Receiver system

• US 7,308,241 B2
• Filed: 07/19/2006
• Issued: 12/11/2007
• Est. Priority Date: 10/24/2001
• Status: Expired due to Fees

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Ashida, Hiroyuki, Shimada, Yoshikazu
• Primary Examiner(s): Vuong; Quochien B.
• Application Number:
  US11/488,768
• Publication Number:
  US 20060258321A1
• Time in Patent Office: 510 Days
• Field of Search: 455/63.1, 455/67.13, 455/295, 455/296, 455/307, 455/313, 455/334, 455/339, 333/167, 333/185, 375/346, 375/350, 327/552, 327/553, 327/557, 327/558
• US Class Current: 455/307
• CPC Class Codes: H03H 11/0444 Simulation of ladder networks
• CPC Class Codes: H03H 11/486 Simulating inductances using transconductance amplifiers
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04B 1/12 Neutralising, balancing, or compensation arrangements

Abstract

A conventional receiver system has a filter circuit with unsatisfactory gain characteristics, and thus does not offer satisfactory reception performance. A receiver system of the invention has a filter circuit employing an equivalent inductor circuit including a capacitor, a gyrator composed of a plurality of operational transconductance amplifiers and having the capacitor as a load, and a resistor connected in series with the capacitor. A conventional receiver system has a band-pass filter circuit with a low third-order input intercept point, and thus does not offer satisfactory reception performance. The receiver system of the invention has, in the stage following a mixer, a band-pass filter circuit composed of a low-pass filter and a band-pass filter receiving the output signal of the low-pass filter, wherein the value obtained by dividing the higher cutoff frequency of the band-pass filter by the lower cutoff frequency thereof is smaller than 2, the center frequency of the band-pass filter is within a range of from about 1 to 3 MHz, and the cutoff frequency of the low-pass filter is higher than the center frequency of the band-pass filter.

Claims

1. A receiver system comprising:

an antenna for receiving a high-frequency signal;

an amplifier for amplifying the high-frequency signal output from said antenna;

a local oscillator for producing a local oscillation signal;

a mixer for mixing an output signal of said amplifier and the local oscillation signal to produce an intermediate signal; and

a band-pass filter circuit for eliminating unnecessary frequency components from an output signal of said mixer,

wherein said band-pass filter circuit is composed of a low-pass filter that receives the output signal of said mixer and a band-pass filter that receives an output signal of said low-pass filter,

a value obtained by diving a higher cutoff frequency of said band-pass filter by a lower cutoff frequency thereof is smaller than 2, and a cutoff frequency of said low-pass filter is higher than a center frequency of said band-pass filter.

2. A receiver system as claimed in claim 1, wherein the center frequency of said band-pass filter is within a range of from about 1-3 MHz.