A 7-GHz-band subminiature FPU transmitter

A compact, low-cost, light-weight field pick-up (FPU) transmitter developed for emergency news gathering is described. It consists of a 7 GHz band FET direct frequency modulator and a flat-panel antenna. The modulator uses a FET, a dielectric resonator, and two varactors. The use of two varactors magnetically coupled with the dielectric resonator results in good modulation linearity and, therefore, a linearizer before the modulator is not required. The modulator has an output power of 22 dBm, differential gain of less than 3%, and differential phase of less than 2°. The antenna is constructed of four rectangular microstrip patches on a Teflon-glass substrate and has outer dimensions of 90 mm×90 mm and a gain of 13 dBi. The dimensions of the transmitter are 60 mm×45 mm×90 mm and the weight is 300 g. Using the transmitter with a 4 dB noise-figure receiver and a 60 cm diameter parabolic receiving antenna, the unweighted signal-to-noise ratio obtained for an NTSC TV signal is 42 dB after a 10 km transmission