The transmitter prototype chip was fabricated in a 90 nm CMOS process and packaged in a 64 pin QFN package. The chip micrograph and the testbench are shown in Fig. 5(a) and Fig. 5(b).
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The DACs generated quadrature pulses at 260 MHz or 700 MHz IF frequency using the templates stored in the high speed digital memories at a sampling speed of 2 GHz. The time-domain output of one of the four POH-DACs operating at 2 GS/s is shown in Fig. 6(a). The baseband pulse amplitudes are in the range 217-257 mVpp.
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The DFT of these pulses were taken after applying a Blackman window and the spectra in Fig. 6(b) show one of the baseband signals centered at 760 MHz. The sinc roll-off due to the windowed-integration attenuates its sampling image around 3.24 GHz by close to 30 dBc. The IF outputs from the complementary POH-DACs were interleaved during post-processing and this results in over 30 dBc attenuation of the image bands around 1.24 GHz and 2.76 GHz as well. Fig. 7 shows the up converted UWB pulses occupying four different bands.
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This work | [8] | ||
Bands | 3-5 GHz and above | 3-5 GHz | |
PRR | 100 MHz | 10 kHz - 16.7 MHz | |
Energy per pulse | 1.25 nJ | 9.6 nJ - 43 pJ | |
Spurs | Broadband Rejection | -42 dBc | -12 dBc |
LO feedthrough | -22 dBc | ||
Supply | 1.25 V | 1 V |