A CMOS channel-select filter for a direct-conversion wireless receiver

New high-Q discrete-time LC bandpass filter design with center frequency broadband tuning

“…The switches are successively closed with a switching period To, during a time To/N. When, the command signals of the switches are considered to be Dirac's impulses δ(t) spaced by a To period, then, in the frequency domain, the output signal S(f) can be written as function of the input signal E(f): Equation (1) shows that the total transfer function H s (f) of the classical pseudo switched-capacitor filter is the result of the transfer function of the basic cell (1 rt order low-pass filter) transposed around the center frequency (Fo = 1/To) and all their harmonic components.…”

“…Wireless transceivers are an increasingly important commercial application [1,2]. The current transceiver solutions often use low cost CMOS for digital and baseband circuitry, while reserving silicon bipolar or GaAs for critical radio frequency (RF) circuits.…”

Multistandard Analogue Baseband Filters for Software-Defined and Cognitive Radio Receivers

“…Although there have been a few papers that have implemented baseband channel-select filters using BiCMOS [5,37], CMOS has been almost exclusively used, which is also the focus of this paper. Traditionally, baseband filters in CMOS are realized using the switched-capacitor (SC) technique [7], where the filter response is defined by component ratios and a precise clock frequency. However, biasing MOS switches fully on or off, and maintaining proper operational amplifier (Op-amp) operation is difficult to achieve in SC circuits with reduced supply voltage.…”

“…Reference [3] also designs an inverse Chebyshev filter. A mixed use of different functions is also possible: for example, reference [7] uses a 6 th -order elliptic function for channel select and a 2 nd -order Butterworth function as prefilter. Multiple frequency responses from a single reconfigurable filter structure can also be achieved such as Chebyshev/Inverse Chebyshev [3], Chebyshev/elliptic [36], and Butterworth/Chebyshev/ elliptic [25].…”

“…Also, less complex lower-order filters can provide ease of design, have less noise and reduced parasitic effects. The order of filters adopted in the literature ranges from 3 rd [3,5,6,20,28,36] [4,7,33] order, with most using the 5 th -order to best trade off frequency response and circuit complexity. For multistandard receivers, references [3, 6, 20, and 36] have also presented an order-adaptable filter system which can realize 3 rd -and 5 th -order filters for different standards to reduce chip area and power consumption.…”