Transducer

A transducer which can provide wider relative bandwidth is provided. The transducer (2) is provided with an oscillator (20) and a broad band matching circuit (10), wherein in the oscillator, a peak frequency (fp) corresponding to a peak transmission sensitivity (pp) may separate from a centre frequency (fc) within a given bandwidth, and a transmission sensitivity (SE) may increase as a frequency (f) separates from the peak frequency (fp) with respect to the centre frequency (fc). The broadband matching circuit performs an impedance matching such that the transmission sensitivity (SE) of the oscillator (20) at the peak frequency (fp) becomes substantially equal to the transmission sensitivity (SE) of the oscillator (20) at the centre frequency (fc). 本发明提供能够使相对带宽更宽的收发器。收发器(2)具有：振子(20)，与峰值发送灵敏度(pp)对应的峰值频率(fp)从规定频带的中心频率(fc)偏离，随着频率(f)以中心频率(fc)为基准从峰值频率(fp)远离而发送灵敏度(SE)增高；以及宽带化匹配电路(10)，进行阻抗匹配以使峰值频率(fp)处的振子(20)的发送灵敏度(SE)与中心频率(fc)处的振子(20)的发送灵敏度(SE)大致相等。