AN INTERPOLATED FREQUENCY-HOPPING SPREAD-SPECTRUM TRANSCEIVER

A technique of spread-spectrum transmission, interpolated frequency-ho pping (IFH), is presented, IFH employs a carrier that moves smoothly a nd continuously in frequency, helping to alleviate problems, such as s pectral splatter and transient mismatch, which are a concern in conven tional phase-locked loop (PLL)-based frequency-hopping spread-spectrum systems, In IFH, the pseudorandom hopping code is passed through a di gital interpolation filter prior to controlling the synthesizer instan taneous frequency output, While such filtering is commonly used in dat a pulse-shaping to improve the spectral characteristics of the modulat ed carrier, such filtering has not been reported for IFH codes, where the frequency deviations are changing and can span several MHz, The im plications of matching the transient responses of two PLL-based freque ncy synthesizers using this method have also not been reported, Initia l simulation and laboratory measurements indicate that, for certain ca ses, IFH shows a 1.9 dB improvement in received IF power, has a much s harper roll-off of inband phase noise when compared to conventional ho pping, and provides a phase-coherent IF after despreading. An IFH tran sceiver system using Delta-Sigma frequency synthesis and a Delta-Sigma frequency discriminator is proposed,The system would be suitable for integrated mobile radio applications in slow-fading environments.