This report was undertaken to see how the transmission of asymmetrical sideband power would benefit digital receivers in terms of the digital signal-to-noise ratio. It was done in the laboratory using three particular chipsets that iBiquity characterizes as being typical in both the OEM and aftermarket: the ST Micro STA-680, the Texas Instruments Jacinto, and the NXP SAF3560. The tests were done with IRSS 4.4.x PAR v.2 (A late news update: IRSS 4.4.x PAR v.2 was delivered to manufacturers on Jan. 17, 2012).

Four sets of measurements were taken; P1 partition with no interference, and P1 partition with 6dB D/U interference on the lower adjacent channel; and P3 partition, with no interference, and with 6dB D/U interference on the lower adjacent channel. Those measurements are shown in Figures 1, 2, 3 and 4 respectively. Interpreting these is easy; along the left-hand column you see the scale is decibels over the -20dBc (legacy) reference. The black bar is the difference in power with respect to the legacy power, calculated for each LSB to USB ratio. The colored bars represent the actual measured receiver performance, in decibels, as an improvement in digital SNR.

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The conclusion to be drawn from these charts is that the increase in overall digital power (even asymmetrically) does produce an improvement in the digital signal-to-noise ratio.

- continued on page 5