A 10.7-MHz CMOS SC radio IF filter using orthogonal hardware modulation

Abstract

Abstract-FM radio receivers require an IF filter for channel selection, customarily set at an IF center frequency of 10.7 MHz. Up until now, the limitations of integrated radio selectivity filters in terms of power dissipation, dynamic range, and cost are such that it is still required to use an external ceramic 10.7-MHz bandpass filter. This paper demonstrates a CMOS switched-capacitor IF filter that can be integrated with most of the rest of the FM receiver, eliminating external components and printed circuit board area. This is made possible through a combination of two techniques: orthogonal hardware modulation, and delta-charge redistribution. It exhibits a tightly controlled center frequency with a of 55 and also contains a programmable gain. The filter occupies an area of 0.7 mm 2 in a 0.6-m CMOS process with poly-poly capacitors. The new filter requires only 16 mW of power, and this is offset by elimination of the power needed in current designs to drive off-chip filters.

A 10.7-MHz fully balanced, high-Q, 87-dB-dynamic-range current-tunable Gm-C bandpass filter

“…8 The quality factor Q HQ versus ambient temperature for the uncompensated and compensated cases Table 4 Comparisons of the proposed Gm-C bandpass filter and existing Gm-C approaches Performance This design Tajalli and Atarodi [9] Chung-Yu and Chung-Yun [10] Munoz et al [11] Stevenson and Edgar [12] Steyaert and Silva-Martinnez [13] Hernandez-Garduno and Silva-Martinez [3] Silva-Martinez et al [4] Hammouda [5] Quinn et al [6] Nagari and Nicollini [7] Nagari et al [8] Design techniques Technologies…”

“…Recently, attempts at possible on-chip filters have particularly been demonstrated for 10.7-MHz IF filters based on, for example, switched capacitors (SC) [3][4][5][6][7][8], and Gm-C [9][10][11][12][13] techniques. Such techniques have, however, repeatedly suffered from low quality (Q) factors from 10 to 55, high total noise from 226 to 707 lV rms and limited dynamic ranges from 58 to 68 dB.…”

Optimum design and implementation of IIR SC filters using small-order FIR cells

“…The design of IIR SC filters for narrowband applications is a formidable challenge, mainly because the poles are clustered close to the unit circle inside the (narrow) passband. Specific approaches addressing this problem include -path [7], [8], polyphase [9] and interpolated FIR [10] structures.…”

A 10.7-MHz fully balanced, Q-of-267, 103-dB-dynamic-range current-tunable bandpass filter

“…As off-chip filters are bulky and consume more power to drive external devices, the need for on-chip filters for viable fully integrated receivers has increasingly been motivated. Recently, attempts on on-chip filters have particularly been demonstrated for 10.7-MHz IF filters based on, for example, continuous-time (CT) [2][3][4][5][6] or switched capacitors (SC) [7][8][9][10][11][12] techniques. Such techniques, however, have repeatedly suffered from low quality (Q) factors (between 10 to 55), limited dynamic ranges (between 58 to 68 dB) and high total output noise (between 226 to 707 µVrms).…”