Digital spread spectrum GPS navigation receiver

For use in a CDMA receiver in which spread spectrum signals are correlated with a plurality of known reference codes to recover a plurality of (k) sum-of-product observations of each of a plurality of (n) said signals, the relative carrier phase offsets and motion of said signals being nominally independent from signal to signal, a multiplex accumulator comprising:

• phase estimating means for sequentially developing a plurality of carrier phase offset estimates, .phi.(i) (t), one for each of said plurality of (n) signals,
• a mechanism for receiving a plurality of (k) complex partial sum of product inputs for each of a plurality of (n) signals, S(1 . . . n, 1 . . . k), wherein all inputs for any one signal are nominally measured relative to said carrier phase offset estimate, and sequentially selecting exactly one of said inputs, S(i,j),
• rotator means for sequentially receiving and rotating said selected input, S(i,j) to provide a complex product, Y(i,j), in which said carrier phase offset estimate, .phi.(i) (t) is removed,
• an adder for receiving and summing said product, Y(i,j), with a previous accumulation of complex sum-of-products from said adder, YS(i,j) (t-1), to produce an updated sum-of-products, YS(i,j),
• a memory for storing the accumulated sums-of-products, YS›i,j!, from said adder for further accumulation and later retrieval, and
• a multiplexer for sequentially applying sums of products from said adder to said memory.

A receiver for a plurality of (n) spread spectrum signals, wherein the relative carrier phase offsets and motion of said signals are nominally independent from signal to signal, comprising:

• an antenna for receiving said spread spectrum signals,
• means for filtering and amplifying said spread spectrum signals and producing a plurality of (k) complex partial sum of product observation inputs for each of a plurality of (n) said signals, S(1 . . . n, 1 . . . k), wherein non-negligible residual relative carrier phase offsets and motion may be retained in said inputs,
• phase estimating means for sequentially developing a plurality of (n) estimates of said residual carrier phase offset, .phi.(i) (t), one for each of said plurality of (n) signals, said phase estimating means including
• memory for storage of carrier phase estimates, .phi.i, and carrier frequency numbers, Fni, for each signal, and a means for carrier phase accumulation by receiving carrier phase estimate, .phi.i(t-1), and carrier frequency number, Fni, from said memory and summing them to produce an updated carrier phase estimate, .phi.i(t), for return to said memory for further accumulation and later retrieval,
• a mechanism for receiving said signals, S(1 . . . n, 1 . . . k), and sequentially selecting exactly one, S(i,j),
• a rotator means for sequentially receiving and rotating said selected input, S(i,j), to provide a complex product, Y(i,j), in which said carrier phase offset, .phi.(i) (t), is removed,
• an adder for receiving and summing said product, Y(i,j), with a previous accumulation of complex sum-of-products from said adder, YS(i,j)(t-1), to produce an updated sum-of-products, YS(i,j) (t), and
• memory for storing the accumulated sums-of-products, YS(i,j), from said adder for further accumulation and later retrieval,
• wherein said phase estimating means sequentially reuses the adder and memory functions used for sum-of-product accumulation.

A receiver for a plurality of (n) spread spectrum signals, wherein the relative carrier phase offsets and motion of said signals are nominally independent from signal to signal, comprising:

• an antenna for receiving said spread spectrum signals,
• means for filtering and amplifying said spread spectrum signals and producing a plurality of (k) complex partial sum of product observation inputs for each of a plurality of (n) said signals, S(1 . . . n, 1 . . . k), wherein non-negligible residual relative carrier phase offsets and motion may be retained in said inputs,
• phase estimating means for sequentially developing a plurality of (n) estimates of said residual carrier phase offset, .phi.(i) (t), one for each of said plurality of (n) signals,
• a mechanism for receiving said signals, S(1 . . . n, 1 . . . k), and sequentially selecting exactly one, S(i,j),
• a rotator means for sequentially receiving and rotating said selected input, S(i,j), to provide a complex product, Y(i,j), in which said carrier phase offset, .phi.(i) (t), is removed,
• an adder for receiving and summing said product, Y(i,j), with a previous accumulation of complex sum-of-products from said adder, YS(i,j) (t-1), to produce an updated sum-of-products, YS(i,j) (t),
• memory for storing the accumulated sums-of-products, YS(i,j), from said adder for further accumulation and later retrieval, and
• a multiplexer for sequentially applying sums of products from said adder to said memory.