应用于GPS接收机的宽动态范围连续VGA

A Wide Dynamic Range Continuous VGA Applied in GPS Receivers

针对全球定位系统(GPS)接收机中宽动态范围的要求,提出了一种伪指数近似可变增益放大器(VGA)。该VGA在改进的吉尔伯特单元基础上,采用电压-电流转换电路构成伪指数函数,通过两级级联方式来实现宽线性增益范围,且电路结构对温度不敏感。测试结果表明,当控制电压在0.41.45V变化时,该VGA的线性增益范围为2080dB。在50dB线性增益范围内,增益随温度变化的最大偏差不大于±1.5dB。

A pseudo-exponential variable gain amplifier（VGA）with wide dynamic range for global position system（GPS）receiver was implemented.On the basis of the improved Gilbert cells,a voltage-current conversion circuit was used to implement the pseudo-exponential function.The wide linear gain range was realized by the two cascade stages which were independent of temperature.Measurement results showed that the VGA gain increased linearly from 20 dB to 80 dB with the control voltage changing from 0.4 V to 1.45 V,and the maximum gain variation was less than ±1.5 dB during 50 dB linear range.