| 摘要 |
PROBLEM TO BE SOLVED: To improve receiving performance of the receiver of a direct conversion system by modulating a demodulating local signal by a pseudo noise signal to mix to a reception signal and inversely spreading the nixed signal by the pseudo noise signal to make a base band signal. SOLUTION: Since waves outputted from respective transmitter 21 andπ/2 phase shifter 22 become local signals spread by multiplying by the respective pseudo noise signals PNc/PNs and supplied to respective mixing circuits 14I/14Q. Then the mixed output of the mixer circuits 14I/14Q is supplied for inverse conversion circuits 16I/16Q respectively through low-pass filters 15I/15Q. A pseudo noise signal PNc outputted by a PN code generation circuit 24 is supplied for the circuit 16I and the demodulated signal of an I component obtained by inversely spreading the demodulated signal by multiplying this pseudo noise signal PNc is made a base band signal. On the other hand, pseudo noise signal PNs outputted by a PN code generation circuit 25 is supplied for the circuit 16Q and the demodulated signal of a band spread I component is made a base band signal.
|
