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Next: Acknowledgment Up: index Previous: POH DAC and Quadrature Up Conversion Mixer

Measurements [7]

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).

Figure 5: (a) Chip photograph. Active area is 0.65 X 0.76 sq-mm. (b) Test-bench for measuring POH-DAC outputs and the UWB pulses.
[a] Image IRuwbTx07 [b] Image uwbtest

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.

Figure 6: (a) Measured time-domain baseband pulses corresponding to I-memory and sampled at 0 degree phase of clock at fs = 2 GHz. (b) DFT of the measured baseband pulse (-), centered at 760 MHz, generated using a 2 GHz POH-DAC, is compared with the sinc filter (-.-) (null around 3.4 GHz) on top and with the interleaved pulse at the bottom. Top: POH effect attenuates the image around 3.24 GHz by 30 dBc. Bottom: In the interleaved output (-o-), the images at 1.24 GHz and 2.76 GHz are reduced by 30 dBc.
[a] Image pohA_I1_TD_noclr [b] Image basebandAB_I_selC_noclr

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.

Figure 7: Measured UWB pulses (without any filtering) centered at 3.3, 3.74, 4.26 and 4.7 GHz are shown (a) in the time domain and (b) with respect to a normalized FCC mask (-.-) in the frequency domain.
[a] Image 4uwbCHs_TD_noclr [b] Image 4uwbCHs_FD_noclr




Table 1: Performance summary: UWB Pulse Transmitter
  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


next up previous
Next: Acknowledgment Up: Index Previous: POH DAC and Quadrature Up Conversion Mixer
Anuranjan Jha 2009-01-30