A comprehensive method applying a nonlinear frequency compression (FC) as complementary to multiband loudness compensation is proposed, which is able to improve loudness compensation and simultaneously increase high-frequency speech intelligibility for digital hearing aids. First, to avoid the spectral distortions in the sounds, speech intelligibility-based frequency spectrum splitting is introduced. Then a nonlinear FC (NLFC) is also proposed to compress the high-frequency sounds to the lower bands where the audibility is available. Moreover, the introduced NLFC adjusts compression ratio (CR) based on the speech intelligibility percentage in different frequency ranges. Finally, an adaptive wide dynamic range compression (AWDRC) with a time-varying CR is applied to achieve adaptive loudness compensation, and prevent the stationary CR of the typical wide dynamic range compression (WDRC) from generating a negative impact on the speech. The experimental test results show that the mean speech identification is improved at least 20% points in comparison with the typical WDRC or the conventional FC.

A baseband transmitter for UHF (ultra high frequency) RFID (radio frequency identification) reader is proposed, which supports ISO 18000-6B&6C protocol and works at 840-960 MHz. Taking security and compatibility into consideration, 2-bits PIE-kind encoder and PIE encoder are both implemented, the former is 6 times higher security than the later. In SSB modulation, when there is amplitude mismatch of two quadrature signals, it will generate two frequency bands and result in performance lost. For this problem, an amplitude matching module is integrated. A power adjustment module in baseband is also proposed to enhance the signal and get larger input signal for PA to generate larger PA output power. The whole reader chip is implemented in a 0.18μm CMOS process and consumes 209461 gates and 102.609 mW. The baseband transmitter takes up 22% of the total area. This novel architecture doesn’t bring much lost in area and power consumption compared with other existing designs.