甚小线性调频键控（very minimum chirp keying,VMCK）调制方式具有超窄带特性.采用连续相位调制的一般分析方法，选用线性信号作为积分脉冲，给出VMCK的连续相位调制表达式，并构造出一种新型的发射机结构.推导VMCK信号的归一化功率谱密度公式，以功率百分比带宽为考核准则，证明在正交二元信号下，VMCK比最小频移键控(minimum shift keying,MSK)具有更窄的主瓣宽度和更低的旁瓣能量，即带宽更具有效性.

The very minimum chirp keying (VMCK) modulation possesses characteristics of an ultra narrow band (UNB). This paper uses a general analysis method of continuous phase modulation (CPM) to select a linear signal as the integral pulse, give the continual phase modulation express of VMCK, and construct a new kind of the VMCK transmitter structure. The normalization power spectral density formula of VMCK is then derived, with the power percentage bandwidth as an inspection criterion. It is proven that, for an orthogonal binary signal set, VMCK has a narrower main lobe compared with the minimum shift keying (MSK) modulation. Therefore better band width efficiency can be achieved with VMCK.