Vesa Lehtinen

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In order to obtain a higher spectral separation from the BPSK-like signals, i.e. GPS C/A code, the signals proposed for future Galileo and GPS M-code signals are processed using split-spectrum type modulations, such as Binary Offset Carrier (BOC) modulation. These BOC modulations create deep fades (ambiguities) in the envelope of the Autocorrelation(More)
In radio frequency (RF) power amplifiers (PA), power efficiency, linearity and cost are contradictory requirements. In the Long Term Evolution (LTE) and LTE-Advanced (LTE-A) standards by the Third Generation Partnership Project, maximum power reduction (MPR) is used to relax RF PA requirements in user equipment. In this paper, we analyze the gating factors(More)
In frequency division duplex transceivers employing non-contiguous carrier aggregation (CA) transmission, achieving sufficient isolation between transmit and receive chains using radio frequency filtering alone is increasingly difficult. Particularly challenging problem in this context is spurious intermodulation (IM) components due to nonlinear power(More)
In this paper, the impulse response symmetry of Farrow interpolation filters and its significance in rational sample rate conversion is addressed. Four methods for ensuring impulse response symmetry are proposed. Comparison of different symmetrization schemes is made, with filters optimized based on the discrete-time impulse response model. The results(More)
Carrier aggregation transmissions in frequency division duplexing devices reduce the duplexing distance between the transmitter (TX) and receiver (RX) bands. As a consequence, the spurious intermodulation distortion products created by the nonlinear RF front-end of the TX may easily extend over to the RX band, potentially causing own RX desensitization. In(More)
The cascaded integrator-comb (CIC) filter is an efficient multiplier- free structure for decimation and interpolation. However, due to its narrow stopband notches, it is useful only when the signal of interest has a small bandwidth compared to the input and output sample rates. Consequently, it can only be used in the first (last) few stages of multistage(More)
Interpolation filters are used to interpolate new sample values at arbitrary points between existing discrete-time samples. An interesting class of such filters is polynomial-based interpolation filter. These filters can be efficiently implemented using the Farrow structure and its modifications. Traditionally, the polynomial based interpolation filters(More)
The variable fractional-delay (FD) filter structure by Tassart and Depalle performs Lagrange interpolation in an efficient way. We point out that this structure directly corresponds to Newton’s interpolation (backward difference) formula, hence we prefer to refer to it as the Newton FD filter. This structure does not function correctly when the fractional(More)