its corner frequency at 100 kHz and a high-frequency attenuation of -15dB. This highpass feedback path corresponds with the fact that it typically arises due to capacitive current injections. The desired downconversion behavior from f = fo to baseband is described by the HTM element H0,1(s) and is computed to be (4.106) H2(s)H1(s+jwo)Hfb(s)Hfb(s+jwo) This result is accurate up to 2nd order in while taking 7 tones into account. In expression (4.106), the first term describes the intended signal transfer, while the other terms can be considered as linear distortion components due to the parasitic feedback filter Hfb(s). The downconversion behavior from f = 0 and f = 2fo to baseband is respectively modeled by the HTM elements (4.107) (4.108) From (4.107), it is observed that, with H1 (s) being a bandpass filter centered around W0, Hoo(s) ~ H1(s) vanishes almost completely at low frequencies. On the other hand, equation (4.108) shows that, for a given feedback path Hfb(s), the order of magnitude of H0,2 will be largely determined by H1 (2jwo). In order to get H0,2 (s) as low as possible, it is advantageous to design the upper (high-frequency) stopband characteris- tic of H1 (s) as steep as possible. For a given filter order, this suggests an asymmetric filter design with the majority of the filter zeros located in the upper stopband. This will result in an increase of Ho,o(s) as compared to a symmetric design, but as long as 4.3.8 Application 2: Receiver stage with feedback across the mixing element HTM element Relative error H0,1 (s) -78.0 dB H0,0 (s) -41.1 dB ,((s) -35.9 dB Table 4.3: Relative accuracy of the symbolically computed receiver HTM elements (4.106)-(4.108) with respect to results obtained by direct numerical extraction. the bandwidth of the lowpass filter H2(s) is much smaller than W0, this won't matter much. Fig. 4.29 plots the HTM elements with H1 (s) respectively being a symmetric and an asymmetric bandpass filter. H (s) being symmetric means that it has two zeros at W = 0 and two zeros at W = 8. H1 