Input and output filtering system for a direct conversion receiver

• US 7,155,195 B2
• Filed: 06/14/2002
• Issued: 12/26/2006
• Est. Priority Date: 06/14/2002
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Vasa, John E.
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): Le, Nhan T.
• Application Number:
  US10/172,239
• Publication Number:
  US 20030232611A1
• Time in Patent Office: 1,656 Days
• Field of Search: 455/324, 455/306, 455/43, 455/131, 455/132, 455/140, 455/141, 455/147, 455/196.1, 455/197.1, 455/2, 455/313, 455/323, 455/334, 455/338, 455/339
• US Class Current: 455/324
• CPC Class Codes: H04B 1/12 Neutralising, balancing, or compensation arrangements
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

A direct conversion receiver including a filtering system for improving signal reception in the receiver is disclosed. In one embodiment, the direct conversion receiver comprises a first filter adapted to receive a plurality of receive signals comprising a receive band. The first filter is configured to attenuate a frequency range of the receive band to de-emphasize signals within of the frequency range. The direct conversion receiver also comprises a second filter coupled to a signal processing logic output and is configured to amplify the signals in the frequency range of the receive band, the signal processing logic being coupled to the output of the first filter and configured to substantially attenuate a plurality of unwanted signals in the receive band.

Claims

1. A direct conversion receiver, comprising:

a first filter adapted to receive a plurality of receive signals of a receive band, the first filter configured to attenuate at least a portion of a desired signal in a frequency range of the receive band to de-emphasize signals within the frequency range; and

a second filter coupled to the output of a signal processing logic and configured to amplify the signals in the frequency range of the receive band, wherein the signal processing logic is coupled to the output of the first filter and is configured to substantially attenuate a plurality of unwanted signals in the receive band, the first and second filters having opposite transfer functions, such that the resulting transfer function is identity, when disregarding the signal processing logic, and the transfer function of the first filter is 1/(1+sRC) and the transfer function of the second fiber is 1+sRC.

2. The direct conversion receiver as defined in claim 1, wherein a pole frequency of the first filter is located at a frequency that is within the desired signal, such that a portion of the desired signal is rejected along with the unwanted signal in order to provide better rejection of the unwanted signal.

3. A direct conversion receiver, comprising:

a first filter adapted to receive a plurality of receive signals comprising a receive band and configured to pass a plurality of low frequency signals substantially unaltered, while providing a constant attenuation value for a plurality of high frequency signals corresponding to at least a portion of a desired signal; and

a second filter coupled to a signal processing logic output and configured to amplify the high frequency signals that were attenuated by the first filter to yield a desired baseband signal, wherein the signal processing logic is coupled to the output of the first filter and configured to attenuate the plurality of receive signals such that substantially only one signal remains, wherein the first filter and second filter, taken together without the signal processing logic, would yield an output with a transfer function of identity, wherein the transfer function of the first filter is (1+sR1C)/(1+s(R1+R2)C), and the transfer function of the second filter is (1+s(R1+R2)C)/(1+sR1C).

4. The direct conversion receiver as defined in claim 3, wherein the pole frequency of the first filter is at a very low frequency and the zero of the first filter corresponds with a flicker noise corner frequency, wherein the response of the first filter is substantially flat after the zero.

5. A method for enhancing reception on a direct conversion receiver, the method comprising the steps of:

attenuating a plurality of signals in a frequency range of a receive band with a filter, including at least a portion of a desired signal, wherein the frequency range of the receive band comprises high frequency signals;

performing intermediate filtering on the receive band;

amplifying the plurality of signals in the frequency range, wherein the attenuating step and the amplifying step, taken together without the intermediate filtering, comprise a balanced circuit without any gain or loss, wherein the attenuating step comprises subtracting strength from the frequency range, such that a low frequency range where a flicker noise is strongest is amplified in relation to a high frequency range where flicker noise is weaker; and

providing a desired baseband signal.

6. The method as defined in claim 5, wherein the attenuating step comprises filtering out a plurality of unwanted signals from the receive band and a portion of the desired signal, while leaving at least a portion of the desired signal substantially unaltered, and the amplifying step comprises adding strength to the plurality of signals in the frequency range.

7. A method for enhancing the reception of a receiver, the method comprising the steps of:

receiving a receive band, the receive band comprising a plurality of signals;

attenuating a frequency range of the plurality of signals with a filter, including at least a portion of a desired signal, such that the frequency range is de-emphasized with respect to signals outside of the frequency range;

providing signal processing to substantially remove a plurality of unwanted signals from the receive band; and

amplifying the frequency range of the plurality of signals, such that the attenuated frequency range receives amplification substantially equal to the attenuation received in the attenuating step, wherein the attenuating step comprises filtering the receive band with a low pass filter having the transfer function (1+sR1C)/(1+s(R1+R2)C), and the amplifying step comprises filtering the intermediate processed and filtered signal with a high pass filter having the transfer function (1+s(R1+R2)C)/(1+sR1C).

8. The method as defined in claim 7, wherein the frequency range comprises frequencies above the corner frequency of a flicker noise.