during the periods of lower signal, this voltage is not required and means that power is dissipated in the device.
The amplifier only requires a smaller voltage to deliver the lower levels of power and therefore running with the higher voltage all the time, unnecessarily wastes power.
0コメント