Design and testing of a mixed signal matched filter for IS-95 CDMA code acquisition

Due to its advantages in multiple access, interference rejection, multipath mitigation, and access security, the direct-sequence spread spectrum (DS-SS) become very popular in mobile communication. For code acquisition of DS-SS signals, matched filters are the key components. This paper presents the design, implementation, and testing of a mixed signal matched filter. The proposed filter uses simple current mirrors to reduce the complexity of the crucial summation circuitry. The circuit is small in size and regular in structure; hence, one can cascade several to produce a filter of longer length. A 128-tap test chip has been implemented in a 2.5 mm² core by means of 0.8 μm SPDM digital CMOS technology. The DC and AC measurements confirm the feasibility of the design.