Sampling and analog despreading of a DS/SS modulated signal directly on the IF waveform
(English)Manuscript (preprint) (Other academic)
This paper introduces a method how to interpret the user data directly from a direct-sequence spread quaternary-phase-shift keyed (DS/QPSK) modulated wave-form without first demodulate nor digitize the waveform. The Methos is to sample the waveform, to weight each individual sample with -1, 0, or +1 according to the spreading code, and finally to accumulate these weighted samples. The wave-form carrier frequency is chosen as a multiple of the chop rate. This demonstrated with a 0.6μm CMOS test chip that is fed with a 2Mchip/s DS/QPSK modulated signal, shaped with a Root-Nyquist filter. The measurement result cerifies correct interpreting of transmitted data symbols (user data) represented over seven chips. The test chip further exhibit a measured noise figure 16.2dB at a bandwidth expansion of 7.
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-86799OAI: oai:DiVA.org:liu-86799DiVA: diva2:582408