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A radio transmitter design has to meet certain requirements. These include the frequency of operation, the type of modulation, the stability and purity of the resulting signal, the efficiency of power use, and the power level required to meet the system design objectives. [1]
4×4 array of 2.4 GHz patch antenna elements Patch antenna gain pattern. A patch antenna is a type of antenna with a low profile, usually consisting of a printed circuit board. It consists of a planar rectangular or circular sheet or "patch" of metal, mounted over a larger sheet of metal called a ground plane.
It is difficult to build multistage amplifiers, filters, and detectors that can have all stages track the tuning of different frequencies, but it is comparatively easy to build tunable oscillators. Superheterodyne receivers tune in different frequencies by adjusting the frequency of the local oscillator on the input stage, and all processing ...
Schematic of an AGC used in the analog telephone network; the feedback from output level to gain is effected via a Vactrol resistive opto-isolator.. Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the input.
(C) The bypass capacitor (C) is charged up by the current pulses from the diode, and its voltage follows the peaks of the pulses, the envelope of the audio wave. It performs a smoothing ( low pass filtering ) function, removing the radio frequency carrier pulses, leaving the low frequency audio signal to pass through the load R L .
In electronics, an antenna amplifier (also: aerial amplifier or booster) is a device that amplifies an antenna signal, usually into an output with the same impedance as the input impedance. Typically 75 ohm for coaxial cable and 300 ohm for twin-lead cable. An antenna amplifier boosts a radio signal considerably for devices that receive radio ...
The basic problem is the amplifying element is dissipating power. Switching Class C amplifiers are nonlinear, but they can be better than 50 percent efficient because an ideal switch does not dissipate any power. A clever design can use the nonlinear Class C amplifier for both gain and as a frequency multiplier.
Small-loop receiving antennas are also almost always resonated using a parallel-plate capacitor, which makes their reception narrow-band, sensitive only to a very specific frequency. This allows the antenna, in conjunction with a (variable) tuning capacitor, to act as a tuned input stage to the receiver's front-end, in lieu of a preselector.