Simplified High Frequency Tuner and Tuning Method

• US 20100056087A1
• Filed: 11/09/2009
• Published: 03/04/2010
• Est. Priority Date: 09/13/1996
• Status: Active Grant

• Current Assignee: Washington Research Foundation (University of Washington)
• Original Assignee: University of Washington
• Inventors: Suominen, Edwin A.
• Granted Patent: US 7,860,482 B2
• Time in Patent Office: Days
• US Class Current: 455/179.100
• CPC Class Codes: H03D 3/007 by converting the oscillations into two quadrature related signals H03D3/245 takes precedence
• CPC Class Codes: H03D 3/009 Compensating quadrature phase or amplitude imbalances
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: H04B 1/06 Receivers
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/16 Circuits
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178

Abstract

A disclosed method tunes a signal from a channelized spectrum having a predetermined channel spacing. A signal of interest having a predetermined maximum bandwidth is mixed with a local oscillator signal, which has a frequency that is an integer multiple of the channel spacing or one-half of a channel spacing displaced from an integer multiple of the channel spacing. The local oscillator signal is selected to frequency translate the signal of interest to within a near-baseband passband whose lower edge is spaced from DC by at least about the maximum bandwidth of the signal of interest. Problems associated with 1/f noise, DC offsets, and self-mixing products are avoided or substantially diminished. Other methods and systems are also disclosed.

Claims

1-78. -78. (canceled)

79. A method of tuning a signal of interest from a channelized spectrum, comprising:

(a) splitting an incoming signal into two signal paths;

(b) generating an approximately quadrature local oscillator signal;

(c) quadrature mixing the split incoming signal with the local oscillator signal, thereby producing I and Q signals in approximate quadrature relation;

(d) filtering the I signal with a first passband filter and filtering the Q signal with a second passband filter, wherein each filter defines a near-baseband passband, the lower edge of which is spaced from DC by at least about the passband width;

(e) subjecting one of the filtered I and Q signals to a phase shift of about 90 degrees relative to the other, thereby producing second I and Q signals; and

(f) summing the second I and Q signals, thereby producing a real-valued signal.

80. The method of claim 79 wherein the relative phase shift is implemented with a Hilbert transform pair.

81. The method of claim 79 further comprising filtering the real-valued signal with a third passband filter and demodulating the real-valued signal.

82. The method of claim 81 wherein the third bandpass filter is adjustable.

83. The method of claim 79 further comprising implementing error correction between I and Q signals to maximize rejection of unwanted mixing images.

84. The method of claim 83 wherein implementing error correction comprises continuously detecting and correcting errors.

85. The method of claim 79 wherein generating the approximately quadrature local oscillator signal comprises generating the signal from a local oscillator that is coarse-tunable across the channelized spectrum with a step size that is an integer multiple of a channel spacing of the channelized spectrum.

86. The method of claim 85 wherein the local oscillator signal is one-half of a channel spacing displaced from an integer multiple of the channel spacing.

87. The method of claim 79 wherein the lower edge of the near-baseband passband is spaced from DC by at least about a channel spacing of the channelized spectrum.

88. The method of claim 87 wherein the lower edge of the near-baseband passband is spaced from DC by about a channel spacing and the near-baseband passband has a width equal to about the channel spacing.

89. The method of claim 88 further comprising:

(a) filtering the real-valued signal with a third passband filter;

(b) demodulating the filtered real-valued signal; and

(c) implementing error correction between I and Q signals to maximize rejection of unwanted mixing images.

90. The method of claim 79 wherein the lower edge of the near-baseband passband is spaced from DC by at least about the maximum bandwidth of the signal of interest.

91. The method of claim 90 wherein the lower edge of the near-baseband passband is spaced from DC by about the maximum bandwidth of the signal of interest and the near-baseband passband has a width equal to about the maximum bandwidth of the signal of interest.

92. The method of claim 91 further comprising:

(a) filtering the real-valued signal with a third passband filter;

(b) demodulating the filtered real-valued signal; and

(c) implementing error correction between I and Q signals to maximize rejection of unwanted mixing images.

93. The method of claim 79 further comprising converting the filtered I and Q signals to digital I and Q signals, wherein the second I and Q signals and the real-valued signal are digital signals.

94. The method of claim 93 further comprising filtering the real-valued digital signal with a digital passband filter and digitally demodulating the real-valued digital signal.

