Design of a reconfigurable active filter chip

doi:10.3969/j.issn.1000-5641.2022.02.017

Abstract

Abstract:

Recently, research on multi-mode, multi-band transceivers has garnered significant interest; in this context, the Software-Define Radio (SDR) system is considered a good candidate. To reduce the negative influence of out-of-band interference on transceiver performance of the SDR system, a high out-of-band rejection IF (intermediate frequency) filter with tunable bandwidth and programable gain is proposed. The proposed filter consists of a biquadratic Gm-C filter, a gain-boosting stage, and a 5th-order elliptic filter. In the proposed filter, the variable gain is achieved using a biquadratic Gm-C filter and a gain-boosting stage, and the tunable bandwidth is achieved using capacitor arrays. In addition, a 5th-order elliptic filter is added to improve out-of-band rejection. The post-layout simulation shows that the bandwidth is tuned over a range of 1 MHz–30 MHz, and the minimum out-of-band rejection at twice the bandwidth reaches 44.56 dB. The gain control range is from –20 dB to 20 dB, and the power consumption and active area for the analog counterpart is 5.1 mW and 1.23 mm², respectively. The proposed filter is suitable for the analog front-end of multi-mode communication terminals.

Key words: active filter, bandwidth tunable, gain programable, high out-of-band rejection, low power consumption

CLC Number:

TN713

Junwei YU, Shengxi DIAO. Design of a reconfigurable active filter chip[J]. Journal of East China Normal University(Natural Science), 2022, 2022(2): 143-154.

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带宽/MHz	阻带幅度最大时的频率/MHz	阻带幅度最大时的带外抑制/dB	2倍带宽频率的带外抑制/dB
30.21	69.18	62.59	68.90
20.10	53.70	54.84	68.82
15.19	37.15	49.62	54.35
10.03	22.91	47.62	49.58
5.02	11.48	47.76	49.34
1.03	2.24	43.93	44.56

低频增益/dB	带宽/MHz	阻带幅度最大时的频率/MHz	阻带幅度最大时的带外抑制/dB	2倍带宽频率的带外抑制/dB
20.01	10.03	22.91	47.63	49.59
10.22	10.05	23.44	46.24	48.32
0.12	10.05	23.44	46.21	48.34
–9.89	10.07	22.91	45.52	47.50
–19.83	10.10	22.91	45.13	46.81

参考文献	带宽调节范围	两倍带宽频率的带外抑制/dB	增益调节范围/dB	功耗/mW	核心面积/mm²
本文	1 MHz ~ 30 MHz	44.56	–20 ~ 20	5.1	1.23
[1]	30 MHz	42.00		85.0	1.40
[2]	44 MHz ~ 300 MHz	41.00		54.0	0.63
[3]	500 kHz ~ 14 MHz	13.00		6(@500 KHz)
[4]	28 MHz ~ 2.8 GHz	25.00		3.3/17.4	0.04
[9]	1.73 MHz ~ 27.25 MHz	24.00		1.92 ~ 5.98