X-BAND MICROSTRIP YAGI ARRAY WITH DUAL-OFFSET APERTURE- COUPLED FEED

small-signal gain, for a given millimetre-wave output frequency, was essentially independent of the LO frequency whether the output was in the lower or upper sideband of the LO, as determined by the relationship between the LO and IF frequencies. The smallsignal gain of the transmitter is therefore shown in Figure 4 as a function of output frequency only. It can be seen that the smallsignal up-conversion gain falls approximately monotonically from 0 dB, for output at 176 GHz, to 15 dB, for output at 190 GHz. The large-signal behaviour of the module was measured at six output frequencies in the range 176 –191 GHz (in 3-GHz steps). LO and IF frequencies were chosen to give the appropriate output. Again, the performance was found (up to the 1 st order) to be independent of the LO frequency whether the output was in the lower or upper sideband of the LO, as determined by the relationship between the LO and IF frequencies. Figure 5 shows the millimetre-wave output power of the transmitter measured at 1-dB gain compression (1 dBc) and at output saturation. The figure also shows the corresponding output twotone, 3 rd -order intercept point for two input IF tones separated by 10 MHz. It can be seen that 1-dB gain compression occurs at an output power of 12 dBm at 176 GHz, decreasing to 20 dBm at 188 GHz. The saturated output power varies from 1 dBm at 176 GHz to 16 dBm at 188 GHz. The output 3 rd -order intercept point is 1 dBm at 176 GHz, decreasing to 12 dBm at 188 GHz. 5. SUMMARY This paper has described the design, fabrication, and test of a unique, double-sideband up-converting transmitter module for application in telecommunication links operating in the G-band. Using only InP and GaAs MMICs that can be readily fabricated commercially, the module exhibits wide bandwidth, useful output power capability, and linear characteristics. It should encourage the future development of a new generation of high-performance, millimetre-wave radio systems that take advantage of the spectrum available in the G-band. Such systems could deliver the multigigabit data rates needed for future-generation fixed, mobile, and personal communication needs.