95. Apparatus for tuning, from a channelized spectrum having a predetermined channel spacing, a channel of interest, the apparatus comprising:

(a) a local oscillator configured to generate a quadrature local oscillator signal;

(b) an amplifier responsive to an RF signal of interest;

(c) a pair of mixers that are responsive to the amplified signal of interest and the quadrature local oscillator signal, thereby producing I and Q signals in approximate quadrature relation;

(d) a first passband filter responsive to the I signal and a second passband filter responsive to the Q signal, wherein each filter defines a near-baseband passband, the lower edge of which is spaced from DC by at least about the passband width; and

(f) a summer responsive to (1) a first one of the filtered I and Q signals from the first and second passband filters, and (2) a version of the second one of the filtered I and Q signals that has been subjected to a phase shift of about 90 degrees relative to the first one of the filtered I and Q signals.

96. The apparatus of claim 95 further comprising a Hilbert transform pair responsive to the filtered I and Q signals, thereby subjecting one of the filtered I and Q signals to a phase shift of about 90 degrees relative to the other.

97. The apparatus of claim 95 further comprising a third passband filter responsive to a real-valued signal from the summer and a demodulator responsive to a filtered real-valued signal from the third passband filter.

98. The apparatus of claim 97 wherein the third bandpass filter is adjustable.

99. The apparatus of claim 95 wherein the local oscillator is coarse-tunable across the channelized spectrum with a step size that is an integer multiple of a channel spacing of the channelized spectrum.

100. The apparatus of claim 99 wherein the local oscillator is configured to generate the quadrature local oscillator signal at frequencies one-half of a channel spacing displaced from integer multiples of the channel spacing.

101. The apparatus of claim 95 wherein the lower edge of the near-baseband passband is spaced from DC by at least about a channel spacing of the channelized spectrum.

102. The apparatus of claim 101 wherein the lower edge of the near-baseband passband is spaced from DC by about a channel spacing and the near-baseband passband has a width equal to about the channel spacing.

103. The apparatus of claim 95 wherein the lower edge of the near-baseband passband is spaced from DC by at least about the maximum bandwidth of the signal of interest.

104. The apparatus of claim 103 wherein the lower edge of the near-baseband passband is spaced from DC by about the maximum bandwidth of the signal of interest and the near-baseband passband has a width equal to about the maximum bandwidth of the signal of interest.

105. The apparatus of claim 95 further comprising a pair of analog-to-digital converters response to the filtered I and Q signals from the first and second passband filters, respectively, wherein the summer is responsive to digital signals.

106. The apparatus of claim 105 further comprising a digital passband filter responsive to a real-valued digital signal from the summer and a digital demodulator responsive to a filtered real-valued digital signal from the digital passband filter.

107. A method of tuning a channel of interest from a channelized spectrum, comprising:

(a) splitting an incoming signal containing a channel of interest into two signal paths;

(b) generating an approximately quadrature local oscillator signal;

(c) quadrature mixing the split incoming signal with the local oscillator signal, thereby producing I and Q signals in approximate quadrature relation;

(d) filtering the I signal with a first filter and filtering the Q signal with a second filter;

(e) subjecting one of the filtered I and Q signals to a phase shift of about 90 degrees relative to the other, thereby producing second I and Q signals; and

(f) summing the second I and Q signals, thereby producing a real-valued signal;

(g) wherein the channel of interest is frequency translated to within a near-baseband passband, the lower edge of which is spaced from DC by at least about the channel spacing.

108. The method of claim 107 wherein the relative phase shift is implemented with a Hilbert transform pair.

109. The method of claim 107 further comprising implementing error correction between I and Q signals to maximize rejection of unwanted mixing images.

110. The method of claim 109 wherein implementing error correction comprises continuously detecting and correcting errors.

111. The method of claim 107 wherein generating the approximately quadrature local oscillator signal comprises generating the signal from a local oscillator that is coarse-tunable across the channelized spectrum with a step size that is an integer multiple of a channel spacing of the channelized spectrum.

112. The method of claim 111 wherein the local oscillator signal is one-half of a channel spacing displaced from an integer multiple of the channel spacing.

113. The method of claim 111 wherein the lower edge of the near-baseband passband is spaced from DC by about a channel spacing and the near-baseband passband has a width equal to about the channel spacing.

114. The method of claim 113 further comprising:

(a) demodulating the real-valued signal; and

(b) implementing error correction between I and Q signals to maximize rejection of unwanted mixing images.

115. The method of claim 107 wherein the lower edge of the near-baseband passband is spaced from DC by at least about the maximum bandwidth of the signal of interest.

116. The method of claim 115 wherein the near-baseband passband has a width equal to about the maximum bandwidth of the signal of interest.

117. The method of claim 116 further comprising:

(a) demodulating the real-valued signal; and

(b) implementing error correction between I and Q signals to maximize rejection of unwanted mixing images.

118. The method of claim 107 further comprising converting the I and Q signals to digital I and Q signals, wherein the second I and Q signals and the real-valued signal are digital signals.

119. The method of claim 118 further comprising filtering the real-valued digital signal with a digital passband filter and digitally demodulating the real-valued digital signal.

120-166. -166. (canceled)