Homemade television signal transmitter circuit
Abstract : achieving a fully integrated IF variable -bandwidth broadband low-pass filter , discussion and analysis of the transconductance amplifier – the structure of the capacitor (OTA-C) continuous-time filter design and implementation , use an external programmable circuit designed to control the filter bandwidth , and use ADS software for circuit design and simulation. Simulation results show that the adjustable range of the filter bandwidth is 1 ~ 26 MHz, stopband rejection greater than 35 dB, in-band ripple of less than 0.5 dB, a 1.8 V power supply , TSMC 0.18μm CMOS technology library emulation , consumes less than 21 mW, frequency response curve close to the ideal state. Keywords : Butte
homemade television signal transmitter circuit
television transmission circuits and working principle:
the principle wideband low-power television transmitter circuit is the RF signal sent by the 75 ohm RF cable has a C1, a high pass filter L1, C2 consisting of the filter out frequencies below 45MHZ , then the pre-amplifier via the transistor 9018 to the other components of the amplification by the capacitor C3 upc1651 power amplifier, the output signal of about 60cm whip antenna out . 7805 like the instructions provided supply voltage 5V power supply for upc1615. Selection produced upc1651 high frequency amplification integrated circuits for high gain , low -noise 9018 UHF transistor , C1, L1, C2 constitute a cutoff frequency of 47MHZ high-pass filter . Choose high-frequency ceramic capacitors are capacitors with ordinary carbon film resistors resistance. IC2 and other components to provide 5V power supply and power indicator. L1 production is 3mm in diameter cylinder with a 0.2mm enameled wire tightly wound 16 laps bodiless. Antenna with a 60cm whip antenna. because this machine to work in ultra-high band, in the design and production of PCB, component configuration and lead length must comply with the requirements of high-frequency design, although short of the welding wire to close the circuit board prevail, unlimited electronic production networks in the design of this miniaturized components are used when, circuit, plastic box can be installed in the site provides 47x33x16mm . Power supply 9V DC power supply is used, placed in the living room or do not account for how much space they can not have more than one television signal line home exchange can refer friends make
debug the transponder circuit can also be placed in a small iron box may also be placed in a waste of the VHF tuner as long to remove the mechanical and electronic components which become a shielded box. Because transponder circuit is simple , very few components can be soldered directly to the circuit elements board and make sure the connection is correct, correct welding ! machine operating current of about 25MA. 9018 operating current of about 5MA, can be adjusted by R1. recorders , VCD and other appliances should be selected RF output cable 75 ohm coaxial cable length as short as possible , using fully shielded [ including joints ] , thus reducing interference RF antenna as long as elements of quality assurance , the transmitter can work properly.