A co-design study of low noise amplifier and band-pass filter

In this paper, the traditional 50Ω interface between the LNA (low-noise amplifier) and the BPF (band-pass filter) is removed, and a co-designed LNA-BPF is presented. The BPF is used to suppress the harmonics and acts as the matching network of LNA. The measured results show, at 2.5GHz, the co-designed LNA-filter achieves a voltage gain of 15.04 dB, a noise figure of 3.9 dB, 3^rd harmonic suppression of 66.17dB and P_I1dB of -13dBm. Compared with traditional versions with 50Ω interfaces, the co-designed version obtains a large voltage gain, better P_I1dB and 3^rd harmonic suppression and is more compact. Good agreement between the measured and simulated results is achieved.

I. Introduction

With the rapid development of wireless communications technology, RF front-end has been put forward high requirements. Nowadays, there are two methods to improve the performance of RF front-end, including system-level packaging of RF systems (passive and active components or subsystems are integrated into one device to realize the system in one package) and co-design for RF front-end (the traditional interface between the LNA and band-pass filter is removed to realize multi-function in one device) [1]–[5]. The co-design can essentially change the structure of the circuit, combine the function of the circuits and simplify the connection between the components. In ref. [1], a RF antenna-filter-LNA co-design strategy was presented. By co-design, the noise figure was improved significantly. In ref. [2], [3], antennas were co-designed with amplifier and transceivers, and the integration were improved significantly. Also, a device acted as a matching network, balun, and an extracted-pole band-pass filter was proposed in [4]. In [5], the oscillator was co-designed with filters, and the noise levels and harmonic suppression is improved effectively.