| 摘要 |
PURPOSE: To effectively utilize a frequency by changing a channel band width corresponding to the kind of data in a radio LAN system for using a frequency hopping type spread spectrum communication system. CONSTITUTION: In transmission, the data are band-limited in a BPF 218, inputted to a VCO inside a frequency synthesizer 226, FSK modulated, then mixed with carrier signals by an up converter 211, gain-adjusted in a transmission amplifier 209, passed through the BPF 206 and transmitted. At the time, whether the transmission data are a low rate or a high rate is discriminated in a controller 203, and in the case of low-rate data, the frequency division counter value of a hopping PLL 217 is changed, the frequency step of a synthesizer 202 is turned to 1/2, the filter of a 2nd IF is switched to a 221b provided with the passing band of the 1/2 of the BPF 221a, the free channel of a 1/2Fw band is searched and the transmission is performed. Thus, an excessive frequency band is not uselessly assigned to the low-rate data and the frequency is effectively utilized. |
