Abstract: A receiver is provided that can shorten the time during which initial synchronization is established. When the frequency of an output signal from the PLL 12 is set to the receiving channel corresponding to the transmission channel for a transmission signal, the time-constant switching circuit 17 changes the time constant of the loop filter 14 to a low rate mode. Meanwhile, the output signal frequency from the PLL is swept between the highest frequency and the lowest frequency signal of a frequency channel. Thus, a receiving channel corresponding to the transmission channel is estimated by signals received during the sweeping period so that the initial synchronization is established based on the estimation result. Receiving-channel estimation, to which adverse effects due to multi-path fading are reduced, can be reliably performed by selecting each of plural receiving antennas in time-divisional mode and synthesizing envelopes of received signals from respective antennas.

Abstract: A receive antenna selection method and a diversity receive capable of preventing a deterioration in transmission efficiency in a multipath environment. A receive antenna for receiving a packet is selected during a period of time for which a preamble section of the packet is received, to thereby keep change-over between packets from being carried out during receiving of the packet. This eliminates a situation that a packet must be nullified due to generation of a bit error by change-over between receive antennas during receiving of the packet, to thereby keep transmission efficiency from being deteriorated even in a multipath environment.

Abstract: A spectrum spread communication system capable of preventing an increase in error rate irrespective of hit while keeping a communication speed from being reduced. A plurality of input data DS-modulated by a DS spread multiplier are fed to an array converter, wherein a first chip of each of the data is collected to form an FH first frame. Likewise, only second to seventh chips are collected to form FH second to seventh frames, respectively. The FH frames each are then subject to FH modulation in an FH spread multiplier and then transmitted. In a receive section, the data are returned to the original data array after FH demodulation, resulting in a burst error being a random error.

Abstract: A spectrum spread communication system capable of ensuring positive synchronization and improving error rate characteristics of data. At least one frequency is subject to hopping at an interval equal to one cycle of a DS signal during one cycle of frequency hopping and a cycle of changing-over of hopping is controlled depending upon an output signal of a correlation device, resulting in accomplishing synchronization.